Method and Device for Open-Loop/Closed-Loop Control of a Robot Manipulator

Abstract

The invention relates to a device and to a method for open-loop/closed-loop control of a robot manipulator (202), which comprises a sensor (203) for detecting an interaction with an environment. The proposed method is characterized in that a force-time curve of an external force (I) acting on the robot manipulator (202) is detected by the sensor (203), and, if the value of the detected force (II) is higher than a defined threshold value G1: (II)>G1, a safety mode of the robot manipulator (202) is activated, which open-loop controls a movement speed (III) and/or a movement direction (IV) depending on the detected force (I), wherein the movement speed (III) and/or the movement direction (IV) of the robot manipulator (202) is/are open-loop/closed-loop controlled depending on predetermined medical injury parameters before the safety mode is activated.

Claims

1. A method for open-loop/closed-loop control of a robot manipulator, which comprises a sensor for detecting a mechanical interaction with an environment, wherein a force-time curve of an external force {right arrow over (F)} (t) acting on the robot manipulator is detected by the sensor, and, if the value of the detected force |{right arrow over (F)} (t)| is greater than a defined threshold value G1: |{right arrow over (F)} (t)|>G1, a safety mode of the robot manipulator is activated, which open-loop/closed-loop controls a movement speed |{right arrow over (V)} (t)| and/or a movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| of the robot manipulator depending on the detected force {right arrow over (F)} (t), wherein the movement speed |{right arrow over (V)} (t)| and/or the movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| of the robot manipulator is/are open-loop/closed-loop controlled before the activation of the safety mode depending on predetermined medical parameters.

2. The method according to claim 1, in which, in the safety mode, at least one actuator of the robot manipulator is open-loop/closed-loop controlled depending on the detected force {right arrow over (F)} (t).

3. The method according to claim 2, wherein a torque generated by the actuator and/or position of the actuator and/or a speed of the actuator is/are individually limited depending on the detected force {right arrow over (F)} (t).

4. The method according to claim 1, wherein for G1: G1=0.

5. The method according to claim 1, wherein a time span Δt.sub.1 is determined, which indicates the time span from the time when the threshold value G1 is exceeded at time t.sub.0 to the time when a subsequent first maximum Max1(|{right arrow over (F)} (t)|) of the force-time curve {right arrow over (F)} (t) at time t.sub.1 is reached, a time span Δt.sub.2 is determined which indicates a time span from t.sub.1 until the time when a subsequent first minimum Min1(|{right arrow over (F)} (t)|) of the force-time curve {right arrow over (F)} (t) at time t.sub.2 is reached, and the safety mode is activated only when: Δt.sub.1+Δt.sub.2=Δt.sub.G<G2 and/or Max1(|{right arrow over (F)} (t)|)>G3, wherein G2 and G3 are defined threshold values.

6. The method according to claim 5, wherein, if for a time t>t.sub.2, the value of the force |{right arrow over (F)} (t)| exceeds a defined threshold value G4: |{right arrow over (F)} (t)|>G4, a current movement of the robot manipulator is stopped.

7. The method according to claim 5, wherein, if for a time t>t.sub.2, the value of the force |{right arrow over (F)} (t)| exceeds a defined boundary G4: |{right arrow over (F)} (t)|>G4, a gravitation compensation is carried out, in which the manipulator is open-loop/closed-loop controlled control in such a manner that only the gravitation force is compensated, and any additional externally applied force leads to the robot manipulator moving away from said force in a compliant manner.

8. The method according to claim 6, wherein, after the stopping, the previous movement of the robot manipulator is carried out in reverse direction, until: {right arrow over (F)} (t)<G5, and then stopped again, wherein G5 is a defined threshold value.

9. The method according to claim 8, wherein: G5=0.

10. A computer system with a data processing device, wherein the data processing device is designed in such a manner that a method according to claim 1 is carried out on the data processing device.

11. A digital storage medium with electronically readable control signals, wherein the control signals can interact with a programmable computer system in such a manner that a method according to claim 1 is carried out.

12. A computer program product with a program code, stored on a machine-readable support, for carrying out the method according to claim 1, when the program code is carried out on a data processing device.

13. The computer program with program code for carrying out the method according to claim 1, when the program is run on a data processing device.

14. A device for the open-loop/closed-loop control of a robot manipulator and for carrying out a method according to claim 1, comprising: a sensor, which detects a force-time curve of an external force {right arrow over (F)} (t) acting on the robot manipulator, a unit, which is designed and configured in such a manner that a movement speed |{right arrow over (V)} (t)| and/or a movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| of the robot manipulator is/are open-loop/closed-loop controlled depending on predetermined medical parameters, and that, if the value of the detected force |{right arrow over (F)} (t)| is greater than a defined threshold value G1: |{right arrow over (F)} (t)|>G1, a safety mode of the robot manipulator is activated, which open-loop/closed-loop controls the movement speed |{right arrow over (V)} (t)| and/or the movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| depending on the detected force {right arrow over (F)} (t).

15. The device according to claim 14, wherein the unit is designed and configured in such a manner that a time span Δt.sub.1 is determined, which indicates the time span from the time when the threshold value G1 is exceeded at time t.sub.0 to the time when a subsequent first maximum Max1(|{right arrow over (F)} (t)|) of the force {right arrow over (F)} (t) at time t.sub.1 is reached, a time Δt.sub.2 is determined, which indicates a time span from t.sub.1 to the time when a subsequent first minimum Min1(|{right arrow over (F)} (t)|) of the force {right arrow over (F)} (t) at t.sub.2 is reached, and the safety mode is activated only when: Δt.sub.1+Δt.sub.2=Δt.sub.G<G2 and/or Max1(|{right arrow over (F)} (t)|)<G3, wherein G2 and G3 are defined threshold values.

16. A robot with a device according to claim 14.

Description

[0038] Additional advantages, features and details result from the subsequent description, in which—if applicable in reference to the drawings—at least one embodiment example is described in detail. Identical, similar and/or functionally equivalent parts are provided with identical reference numerals.

[0039] The figures show:

[0040] FIG. 1 a typical force-time curve when the robot manipulator collides with an object, in the case of a spatial blocking of the object,

[0041] FIG. 2 a diagrammatic procedure of the proposed method for an exemplary embodiment, and

[0042] FIG. 3 a diagrammatic design of a robot according to the invention.

[0043] FIG. 1 shows a typical force-time curve in a collision of the robot manipulator with an object, in the case of a spatial blocking of the object, i.e., in the case in which the object, after the collision with the robot manipulator, cannot move away and is thus spatially immobilized and hence squeezed.

[0044] In FIG. 1, the x axis represents the time t, and the y axis represents the value of an external force: |{right arrow over (F)} (t)| detected by a sensor, which acts on the robot manipulator. As can be seen from the represented curve, starting at time t.sub.0, an external force is detected by the sensor, i.e., at time t.sub.0 a collision of the robot manipulator with an object occurs, for example, with an arm of a human. After a first maximum M1 has been reached at time t.sub.1 after 5 ms, for example, the value of the force detected by the sensor decreases again until at time t.sub.2 a first minimum is reached. The represented force-time curve is not true to scale and indicates only the qualitative force curve.

[0045] Due to the spatial immobilization of the arm, for example, the arm is arranged between the robot manipulator and a wall, the arm is squeezed by the further movement of the robot manipulator, which manifests itself in the still rising force curve for a time greater than t.sub.2.

[0046] FIG. 2 shows a diagrammatic course of an exemplary embodiment of the method for open-loop control of a robot manipulator, which, for the detection of a mechanical interaction with an environment, comprises a sensor. The movement speed |{right arrow over (V)} (t)| and the movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| of the robot manipulator are open-loop controlled in this example depending on predetermined medical injury parameters. The medical injury parameters contain information representative of an effect of a collision between the robot manipulator and the human body. Further information on different injury parameters can be found in DE 102013212887 A1, to which reference is made in this regard. In the case at hand, the open-loop control of the robot manipulator occurs in principle by means of a speed open-loop control, which implicitly can ensure a speed, for example, by introducing a virtual (possibly variable) damping, which generates corresponding counter-torques, in order to ensure the speed in spite of the actuation in the form of a torque closed-loop control.

[0047] During the operation of the robot manipulator, a continuous detection 101 of the force-time curve of an external force {right arrow over (F)} (t) acting on the robot manipulator is carried out by the sensor. This force-time curve is stored at least temporarily. If, in the process, a value of the detected force |{right arrow over (F)} (t)| greater than a defined threshold value G1 is detected: |{right arrow over (F)} (t)|>G1, then an activation 102 of a safety mode of the robot manipulator occurs. The safety mode is characterized in that the movement speed |{right arrow over (V)} (t)| and the movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| are open-loop controlled depending on the detected force {right arrow over (F)} (t). Thus, in this case of a speed open-loop control there is a switch from a speed open-loop control to a force open-loop control. However, in principle, the switch can be implemented by a torque closed-loop regulation.

[0048] FIG. 3 shows a diagrammatic structure of a robot with a device for open-loop control of a robot manipulator 202 of the robot. The robot comprises a sensor 203, which detects a force-time curve of an external force {right arrow over (F)} (t) acting on the robot manipulator 202, and a unit 201, which is designed and configured in such a manner that a movement speed |{right arrow over (V)} (t)| and/or a movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| of the robot manipulated 202 is/are controlled depending on predetermined medical injury parameters, and that, if the value of the detected force |{right arrow over (F)} (t)| is greater than a defined threshold value G1: |{right arrow over (F)} (t)|>G1, a safety mode of the robot manipulator 202 is activated, which open-loop controls the movement speed |{right arrow over (V)} (t)| and/or the movement direction {right arrow over (V)} (t)/|{right arrow over (V)} (t)| depending on the detected force {right arrow over (F)} (t).

[0049] Although the invention is illustrated and explained in greater detail by means of preferred exemplary embodiments, the invention is not limited to the disclosed examples and other variations can also be derived therefrom by the person skilled in the art, without leaving the scope of protection of the invention. Therefore, it is clear that there are numerous possible variations. It is also clear that embodiments mentioned as examples really represent only examples which in no way should be conceived of as a limitation of, for example, the scope of protection, of the possible applications, or of the configuration of the invention. Rather, the preceding description and the description of the figures enable the person skilled in the art to concretely implement the exemplary embodiments, wherein the person skilled in the art, having learned the disclosed inventive thought, can make numerous changes, for example, with regard to the function of the arrangement, to an exemplary embodiment of mentioned elements, without leaving the scope of protection which is defined by the claims and their legal equivalents such as, for example, a more detailed explanation in the description.

LIST OF REFERENCE NUMERALS

[0050] 101-102 Method steps

[0051] 201 Unit for open-loop/closed-loop control

[0052] 202 Robot manipulator

[0053] 203 Sensor