DE102015220066A1 - Haptic referencing of a manipulator - Google Patents

Abstract

The present invention relates to a method for controlling a robot system, and in particular for aligning a robot system with respect to a reference body. The robot system comprises a manipulator and a manipulator supporting the mobile platform. In this case, a reference position of the platform relative to the reference body and a reference configuration of the manipulator is provided. Furthermore, the manipulator is coupled to the reference body and the robot system is controlled in the coupled state such that the reference configuration of the manipulator is taken.

Description

1. Technical area

The present invention relates to a method for controlling a robot system, and in particular for aligning a robot system to a reference body. Furthermore, the invention relates to a corresponding robot system.

2. Technical background

Robots are freely programmable, program-controlled handling devices that can be used for various activities in assembly or manufacturing processes. The actual mechanics of a robot can be called a manipulator. A manipulator may include various members and axes whose movement may be controlled by driving respective motors, and in particular servomotors.

Manipulators may be provided on mobile platforms which may, for example, move the manipulators through a factory floor. The platforms can be active or passive, that is, have a standalone drive and independent control or not.

In an automatic program sequence, such a mobile manipulator can be moved to a workpiece in order to subsequently process it. When positioning the mobile manipulator, odometry or laser navigation can be used. However, due to inaccuracies of the hardware and software involved in such positioning, accurate homing to the workstation is necessary. It may be a preferred goal of such referencing, to align a manipulator to a workstation such that a defined transformation between a coordinate system of the workstation and a coordinate system of the mobile manipulator is given. An appropriate control is thus known exactly where the mobile manipulator is with respect to the workstation and the component to be processed. Subsequently, an automatic processing step of a robot program can be executed without restrictions.

It is known from in-house methods to identify a positioning error sensor-supported. For this purpose, optical detection systems can be used in conjunction with algorithms for object or environment detection.

The patent US 6,429,016 B1 relates to automatic systems for positioning a sample. A positioning system disclosed therein includes a macro-positioning subsystem and a micro-positioning subsystem. The micro-positioning system is provided between a robot and a workstation to enable a fine mechanical positioning.

The document EP 2 590 787 B1 relates to a method for calibrating a robot. For this purpose, a CAD model is generated by means of a CAD software, and then compared with a second CAD model, which was generated based on 3D measurements.

It is an object of the present invention to provide a method for efficiently referencing a robotic system to e.g. to enable a workstation so that the track or processing points stored during a programming process can be successfully completed. In particular, a method is to be provided which enables an unrestricted automatic and precise application sequence of a mobile manipulator. Cost-intensive external sensors for aligning should preferably be dispensed with here.

These and other objects, which will become apparent from the following description, are achieved by a method according to claim 1 and by a robot system according to claim 11.

3. Content of the invention

The present invention relates to a method for controlling a robot system. In particular, by means of this method, the robot system can be aligned to a workstation at which a work step is to be performed by means of the robot system. The robot system can refer to the workstation. Particularly preferably, the robot system can align itself by means of the method according to the invention to such a workstation and subsequently handle a component based on the orientation. The workstation can include the component.

The robotic system includes a manipulator as well as a mobile platform supporting the manipulator. Preferably, the manipulator is a multi-axis articulated arm robot. The mobile platform may be part of the manipulator, for example a movable manipulator foot. Alternatively, the mobile platform can also be provided as a separate transport system, which can enable an autonomous movement of the manipulator. In particular, the mobile platform may be an omnidirectionally mobile platform. The platform may be passively movable, and may be pushed by an operator, for example. The platform can Also have its own drive and a corresponding control. Preferably, the mobile platform is connected to the manipulator.

The method includes providing a reference body. This reference body can be arranged for example on a workstation or a component, and is preferably fixed in place and provided separately from the manipulator and the mobile platform.

The method further comprises providing a reference position of the platform and a reference configuration of the manipulator. The reference position of the platform may refer to the reference body and may further correspond to a particular transformation between the reference body and the platform. The reference position and the reference configuration may, for example, have been detected during a previous application programming. The reference position of the platform may, for example, comprise a two-dimensional position and an orientation of the platform. The reference configuration of the manipulator may include, for example, an axis configuration of the manipulator or a pose of the manipulator.

The method further includes approximating the platform to the provided reference position of the platform. For this purpose, the mobile platform can be actively controlled, or passively moved by an operator. The approach of the platform can also be done by moving the robot system to the reference body. For example, the platform can be moved here in order to reach the reference position of the platform. The reference position does not have to be reached, in particular can not be reached exactly. For example, such an achievement is often not possible due to positioning errors or even manual inaccuracies.

The method further comprises coupling the manipulator to the reference body. By coupling, a coupled state of the robot system is achieved by e.g. an end effector of the manipulator grips the reference body. In this case, a direct connection between the manipulator and the reference body can be produced. Thus, the mobile platform is connected via the manipulator with the reference body. Preferably, the coupling is a releasable coupling, so that a coupled state can be canceled after a successful referencing.

Furthermore, the method comprises a control of the robot system in the coupled state, so that the reference configuration of the manipulator is taken. For this purpose, the manipulator and / or the mobile platform can be controlled and moved accordingly. The reference body is preferably not moved in this case to counteract a falsified referencing. Due to the existing coupling between the manipulator and the reference body, the manipulator can not move completely free, but is limited due to the coupling in its movement.

Following the activation, the manipulator has assumed the reference configuration. Since the manipulator is coupled to the reference body, thus the position and preferably also the orientation of the manipulator are precisely defined, at least with regard to the reference body. Thus, since the manipulator and platform are connected to each other, preferably also the position of the mobile platform with respect to the reference body is precisely defined. The robot system is thus referenced with respect to the reference body. By means of the manipulator, an application can now be performed, with a high accuracy due to the precise referencing of the robot system. External sensors for referencing are not necessary. In particular, the steps described above can be carried out automatically, for example before or during an automatic execution of an application. Thus, the robot system can autonomously refer to a component by coupling to the reference body and the reference configuration controls.

Preferably, the driving of the robot system in the coupled state further takes place such that the reference position of the mobile platform is taken. For example, when an end effector of the manipulator is coupled to the reference body, and a foot of the manipulator is connected to the mobile platform, the platform associated with the manipulator may assume the reference position as a result of driving the robotic system so that the manipulator assumes the reference configuration. For this purpose, the mobile platform can be moved as a passive element through the manipulator, so be pushed into the reference position. As an active element, the mobile platform can be controlled accordingly to follow a guidance of the manipulator. For this purpose, a controller of the manipulator may be connected to a corresponding controller of the manipulator. Further, the mobile platform may include sensors that detect forces exerted by the manipulator on the platform as a result of the driving. According to this data, the mobile platform can drive its drives to follow the manager of the manipulator.

In the reference position are the position and preferably also the orientation of the mobile platform with respect to the reference body or precisely defined with regard to the component. The coordinate system of the manipulator, which itself may be defined with regard to the mobile platform, is thus assigned precisely to the reference position of the mobile platform. By means of appropriate transformation, the manipulator can therefore precisely edit a component whose position is stored with respect to the reference body.

Preferably, in the coupled state, there is a connection between the manipulator and the reference body. In particular, preferably there is a mechanical or magnetic connection between the manipulator and the reference body. Based on this connection, the robot system can align itself if it is driven accordingly, while the manipulator is still connected to the reference body and thus has a fixed reference point, by which the movement takes place as a result of the driving. When coupling, for example, a magnetic coupling device of the manipulator can be moved efficiently by means of magnetic tensile forces to a ferrous reference body.

Preferably, an intermediate position of the platform is achieved as a result of approaching the platform to the reference position of the platform. This intermediate position is typically different from the reference position of the platform. The robot system therefore does not have to be precisely approximated to the reference position of the platform, since the precise alignment or referencing takes place automatically later by means of the manipulator. For example, a worker may manually move the robot system near the reference body and near the reference position of the mobile platform. The platform reaches the intermediate position. In order to be able to carry out a precise execution of a programmed application, the platform is first automatically brought into the reference position by means of the manipulator.

Preferably, the method further comprises detecting forces and moments acting on the robot system. During the approach of the platform and / or during the coupling of the manipulator while the robot system and in particular preferably the manipulator is operated by means of a force control using the detected forces and moments. The force control can be a compliance control, and in particular by means of an impedance, an admittance, a position or torque control. With such a compliance control, the robot system may be at least partially soft-wired and may be controlled according to external forces, so that the external forces acting on the robot system are reduced due to a corresponding movement of the robot system. This allows the manipulator to couple to the reference body without damaging the manipulator and / or the reference body. In particular, a haptic coupling can take place in which the manipulator recognizes the reference body and couples it to it. The approach of the platform to the reference position can also take place in such a way that a collision between the robot system and, for example, a workstation on which the reference body can be located is prevented. Thus, a haptic referencing can be made possible.

Preferably, the coupling of the manipulator to the reference body comprises a frictional coupling. In particular, as a result of the coupling, there is preferably a frictional connection between the manipulator and the reference body. Thus, the robot system can align itself as a result of the drive while it is in the coupled state. For example, the manipulator may refer to or push away from the reference body to assume the reference configuration. The reference body is accordingly fixed and dimensioned sufficiently rigid.

Preferably, the coupling of the manipulator to the reference body comprises a positive coupling. In particular, as a result of the coupling, there is preferably a positive connection between the manipulator and the reference body. By this positive locking can be precisely ensured that in the coupled state, a certain predefined orientation between the coupled manipulator and the reference body is present, so easily the reference configuration of the manipulator and the reference position of the mobile platform can be achieved.

Preferably, the coupling of the manipulator to the reference body takes place such that a coupling device of the manipulator is in a predefined orientation relative to the reference body. In particular, the coupling device may comprise an end effector of the manipulator. In this case, the end effector form the coupling device. The coupling device or the end effector in the coupled state is preferably in a predefined position and orientation relative to the reference body. By driving the robot system in the coupled state can thus be achieved efficiently a predefined reference configuration and reference position.

In particular, the coupling of the manipulator to the reference body preferably takes place such that a coding of the coupling device of the manipulator is coupled with a corresponding counter-coding of the reference body or agrees accordingly. The coding and counter-coding may be based on structural features and, for example, due to the key-lock principle, prevent the manipulator from coupling to an incorrect location. Thus, it can be ensured efficiently that the manipulator is coupled to the correct reference body, and that the coupled manipulator stands in a desired orientation to the reference body. For this purpose, the coding and counter-coding can be present for example as three-dimensional coding and Gegenkodierflächen, which can only interlock when a certain orientation of the surfaces to each other is present.

Preferably, providing the reference position of the platform and the reference configuration of the manipulator comprises moving the mobile platform to a position where the manipulator can reach the reference body, coupling the manipulator to the reference body, and detecting the position as the reference position of the platform and the configuration of the manipulator in the coupled state as the reference configuration of the manipulator. These steps are preferably performed during application programming, and may be at least partially performed manually by a programmer. Subsequently, certain application steps can be programmed, such as the storage of a specific gripping point. By means of the method, it is ensured that during an automatic execution of the application exact referencing information is available, by means of which the robot system can precisely refer automatically, so that the following application steps can be carried out precisely. It is thus ensured in particular that, starting from the reference configuration, the manipulator can also carry out the following application steps as defined during the application programming in automatic mode.

Furthermore, the present invention comprises a robot system comprising a manipulator and a manipulator-supporting mobile platform. Preferably, the manipulator is a multi-axis articulated arm robot. In particular, the multi-axis articulated-arm robot is preferably designed as a lightweight robot. Furthermore, the robot system has a controller configured to perform a method of controlling the robot system described above. One skilled in the art will understand that the robotic system may include corresponding means for performing such a method, such as a coupling device. In this case, the robot system preferably comprises sensors for detecting forces and moments acting on the robot system and in particular on the manipulator. For this purpose, 6-axis force-moment sensors can be used, which can detect force and torque components acting on the manipulator based on strain gauges or strain gauges.

4th embodiments

In the following, the present invention will be described in detail with reference to the accompanying drawings. Showing:

1 - 5 a robot system according to an embodiment in different constellations.

In the 1 a robot system is shown comprising a manipulator 4 and a mobile platform 3 which the manipulator 4 supports. The mobile platform can be moved in x- and y-direction, and thus the manipulator 4 move. The mobile platform 3 can be an omnidirectionally mobile platform that can be pushed as a passive platform by a worker. Preferably, the axes of the platform are actively driven, so that the platform can move programmatically automatically and autonomously. For this purpose, the mobile platform may include navigation means, such as lasers. An actively driven platform can also passively be pushed by a worker while the brakes are released.

The manipulator 4 is designed as a multi-axis articulated arm robot, on whose hand flange a gripper 5 and a coupling device 6 are provided in the form of a loop. Furthermore, in the 1 a workstation 1 shown. At this is a contact device 2 to which the coupling device 6 of the manipulator 4 is coupled. The contact device 2 represents the reference body in the context of the invention.

In the following the exemplary procedure of an application programming with reference to the 1 and 2 described. First, the mobile platform is moved to a position 7a moves, in which the manipulator 4 with its coupling device 6 the contact device 2 can reach. In the case of a passive design of the platform 3 can do this manually to the workstation 1 be pushed. In the case of an actively driven platform 3 This can be done in manual mode, for example by means of a remote control, in front of the workstation 1 to be moved.

Subsequently, the manipulator 4 to the contact device 2 as in 1 shown coupled. For this purpose, the manipulator is manually to the workstation 1 approximated, and then by means of the coupling device 6 to the contact device 2 connected. There is a positive connection 8th between the contact device 2 and the coupling device 6 of the manipulator 4 in front.

Subsequently, the position 7a the mobile platform 3 comprising the translational components xa, ya and the rotational component θa as the reference position of the mobile platform 3 saved. Likewise, the axis configuration becomes α1, β1, γ1, ε1 of the manipulator 4 stored in the coupled state as the reference configuration of the manipulator.

Like in the 2 then an application can be programmed. For this purpose, first the coupling between the manipulator 4 and the contact device 2 solved. The mobile platform 3 was this not moved in the illustrated embodiment and is still - with activated brakes - at the position 7a , The configuration of the manipulator 4 was changed according to the application to be programmed, and among other things a gripping point 9 at the workstation 1 saved. For this purpose, the corresponding axis coordinates α2, β2, γ2, ε2 of the manipulator to the gripping point 9 get saved.

The following is the automatic execution of the programmed application with reference to the 3 - 5 described. For this purpose, first the mobile platform 3 that was previously at another work site, for example, to the reference position 7a approximated to the platform. This can for example be done automatically by autonomous navigation or by manual pushing. Due to positioning errors, however, typically only a different intermediate position 7b reached with the coordinates xb, yb, θb. If the programmed application would now be carried out without referencing, it would not be ensured that the path points to be approached, with regard to the workstation 1 are defined, precisely or due to axial limits can be achieved with the manipulator at all. For example, a position can not be approached with sufficient accuracy or can not be achieved due to axle limits. Furthermore, due to the changed initial configuration and the resulting singularities, a linear movement can not be carried out. Furthermore, this could set a singularity of Achsstellung, so that under certain circumstances, a gripping position can not be achieved.

As in 4 Therefore, the coupling device is initially displayed by means of an automatic search operation of the manipulator 6 of the manipulator 4 to the contact device 2 the workstation 1 coupled. For this purpose, the manipulator 4 be operated by means of compliance control, so that the positive connection 8th between coupling device 6 and contact device 2 can be achieved easily. In this coupled state, there is a configuration of the manipulator with, for example, the axis coordinates α3, β3, γ3, ε3.

Subsequently, the positioning error of the mobile platform 3 corrected. When the mobile platform 3 is a passive powered platform, the manipulator can 4 be controlled directly in the Referenzachskonfiguration α1, β1, γ1, ε1. This will be the mobile platform 3 that stuck with the manipulator 4 connected, in the associated reference position xa, ya, θa out or pulled, as in 5 shown. Subsequently, the coupling can be solved and the following application step can be performed. The base of the manipulator is now in the same place as in the application programming, so that the programmed movement of the manipulator can be performed as desired.

If the platform 3 is an actively driven platform, via an inverse kinematics, which includes all degrees of freedom of the entire system, both the reference configuration α1, β1, γ1, ε1 of the manipulator and the reference position xa, ya, θa of the platform can be controlled by a zero space movement. Subsequently, the coupling can be released and the following application step can be carried out, without any repositioning of the platform being required in order to execute the previously programmed application program.

LIST OF REFERENCE NUMBERS

1

 workstation

2

 Contact device, reference body

3

 mobile platform

4

 manipulator

5

 end effector

6

 coupling device

7a, 7b

 Position of the mobile platform

8th

 connection

9

 gripping point

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6429016 B1 [0006]
• EP 2590787 B1 [0007]

Claims (13)

Method for controlling a robot system, wherein the robot system includes a manipulator ( 4 ) and a manipulator ( 4 ) supporting mobile platform ( 3 ), the method comprising the following steps: providing a reference body ( 2 ); Providing a reference position ( 7a ) of the platform ( 3 ) and a reference configuration of the manipulator ( 4 ); Approaching the platform ( 3 ) to the reference position ( 7a ) of the platform ( 3 ); Coupling the manipulator ( 4 ) to the reference body ( 2 ); and driving the robot system in the coupled state, so that the reference configuration of the manipulator ( 4 ) is taken. The method of claim 1, wherein the driving of the robot system in the coupled state further takes place such that the reference position ( 7a ) of the mobile platform ( 3 ) is taken. Method according to claim 1 or 2, wherein in the coupled state a mechanical and / or magnetic connection ( 8th ) between the manipulator ( 4 ) and the reference body ( 2 ) is present. Method according to one of claims 1 to 3, wherein as a result of approaching the platform ( 3 ) to the reference position ( 7a ) of the platform ( 3 ) an intermediate position ( 7b ) of the platform ( 3 ) different from the reference position ( 7a ) of the platform ( 3 ). Method according to one of claims 1 to 4, further comprising detecting acting on the robot system forces and moments, and wherein the robot system and preferably the manipulator ( 4 ) is operated by means of a force control, in particular compliance control, using the detected forces and moments, during the approach of the platform (FIG. 3 ) and / or during the coupling of the manipulator ( 4 ). Method according to one of claims 1 to 5, wherein the coupling of the manipulator ( 4 ) to the reference body ( 2 ) comprises a frictional coupling, and wherein as a result of the coupling preferably a frictional connection ( 8th ) between the manipulator ( 4 ) and the reference body ( 2 ) is present. Method according to one of claims 1 to 6, wherein the coupling of the manipulator ( 4 ) to the reference body ( 2 ) comprises a positive coupling, and wherein as a result of the coupling, preferably a positive connection ( 8th ) between the manipulator ( 4 ) and the reference body ( 2 ) is present. Method according to one of claims 1 to 7, wherein the coupling of the manipulator ( 4 ) to the reference body ( 2 ) such that a coupling device ( 5 . 6 ) of the manipulator ( 4 ) and preferably an end effector ( 5 ) of the manipulator ( 4 ) in a predefined orientation relative to the reference body ( 2 ). Method according to claim 8, wherein the coupling of the manipulator ( 4 ) to the reference body ( 2 ) is performed such that a coding of the coupling device ( 5 . 6 ) of the manipulator ( 4 ) with a corresponding counter-coding of the reference body ( 2 ) couples. Method according to one of claims 1 to 9, wherein the provision of the reference position ( 7a ) of the platform ( 3 ) and the reference configuration of the manipulator ( 4 ) includes the following steps: moving the mobile platform ( 3 ) to a position in which the manipulator ( 4 ) the reference body ( 2 ) can reach; Coupling the manipulator ( 4 ) to the reference body ( 2 ); and detecting the position as the reference position ( 7a ) of the platform ( 3 ) and the configuration of the manipulator ( 4 ) in the coupled state as the reference configuration of the manipulator ( 4 ). Robot system comprising a manipulator ( 4 ), a manipulator ( 4 ) supporting mobile platform ( 3 ), and further a controller configured to perform a method according to any of the steps 1 to 10 for controlling the robot system. A robot system according to claim 11, further comprising sensors for detecting on the robot system and in particular on the manipulator ( 4 ) acting forces and moments. Method according to one of claims 1 to 10 or robot system according to claim 11 or 12, wherein the manipulator ( 4 ) is a multi-axis articulated robot.

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