JP5803173B2 - Robot control apparatus and calibration method - Google Patents

Description

  The present invention relates to a technique for calibrating a robot.

  Regarding the technology for calibrating the robot (calibration), for example, in the technology described in Patent Document 1, by moving the end effector with respect to the target point from the first position and the second position symmetrical with respect to the target point, Positive direction data and negative direction data are acquired, and calibration data is created based on these data. In this technique, the effect of hysteresis existing in each part of the robot is suppressed by correcting the position of the end effector based on the calibration data thus created.

  However, once the robot is installed in the equipment, it may be necessary to perform calibration in a limited space due to factors such as downsizing of the equipment. In such a case, for example, if the first position or the second position described above is a position corresponding to the operation limit position (mechanical end) of the joint shaft, the end effector cannot be moved to that position. There may be a situation in which the calibration cannot be substantially performed. Such a problem is not limited to the end effector, but is a problem common when calibrating each joint axis of the robot.

JP 2009-142904 A

  In view of the above-mentioned problems, the problem to be solved by the present invention is to provide a technology that can accurately calibrate a robot joint axis at an arbitrary position even when the joint axis of the robot cannot be calibrated at its operation limit position. It is to be.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 An absolute encoder that outputs position information including a joint axis, a motor that drives the joint axis, a position within one rotation representing a physical position of the rotation axis of the motor, and a multi-rotation position; A first position information acquisition unit that acquires position information from the absolute encoder when the joint axis is moved to an arbitrary calibration position on the joint axis; And determining whether the position within one rotation included in the position information acquired by the first position information acquisition unit is included in a predetermined allowable range that does not include an origin serving as a reference for counting the multi-rotation positions. The position within one rotation when the position within one rotation included in the position information acquired by the position range determination unit and the first position information acquisition unit is not included in the allowable range. The movement request unit that requests movement of the calibration position and the position within one rotation included in the position information acquired by the first position information acquisition unit are included in the allowable range until they are included in the allowable range. In this case, a robot control apparatus comprising: a correction value determining unit that determines a correction value for correcting the physical position of the joint axis and the control position based on the position information and the control position of the joint axis.

  According to the robot control device having such a configuration, when the correction value for correcting the physical position of the joint axis and the control position is obtained, the position within one rotation output from the absolute encoder is the multi-rotation position. If the position within one rotation is not included in the allowable range, the calibration is performed until the position is included in the allowable range. Request movement of the location. Therefore, the position of the joint axis for determining the correction value (hereinafter also referred to as “calibration position”) is suppressed from being set to a position close to the origin of the absolute encoder. As a result, since the multi-rotation position output from the absolute encoder is prevented from becoming unstable during the second and subsequent calibration of the joint axis, high accuracy is obtained at an arbitrary position. Calibration can be performed. Also, in the alignment to the calibration position once set, it is assumed that the hysteresis of each part of the robot, the force at the time of alignment to the calibration position, and the deviation due to the amount of alignment at the time of alignment occurred on the joint axis However, in many cases, the influence falls within the deviation within the range of the position within one rotation of the rotating shaft of the motor. Therefore, if the calibration position is set within the allowable range as in the above configuration, even if the positional deviation due to the various factors described above occurs in the alignment to the calibration position at the second and subsequent calibrations, the deviation is caused. Stays within the range of the position within one rotation and is prevented from shifting to the multi-rotation position. Therefore, it is possible to realize highly accurate calibration.

[Application Example 2] The robot control apparatus according to Application Example 1, wherein the allowable range is 360 ° (2π rad) of the rotation axis of the motor from the entire range of the position within one rotation starting from the origin. A robot controller that is a range excluding a position delayed by a value divided by the number of gears and a position advanced to the value.

  The alignment of the joint shaft to the calibration position is restricted by the resolution of the gear provided on the rotation shaft of the motor. Therefore, if the range excluding the range where the position is moved back and forth by one gear from the origin is set as the allowable range as in the above configuration, the range in which the calibration position can be set can be increased. The degree of freedom of setting can be increased.

[Application Example 3] The robot control apparatus according to Application Example 1 or Application Example 2, and further, at least the position within one rotation and the position of the joint axis in the position information when the correction value is determined. A controller-side storage unit that stores a control position; and a position information is acquired from the absolute encoder when the joint axis is moved to the calibration position again after the correction value is determined. 2 position information acquisition unit and the position within one rotation in the position information acquired by the second position information acquisition unit is changed to the position within one rotation stored in the control device side storage unit, and after the change And a correction value update unit that updates the correction value based on the position information of the joint axis and the control position of the joint axis stored in the control device side storage unit.

  With the robot control device having such a configuration, the second and subsequent calibrations (update of correction values) can be performed using the position within one rotation stored in advance in the control device-side storage unit. Therefore, in the second and subsequent calibrations, even if there are effects such as hysteresis of each part of the robot, force adjustment at the time of alignment to the calibration position, and deviation due to the amount of distance at the time of alignment, the first calibration By using the position within one rotation memorized at the time, recalibration can be performed with high accuracy. The pre-stored position within one rotation can be used as it is, as described above, even if a misalignment occurs in the alignment with the calibration position due to various factors, This is because it falls within the range.

Application Example 4 In the robot control device according to Application Example 3, the absolute encoder includes a volatile encoder side storage unit that holds a multi-rotation position in the position information, and the encoder side storage unit. A battery for battery backup, and the second position information acquisition unit is configured to store the multiple values from the encoder side storage unit after the correction value is determined by the correction value determination unit and after the battery is replaced. A robot control apparatus that acquires the position information after a rotational position is lost.

  Also in this configuration, as described above, since the calibration position is suppressed from being set near the origin of the absolute encoder, a multi-rotation position is accurately output from the absolute encoder. Therefore, even when the multi-rotation position is lost due to the voltage drop of the battery of the absolute encoder and calibration is necessary again, the calibration can be performed accurately. As a result, it is not necessary to perform teaching or the like again with battery replacement, so that the robot can be returned quickly.

  In addition to the configuration as the robot control device described above, the present invention can also be configured as a robot calibration method and a computer program for performing robot calibration. The computer program may be recorded on a computer-readable recording medium. In addition, the components of each application example described above can be combined or omitted as appropriate.

It is explanatory drawing which shows schematic structure of the robot system containing a robot control apparatus. It is a block diagram which shows the internal structure of a robot main body and a robot control apparatus. It is a flowchart of an initial calibration process. It is explanatory drawing which shows the tolerance | permissible_range of the position within 1 rotation. It is a flowchart of a recalibration process.

A. System configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of a robot system 10 including a robot control apparatus 200 as an embodiment of the present invention. The robot system 10 is connected to the robot main body 100 configured as an articulated industrial robot, a robot control device 200 that controls the operation of the robot main body 100, and the robot control device 200, and teaches the operation of the robot main body 100. And a robot teaching device 300 for performing the above. The robot body 100 and the robot control device 200, and the robot control device 200 and the robot teaching device 300 are connected to each other via a predetermined connection cable.

  The robot body 100 includes, for example, a base portion 101 fixed to equipment in a factory, a shoulder portion 102 supported by the base portion 101 by a joint shaft that can turn in a horizontal direction, and a joint shaft that can turn in a vertical direction. A lower arm 103 whose lower end is supported by the shoulder portion 102, an upper arm 104 whose substantially central portion is supported at the tip of the lower arm 103 by a joint shaft that can pivot in the vertical direction, and a joint shaft that can pivot in the vertical direction A wrist 105 supported at the tip of the upper arm 104. A flange portion 106 having a shaft that can rotate in the circumferential direction of the wrist 105 is provided at the tip of the wrist 105. An end effector 107 that grips a workpiece is attached to the flange portion 106.

  The robot control device 200 is configured as a computer including a CPU and a memory. Based on the teaching data taught by the robot teaching device 300, the robot control device 200 drives a servo motor provided on each joint axis of the robot main body 100 to automatically control the robot main body 100. When there is a manual operation command from the robot teaching device 300, the robot control device 200 drives each joint axis of the robot main body 100 in accordance with the command.

  FIG. 2 is a block diagram showing the internal configuration of the robot body 100 and the robot control device 200. For simplicity of explanation, FIG. 2 shows one joint axis among the plurality of joint axes shown in FIG. The robot body 100 includes a servo motor 110 configured as a three-phase AC brushless DC motor, an absolute encoder 160 connected to the rotation shaft of the servo motor 110, a speed reducer 170 that decelerates rotation of the servo motor 110, And a joint shaft 180 driven by a servo motor 110 via a speed reducer 170.

  The absolute encoder 160 is a detector that detects the physical absolute position of the rotation shaft of the servo motor 110. The absolute position is represented by encoder position information including position information in one rotation and position information in multiple rotations. The position information within one rotation is information indicating the absolute position (absolute angle) of the rotating shaft of the servo motor 110 within one rotation from the origin of the absolute encoder 160, and is represented by a 16-bit value, for example. Further, the multi-rotation position information is information indicating the cumulative number of rotations (cumulative angle) of the rotation shaft of the servo motor 110 counted with reference to the origin, and is represented by a 16-bit value, for example.

  The absolute encoder 160 includes a multi-rotation position information storage unit 162 for storing multi-rotation position information among the encoder position information described above. This multi-rotation position information storage unit is a volatile memory, and is backed up by a battery 164. For this reason, when the voltage of the battery 164 decreases, the multi-rotation position information stored in the multi-rotation position information storage unit 162 is lost. In addition, even if the voltage of the battery 164 falls, the information within one rotation is not lost. This is because the absolute position within one rotation can always be obtained by the rotating plate provided in the absolute encoder 160.

  The robot control device 200 includes an inverter 210 that supplies three-phase AC power to the servo motor 110 of the robot body 100, a drive circuit 220 that performs switching control of the inverter 210, an interface 230 to which the robot teaching device 300 is connected, and a CPU 240. And a storage unit 250. The CPU 240 functions as a drive control unit 260, a first calibration processing unit 270, and a second calibration processing unit 280 by executing a predetermined control program 251 stored in the storage unit 250.

  For example, the first calibration processing unit 270 has a function for performing calibration first at the timing when the robot body 100 is installed in equipment in a factory. Calibration refers to obtaining a correction value for matching the axial position on the control of the joint axis 180 with the physical position output from the absolute encoder 160. Hereinafter, the calibration executed by the first calibration processing unit 270 is referred to as “initial calibration processing”. As shown in FIG. 2, the first calibration processing unit 270 includes a first position information acquisition unit 271, a position range determination unit 272, a correction value determination unit 273, a position recording unit 274, and a movement request unit 275. , Including.

  The first position information acquisition unit 271 has a function of acquiring encoder position information from the absolute encoder 160 when performing an initial calibration process. The position range determination unit 272 determines whether or not the position represented by the position information in one rotation of the encoder position information acquired by the first position information acquisition unit 271 is included in a predetermined allowable range. Have Details of the allowable range will be described later. The correction value determination unit 273 calculates the correction value described above based on the encoder position information acquired by the first position information acquisition unit 271 and stores the correction value in the storage unit 250 in a nonvolatile manner. A specific method for calculating the correction value will be described later. The position recording unit 274 includes information (hereinafter, referred to as joint axis position information) indicating the position of the joint axis when the correction value is determined, and encoder position information acquired by the first position information acquisition unit 271. Are stored in the storage unit 250 in a nonvolatile manner. The movement request unit 275 changes the calibration position when the position represented by the position information within one rotation of the encoder position information acquired by the first position information acquisition unit 271 is not included in the above-described allowable range. It has a function requested to the user.

  The second calibration processing unit 280 has a function for performing calibration again at an arbitrary timing after the initial calibration processing. Hereinafter, the calibration performed by the second calibration processing unit 280 is referred to as “recalibration processing”. For example, when the voltage of the battery 164 included in the absolute encoder 160 decreases and the multi-rotation position information is lost, the recalibration process is executed according to a user instruction after the battery 164 is replaced with a new battery. Is done. The second calibration processing unit 280 includes a second position information acquisition unit 281 and a correction value update unit 282.

  The second position information acquisition unit 281 has a function of acquiring encoder position information from the absolute encoder 160. The correction value update unit 282 regenerates the correction value based on the encoder position information stored in the storage unit 250, the joint axis position information, and the encoder position information acquired by the second position information acquisition unit 281. It has a function of determining and recording in the storage unit 250.

  The drive control unit 260 outputs a signal for driving the servo motor 110 to the drive circuit 220 based on the teaching data 252 stored in advance in the storage unit 250. At this time, the drive control unit 260 acquires the encoder position information from the absolute encoder 160 of the robot body 100, and drives the servo motor 110 based on the encoder position information and the correction value stored in the storage unit 250. Feedback control.

  The drive control unit 260 performs feedback control by calculating the position of the joint axis by the following equation (1). Specifically, the correction value determined by the first calibration processing unit 270 or the second calibration processing unit 280 is added to the absolute position output from the absolute encoder 160, and the total value is added to the gear of the speed reducer 170. The value divided by the ratio is the control position of the joint shaft 180. The gear ratio of the speed reducer 170 takes a value of about 50 to 120 according to the type of the joint shaft 180 and can be set to 80, for example.

  Joint axis position = (encoder output position + correction value) / gear ratio (1)

  The first calibration processing unit 270 calculates the correction value in the above formula (1) based on the following formula (2). Specifically, the gear ratio is added to the control position of the joint axis at the time of calibration, and is obtained by subtracting the absolute position (position within one rotation + multi-turn position) output from the integrated value. be able to. Note that the correction value re-determination method performed by the second calibration processing unit 280 will be described later.

  Correction value = Joint axis position * Gear ratio-Encoder output position (2)

B. Initial calibration process:
FIG. 3 is a flowchart of the initial calibration process executed by the first calibration processing unit 270. This initial calibration process is executed, for example, when the execution of initial calibration is instructed by the user through the robot teaching device 300 when the robot main body 100 is assembled in equipment or the like in the factory.

  When the initial calibration process is executed, first, the user moves the joint axis 180 of the robot main body 100 to an arbitrary position and designates the calibration position (step S100). The user can move the joint axis 180 by using the robot teaching device 300, and can also move the joint axis 180 by grasping the arm of the robot main body 100.

  When the calibration position is designated, the first calibration processing unit 270 acquires encoder position information from the absolute encoder 160 by the first position information acquisition unit 271 (step S105). The first position information acquisition unit 271 further acquires position information within one rotation from the encoder position information (step S110).

  When the position information within one rotation is acquired, the position range determination unit 272 determines whether the position within one rotation represented by the position information within one rotation is within a predetermined allowable range that does not include the origin of the absolute encoder 160. It is determined whether or not (step S115).

  FIG. 4 is an explanatory diagram showing an allowable range of the position within one rotation in the present embodiment. In the present embodiment, as shown in FIG. 4, the position range determination unit 272 defines a range excluding a range of ± 45 ° from the origin, that is, a range from + 45 ° to + 315 ° with respect to the origin, It is determined whether the position within one rotation is within this allowable range. As a result of this determination, if the position within one rotation is not within the allowable range, the movement request unit 275 requests the user to move the joint shaft 180 through the robot teaching device 300 (step S120), and the process proceeds to step S100. return. When the joint shaft 180 is moved, the processes in steps S100 to S115 are repeated until the position within one rotation after the movement is within the allowable range described above. In step S120, the robot control device 200 may cause the user to display a warning through the robot teaching device 300 until, for example, the movement of the joint axis 180 by the user is within an allowable range. .

  If it is determined in step S115 that the position within one rotation is within the allowable range, a correction value is calculated by the correction value determination unit 273 according to the equation (2) (step S125). When the correction value is calculated by the correction value determination unit 273, the calculated correction value is stored in the storage unit 250 (step S130). When the correction value is stored in the storage unit 250, the position recording unit 274 stores the encoder position information last acquired in step S105 and the joint axis indicating the control position of the joint axis at the time when the encoder position information is acquired. The position information is stored in the storage unit 250 (steps S135 and S140). In the present embodiment, in step S135, the entire encoder position information is stored in the storage unit 250, but only the position information within one rotation may be stored in the encoder position information.

  The initial calibration process is completed by the series of processes described above. After completion of the initial calibration process, the user preferably performs marking on the calibration position designated in step S100 on the joint shaft 180 or the calibration position moved in step S120. By doing so, it is possible to easily align the joint axis 180 to the calibration position in the recalibration process described later.

C. Recalibration process:
FIG. 5 is a flowchart of the recalibration process executed by the second calibration processing unit 280. This recalibration process is executed when the battery 164 included in the absolute encoder 160 is replaced and the execution of the recalibration process is instructed through the robot teaching apparatus 300 by the user.

  When the recalibration process is executed, first, the user moves the joint axis 180 of the robot body 100 to the calibration position designated in the initial calibration process (step S200). As in the initial calibration process, the user can move the joint axis 180 by using the robot teaching apparatus 300, and can also move the joint axis 180 by grasping the arm of the robot body 100.

  When the joint shaft 180 is moved to the calibration position, the encoder position information is acquired from the absolute encoder 160 by the second position information acquisition unit 281 (step S205). After acquiring the encoder position information, the second calibration processing unit 280 reads out the encoder position information stored in the initial calibration process from the storage unit 250 (step S210). Then, the position information within one rotation of the encoder position information acquired from the absolute encoder 160 is replaced with position information within one rotation within the encoder position information read from the storage unit 250 (step S215).

  After the replacement of the position information within one rotation, the correction value update unit 282 reads the joint axis position information stored in the storage unit 250 in the initial calibration process (step S220), and the joint axis position information and one in step S215. Using the encoder position information in which the in-rotation position information is replaced, a correction value is calculated based on the above equation (2) (step S225). Then, the correction value already stored in the storage unit 250 is updated with the calculated correction value (step S230). Note that the encoder position information and the joint axis position information saved in the storage unit 250 by the initial calibration process are saved as they are without being updated.

  According to the robot control apparatus 200 of the present embodiment described above, in the initial calibration process described above, the calibration position of the joint shaft 180 is set at a position within one rotation that is somewhat distant from the origin position of the absolute encoder 160. . Therefore, at the time of recalibration, when the joint shaft 180 is aligned with the calibration position, the multi-rotation position becomes unstable (more specifically, the multi-rotation position varies within a range of ± 1 rotation). Can be suppressed. Therefore, even in a situation where the robot body 100 is fixed in the facility and the joint shaft 180 cannot be calibrated at a position where positioning is easy, such as a mechanical end, a highly reproducible calibration position is provided at any position. It becomes possible to set.

  In the present embodiment, as a result of setting the calibration position as described above, the multi-rotation position information is accurately output from the absolute encoder 160 at the time of recalibration. Therefore, even when the multi-rotation position information is lost due to the voltage drop of the battery 164 of the absolute encoder 160 and recalibration is necessary, the calibration can be performed accurately. As a result, it is not necessary to perform teaching again with battery replacement, and thus the robot can be returned quickly.

  Furthermore, according to the recalibration process described above, the correction value is calculated using the position within one rotation in the encoder position information stored in the initial calibration process. For this reason, even if there are factors such as hysteresis of the speed reducer 170, force adjustment at the time of alignment, or positional deviation due to the amount of division during alignment at the time of recalibration processing, it is affected by them. Therefore, the calibration can be performed accurately with the same accuracy as the initial calibration.

  Here, the reason why the correction value can be calculated at the time of recalibration using the position within one rotation in the encoder position information stored in the storage unit 250 by the initial calibration processing will be described. First, the joint shaft 180 with the robot main body 100 was pressed against the mechanical end, and the displacement of the joint shaft 180 was measured when the pressing force was changed. Then, the amount of deviation was about 0.26 ° at the maximum. For example, when the length of the arm is 854.88 mm, this deviation is 3.879 mm (= 854.88 mm) at the tip of the arm. Xsin 0.26 °). However, this angle of 0.26 ° is only an angle of 20.8 ° (= 0.26 ° × 80) at the rotating shaft level of the servo motor 110 when the gear ratio of the speed reducer 170 is 80. Further, even if the gear ratio is calculated as 150, it is about 39.0 °. That is, it can be said that the influence of the above-described deviation factor falls within the deviation within one rotation of the rotation shaft of the servo motor 110 even if many estimates are made. Therefore, in the recalibration process of the present embodiment, the initial calibration is performed by replacing only the position information in one rotation with the value stored in the storage unit 250 while maintaining the multi-rotation position information acquired from the absolute encoder 160 as it is. The same highly accurate calibration as when executing the calibration process can be performed. In the recalibration process, the value obtained at the time of recalibration is used as it is for the multi-rotation position information. However, in this embodiment, the calibration position is the absolute encoder 160 as described above. Since it is not set near the origin, the detection accuracy of the multi-rotation position is increased. Therefore, according to the present embodiment, it is possible to perform calibration with extremely high accuracy by the highly accurate position within one rotation and the multiple rotation position.

D. Variation:
As mentioned above, although one Example of this invention was described, this invention is not limited to such an Example, A various structure can be taken in the range which does not deviate from the meaning. For example, the following modifications are possible.

・ Modification 1:
In the above embodiment, the calibration position is set so that the position within one rotation of the rotation axis of the servo motor 110 falls within the range (allowable range) of + 45 ° to + 315 ° from the origin. Any value can be set as long as the fluctuation of the number can be suppressed. For example, ranges of + 30 ° to + 330 °, + 60 ° to + 300 °, + 90 ° to + 270 °, and the like can be set as allowable ranges. Further, the allowable range may be a range in which the plus direction and the minus direction are asymmetric from the origin.

  In addition, for example, as shown in the following formulas (3) and (4), the allowable range described above is 360 degrees from the entire range of the position within one rotation, starting from the origin, with the number of gears of the rotation shaft of the servo motor 110. The range excluding the position delayed by the divided value A to the position advanced to this value A (in other words, the value A is subtracted from 360 ° from the position corresponding to the value A in the entire range of the position within one rotation. Range up to the position corresponding to the measured value).

Value A = 360 ° / number of gears (3)
Value A ≦ Allowable Range ≦ 360 ° −Value A (4)

  The alignment of the joint shaft to the calibration position is restricted by the resolution of the gear provided on the rotation shaft of the motor. Therefore, as described above, if the range excluding the range where the position is moved back and forth by one gear from the origin is set as the allowable range, the calibration position can be set in a wider range. Note that the number of gears of the rotating shaft of the motor is, for example, about 50 to 60, and about 100 at most.

Modification 2
In the above-described embodiment, an example in which initial calibration and recalibration are performed for one joint axis 180 has been described. Can be applied.

・ Modification 3:
In the above embodiment, the recalibration process is performed after the battery 164 is replaced. However, at any timing after the initial calibration process is completed regardless of whether the battery 164 is replaced. Also good. Further, the number of times the initial calibration process and the recalibration process are executed is not particularly limited.

-Modification 4:
In the above embodiment, the initial calibration process and the recalibration process are executed by the robot control apparatus 200, but may be executed by the robot teaching apparatus 300. In this case, the robot teaching device 300 corresponds to the robot control device of the present application. Further, when the processing contents are distributed between the robot control device 200 and the robot teaching device 300, it is also possible to collect both of them as the robot control device of the present application.

-Modification 5:
In the above embodiment, the initial calibration is performed at an arbitrary position. However, the initial calibration may be performed at a position with high reproducibility of alignment such as a mechanical end or a predetermined marking position.

Modification 6:
In the configuration of the robot control device 200 described above, functions realized by software may be realized by hardware, and vice versa.

DESCRIPTION OF SYMBOLS 10 ... Robot system 100 ... Robot main body 101 ... Base part 102 ... Shoulder part 103 ... Lower arm 104 ... Upper arm 105 ... Wrist 106 ... Flange part 107 ... End effector 110 ... Servo motor 160 ... Absolute encoder 162 ... Multi-rotation position information storage Unit 164 ... Battery 170 ... Speed reducer 180 ... Joint axis 200 ... Robot controller 210 ... Inverter 220 ... Drive circuit 222 ... Teaching data 230 ... Interface 240 ... CPU
250: Storage unit 251: Control program 252 ... Teaching data 260 ... Drive control unit 270 ... First calibration processing unit 271 ... First position information acquisition unit 272 ... Position range determination unit 273 ... Correction value determination unit 274 ... Position recording unit 280 ... second calibration processing unit 281 ... second position information acquisition unit 282 ... correction value update unit 300 ... robot teaching device

Claims (5)

Controlling a robot having a joint axis, a motor that drives the joint axis, and an absolute encoder that outputs position information including a position within one rotation representing a physical position of the rotation axis of the motor and a multi-rotation position A robot controller that
A first position information acquisition unit that acquires position information from the absolute encoder when the joint axis is moved to an arbitrary calibration position on the joint axis;
It is determined whether the position within one rotation included in the position information acquired by the first position information acquisition unit is included in a predetermined allowable range that does not include an origin serving as a reference for counting the multiple rotation positions. A position range determination unit;
When the position within one rotation included in the position information acquired by the first position information acquisition unit is not included in the allowable range, the calibration position is included until the position within one rotation is included in the allowable range. A movement requesting unit that requests movement of
When the position within one rotation included in the position information acquired by the first position information acquisition unit is included in the allowable range, based on the position information and the control position of the joint axis, A correction value determination unit for determining a correction value for correcting the physical position and the control position;
A robot control device comprising: The robot control device according to claim 1,
The allowable range excludes from the entire range of the position within one rotation to a position advanced from the position delayed by a value obtained by dividing 360 ° by the number of gears of the rotation shaft of the motor from the origin. Robot controller that is in range. The robot control device according to claim 1 or 2, further comprising:
A control-unit-side storage unit that stores at least the position within one rotation and the control position of the joint axis in the position information when the correction value is determined;
A second position information acquisition unit that acquires position information from the absolute encoder when the joint axis is moved to the calibration position again after the correction value is determined;
The position within one rotation in the position information acquired by the second position information acquisition unit is changed to the position within one rotation stored in the storage unit on the control device side, and the position information after the change and the control device And a correction value updating unit that updates the correction value based on a control position of the joint axis stored in a side storage unit. The robot control device according to claim 3 ,
The absolute encoder is
A volatile encoder-side storage unit that holds a multi-rotation position of the position information;
A battery for battery backup of the encoder side storage unit,
The second position information acquisition unit, after the correction value is determined by the correction value determination unit and after the battery is replaced and the multi-rotation position is lost from the encoder-side storage unit, A robot controller that acquires position information. A robot having a joint shaft, a motor that drives the joint shaft, and an absolute encoder that outputs position information including a position within one rotation representing a physical position of the rotation shaft of the motor and a multi-rotation position. A calibration method in which a control device calibrates,
A first position information acquisition step of acquiring position information from the absolute encoder when the joint axis is moved to an arbitrary calibration position on the joint axis;
A position for determining whether or not the position within one rotation included in the position information acquired by the first position information step is included in a predetermined allowable range that does not include an origin serving as a reference for counting the multiple rotation positions. A range determination step;
When the position within one rotation included in the position information acquired by the first position information acquisition unit is not included in the allowable range, the calibration position is included until the position within one rotation is included in the allowable range. A movement request process for requesting movement of
When the position within one rotation included in the position information acquired by the first position information acquisition unit is included in the allowable range, based on the position information and the control position of the joint axis, A correction value determining step for determining a correction value for correcting the physical position and the control position;
Calibration method including:

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