阅读说明：本技术 重建器械术野中心的控制方法、系统、设备和存储介质 (Control method, system, equipment and storage medium for reconstructing instrument surgical field center ) 是由 黄善灯 柏龙 陈晓红 潘鲁锋 于 2021-06-11 设计创作，主要内容包括：本申请涉及一种重建器械术野中心的控制方法、系统、设备和可读存储介质,获取重建器械术野中心后,动平台在机械坐标系下的当前位姿,根据动平台的当前位姿获取重建器械术野中心后,静平台在机械坐标系下的目标位姿,根据动平台的当前位姿和静平台的目标位姿对静平台进行位姿变换；根据动平台的当前位姿和静平台的目标位姿获取动平台和静平台之间在中心轴线上的扭转角度,根据扭转角度对动平台进行旋转变换,以使并联平台回归零位,解决了相关技术中存在的并联机器人难以实现姿态回零的问题,提升了重建器械术野中心的控制准确度,保证并联平台的运动性能。(The application relates to a control method, a system, equipment and a readable storage medium for a surgical field center of a reconstruction instrument, wherein after the surgical field center of the reconstruction instrument is obtained, the current pose of a movable platform under a mechanical coordinate system is obtained, after the surgical field center of the reconstruction instrument is obtained according to the current pose of the movable platform, the target pose of a static platform under the mechanical coordinate system is obtained, and the pose of the static platform is transformed according to the current pose of the movable platform and the target pose of the static platform; the torsion angle between the movable platform and the static platform on the central axis is obtained according to the current pose of the movable platform and the target pose of the static platform, and the movable platform is subjected to rotation transformation according to the torsion angle, so that the parallel platform returns to a zero position, the problem that the parallel robot in the related technology is difficult to realize posture zero return is solved, the control accuracy of the surgical field center of the reconstruction instrument is improved, and the motion performance of the parallel platform is ensured.)

1. A control method for reconstructing a surgical field center of an instrument is characterized by comprising the following steps:

after a surgical field center of a reconstruction instrument is obtained, the current pose of a movable platform under a mechanical coordinate system is obtained, wherein the mechanical coordinate system is a global coordinate system of a mechanical arm where the movable platform is located;

after the surgical field center of the reconstruction instrument is obtained according to the current pose of the movable platform, the target pose of a static platform under the mechanical coordinate system is obtained, wherein the movable platform and the static platform are parallel platforms which are connected in the mechanical arm through telescopic elements, the center of the target pose of the static platform is on the central axis of the current pose of the movable platform, and the static platform in the target pose is parallel to the movable platform;

carrying out pose transformation on the static platform according to the current pose of the movable platform and the target pose of the static platform;

and acquiring a torsion angle between the movable platform and the static platform on the central axis according to the current pose of the movable platform and the target pose of the static platform, and performing rotation transformation on the movable platform according to the torsion angle so as to enable the parallel platform to return to a zero position.

2. The control method for reconstructing instrument surgical field center according to claim 1, wherein the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

acquiring a first conversion matrix between the static coordinate system and the dynamic coordinate system when the zero position state is reestablished and returned according to the current pose of the dynamic platform and the target pose of the static platform; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located;

obtaining a second conversion matrix from the static coordinate system to the moving coordinate system when the zero state is rebuilt but not returned; and a third transformation matrix between the mechanical coordinate system and the static coordinate system before reconstruction;

acquiring a fourth conversion matrix between the mechanical coordinate system and the static coordinate system after reconstruction according to the first conversion matrix, the second conversion matrix and the third conversion matrix;

and acquiring a fifth conversion matrix between joint coordinate systems of a passive arm in the mechanical arm according to the fourth conversion matrix, and converting the driving parameters of the joint of the passive arm according to the fifth conversion matrix, wherein the passive arm is connected with the static platform.

3. The control method for reconstructing the surgical field center of an instrument as claimed in claim 2, wherein the passive arm comprises a first joint, a second joint and a third joint connected in series, wherein the driving parameters of the first joint and the third joint are unchanged, and the third joint is connected with the static platform;

the transforming the driving parameters of the joints of the driven arm according to the fifth transformation matrix comprises the following steps:

acquiring a sixth conversion matrix from the mechanical coordinate system to the coordinate system of the first joint and a seventh conversion matrix from the coordinate system of the second joint to the coordinate system of the third joint;

acquiring an eighth conversion matrix from the first joint to the second joint according to the fifth conversion matrix, the sixth conversion matrix and the seventh conversion matrix;

and transforming the driving parameters of the second joint according to the eighth transformation matrix.

4. The method for controlling the surgical field center of the reconstruction instrument as claimed in claim 3, wherein the second joint comprises a first revolute pair, a second revolute pair and a third revolute pair which are connected in sequence, the first revolute pair is rotationally connected with the first joint, and the third revolute pair is rotationally connected with the third joint;

the transforming the driving parameters of the second joint according to an eighth transformation matrix comprises the steps of:

and obtaining a driving parameter transformation relation from the first joint to the third revolute pair, and solving to obtain driving parameters of the first revolute pair, the second revolute pair and the third revolute pair according to the eighth transformation matrix and the driving parameter transformation relation.

5. The control method for reconstructing instrument surgical field center according to claim 1, wherein the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

and acquiring a first telescopic amount of the telescopic element according to the current pose of the movable platform and the target pose of the static platform, and adjusting the telescopic element according to the first telescopic amount when the pose of the static platform is changed, so that the current pose of the movable platform in the mechanical coordinate system is kept unchanged.

6. The control method for reconstructing instrument surgical field center according to any one of claims 1 to 5, wherein the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

acquiring an original pose of the static platform before reconstruction, interpolating the original pose and a target pose of the static platform, and acquiring an intermediate pose of the static platform in a pose transformation process;

and performing position transformation and posture transformation on the static platform according to the intermediate posture and the current posture of the movable platform, wherein the position transformation comprises circular arc motion transformation taking a telecentric motionless point as a circle center and linear motion transformation pointing to the circle center, and the posture transformation comprises rotation transformation of a static coordinate system around a Z axis of the mechanical coordinate system and rotation transformation of the static coordinate system around a Y axis of the static coordinate system.

7. The control method for reconstructing instrument surgical field center according to claim 6, wherein the position transformation and the posture transformation of the static platform according to the intermediate posture and the current posture of the movable platform comprises the following steps:

converting the intermediate pose into a ninth conversion matrix between a static coordinate system and the mechanical coordinate system and a tenth conversion matrix between the static coordinate system and the dynamic coordinate system; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located;

transforming attitude parameters of joints of a driven arm according to the ninth transformation matrix and the tenth transformation matrix, wherein the driven arm is connected with the static platform;

and acquiring a second stretching amount of the stretching element according to the ninth conversion matrix and the tenth conversion matrix, and adjusting the stretching element according to the second stretching amount so as to keep the current pose of the movable platform under the mechanical coordinate system unchanged.

8. The control method for reconstructing instrument surgical field center according to claim 7, wherein the rotating transformation of the movable platform according to the torsion angle to make the parallel platform return to the zero position comprises the following steps:

interpolating the torsion angle to obtain a middle angle of the movable platform in the rotation transformation process;

and carrying out rotation transformation on the movable platform according to the intermediate angle and the current angle of the movable platform.

9. The method for controlling the field center of the reconstruction instrument as set forth in claim 8, wherein the rotationally transforming the movable platform according to the intermediate angle and the current angle of the movable platform comprises the steps of:

and acquiring an eleventh conversion matrix between the static coordinate system and the moving coordinate system according to the intermediate angle, acquiring a third expansion amount of the telescopic element according to the eleventh conversion matrix, and adjusting the telescopic element according to the third expansion amount so as to enable the parallel platform to return to a zero position.

10. The control method for reconstructing the surgical field center of an instrument as claimed in claim 9, further comprising the steps of:

and after the parallel platform returns to the zero position, acquiring the coordinates of the telecentric motionless point under the static coordinate system after the operative field is reconstructed according to the conversion relation between the static coordinate system and the mechanical coordinate system after the operative field is reconstructed, wherein the coordinates of the telecentric motionless point under the mechanical coordinate system are unchanged.

11. A control system for reconstructing a surgical field center of an instrument, the system comprising:

the device comprises a first acquisition module, a second acquisition module and a third acquisition module, wherein the first acquisition module is used for acquiring the current pose of a movable platform under a mechanical coordinate system after the surgical field center of the reconstruction instrument is reconstructed, and the mechanical coordinate system is a global coordinate system of a mechanical arm where the movable platform is located;

the second acquisition module is used for acquiring the target pose of a static platform under the mechanical coordinate system after the surgical field center of the reconstruction instrument is acquired according to the current pose of the movable platform, wherein the movable platform and the static platform are parallel platforms which are connected in the mechanical arm through telescopic elements, the center of the target pose of the static platform is on the central axis of the current pose of the movable platform, and the static platform in the target pose is parallel to the movable platform;

the first transformation module is used for carrying out pose transformation on the static platform according to the current pose of the movable platform and the target pose of the static platform;

and the second transformation module is used for acquiring a torsion angle between the movable platform and the static platform on the central axis according to the current pose of the movable platform and the target pose of the static platform, and performing rotation transformation on the movable platform according to the torsion angle so as to enable the parallel platform to return to a zero position.

12. A control device for reconstructing the surgical field center of an instrument is characterized by comprising a mechanical arm and a control device;

the control device is used for carrying out pose transformation on the static platform on the mechanical arm and carrying out rotation transformation on the movable platform on the mechanical arm according to the control method for reconstructing the surgical field center of the instrument as claimed in any one of claims 1 to 10.

13. A readable storage medium, on which an executable program is stored, characterized in that the executable program, when being executed by a processor, implements the steps of the method for controlling the reconstruction of an instrument surgical field center according to any one of claims 1 to 10.

Technical Field

The present application relates to the field of robotics, and in particular, to a method, system, device, and storage medium for controlling a surgical field center of a reconstruction instrument.

Background

The robot needs to be placed before application operation, so that the tail end of an instrument reaches a corresponding operation space.

When the instrument is moved to another distant position, if the instrument is moved to the target point directly by the active arm, the parallel platform may be already at the edge position of the working space, and therefore, the parallel platform needs to be adjusted to the zero position state without changing the position of the instrument.

The motion range of the active arm of the parallel robot is small, and after the positioning is finished, the parallel platform is usually not in a zero position, which may cause that the parallel platform cannot cover the applied operation space in the motion space, so that the parallel platform is clamped in the limit position and cannot finish the operation. Due to the limited freedom of movement of the passive arm, the attitude return to zero cannot be completely realized only by the movement of the passive arm.

At present, an effective solution is not provided aiming at the problem that the parallel robot in the related technology is difficult to realize the posture zero returning.

Disclosure of Invention

The embodiment of the application provides a control method, a system, equipment and a readable storage medium for reconstructing an instrument surgical field center, which at least solve the problem that a parallel robot in the related art is difficult to realize posture zeroing.

In a first aspect, an embodiment of the present application provides a control method for reconstructing a surgical field center of an instrument, including:

after the surgical field center of the reconstruction instrument is obtained, the current pose of the movable platform under a mechanical coordinate system is obtained, wherein the mechanical coordinate system is a global coordinate system of a mechanical arm where the movable platform is located;

after the surgical field center of the reconstruction instrument is obtained according to the current pose of the movable platform, the target pose of the static platform under a mechanical coordinate system is obtained, wherein the movable platform and the static platform are parallel platforms which are connected in the mechanical arm through telescopic elements, the center of the target pose of the static platform is on the central axis of the current pose of the movable platform, and the static platform in the target pose is parallel to the movable platform;

carrying out pose transformation on the static platform according to the current pose of the movable platform and the target pose of the static platform;

and acquiring a torsion angle between the movable platform and the static platform on the central axis according to the current pose of the movable platform and the target pose of the static platform, and performing rotation transformation on the movable platform according to the torsion angle so as to enable the parallel platform to return to a zero position.

In some embodiments, the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

acquiring a first conversion matrix between the static coordinate system and the dynamic coordinate system when the zero position state is reconstructed and returned according to the current pose of the dynamic platform and the target pose of the static platform; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located;

acquiring a second conversion matrix from the static coordinate system to the dynamic coordinate system when the zero state is rebuilt but not returned; and reconstructing a third transformation matrix from the mechanical coordinate system to the static coordinate system before reconstruction;

acquiring a fourth conversion matrix from the reconstructed mechanical coordinate system to the static coordinate system according to the first conversion matrix, the second conversion matrix and the third conversion matrix;

and acquiring a fifth conversion matrix between joint coordinate systems of a passive arm in the mechanical arm according to the fourth conversion matrix, and converting the attitude parameters of the joint of the passive arm according to the fifth conversion matrix, wherein the passive arm is connected with the static platform.

In some embodiments, the passive arm comprises a first joint, a second joint and a third joint which are connected in series, wherein the posture parameters of the first joint and the third joint are unchanged, and the third joint is connected with the static platform;

the posture parameter transformation of the joint of the passive arm according to the fifth transformation matrix comprises the following steps:

acquiring a sixth conversion matrix from the mechanical coordinate system to the coordinate system of the first joint and a seventh conversion matrix from the coordinate system of the second joint to the coordinate system of the third joint;

acquiring an eighth conversion matrix from the first joint to the second joint according to the fifth conversion matrix, the sixth conversion matrix and the seventh conversion matrix;

and transforming the attitude parameters of the second joint according to the eighth transformation matrix.

In some embodiments, the second joint comprises a first revolute pair, a second revolute pair and a third revolute pair which are connected in sequence, wherein the first revolute pair is rotationally connected with the first joint, and the third revolute pair is rotationally connected with the third joint;

the transforming the driving parameters of the second joint according to an eighth transformation matrix comprises the steps of:

and obtaining a driving parameter transformation relation from the first joint to the third revolute pair, and solving to obtain driving parameters of the first revolute pair, the second revolute pair and the third revolute pair according to the eighth transformation matrix and the driving parameter transformation relation.

In some embodiments, the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

and when the pose of the static platform is changed, the telescopic elements are adjusted according to the first telescopic amount, so that the current pose of the dynamic platform in a mechanical coordinate system is kept unchanged.

In some embodiments, the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

acquiring an original pose of the static platform before reconstruction, interpolating the original pose and the target pose of the static platform, and acquiring an intermediate pose of the static platform in a pose transformation process;

and performing position transformation and posture transformation on the static platform according to the intermediate posture and the current posture of the movable platform, wherein the position transformation comprises circular arc motion transformation taking a telecentric motionless point as a circle center and linear motion transformation pointing to the circle center, and the posture transformation comprises rotation transformation of a static coordinate system around a Z axis of a mechanical coordinate system and rotation transformation of the static coordinate system around a Y axis of the static coordinate system.

In some embodiments, the position transformation and the posture transformation of the static platform according to the intermediate pose and the current pose of the movable platform comprise the following steps:

converting the intermediate pose into a ninth conversion matrix between a static coordinate system and a mechanical coordinate system and a tenth conversion matrix between the static coordinate system and a dynamic coordinate system; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located;

changing the attitude parameters of the joints of the driven arm according to the ninth conversion matrix and the tenth conversion matrix, wherein the driven arm is connected with the static platform;

and acquiring a second telescopic quantity of the telescopic element according to the ninth conversion matrix and the tenth conversion matrix, and adjusting the telescopic element according to the second telescopic quantity so as to keep the current pose of the movable platform under the mechanical coordinate system unchanged.

In some embodiments, the rotating the moving platform according to the torsion angle to make the parallel platform return to the zero position includes the following steps:

interpolating the torsion angle to obtain a middle angle of the movable platform in the rotation transformation process;

and carrying out rotation transformation on the movable platform according to the intermediate angle and the current angle of the movable platform.

In some of these embodiments, the rotational transformation of the moving platform according to the intermediate angle and the current angle of the moving platform comprises the following steps:

and acquiring an eleventh conversion matrix between the static coordinate system and the moving coordinate system according to the middle angle, acquiring a third expansion amount of the telescopic element according to the eleventh conversion matrix, and adjusting the telescopic element according to the third expansion amount so as to enable the parallel platform to return to the zero position.

In some embodiments, the control method for reconstructing the surgical field center of the instrument further comprises the following steps: and after the parallel platform returns to the zero position, acquiring the coordinates of the telecentric motionless point under the static coordinate system after the operative field is reconstructed according to the conversion relation between the static coordinate system and the mechanical coordinate system after the operative field is reconstructed, wherein the coordinates of the telecentric motionless point under the mechanical coordinate system are unchanged.

In a second aspect, an embodiment of the present application provides a control system for reconstructing a surgical field center of an instrument, including:

the first acquisition module is used for acquiring the current pose of the movable platform under a mechanical coordinate system after the surgical field center of the reconstruction instrument is acquired, wherein the mechanical coordinate system is a global coordinate system of a mechanical arm where the movable platform is located;

the second acquisition module is used for acquiring the target pose of the static platform under a mechanical coordinate system after the surgical field center of the reconstruction instrument is acquired according to the current pose of the movable platform, wherein the movable platform and the static platform are parallel platforms which are connected in the mechanical arm through telescopic elements, the center of the target pose of the static platform is on the central axis of the current pose of the movable platform, and the static platform in the target pose is parallel to the movable platform;

the first transformation module is used for carrying out pose transformation on the static platform according to the current pose of the movable platform and the target pose of the static platform;

and the second transformation module is used for acquiring a torsion angle between the movable platform and the static platform on the central axis according to the current pose of the movable platform and the target pose of the static platform, and performing rotation transformation on the movable platform according to the torsion angle so as to enable the parallel platform to return to a zero position.

In a third aspect, an embodiment of the present application provides a control apparatus for reconstructing a surgical field center of an instrument, including a mechanical arm and a control device;

the control device is used for carrying out pose transformation on the static platform on the mechanical arm and carrying out rotation transformation on the movable platform on the mechanical arm according to the control method for reconstructing the surgical field center of the instrument in the first aspect.

In a fourth aspect, embodiments of the present application provide a readable storage medium, on which an executable program is stored, and the executable program, when executed by a processor, implements the method for controlling the reconstruction instrument surgical field center according to the first aspect.

Compared with the prior art, the control method, the control system, the control equipment and the readable storage medium for the surgical field center of the reconstruction instrument provided by the embodiment of the application have the advantages that after the surgical field center of the reconstruction instrument is obtained, the current pose of the movable platform is under the mechanical coordinate system, after the surgical field center of the reconstruction instrument is obtained according to the current pose of the movable platform, the target pose of the static platform is under the mechanical coordinate system, and pose transformation is carried out on the static platform according to the current pose of the movable platform and the target pose of the static platform; the torsion angle between the movable platform and the static platform on the central axis is obtained according to the current pose of the movable platform and the target pose of the static platform, and the movable platform is subjected to rotation transformation according to the torsion angle, so that the parallel platform returns to a zero position, the problem that the parallel robot in the related technology is difficult to realize posture zero return is solved, the control accuracy of the surgical field center of the reconstruction instrument is improved, and the motion performance of the parallel platform is ensured.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic flow chart of a control method for reconstructing a surgical field center of an instrument according to an embodiment of the present application;

FIG. 2 is a schematic diagram of an application of a control method for reconstructing a surgical field center of an instrument according to an embodiment of the present application;

FIG. 3 is a schematic view of a joint of a robotic arm according to an embodiment of the present application;

FIG. 4 is a schematic diagram of pose transformation of a static platform in a parallel platform according to an embodiment of the application;

FIG. 5 is a schematic diagram of attitude transformation of a stationary platform in a parallel platform according to an embodiment of the present application;

FIG. 6 is a schematic diagram of a system default initial position of a parallel platform according to an embodiment of the present application;

FIG. 7 is a block diagram of a control system for reconstructing a surgical field center of an instrument according to an embodiment of the present application;

fig. 8 is a block diagram of a control apparatus for reconstructing a surgical field center of an instrument according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments provided in the present application without any creative effort belong to the protection scope of the present application.

Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of ordinary skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments without conflict.

Unless defined otherwise, technical or scientific terms referred to herein shall have the ordinary meaning as understood by those of ordinary skill in the art to which this application belongs. Reference to "a," "an," "the," and similar words throughout this application are not to be construed as limiting in number, and may refer to the singular or the plural. The present application is directed to the use of the terms "including," "comprising," "having," and any variations thereof, which are intended to cover non-exclusive inclusions; for example, a process, method, system, article, or apparatus that comprises a list of steps or modules (elements) is not limited to the listed steps or elements, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. Reference to "connected," "coupled," and the like in this application is not intended to be limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The term "plurality" as referred to herein means two or more. "and/or" describes an association relationship of associated objects, meaning that three relationships may exist, for example, "A and/or B" may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. Reference herein to the terms "first," "second," "third," and the like, are merely to distinguish similar objects and do not denote a particular ordering for the objects.

The embodiment provides a control method for reconstructing a surgical field center of an instrument. Fig. 1 is a schematic flowchart of a control method for reconstructing a surgical field center of an instrument according to an embodiment of the present application, and as shown in fig. 1, the flowchart includes the following steps:

step S110: after the surgical field center of the reconstruction instrument is obtained, the current pose of the movable platform under a mechanical coordinate system is obtained, wherein the mechanical coordinate system is a global coordinate system of a mechanical arm where the movable platform is located;

in the step, the instrument surgical field center refers to the position of the instrument in the surgical field center, and the reconstruction instrument surgical field center refers to a non-target region of the surgical field center at the tail end of the mechanical arm of the parallel robot, and needs to be re-determined under the condition of not changing the telecentric fixed point of the parallel robot so that the surgical field center is in the target region; in the process of reconstructing the surgical field center of the instrument, the transfer of the surgical field center is generally realized by the movement of the movable platform on the parallel platform of the parallel robot, but the movable platform and the static platform on the parallel platform are not in the zero position at the moment; the global coordinate system where the mechanical arm is located is a mechanical coordinate system suitable for each part of the mechanical arm, and the poses of the movable platform and the static platform are mapped onto the mechanical coordinate system, so that the pose conversion calculation between the movable platform and the static platform is facilitated.

Specifically, the machine coordinate system may be a global coordinate system of the entire robot arm in fig. 3, and an origin of the global coordinate system may be a base center of the robot arm.

Step S120: after the surgical field center of the reconstruction instrument is obtained according to the current pose of the movable platform, the target pose of the static platform under a mechanical coordinate system is obtained, wherein the movable platform and the static platform are parallel platforms which are connected in the mechanical arm through telescopic elements, the center of the target pose of the static platform is on the central axis of the current pose of the movable platform, and the static platform in the target pose is parallel to the movable platform;

in the step, the parallel platform is an important component of the mechanical arm and comprises a movable platform, a telescopic element and a static platform, the relative poses of the static platform and the movable platform in zero positions are determined, the center of the target pose of the static platform is on the central axis of the current pose of the movable platform, the static platform in the target pose is parallel to the movable platform, and the target pose of the static platform in a mechanical coordinate system can be determined by utilizing the current pose of the movable platform behind the surgical field center of the reconstruction instrument.

Step S130: carrying out pose transformation on the static platform according to the current pose of the movable platform and the target pose of the static platform;

in the step, the current pose of the movable platform and the target pose of the static platform are used as transformation targets, pose transformation is carried out on the static platform, the static platform is enabled to move to the target pose, and in the process, the current pose of the movable platform under a mechanical coordinate system is kept unchanged.

Step 140: acquiring a torsion angle between the movable platform and the static platform on the central axis according to the current pose of the movable platform and the target pose of the static platform, and performing rotation transformation on the movable platform according to the torsion angle so as to enable the parallel platform to return to a zero position;

in the step, after the static platform is subjected to pose transformation, the parallel platform cannot completely return to the zero position, torsion in the direction of a central shaft of the movable platform can exist between the movable platform and the static platform, and the parallel platform cannot return to the zero position by adjusting the posture of the static platform due to the limitation of the degree of freedom of a driven arm on the mechanical arm, so that the parallel platform is selectively controlled to rotate around the central shaft to return to the zero position, the rotation of the movable platform can cause the instrument to rotate around the central shaft, the telecentric dead point principle cannot be violated, the surgical field center of the instrument cannot be changed, and the surgical field center reconstruction can be effectively completed.

In this embodiment, through the above steps, after the surgical field center of the reconstruction instrument is obtained, the current pose of the movable platform under the mechanical coordinate system is obtained, after the surgical field center of the reconstruction instrument is obtained according to the current pose of the movable platform, the target pose of the static platform under the mechanical coordinate system is obtained, and the pose of the static platform is transformed according to the current pose of the movable platform and the target pose of the static platform; the torsion angle between the movable platform and the static platform on the central axis is obtained according to the current pose of the movable platform and the target pose of the static platform, and the movable platform is subjected to rotation transformation according to the torsion angle, so that the parallel platform returns to a zero position, the problem that the parallel robot in the related technology is difficult to realize posture zero return is solved, the control accuracy of the surgical field center of the reconstruction instrument is improved, and the motion performance of the parallel platform is ensured.

It should be noted that the control method of the surgical field center of the reconstruction instrument can be applied to various application scenarios. As shown in fig. 2, in the preposition operation, the preposition assistant establishes a telecentric motionless point by moving each joint of the passive arm, and establishes the center of the surgical field of the instrument so that the initial position of the distal end point of the instrument is positioned at the center of the surgical field. Since the procedural instrument is not inserted into the examination object, but is approximately determined by visual inspection by the anterior assistant, there may be a large deviation from the ideal instrument surgical field center. When the instrument is inserted into an object to be detected and a large deviation is found, the instrument surgical field center can be reconstructed under the condition of not changing the telecentric fixed point by the scheme of the application so as to eliminate the deviation and ensure that the instrument obtains an ideal moving space.

As another example, the parallel platform working space is relatively small due to the swing angle limitation of the telescopic elements (such as dynamic and static hinges), and a larger moving space may be required in some scenarios. When the current working space of the parallel platform can not meet the requirement or the current working space is subjected to periodic operation, the instrument surgical field center can be reconstructed by the scheme of the application, the working space of the parallel platform is moved under the condition of not changing the telecentric fixed point, and a larger moving space is indirectly obtained.

In some embodiments, the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

acquiring a first conversion matrix between the static coordinate system and the dynamic coordinate system when the zero position state is reconstructed and returned according to the current pose of the dynamic platform and the target pose of the static platform; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located;

acquiring a second conversion matrix from the static coordinate system to the dynamic coordinate system when the zero state is rebuilt but not returned; and reconstructing a third transformation matrix from the mechanical coordinate system to the static coordinate system before reconstruction;

acquiring a fourth conversion matrix from the reconstructed mechanical coordinate system to the static coordinate system according to the first conversion matrix, the second conversion matrix and the third conversion matrix;

and acquiring a fifth conversion matrix between joint coordinate systems of a passive arm in the mechanical arm according to the fourth conversion matrix, and converting the attitude parameters of the joint of the passive arm according to the fifth conversion matrix, wherein the passive arm is connected with the static platform.

In this embodiment, before and after reconstructing the surgical field center of the instrument, there is a transformation relationship among the dynamic coordinate system, the static coordinate system, and the mechanical coordinate system, which can be described by a transformation matrix. Four transformation matrices are used here: when the zero state is rebuilt and returned, a first conversion matrix between the static coordinate system and the moving coordinate system is obtained; a second conversion matrix from the static coordinate system to the moving coordinate system when the zero state is reconstructed but not returned; reconstructing a third conversion matrix from the mechanical coordinate system to the static coordinate system before reconstruction; and a fourth conversion matrix from the reconstructed mechanical coordinate system to the static coordinate system. The first transformation matrix can be obtained according to the current pose of the movable platform and the target pose of the static platform, the second transformation matrix can be obtained according to the transformation relation between the movable platform and the static platform, the third transformation matrix can be obtained according to the joint information of the driven arm of the mechanical arm, because the pose of the movable platform is kept unchanged in the transformation process, the product of the fourth transformation matrix and the first transformation matrix is the same as the product of the third transformation matrix and the second transformation matrix, and the fourth transformation matrix can be obtained by utilizing the equivalent relation, which reflects the conversion relationship from the passive arm to the parallel platform in the mechanical arm, so as to obtain a fifth conversion matrix between the joint coordinate systems of the passive arm in the mechanical arm, and the posture parameters of the joints of the driven arm are transformed by a fifth transformation matrix, and the posture transformation of the static platform in the parallel platform is realized through the posture transformation of the driven arm.

It should be noted that, as shown in fig. 2, the stationary coordinate system is the coordinate system where the stationary platform is located, before the reconstruction of the surgical field, the center S of the stationary platform is taken as the origin, the Xs axis and the Ys axis are parallel to the stationary platform plane, and the Zs axis is perpendicular to the stationary platform plane; after the operative field is reconstructed, taking the center S 'of the static platform as an origin, enabling the X' S axis and the Y 'S axis to be parallel to the plane of the static platform, and enabling the Z' S axis to be vertical to the plane of the static platform; the movable coordinate system is the coordinate system of the movable platform, and before the reconstruction of the surgical field, the center M of the movable platform is taken as the origin, and X is taken as the origin_MAxis and Y_MThe axis being parallel to the plane of the moving platform, Z_MThe axis is vertical to the plane of the movable platform; after the operative field is reconstructed, the center M 'of the movable platform is taken as the origin, X'_MShaft and Y'_MThe axis being parallel to the plane of the moving platform, Z'_MThe axis is perpendicular to the plane of the moving platform.

In some embodiments, the passive arm comprises a first joint, a second joint and a third joint which are connected in series, wherein the posture parameters of the first joint and the third joint are unchanged, and the third joint is connected with the static platform;

the posture parameter transformation of the joint of the passive arm according to the fifth transformation matrix comprises the following steps:

acquiring a sixth conversion matrix from the mechanical coordinate system to the coordinate system of the first joint and a seventh conversion matrix from the coordinate system of the second joint to the coordinate system of the third joint;

acquiring an eighth conversion matrix from the first joint to the second joint according to the fifth conversion matrix, the sixth conversion matrix and the seventh conversion matrix;

and transforming the attitude parameters of the second joint according to the eighth transformation matrix.

In this embodiment, the passive arm includes a plurality of joints connected in series, when the posture parameters of the joints of the passive arm are transformed, the posture parameters of some of the joints are not changed, only the posture parameters of another part of the joints are changed, since the posture parameters of the first joint and the third joint are not changed, the sixth transformation matrix from the mechanical coordinate system to the coordinate system of the first joint and the seventh transformation matrix from the coordinate system of the second joint to the coordinate system of the third joint are determined, the eighth transformation matrix for the posture parameters of the second joint can be obtained by combining the fifth transformation matrix of the transformation target, and the posture parameters of the second joint are transformed based on the eighth transformation matrix, so that the number of the moving joints can be reduced, the calculation amount of the posture parameters of the joints can be reduced, and the adjustment of the passive arm can be realized as soon as possible.

Furthermore, the first joint, the second joint and the third joint can comprise one or more joints, and the third joint is connected with the static platform, so that when the operation is finished and the parallel platform is withdrawn, the full motion range of the third joint is ensured.

In some embodiments, the second joint comprises a first revolute pair, a second revolute pair and a third revolute pair which are connected in sequence, wherein the first revolute pair is rotationally connected with the first joint, and the third revolute pair is rotationally connected with the third joint;

the transforming the driving parameters of the second joint according to an eighth transformation matrix comprises the steps of:

and obtaining a driving parameter transformation relation from the first joint to the third revolute pair, and solving to obtain driving parameters of the first revolute pair, the second revolute pair and the third revolute pair according to the eighth transformation matrix and the driving parameter transformation relation.

In this embodiment, the second joint may include a plurality of joints, such as a first revolute pair, a second revolute pair, and a third revolute pair, which are connected in sequence, where the first revolute pair is rotationally connected to the first joint, and the third revolute pair is rotationally connected to the third joint, and the plurality of joints included in the second joint may enable the driven arm to have a larger motion space.

Further, in the second joint, the driving parameter of the first revolute pair may be a rotation angle θ 5, the driving parameter of the first revolute pair may be a movement distance d6, the driving parameter of the second revolute pair may be a rotation angle θ 7, the driving parameter of the second revolute pair may be a movement distance d8, and the driving parameter of the third revolute pair may be a rotation angle θ 9, as shown in fig. 3.

In some embodiments, the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

and when the pose of the static platform is changed, the telescopic elements are adjusted according to the first telescopic amount, so that the current pose of the dynamic platform in a mechanical coordinate system is kept unchanged.

In this embodiment, in addition to adjusting the pose of the static platform by the passive arm, the telescopic element between the movable platform and the static platform needs to be adjusted to ensure that the current pose of the movable platform in the mechanical coordinate system remains unchanged when the pose of the static platform is changed, and only the pose of the static platform is changed to realize the zero return of the parallel platform.

In particular, the solution of the present application can be applied to a Stewart platform, which can associate 10 joints in series.

In the specific working process, the method can be divided into a pose transformation stage and a zero position returning stage of a moving coordinate system.

Control of tandem robots typically performs coordinate system transformations based on DH parameters or modified DH parameters. The two joints connected are adjacent joints. The transformation of the joint coordinate systems of two adjacent joints is usually represented by DH parameters or modified DH parameters. Taking a DH parameter as an example, two adjacent joint coordinate systems can be overlapped with each other by rotating θ and translating d around the Z axis and then rotating α and translating a around the X axis, where θ, d, α and a are the DH parameters. It follows that if the DH parameters are more compact, the conversion of the two adjacent joint coordinate systems is simpler.

The DH parameters of each joint are known, and the conversion matrix between two adjacent joints is known according to positive kinematics of the robot as

The transformation matrix from the m-th joint (containing the degrees of freedom of the m-joint) to the n-th joint can be expressed as:

after the instrument surgical field center is reconstructed, the following equation relationship can be established according to the fact that the pose of the Stewart platform moving forward and backward under the mechanical coordinate system is unchanged:

T_0_4×T_4_9₁×T_9_10×T_s_end_m_end

＝T_machine_s_begin×T_s_begin_m_end (3)

wherein T _0_4 represents a conversion matrix from a mechanical coordinate system to a 4 th joint coordinate system; t _4_9₁Representing a transformation matrix from a 4 th joint coordinate system to a 9 th joint coordinate system after the zero position state is reconstructed and returned; t _9_10 represents a conversion matrix from the 9 th joint coordinate system to the 10 th joint coordinate system; t _ s _ end _ m _ end represents a conversion matrix between the Stewart platform static coordinate system and the dynamic coordinate system when the Stewart platform is rebuilt and returns to the zero state; t _ machine _ s _ begin indicates that the mechanical coordinate system is static before reconstructionConverting matrix between coordinate systems; and T _ s _ begin _ m _ end represents a conversion matrix between the static coordinate system and the dynamic coordinate system when the reconstructed Stewart platform does not return to the zero state.

From the formula (3)

Wherein, the left side of the equation is a conversion matrix containing the parameters to be solved, the right side of the equation is a known quantity, T _4_9₀The transformation matrix, T _4_9, representing the time when the DH parameters of the 5 th-9 th joint have not been updated₁And representing a transformation matrix from the 4 th joint coordinate system to the 9 th joint coordinate system after the zero position state is reconstructed and returned. Because the parameters of the passive joint arms DH of the 1 st to 4 th and the 10 th have no change in the whole process, the expression of each matrix can be obtained as follows:

T_machine_s_begin＝T_0_4×T_4_9₀×T_9_10 (6)

m in formula (8)_ozWhen the zero position state is represented, the distance between the dynamic coordinate system and the static coordinate system in the Z-axis direction of the static coordinate system is increased.

Let phi_x、φ_y、φ_zEuler angles, m, about the x, y, z axes respectively_x、m_y、m_zThe coordinate positions of the moving coordinate system at any moment under the static coordinate system are respectively, and the conversion matrix from the static coordinate system to the moving coordinate system at any moment is as follows:

as shown in fig. 3, the transformation matrix from the 4 th joint coordinate system to the 9 th joint coordinate system can obtain the expression:

and (4) obtaining the DH parameters of the 5 th-9 th joint to be updated by the corresponding elements of the matrixes on the two sides of the equation (4) being equal. In establishing the equation relationship, since T _4_9 has 0 element, it must first be satisfied that:

T_4_9₁[3,3]＝0 (11)

through derivation:

T_4_9₁[3,3]＝sinθ₉(sinφ_xcosφ_z+cosφ_x sinφ_ysinφ_z)-cosθ₉cosφ_ysinφ_z

then there is

sinθ₉(sinφ_xcosφ_z+cosφ_xsinφ_ysinφ_z)-cosθ₉cosφ_ysinφ_z＝0 (12)

Wherein, theta₉For the 9 th articulated arm DH parameter of the series arm, phi_xIs the Euler angle phi of the moving coordinate system around the self X axis_zThe Euler angle of the movable coordinate system around the Z axis is shown. From equation (12):

when sin theta₉cosφ_xsinφ_y-cosθ₉cosφ_yWhen equal to 0, phi_z＝90°；

When sin theta₉cosφ_xsinφ_y-cosθ₉cosφ_yWhen not equal to 0, combining the formulas (2), (3) and theta₉The following can be obtained:

in the whole reconstruction process, a conversion matrix corresponding to the rotational motion in the Z-axis direction between the dynamic coordinate system and the static coordinate system is recorded as T _ rota _ Z:

then, in the process of reconstructing the operative field, the static platform is adjusted to be parallel to the movable platform, and the transformation matrix T _ s _ m _ input between the dynamic coordinate system and the static coordinate system is set as

T _ s _ m _ input is calculated from the position information transmitted from the master hand and is a known quantity. The euler angle of the motion coordinate system around the axis of the motion coordinate system X, Y can be calculated according to the formula (15):

φ_x＝arcsin(T_s_m_input(3,2))

φ_y＝arcsin(T_s_m_input(1,3))

the operation field reconstruction process can be divided into a pose transformation stage and a zero position returning stage of a moving coordinate system. The 'pose transformation stage' is a process of keeping the pose of the movable platform under a mechanical coordinate system still and moving the static platform to a position which is parallel to the movable platform and is collinear with the Z axis; the 'return zero position stage of the moving coordinate system' is that the moving platform rotates phi around the Z axis of the moving platform_zThe Stewart platform returns to zero.

Before and after reconstruction, the static coordinate system conversion matrix and the dynamic and static coordinate system conversion matrix have the following relations:

T_machine_s_begin×T_s_begin_m_end＝T_machine_s_end×T_s_end_m_end (16)

therefore, the transformation matrix representing the pose of the static coordinate system after reconstruction is as follows:

T_machine_s_end＝T_machine_s_begin×T_s_begin_m_end×T_s_end_m_end^-1 (17)

wherein T _ machine _ s _ end is a transformation matrix from a reconstructed mechanical coordinate system to a static coordinate system, T _ s _ end _ m _ end is a zero transformation matrix of a dynamic and static coordinate system, and

so far, the moving target of the pose transformation stage can be defined:

connecting the motion targets of the articulated arms in series: t _ machine _ s _ begin → T _ machine _ s _ end;

moving the target by the Stewart platform: t _ s _ m _ input → T _ s _ end _ m _ end × T _ rota _ z

(φ_zAt this time, it is taken as-phi_z. The total angle is phi because the movable platform rotates around the Z axis of the movable platform_zRelative to the zero position state, the description of the Euler angle between the dynamic and static coordinate systems during the rotation process should be-phi_z)。

In some embodiments, the pose transformation of the static platform according to the current pose of the movable platform and the target pose of the static platform comprises the following steps:

acquiring an original pose of the static platform before reconstruction, interpolating the original pose and the target pose of the static platform, and acquiring an intermediate pose of the static platform in a pose transformation process;

and performing position transformation and posture transformation on the static platform according to the intermediate posture and the current posture of the movable platform, wherein the position transformation comprises circular arc motion transformation taking a telecentric motionless point as a circle center and linear motion transformation pointing to the circle center, and the posture transformation comprises rotation transformation of a static coordinate system around a Z axis of a mechanical coordinate system and rotation transformation of the static coordinate system around a Y axis of the static coordinate system.

In this embodiment, the original pose and the target pose of the static platform are interpolated to obtain an intermediate pose of the static platform in the in-place pose transformation process, a path of the static platform returning to the zero position can be planned by using the intermediate pose, and the position transformation and the posture transformation of the static platform are performed on the path, so that the static platform keeps smooth in the motion process, and the motion precision of the static platform is ensured.

Furthermore, in the position conversion, the circular arc motion conversion taking a telecentric fixed point as a circle center and the linear motion conversion pointing to the circle center can be simultaneously carried out; in the posture transformation, the rotation transformation of the static coordinate system around the Z axis of the mechanical coordinate system and the rotation transformation of the static coordinate system around the Y axis of the static coordinate system can be simultaneously carried out.

Specifically, the motion of the static platform in the pose transformation stage is interpolated and kinematically solved. And performing pose interpolation on the motion process of the static coordinate system according to the confirmed moving target, as shown in fig. 4.

(1) Position interpolation

The position interpolation target is the position of the static coordinate system in space before reconstruction, and is shown by S in figure 4 along a certain track₀Moves to the reconstructed target position S₁. Firstly, the motion track is searched through motion planning, then a coordinate system with a remote center point as an original point is established, each point of a motion track curve is mapped under the coordinate system, and finally the coordinate of a motion track point under a mechanical coordinate system is obtained through a newly established coordinate system conversion matrix.

As shown in fig. 3, the position interpolation process is divided into two motions. Movement 1: circular arc motion with the center of the far center point as the center and r0 as the radius; and (3) movement 2: the linear motion along the radius r pointing to the center of the circle, namely the motion with the radius r0 changing constantly. The motion trail formed by the combination of the two is a curvilinear motion with a radius changing from r0 to r1, like the motion trail of the static coordinate system in fig. 4.

Wherein, the variable θ r symbolizing circular motion is changed from 0 to θ by taking Δ θ as increment, the variable r symbolizing linear motion is changed from r0 to r1 and from 0 to θ by taking Δ r as variable quantity, and the number of interpolation points is set as N, so that the included angle θ r between the ith interpolation point and the initial position and the radius r are as follows:

the origin OF is set to the remote center point F,the vector is in the forward direction of the XF axis,the result is a ZF axis forward direction, the YF axis forward direction satisfies the right hand rule, establishing a apothem coordinate system O as shown in FIG. 3_F-X_FY_FZ_FIf the coordinate value of the ith interpolation point is:

x＝r×cosθ_r，y＝r×sinθ_r，z＝0 (21)

is recorded as location _ pre (i) [. times.cos Theta ]_r；r×sinθ_r；0；1]

Apocenter coordinate system O_F-X_FY_FZ_FThe pose matrix T _ machine _ dm in the mechanical coordinate system is recorded as:

wherein n is_x，n_y，n_zThe cosine value of an included angle of an Xdm axis relative to the global x, y and z axes; o_x，o_y，o_zIs the cosine of the angle formed by the axis Ydm with respect to the global x, y, z axes; a is_x，a_y，a_zIs the cosine of the angle formed by the axis Zdm with respect to the global x, y, z axes; x_F，Y_F，Z_FThe coordinates of the far center point in the mechanical coordinate system.

According to the establishment of the coordinate system, the following parameters can be obtained, where fix is the coordinate of the far center point before reconstruction in the static coordinate system, and is a known quantity:

[x_F；y_F；z_F；1]＝T_machine_s_begin×fix (23)

substituting equations (23) - (26) into equation (22) to obtain the pose matrix T _ machine _ dm of the coordinate system of the remote center point in the global coordinate system, where the coordinate value location (i) of the ith interpolation point in the global coordinate system is:

location(i)＝T_machine_dm×location_pre(i) (27)

and at this point, the position interpolation work is finished, and the global coordinate of each interpolation point in the motion trail is stored in the array location. The attitude interpolation will be performed below.

(2) Attitude interpolation

The pose interpolation target is obtained by transforming the pose before the reconstruction of the static coordinate system into the pose of the reconstructed target according to a certain rule, as shown in fig. 5. Due to the mechanical structure limitation, during the posture transformation, the axis of the static coordinate system Y0 needs to be parallel to the XY plane of the global coordinate system at any time, so as shown in fig. 4, the posture transformation is divided into 2 parts: firstly, a static coordinate rotates around a global Z axis; ② the static coordinate rotates around the Y0 axis. Therefore, firstly, 2 rotation angles are obtained by reconstructing the attitude relationship of the front and rear static coordinate systems, then the 2 angles are respectively subjected to linear interpolation, and finally, a series of continuous transformation arrays consisting of interpolation points are formed.

Since 2 transformation processes all satisfy the parallel condition, can be carried out simultaneously. Thus, the pose transformation process can be described as follows:

R_rotate_posture＝R_z×R_machine_s_begin×R_y (28)

wherein, R _ rotate _ posture represents the rotation matrix of the ith interpolation point in the global coordinate system; r _ machine _ s _ begin is a static coordinate system rotation transformation matrix before reconstruction, and the transformation matrix T _ machine _ s _ begin is composed of 9 elements of 1-3 rows and 1-3 columns of the transformation matrix T _ machine _ s _ begin; r _ Z represents a transformation process around the global Z axis; r _ Y denotes Y around a static coordinate system₀And (5) an axis changing process.

Wherein theta is_z、θ_yThe rotation angles around the global Z axis and the Y0 axis between the ith interpolation point and the static coordinate system before reconstruction are respectively represented, and the rotation angles can be obtained by the formula (28), and the posture rotation matrix before and after reconstruction should meet the following requirements:

R＝R_machine_s_end×R_y^-1＝R_z×R_machine_s_begin(31)

wherein R _ machine _ s _ end is a reconstructed stationary coordinate system rotation matrix which is composed of 9 elements of the 1 st to 3 rd rows and the 1 st to 3 rd rows of the transformation matrix T _ machine _ s _ end;

taking the two-sided matrix elements R (1,2) and R (2,2) of equation (31) can be obtained

According to the equation set, the rotation angle theta required by the transformation from the pre-reconstruction state to the post-reconstruction state can be obtained by dividing the two equations_zIs marked as alpha_z。

Order to

Similarly, the matrix elements R (3,1) and R (3,3) of the formula (31) can be obtained

According to the equation set, the rotation angle theta required by the transformation from the pre-reconstruction state to the post-reconstruction state can be obtained by dividing the two equations_yIs marked as alpha_y。

Order to

During the whole attitude transformation, theta_z、θ_yAt each angle of Delta theta_z、Δθ_yIn increments, varying from 0 to a_z、α_yIf the number of interpolation points is equal to the position interpolation and is N, the rotation angle parameter theta of the ith interpolation point is_z、θ_yCan be expressed as:

the ith interpolation point parameter is recorded in the set of postures, which can be expressed as:

and at this point, the attitude interpolation work is finished, and all the attitude parameters of the interpolation points are recorded in the array posture.

In some embodiments, the position transformation and the posture transformation of the static platform according to the intermediate pose and the current pose of the movable platform comprise the following steps:

converting the intermediate pose into a ninth conversion matrix between a static coordinate system and a mechanical coordinate system and a tenth conversion matrix between the static coordinate system and a dynamic coordinate system; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located;

changing the attitude parameters of the joints of the driven arm according to the ninth conversion matrix and the tenth conversion matrix, wherein the driven arm is connected with the static platform;

and acquiring a second telescopic quantity of the telescopic element according to the ninth conversion matrix and the tenth conversion matrix, and adjusting the telescopic element according to the second telescopic quantity so as to keep the current pose of the movable platform under the mechanical coordinate system unchanged.

In this embodiment, the position and attitude of the static platform are changed according to the intermediate pose and the current pose of the movable platform, which are implemented by changing the attitude parameters of the joints of the driven arm and adjusting the extension and retraction of the telescopic elements. And converting the intermediate pose into a ninth conversion matrix between a static coordinate system and a mechanical coordinate system and a tenth conversion matrix between the static coordinate system and a dynamic coordinate system, acquiring the attitude parameters of the joint of the driven arm and the second stretching amount of the stretching element by using the ninth conversion matrix and the tenth conversion matrix, and further performing intermediate pose transformation to ensure that the static platform keeps smooth in the motion process and ensure the motion precision of the static platform.

Further, after obtaining the attitude parameter of the joint of the passive arm and the second expansion and contraction amount of the expansion and contraction element, the drive parameter of the joint of the passive arm and the drive parameter of the expansion and contraction element may be further analyzed to realize the attitude parameter of the joint of the passive arm and the second expansion and contraction amount of the expansion and contraction element.

Specifically, the analysis of the attitude parameter of the joint of the passive arm and the second expansion/contraction amount of the expansion element may be referred to as pose interpolation kinematics calculation. And the kinematic calculation part converts parameters obtained by (1) position interpolation and (2) attitude interpolation into a conversion matrix describing the attitude of a static coordinate system and a conversion matrix between the static coordinate system and the static coordinate system, and then respectively calculates the conversion matrixes to the motion drives of the serial articulated arm and the Stewart platform to finally obtain all required driving parameters.

As can be seen from (1) position interpolation and (2) attitude interpolation, the ith interpolation point position description is obtained from the array location, and the attitude description is obtained from the array posture, the ith interpolation point rotation angle can be converted into a rotation matrix R _ rotate _ posture (i) by equation (28), and then the mechanical coordinate system to the point static coordinate system conversion matrix can be expressed as:

at this time, the transformation matrix between the moving and static coordinate systems can be expressed as:

T_s_m_i＝T_machine_s_i^-1×T_machine_m_mid (38)

wherein, T _ machine _ m _ mid is T _ machine _ s _ begin × T _ s _ m _ input.

Solving driving parameters of a serial joint arm:

replacing T _ s _ begin _ m _ end in the formula (4) by T _ s _ m _ input, correspondingly replacing T _ s _ m _ i by T _ s _ end _ m _ end in the formula (4), and still enabling the equation to be established to obtain

Wherein T _4_9_iAnd the transformation matrix from the 4 th joint coordinate system to the 9 th joint coordinate system of the ith interpolation point is represented.

From the formula (38)

According to the equation (40), the corresponding terms of the matrixes on the two sides are equal, the value range is solved by comprehensively considering matlab inverse trigonometric function, and the expression of each parameter to be solved in the serial joint arm can be obtained:

θ_7i＝arcsin[T_4_9_i(2,3)×cosθ₅-T_4_9_i(1,3)×sinθ₅] (41)

d_8i＝-T_4_9_i(3,4) (42)

θ_9i＝arcsin T_4_9_i(3,2) (43)

a) if T _4_9_iWhen (2,4) ═ 0, then:

θ_5i＝90° (44)

d_6i＝a₄-T_4_9_i(1,4) (45)

b) if T _4_9_i(2,4) ≠ 0, then:

θ_5i＝arccos(T_4_9_i(2,4)/d₆) (46)

and stores the calculated N sets of DH parameters in the set DH _ update _ po.

Stewart drive solution process:

and (4) establishing according to a Stewart coordinate system, and calculating the relative coordinates of the movable hinge point in the movable coordinate system and the static hinge point in the static coordinate system. Taking the coordinate calculation of the stationary hinge point as an example, the stationary hinge point S is first calculated according to the above description_i(i 1-6) from the origin O of the stationary coordinate system_SMoving to a stationary coordinate system X_SThe axes and the static coordinate system platform are distributed at the circumferential intersection (as shown in FIG. 6 (c)), and the coordinate value is (r)_s，0)。

According to the plane coordinate rotation theorem, the coordinates of an arbitrary coordinate point (x, y) rotated by an angle theta around the origin are expressed as

x′＝xcosθ-ysinθ，y′＝xsinθ+ycosθ (48)

Will coordinate (r)_s0) as a value of x, y into equation (48), its coordinates can be expressed as

(ss_ix，ss_iy)＝(r_scosθ_si，r_ssinθ_si) (49)

Wherein theta is_siThe rotation angle is the rotation angle from the intersection point to the corresponding hinge point by taking the origin of the static coordinate system as the center of a circle.

The origin of the coordinate system of the static platform is defined at the center of the plane where the static hinge point is located, so that the ZS axial coordinate of any static hinge point under the static coordinate system is 0, and the homogeneous coordinate of the static hinge point on the static platform can be obtained by considering coordinate rotation and translation transformation:

S_i＝(ss_ix，ss_iy，0，1)

as shown in fig. 6(c), the rotation angles during the respective hinge point shifts are given in table 1.

TABLE 1 corresponding rotation angle of static hinge point

In the same way, the homogeneous coordinate of the movable hinge point under the movable coordinate system is obtained:

M_i＝(mm_ix，mm_iy，0，1)

as shown in fig. 6(c), the rotation angles during the respective hinge point shifts are given in table 2.

TABLE 2 corresponding rotation angle of movable hinge point

From equation (38), the coordinates of the movable hinge point under the static coordinate system are:

calculating the distance between any pair of dynamic and static hinge points according to a distance formula between two points in a three-dimensional space:

subtracting the initial rod length from the value to obtain the driving parameters of each rod.

The calculated N sets of respective rod drive parameters are stored in the array L _ mark _ po.

The serial arm and the Stewart platform respectively and sequentially read parameters in the array dh _ update _ po and the array L _ mark _ po, so that the static platform can move to a position parallel to the dynamic platform in a determined track under the condition that the pose of the dynamic platform is static relative to the mechanical coordinate system. Thus, the pose transformation stage is completed.

In some embodiments, the rotating the moving platform according to the torsion angle to make the parallel platform return to the zero position includes the following steps:

interpolating the torsion angle to obtain a middle angle of the movable platform in the rotation transformation process;

and carrying out rotation transformation on the movable platform according to the intermediate angle and the current angle of the movable platform.

In some of these embodiments, the rotational transformation of the moving platform according to the intermediate angle and the current angle of the moving platform comprises the following steps:

and acquiring an eleventh conversion matrix between the static coordinate system and the moving coordinate system according to the middle angle, acquiring a third expansion amount of the telescopic element according to the eleventh conversion matrix, and adjusting the telescopic element according to the third expansion amount so as to enable the parallel platform to return to the zero position.

In this embodiment, when the movable platform is subjected to rotation transformation, the torsion angle may also be interpolated to obtain a middle angle of the movable platform in the rotation transformation process, an eleventh transformation matrix between the static coordinate system and the movable coordinate system is obtained by utilizing the transformation of the middle angle, and a third expansion amount of the expansion element is further obtained, and after the expansion element is adjusted, the movable platform returns to the zero position, so that the return to the zero position of the parallel platform is realized.

Furthermore, the third telescopic quantity can be converted into a driving parameter of the telescopic element, and the telescopic element is driven and adjusted.

In some embodiments, the control method for reconstructing the surgical field center of the instrument further comprises the following steps:

and after the parallel platform returns to the zero position, acquiring the coordinates of the telecentric motionless point under the static coordinate system after the operative field is reconstructed according to the conversion relation between the static coordinate system and the mechanical coordinate system after the operative field is reconstructed, wherein the coordinates of the telecentric motionless point under the mechanical coordinate system are unchanged.

In this embodiment, the coordinates of the telecentric motionless point in the static coordinate system after the reconstruction of the surgical field can be re-confirmed to facilitate the confirmation of the surgical site.

Specifically, through a 'pose transformation stage', the pose of the static coordinate system meets the pose requirement after reconstruction, the Stewart platform still rotates around the Z axis of the dynamic coordinate system relative to the static coordinate system, so that the serial arm in the stage keeps still, and the Stewart platform interpolates the rotation angle around the Z axis and calculates the corresponding driving parameters of the Stewart platform.

The target is as follows: t _ s _ m _ rota → T _ s _ end _ m _ end. The motion of the movable platform in the zero position returning stage of the movable coordinate system is interpolated and kinematically solved as follows.

The motion at this stage is: the movable platform rotates around the Z axis of the movable platform, and the total angle is phi_zRelative to the zero position state, the description of the Euler angle between the dynamic and static coordinate systems during the rotation process should be-phi_z。

If the number of interpolation points is M, eula angle description eula _ z between the moving and static coordinate systems of the ith interpolation point should be:

the transformation matrix T _ s _ m _ rota _ z _ i between the moving coordinate system and the static coordinate system of the ith interpolation point is as follows:

according to the method for Stewart drive resolving process, replacing T _ s _ M _ i with T _ s _ M _ rota _ z _ i, obtaining M groups of driving rod parameters by the same method, storing the M groups of driving rod parameters into an array L _ mark _ rota _ z, and forming a driving L _ mark _ re _ update of a Stewart platform together with L _ mark _ po in the whole reconstruction process:

L_mark_re_update＝[L_mark_po；L_mark_rota_z] (54)

the DH parameters of the serial joint arms in the reconstruction process are parameters during pose interpolation:

dh_re_update＝dh_update_po (55)

after the Stewart platform finishes the pose transformation stage, the pose transformation stage and the pose transformation stage are sequentially carried outReading array parameters in the array L _ mark _ rota _ Z, namely rotating the coordinate system around the Z axis of the coordinate system by phi_zStewart is returned to zero. And finishing the zero position returning stage of the moving coordinate system, namely finishing the whole operative field reconstruction process.

In addition, in order to make the operation normally performed, the coordinates of the telecentric fixed point in the static coordinate system need to be obtained again and input into the system. In the process of reconstructing the operative field, the pose of the static platform is changed, but the coordinate of the telecentric motionless point under the mechanical coordinate system is unchanged, and according to the conversion relation between the static coordinate and the mechanical coordinate obtained after reconstructing the operative field, the coordinate of the telecentric motionless point under the static coordinate system after reconstructing the operative field can be obtained and is marked as fix _ new:

fix_new＝T_machine_s_end^-1×T_machine_s_begin×fix (56)

in one embodiment, the control steps for reconstructing the surgical field center of the instrument are as follows:

1. a pose transformation stage:

firstly, a pose transformation matrix T _ machine _ s _ begin of a static coordinate system before reconstruction under a mechanical coordinate system is solved through joint information of a driven arm.

And resolving a pose transformation matrix T _ machine _ s _ end of the reconstructed static coordinate system in the mechanical coordinate system according to the pose information of the movable platform in the mechanical coordinate system. Because the driven arm has only 5 degrees of freedom, the Stewart attitude return to zero can not be completely realized only by the movement of the driven arm, and therefore a torsion in the Z-axis direction may exist between the static coordinate system and the moving coordinate system obtained by the calculation.

And thirdly, performing position interpolation and attitude interpolation on the intermediate track and the attitude according to the attitude matrixes of the static coordinate system before and after the reconstruction of the surgical field to obtain a series of attitude matrixes T _ machine _ s of the static coordinate system under the mechanical coordinate system in the intermediate process, and resolving motion information dh _ update _ po of 5 joints of the driven arm between each interpolation point through inverse kinematics of the driven arm so that the static coordinate system moves to the reconstructed preset attitude according to the trajectory of the interpolation point.

And fourthly, in the same time of the third step, namely in the interpolation process, obtaining a conversion matrix T _ s _ m between the dynamic coordinate system and the static coordinate system of the interpolation point according to the pose information of the movable platform in the mechanical coordinate system and the attitude matrix of the interpolation pose of the static platform in the mechanical coordinate system, and resolving the length L _ mark _ po of the six driving rods of the Stewart platform according to the Stewart platform inverse kinematics so that the pose of the movable platform in the mechanical coordinate system is kept static in the motion process of the static platform.

2. The return zero position stage of the dynamic coordinate system:

according to the explanation in the second point of the pose transformation stage, the Stewart platform cannot be completely returned to the zero position in the pose transformation stage, a torsion in the Z-axis direction can exist between the moving platform and the static platform, and the Stewart platform cannot be returned to the zero position by adjusting the posture of the static platform due to the limitation of the degree of freedom of the driven arm, so that the Stewart platform is selectively controlled to rotate around the Z axis to return to the zero position. The rotation of the movable platform can cause the instrument to rotate around the Z axis, but the telecentric motionless point principle is not violated, the surgical field center of the instrument is not changed, and the reconstruction of the surgical field center can be effectively finished.

And calculating torsion angles between the moving coordinate system and the static coordinate system according to a pose matrix of the moving coordinate system and the static coordinate system under a mechanical coordinate system after the pose transformation stage is completed, performing multi-point interpolation on the angles, calculating the lengths L _ mark _ po of the six driving rods of the Stewart platform at each difference point according to Stewart platform inverse kinematics, and enabling the Stewart platform to rotate around the Z axis at a corresponding speed until the Stewart platform returns to a zero point position.

The present embodiment further provides a control system for reconstructing a surgical field center of an instrument, which is used to implement the above embodiments and preferred embodiments, and the description of the system is omitted here. As used below, the term "module" or the like may implement a combination of software and/or hardware of predetermined functions. While the system described in the embodiments below is preferably implemented in software, implementations in hardware, or a combination of software and hardware are also possible and contemplated.

Fig. 7 is a block diagram of a control system for reconstructing a surgical field center of an instrument according to an embodiment of the present application, as shown in fig. 7, the system including:

the first obtaining module 210 is configured to obtain a current pose of the movable platform in a mechanical coordinate system after the surgical field center of the reconstruction instrument is reconstructed, where the mechanical coordinate system is a global coordinate system of a mechanical arm where the movable platform is located;

a second obtaining module 220, configured to obtain, according to the current pose of the moving platform, a target pose of the static platform in the mechanical coordinate system after the surgical field center of the reconstruction instrument is obtained, where the moving platform and the static platform are parallel platforms connected to each other through a telescopic element in the mechanical arm, a center of the target pose of the static platform is on a central axis of the current pose of the moving platform, and the static platform in the target pose is parallel to the moving platform;

the first transformation module 230 is configured to perform pose transformation on the static platform according to the current pose of the dynamic platform and the target pose of the static platform;

and the second transformation module 240 is configured to acquire a torsion angle between the movable platform and the static platform on the central axis according to the current pose of the movable platform and the target pose of the static platform, and perform rotation transformation on the movable platform according to the torsion angle, so that the parallel platform returns to a zero position.

In some embodiments, the first transformation module 230 is further configured to obtain a first transformation matrix from the static coordinate system to the dynamic coordinate system when the reconstructed and returned to the zero position state is obtained according to the current pose of the dynamic platform and the target pose of the static platform; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located; acquiring a second conversion matrix from the static coordinate system to the dynamic coordinate system when the zero state is rebuilt but not returned; and reconstructing a third transformation matrix from the mechanical coordinate system to the static coordinate system before reconstruction; acquiring a fourth conversion matrix from the reconstructed mechanical coordinate system to the static coordinate system according to the first conversion matrix, the second conversion matrix and the third conversion matrix; and acquiring a fifth conversion matrix between joint coordinate systems of a passive arm in the mechanical arm according to the fourth conversion matrix, and converting the attitude parameters of the joint of the passive arm according to the fifth conversion matrix, wherein the passive arm is connected with the static platform.

In some embodiments, the passive arm comprises a first joint, a second joint and a third joint which are connected in series, wherein the posture parameters of the first joint and the third joint are unchanged, and the third joint is connected with the static platform;

the first transformation module 230 is further configured to obtain a sixth transformation matrix from the mechanical coordinate system to the coordinate system of the first joint, and a seventh transformation matrix from the coordinate system of the second joint to the coordinate system of the third joint; acquiring an eighth conversion matrix from the first joint to the second joint according to the fifth conversion matrix, the sixth conversion matrix and the seventh conversion matrix; and transforming the attitude parameters of the second joint according to the eighth transformation matrix.

In some embodiments, the first transformation module 230 is further configured to obtain a first amount of stretching of the telescopic element according to the current pose of the moving platform and the target pose of the static platform, and adjust the telescopic element according to the first amount of stretching when performing pose transformation on the static platform, so as to keep the current pose of the moving platform in the mechanical coordinate system unchanged.

In some embodiments, the first transformation module 230 is further configured to obtain an original pose of the stationary platform before reconstruction, interpolate the original pose and the target pose of the stationary platform, and obtain an intermediate pose of the stationary platform during pose transformation; and performing position transformation and posture transformation on the static platform according to the intermediate posture and the current posture of the movable platform, wherein the position transformation comprises circular arc motion transformation taking a telecentric motionless point as a circle center and linear motion transformation pointing to the circle center, and the posture transformation comprises rotation transformation of a static coordinate system around a Z axis of a mechanical coordinate system and rotation transformation of the static coordinate system around a Y axis of the static coordinate system.

In some embodiments, the first transformation module 230 is further configured to transform the intermediate pose into a ninth transformation matrix between the static coordinate system and the mechanical coordinate system and a tenth transformation matrix between the static coordinate system and the dynamic coordinate system; the static coordinate system is a coordinate system where the static platform is located, and the moving coordinate system is a coordinate system where the moving platform is located; changing the attitude parameters of the joints of the driven arm according to the ninth conversion matrix and the tenth conversion matrix, wherein the driven arm is connected with the static platform; and acquiring a second telescopic quantity of the telescopic element according to the ninth conversion matrix and the tenth conversion matrix, and adjusting the telescopic element according to the second telescopic quantity so as to keep the current pose of the movable platform under the mechanical coordinate system unchanged.

In some embodiments, the second transformation module 240 is further configured to interpolate a torsion angle to obtain an intermediate angle of the moving platform in the rotation transformation process; and acquiring an eleventh conversion matrix between the static coordinate system and the moving coordinate system according to the middle angle, acquiring a third expansion amount of the telescopic element according to the eleventh conversion matrix, and adjusting the telescopic element according to the third expansion amount so as to enable the parallel platform to return to the zero position.

As shown in fig. 8, the present application further provides a control apparatus for reconstructing a surgical field center of an instrument, which includes a robotic arm 310 and a control device 320;

the control device 320 is used for performing pose transformation on the static platform on the mechanical arm 310 and performing rotation transformation on the movable platform on the mechanical arm 310 according to the control method for reconstructing the surgical field center of the instrument in the first aspect.

Above-mentioned control apparatus of rebuilding apparatus art field center carries out the position appearance transform to quiet platform on arm 310 through controlling means 320, carries out rotation transformation to the moving platform on arm 310, has realized that the parallel platform returns the zero bit, has solved the problem that parallel robot that exists among the correlation technique is difficult to realize the gesture and has returned zero, has promoted the control accuracy of rebuilding apparatus art field center, guarantees the motion performance of parallel platform.

The embodiment of the application also provides a readable storage medium, wherein an executable program is stored on the readable storage medium, and when the executable program is executed by a processor, the executable program realizes the control method for reconstructing the surgical field center of the instrument.

The readable storage medium can realize the return to the zero position of the parallel platform by running the executable program on the processor, solves the problem that the parallel robot in the related technology is difficult to realize the posture return to the zero position, improves the control accuracy of the surgical field center of the reconstruction instrument, and ensures the motion performance of the parallel platform.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

Those skilled in the art will appreciate that all or part of the steps in the method for implementing the above embodiments may be implemented by a program instructing the relevant hardware. The program may be stored in a readable storage medium. Which when executed comprises the steps of the method described above. The storage medium includes: ROM/RAM, magnetic disk, optical disk, etc.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.