FORCE LIMITATION IN THE EVENT OF COLLISION OF A ROBOT MANIPULATOR

Abstract

A method of operating a robot manipulator, the method including: specifying a maximum permissible force to be exerted on an object by the robot manipulator, specifying a target position of a reference point of the robot manipulator, determining a current position of the reference point, performing an impedance regulation, which determines a current reference force of an artificial spring component based on a spring stiffness and based on a difference between the current position and the target position of the reference point of the robot manipulator, and controlling the robot manipulator to execute an emergency control program if the current reference force exceeds the maximum permissible force.

Claims

1. A method of operating a robot manipulator the method comprising: specifying a maximum permissible force to be exerted by the robot manipulator on an object in a vicinity of the robot manipulator; specifying a target position of a reference point of the robot manipulator; determining a current position of the reference point of the robot manipulator; controlling the robot manipulator by performing an impedance regulation, wherein the impedance regulation has an artificial spring component, and a current reference force of the artificial spring component is determined based on a specified spring stiffness and based on a difference between the current position and the target position of the reference point of the robot manipulator; and controlling the robot manipulator to execute an emergency control program if the current reference force exceeds the maximum permissible force.

2. The method of claim 1, wherein the emergency control program includes at least one of the following control programs: stopping the robot manipulator, moving the robot manipulator back to its original path, and switching to an alternative regulation mode.

3. The method of claim 1, wherein specifying the maximum permissible force is comprises detecting an input of a user at a user interface.

4. The method of claim 1, wherein specifying the maximum permissible force comprises using a database, wherein a plurality of body zones of a person with a respective associated maximum permissible force with respect to one of the body zones is stored in the database.

5. The method of claim 4, wherein specifying the maximum permissible force comprises: performing camera-based detection of a collision between a specific body zone of the person and the robot manipulator; and selecting the maximum permissible force from the database based on the detection of the collision between the specific body zone of the person and the robot manipulator, wherein the specific body zone of the person is assigned to a body zone stored in the database and a maximum permissible force associated with the body zone assigned is selected as the maximum permissible force.

6. The method of claim 4, wherein the method comprises adapting maximum permissible forces stored in the database or one selected from the maximum permissible forces depending on an edge geometry of the robot manipulator and/or a task or task class to be performed by the robot manipulator.

7. The method of claim 1, wherein specifying the target position comprises specifying a desired path of the reference point of the robot manipulator.

8. The method of claim 1, wherein determining the current position of the reference point of the robot manipulator is based on redundant sensor signals.

9. The method of claim 1, wherein the target position of the reference point of the robot manipulator is specified behind a surface of the object, such that the robot manipulator exerts a force on the surface of the object in a direction of the target position.

10. (canceled)

11. The method of claim 2, wherein the alternative regulation mode is an admittance regulation mode and/or a gravitational force-compensated mode, and the switching to the alternative regulation mode includes ending all movement and/or force commands.

12. A robot system comprising: a robot manipulator; and a control unit connected to the robot manipulator, the control unit configured to: specify a maximum permissible force to be exerted by the robot manipulator on an object in a vicinity of the robot manipulator; specify a target position of a reference point of the robot manipulator; determine a current position of the reference point of the robot manipulator; control the robot manipulator by performing an impedance regulation, wherein the impedance regulation has an artificial spring component and a current reference force of the artificial spring component is determined based on a specified spring stiffness and based on a difference between the current position and the target position of the reference point of the robot manipulator; and control the robot manipulator in order to execute an emergency control program if the current reference force exceeds the maximum permissible force.

13. The robot system of claim 12, wherein the emergency control program includes at least one of the following control programs: stopping the robot manipulator, moving the robot manipulator back to its original path, and switching to an alternative regulation mode.

14. The robot system of claim 12, wherein the maximum permissible force is specified by detection of an input of a user at a user interface.

15. The robot system of claim 12, wherein the maximum permissible force is specified using a database, wherein a plurality of body zones of a person with a respective associated maximum permissible force with respect to one of the body zones is stored in the database.

16. The robot system of claim 15, wherein a maximum permissible force is selected based on camera-based detection of a collision between a specific body zone of the person and the robot manipulator, wherein the specific body zone of the person is assigned to a body zone stored in the database and a maximum permissible force associated with the body zone assigned is selected as the maximum permissible force.

17. The robot system of claim 15, wherein maximum permissible forces stored in the database or one selected from the maximum permissible forces are adapted depending on an edge geometry of the robot manipulator and/or a task or task class to be performed by the robot manipulator.

18. The method of claim 12, wherein the target position is specified by specifying a desired path of the reference point of the robot manipulator.

19. The robot system of claim 12, wherein the current position of the reference point of the robot manipulator is determined based on redundant sensor signals.

20. The robot system of claim 12, wherein the target position of the reference point of the robot manipulator is specified behind a surface of the object, such that the robot manipulator exerts a force on the surface of the object in a direction of the target position.

21. The robot system of claim 13, wherein the alternative regulation mode is an admittance regulation mode and/or a gravitational force-compensated mode, and the switching to the alternative regulation mode includes ending all movement and/or force commands.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the drawings:

[0032] FIG. 1 shows a method according to an exemplary embodiment of the invention; and

[0033] FIG. 2 shows a robot system used to carry out the method according to FIG. 1.

[0034] The illustrations in the figures are schematic and not to scale.

DETAILED DESCRIPTION

[0035] FIG. 1 shows a method of operating a robot manipulator 1, the method including: [0036] specifying S1 a maximum permissible force to be exerted on an object 3 by the robot manipulator 1 in the vicinity of the robot manipulator 1; [0037] specifying S2 a target position 5 of a reference point 7 of the robot manipulator 1; [0038] determining S3 a current position of the reference point 7 of the robot manipulator 1; [0039] controlling S4 the robot manipulator 1 by performing an impedance regulation, wherein the impedance regulation has an artificial spring component and a current reference force of the artificial spring component is determined based on a specified spring stiffness and based on a difference between the current position and the target position 5 of the reference point 7 of the robot manipulator 1; and [0040] controlling S5 the robot manipulator 1 to execute an emergency control program if the current reference force exceeds the maximum permissible force.

[0041] The method as described in this FIG. 1 is performed on a robot system 100 in FIG. 2. The reference symbols identified above, which are not to be found in FIG. 1, therefore refer directly to FIG. 2. The method is explained in more detail below with reference to the robot system 100 of FIG. 2.

[0042] FIG. 2 shows a robot system 100 for carrying out the method of FIG. 1. The robot system 100 has a robot manipulator 1 and a control unit 11 connected to the robot manipulator 1. The control unit 11 specifies a maximum permissible force to be exerted by the robot manipulator 1 on an object 3, here specifically the body zone of the person 3 affected by a collision with a person 3. In this case, a collision is first detected by torque sensors in the joints of the robot manipulator 1. In contrast, the affected body zone is determined camera-based, i.e., based on an external camera system (not shown in FIG. 2). In the present example, this is the elbow of person 3. The control unit 11 queries a database as to the maximum permissible force that may be applied to the elbow of person 3. This maximum permissible force of the database is specified by the user via a user interface 9. The user interface 9 is a user computer that is connected to the control unit 11 of the robot manipulator 1. The corresponding body zone, namely the elbow of person 3, is assigned a corresponding maximum permissible force in the database. This maximum permissible force is read out. Since the control unit 11 is also designed to specify a current target position 5 of a reference point 7 of the robot manipulator 1, the collision causes an increasing deflection of the current position of the reference point 7 of the robot manipulator 1, which is thought to be arranged on the end effector of the robot manipulator 1. This continuous target position 5 of the reference point 7 continues accordingly on its specified trajectory. This current position of the reference point 7 of the robot manipulator 1 is continuously determined by the control unit 11. Moreover, the robot manipulator 1 is controlled by its control unit 11 by performing an impedance regulation, wherein the impedance regulation has an artificial spring component and a current reference force of the artificial spring component is determined based on a specified spring stiffness and based on a difference between the current position and the specified target position 5 of the reference point 7 of the robot manipulator 1. If this reference force exceeds the maximum permissible force associated with the body zone affected by the collision, the emergency control program is executed. The emergency control program includes a brief return of the robot manipulator on its path executed up to the collision, and then stopping the entire robot manipulator 1 in its current pose.

[0043] Although the invention has been further illustrated and described in detail by way of preferred example embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention. It is therefore obvious that several possible variations exist. It is also clear that illustrated embodiments are really only examples, which are not to be construed in any way as limiting the scope of protection, applicability, or configuration of the invention. Rather, the foregoing description and the description of the figures enable a person skilled in the art to concretely implement the example embodiments, and such person may make various changes based on the knowledge of the disclosed inventive concept, for example, with respect to the function or arrangement of individual elements cited in an example embodiment, without departing from the scope as defined by the claims and their legal equivalents, such as a more extensive explanation in the description.

LIST OF REFERENCE NUMERALS

[0044] 1 robot manipulator [0045] 3 object [0046] 5 target position [0047] 7 reference point [0048] 9 user interface [0049] 11 control unit [0050] 100 robot system [0051] S1 specifying [0052] S2 specifying [0053] S3 determining [0054] S4 controlling [0055] S5 controlling