METHOD AND SYSTEM FOR PERFORMING A PREDETERMINED TASK USING A ROBOT

Abstract

A method for carrying out a predetermined task using a robot, which is redundant with regard to the task. When the task is carried out, an admittance motion that is dependent on a force exerted externally on the robot and on a predetermined virtual mass, stiffness and/or damping is carried out in the zero space.

Claims

1-9. (canceled)

10. A method for carrying out a predetermined task using a robot, wherein the robot is redundant with regard to the task, the method comprising: executing the task by actuating at least one joint of the robot, while performing an admittance motion in the zero space of the robot in response to the command; wherein the admittance motion is based on a force exerted externally on the robot and at least one of a predetermined virtual mass, a predetermined virtual stiffness, or a predetermined virtual damping associated with the robot.

11. The method of claim 10, further comprising: determining the force exerted externally on the robot based on at least one of forces in the joints of the robot or a model of the robot.

12. The method of claim 10, wherein at least one of: the task is predetermined in the workspace of the robot; or the task comprises at least one of: at least one pose of the robot, or at least one change of pose of a robot-fixed reference.

13. The method according of claim 12, wherein at least one of: the robot-fixed reference is arranged on a robot-guided tool; or at least one of the tool center point (TCP) of the robot or a target task motion is determined on the basis of the predetermined task.

14. The method of claim 13, wherein at least one of: the robot-fixed reference is arranged on the robot-guided tool between a tool tip and a robot end flange; the target task motion is in the joint coordinate space of the robot; or the TCP of the robot or the target task motion is determined on the basis of the Jacobian matrix of the predetermined task.

15. The method of claim 10, wherein: a target admittance motion is determined on the basis of at least one of: the force exerted externally on the robot, or at least one of a predetermined virtual mass, stiffness, or damping; and the determined target admittance motion is projected into the zero space.

16. The method of claim 15, wherein the target admittance motion is at least one of: in the joint coordinate space of the robot; or performed with the aid of an admittance control.

17. The method of claim 13, further comprising: controlling motion of at least one joint of the robot using at least one of velocity control or position control; wherein the velocity control or the position control is based on at least one of: the target task motion, or the target admittance motion projected into the zero space.

18. The method of claim 15, further comprising: controlling motion of at least one joint of the robot using at least one of velocity control or position control; wherein the velocity control or the position control is based on the target admittance motion projected into the zero space.

19. The method of claim 10, wherein executing the predetermined task comprises guiding a medical tool with the robot.

20. A system for operating a robot to carry out a predetermined task, wherein the robot is redundant with regard to the task, the system comprising: means for executing the task while performing an admittance motion in the zero space of the robot; wherein the admittance motion is based on a force exerted externally on the robot and at least one of a predetermined virtual mass, a predetermined virtual stiffness, or a predetermined virtual damping associated with the robot.

21. A computer program product for carrying out a predetermined task using a robot, wherein the robot is redundant with regard to the task, the computer program product comprising program code stored on a non-transient computer-readable medium, the program code, when executed on a computer, causing the computer to: execute the predetermined task by actuating at least one joint of the robot; and perform an admittance motion in the zero space of the robot while executing the predetermined task; wherein the admittance motion is based on a force exerted externally on the robot and at least one of a predetermined virtual mass, a predetermined virtual stiffness, or a predetermined virtual damping associated with the robot.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention.

[0044] FIG. 1 illustrates a system for operating a robot or for carrying out a predetermined task using the robot according to an embodiment of the present invention; and

[0045] FIG. 2 illustrates a method for carrying out the task using the robot according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0046] FIG. 1 shows a system with a controller 2 for controlling or regulating a seven-axis robot 10 or for carrying out a predetermined task using the robot 10 according to an embodiment of the present invention, and FIG. 2 shows a method for carrying out the task using the robot according to an embodiment of the present invention.

[0047] The robot 10 guides a tool 12 which is fastened to the robot end flange 11 and comprises a distal tool tip 13.

[0048] A predetermined task is, for example, to keep the three-dimensional Cartesian position of the tool-fixed point X constant. Another predefined task can be, for example, a predefined TCP pose or TCP path.

[0049] In a first step S10, the controller 2 determines forces, in particular torques Ti about the (rotational) axes, in the joints of the robot, for example by means of force, in particular torque sensors in the joints (not shown).

[0050] In a second step S20, the controller 2 uses this to determine a force Text exerted externally on the robot, for example according to Eq. (6) or in another way.

[0051] In a third step S30, the controller 2 determines a target admittance motion {dot over (q)}.sub.a or {umlaut over (q)}.sub.a on the basis of this force Text exerted externally on the robot and a predetermined virtual mass M and damping D, with the aid of an admittance control, for example according to Eq. (5), (5′) with K=0 or in another way.

[0052] In a fourth step S40, the controller 2 projects this target admittance motion into the zero space of the task, adds a task target motion that it determines on the basis of the generalized or pseudo inverse of the Jacobian matrix of the predetermined task, for example according to Eq. (7) or in another way, and feeds the resulting or according to Eq. (8) determined target motion ad, possibly after integration into a target position q.sub.d in the joint coordinate space, to a velocity or position control, which commands the corresponding joint angle or controls drives of the robot 10 (not shown) accordingly.

[0053] As a result, when carrying out the task in the zero space, the robot 10 carries out an admittance motion {dot over (q)}.sub.a that is dependent on the force exerted externally on the robot and on the predetermined virtual mass and damping.

[0054] Although embodiments have been explained in the preceding description, it is noted that a large number of modifications are possible. It is also noted that the embodiments are merely examples that are not intended to restrict the scope of protection, the applications and the structure in any way. Rather, the preceding description provides a person skilled in the art with guidelines for implementing at least one embodiment, with various changes, in particular with regard to the function and arrangement of the described components, being able to be made without departing from the scope of protection as it arises from the claims and from these equivalent combinations of features.

[0055] While the present invention has been illustrated by a description of various embodiments, and while these embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such de-tail. The various features shown and described herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without