Recalibrating and controlling a drive of a robot joint

Abstract

The invention relates to a method for recalibrating a pre-calibrated drive (2) of a robot joint, the drive having a multiturn encoder (2.1) which supplies an absolute value for the drive position of the drive, the absolute value being based on the number of passes through the measurement range. The method has the following steps: determining (S30) the current drive position for the actual position of the robot joint, the actual position of the robot joint being reached in order to approximate a reference base position of the robot joint, with the aid of the multiturn encoder of the pre-calibrated drive; providing (S40) a reference drive position for the reference base position of the robot joint on the basis of the pre-calibrated drive; and recalibrating (S50) the pre-calibrated drive in such a way that a deviation between the provided reference drive position and the sum of the determined current drive position and the product of the integral number of passes through the measurement range and a change in the drive position per measurement range pass is minimized. The invention also relates to a robot controller or assembly and to a computer program (product).

Description

[0001] Description

[0002] Recalibrating and controlling a robot joint drive

[0003] The present invention relates to a method for recalibrating a (pre-calibrated) drive of a robot joint, a method for controlling the recalibrated drive to adjust the robot joint, as well as a robot control, an arrangement and a computer program or computer program product for carrying out a method described herein.

[0004] According to internal practice, drives for robot joints are known that incorporate a multiturn rotary encoder which provides an absolute value for a drive position that depends on the number of measurement range cycles. For example, a resolver with one pole pair provides an absolute value for a resolver position r = nR - 360° + x, where x represents a position within the measurement range [0, 360°] and nR is the number of cycles of this measurement range. A resolver with two pole pairs accordingly provides an absolute value for a resolver position r = nR - 180° + x, where x represents a position within the measurement range [0, 180°] and nR is the number of cycles of this measurement range.

[0005] According to internal company practice, such drives are calibrated by determining the drive position r, calculated using the multiturn rotary encoder, for a defined position of each robot joint. meThe value of the drive to be calibrated is set to a value specified for the defined position of the robot joint; in one version, a corresponding offset o is added to the absolute value supplied by the rotary encoder (o = G'). 1 -jdef - r me s with the reciprocal G' 1 a translation G from an adjustment of the drive to an adjustment of the joint). This can in particular be a so-called mastem, in which the defined position of each of the robot joint is detected by means of an EMD probe ("Electric Mastering Device") when a mechanical notch is crossed and reported to the robot controller, which then calibrates the drive based on the drive position determined by means of the multiturn rotary encoder, in particular determining the offset.

[0006] Since the absolute value supplied by the multiturn encoder also depends on the number of measurement range cycles, this number must be stored. If this information is lost or no longer reliable, the drive currently has to be remastered, which requires considerable time and equipment, in particular the temporary installation of the EMD probe.

[0007] Furthermore, the initial mastering process already requires a corresponding investment of time and equipment, in particular the temporary, precise placement of the EMD button.

[0008] The object of the present invention is to improve the recalibration and / or control of a drive of a robot joint, preferably to reduce at least one of the aforementioned disadvantages.

[0009] This problem is solved by a method with the features of claim 1 or 7. Claims 8-10 protect a robot control system or arrangement or a computer program or computer program product for carrying out a method described herein. The dependent claims relate to advantageous embodiments.

[0010] The present invention is based in particular on the following findings, ideas, and considerations: If a correct or calibrated first drive position rm of the robot joint drive is known for a first joint position ji of the robot joint, and the robot joint is located near this first joint position (j = j2« ji), then a drive position m2 determined for this joint position j2 of the robot joint near the first joint position using the drive or rotary encoder must be located near the first drive position (m2« r). Since, or if, the rotary encoder itself still measures correctly, in particular if no mechanical changes are present or only its zero point or the number of measurement range cycles is lost or no longer reliable, the correct drive position m2 can be determined. caiThe drive position m2, determined using the (no longer correctly calibrated) drive or rotary encoder, differs only by an integer multiple of the measurement range cycles (m2,cai = m2 + i-360° for a directly coupled resolver with one pole pair). Thus, a correct or correct measurement range cycle number can be determined for which the deviation to the first drive position becomes minimal, and with this measurement range cycle number the drive can be correctly recalibrated.

[0011] Accordingly, according to one embodiment of the present invention, a method for recalibrating a (previously) pre-calibrated drive of a robot joint, which has a multi-turn encoder or multi-turn resolver that provides an absolute value for a drive position of the drive, which depends on a number of measurement range cycles, in particular of the drive and / or multi-turn encoder or multi-turn resolver, comprises the step of:

[0012] - Determining a current drive position Mact of the drive for or in an actual joint position Jact of the robot joint using the multiturn rotary encoder of the pre-calibrated drive, wherein this actual joint position Jact approximates a reference joint basic position jRet.o of the robot joint or is approached in one embodiment of the procedure.

[0013] In one embodiment, a translation ratio G, preferably of a gearbox of the robot joint, transforms a drive position M of the drive into a joint position J of the robot joint, or the reciprocal transforms the joint position into the drive position:

[0014] J = GM or M = G- 1 J (1 )

[0015] In the case of a rotary joint, the joint position can depend on the angular position of a (distal) robot (structure) element relative to another (proximal) robot (structure) element, to which this (distal) robot (structure) element is rotatably mounted in the robot (rotary) joint. This position can be specified or defined. In the case of a linear joint, the joint position can depend on a translational displacement of a (distal) robot (structure) element relative to another (proximal) robot (structure) element, to which this (distal) robot (structure) element is slidably mounted in the linear or linear joint. This displacement can be specified or defined.

[0016] In one embodiment, the robot axis drive comprises a drive motor, preferably an electric motor. A drive position can depend, in particular, on the angular position of an output shaft of the (rotary) drive, preferably of the drive (rotary) motor, relative to a housing of the drive (motor); this position can be specified or defined.

[0017] An actual joint position approximates a reference joint home position in one embodiment if the deviation between the actual joint position and the reference joint home position (in magnitude) is less than or equal to the change in joint position that occurs during a full measurement range cycle of the multiturn encoder, or, in a further development, during half a measurement range cycle of the multiturn encoder. For example, if the resolver has one pole pair and is coupled directly or via a 1:1 ratio to the drive (motor), a full measurement range cycle corresponds to 360°, and half a measurement range cycle to 180°. With a ratio of, for example, 360, the deviation between the reference joint home position and an actual joint position approximating it (in magnitude) is then a maximum of 1° or 0.5°, respectively. Multipole resolvers and / or couplings with other ratios can be taken into account by appropriate factors.

[0018] According to one embodiment of the present invention, the method comprises the following step:

[0019] - Providing a reference drive position MRef for the reference joint basic position jRef.o based on the pre-calibrated drive.

[0020] The reference drive position MRef can, in one embodiment, particularly for sliding joints or rotary joints that are not rotatable by more than 360°, be related to the reference joint basic position JRef.o according to the above equation (1) (MRef = G' 1 -jRef,o), in particular, must be determined or provided accordingly. For rotary joints that can rotate more than 360°, providing the reference drive position may involve determining one of several possible reference drive positions, each differing from the others by 360°, which will be explained in more detail below.

[0021] According to one embodiment of the present invention, the method comprises the following step:

[0022] - Recalibrating the pre-calibrated drive in such a way, in particular with the stipulation that a deviation (|Mact + HR-A - MRef|) between the provided reference drive position MRef and a sum (Mact + HR-A) of the determined current drive position Mact and a product (HR-A) of an integer number nR of measurement range cycles and / or multiplied by a change A of the drive position of the drive per measurement range cycle is minimized (nR such that |MRet - (Mact + nR-A)| = Min or |M ac t + OR-A - MRet| Min).

[0023] In one embodiment, a corresponding integer correction number nR.cor of measurement range passes is used, preferably by rounding, in particular according to nR,cor = round[(MRet - M act) / A] (2) determined and the drive is recalibrated with this integer correction number, in particular an assignment between drive positions Mrekaiibrated determined using the multiturn rotary encoder and associated joint positions Jrekaiibrated, preferably according to

[0024] Mrekailibiert = Mact + HR.cor-A; Jrekaiibrated = G- Recalibrated (3) In particular, a (new) offset can thus be determined which is added to the drive positions determined using the multiturn rotary encoder of the recalibrated drive, wherein the recalibrated drive implements the correspondingly recalibrated mapping between drive positions and joint positions.

[0025] The robot joint can in particular be a rotary joint, for which the present invention is particularly advantageous, especially due to the kinematic boundary conditions.

[0026] If the rotary joint can rotate more than 360°, several joint positions, each differing by 360°, correspond to the same relative position of an output shaft of the drive to a housing of the drive. Therefore, in one embodiment, the reference drive position is provided based on the pre-calibrated drive for a reference joint position of the robot joint, which represents a deviation (| Ja, vor - (jRef.o + nj-360°)|) between a current joint position Ja, vor of the robot joint, which is assigned to the determined current drive position Mact for the pre-calibrated drive, in particular according to Eq. (1) or Yes, before = G-Mact, and a sum (JRef.o + nj-360°) of the reference joint home position JRef.o and a product (nj-360°) of an integer number of pivot joint rotations and or multiplied by a change in joint position per rotation or 360° minimized (nj) such that (| Yes, before - (JRef.o + nj-360°)| = Min or | Yes, before - (JRef.o + nj-360°)| Min).

[0027] In one embodiment, the corresponding integer number nj of pivot joint rotations is obtained, preferably by rounding, in particular according to nj = round[(Ja,vor - J R ef,o) / 36O°] (4) determined and the reference drive position is provided with this integer number of pivot joint revolutions, preferably according to Eq. (1) or

[0028] M R ef = G- 1 -(J R ef,o + nj-36O°) (5)

[0029] The robot joint can also be a sliding joint. The present invention is particularly advantageous for this purpose, especially due to the mechanical constraints.

[0030] In one embodiment, the actual joint position is determined by means of a stepwise and / or manually controlled adjustment of the robot joint and / or by means of an optical and / or tactile evaluation of the approximation of the reference joint home position and / or by means of approaching a stop, which in one embodiment is mechanical.

[0031] This can reduce the time and / or equipment required for recalibration, preferably eliminating the need for an EMD button for (re)mastering.

[0032] An optical evaluation of the approximation can, in particular, include checking the spatial position of markings on robot (structure) elements connected to each other in the robot joint, or adjusting the robot joint until these markings have a predetermined position relative to each other within an optical or observational tolerance. Accordingly, in one embodiment, the reference joint position is defined or predetermined by optically recognizable markings on robot (structure) elements connected to each other in the robot joint.

[0033] A tactile evaluation of the approximation can, in particular, include tactilely checking whether a mechanical feature, especially a notch, protrusion, or the like, has been reached or passed over on a robot (structure) element connected to the robot joint, especially with a hand or a rod or the like, or adjusting the robot joint until, or with the stipulation that, this feature has a predetermined position relative to the other robot (structure) element connected to the robot joint within a tactile tolerance. Accordingly, the reference joint home position in one embodiment is defined or specified by tactilely recognizable features on robot (structure) elements connected to each other in the robot joint, for example, a notch, protrusion, or the like, and a receptacle for guiding a sensor for tactile detection of the feature. In this context, "tactile" refers in particular to haptic or...understood using the sense of touch (of an operator).

[0034] In one embodiment, and in a further development, the reference joint position is selected from one of at least two predefined reference joint positions, for example, by moving to one of two end stops. This advantageously allows for the use or approximation of a different reference joint position if one of the predefined reference joint positions cannot be reached.

[0035] In one implementation, the reference joint position is a joint reference position used during the drive's pre-calibration, for example, the joint reference position that is approached using an EMD probe during pre-calibration or mastering. This saves time and can increase precision.

[0036] Similarly, a different joint position can also be used as the reference joint position, which has been determined using the still correct or pre-calibrated drive, as described in a further development. For example, after pre-calibration, a joint position can be approached with the still correctly (calibrated) drive in which the previously described markings have the specified relative positions, and then used for recalibration as the reference joint position (jRef.o is then obtained by multiplying the drive position determined in the approached joint position, in which the markings have the specified relative positions, by the gear ratio G). As also mentioned elsewhere, in one embodiment the pre-calibration can be a part or part of the process.This step of a method according to the invention may include mastering, in particular with an EMD probe, or calibration analogous to the recalibration described herein. In other words, during pre-calibration, the reference joint home position can be approached by means of a stepwise and / or manually controlled adjustment of the robot joint and / or by means of an optical and / or tactile evaluation of reaching the reference joint home position and / or by means of approaching a stop, and then the drive, in particular an offset, can be pre-calibrated using the drive position determined thereby (J = G-(M+O)).

[0037] According to one embodiment of the present invention, a method for controlling a robot joint or the drive of a robot joint or the robot joint comprises the following steps:

[0038] - Recalibrating the pre-calibrated drive according to a procedure described here; and

[0039] - Controlling the (such) recalibrated drive to adjust the robot joint.

[0040] According to one embodiment of the present invention, a robot control system or arrangement, in particular in terms of hardware and / or software, is set up and / or has the following features for carrying out a method described herein:

[0041] - Means of determining a current drive position of the drive for an actual joint position of the robot joint approached to approximate a reference joint basic position of the robot joint using the multiturn rotary encoder of the pre-calibrated drive;

[0042] - Means of providing a reference drive position for the reference joint home position based on the pre-calibrated drive; and

[0043] - Means for recalibrating the pre-calibrated drive such that a deviation between the provided reference drive position and a sum of the determined current drive positions and a product of an integer number of measurement range cycles and a change in the drive position per measurement range cycle is minimized. In one embodiment, the arrangement comprises a robot with the robot joint with the drive and the robot controller or its means. In one embodiment, the arrangement or robot controller or its means comprises:

[0044] - Means of providing the reference drive position based on the pre-calibrated drive for a reference joint position of the robot joint that minimizes a deviation between a current joint position of the robot joint, which is assigned to the determined current drive position for the pre-calibrated drive, and a sum of the reference joint home position and a product of an integer number of rotary joint revolutions and a change in joint position per revolution; and / or

[0045] - Means of approaching the actual joint position by means of a stepwise and / or manually controlled adjustment of the robot joint and / or by means of an optical and / or tactile evaluation of the approximation of the reference joint home position and / or by means of approaching a stop; and / or

[0046] - Means for selecting the reference joint position from one of at least two predefined reference joint positions and / or for determining the reference joint position using the pre-calibrated drive or using a joint reference position used during the pre-calibration of the drive as the reference joint position; and / or

[0047] - Means for controlling the recalibrated drive to adjust the robot joint.

[0048] A means according to the present invention can be configured as hardware and / or software, in particular comprising at least one processing unit, preferably a microprocessor unit (CPU), graphics processing unit (GPU), or the like, preferably connected to a storage and / or bus system via data or signals, and / or comprising one or more programs or program modules. The processing unit can be configured to execute instructions implemented as a program stored in a storage system, to acquire input signals from a data bus, and / or to output signals to a data bus. A storage system can comprise one or more, in particular different, storage media, in particular optical, magnetic, solid-state, and / or other non-volatile media. The program can be configured to embody the methods described herein.is capable of executing such procedures, enabling the processing unit to perform the steps of such procedures and, in particular, to recalibrate or control the drive. A computer program product may, in one embodiment, include a storage medium, in particular a computer-readable and / or non-volatile medium, for storing a program or instructions, or with a program or instructions stored thereon. In one embodiment, the execution of this program or these instructions by an arrangement or robot control, in particular a computer or an arrangement of several computers, causes the arrangement or control, in particular the computer(s), to execute a procedure described herein or one or more of its steps, or the program or instructions are configured for this purpose.

[0049] In one embodiment, one or more, in particular all, steps of the procedure are fully or partially computer-implemented, or one or more, in particular all, steps of the procedure are fully or partially automated, in particular by the system or its means.

[0050] Further advantages and features will become apparent from the dependent claims and the exemplary embodiments. These are shown, in part schematically:

[0051] Fig. 1: Part of an arrangement with a robot and a robot controller according to an embodiment of the present invention; and

[0052] Fig. 2: a method according to one embodiment of the present invention.

[0053] Fig. 1 shows part of an arrangement with a robot and a robot controller 4 according to an embodiment of the present invention.

[0054] Two robot (structure) sections 10 and 11 are partially shown, connected by a rotary joint. A drive in the form of an electric motor 2 is arranged on robot section 10 and is coupled to the other robot section 11 via a gearbox 3 for adjusting the rotary joint. A multiturn rotary encoder 2.1 provides an absolute value for a drive position of the drive.

[0055] Electric motor 2 to the robot controller 4.

[0056] In step S10, the drive is pre-calibrated, and in a preferred embodiment, mastered. The pre-calibration can be part of a method according to the invention; likewise, the method according to the invention can also be carried out for or with a drive that has already been pre-calibrated and, in a further development, mastered.

[0057] For mastering, in step S10 an EMD sensor 5 is temporarily attached to the robot element 10 and signals to the robot controller 4 when a notch K on the robot element 11 is passed over. Based on this defined position of the robot joint and the absolute value n ies supplied by the rotary encoder or resolver 2.1, the controller determines an offset o (o = G'). 1 -jdef - r me s with the translation G of the gearbox 3) and this is used to control the drive thus pre-calibrated. After removing the EMD probe 5, the robot is operated, for example, test runs or automatic operation is carried out, or the like.

[0058] It is expressly pointed out that pre-calibration of the drive may include mastering the drive using EMD probes 5, which can improve the precision during subsequent operation of the robot even after recalibration. However, the invention is not limited to this, but pre-calibration of the drive can also be carried out in another way, in particular in a particularly preferred embodiment analogous to the recalibration described below, thereby eliminating the time and equipment costs of mastering, which can be particularly advantageous for inexpensive small robots.

[0059] Particularly when the robot controller 4 is temporarily switched off, it can happen that a stored number of measurement range cycles nR of the resolver 2.1, starting from a zero point, is lost or no longer reliable. Since the absolute value for the drive position of the drive 2 supplied by the resolver 2.1 depends on this number of measurement range cycles (r = nR-360° + x, x G [0, 360°]), the pre-calibration may no longer be correct.

[0060] Therefore, the drive is recalibrated.

[0061] In step S20, to approximate a reference joint position jRef.o of the robot joint, an actual joint position is approached using the multiturn rotary encoder 2.1 of the pre-calibrated drive. The reference joint position can, in particular, be the joint reference position shown in Fig. 1, which was used during the pre-calibration of the drive in step S10. It can also be determined in step S10 using the drive that is still correctly or pre-calibrated. The reference joint position can, in particular, be defined by the notch K and the receptacle for the EMD probe 5: for this purpose, a user guides a finger or a rod through the receptacle and tactilely detects that the notch has been reached. Similarly, for example, aligned markings on the robot segments 10, 11 can define the reference joint position.Both variants illustrate how advantageous it is to reduce time and equipment costs compared to a mast with an EMD button.

[0062] In the reference joint basic position, a current drive position Mact is determined using the multiturn rotary encoder 2.1 of the pre-calibrated drive (Fig. 2: step S30).

[0063] Since a rotation of the robot element 11 by 360° or a multiple thereof results in the same relative position of the output shaft of the drive 2, the reference drive position MRef is first determined. For this purpose, in step S40, an integer number of rotary joint rotations is determined according to Eq. (4), and from this, the reference drive position MRef is determined or provided according to Eq. (5).

[0064] For example, if the reference joint position JRef.o = 0° and the pre-calibration became unreliable after 10 rotations of the joint, the rotary encoder 1 delivers a value of 3600.003° for the current drive position Mact (since 0° was not reached exactly due to the optical or tactile (evaluation of the) approximation, Eq. (4) accordingly nj = 10 and Eq. (5) then M Ref = G- 1 -(3600°).

[0065] For sliding joints or rotary joints that are not capable of multiple rotations, this can be omitted and the drive position corresponding to the reference joint basic position (taking the gear ratio into account) can be provided as the reference drive position in step S40 (M Re f = G' 1 -J Re f = G' 1 -J Re f,o).

[0066] Now, in step S50, the pre-calibrated drive is recalibrated with the stipulation that there is no deviation between the provided reference drive position M. Re f and a sum of the determined current drive position Mact and a product of an integer number n R The number of measurement range cycles and the change A of the drive position per measurement range cycle are minimized. For this purpose, an integer correction number n is often used according to Eq. (2). R ,cor of

[0067] The measuring range cycles were determined and thus, according to Eq. (3), the drive, in particular an assignment between drive positions Mkai determined using the multiturn rotary encoder 2.1 and associated joint positions Jkai, was recalibrated.

[0068] In step S60, the robot controller 4 controls the drive 2, which has been recalibrated in this way, to adjust the robot joint, in particular to carry out automatic operation of the robot.

[0069] In the present disclosure, "has an X" does not generally imply an exhaustive list, but is a shorthand for "has at least one X" and also includes "has two or more X" as well as "has Y in addition to X". Although exemplary embodiments were explained in the preceding description, it should be noted that a multitude of variations are possible. 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, whereby various modifications, particularly with regard to the function and arrangement of the described components, can be made without leaving the scope of protection as defined by the claims and these equivalent combinations of features.

[0070] List of reference signs

[0071] 2.1 Multiturn rotary encoder

[0072] 2 Electric motor (drive) 3 Gearbox (transmission ratio G)

[0073] 4 Robot control

[0074] 5 EMD buttons

[0075] 10, 11 robot structural elements

[0076] K notch

Claims

Patent claims 1. A method for recalibrating a pre-calibrated drive (2) of a robot joint having a multi-turn rotary encoder (2.1) which provides an absolute value for a drive position of the drive which depends on a number of measurement range passes, wherein the method comprises the steps: - Determining (S30) a current drive position of the drive for an actual joint position of the robot joint approached to approximate a reference joint basic position of the robot joint using the multiturn rotary encoder of the pre-calibrated drive; - Providing (S40) a reference drive position for the reference joint home position based on the pre-calibrated drive; and - Recalibrating (S50) the pre-calibrated drive such that a deviation between the provided reference drive position and a sum of the determined current drive position and a product of an integer number of measurement range passes and a change in the drive position of the drive per measurement range pass is minimized.

2. Method according to claim 1, characterized in that the robot joint is a rotary joint.

3. Method according to claim 2, characterized in that the rotary joint is rotatable by more than 360° and the reference drive position is provided on the basis of the pre-calibrated drive for a reference joint position of the robot joint which minimizes a deviation between a current joint position of the robot joint, which is assigned to the pre-calibrated drive of the determined current drive position, and a sum of the reference joint basic position and a product of an integer number of rotary joint revolutions and a change in joint position per revolution.

4. Method according to claim 1, characterized in that the robot joint is a shear joint.

5. Method according to one of the preceding claims, characterized in that the method comprises pre-calibrating the drive and / or the actual joint position is approached by means of a stepwise and / or manually controlled adjustment of the robot joint and / or by means of an optical and / or tactile evaluation of the approximation of the reference joint home position and / or by means of approaching a stop.

6. Method according to one of the preceding claims, characterized in that the reference joint position is selected from one of at least two predetermined reference joint positions and / or is determined using the pre-calibrated drive or is a joint reference position used in the pre-calibration of the drive.

7. Method for controlling a drive of a robot joint, wherein the method comprises the steps: - Recalibrating the pre-calibrated drive according to a method according to one of the preceding claims; and - Control (S60) the recalibrated drive to adjust the robot joint.

8. Robot control (4) which is configured and / or comprises for carrying out a method according to one of the preceding claims: - Means of determining a current drive position of the drive for an actual joint position of the robot joint approached to approximate a reference joint basic position of the robot joint using the multiturn rotary encoder of the pre-calibrated drive; - Means of providing a reference drive position for the reference joint home position based on the pre-calibrated drive; and - Means for recalibrating the pre-calibrated drive such that a deviation between the provided reference drive position and a sum of the determined current drive position and a product of an integer number of measurement range passes and a change in the drive position of the drive per measurement range pass is minimized.

9. Arrangement comprising a robot with at least one robot joint, a drive (2) and a robot controller (4), in particular according to claim 8, which is set up to carry out a procedure according to one of the preceding claims.

10. Computer program or computer program product, wherein the computer program or computer program product contains instructions, in particular stored on a computer-readable and / or non-volatile storage medium, which, when executed by a robot controller according to claim 8 or 9, cause the robot controller or arrangement to perform a method according to any one of claims 1 to 7.

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