Monitoring a kinematically redundant robot

Abstract

A method for monitoring a kinematically redundant robot includes detecting joint forces acting in the joints of the robot, determining an external work force between a robot-permanent reference point and an environment based on the detected joint forces, determining a further monitoring variable that is at least substantially independent of an external force acting on the robot-permanent reference point based on the detected joint forces, and monitoring the determined external work force and the determined further monitoring variable.

Claims

1. A method for monitoring a kinematically redundant robot, the method comprising: detecting joint forces acting in joints of the robot; determining an external work force between a robot-permanent reference point and an environment based on the detected joint forces; determining, based on the detected joint forces, a further monitoring variable which is at least substantially independent of an external force acting on the robot-permanent reference point; monitoring the determined external work force and the determined further monitoring variable; and controlling the robot with a controller based on at least one of the determined external work force or the determined further monitoring variable.

2. The method of claim 1, further comprising: triggering a first safety reaction when the determined external work force fulfills a first variably definable monitoring condition; and triggering the first safety reaction or a second safety reaction when the determined further monitoring variable fulfills the first monitoring condition or a second monitoring condition.

3. The method of claim 2, wherein the second monitoring condition is a variably pre-definable monitoring condition.

4. The method of claim 1, wherein the further monitoring variable comprises an external force spaced apart from the robot-permanent reference point.

5. The method of claim 2, wherein the further monitoring variable comprises an external force spaced apart from the robot-permanent reference point.

6. The method of claim 1, wherein the joint forces are mapped onto the external work force by a first linear mapping.

7. The method of claim 2, wherein the joint forces are mapped onto the external work force by a first linear mapping.

8. The method of claim 4, wherein the joint forces are mapped onto the external work force by a first linear mapping.

9. The method of claim 5, wherein the joint forces are mapped onto the external work force by a first linear mapping.

10. The method of claim 6, wherein the first linear mapping is a pseudoinverse of a transposed Jacobian matrix for the robot-permanent reference point.

11. The method of claim 7, wherein the first linear mapping is a pseudoinverse of a transposed Jacobian matrix for the robot-permanent reference point.

12. The method of claim 8, wherein the first linear mapping is a pseudoinverse of a transposed Jacobian matrix for the robot-permanent reference point.

13. The method of claim 9, wherein the first linear mapping is a pseudoinverse of a transposed Jacobian matrix for the robot-permanent reference point.

14. The method of claim 10, wherein the same joint forces are mapped onto the further monitoring variable by a second linear mapping.

15. The method of claim 11, wherein the same joint forces are mapped onto the further monitoring variable by a second linear mapping.

16. The method of claim 12, wherein the same joint forces are mapped onto the further monitoring variable by a second linear mapping.

17. The method of claim 13, wherein the same joint forces are mapped onto the further monitoring variable by a second linear mapping.

18. A method for monitoring a kinematically redundant robot, the method comprising: detecting joint forces acting in joints of the robot; determining an external work force between a robot-permanent reference point and an environment based on the detected joint forces; determining, based on the detected joint forces, a further monitoring variable which is at least substantially independent of an external force acting on the robot-permanent reference point; and monitoring the determined external work force and the determined further monitoring variable; wherein the joint forces are mapped onto the external work force by a first linear mapping; wherein the first linear mapping is a pseudoinverse of a transposed Jacobian matrix for the robot-permanent reference point; wherein the same joint forces are mapped onto the further monitoring variable by a second linear mapping; and wherein the second linear mapping is a null space projection operator of the pseudoinverse of the transposed Jacobian matrix for the robot-permanent reference point.

19. A computer program product, comprising: a non-transitory computer readable storage medium; and a program stored on the non-transitory computer readable storage medium that, when executed by a processing unit, causes the processing unit to: detect joint forces acting in joints of a kinematically redundant robot, determine an external work force between a robot-permanent reference point and an environment based on the detected joint forces, determine, based on the detected joint forces, a further monitoring variable which is at least substantially independent of an external force acting on the robot-permanent reference point, monitor the determined external work force and the determined further monitoring variable, and control the robot based on at least one of the determined external work force or the determined further monitoring variable.

20. A robot, comprising: a plurality of joints; and a control configured for executing the method of claim 1, the control comprising: a detection means for detecting joint forces, a processing means for determining the external work force and further monitoring variable, and a monitoring means for monitoring the determined external work force and the determined further monitoring variable.

21. The robot of claim 20, comprising at least seven joints.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further advantages and features can be derived from the dependent claims and the embodiment examples. For this, shown are, in part schematically:

(2) FIG. 1: a robot according to one embodiment of the present invention; and

(3) FIG. 2: a method according to one embodiment of the present invention.

DETAILED DESCRIPTION

(4) FIG. 1 shows a kinematically redundant seven-axis lightweight robot 1 according to one embodiment of the present invention, having seven joints, exhibiting the joint angles q.sub.1−q.sub.7=q, a TCP on a tool (flange) and a control means 2, which executes a process according to one embodiment of the present invention, which shall be explained in greater detail below with reference to FIG. 2.

(5) In a step S10, joint torques τ.sub.1−τ.sub.7=τ are detected by means of joint torque sensors 1.1-1.7 of a detection means in the control means 2 for detecting joint forces. From these, in a step S20, model-based externally induced joint forces {circumflex over (T)}.sub.e are evaluated by a processing means 2.1 in the control means 2, in that tractive, gravitational, drive, and similar, robot-internal components are subtracted from the detected joint forces τ.

(6) In a step S30, the externally induced joint forces {circumflex over (T)}.sub.e determined in this manner are mapped on the external work force by multiplication with the pseudoinverse of the transposed Jacobian matrix of the TCP weighted with the mass matrix M of the robot 1:
{circumflex over (f)}.sub.W=(J.sup.T).sup.#.Math.{circumflex over (T)}.sub.e

(7) In a step S40, a further monitoring variable is determined in advance, parallel to, or subsequently, by means of the processing means, from the externally induced joint forces {circumflex over (T)}.sub.e by multiplication with the null space projection operator of this transposed Jacobian matrix:
{circumflex over (τ)}.sub.NS=└I−J.sup.T.Math.(J.sup.T).sup.#┘.Math.{circumflex over (τ)}.sub.e

(8) In steps S50, S60, a monitoring of whether a quantity for the work force (step S50) or the further monitoring variable (step S60) exceeds a given threshold value f.sub.1 or f.sub.2, respectively, is carried out by means of a monitoring means 2.2 in the control means 2. If this is the case (“Y” in step S50, or S60, respectively), a STOP 1 (when the threshold value f.sub.1 is exceeded by the work force), or a STOP 0 (when the threshold value f.sub.2 is exceeded by the further monitoring variable), is triggered. Processing and monitoring means can be implemented, in particular, by a computer configured accordingly in terms of its programming.

LIST OF REFERENCE SYMBOLS

(9) 1 redundant robot 1.1-1.7 joint force sensors (detection means) 2 control means 2.1 processing means 2.2 monitoring means q.sub.1-q.sub.7 joint angles (minimum coordinates) TCP Tool Center Point (robot-permanent reference point)