阅读说明：本技术 控制机器人的方法和系统 (Method and system for controlling robot ) 是由 S·夏尔玛 于 2019-01-16 设计创作，主要内容包括：根据本发明的一种用于根据施加在机器人(10)上的外部的力(F<Sub>ex</Sub>)来控制该机器人的方法,在第一运行模式下,根据表面(21)控制(S50)机器人,使得机器人在特定于机器人的参照物(11)与表面的接触点上,相比于跟随力的沿表面法线方向的法向分量(F<Sub>n</Sub>),更强烈地试图跟随该力的垂直于关于表面向外指向的法线(n)的切向分量(F<Sub>t</Sub>)。(The invention relates to a method for determining an external force (F) exerted on a robot (10) ex ) Method for controlling the robot, in a first mode of operation, the robot being controlled (S50) in dependence on a surface (21) such that the robot has a normal component (F) in the direction of the surface normal in comparison to a follow-up force at a contact point of a reference object (11) specific to the robot with the surface n ) More strongly, it is attempted to follow the tangential component (F) of the force perpendicular to the normal (n) pointing outwards with respect to the surface t )。)

1. For according to application inExternal forces (F) on the robot (10)_ex) Method for controlling the robot, wherein in a first mode of operation the robot is controlled (S50) in dependence on a surface (21) such that the robot has a normal component (F) of the force in the direction of the surface normal compared to the normal component (F) of the force at the point of contact of a robot-specific reference object (11) with the surface_n) More strongly trying to follow a tangential component (F) of the force perpendicular to a normal (n) pointing outwards with respect to the surface_t)。

2. A method according to claim 1, characterized by controlling the robot in the first mode of operation such that the robot does not attempt to follow the normal component of the force.

3. Method according to any of the preceding claims, characterized in that in a second operation mode the robot is controlled (S40) such that it follows the normal component of the force more strongly than in the first operation mode.

4. Method according to any of the preceding claims, characterized in that the switching from the first to the second operation mode (S20) is performed depending on the normal component of the force and/or the robot is controlled in the second operation mode such that the robot tries to follow the force independently of its direction.

5. A method according to any of the preceding claims, characterized by controlling the robot in the first mode of operation such that the robot tries to exert a predetermined force against the surface normal with the robot-specific reference object on the surface.

6. Method according to any one of the preceding claims, characterized in that switching to the first operating mode is performed depending on the determined distance, in particular contact, between the robot-specific reference object and the surface and/or depending on a user input.

7. Method according to any of the preceding claims, characterized in that the external force is determined by means of sensors (12) on the robot-specific reference object and/or sensors (12') on the joints of the robot.

8. Method according to any of the preceding claims, characterized in that the surface normal is determined from the determined or pre-given contour of the surface.

9. Method according to any of the preceding claims, characterized in that the contact point is determined from the detected position of the joints of the robot, the determined or predefined contour of the robot-specific reference object and/or the determined or predefined contour of the surface and/or the detection of the surroundings of the robot-specific reference object.

10. Method according to any of the preceding claims, characterized in that in the first and/or second operating mode the robot is controlled by means of an admittance adjustment, which determines a control value for a drive (13) of the robot depending on the determined external force.

11. Method according to one of the preceding claims, characterized in that in the first operating mode the normal component is computationally reduced, in particular attenuated.

12. System designed for carrying out the method according to any one of the preceding claims and/or having means for determining the external force (F) exerted on the robot (10) _ex) Controlling means (30) of the robot (10) in a first operating mode as a function of the surface (21) such that the robot is specific to the surfaceA normal component (F) of the reference object (11) of the robot in the direction of the surface normal compared to the force at the point of contact with the surface_n) More strongly trying to follow the tangential component (F) of the force perpendicular to the direction of the normal (n) pointing outwards with respect to the surface_t)。

13. A computer program product comprising program code stored on a medium readable by a computer, for performing the method according to any one of claims 1 to 11.

Technical Field

The invention relates to a method and a system for controlling a robot as a function of external forces exerted on the robot, and a computer program product for carrying out the method.

Background

An admittance adjustment for controlling a robot is known from the patent document US9308645B 2. In this case, the control system determines a target movement, which is to be achieved by a virtual mass under the external force, based on the external force exerted on the robot, and the robot attempts to execute the target movement. In other words, the end effector of the robot behaves like the virtual mass itself.

This enables the operator to perform an advantageous manual guidance of the (freely) movable end-effector by manually applying an external force on the robot.

However, if the end effector contacts the surface there, inadvertent lifting of the end effector from the surface may occur, particularly due to imprecise adjustment, and the like.

Disclosure of Invention

The object of the invention is to improve the operation of a robot.

The object of the invention is achieved by a method having the features of claim 1. Claims 12 and 13 claim a system or a computer program product for performing the method described herein. Preferred developments are given by the dependent claims.

According to one embodiment of the invention, in a method for controlling a robot as a function of an external force exerted on the robot, in particular a current external force, the robot is controlled in a first operating mode, in particular continuously, as a function of a surface in such a way or according to such a criterion: that is, having the robot at the, in particular, current, contact point of the robot-specific reference object with the surface more strongly tries to follow, in particular more strongly follows, the tangential component of the force perpendicular to the normal pointing outwards with respect to the surface than the normal component of the force in the direction of the surface normal; in particular, the robot is controlled in this way or according to the following criteria: i.e. such that the robot does not try to follow, at least substantially does not try to follow, in particular does not follow, the normal component of the force. In other words, the robot is controlled in the first mode of operation to (so as to) follow the normal component (slightly) less than the tangential component, in one embodiment not follow the normal component at all.

Thus, undesired lifting from the contacted surface may be reduced in one embodiment, and undesired lifting from the contacted surface may be at least substantially avoided in one embodiment.

In one embodiment, the control can comprise, in particular can be, an adjustment. In one embodiment, the force may also comprise, in particular may be, a torque.

In one embodiment, the robot has at least three joints, in particular at least six joints, in one embodiment at least seven joints, in particular joints that can be driven or driven and/or revolute joints, i.e. in one embodiment the robot has a drive, in particular an electric drive, for adjusting the joints.

In one embodiment, the robot can thus be used advantageously, in particular flexibly and/or precisely.

In one embodiment, the robot-specific reference object is a distal end effector of the robot. In one embodiment, the external force is an external force which is exerted manually by the operator or is exerted on the robot, in one embodiment on a reference object of the robot which is specific to the robot, or is an external force which is exerted manually by the operator. In one embodiment, the external force is a force acting on the contact point, which can be (virtually) transformed or moved there in a known manner, for example by means of a jacobian matrix.

Thus, in one embodiment the robot may advantageously be guided manually, in one embodiment for teaching or setting a trajectory or the like to be followed automatically.

In one embodiment, the normal pointing outwards with respect to the surface at the contact point ("surface normal"), which is perpendicular to the tangential plane of the surface at the contact point (on) and points away from the surface or to a robot-specific reference, can be made, for example, in a known manner, by means of differential geometry methodsThe gradient of the respective orientation or the cross-product of the respective orientation of the two non-collinear tangential vectors of the surface (on) at the contact point is determined, and the gradient or cross-product itself can be determined, for example, by differentiation in a known manner. For example, a surface or its contour is represented by cartesian coordinates x, y and z, for example x, if the function S (x, y, z) ═ 0²+y²+z²A sphere is denoted by 0, the surface normal n at the point of contact (x, y, z) is based onIs determined, for example, according to [ x, y, z ]]^TTo be determined. In other words, in one embodiment, in the first mode of operation, the robot follows the projection of the external force in the tangential plane of the surface (on) at the point of contact more strongly than it follows the projection of the external force in the direction of the outwardly directed surface normal, or tries to do so, or is (correspondingly) controlled for this purpose; in one embodiment, the robot does not follow the projection of the external force in the direction of the outwardly directed surface normal at least substantially at all, or tries to do so, or is (correspondingly) controlled for this purpose.

In one embodiment, the robot is controlled in the second operating mode, in particular continuously, in such a way or according to such a criterion: that is, the robot tries to follow, in particular follows the normal component of the external force more strongly than in the first mode of operation; in particular, it is controlled in this way or according to the following criteria: that is, the robot tries to follow, in particular to follow, the force independently of the direction of the force. In other words, the robot is controlled in the second operating mode to (slightly) follow the external force (so) independently of the direction.

In this way, in one embodiment, the robot-specific reference object can be moved intentionally away from the surface and/or advantageously freely in space in the second operating mode.

In one embodiment, switching from the first mode of operation to the second mode of operation is based on a normal component of the force; in one embodiment, the first operating mode is switched to the second operating mode if the value of the normal component exceeds a predetermined threshold value.

Thus, in one embodiment, the operator may simply end the first mode of operation, and in particular may cause the robot-specific reference to move off the surface by pulling the robot-specific reference sufficiently hard off the surface.

Additionally or alternatively, the switch from the first mode of operation to the second mode of operation may also be based on operator input, such as an operator manipulating a corresponding physical or software switch or the like.

In one embodiment, the robot is controlled in the first operating mode in such a way or according to such criteria: that is, the robot attempts to apply a predetermined force against the surface normal with a reference object specific to the robot. In other words, the robot is controlled in the first mode of operation to (in order to) exert a predetermined force on the surface opposite to the surface normal.

Thus, in one embodiment, the robot-specific reference object can be advantageously fixed on the surface by means of control techniques and/or can exert the desired process forces, for example for machining the surface.

In one embodiment, the switching to the first operating mode takes place as a function of the determined distance between the robot-specific reference object and the surface, in particular below a predetermined minimum distance; in one embodiment, the switching to the first operating mode takes place when contact occurs.

Thus, in one embodiment, the operator can easily initiate the first mode of operation by drawing the robot-specific reference object sufficiently close to the surface.

Additionally or alternatively, the switching to the first mode of operation may also be based on operator input, such as an operator manipulating a corresponding physical or software switch or the like.

In one embodiment, the external force is determined by means of a sensor on a robot-specific reference object.

In one embodiment, the external force can thus be determined particularly precisely.

Additionally or alternatively, in an embodiment, the external force is determined by means of sensors on the robot joints, in particular based on a dynamic model of the robot.

Thus, in one embodiment, an additional sensor on the robot-specific reference object may be omitted.

In one embodiment, the surface normal is determined from the determined surface profile, which in one embodiment is determined by means of scanning, a vision system, or the like.

In one embodiment, the surface normal can thus be determined particularly precisely.

Additionally or alternatively, in one embodiment, the surface normal is determined from a predefined surface profile, which in one embodiment is predefined based on CAD data or the like.

Thus, in one embodiment, the time cost and/or equipment cost for determining the contour may be omitted.

In one embodiment, the contact point is determined from a detection of the surroundings of the robot-specific reference object, which detection is performed in one embodiment by means of scanning, a vision system or the like.

In one embodiment, the contact point can thus be determined particularly precisely.

Additionally or alternatively, in one embodiment, the contact point is determined as a function of the detected position of the robot joint, the determined or predefined contour of the robot-specific reference object and/or the determined or predefined contour of the surface.

Thus, in one embodiment, the time cost and/or equipment cost for detecting the surroundings can be omitted.

In one embodiment, in the first and/or second operating mode, the robot is controlled by means of an admittance adjustment, which determines a control value for a drive of the robot as a function of the determined external force.

In one embodiment, the robot can thus be guided manually particularly advantageously, in particular intuitively, reliably and/or precisely.

In one embodiment, in the first operating mode, the normal component of the determined external force in the direction of the surface normal is reduced, in particular attenuated or filtered out, by computational techniques.

In this way, in particular by means of admittance adjustment, a weak or no following of the normal component according to the invention can be achieved particularly advantageously, in particular reliably, and/or with very low computational (time) costs.

According to one embodiment of the invention, a system is designed, in particular by hardware and/or software technology, in particular programming technology, for carrying out the method described here, and/or comprises means for controlling the robot in a first operating mode in dependence on the surface in dependence on an external force exerted on the robot, such that the robot, at a contact point of a robot-specific reference object with the surface, attempts to follow a tangential component of the force perpendicular to a normal pointing outwards with respect to the surface more strongly than a normal component of the force in the direction of the surface normal, in particular does not attempt to follow the normal component of the force.

In one embodiment, the system or apparatus thereof comprises:

means for controlling the robot in the second mode of operation such that the robot more strongly attempts to follow the normal component of the force than in the first mode of operation, in particular such that the robot attempts to follow an external force independently of its direction;

Means for switching from a first mode of operation to a second mode of operation in dependence on a normal component of the force;

means for controlling the robot in a first mode of operation such that the robot attempts to apply a predetermined force on the surface opposite the surface normal with a reference object specific to the robot;

means for switching to a first operating mode depending on the determined distance, in particular contact, between the robot-specific reference object and the surface and/or depending on a user input;

sensors located on robot-specific reference objects and/or sensors located on joints of the robot for determining external forces;

means for determining a surface normal from the determined or predetermined profile of the surface;

means for determining a contact point based on the detected position of the joints of the robot, the determined or predetermined contour of the robot-specific reference object and/or the determined or predetermined contour of the surface and/or the detection of the surroundings of the robot-specific reference object;

means for controlling the robot in the first and/or second operating mode by means of admittance adjustment, which is determining control values for the drives of the robot in dependence of the determined external force; and/or

Means for reducing, in particular attenuating, the normal component in the first operating mode by means of computational techniques.

The device according to the invention can be implemented by hardware and/or software, and in particular has: a processing unit, in particular a digital processing unit, in particular a micro processing unit (CPU), preferably in data connection or signal connection with a memory system and/or a bus system; and/or one or more programs or program modules. To this end, the CPU may be designed to: executing instructions implemented as a program stored in a storage system; collecting an input signal from a data bus; and/or send output signals to a data bus. The storage system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state and/or other non-volatile media. The program may be designed to embody or to carry out the method described herein, so that the CPU is able to carry out the steps of the method and thus, in particular, to control the robot. In one embodiment, the computer program product may have a storage medium, in particular a non-volatile storage medium, on which a program is stored or on which a program is stored, in particular a storage medium, in particular a non-volatile storage medium, on which a program is stored or on which a program is stored, wherein execution of the program causes a system or a controller, in particular a computer, to carry out the method or one or more steps of the method described herein.

In one embodiment, one or more, in particular all, steps of the method are performed fully or partially automatically, in particular by the system or a device thereof.

In one embodiment, the system has a robot and/or a controller thereof.

The method according to the invention can be used particularly advantageously for teaching or setting a robot trajectory, in particular by manual guidance of the robot, in particular of a robot-specific reference object. Accordingly, in one embodiment, in the first operating mode, at least temporarily, the pose of the robot, in particular of the robot-specific reference object, is stored, and in one development the robot trajectory is subsequently predefined on the basis of the stored pose.

Drawings

Further advantages and features are given by the dependent claims and embodiments. To this end, parts are schematically shown:

FIG. 1: a system according to an embodiment of the invention; and

FIG. 2: a method for controlling a robot of a system according to one embodiment of the invention.

Detailed Description

Fig. 1 shows a system according to an embodiment of the invention with a robot 10 having an end effector 11 and a robot controller 30.

The end effector 11 is manually guided on the surface 21 of the workpiece 20 by an operator 40, for example for teaching a machining trajectory.

To this end, in a first step S10 (see fig. 2) of the method for controlling the robot 10 according to an embodiment of the invention, the external force F manually applied by the operator 40 is determined by means of the force-torque sensor 12 on the end effector 11_ex。

In a variant, the robot controller may also be assisted by sensors on the robot jointsAnd 12' to determine the external force. In general, in one embodiment, a (transformed) jacobian matrix J of an end effector or tip thereof may be utilized^TFor the axial torque tau measured on the joint by means of a sensor_msrIn particular, the commanded axial torque τ calculated from a robot-based, optionally inverse dynamic model_(c)mdIs transformed to determine the external force F_ex：

F_ex＝J^T∙(τ_msr-τ_(c)md)

The basis of this concept is: the deviation between the model-based shaft moment and the measured shaft moment is precisely caused by the external force, so that the external force can be determined by converting the corresponding shaft moment into the working space of the robot (end effector).

The contour of the surface 21 is known, for example from CAD data, or determined by means of a camera 31.

In step S10, robot controller 30 checks whether the first operating mode is (has been or is still) selected, for example, by the operator manipulating a corresponding switch.

If this is not the case (S10: NO), then a second mode of operation exists and the robot controller or the method continues to step S40.

In step S40, the robot controller performs admittance adjustment, where the robot controller is based on the external force F on the tip of the end effector 11 in a known manner_exTo determine the target speed V_dFor example by time integration according to:

V_d＝∫(F_ex/m)dt

where m is the virtual mass and the robot's drive 13 is operated to achieve the target velocity V_d. In a variant, virtual damping may also be provided.

If the first operation mode is selected (S10: "Y"), the robot controller 30 determines to be perpendicular to the surface 21 at the contact point of the tip of the end effector 11 and the surface 21 according to the following equation based on the positions of the joints of the robot and the contour of the surface 21 in step S20The outwardly pointing surface normal n (| n | ═ 1) of the surface 21 and the external forces F acting there_exA normal component F in the direction of the surface normal n_n

F_n＝{[(F_ex·n)+|F_ex·n|]/2}·n

And checking the normal component F _nValue of | F_nIf | exceeds a predetermined boundary value.

If this is the case (S20: YES), the robot controller switches to the second mode of operation and continues with step S40 described above.

If not (S20: NO), i.e. if the first operation mode is (still) selected or present, the robot controller controls the robot by applying an external force F in step S30_exThe normal component is computationally attenuated by subtracting the normal component:

F_ex←(F_ex-F_n)。

in other words, in step S30, the robot controller filters out the external force F_exNormal component F in the direction of surface normal n_n。

Subsequently, in step S50, the robot controller performs admittance adjustment using the filtered external force, in this embodiment, for example, according to the filtered external force, in a manner similar to step S40

V_d＝∫(F_ex/m)dt

Subsequently, the method returns to step S10.

As a result, the robot 10 does not follow the external force F manually applied by the operator 40 with its end effector 11 in the first operation mode_exNormal component F of_nAnd therefore more strongly follow the tangential component F_t＝F_ex-(F_exN) n, or trying to adjust the technology. On the other hand, in the second operating mode, the robot 10 follows the external force F with its end effector 11 independently of its direction _exOr attempt to adjust the technology to do so.

Although exemplary embodiments have been set forth in the foregoing description, it should be noted that many variations are possible.

In one variation, in step S50, instead of the normal component F in the direction of the surface normal, a normal component F is substituted_nAlternatively, the external force F may be applied_exI.e. independently of the direction, or only the aforementioned tangential component F_tThe external force after filtration is considered. In addition or alternatively, it is also possible to set the technical force f exerted on the surface in a predetermined manner counter to the surface normal_cmdFor example, by adding it to the filtered external force in step S50:

F_ex←(F_ex-F_n)-f_cmdn or F_ex←F_t-f_cmd·n。

It should also be noted that the exemplary embodiments are only examples, and should not be construed as limiting the scope, applicability, or configuration in any way. Rather, the foregoing description will enable one skilled in the art to practice the teachings of the conversion to at least one exemplary embodiment, wherein various changes, particularly in matters of function and arrangement of parts described herein may be made without departing from the scope of the present invention, such as may be found in the claims and the equivalents thereof.

List of reference numerals

10 robot

11 end effector (reference object special for robot)

12; 12' sensor

13 driver

20 workpiece

21 surface of

30 robot controller

31 Camera

40 operator

F_exExternal force

F_nNormal component

F_tTangential component

n surface normal.