Robot arm calibration

Abstract

The invention relates to a method for calibrating a robot arm with the aid of a measuring device that has a first calibration element and a calibration element which is fixed to the robot arm and which can be moved relative to the first calibration element by adjusting joints of the robot arm, wherein the first calibration element and the calibration element fixed to the robot arm are designed such that in the event of a displacement of the calibration element fixed to the robot arm relative to the first calibration element in an advance direction, the calibration element fixed to the robot arm is guided by the first calibration element from various starting positions to the same defined end position, said method comprising the following steps: positioning (S10) the calibration element fixed to the robot arm relative to the first calibration element in one of the starting positions; moving (S20), in a force-controlled manner, the calibration element fixed to the robot arm relative to the first calibration element in the advance direction with the aid of the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the first calibration element to the end position and thereat the robot has a calibration setting; detecting (S30) joint settings of the robot arm in the calibration setting; and calibrating (S110) the robot arm on the basis of these joint settings.

Description

[0001] Description

[0002] Robot arm calibration

[0003] The present invention relates to a method for calibrating a robot arm and to a system, computer program or computer program product for carrying out a method described here.

[0004] The object of the present invention is to improve the calibration of a robot arm.

[0005] This object is achieved by a method having the features of claim 1. Claims 9 and 10 represent a system or computer program or.

[0006] A computer program product for carrying out a method described herein is protected. The subclaims relate to advantageous developments.

[0007] According to one embodiment of the present invention, a robot arm has several, preferably at least three, in particular at least six, in one embodiment at least seven, joints or (movement) axes, in one embodiment rotary joints.

[0008] According to one embodiment of the present invention, a measuring device has at least two calibration elements, each of which can be formed in one or more parts.

[0009] In one embodiment, one of the calibration elements is a calibration element fixed to the robot arm and, in a further development, is arranged in a stationary manner, in one embodiment (non-destructively) detachable, in another embodiment (non-destructively) non-detachable or permanently, on the robot arm, preferably its (distal) end or tool flange or member.

[0010] The calibration element(s) is referred to in one embodiment, without limitation of generality, as the first calibration element. In one embodiment, this calibration element is fixed relative to a rigid or mobile environment and / or the base of the robot arm; in one embodiment, it is detachable (non-destructively); and in another embodiment, it is non-detachable or permanently arranged on the environment or the robot arm base.

[0011] The calibration element fixed to the robot arm is movable relative to the first calibration element by adjusting the joints of the robot arm, wherein the first and the calibration elements fixed to the robot arm are designed such that when the calibration element fixed to the robot arm is displaced relative to the first calibration element in a spatial direction, which is referred to here without restriction of generality as the first feed direction, the calibration element fixed to the robot arm is (forced) from various starting positions, which are referred to here without restriction of generality as the first starting positions, by the first calibration element, preferably mechanically or positively, (ultimately) in each case into the same, in particular clearly defined, preferably singular or unambiguous, end position, which is referred to here without restriction of generality as the first end position.A simple and at the same time preferred example is a funnel for guiding a ball: When the ball is moved into the funnel relative to the funnel, it contacts the surface of the funnel. Upon subsequent further movement into the funnel, the funnel guides the ball inward to a defined end position. This can preferably be achieved by a ball fixed or guided to the robot arm, but of course also by moving the funnel fixed to the robot arm relative to the ball fixed to the surroundings.

[0012] According to one embodiment of the present invention, the method for calibrating the robot arm using the measuring device comprises the steps:

[0013] - Positioning the calibration element fixed to the robot arm relative to the first

[0014] Calibration element using the robot arm in one of the first starting positions;

[0015] - force-controlled movement, preferably using impedance control of the robot arm, of the calibration element fixed to the robot arm relative to the first calibration element in the first feed direction using the robot arm, wherein during this (force-controlled) movement, the calibration element fixed to the robot arm is (forcedly) guided into the first end position by the first calibration element, preferably mechanically or positively, and the robot has a calibration position in this first end position, which is referred to herein without restriction of generality as the first calibration position; - detecting positions of the joints of the robot arm in the first calibration position, in one embodiment using sensors on the joints, which are referred to herein without restriction of generality as the first positions; and

[0016] - Calibrating the robot arm on the basis of these first joint positions, in particular on the basis of the first joint positions and the known, preferably predetermined and / or measured, first end position, wherein the first end position in one embodiment is known, preferably predetermined and / or measured, relative to the robot arm, in particular its base, and / or relative to an environment of the robot arm, in particular a base of the measuring device.

[0017] By means of the force-controlled, in one embodiment impedance-controlled movement of the calibration element fixed to the robot arm by means of the robot arm in conjunction with the (forced) guidance by the first calibration element, in one embodiment the calibration element fixed to the robot arm can advantageously be arranged in the first end position reliably, precisely, quickly and / or in different guidance directions, for example also horizontally or vertically upwards or the like, and this can be used to calibrate the robot arm.

[0018] In one embodiment, the measuring device has at least one further calibration element, which is referred to as a second calibration element without restriction of generality and is also arranged on the environment or robot arm base in a stationary manner relative to the environment and / or base of the robot arm, in one embodiment detachable (non-destructively), in another embodiment (non-destructively) non-detachable or permanent.

[0019] The calibration element fixed to the robot arm can also be moved relative to the second calibration element by adjusting the joints of the robot arm, in particular after it has initially been arranged in the first end position and then moved away from this again, wherein the second and the calibration element fixed to the robot arm are designed such that when the calibration element fixed to the robot arm is displaced relative to the second calibration element in a spatial direction, which is referred to here without restriction of generality as the second feed direction, the calibration element fixed to the robot arm is (forcedly) guided from different starting positions, which are referred to here without restriction of generality as second starting positions, by the second calibration element, preferably mechanically or positively, into the same defined end position, which is referred to here without restriction of generality as the second end position.

[0020] In a further development of this embodiment, the method with respect to the second calibration element comprises the same steps as described above with respect to the first calibration element, or the steps:

[0021] - positioning the calibration element fixed to the robot arm relative to the second calibration element with the aid of the robot arm in one of the second starting positions, preferably after it has first been moved into the first end position with the aid of the robot arm, in which the first positions and, if applicable, the further positions of the joints of the robot arm have been detected and then the calibration element fixed to the robot arm has been moved away from the first end position again, in particular out of the first calibration element;

[0022] - force-controlled movement of the calibration element fixed to the robot arm relative to the second calibration element in the second feed direction by means of the robot arm, wherein during this (force-controlled) movement the calibration element fixed to the robot arm is (forced) guided into the second end position by the second calibration element, preferably mechanically or positively, and the robot has a calibration position in this end position, which is referred to here without restriction of generality as the second calibration position; and

[0023] - Detecting positions of the joints of the robot arm in the second calibration position, which are referred to herein as second positions without restriction of generality; wherein the robot arm is calibrated on the basis of the first and also these second joint positions, preferably also on the basis of the known, in one embodiment predetermined and / or measured, second end position, wherein the second end position in one embodiment is known, preferably predetermined and / or measured, relative to the robot arm, in particular its base, and / or relative to an environment of the robot arm, in particular a base of the measuring device.

[0024] In a further development, the measuring device has at least one further

[0025] Calibration element, which is referred to without restriction of generality as a further second or third calibration element and, in one embodiment, is also fixed relative to the environment and / or base of the robot arm, in one embodiment (non-destructively) detachable, in another embodiment (non-destructively) non-detachable or permanent, arranged on the environment or robot arm base.

[0026] The calibration element fixed to the robot arm can also be moved relative to the third or further second calibration element by adjusting the joints of the robot arm, in particular after it has initially been arranged in the first end position, then moved away from this again and arranged in the (one) second end position and then moved away from this again, wherein this third or further second calibration element and the calibration element fixed to the robot arm are designed in such a way that when the calibration element fixed to the robot arm is moved relative to the third or further second calibration element in a spatial direction, which is referred to here without restriction of generality as the third or further second feed direction, the calibration element fixed to the robot arm can be moved from different starting positions, which are referred to here without restriction of generality as the third or further second starting positions, by the third or further second calibration element.a further second calibration element is (forcedly) guided, preferably mechanically or positively, into the same defined end position, which is referred to here without restriction of generality as the third or further second end position.

[0027] In a further development of this embodiment, the method comprises the same steps as described above with reference to the first and (a) second calibration element or the steps:

[0028] - positioning the calibration element fixed to the robot arm relative to the third or further second calibration element with the aid of the robot arm in one of the third or further second start positions, preferably after it has first been moved with the aid of the robot arm into the first end position, in which the first positions and, if applicable, the further positions of the joints of the robot arm have been recorded, and then the calibration element fixed to the robot arm has been moved away from the first end position again, in particular out of the first calibration element, and then moved with the aid of the robot arm into the (one) second end position, in which the (one) second positions and, if applicable, further positions of the joints of the robot arm have been recorded, and then the calibration element fixed to the robot arm has been moved away from the (one) second end position again, in particular out of the (one) second calibration element;

[0029] - force-controlled movement of the calibration element fixed to the robot arm relative to the third or further second calibration element in the third or further second feed direction by means of the robot arm, wherein during this (force-controlled) movement the calibration element fixed to the robot arm is (forced) guided by the third or further second calibration element, preferably mechanically or positively, into the third or further second end position and the robot has a calibration position in this end position, which is referred to here without restriction of generality as the third or further second calibration position; and

[0030] - Detecting positions of the joints of the robot arm in the third or further second calibration position, which are referred to herein without restriction of generality as third or further second positions; wherein the robot arm is calibrated on the basis of the first, the (one) second and also this third or further second joint position, preferably also on the basis of the known, in one embodiment predetermined and / or measured, third or further second end position, wherein this third or further second end position is known, preferably predetermined and / or measured, in one embodiment relative to the robot arm, in particular its base, and / or relative to an environment of the robot arm, in particular a base of the measuring device.

[0031] By means of one or more second calibration elements, which are preferably spaced (arranged) from one another and / or the first calibration element, the calibration, in particular its precision, can be improved and / or more dimensions or parameters can be determined in one embodiment.

[0032] In one embodiment, the method comprises the steps:

[0033] - Adjusting the robot arm from the first calibration position into at least one further calibration position in which the calibration element fixed to the robot arm is (likewise) arranged in the first end position, wherein the calibration element fixed to the robot arm preferably remains arranged in the first end position during this adjustment with the aid of the force-controlled robot arm or is guided back into the first end position by the first calibration element during force-controlled movement of the calibration element fixed to the robot arm relative to the first calibration element in the first feed direction; and

[0034] - Detecting further positions of the joints of the robot arm in this further calibration position; whereby the robot arm is calibrated on the basis of the first and these further joint positions.

[0035] Additionally or alternatively, the method in one embodiment comprises the steps:

[0036] - Adjusting the robot arm from the or at least one of the second calibration positions into at least one further calibration position in which the calibration element fixed to the robot arm is arranged in the second end position in which it was arranged in this second calibration position, wherein the calibration element fixed to the robot arm preferably remains arranged in this second end position during this adjustment with the aid of the force-controlled robot arm or is guided back into the (respective) second end position by the corresponding second calibration element during force-controlled movement of the calibration element fixed to the robot arm relative to this second calibration element in the (respective) second feed direction; and

[0037] - Detecting further positions of the joints of the robot arm in this further calibration position; whereby the robot arm is also calibrated based on these further joint positions.

[0038] In one embodiment, different calibration or joint positions of the robot arm can be detected in the same or for the same end position and used for calibration, thereby improving in particular the calibration, in particular its precision, and / or time and / or space requirements and / or determining more dimensions or parameters.

[0039] In one embodiment, when adjusting the robot arm from the first calibration position to a further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position, when adjusting the robot arm between at least two calibration positions A, B of the robot arm, one of which can be the first calibration position or both calibration positions can be different from the first calibration position, the calibration element fixed to the robot arm is arranged in the first end position and an orientation of the calibration element fixed to the robot arm relative to the first calibration element is maintained (during this adjustment of the robot arm between the two calibration positions A, B of the robot arm), during the detection, positions of the joints of the robot arm in these at least two calibration positions A, B are detected, and the robot arm is (also) calibrated on the basis of these detected positions of the joints.

[0040] Additionally or alternatively, in one embodiment, when adjusting the robot arm from the or at least one of the second calibration positions to the or at least one of the further calibration positions, in which the calibration element fixed to the robot arm is arranged in the (respective) second end position in which it was arranged in this (respective) second calibration position, when adjusting the robot arm between at least two calibration positions A', B' of the robot arm, one of which can be the (respective) second calibration position or both calibration positions can be different from the (respective) second calibration position, the calibration element fixed to the robot arm is arranged in the (respective) second end position and an orientation of the calibration element fixed to the robot arm relative to the (respective) second calibration element is maintained (during this adjustment of the robot arm between the two calibration positions A', B' of the robot arm).During the detection, positions of the joints of the robot arm are detected in these at least two calibration positions A', B', and the robot arm is (also) calibrated on the basis of these detected positions of the joints.

[0041] Thus, in one embodiment, the robot arm (in each case) is adjusted in such a way that it not only maintains the position but also the orientation of the calibration element fixed to the robot arm relative to the respective calibration element, or adjusts it in its corresponding zero space.

[0042] In one embodiment, this allows for particularly advantageous calibration of additional joint positions, preferably with less load on the calibration elements. Additionally or alternatively, in one embodiment, such adjustment of the robot arm in its corresponding zero space allows for additional joint positions to be used for calibration.Additionally or alternatively, in one embodiment, when adjusting the robot arm from the first calibration position into a further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position, in at least two calibration positions U, V of the robot arm, one of which can be the first calibration position or both calibration positions can be different from the first calibration position, the calibration element fixed to the robot arm is arranged in the first end position and the calibration element fixed to the robot arm has different orientations relative to the first calibration element in these at least two calibration positions U, V.During this adjustment of the robot arm between the two calibration positions U, V of the robot arm, its orientation relative to the first calibration element changes, during the detection, positions of the joints of the robot arm in these at least two calibration positions U, V are detected, and the robot arm is (also) calibrated on the basis of these detected positions of the joints.

[0043] Additionally or alternatively, in one embodiment, when adjusting the robot arm from the or at least one of the second calibration position(s) into the or at least one of the further calibration position(s), in which the calibration element fixed to the robot arm is arranged in the (respective) second end position in which it was arranged in this (respective) second calibration position, in at least two calibration positions LT, V' of the robot arm, one of which can be the (respective) second calibration position or both calibration positions can be different from the (respective) second calibration position, the calibration element fixed to the robot arm is arranged in the (respective) second end position and the calibration element fixed to the robot arm has different orientations relative to the (respective) second calibration element in these at least two calibration positions U', V'.During this adjustment of the robot arm between the two calibration positions LT, V' of the robot arm, its orientation relative to the (respective) second calibration element changes. During the detection, the positions of the joints of the robot arm in these at least two calibration positions LT, V' are detected, and the robot arm is (also) calibrated based on these detected joint positions. Thus, in one embodiment, only the position of the calibration element fixed to the robot arm is maintained relative to the respective calibration element, but its orientation relative to the respective calibration element is changed.

[0044] As a result, in one embodiment, additional joint positions can advantageously be approached for calibration more easily and / or more precisely and / or additional joint positions can be used for calibration, in particular if the robot arm does not have a corresponding zero space in the corresponding starting (calibration) position.

[0045] Particularly advantageously, the two variants mentioned above can be combined with one another, in particular sequentially, in particular by adjusting the robot arm between two calibration positions in which the calibration element fixed to the robot arm has different orientations relative to the respective calibration element, but the same position, the robot arm is then adjusted while maintaining the position and orientation, and / or by adjusting the robot arm between two calibration positions in which the calibration element fixed to the robot arm has the same position and orientation relative to the respective calibration element, the robot arm is then adjusted while maintaining the position and changing the orientation.

[0046] This allows additional joint positions to be used for calibration, thereby improving the calibration process, particularly its precision and / or speed. It can be particularly advantageous to move to more than two calibration positions while maintaining the position and orientation of the calibration element fixed to the robot arm relative to the respective calibration element, and to use the joint positions detected in these calibration positions for calibration.

[0047] In one embodiment, the robot arm is force-controlled in the first calibration position, in a further development during an adjustment from the first calibration position to the further calibration position and / or at least during the detection of the joint positions in the first and / or this further calibration position, such that the calibration element fixed to the robot arm exerts a contact force on the first calibration element in the first end position and is supported by the first calibration element in the first end position.

[0048] Additionally or alternatively, the robot arm is force-controlled in the or at least one of the second calibration positions, in a further development when adjusting from the or at least one of the second calibration positions into the corresponding further calibration position and / or at least during the detection of the joint positions in the (respective) second and / or this further calibration position, such that the calibration element fixed to the robot arm exerts a contact force on the respective second calibration element in the (respective) second end position and is supported by the respective second calibration element in the (respective) second end position.

[0049] In one embodiment, the calibration element fixed to the robot arm can thereby advantageously be secured in its respective end position and thus in particular the calibration, in particular its precision, and / or the time required can be improved.

[0050] In one embodiment, the first calibration element has a guide surface with a cavity, wherein the calibration element fixed to the robot arm can be supported by the cavity in a defined support position which determines the first end position, wherein the guide surface converges towards the cavity, preferably in a funnel-like manner.

[0051] In a further development, the or one or more of the second calibration element(s) each have a guide surface with a cavity, wherein the calibration element fixed to the robot arm can be supported by the (respective) cavity in a defined support position that determines the (respective) second end position, wherein the guide surface converges towards the cavity, preferably in a funnel-like manner. Additionally or alternatively, the calibration element fixed to the robot arm has an at least partially spherical or (partially) spherical contact or surface for sliding on the (respective) guide surface. Additionally or alternatively, in one embodiment, the or one or more of the guide surfaces each have one or more guides that are designed to guide the calibration element fixed to the robot arm into the (respective) cavity along (respective) a one-dimensional, preferably at least partially straight, guide path.In another embodiment, conversely, the calibration element fixed to the robot arm has a guide surface with a cavity, wherein the first calibration element can be supported by the cavity in a defined support position which determines the first end position, wherein the guide surface converges towards the cavity, preferably in a funnel-like manner.

[0052] In a further development, the first calibration element and, in one embodiment, also the second calibration element(s) each have an at least partially spherical or (partially) spherical contact or surface for sliding on this guide surface. Additionally or alternatively, in one embodiment, the guide surface has one or more guides designed to guide the first or (respective) second calibration element fixed to the robot arm into the (respective) cavity along (respective) a one-dimensional, preferably at least partially straight, guide path.

[0053] In one embodiment, this can improve the mechanical or form-fitting guidance or calibration, in particular its precision, and / or time and / or space requirements.

[0054] In one embodiment, the method comprises the step:

[0055] - force-controlled movement of the calibration element fixed to the robot arm relative to the first calibration element using the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the guide along the guideway and positions of the joints of the robot arm are detected in at least two calibration positions; wherein the robot arm is calibrated on the basis of these joint positions.

[0056] In a further training, the procedure includes the following steps:

[0057] - force-controlled movement of the calibration element fixed to the robot arm relative to the or one or more of the second calibration elements using the robot arm, wherein during this movement, the calibration element fixed to the robot arm is guided along the guideway by the (respective) guide, and positions of the joints of the robot arm are detected in at least two calibration positions; wherein the robot arm is calibrated based on these joint positions. In one embodiment, the or one or more of the guides (each) have at least one edge, preferably a groove, in the guide surface.

[0058] In one embodiment, the (respective) guide provides a defined direction, which can be detected by the at least two calibration positions and thus advantageously used for calibration. This can improve calibration, in particular its precision, and / or time and / or space requirements.

[0059] According to one embodiment of the present invention, a system, in particular hardware and / or software, in one embodiment programmatically, is set up to carry out a method described here.

[0060] According to one embodiment of the present invention, a system comprises a measuring device as described here and can in particular consist of this.

[0061] Additionally or alternatively, according to an embodiment of the present invention, a or the system has a control which, in particular hardware and / or software, in one embodiment programmatically, for

[0062] - controlling the robot arm to position the calibration element fixed to the robot arm relative to the first calibration element using the robot arm in one of the first starting positions;

[0063] - controlling the robot arm for the force-controlled movement of the calibration element fixed to the robot arm relative to the first calibration element in the first feed direction using the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the first calibration element into the first end position and the robot has a first calibration position in this end position; and

[0064] - detecting first positions of the joints of the robot arm in the first calibration position, preferably with the aid of corresponding sensors; can in particular consist of this.

[0065] Additionally or alternatively, according to an embodiment of the present invention, a system or the system, in particular its controller, has a calibration means for calibrating the robot arm on the basis of the detected first joint positions, and can in particular consist of this.

[0066] In one embodiment, in particular hardware and / or software, in one embodiment programmatically, the control for

[0067] - controlling the robot arm to position the calibration element fixed to the robot arm relative to the second calibration element using the robot arm in one of the second starting positions;

[0068] - controlling the robot arm for the force-controlled movement of the calibration element fixed to the robot arm relative to the second calibration element in the second feed direction using the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the second calibration element into the second end position and the robot has a second calibration position at this end position; and

[0069] - detecting second positions of the joints of the robot arm in the second calibration position, preferably using corresponding sensors; and / or the calibration means is configured to calibrate the robot arm based on the first and second joint positions.

[0070] In one embodiment, in particular hardware and / or software, in one embodiment programmatically, the control for

[0071] - controlling the robot arm to adjust the robot arm from the first calibration position into at least one further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position; and

[0072] - detecting further positions of the joints of the robot arm in this further calibration position, preferably using corresponding sensors; and / or the calibration means is configured to calibrate the robot arm based on these further joint positions.

[0073] In one embodiment, in particular hardware and / or software, in one embodiment programmatically, the control is set up so that

[0074] - when adjusting the robot arm from the first calibration position to a further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position, when adjusting the robot arm between at least two calibration positions of the robot arm, the calibration element fixed to the robot arm is arranged in the first end position and an orientation of the calibration element fixed to the robot arm relative to the first calibration element is maintained, and during the detection, positions of the joints of the robot arm in these at least two calibration positions are detected; and / or

[0075] - when adjusting the robot arm from the first calibration position into a further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position, in at least two calibration positions of the robot arm the calibration element fixed to the robot arm is arranged in the first end position and the calibration element fixed to the robot arm has different orientations relative to the first calibration element in these at least two calibration positions, and during the detection, positions of the joints of the robot arm are detected in these at least two calibration positions, and / or the calibration means is set up to calibrate the robot arm on the basis (also) of these detected joint positions.

[0076] In one embodiment, in particular hardware and / or software, in one embodiment programmatically, the control for

[0077] - Controlling the robot arm for force-controlled movement of the calibration element fixed to the robot arm relative to the first calibration element using the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the guide along the guideway and positions of the joints of the robot arm in at least two calibration positions are detected, preferably using corresponding sensors; and / or the calibration means is configured to calibrate the robot arm in these joint positions.

[0078] A system and / or means within the meaning of the present invention can be designed in hardware and / or software, in particular at least one, in particular digital, processing unit, in particular a microprocessor unit (CPU), graphics card (GPU) or the like, preferably connected to a memory and / or bus system for data or signals, and / or one or more programs or program modules. The processing unit can be designed to execute instructions implemented as a program stored in a memory system, to detect input signals from a data bus, and / or to output signals to a data bus. A memory system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state, and / or other non-volatile media. The program can be designed in such a way that it embodies the methods described here oris capable of executing such a method, so that the processing unit can carry out the steps of such methods and thus, in particular, can control and / or calibrate the robot arm. Controlling in the sense of the present invention is understood to mean, in particular, regulating or commanding on the basis of a deviation between target and actual values. In one embodiment, a computer program product can have, in particular be, a storage medium, in particular a computer-readable and / or non-volatile one, for storing a program or instructions or with a program or instructions stored thereon. In one embodiment, execution of this program or these instructions by a system or a controller, in particular a computer or an arrangement of several computers, causes the system or the controller, in particular the computer(s), to execute a method or instructions described here.to carry out one or more of its steps, or the program or instructions are set up to do so.

[0079] In one embodiment, one or more, in particular all, steps of the method are fully or partially computer-implemented or one or more, in particular all, steps of the method are fully or partially automated, in particular by the system or its means.

[0080] In one version, the system has the robot arm.

[0081] Calibrating a robot arm may in particular comprise determining parameters of a, preferably kinematic, model of the robot arm.

[0082] In one embodiment, such a model maps positions q of the joints of the robot arm and poses X of a robot-fixed reference, preferably an end flange, end effector, TCP or the like, to each other and depends on parameters p, whereby a pose can describe a one-, two- or three-dimensional position and / or a one-, two- or three-dimensional orientation in the usual way (forward kinematics: X = V(qp) or

[0083] Backward kinematics q = V(X, p')). Using corresponding pairs of values ​​{X, qi}, the parameters can be determined in a known manner, for example by minimizing the measurement errors E| - V(q h p)| or the like.

[0084] Calibrating a robot arm may in particular comprise determining transformations between robot arm-fixed coordinate systems and environment-fixed coordinate systems.

[0085] In one embodiment, a pose of the calibration element fixed to the robot arm can be described, on the one hand, by a transformation from a coordinate system fixed to the environment into a coordinate system fixed to the robot arm base, from there - in particular by means of a preferably kinematic model of the robot arm as a function of its joint positions - into a coordinate system fixed to the end flange and the pose of the calibration element fixed to the robot arm described therein, and, on the other hand, in the coordinate system fixed to the environment and the pose of the calibration element fixed to the robot arm in the respective end position described therein. Accordingly, the transformation between an environmentally fixed coordinate system and a coordinate system fixed to the robot arm base (and thus, in one embodiment, the pose of the robot arm orits base relative to the environment-fixed coordinate system) and / or the transformation between an end flange-fixed coordinate system and an end effector or calibration element-fixed coordinate system.

[0086] In general, the calibration of the robot arm in one embodiment is carried out on the basis of the recorded (first, further and / or second) joint positions and the known, in one embodiment specified and / or measured, end position(s).

[0087] In one embodiment, detection comprises a preferably sensory detection and / or storage of measured values.

[0088] In one embodiment, the calibration element fixed to the robot arm exerts a contact force, in a further development a predefined or desired contact force, on the first calibration element as a result of the force-controlled movement when moving to the first end position and / or a contact force, in a further development a predefined or desired contact force, on the second calibration element when moving to the second end position. In one embodiment, this can improve the approach to the end position and thus the calibration, in particular its precision, and / or time requirement. Additionally or alternatively, the corresponding feed direction can advantageously deviate from a direction of gravity, for example the robot arm can also move the calibration element fixed to the robot arm horizontally, overhead or the like, into the respective end position.

[0089] In one embodiment, force-controlled movement can also include additional position control, in particular a hybrid force-position control. In particular, force-controlled movement in a feed direction can include position-controlled movement in the feed direction and force-controlled movement, in particular deflection, transverse thereto.

[0090] A force-controlled movement in a feed direction within the meaning of the present invention can, in one embodiment, have or include not only a (movement) component in this feed direction but also a (movement) component transverse to the feed direction, which is preferably brought about in a form-fitting or mechanical manner by the first or second calibration element contacting the calibration element fixed to the robot arm. Accordingly, in one embodiment, when the calibration element fixed to the robot arm is displaced relative to the first or second calibration element contacting it in a feed direction, the calibration element fixed to the robot arm can, in addition to this displacement, execute a movement transverse to this feed direction relative to the calibration element contacting it, which movement is brought about in a form-fitting or mechanical manner by the contacting or first or second calibration element. Thus, in one embodiment, the force control brings about in one embodiment in one orthe (force-controlled) movement of the calibration element fixed to the robot arm relative to the first or second calibration element contacting it in the first or second feed direction, a relative movement transverse to this, coupled to the displacement in this feed direction, in particular mechanically and / or positively, so that the calibration element fixed to the robot arm is guided into the respective end position using or utilizing a single degree of freedom, in particular the degree of freedom in the feed direction. Further advantages and features emerge from the subclaims and the exemplary embodiments. In this connection, the drawing shows, partly schematically:

[0091] Fig. 1 : a system according to an embodiment of the present invention;

[0092] Fig. 2: a plan view of a first calibration element of Fig. 1; and

[0093] Fig. 3: a method according to an embodiment of the present invention.

[0094] Fig. 1 shows a system according to an embodiment of the present invention, which comprises a robot arm 1 with a robot arm base, with respect to which a robot arm base-fixed coordinate system B is defined, and an end flange 1.2, with respect to which an end flange-fixed coordinate system F is defined, as well as a controller 3 for controlling the robot arm 1.

[0095] A calibration element of a measuring device of the system with a partially spherical surface or contact surface 2 is arranged on the end flange 1.2 and is fixed to the robot arm.

[0096] The measuring device also has a first calibration element 10 with a guide surface 10.1 formed by a pyramid-shaped depression, the edges 11 of which (four in the exemplary embodiment) form guides for guiding the spherical upper or contact surface of the calibration element 2 fixed to the robot arm along one-dimensional, straight guideways. The tip region of the pyramid-shaped depression, in which the spherical upper or contact surface of the calibration element 2 fixed to the robot arm is finally stopped in a clearly defined first position upon insertion into the depression, is indicated by cross-hatching in Fig. 1 for illustration purposes and forms a cavity 12, wherein the guide surface 10.1 converges in a funnel-like manner towards this cavity 12.

[0097] The measuring device further comprises a second calibration element 20 with a guide surface 20.1 formed by a depression in the shape of a cone, the tip region of which, analogously to the spherical upper or contact surface of the calibration element 2 fixed to the robot arm, finally stops in a clearly defined second position when inserted into this depression.

[0098] To calibrate the robot arm 1, the controller 3 first controls it into a position in which the spherical upper or contact surface of the calibration element 2 fixed to the robot arm is roughly positioned at least partially within the recess of the first calibration element 10 (Fig. 3: step S10).

[0099] Then, the controller 3 moves the calibration element 2 fixed to the robot arm relative to the first calibration element 10 in a first feed direction, which is vertically downward in Fig. 1, with the aid of the robot arm 1 by moving the robot arm 1 accordingly in a force-controlled manner (Fig. 3: step S20).

[0100] During this movement, the calibration element 2, which is fixed to the robot arm, encounters the guide surface 10.1. Then, with further force-controlled retraction into the recess, it is retracted by the robot arm 1, first to one of the edges 11 and then along this edge into the cavity 12, while being guided mechanically or positively by the guide surface 10.1 or edge 11.

[0101] When the calibration element fixed to the robot arm is stopped in the cavity 12 and has a first end position X, the positions qn of its joints are detected in this first calibration position of the robot arm 1, one of which is designated as 1.1 in Fig. 1 by way of example (Fig. 3: step S30), wherein the calibration element fixed to the robot arm continues to exert a force-controlled contact force on the guide surface 10.1 in the cavity 12 during this detection.

[0102] Beforehand, the positions q of the joints are recorded at least once when the robot arm 1 travels along the edge 11 in a further calibration position that is passed through.

[0103] While the calibration element fixed to the robot arm continues to exert a force-controlled contact force on the guide surface 10.1 in the cavity 12, the robot arm 1 is moved from the first calibration position into at least one further calibration position, wherein the calibration element fixed to the robot arm continues to be arranged in the first end position or, due to the force-controlled contact force in interaction with the cavity 12, maintains the first end position (Fig. 3: step S40). The positions qi2 of the joints are also detected in this further calibration position (Fig. 3: step S50), wherein the calibration element fixed to the robot arm continues to exert a force-controlled contact force on the guide surface 10.1 in the cavity 12 during this detection.

[0104] In one embodiment, the orientation of the calibration element fixed to the robot arm relative to the first calibration element 10 can be changed during adjustment to the further calibration position. Thereafter, in one embodiment, while maintaining the first end position and the orientation of the calibration element fixed to the robot arm relative to the first calibration element, the robot arm 1 can be adjusted to at least one further calibration position, and the positions of the joints can also be recorded in this or these further calibration position(s).

[0105] Likewise, when adjusting the robot arm 1 from the first calibration position to a further calibration position, the calibration element fixed to the robot arm can maintain both the first end position and its orientation relative to the first calibration element and, if appropriate, the robot arm can then be adjusted to at least one further calibration position while maintaining the first end position of the calibration element fixed to the robot arm and changing its orientation relative to the first calibration element.

[0106] Subsequently, in an analogous manner, the spherical upper or contact surface of the calibration element 2 fixed to the robot arm is roughly positioned at least partially within the recess of the second calibration element 20 using the robot arm 1 (Fig. 3: step S60).

[0107] Then, the controller 3 moves the calibration element fixed to the robot arm relative to the second calibration element in a second feed direction, which is also vertically downward in Fig. 1, with the aid of the robot arm 1 by moving the robot arm 1 accordingly in a force-controlled manner (Fig. 3: step S70).

[0108] During this movement, the calibration element, which is fixed to the robot arm, encounters the guide surface 20.1. Then, with further force-controlled retraction into the recess, it is retracted by the robot arm 1 to the tip area of ​​the conical recess, where it is mechanically or positively guided by the guide surface 20.1.

[0109] When the calibration element fixed to the robot arm is stopped in the second cavity 22 formed by this tip area and has a second end position X2, the positions q 2iof its joints is detected (Fig. 3: step S80), wherein the calibration element 2 fixed to the robot arm continues to exert a force-controlled contact force on the guide surface 20.1 in the cavity 22 during this detection.

[0110] While the calibration element 2, which is fixed to the robot arm, continues to exert a force-controlled contact force on the guide surface 20.1 in the cavity 22, the robot arm 1 is moved from the second calibration position into at least one further calibration position, wherein the calibration element, which is fixed to the robot arm, remains arranged in the second end position or maintains the second end position due to the force-controlled contact force in cooperation with the cavity 22 (Fig. 3: step S90). In this further calibration position, the positions q 22of the joints is detected (Fig. 3: step S100), wherein the calibration element fixed to the robot arm continues to exert a force-controlled contact force on the guide surface 20.1 in the cavity 22 during this detection. As explained above with reference to the first calibration element, the calibration element fixed to the robot arm can have the same end position and different orientations and / or the same end position and orientation in two or more of the calibration positions.

[0111] The end positions are known in an environmentally fixed coordinate system W, for example, based on measurements. Then, in a step S110, a kinematic model of the robot arm 1 can be calibrated by determining, purely as an example, parameters p of the model V such that the sum of the deviation |X - V (qi2, p)| + |Xi - V(q 22 , p)| + |X2- V(q2i, p)| + |X2- V (q 22 , p)| becomes minimal.

[0112] Additionally or alternatively, in step S110, a transformation between the environment-fixed coordinate system W and the robot arm base-fixed coordinate system B and / or between the end flange-fixed coordinate system F and a robot tool-fixed coordinate system T can be carried out in a manner known per se, for example on the basis of the relationship F 7T • eT F (q) - W TB = w F , where W T B the (sought) transformation from the environment-fixed coordinate system W into the robot arm base-fixed coordinate system B (which determines the pose of the robot base relative to the environment or the environment-fixed coordinate system W), B T F the transformation from the robot arm base-fixed coordinate system B to the end flange-fixed coordinate system F, which is dependent on the joint positions q and determined using the kinematic model or a kinematic model, F7T the (sought) transformation from the end flange-fixed coordinate system F into the robot tool-fixed coordinate system T (which determines the pose of the robot tool relative to the end flange), and B 7T denotes the transformation from the environment-fixed coordinate system W into the robot tool-fixed coordinate system arranged in the respective end position, which can be determined based on a measurement of the cavities 12, 22 relative to W. In this calibration, the various recorded joint positions and the respective known end positions are again used.

[0113] In addition, due to the two positions q , qn along the edge 11 , whose orientation relative to W is known on the basis of a measurement of the guide surface 10.1, in addition to the position, an orientation of the robot tool-fixed coordinate system arranged in the first end position is also known and can be advantageously used in the calibration described above.

[0114] Although exemplary embodiments have been explained in the preceding description, it should be noted that a large number of modifications are possible.

[0115] Thus, purely by way of example, a first and a second calibration element were explained, of which one, purely by way of example, has a guide surface in the form of a pyramid-shaped depression (the edges of which form guides for guiding the calibration element fixed to the robot arm into the cavity 12 along a one-dimensional, straight guide path) and the other, again purely by way of example, has a guide surface in the form of a conical depression. Of course, both calibration elements can each have the pyramid-shaped or conical depression or a different type of depression. Additionally or alternatively, instead of a pyramid shape with four edges, a different pyramid shape, for example with only three edges, can be used. Additionally or alternatively, one or more further second calibration elements can be provided or used in an analogous manner, as was illustrated purely by way of example with reference to the second guide surface 20.1.Additionally or alternatively, one or more of the calibration elements may be oriented differently to the environment, for example, have horizontal or upward feed directions, which may in particular improve flexibility and / or space requirements.

[0116] As already mentioned, force-controlled movement can also include additional position control, in particular, a hybrid force-position control. Purely by way of example, in the exemplary embodiment described above, a feed movement in the respective feed direction can be performed in a position-controlled manner in the feed direction, and the robot arm 1, with the calibration element 2 fixed to the robot arm, can deflect in a force-controlled manner transversely thereto (i.e., horizontally in the exemplary embodiment) as a result of the guidance by the respective calibration element fixed to the environment.

[0117] Furthermore, it should be noted that the exemplary embodiments are merely examples and are not intended to limit the scope of protection, applications, or structure in any way. Rather, the preceding description provides the skilled person with a guide for implementing at least one exemplary embodiment. Various modifications, particularly with regard to the function and arrangement of the described components, may be made without departing from the scope of protection as defined by the claims and equivalent combinations of features.

[0118] List of reference symbols

[0119] 1 robot arm

[0120] 1.1 Joint

[0121] 1.2 End flange

[0122] 2 robot arm-mounted calibration element

[0123] 3 Robot arm control

[0124] 10 first calibration element

[0125] 10.1 Guide surface

[0126] 11 edge

[0127] 12 Cavity

[0128] 20 second calibration element

[0129] 20.1 Guide surface

[0130] 22 Cavity

[0131] B robot arm base fixed coordinate system

[0132] F end flange fixed coordinate system

[0133] T robot tool-fixed coordinate system

[0134] W environmentally fixed coordinate system

Claims

A method for calibrating a robot arm (1) having a plurality of joints (1.1), using a measuring device having a first calibration element (10) and a calibration element (2) fixed to the robot arm, which can be moved relative to the first calibration element by adjusting the joints of the robot arm, wherein the first and the calibration element fixed to the robot arm are designed such that upon displacement of the calibration element fixed to the robot arm relative to the first calibration element in a first feed direction, the calibration element fixed to the robot arm is guided from different first starting positions by the first calibration element into the same defined first end position; wherein the method comprises the steps: - positioning (S10) the calibration element fixed to the robot arm relative to the first calibration element using the robot arm in one of the first starting positions; - force-controlled movement (S20) of the calibration element fixed to the robot arm relative to the first calibration element in the first feed direction by means of the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the first calibration element into the first end position and the robot has a first calibration position at this end position; - detecting (S30) first positions of the joints of the robot arm in the first calibration position; and - Calibrating (S110) the robot arm based on these first joint positions. The method according to claim 1, characterized in that the measuring device has at least one second calibration element (20), wherein the second and the robot-arm-fixed calibration elements are designed such that, upon displacement of the robot-arm-fixed calibration element relative to the second calibration element in a second feed direction, the robot-arm-fixed calibration element is guided from different second starting positions by the second calibration element into the same defined second end position; wherein the method comprises the steps: - positioning (S60) the calibration element fixed to the robot arm relative to the second calibration element using the robot arm in one of the second starting positions; - force-controlled movement (S70) of the calibration element fixed to the robot arm relative to the second calibration element in the second feed direction by means of the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the second calibration element into the second end position and the robot has a second calibration position at this end position; and - Detecting (S80) second positions of the joints of the robot arm in the second calibration position; wherein the robot arm is calibrated (S110) based on the first and these second joint positions. Method according to one of the preceding claims, characterized by the steps: - Adjusting (S40) the robot arm from the first calibration position into at least one further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position; and - detecting (S50) further positions of the joints of the robot arm in this further calibration position; wherein the robot arm is calibrated (S110) based on the first and these further joint positions. Method according to claim 3, characterized in that - when adjusting the robot arm from the first calibration position to a further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position, when adjusting the robot arm between at least two calibration positions of the robot arm, the calibration element fixed to the robot arm is arranged in the first end position and an orientation of the calibration element fixed to the robot arm relative to the first calibration element is maintained, during the detection, positions of the joints of the robot arm are detected in these at least two calibration positions, and the robot arm is calibrated on the basis of these detected positions of the joints; and / or - when adjusting the robot arm from the first calibration position into a further calibration position in which the calibration element fixed to the robot arm is arranged in the first end position, in at least two calibration positions of the robot arm the calibration element fixed to the robot arm is arranged in the first end position and the calibration element fixed to the robot arm has different orientations relative to the first calibration element in these at least two calibration positions, during the detection positions of the joints of the robot arm are detected in these at least two calibration positions, and the robot arm is calibrated on the basis of these detected positions of the joints.Method according to one of the preceding claims, characterized in that the robot arm is force-controlled in the first calibration position, in particular when adjusted from the first calibration position to the further calibration position, such that the calibration element fixed to the robot arm exerts a contact force on the first calibration element in the first end position and is supported by the first calibration element in the first end position. Method according to one of the preceding claims, characterized in that one of the first and the robot arm-fixed calibration elements has a guide surface (10.1) with a cavity (12), wherein the other of the first and the robot arm-fixed calibration elements can be supported by the cavity in a defined support position that determines the first end position, wherein the guide surface converges towards the cavity.Method according to the preceding claim, characterized in that the guide surface has at least one guide (11) for guiding the other of the first and the robot-arm-fixed calibration elements into the cavity along a one-dimensional guide path. Method according to the preceding claim, characterized by the step: - force-controlled movement (S20) of the calibration element fixed to the robot arm relative to the first calibration element by means of the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided along the Guideway is guided and positions of the joints of the robot arm are recorded in at least two calibration positions (S20, S30); wherein the robot arm is calibrated on the basis of these joint positions (S110). System for calibrating a robot arm (1) having a plurality of joints (1.1) which is set up to carry out a method according to one of the preceding claims and / or comprises: a measuring device which has a first calibration element (10) and a calibration element (2) which can be arranged on the robot arm, wherein the first calibration element and the calibration element which can be arranged on the robot arm are designed in such a way that, when the calibration element which can be arranged on the robot arm is arranged on the robot arm, this calibration element which is fixed to the robot arm can be moved relative to the first calibration element by adjusting the joints of the robot arm, and when the calibration element which is fixed to the robot arm is displaced relative to the first calibration element in a first feed direction, the calibration element which is fixed to the robot arm is guided from different first start positions by the first calibration element into the same defined first end position; and / or a controller (3) for. Controlling the robot arm to position the calibration element fixed to the robot arm relative to the first calibration element using the robot arm in one of the first starting positions; Controlling the robot arm for force-controlled movement of the calibration element fixed to the robot arm relative to the first calibration element in the first feed direction using the robot arm, wherein during this movement the calibration element fixed to the robot arm is guided by the first calibration element into the first end position and the robot has a first calibration position at this end position; and Detecting first positions of the joints of the robot arm in the first calibration position; and / or a calibration means for calibrating the robot arm based on these first joint positions. Computer program or computer program product, wherein the computer program or computer program product, in particular stored on a computer-readable and / or non-volatile storage medium, Containing instructions which, when executed by one or more computers or a system according to claim 9, cause the computer(s) or system to perform a method according to any one of claims 1 to 8.

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