Patent Application
20220184812
The invention relates to a robot gripper and to a method for operating a robot gripper.
Robot grippers (also referred to as “grippers” or “gripping system” or “effector” or “end effector”) are known in the prior art. Robot grippers are typically arranged on the distal end of robot manipulators and perform tasks such as gripping and/or holding objects/tools.
A robot gripper typically includes a drive unit, a powertrain (also referred to as: kinematic system), which moves active elements, a mechanical interface for the detachable fixed connection of the robot gripper, for example, to a robot manipulator, an energy interface for supplying energy necessary for the operation of the robot gripper, as well as a control signal interface for supplying control signals (for example, from a central robot control unit).
Active elements are elements of the robot gripper which are in direct contact with an object when gripping and holding the object, and in the process can exert a gripping force on the object. There are various possibilities for how a robot gripper can hold an object. Here, a distinction is made, for example, between different active matings: force mating, shape mating, substance mating. Moreover, multiple forms of the active elements themselves exist, for example, in the form of gripper jaws (in a parallel jaw gripper) or multi-member fingers (in an artificial hand).
The drive unit generates the kinetic energy necessary for the gripping or holding process. The drive unit drives the powertrain and thus generates corresponding movements of the active elements. Thereby, the opening, closing, and holding of an object by the robot gripper is possible.
The powertrain is used for transmitting the kinetic energy generated by the drive unit to the active elements. It thus converts a movement of the drive unit into a drive movement of the robot gripper, i.e., into a corresponding movement of the active elements.
The aim of the invention is to provide a robot gripper which enables an operation with improved safety.
The invention results from the features of the independent claims. Advantageous developments and embodiments are the subject matter of the dependent claims. Additional features, application possibilities and advantages of the invention result from the following description as well as from the explanation of embodiment examples of the invention, which are represented in the figures.
A first aspect of the invention relates to 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 WEn, wherein the active elements WEn each have a working region ABn which is arranged in a body-fixed manner relative to the robot gripper, in which working region the respective active elements WEn can be moved, and which working region can be reached by them;
a control unit for controlling the at least one drive unit AE, and a sensor system which is connected to the control unit for ascertaining forces/moments Fext,WEn(t), where n=1, 2, . . . , N and N≥1, which are applied externally to the individual active elements WEn; wherein the control unit is designed and configured such that a collision monitoring can be carried out for the active elements WEn, and in the event of a detected collision for an active element Wn, the drive unit AE is actuated according to a specified operation, having the following steps: providing in each case a region Bn within the respective working region ABn for the active elements WEn and carrying out the collision monitoring for the active elements WEn only when the respective active elements WEn are located outside of the region Bn, and deactivating the collision monitoring for the active elements WEn when the respective active elements WEn are located at least partly within the assigned region Bn.
In the present case, the drive unit AE converts energy provided by the robot gripper (for example, pneumatic energy, hydraulic energy or electric energy) into a mechanical energy, i.e., into a movement. This movement is advantageously a translational and/or rotational movement. Advantageously, the drive unit is an electric motor which converts the provided electrical energy (potential U, current I) into a mechanical rotation. Depending on the application, other drive units are naturally also suitable, such as, for example, a hydraulic motor or a pneumatic motor for driving the powertrain. Advantageously, the drive unit drives multiple active elements WEn, in particular, two active elements WEn=1,2. Advantageously, the robot gripper has multiple drive units, each driving one or more active elements WEn. The drive unit AE can, in particular, include a transmission for speed reduction or speed increase of a rotational movement.
The powertrain AS (also referred to as kinematic system) transmits the mechanical movement generated by the drive unit AE to one or more active elements WEn, so that they move correspondingly. For the mechanical implementation of the powertrain AS in a robot gripper, a plurality of implementations are known in the prior art. Particularly advantageously, the powertrain AS includes a belt, in particular, a toothed belt.
The working regions ABn of the active elements WEn each indicate a region which is arranged in a body-fixed manner relative to the robot gripper, in which the active elements WEn can be moved and which can be reached by them. The working regions ABn are thus defined in particular by the region which is spanned between the active elements WEn when the active elements WEn are open to the maximum. Since the working regions ABn are defined in a body-fixed manner relative to the robot gripper, the working regions ABn always remain identical independently of the position and orientation of the robot gripper.
According to the invention, the robot gripper has a sensor system for ascertaining forces/moments Fext,WEn(t), where n=1, 2, . . . , N and N≥1, which are applied externally to the individual active elements WEn. Forces/moments applied on other parts of the robot gripper, for example, on a housing of the robot gripper, are therefore not acquired by this sensor system.
In a particularly advantageous development of the proposed method, using a position sensor, a position qAE of the drive unit AE, and/or, using a position sensor, a position qAS of the powertrain, and/or, using a speed sensor, a drive unit speed qAE of the drive unit AE, and/or, using a speed sensor, a powertrain speed qAs of the powertrain AS, and/or, using a torque sensor, a torque τAE of the drive unit of the AE, and/or, using a torque sensor, a torque τAS in the powertrain AS, and/or, using a current sensor, a motor current IM of an electric motor of the drive unit AE is/are determined.
Advantageously, no sensors are arranged on the active elements WEn. As a result, a corresponding cable connection to sensors on the active elements WEn is omitted. The active elements WEn are also advantageously exchangeable. Thus, advantageously, different types of active elements WEn can be connected to the powertrain AS, for example, in order to enable different active matings such as force mating, shape mating, substance mating during the gripping or holding.
The provision of the regions Bn within the working regions ABn can occur, for example, by corresponding inputs on the control unit, by reading a corresponding data memory of the control unit, by data transmission to the control unit via a data interface of the robot gripper, by a manual or automated “teach-in” process on the robot gripper after subsequent storing in a data memory of the control unit.
According to the invention, the control unit is designed and configured in such a manner that a collision monitoring for the active elements WEn is carried out only when the respective active elements WEn are located outside of the assigned regions Bn, and deactivating of the collision monitoring for the active elements WEn is carried out only when the respective active elements WEn are located at least partly within the respective assigned regions Bn.
The regions Bn are advantageously defined depending on an external geometry AG of an object to be gripped. Here, the external geometry AG can be defined, for example, in the case of a spherical object, by the diameter of the object. Here, the regions Bn are advantageously selected/defined in such a manner that the regions Bn include the external geometry AG (the edge/the surface of the object) of the object to be gripped, as well as a difference region ΔBn adjoining it externally: Bn=AG+ΔBn. Here, the sizes of the different region ΔBn are selected depending on the task definition, the safety standards to be applied (for example, jamming protection) and/or the sensitivity/rupture strength of the object to be gripped.
When carrying out the method, an objective of which is to grip an object, the collision monitoring/collision detection is accordingly carried out only outside of the regions Bn, i.e., outside of a zone (difference region ΔBn) around an object which is optimally positioned for gripping. Within this zone, in this example, the collision monitoring/collision detection is deactivated.
Advantageously, the working regions ABn are each a three-dimensional or a two-dimensional or a one-dimensional region. Advantageously, the regions Bn are each a three-dimensional or a two-dimensional or a one-dimensional region.
In a particularly preferable development of the proposed method, the robot gripper is designed as a parallel jaw gripper with two active elements WEn=1,2, wherein a common working region AB and a common region B are defined by spacing ranges of the active elements WEn=1,2. The working region AB is advantageously defined as the spacing range from a minimum spacing AMIN to a maximum spacing AMAX, which the active elements WEn=1,2 can assume with respect to one another. Depending on the task definition, the region B of this development is correspondingly specified by a maximum spacing limit value AB and thus covers all spacings A from AMIN to the spacing AB.
Thus, the region B is defined by the spacings A of the active elements WEn=1,2 with respect to one another, for which: AMIN≤A<AB or AMIN≤A≤AB and AB<AMAX. In this development, a collision monitoring for the active elements WEn=1,2 is carried out only when the active elements WEn=1,2 have a spacing A for which: A>AB or A≥AB. Particularly preferably, the active elements (gripper jaws) of the parallel jaw gripper have no sensors.
The activation or deactivation of the collision monitoring according to the method, depending on a current position of the active elements WEn and depending on the defined regions Bn, occurs in principle independently of whether an object is arranged in such a manner relative to the robot gripper that it can also be gripped by the robot gripper, i.e., even if no object is arranged between the active elements WEn, a collision monitoring for the active elements WEn is carried out only when the respective active elements WEn are located outside of the assigned region Bn, and the collision monitoring for the active elements WEn is deactivated when the respective active elements WEn are located at least partly within the assigned region Bn.
An advantageous development of the robot gripper is characterized in that the robot gripper has a sensor, by which a presence or absence of an object in a gripping region of the robot gripper can be acquired, i.e., in that the sensor acquires that an object is arranged in such a manner that it can currently also be gripped by the robot gripper. If an object in the gripping region is ascertained by this sensor, then the collision monitoring for the active elements WEn is deactivated if they are located at least partly within the specified regions Bn. If no object in the gripping region is ascertained by this sensor, then advantageously no deactivation of the collision monitoring within the regions Bn occurs. In this case, the collision monitoring is carried out in the entire working region of the robot gripper.
The sensor for ascertaining an object in the gripping region of the robot gripper advantageously is, for example, a camera sensor, an ultrasound sensor, a laser sensor, an infrared sensor, a capacitive sensor, an inductive sensor, a microwave sensor, or a combination thereof.
An advantageous development of the proposed method is characterized in that the collision monitoring occurs on the basis of a specified dynamic model of the robot gripper. The dynamic model is a mathematical model which enables simulating the components of the robot gripper and their dynamic interactions. The control unit for closed loop and open loop control of the drive unit is in particular based on the dynamic model.
Advantageously, the collision monitoring for the active elements WEn occurs using a disturbance variable observer, in particular a performance observer or a pulse observer or a speed observer or an acceleration observer. Advantageously, for the collision monitoring, one or more of the measured variables: qAE, qAS, {dot over (q)}AE, {umlaut over (q)}AE, {dot over (q)}AS, {umlaut over (q)}AS, τAE, τAS, Im are used. Here, the variables: {dot over (q)}AE, {umlaut over (q)}AE and {dot over (q)}AS, {umlaut over (q)}AS, respectively, can also be ascertained on the basis of corresponding time derivatives from the variables: qAE and qAS, respectively.
Advantageously, the collision monitoring occurs on the basis of a comparison of a target position and an actual position for qAE, qAS.
According to a development of the proposed method, the operation is selected from the following possibilities of a non-comprehensive list:
Advantageously, defining the regions Bn within the working regions ABn occurs by a manual or automated teach-in process on the robot gripper. Advantageously, the teach-in process includes the following steps:
Storing Bn preferably occurs on a memory unit of the robot gripper.
By an appropriate selection of the regions Bn, in particular, jamming risks during the operation of the gripper in collaboration with a human, in particular, during an automatically performed gripping process of the robot gripper, are prevented or at least considerably reduced.
For example, if a sphere having a diameter of 5 cm (AG=5 cm) is to be gripped by a parallel jaw gripper, then, for the two gripper jaws, a common region B=AG+ΔB is advantageously defined by a spacing of the gripper jaws of 5.5 cm. Thereby, in the case of a central arrangement of the sphere between the gripper jaws, 2.5 mm (=ΔB/2) remain on each side of the sphere, before a collision monitoring during a further movement toward one another of the gripper jaws is deactivated. The 2.5 mm on each side of the sphere advantageously are measured in such a way that no human finger fits between gripper jaw and sphere.
The proposed method thus improves, in particular, the safety during a collaboration between robot gripper and an operator.
The robot gripper, to the extent that it is connected to a manipulator of a robot, can receive control commands from a central control unit of the robot. These control commands are transmitted to the control unit of the robot gripper. The control unit of the robot gripper converts these control commands and in principle actuates the drive unit correspondingly, wherein the collision monitoring according to the invention as well as the activation or respectively deactivation of the collision monitoring according to the invention are carried out locally on the control unit of the robot gripper. Advantageously, for the active elements WEn, collisions as detected are transmitted by the control unit of the robot gripper to a central control unit of the robot.
An additional aspect of the invention relates to a robot gripper including: at least one drive unit AE for driving a powertrain AS with a number N of active elements WEn, wherein the active elements WEn each have working regions ABn, which are arranged in a body-fixed manner relative to the robot gripper, in which the active elements WEn can each be moved, and which can be reached by them; a control unit for closed loop and open loop control of the at least one drive unit AE; and a sensor system connected to the control unit for ascertaining forces/moments Fext,WEn(t), where n=1, 2, . . . , N and N≥1, which are applied externally to the individual active elements WEn; wherein the control unit is designed and configured in such a manner that, for the active elements WEn, a collision monitoring can be carried out; the collision monitoring for the active elements WEn is carried out only when the respective active elements WEn are located outside of a specified assigned region Bn located within the working region ABn; the collision monitoring for the active elements WEn is deactivated when the respective active elements WEn are located at least partly within the assigned region Bn; and if for an active element WEn a collision is detected, the drive unit is actuated according to a specified operation.
The drive unit AE is advantageously an electric motor or a hydraulic actuator or a pneumatic actuator. The drive unit AE can additionally include a transmission unit.
Advantageously, the drive regions ABn are each a three-dimensional or a two-dimensional or a one-dimensional region. Advantageously, the regions Bn are each a three-dimensional or a two-dimensional or a one-dimensional region.
In a particularly preferred development, the robot gripper is designed as a parallel jaw gripper with two active elements WEn=1,2, wherein a common working region AB and a common region B are defined by spacing ranges of the active elements WEn=1,2. The working region AB is advantageously defined as the spacing range from a minimum spacing AMIN to a maximum spacing AMAX, which the active elements WEn=1,2 can assume with respect to one another. Depending on the task definition, the region B of this development is correspondingly specified by a maximum spacing limit value AB and thus covers all spacings A from AMIN to the spacing ABB.
Thus, the region B is defined by the spacings A of the active elements WEn=1,2 with respect to one another, for which: AMIN≤A<AB or AMIN≤A≤AB and AB<AMAX. In this development, a collision monitoring for the active elements WEn=1,2 is carried out only when the active elements WEn=1,2 have a spacing A for which: A>AB or A≥AB. Particularly preferably, the active elements (gripper jaws) of the parallel jaw gripper have no sensors.
In an advantageous development of the robot gripper, the sensor system has one or more of the following sensors: a position sensor for ascertaining a position qAE of the drive unit AE and/or a position sensor for ascertaining a position qAS of the powertrain AS and/or a speed sensor for ascertaining a drive unit speed {dot over (q)}AE of the drive unit AE and/or a speed sensor for ascertaining a powertrain speed {dot over (q)}AS of the powertrain AS and/or a torque sensor for ascertaining a torque τAE of the drive unit AE and/or a torque sensor for ascertaining a torque τAS in the powertrain AS and/or a current sensor for ascertaining the motor current IM of an electric motor of the drive unit AE.
In an advantageous development of the proposed robot gripper, the control unit is designed and configured in such a manner that the collision monitoring occurs on the basis of a specified dynamic model of the robot gripper.
Advantageously, the control unit is designed and configured in such a manner that the collision monitoring occurs using a disturbance variable observer, in particular by a performance observer or a pulse observer or a speed observer or an acceleration observer.
Advantageously, for the collision monitoring, one or more of the measured variables: qAE, qAS, {dot over (q)}AE, {umlaut over (q)}AE, {dot over (q)}AS, {umlaut over (q)}AS, τAE, τAS, IM are used. Here, the variables: {dot over (q)}AE, {umlaut over (q)}AE and {dot over (q)}AS, {umlaut over (q)}AS, respectively, can also be ascertained on the basis of corresponding time derivatives from the variables: qAE and qAS, respectively.
An advantageous development of the robot gripper is characterized in that the drive unit AE is a motor which is coupled via a transmission to the powertrain AS and in that a torque sensor for ascertaining a torque τAS in the powertrain AS is arranged between the transmission and the powertrain. The motor is advantageously an electric motor.
Advantageously, the control unit is designed and configured in such a manner that the operation is selected from the following possibilities of a non-comprehensive list:
Advantageously, the robot gripper has a housing, in which at least the drive unit AE and the control unit are integrated. The control unit advantageously includes a processor, a memory unit, as well as an interface for the specification of target control variables, for example, of a central computer for controlling a robot, to which the robot gripper is connected.
Finally, the invention relates to a robot or humanoid with a robot gripper, as described above.
Additional advantages, features and details result from the following description in which at least one embodiment example is described in detail, optionally in reference to the drawings. Identical, similar and/or functionally equivalent parts are provided with identical reference numerals.
In the drawings:
The control unit is designed and configured in such a manner that, for the active elements WEn, 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 WEn, the drive unit is autonomously and locally actuated according to a specified operation.
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 WEn, in each case a provision of a defined region Bn within the assigned working region ABn occurs.
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 WEn always occurs when the respective active elements WEn are located outside the region B, and a deactivation of the collision monitoring for the active elements WEn always occurs when the respective active elements WEn are located at least partly within the region Bn
Advantageously, the control unit of the robot gripper generates a collision signal when, for one of the active elements WEn, a collision is detected. Advantageously, the control unit of the robot gripper generates a deactivation signal when the collision monitoring for an active element WEn 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.
In an embodiment of the proposed method, the collision monitoring for all active elements WEn is deactivated when at least one active element WEn is located at least partly within the assigned region Bn.
The two active elements WEn=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 WEn=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 ABn=1 of the upper gripper jaw 103a represented in
Thus, in the present case, the composed working region AB of the parallel jaw gripper corresponds to all spacings A of the active elements WEn=1,2 103 from A=0 (minimum spacing of the active elements WEn=1,2) up to and including the maximum spacing AMAX=|AMAX,n=1−AMAX,n=2|, which the active elements WEn=1,2 103 can assume with respect to one another (marked AB in
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 Fext,WEn(t), where n=1, 2, . . . , N and N≥1, which are applied externally to the individual active elements WEn=1,2.
In the present case, the sensor system 105 includes a position sensor for ascertaining a motor position qAE of the electric motor, a current sensor for ascertaining a motor current IAE of the electric motor, as well as a torque sensor connected between the transmission 110 and the powertrain 102 for ascertaining the torque τAS. The measurement variables qAE, IAE and τAS are provided to the control unit 104.
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.
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.
The control unit 104 is designed and configured in such a manner that, for the active elements WEn=1,2 103, a collision monitoring can be carried out; the collision monitoring for the active elements WEn=1,2 103 is carried out only when the respective active elements Wn=1,2 103 are located outside of a specified region B located within the working region AB; the collision monitoring for the active elements WEn=1,2 103 is deactivated when the respective active elements WEn=1,2 103 are located at least partly within the region B, and if, for an active element WEn=1,2, a collision is detected, the drive unit 101 is actuated according to a specified operation.
This collision monitoring is in principle carried out independently of control commands, for example, an external robot malfunction.
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 AB, wherein the region B is defined by a spacing A of the active elements WEn=1,2 for which: A<AB or A≤AB and AB<AMAX. In this development, a collision monitoring for the active elements WEn=1,2 is only carried out if the active elements WEn=1,2 have a spacing > or ≥AB. Particularly preferably, the active elements (gripper jaws) of the parallel jaw gripper have no sensors.
In
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.
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.
100 Robot gripper
101 Drive unit
102 Powertrain
103 Active elements WEn
104 Control unit
105 Sensor system
110 Transmission
111 Interface for electrical energy and control signal of an external control unit
112 Control signal line
113 Electrical energy line
201, 202 Method steps
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 107 851.2 | Mar 2019 | DE | national |
The present application is the U.S. National Phase of PCT/EP2020/057544, filed on 19 Mar. 2020, which claims priority to German Patent Application No. 10 2019 107 851.2, filed on 27 Mar. 2019, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/057544 | 3/19/2020 | WO | 00 |
