Robot Gripper, and Method for Operating a Robot Gripper

Abstract

A robot gripper includes: a drive unit to drive a powertrain with active elements, wherein each element has a working region arranged in a body-fixed manner relative to the robot gripper, a respective element being moveable in and capable of reaching the working region; a control unit to control the drive unit; and a sensor system connected to the control unit to ascertain forces/moments applied externally to individual elements, the control unit configured such that collision monitoring is capable of being carried out for the elements, and when a collision is detected for an element, the drive unit is actuated according to a specified operation, including: providing a defined region within the working region for the elements, and collision monitoring for the elements only when the elements are located outside the assigned region, and deactivating collision monitoring when the elements are located at least partly within the assigned region.

Claims

1. A method of operating a robot gripper, wherein the robot gripper comprises: at least one drive unit AE to drive a powertrain AS with a number N of active elements WE.sub.n wherein each active element WE.sub.n has a working region AB.sub.n arranged in a body-fixed manner relative to the robot gripper, a respective active element WE.sub.n being moveable in and capable of reaching the working region; a control unit to control the at least one drive unit AE; and a sensor system connected to the control unit to ascertain forces/moments F.sub.ext,WEn(t), where n=1, 2, . . . , N and N≥1, applied externally to individual active elements WE.sub.n; wherein the control unit is designed and configured such that a collision monitoring is capable of being carried out for the active elements WE.sub.n, and that in an event of a detected collision event for an active element WE.sub.n, the drive unit AE is actuated according to a specified operation, the method comprising: providing in each case a defined region B.sub.n within the respective working region AB.sub.n for the active elements WE.sub.n; and carrying out the collision monitoring for the active elements WE.sub.n only when the respective active elements WE.sub.n are located outside of the assigned region B.sub.n, and deactivating the collision monitoring for the active elements WE.sub.n when the respective active elements WE.sub.n are located at least partly within the assigned region B.sub.n.

2. The method according to claim 1, wherein the robot gripper is a parallel jaw gripper with two active elements WE.sub.n=1,2, wherein: a common working region AB of the two active elements WE.sub.n=1,2 and a common region B are defined by respective spacing ranges that indicate spacings A of the active elements WE.sub.n=1,2 from one another; the common working region AB comprises all spacings A of the active elements WE.sub.n=1,2 from a minimum spacing A.sub.MIN to a maximum spacing A.sub.MAX, which the active elements WE.sub.n=1,2 are capable of assuming in each case with respect to one another; the region B comprises all spacings A of the active elements WE.sub.n=1,2 from A.sub.MIN to a specified spacing A.sub.B, wherein: A.sub.MIN≤A<A.sub.B or A.sub.MIN≤A≤A.sub.B and A.sub.B<A.sub.MAX; and a collision monitoring for the active elements WE.sub.n=1,2 is carried out only when the active elements WE.sub.n=1,2 have a spacing A> or ≥AB.sub.B.

3. The method according to claim 1, wherein the collision monitoring occurs based on a specified dynamic model of the robot gripper.

4. The method according to claim 1, wherein the collision monitoring occurs using a disturbance variable observer, wherein the disturbance variable observer is a performance observer, a pulse observer, a speed observer, or an acceleration observer.

5. The method according to claim 1, wherein the sensor system, using a position sensor, ascertains a position q.sub.AE of the drive unit AE and/or, using a position sensor, ascertains a position q.sub.AS of the powertrain AS and/or, using a speed sensor, ascertains a drive unit speed {dot over (q)}.sub.AE of the drive unit AE and/or, using a speed sensor, ascertains a powertrain speed {dot over (q)}.sub.AS of the powertrain AS and/or, using a torque sensor, ascertains a torque τ.sub.AE of the drive unit AE and/or, using a torque sensor, ascertains a torque τ.sub.AS in the powertrain AS and/or, using a current sensor, ascertains a motor current I.sub.M of the drive unit AE.

6. The method according to claim 5, wherein, for the collision monitoring, one or more of following measured variables: q.sub.AE, q.sub.AS, {dot over (q)}.sub.AE, {dot over (q)}.sub.AS, τ.sub.AE, τ.sub.AS, and I.sub.M are used.

7. The method according to claim 1, wherein the specified operation is selected from the following: stopping the drive unit AE; actuating the drive unit AE for gravity compensation; actuating the drive unit AE for friction compensation in the drive unit AE powertrain AS system; actuating the drive unit AE in such a manner that a controlled continuous moving apart of the active elements WE.sub.n occurs; and actuating the drive unit AE in such a manner that a reflex-like moving apart of the active elements WE.sub.n occurs.

8. The method according to claim 1, wherein the defining of the regions B.sub.n within the working regions AB.sub.n occurs by a manual or automated teach-in process on the robot gripper, the teach-in process comprising: gripping an object in such a manner that each of the active elements WE.sub.n mechanically contacts the object, wherein the region enclosed in the process by the active elements WE.sub.n defines regions AG.sub.n; ascertaining the regions B.sub.n, in that the regions AG.sub.n are widened outwardly by specified delta regions ΔB.sub.n, so that: B.sub.n=AG.sub.n+ΔB.sub.n; and storing B.sub.n.

9. A robot gripper comprising: at least one drive unit AE to drive a powertrain AS with a number N of active elements WE.sub.n, wherein the active elements WE.sub.n each have working regions AB.sub.n arranged in a body-fixed manner relative to the robot gripper, the active elements WE.sub.n being moveable in and capable of reaching the working regions; a control unit to control the at least one drive unit AE in closed loop and open loop manner; and a sensor system connected to the control unit to ascertain forces/moments F.sub.ext,WEn(t), where n=1, 2, . . . , N and N≥1, applied externally to the individual active elements WE.sub.n; wherein the control unit is designed and configured such that: a collision monitoring is capable of being carried out for the active elements WE.sub.n; the collision monitoring for the active elements WE.sub.n is carried out only when the respective active elements WE.sub.n are located outside of a specified assigned region B.sub.n located within the working region AB.sub.n; the collision monitoring for the active elements WE.sub.n is deactivated, when the respective active elements WE.sub.n are located at least partially within the assigned region B.sub.n; and in an event of a detected collision event for an active element WE.sub.n, the drive unit is actuated according to a specified operation.

10. The robot gripper according to claim 9, wherein the sensor system comprises: a position sensor to ascertain a position q.sub.AE of the drive unit AE and/or a position sensor to ascertain a position q.sub.AS of the powertrain AS and/or a speed sensor to ascertain a drive unit speed {dot over (q)}.sub.AE of the drive unit AE and/or a speed sensor to ascertain a powertrain speed {dot over (q)}.sub.AS of the power train AS and/or a torque sensor to ascertain a torque τ.sub.AE of the drive unit AE and/or a torque sensor to ascertain a torque τ.sub.AS in the drive strand of the powertrain AS and/or a current sensor to ascertain a motor current I.sub.M of an electric motor of the drive unit AE.

11. The robot gripper according to claim 9, wherein the drive unit AE is a motor coupled via a transmission to the powertrain AS, and a torque sensor to ascertain a torque τ.sub.AS in the powertrain AS is connected between the transmission and the powertrain AS.

12. A robot or a humanoid with a robot gripper according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In the drawings:

[0066] FIG. 1 is a highly schematic method sequence; and

[0067] FIG. 2 is a highly schematic above design of a proposed robot gripper.

DETAILED DESCRIPTION

[0068] FIG. 1 shows a highly schematic sequence of a method for operating a robot gripper, wherein the robot gripper includes: at least one drive unit AE for driving a powertrain AS with a number N of active elements WE.sub.n, wherein the active elements WE.sub.n each have a working region arranged in a body-fixed manner relative to the robot gripper, in which the active elements WE.sub.n are movable and can be reached by them, a control unit for controlling the drive unit AE, and a sensor system connected to the sensor unit for ascertaining forces/moments F.sub.ext,WEn(t), where n=1, 2, . . . , N and N≥1, which are applied externally to the individual active elements WE.sub.n.

[0069] The control unit is designed and configured in such a manner that, for the active elements WE.sub.n, a collision monitoring can be carried out autonomously and locally (i.e., without requiring an external control unit and/or an external processor), and in such a way that, when a collision is detected for an active element WE.sub.n, the drive unit is autonomously and locally actuated according to a specified operation.

[0070] The method includes the following steps which are carried out during the operation of the robot gripper, in particular, during the gripping of an object by the robot gripper. In a first step 201, for the active elements WE.sub.n, in each case a provision of a defined region B.sub.n within the assigned working region AB.sub.n occurs.

[0071] During the actuation of the robot gripper for carrying out a gripping task, for example, controlled by an external central control unit of a robot, to which the robot gripper is connected, in step 202, an autonomous carrying out of the collision monitoring by the control unit of the robot gripper for the active elements WE.sub.n always occurs when the respective active elements WE.sub.n are located outside the region B, and a deactivation of the collision monitoring for the active elements WE.sub.n always occurs when the respective active elements WE.sub.n are located at least partly within the region B.sub.n

[0072] Advantageously, the control unit of the robot gripper generates a collision signal when, for one of the active elements WE.sub.n, a collision is detected. Advantageously, the control unit of the robot gripper generates a deactivation signal when the collision monitoring for an active element WE.sub.n is deactivated. Advantageously, the robot gripper provides the collision signal and/or the deactivation signal to an interface, so that the signals can be transmitted to external control units.

[0073] In an embodiment of the proposed method, the collision monitoring for all active elements WE.sub.n is deactivated when at least one active element WE.sub.n is located at least partly within the assigned region B.sub.n.

[0074] FIG. 2 shows a highly schematic design of a proposed robot gripper 100 which is implemented as parallel jaw gripper. The robot gripper 100 includes: a drive unit 101 which in the present case is formed as an electric motor with a downstream transmission 110 and which is used for driving a powertrain 102 with a number N=2 of active elements WE.sub.n=1,2 103 (also referred to as: gripper jaws). The drive unit 101 drives the active elements WE.sub.n=1,2 103 via the powertrain 102 in such a manner that they move either toward one another or apart from one another and thus the spacing A of the active elements WE.sub.n=1,2 103 changes accordingly.

[0075] The two active elements WE.sub.n=1,2 103 have a common working region AB arranged in a body-fixed manner relative to the robot gripper, in which the active elements WE.sub.n=1,2 103 can be moved or which they can assume. In the present case, the working region AB is composed of a first working region AB.sub.n=1 of the upper gripper jaw 103a represented in FIG. 2, which reaches from the represented position A.sub.MAX,n=1 to a center (dash-dot-dot-line), and of a second working region AB.sub.n=2 of the lower gripper jaw 103b represented in FIG. 2, which reaches from the represented position A.sub.MAX,n=2 to the center (dash-dot-dot line).

[0076] Thus, in the present case, the composed working region AB of the parallel jaw gripper corresponds to all spacings A of the active elements WE.sub.n=1,2 103 from A=0 (minimum spacing of the active elements WE.sub.n=1,2) up to and including the maximum spacing A.sub.MAX=|A.sub.MAX,n=1−A.sub.MAX,n=2|, which the active elements WE.sub.n=1,2 103 can assume with respect to one another (marked AB in FIG. 2).

[0077] The parallel jaw gripper moreover has a control unit 104 for controlling the drive unit 101 and a sensor system 105 connected to the control unit 104 for ascertaining forces/moments F.sub.ext,WEn(t), where n=1, 2, . . . , N and N≥1, which are applied externally to the individual active elements WE.sub.n=1,2.

[0078] In the present case, the sensor system 105 includes a position sensor for ascertaining a motor position q.sub.AE of the electric motor, a current sensor for ascertaining a motor current I.sub.AE of the electric motor, as well as a torque sensor connected between the transmission 110 and the powertrain 102 for ascertaining the torque τ.sub.AS. The measurement variables q.sub.AE, I.sub.AE and τ.sub.AS are provided to the control unit 104.

[0079] Moreover, the parallel jaw gripper 100 has an interface 111 for electrical energy, as well as a control signal of an external control unit. The interface 111 is connected to the control unit 104 by at least one signal line 112 and at least one electric line 113.

[0080] If the parallel jaw gripper 100 is connected, for example, as effector, to a manipulator of a robot, then, via the interface 111, for example, control signals are provided to a central control unit of the robot, as well as energy for the parallel jaw gripper 100.

[0081] The control unit 104 is designed and configured in such a manner that, for the active elements WE.sub.n=1,2 103, a collision monitoring can be carried out; the collision monitoring for the active elements WE.sub.n=1,2 103 is carried out only when the respective active elements W.sub.n=1,2 103 are located outside of a specified region B located within the working region AB; the collision monitoring for the active elements WE.sub.n=1,2 103 is deactivated when the respective active elements WE.sub.n=1,2 103 are located at least partly within the region B, and if, for an active element WE.sub.n=1,2, a collision is detected, the drive unit 101 is actuated according to a specified operation.

[0082] This collision monitoring is in principle carried out independently of control commands, for example, an external robot malfunction.

[0083] The region B, i.e., the region in which the collision monitoring according to the invention is deactivated, in the present case is specified depending on the task definition correspondingly by a spacing limit value A.sub.B, wherein the region B is defined by a spacing A of the active elements WE.sub.n=1,2 for which: A<A.sub.B or A≤A.sub.B and A.sub.B<A.sub.MAX. In this development, a collision monitoring for the active elements WE.sub.n=1,2 is only carried out if the active elements WE.sub.n=1,2 have a spacing > or ≥A.sub.B. Particularly preferably, the active elements (gripper jaws) of the parallel jaw gripper have no sensors.

[0084] In FIG. 2, the above indicated regions are illustrated for a situation in which a sphere (in cross section) is arranged centrally between the gripper jaws 103a, 103b, wherein the gripper jaws 103a, 103b in each case are located in the position of their maximum displacement, i.e., their maximum spacing. The represented maximum spacing of the gripper jaws defines the working region AB. The region B located within the working region AB indicates the region in which a collision monitoring is deactivated. In the present case, the region B is defined by the diameter D=AG of the sphere, as well as by a safety zone ΔB/2 on both sides of the sphere.

[0085] If, during the gripping of the sphere, wherein the gripper jaws are moved toward one another from the position shown, external forces/moments are exerted on the gripper jaws, then a corresponding collision is detected if the gripper jaws in each case are located outside the region B. The detected collision leads to a specified operation, in particular, to a stopping of the drive unit. Moreover, a collision signal is provided at the interface 111 for transmission to an external control unit.

[0086] The collision monitoring in the control unit 104 occurs on the basis of a specified dynamic model of the parallel jaw gripper 100. Moreover, the collision monitoring in the control unit 104 occurs using a disturbance variable observer.

LIST OF REFERENCE NUMERALS

[0087] 100 Robot gripper

[0088] 101 Drive unit

[0089] 102 Powertrain

[0090] 103 Active elements WE.sub.n

[0091] 104 Control unit

[0092] 105 Sensor system

[0093] 110 Transmission

[0094] 111 Interface for electrical energy and control signal of an external control unit

[0095] 112 Control signal line

[0096] 113 Electrical energy line

[0097] 201, 202 Method steps