阅读说明：本技术 定位臂 (Positioning arm ) 是由 权东秀 金昶均 千昞植 于 2019-08-07 设计创作，主要内容包括：一种定位臂,包括：连杆组件,其具有可沿通过距离一点规定距离的远程运动中心(RCM)的虚拟轴进行平移的平移连杆,并且,以所述一点为中心在至少两个方向上旋转；以及重力扭矩补偿部,其提供补偿扭矩,所述补偿扭矩的方向与所述连杆组件的自身重量作用于所述一点的重力扭矩的方向相反。(A positioning arm, comprising: a link assembly having a translation link that is translatable along a virtual axis passing through a Remote Center of Motion (RCM) at a prescribed distance from a point, and rotates in at least two directions centered on the point; and a gravity torque compensation portion that provides a compensation torque in a direction opposite to a direction of a gravity torque in which the own weight of the link assembly acts on the one point.)

1. A positioning arm is characterized in that a positioning arm is arranged on a base,

the method comprises the following steps:

a link assembly having a translation link that is translatable along a virtual axis passing through a Remote Center of Motion (RCM) at a prescribed distance from a point, and rotatable in at least two directions about the point; and

a gravity torque compensation portion that provides a compensation torque in a direction opposite to a direction of a gravity torque in which the own weight of the link assembly acts on the one point.

2. Positioning arm according to claim 1,

the linkage assembly is capable of roll rotation and pitch rotation, and the translating linkage is translatable along a virtual axis through the remote center of motion independently of the roll rotation angle and the pitch rotation angle.

3. Positioning arm according to claim 2,

the link assembly further includes:

a gear box which can roll and rotate relative to the bottom;

a pitch link that is rotatable in pitch relative to the gearbox;

a parallel link movable in a posture parallel to a longitudinal direction of the pitch link; and

a connecting rod connecting the pitch link and the parallel link,

the translating link is translatable along a guide located on the parallel link.

4. Positioning arm according to claim 3,

further comprising:

a central bevel gear fixed to the bottom;

a pair of rotary bevel gears respectively engaged with both sides of the central bevel gear and rotatable with respect to the gear case; and

and a pair of rotating bodies fixed to the pair of rotating bevel gears, respectively, and rotatable with respect to the gear box together with the pair of bevel gears, respectively.

5. Positioning arm according to claim 4,

a connecting shaft portion is formed between each of the pair of rotary bevel gears and the corresponding pair of rotary bodies,

the link assembly is provided to the connection shaft portion so as to be rotatable in one direction.

6. Positioning arm according to claim 4,

the pair of rotating bevel gears do not move relatively when the connecting rod assembly rotates in a pitching mode, and rotate reversely relative to the same shaft when the connecting rod assembly rotates in a rolling mode.

7. Positioning arm according to claim 4,

the gravity torque compensation part includes:

a pair of elastic bodies that change in length according to rolling rotation or pitching rotation of the link assembly, thereby providing elastic force that generates the compensation torque.

8. Positioning arm according to claim 7,

the gravity torque compensation part further comprises:

a support base located on one side of the pair of elastic bodies;

a pair of sliders located on the other side of the pair of elastic bodies and slidable with respect to the pitch link; and

and a pair of compensating steel wires, one side of each compensating steel wire being fixed to the pair of rotating bodies, and the other side of each compensating steel wire being fixed to the pair of sliders.

9. Positioning arm according to claim 8,

further comprising:

a gravity torque adjustment part that reduces a difference between the gravity torque and the compensation torque generated with a translation distance of the translation link.

10. Positioning arm according to claim 9,

the support table includes a support portion disposed on a side of a path through which the pair of compensating wires pass, and functioning to receive the compensating torque from the pair of compensating wires,

the gravity torque adjusting part reduces the support table when the translation connecting rod translates towards the remote motion center, so that the length of the force arm of the compensation torque is reduced, and improves the support table when the translation connecting rod translates towards the direction far away from the remote motion center, so that the length of the force arm of the compensation torque is increased.

11. The positioning arm of claim 10,

said support platform being arranged in a slidable manner relative to said pitch link,

the gravity torque adjusting part comprises an adjusting steel wire which is mutually connected with the translation connecting rod and the supporting platform so as to slide the supporting platform when the translation connecting rod translates.

12. The positioning arm of claim 11,

the gravity torque adjusting section further includes a speed change means for increasing or decreasing a sliding distance of the support table with respect to the pitch link in proportion to a translational distance of the translational link with respect to the parallel link.

13. The positioning arm of claim 12,

the adjusting steel wire comprises a first adjusting steel wire and a second adjusting steel wire which are respectively connected with one side and the other side of the speed changing means,

the speed change means includes:

a first reel for winding the first adjustment wire;

a second reel for winding the second adjustment wire; and

a speed reducer that causes the second drum to rotate relative to the first drum at a set rotation ratio.

14. Positioning arm according to claim 1,

and a gravity torque adjusting part which reduces a difference between the gravity torque and the compensation torque generated with a translation distance of the translation link.

15. A positioning arm is characterized in that a positioning arm is arranged on a base,

the method comprises the following steps:

a link assembly that is rotatable in roll and pitch and has a translation link that is translatable along a virtual axis passing through a Remote Center of Motion (RCM) at a prescribed distance from a point; and

a plurality of bevel gears which do not move relatively when the connecting rod assembly rotates in a pitching manner and rotate in a meshing manner when the connecting rod assembly rotates in a rolling manner;

a rotating body connected to one or more of the bevel gears and rotating together with the bevel gears; and

and a gravity torque compensation part connected to the rotating body and deforming the elastic body according to the rolling rotation and the pitching rotation of the link assembly, thereby providing a compensation torque having a direction opposite to that of the gravity torque due to the own weight of the link assembly.

16. The positioning arm of claim 15,

the gravity torque adjusting part is used for increasing and decreasing the arm length of the compensation torque according to the translation of the translation connecting rod, so that the difference between the gravity torque and the compensation torque is reduced.

Technical Field

Example embodiments relate to a positioning arm.

Background

Robots are used in various fields such as medical treatment and industry. For example, in the medical field, a support device including a positioning arm (positioning arm) is used as a part of a surgical robot system, and thus a surgical tool (surgical instrument) and a robot arm (robot arm) are freely and stably positioned.

Generally, a positioning arm having a rotational degree of freedom is used, and is widely used in a laparoscopic surgical robot and a surgical robot such as a Da Vinci system (Da Vinci system). The weight of the positioning arm itself or the weight of an instrument (instrument) loaded on the positioning arm acts on the joint of the positioning arm, and a gravitational torque is generated accordingly. Gravity torque may change the attitude of the positioning arm, and therefore constant force needs to be constantly applied to keep the attitude of the positioning arm constant. For example, the force to support the positioning arm may be provided by the user, or an actuator such as a motor may be used to provide a continuous torque, or a brake may be used to secure.

However, due to the weight of the positioning arm, it is difficult for the user to perform the operation while continuously providing the force, and the weight of the positioning arm that can be borne is limited. Further, even if an actuator such as a motor is used, an excessive load is applied, and in order to solve this problem, there are often problems of an increase in cost, an increase in volume, and a decrease in efficiency with respect to volume. The manner in which the brake is applied for fixing requires the brake to be released and tightened, which reduces the ease of use and also requires the weight of the positioning arm to be manually borne when the brake is released to adjust the position of the positioning arm. Therefore, a gravity compensation device for compensating the weight of the positioning arm itself is required.

The above background is the content of the present invention grasped or learned by the inventors during the development of the present invention, and should not be construed as necessarily requiring the commonly known technology disclosed before the present invention is applied.

Disclosure of Invention

Technical problem

This aspect provides a positioning arm that employs a gravity compensation mechanism for three degrees of freedom motion.

Technical scheme

A locator arm according to an embodiment, comprising: a link assembly having a translation link that is translatable along a virtual axis passing through a Remote Center of Motion (RCM) at a prescribed distance from a point, and rotates in at least two directions centered on the point; and a gravity torque compensation portion that provides a compensation torque in a direction opposite to a direction of a gravity torque in which the own weight of the link assembly acts on the one point.

The linkage assembly is capable of roll rotation and pitch rotation, and the translating linkage is translatable along a virtual axis through the remote center of motion independently of the roll rotation angle and the pitch rotation angle.

The link assembly further includes: a gear box which can roll and rotate relative to the bottom; a pitch link that is rotatable in pitch relative to the gearbox; a parallel link movable in a posture parallel to a longitudinal direction of the pitch link; and a connecting rod connecting the pitch link and the parallel link, the translation link being translatable along a guide located at the parallel link.

The positioning arm further comprises: a central bevel gear fixed to the bottom; a pair of rotary bevel gears respectively engaged with both sides of the central bevel gear and rotatable with respect to the gear case; and a pair of rotating bodies fixed to the pair of rotating bevel gears, respectively, and rotatable with respect to the gear box together with the pair of bevel gears, respectively.

A connecting shaft portion is formed between each of the pair of rotary bevel gears and the corresponding pair of rotary bodies, and the link assembly is provided to the connecting shaft portion so as to be rotatable in one direction.

The pair of rotating bevel gears do not move relatively when the connecting rod assembly rotates in a pitching mode, and rotate reversely relative to the same shaft when the connecting rod assembly rotates in a rolling mode.

The gravity torque compensation portion includes a pair of elastic bodies that change in length according to roll rotation or pitch rotation of the link assembly, thereby providing an elastic force that generates the compensation torque.

The gravity torque compensation part further comprises: a support base located on one side of the pair of elastic bodies; a pair of sliders located on the other side of the pair of elastic bodies and slidable with respect to the pitch link; and a pair of compensating steel wires, one side of each compensating steel wire being fixed to the pair of rotating bodies, and the other side of each compensating steel wire being fixed to the pair of sliders.

The positioning arm further includes a gravity torque adjustment portion that reduces a difference between the gravity torque and the compensation torque generated with a translation distance of the translation link.

The support table includes a support portion disposed at a side of a path through which the pair of compensation wires pass, and functioning to receive the compensation torque from the pair of compensation wires, and the gravity torque adjustment portion lowers the support table to reduce a force arm length of the compensation torque when the translation link is translated toward the remote movement center, and raises the support table to increase the force arm length of the compensation torque when the translation link is translated in a direction away from the remote movement center.

The support table is provided so as to be slidable with respect to the pitch link, and the gravity torque adjustment unit includes an adjustment wire that connects the translation link and the support table to each other, thereby sliding the support table when the translation link translates.

The gravity torque adjusting section further includes a speed changing means for increasing or decreasing a sliding distance of the support table with respect to the pitch link in proportion to a translational distance of the translational link with respect to the parallel link.

The adjusting steel wire comprises a first adjusting steel wire and a second adjusting steel wire which are respectively connected with one side and the other side of the speed changing means, and the speed changing means comprises: a first reel for winding the first adjustment wire; a second reel for winding the second adjustment wire; and a speed reducer that causes the second drum to rotate relative to the first drum at a set rotation ratio.

The positioning arm further includes a gravity torque adjustment portion that reduces a difference between the gravity torque and the compensation torque generated with a translation distance of the translation link.

A locator arm according to an embodiment, comprising: a link assembly that is rotatable in roll and pitch and has a translation link that is translatable along a virtual axis passing through a Remote Center of Motion (RCM) at a prescribed distance from a point; and a plurality of bevel gears which do not move relatively when the connecting rod assembly rotates in a pitching manner and rotate in a meshing manner when the connecting rod assembly rotates in a rolling manner; a rotating body connected to one or more of the bevel gears and rotating together with the bevel gears; and a gravity torque compensation part connected to the rotating body and deforming the elastic body with the rolling rotation and the pitching rotation of the link assembly, thereby providing a compensation torque having a direction opposite to a gravity torque due to a self weight of the link assembly.

The positioning arm further comprises a gravity torque adjusting part which increases and decreases the arm length of the compensation torque according to the translation of the translation connecting rod, thereby reducing the difference between the gravity torque and the compensation torque.

Advantageous effects of the invention

The positioning arm according to an embodiment can be operated with little force by using a gravity compensation mechanism. In other words, the input torque that should be applied to the driving source can be reduced by the gravity compensation mechanism, and thus, a relatively small and light actuator can be used for driving, reducing the energy consumption solely for compensating for the gravity, and improving the energy efficiency.

In addition, even if the emergency situation of power failure occurs in the process of using the positioning arm, the positioning arm does not sink due to the action of gravity, and particularly the safety of the field of the surgical robot and the like can be improved.

The positioning arm according to an embodiment is provided with a gravity compensation mechanism that can stably maintain a variety of postures regardless of gravity in a hemispherical work space (hemispatial work space) with respect to a change in the center of gravity that varies with three degrees of freedom motions of roll, pitch, and translation of the end of the positioning arm. Therefore, the present invention can be widely used for surgical robots such as minimally invasive surgery (minimally invasive surgery) in which a fulcrum (fultrum) moves.

Drawings

FIG. 1 is a perspective view of a positioning arm according to an embodiment.

FIG. 2 is a side view conceptually illustrating a positioning arm, according to one embodiment.

FIG. 3 is a diagram illustrating pitch rotation of a positioning arm, translation of a translation link, according to an embodiment.

Fig. 4 is a plan view schematically showing a part of the positioning arm in a state where the positioning arm is rotated 90 degrees in pitch in the forward direction according to the embodiment.

FIG. 5 is a diagram illustrating pitch rotation of a positioning arm according to an embodiment.

Fig. 6 to 8 are drawings showing a rolling rotation of a positioning arm according to an embodiment.

Fig. 9 and 10 are diagrams showing the operation of the gravity torque adjusting portion when the translation link translates according to the embodiment.

FIG. 11 is a conceptual diagram of a positioning arm according to an embodiment.

Fig. 12a is a drawing illustrating a gravity torque adjustment part according to an embodiment.

Fig. 12b is an enlarged view showing a portion a of fig. 12 a.

Fig. 13 is a drawing illustrating a gravity torque adjustment part according to an embodiment.

Detailed Description

Embodiments are described in detail below with reference to the example drawings. When reference numerals are given to components in each drawing, the same components are denoted by the same reference numerals as much as possible even when they are shown in different drawings. In describing the embodiments, when it is judged that a detailed description of the related well-known art may unnecessarily obscure the embodiments, a detailed description thereof is omitted.

In addition, when describing the components of the embodiment, terms such as first, second, A, B, (a), (b), and the like may be used. These terms are only used to distinguish one constituent element from another constituent element, and are not used to limit the nature, order, and the like of the respective constituent elements. For example, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. Further, it should be understood that when one component is described in the specification as being "connected," "coupled," or "in contact with" another component, the third component may be "connected," "coupled," or "in contact" between the first component and the second component, although the first component can be directly connected, coupled, or in contact with the second component.

When a component has a function common to that of one embodiment, the component will be described with the same name in other embodiments. When no example is mentioned, the description of one embodiment can be applied to the other embodiments, and detailed description thereof is omitted.

FIG. 1 is a perspective view of a positioning arm according to one embodiment; FIG. 2 is a side view conceptually illustrating a positioning arm, in accordance with one embodiment; FIG. 3 is a diagram illustrating pitch rotation of a positioning arm, translation of a translation link, according to an embodiment; fig. 4 is a plan view schematically showing a part of the positioning arm in a state where the positioning arm is rotated 90 degrees in pitch in the forward direction according to the embodiment.

Referring to fig. 1 to 4, the end 114 of the positioning arm 1 according to an embodiment may implement at least three degrees of freedom with respect to the bottom B, specifically a roll rotation, a pitch rotation, and a translation. The coordinate system (x0, y0, z0) shown in fig. 1 to 4 is a global coordinate system with "one point" where the roll rotation axis (axis 1) and the pitch rotation axis (axis 2) intersect as an origin, and the x0 axis is set as the gravity direction.

The positioning arm 1 has a means that provides a compensating torque that opposes the gravitational torque acting on a point, whereby the power required to maintain the attitude of the positioning arm 1 can be reduced. The positioning arm 1 may include a link assembly 11, a center bevel gear 13, a rotation bevel gear 14, a rotation body 15, a connection shaft portion 16, a gravity torque compensation portion 17, and a gravity torque adjustment portion 18.

The link assembly 11 has a translation link 114 that translates along a virtual axis passing through a Remote Center of Motion (RCM) at a prescribed distance from a point, and can rotate in at least two directions centering on the point. For example, the linkage assembly 11 may roll and pitch, and the translating linkage 114 may translate along an axis through a Remote Center of Motion (RCM) regardless of roll and pitch rotation angles. The linkage assembly 11 may include a gear box 111, a pitch link 112, a translation link 114, a parallel link 115, and a connecting rod 116.

The gear box 111 can roll and rotate relative to the bottom B. For example, the gear box 111 is rotatably connected to a connecting shaft portion (no reference numeral) connecting the center bevel gear 13 and the bottom portion B. The gear box 111 has a structure through which the rotation shafts of the plurality of bevel gears 13, 14 pass, and supports the engagement of the rotation bevel gear 14 with the center bevel gear 13.

The pitch link 112 can rotate in pitch relative to the gear box 111. For example, the pitch link 112 may be rotatably connected to a connecting shaft portion 16 that connects the bevel rotation gear 14 and the rotating body 15. For example, the pitch link 112 can include a first pitch link 1121 and a second pitch link 1122 that are disposed parallel to each other.

The translating link 114 can roll and pitch relative to the base B and translate along a virtual axis through a Remote Center of Motion (RCM). For example, translating link 114 may translate along guide 1152 located on parallel links 115. The translation link 114 is shown in fig. 1 simply, and various devices of a Remote Center of Motion (RCM) such as various surgical instruments (E) to be embodied may be provided in the translation link 114 as shown in fig. 2 and 3.

The parallel link 115 can move in a posture parallel to the longitudinal direction of the pitch link 112. Parallel links 115 may include a cross bar 1151 coupled to connecting bar 116; and a guide 1152 provided in a vertical direction of the cross bar 1151 for guiding the translation link 114.

A connecting rod 116 may connect pitch link 112 with parallel link 115. The connection rod 116 may be disposed parallel to a virtual line connecting the rotation axis of the first pitch link 1121 and the rotation axis of the second pitch link 1122. For example, the connecting bar 116 may include a first connecting bar 1161 and a second connecting bar 1162 that are parallel to each other. The pitch link 112 may be disposed parallel to a virtual line connecting the rotation axis of the first connection link 1161 and the rotation axis of the second connection link 1162.

Based on the above-described structure of the link assembly 11, the pitch link 112, the parallel link 115, and the link 116 can realize the motion of a parallelogram-like four-bar linkage (4-bar linkage). Therefore, as shown in fig. 2 and 3, the translation link 114 can perform translation along a virtual axis passing through the Remote Center of Motion (RCM) without being affected by the pitch rotation angle of the positioning arm 1. Also, when the roll rotation axis (axis 1) and the pitch rotation axis (axis 2) intersect at the same point, the translation link 114 can still perform translation along the same virtual axis passing through the Remote Center of Motion (RCM) without being affected by the roll rotation angle of the positioning arm 1.

The central bevel gear 13 is fixed to the bottom B so as not to rotate relative to the bottom B.

A pair of rotating bevel gears 14 may be engaged on both sides of the central bevel gear 13, respectively, and rotate with respect to a specific position of the gear box 111.

With the above configuration, the plurality of bevel gears 13 and 14 do not move relative to each other when the link assembly 11 rotates in a pitching manner (see fig. 5), and can rotate in mesh with each other when the link assembly 11 rotates in a rolling manner (see fig. 6 to 8). The plurality of bevel gears 13, 14 may have, for example, 1: a gear ratio of 1.

The rotating body 15 may be connected to one or more bevel gears 13 and 14 and rotate together with the bevel gears 13 and 14. For example, the pair of rotating bodies 15 may be fixed to the pair of rotating bevel gears 14, respectively, and may rotate together with the pair of rotating bevel gears 14 with respect to the gear case 11. The rotating body 15 may include a cam 151 and a connection port 152, wherein the cam 151 is fixed to the connection shaft 16 and rotates at the same angle as the corresponding rotary bevel gear 14; the connection port 152 is provided to the cam 151 so as to be rotatable, separately from the connection shaft portion 16. A compensating wire 174 described later can be connected to the connection port 152.

The connecting shaft portions 16 may be formed between the pair of rotary bevel gears 14 and the pair of rotary bodies 15 corresponding thereto, respectively, and the link assembly 11 may be provided on the connecting shaft portions 16 so as to be rotatable in one direction.

The gravity torque compensation portion 17 may provide a compensation torque in a direction opposite to that of the gravity torque at which the own weight of the link assembly 11 acts on a point. For example, the gravity torque compensation portion 17 may change the length of the elastic body 171 with the rolling rotation and/or the pitching rotation of the link assembly 11, thereby providing the compensation torque. For example, the gravity torque compensator 17 may include a pair of elastic bodies 171, a support platform 172, a pair of sliders 173, and a pair of compensating steel wires 174.

As shown, the pair of elastic bodies 171 may be compression springs, but are not necessarily limited thereto, and it should be understood that a person skilled in the art may use other known various elastic means than compression springs.

The support base 172 may be positioned at one side of the pair of elastic bodies 171 to support the ends of the pair of elastic bodies 171. The support base may include a support portion (1721, see fig. 12a and 12b) disposed on a side of a path through which the compensating wire 174 passes. The supporting portion 1721 functions to contact the compensating steel wire 174 to receive the compensating torque transmitted from the compensating steel wire 174. For example, the support 172 may be a roller, thereby not interfering with the movement of the compensating steel wire 174. On the one hand, the support platform 172 is slidable with respect to the pitch link 112, and thus can also interact with the gravity torque adjustment unit 18, which will be described later.

A pair of sliders 173 may be positioned at the other side of the pair of elastic bodies 171. In other words, the support base 172 and the slider 173 are located on both sides with respect to the elastic body 171. A pair of sliders 173 are slidable with respect to pitch links 112, respectively, so that the amount of deformation of elastic body 171 can be determined according to the change in the interval between support platform 172 and sliders 173, thereby changing the tension applied to compensating wire 174.

One side of each of the pair of compensating steel wires 174 may be fixed to the pair of rotating bodies 15, and the other side may be fixed to the pair of sliders 173. The positions of the pair of sliders 173 can be adjusted by interlocking the rotation angle of the rotating body 15 with the compensation steel wire 174. Also, compensator wire 174 may extend through brace table 172, whereby a portion of the tension applied to compensator wire 174 may provide a torque that rotates brace table 172 in the pitch direction. To summarize, the compensation torque provided by compensation wire 174 to support table 172 and pitch link 112 connected thereto may be varied depending on the distance between a pair of sliders 173 and support table 172.

The gravity torque adjustment part 18 may reduce a difference between the gravity torque and the compensation torque generated with the translation distance of the translation link 114. The gravitational torque adjustment portion 18 may reduce the elastic potential energy of the elastic body 171 when the translation link 114 translates toward the Remote Center of Motion (RCM) (i.e., when the moment of inertia of the link assembly 11 decreases); as the translating link 114 translates away from the Remote Center of Motion (RCM) (i.e., as the moment of inertia of the linkage assembly 11 increases), the elastic potential energy of the elastic body 171 increases. The gravity torque adjusting part 18 may include an adjusting wire 181 and a speed changing means 182.

An adjustment wire 181 may connect the translation linkage 114 to the support platform 172, whereby the support platform 172 may slide as the translation linkage 114 translates. For example, adjustment wire 181 can include a first adjustment wire 1811 connected between translation link 114 and shifting means 182; and a second adjusting wire 1812 connected between the speed changing means 182 and the support platform 172.

The speed changing means 182 is provided on the adjustment wire 181, and increases or decreases the sliding distance of the support platform 172 with respect to the pitch link 112 in proportion to the translational distance of the translational link 114 with respect to the parallel link 115. For example, the shifting means may include a first reel 1821 around which the first adjusting wire 1811 is wound; a second reel 1822 around which second adjusting wire 1812 is wound, and a decelerator 1823 that rotates second reel 1822 relative to first reel 1821 at a set rotation ratio.

As will be described later with reference to fig. 12a and 13, the set rotation ratio is set in consideration of a design specification such as an elastic modulus of the elastic body 171, and the difference between the gravitational torque and the compensation torque can be minimized.

Meanwhile, the positioning arm 1 may be used as a slave manipulator of a master-slave surgical system (master-slave). For example, the positioning arm 1 may further include a rolling rotation motor M _ r for rolling rotation of the link assembly 11; the pitching motor M _ p is used for pitching and rotating the connecting rod assembly 11; and a translation motor M _ t for translating the translation link 114.

For example, a rolling rotation motor M _ r may be connected to the base B to roll-rotate the gear box 111. The pitch rotation motor M _ p rotates together with the gear box 111, and can pitch-rotate the pitch link 112 with respect to the gear box 111. The translation motor M _ t may be mounted on the parallel link 115 and translate the translation link 114 with respect to the parallel link 115. For example, the parallel linkage 115 may include a helical shaft 1153 capable of moving the translating linkage 114 in a ball screw manner.

FIG. 5 is a diagram illustrating pitch rotation of a positioning arm according to an embodiment. For ease of understanding, the gearbox 111 is omitted from fig. 5.

Before the description, first, the coordinate systems described in all the drawings in the present specification will be described with reference to the coordinate system shown in fig. 5. First, the x0, y0, z0 coordinate system is a global coordinate system (global coordinate system) fixed to the bottom B. The x1, y1 and z1 coordinate system is a coordinate system which rotates the rolling rotation angle theta 1 by taking the z0 axis as a reference; the x2, y2, z2 coordinate system is a coordinate system of rotation pitch rotation angle θ 2 with reference to the y1 axis. The origin positions of the three coordinate systems are the centers of gravity of the rolling rotation and the pitching rotation of the link assembly 11. Thus, the x2, y2, z2 coordinate system may be understood as a local coordinate system (local coordinate system) fixed to the pitch link 112.

Referring to fig. 1 to 5, when the pitch link 112 is rotated in pitch by an angle θ 2 on the x1, y1, z1 coordinate system, that is, the pitch link 112 is rotated in pitch about the connecting shaft portion 16 of the pair of bevel gears 14 with respect to the gear box 111, the pair of rotating bevel gears 14 are engaged to the fixed central bevel gear 13, and thus relative movement does not occur.

As a result, when the link assembly 11 rotates in a pitching manner, the angle between the connection port 152 and the support base 172 increases as the angle between the rotating body 15 and the pitching link 112 increases. As a result, the slider 173 is pulled toward the support base 172 by the tension of the compensating wire 174, and as a result, the elastic body 171 is compressed, and the tension applied to the compensating wire 174 is increased by the elastic force of the elastic body 171. As previously mentioned, the tension applied to the compensating wire 174 may provide a compensating torque in the opposite direction to the gravitational torque caused by the own weight of the connecting rod assembly 11. The above-mentioned gravity compensation process according to the attitude change generated by the pitch rotation can refer to the existing research papers "Static balancing of a manipulator with a hybrid work space", Advanced Intelligent Mechanics (AIM), 2010IEEE/ASME International Conference ("Static balancing of a manipulator with a hemispherical working space", 2010IEEE/ASME Advanced Intelligent Mechatronics International Conference).

Fig. 6 to 8 are drawings showing a rolling rotation of a positioning arm according to an embodiment. Fig. 6 shows the respective rotation directions of the pair of rotary bevel gears 14 and the rotary body 15 when the link assembly 11 is rolled and rotated about the z1 axis, and fig. 7 and 8 show patterns that change when the link assembly 11 is actually rolled by the rotation angle θ 1.

Referring to fig. 6 to 8, when the gear box 111 is rotated in a rolling manner about the coupling shaft portion of the center bevel gear 13 with respect to the bottom portion B, the pair of rotary bevel gears 14 revolve (revolution) about the center axis z _0 which is the center shaft of the fixed center bevel gear 13 at the same rolling rotation angle θ 1 as the gear box 111. As a result, the pair of rotary bevel gears 14 rotate (rotation) in opposite directions by angles θ 1m and θ 2m, respectively, about the y _1 axis, which is the central axis of the pair of rotary bevel gears 14.

As a result, the rotating body 15 positioned on the left side in fig. 8 rotates to the right side in fig. 7, and as a result, the elastic potential energy of the elastic body 171 corresponding thereto changes, thereby changing the compensation torque T2 acting clockwise with respect to the z0 axis.

Similarly, the rotating body 15 positioned on the right side in fig. 8 rotates to the left side in fig. 7, and as a result, the elastic potential energy of the elastic body 171 corresponding thereto changes, thereby changing the compensation torque T1 acting counterclockwise with respect to the z0 axis.

In general, the total torque of the compensating torques T1 and T2 can compensate for the gravitational torque. The above-mentioned gravity compensation process according to the posture change generated by the rolling rotation can refer to the existing research papers "Static balancing of a manipulator with a tangential work space", Advanced Intelligent Mechanics (AIM), 2010IEEE/ASME International Conference ("Static balancing of a manipulator with a hemispherical working space", 2010IEEE/ASME Advanced Intelligent Mechatronics International Conference).

The principle of supplying the compensation torque according to the change in the roll rotation angle θ 1 and the pitch rotation angle θ 2 of the link assembly 11 is described above with reference to fig. 5 to 9. However, as shown in the embodiment of the figure, even if the roll rotation angle θ 1 and the pitch rotation angle θ 2 of the link assembly 11 do not change, when a part of the components (114: translation link) constituting the link assembly 11 relatively moves with respect to the other components, the arm length from the origin to the entire center of gravity of the link assembly 11 changes, and therefore, referring to the contents of the conventional research paper, the gravity torque based on the change cannot be compensated. Next, the gravity torque adjusting portion 18 capable of reducing the difference between the gravity torque and the compensation torque even in the above case will be described.

Fig. 9 and 10 are diagrams showing the operation of the gravity torque adjusting portion when the translation link translates according to the embodiment. Fig. 9 is a front view of a state in which a part of the positioning arm is configured in fig. 1, and fig. 10 is a drawing of a state in which the translation link is away from a remote Rotation Center (RCM) in the state of fig. 9.

Referring to fig. 9 and 10, the positioning arm 1 according to an embodiment has a structure in which the support platform 172 connected to the adjustment wire 181 slides in a direction away from the origin as the translation link 114 moves away from the Remote Center of Motion (RCM), that is, as the moment of inertia of the link assembly 11 with respect to the origin increases. This shortens the distance between the slider 173 and the support base 172, and as a result, the amount of deformation of the elastic body 171 increases. Further, a distance h from a point (a point where the roll rotation axis and the pitch rotation axis intersect) to the support portion (172, see fig. 2) increases by a distance corresponding to the rising distance of the support base 173. As the distance h increases, the arm length of the compensating torque provided by the compensating steel wire 174 to the connecting-rod assembly 11 increases. As a result, the compensation torque increases as the translation link 114 moves away from the Remote Center of Motion (RCM), and the gravity torque adjustment unit 18 can reduce the difference between the gravity torque and the compensation torque that changes as the translation link 114 translates.

According to the above-described embodiments, it is possible to provide compensation torques that vary in correspondence with variations in the roll rotation, pitch rotation, and translation, i.e., the gravitational torques of the three motions. Next, the effectiveness of the compensation torque generated according to the three motions will be theoretically described by a conceptual diagram, and further, the structure and/or conditions capable of more accurately compensating the change in the gravitational torque will be described.

FIG. 11 is a conceptual diagram of a positioning arm according to an embodiment. The gravity torque adjustment unit 18 is omitted in fig. 11.

Referring to fig. 11, the positioning arm 1 according to an embodiment may be shown by a model in which three mass bodies m1, m2, m3 connected in a mutually slidable manner move with respect to the origin O. At this time, (i) the first mass body m1 corresponds to the pitch link 112; (ii) the second mass body m2 corresponds to the parallel link 115, the connecting rod 116, the gravity torque compensation portion 17, and the gravity torque adjustment portion 18; (iii) the third mass m3 corresponds to the translation link 114. The gravity center distances of the three masses m1, m2 and m3 are l1, l2 and l3 respectively.

Also, the elastic body 171 is shown by a zero-length spring (zero-length spring) model, and the elastic modulus is k. It will be appreciated by those skilled in the art that the zero length spring model can be implemented in the manner of the previously illustrated embodiments.

In one aspect, h1, h, and b are defined as follows:

-h 1: the distance from the origin O to one end of the zero-length spring model in the x1-z1 plane coordinate system

-h: distance from origin O to the other end of the zero-length spring model in the x1-z1 plane coordinate system

-b: the distance from the other end of the zero-length spring model k to the second mass m2 in the x1-z1 plane coordinate system

Where h1 is a constant that is the same as the distance from the connecting shaft portion 16 to the connecting port 152. h is a variable that adds the translation distance of the support platform 172 relative to the pitch link 112 to the initial value h1 (Δ h — Δ l 2). b is a constant obtained by subtracting the variable h from the barycentric distance l2 of the second mass m 2.

First, in order to compensate for the gravitational torque at the time of pitch rotation, the sum of the overall potential energy of the positioning arm 1 should be a constant that is not affected by the pitch rotation angle θ 2. When the sum of the three masses m1, m2 and m3 is defined as m and the total gravity center distance of the three masses m1, m2 and m3 is defined as 1, the total potential energy of the positioning arm 1 is expressed as the sum of elastic potential energy and gravitational potential energy, as shown in the following formula 1.

Equation 1

It can be seen that it is first necessary to satisfy the first term of the result obtained by the arrangement of formula 1The conditions of (1). Taking the barycentric equation into the conditions, the following equation 2 is obtained.

Equation 2

As can be seen from equation 2, the change Δ l3 in the gravity center distance l3 of the third mass m3 should be proportional to the change in h (Δ h ═ Δ l2) defined above (Δ l ═ Δ l2)₂∝Δl₃). In other words, in the employed configuration, the translation distance of the translation link 114 with respect to the pitch link 112 is increased or decreased in proportion to the translation distance of the support base 172 with respect to the pitch link 112, and it is understood that the embodiment can satisfy the corresponding conditions.

Fig. 12a and 13 are drawings illustrating a gravity torque adjustment part according to an embodiment.

Referring to fig. 12a and 13, the gravitational torque according to the roll rotation angle θ _ r and the pitch rotation angle θ _ p is calculated by the following formula, and the elastic constant k of the elastic body 171 and the set rotation ratio (c) of the decelerator 1823 corresponding thereto can be determined as the deceleration ratio.

First, terms used for the respective formulas are as follows, and portions overlapping with the terms described above are omitted. On the one hand, in fig. 13 and the following formulas, M _1, M _2, M _3, M _4, and M _ b correspond to the pitch link 112, the connecting link 116, the parallel link 115, the translation link 114, and the support table 112, respectively, and H _ i is a height from the origin to the center of gravity of each of M _ i.

a_i：M_iAnd the distance between the center of mass and the center of rotation

h₁: arm of force of cone gravity compensation part (fixed)

h: arm of force of cone gravity compensation part (variation)

c: 1/(Transmission ratio)

d: translation length (0< d <150mm)

x: compression length of spring

θ_1m: angle of rotation of bevel gear (1)

θ_2m: angle of rotation of bevel gear (2)

k: elastic constant of gravity compensation part

τ_g,r: gravity torque (Rolling)

τ_g,p: gravity torque (pitching)

τ_k,r: compensation torque (Rolling)

τ_k,p: compensation torque (Pitch)

τ_r: total torque (Rolling)

τ_p: total torque (Pitch)

V_k(q): potential energy of gravity compensation part for q (1-degree of freedom)

V_k,total: total potential energy of the system

Next, an equation for calculating the gravitational torque from the roll rotation angle θ _ r and the pitch rotation angle θ _ p is as follows.

U_i＝M_iga_i

H_i＝a_icos(θ_r)cos(θ_p)

h＝h_init+c*d

θ_1m＝-θ_p-θ_r-π

θ_2m＝-θ_p+θ_r-π

x(q)＝h₁ ²+h²+2h₁h*cos(q)

V_k，total＝V_k(θ_1m)+V_k(θ_2m)

τ_r＝τ_g，r+τ_k，r＝0

τ_p＝τ_g，p+τ_k，p＝0

Through the above-described unwinding process, the elastic modulus of the elastic body 171 and the set rotation ratio of the decelerator 1823 are finally determined as follows.

As described above, by changing the elastic modulus of the elastic body 17 and/or the installation rotation ratio of the speed reducer 1823 according to other design specifications, the difference between the gravity torque and the compensation torque is reduced, and a more effective gravity compensation device can be provided.

While certain embodiments of the present invention have been illustrated and described, the present invention is not limited to the described embodiments. Rather, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.