JP2018036097A - Angle position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angle position detector with which it is possible to correct a detection error after assembling an encoder to an arm.SOLUTION: Provided is an angle position detector comprising an input shaft encoder 40 and an output shaft encoder 50, said detector calculating an input-side angle position that is an angle position of a prescribed shaft 12 on the basis of the angle position of an input shaft 21 detected by the input shaft encoder 40; calculating a load moment acting on the output shaft of a reduction gear 30 on the basis of a current flowing in a motor 20; calculating a detection error of the output shaft encoder 50 on the basis of the calculated input-side angle position, an output-side angle position that is the angle position of a prescribed shaft detected by the output shaft encoder, the calculated load moment, and the rigidity of the reduction gear 30; and correcting the output-side angle position detected by the output shaft encoder 50 by the calculated detection error.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an angular position detection device that detects an angular position of a rotation axis of a robot or the like.

  2. Description of the Related Art Conventionally, there is an angular position detection device of this type that corrects a detection error caused by eccentricity when an encoder rotation shaft and a rotation disk are attached (see Patent Document 1). Moreover, in the thing of patent document 1, the output-shaft encoder is provided in the structure which transmits rotation of a motor to an output shaft via a reduction gear. The difference between the angular position based on the detected value of the input shaft encoder and the angular position based on the detected value of the output shaft encoder is corrected as a torsion angle due to elastic deformation of the speed reducer.

JP-A-2015-194462

  However, even when trying to detect the correction value of the detection error due to eccentricity with the input / output axis encoder, the arm or deceleration speed depends on the weight of the arm itself, the tool attached to the arm, the work, etc. in addition to the eccentricity. The amount of bending or twisting of the machine is mixed and detected. Since the eccentricity is determined after the encoder is assembled to the arm, it is difficult to disassemble or detect it in advance so that the influence of the arm is not mixed. It is also possible to geometrically calculate the influence of the arm from the design value of the robot, but based on the deviation between the design value, such as the arm length and the robot installation angle, and the actual machine, or the arm angle before the correction in the first place The correction value cannot be obtained accurately due to the fact that the deviation is to be calculated.

  The present invention has been made to solve these problems, and a main object of the present invention is to provide an angular position detection device capable of correcting a detection error after an encoder is assembled to an arm.

The first means for solving the above problems is as follows.
An angle provided with an input shaft encoder that detects an angular position of an input shaft of a speed reducer to which rotation of a motor is input, and an output shaft encoder that detects an angular position of a predetermined shaft that rotates together with the output shaft of the speed reducer A position detecting device,
An input-side angular position calculation unit that calculates an input-side angular position that is an angular position of the predetermined axis based on an angular position of the input shaft detected by the input shaft encoder;
A load moment calculating unit that calculates a load moment acting on the output shaft based on a current flowing through the motor;
The input-side angular position calculated by the input-side angular position calculation unit, the output-side angular position that is the angular position of the predetermined axis detected by the output shaft encoder, and the load moment calculation unit A detection error calculation unit for calculating a detection error of the output shaft encoder based on a load moment and the rigidity of the reduction gear;
A correction unit that corrects the output-side angular position detected by the output shaft encoder based on the detection error calculated by the detection error calculation unit;
Is provided.

  According to the above configuration, the angular position of the input shaft of the reduction gear to which the rotation of the motor is input is detected by the input shaft encoder. The output shaft encoder detects the angular position of a predetermined shaft that rotates integrally with the output shaft of the speed reducer. The predetermined shaft may be a shaft that rotates integrally with a member attached to the output shaft of the speed reducer, or may be the output shaft itself of the speed reducer.

  Then, the input side angular position calculation unit calculates an input side angular position that is an angular position of the predetermined axis based on the angular position of the input shaft detected by the input shaft encoder. The input side angular position can be calculated based on the angular position of the input shaft and the reduction gear ratio of the speed reducer. This input-side angular position corresponds to an angular position of a predetermined axis in a state where it is not affected by torsion due to deflection and elastic deformation.

  Here, when a member constituting the speed reducer bends or twists due to elastic deformation, the angular position of the predetermined axis detected by the output shaft encoder changes. The deflection angle of the members constituting the speed reducer and the torsion angle due to elastic deformation increase as the load moment acting on the output shaft increases, and increase as the rigidity of the speed reducer decreases. These changes in the detected angular position due to deflection and torsion are the difference between the input-side angular position calculated by the input-side angular position calculation unit and the output-side angular position that is the angular position of the predetermined axis detected by the output shaft encoder. It corresponds to. The load moment acting on the output shaft has a correlation with the current flowing through the motor, and can be calculated based on the current flowing through the motor. Therefore, the detection error calculation unit includes the input side angular position calculated by the input side angular position calculation unit, the output side angular position detected by the output shaft encoder, the load moment calculated by the load moment calculation unit, the deceleration The detection error of the output shaft encoder can be calculated based on the rigidity of the machine.

  The correction unit corrects the output-side angular position detected by the output shaft encoder based on the detection error calculated by the detection error calculation unit. For this reason, even if a detection error occurs according to each use state after the encoder is assembled to the arm, the detection error can be corrected after the encoder is assembled to the arm. As a result, it is possible to accurately detect the angular position of the predetermined axis that rotates integrally with the output shaft of the speed reducer.

  In a state where the output shaft of the reduction gear is stationary by the driving torque of the motor, the driving torque of the motor and the load moment acting on the output shaft of the reduction gear are balanced. For this reason, the change in the detected angular position due to deflection and torsion is equal to the change in the angular position calculated based on the load moment and the reduction gear rigidity.

  In this regard, in the second means, the detection error calculation unit, in a state where the output shaft is stationary by the driving torque of the motor, the input side angular position calculated by the input side angular position calculation unit, The detection error is calculated based on the output side angular position detected by the output shaft encoder, the load moment calculated by the load moment calculation unit, and the rigidity of the speed reducer. Therefore, the detection error can be calculated by making the output shaft of the reduction gear stationary by the driving torque of the motor.

  The load moment acting on the output shaft of the speed reducer differs between when the motor is rotated forward and when it is rotated reversely. For example, the magnitude of the frictional force generated by the speed reducer varies depending on the rotation direction of the motor, or the relationship between the direction of gravity and the direction of movement of the arm varies. For this reason, the current flowing through the motor depends on the direction of rotation of the motor, and the load moment can be calculated appropriately based on the current flowing through the motor without considering the effect of the current depending on the direction of rotation of the motor. Can not.

  In this regard, in the third means, the load moment calculation unit is based on the average current of the current that flows when the motor rotates in the forward direction and the current that flows when the motor rotates in the reverse direction at each angular position of the output shaft. The load moment acting on the output shaft at each angular position of the output shaft is calculated. For this reason, a change in current due to the rotation direction of the motor can be canceled, and the load moment can be appropriately calculated based on the current flowing through the motor.

  The detection error calculation unit corresponds to the input side angular position calculated by the input side angular position calculation unit, the output side angular position detected by the output shaft encoder, and the input side angular position. The detection error is calculated based on the load moment calculated by the load moment calculator and the rigidity of the speed reducer. Therefore, it is not necessary to make the output shaft of the reduction gear stationary by the motor driving torque, and the detection error can be calculated quickly while rotating the output shaft.

  Whether the detection error is calculated with the output shaft of the reduction gear stationary with the motor drive torque, or the detection error is calculated while rotating the output shaft, the detection error is calculated for each angular position of the output shaft. There is a need to. For this reason, it may take a long time to start the operation of the angular position detection device.

  In this regard, in the fourth means, the detection error calculation unit includes the detection error measured in advance corresponding to the angular position of the output shaft as a table, and is calculated by the input side angular position calculation unit. The detection error is calculated based on the input side angular position and the table. Therefore, when the operation of the angular position detection device is started, it is not necessary to newly calculate a detection error for each angular position of the output shaft, and the operation of the angular position detection device can be started quickly.

The perspective view which shows a robot and a robot controller. The schematic diagram which shows the joint of the arm of a robot. The schematic diagram which shows the state which an arm bends. The graph which shows the result of having calculated | required the measured value and calculated value of the eccentric error with respect to an input side angular position in the state where load moment does not act.

(First embodiment)
Hereinafter, a first embodiment will be described with reference to the drawings. This embodiment is embodied in an angular position detection device that detects an angular position of a rotation axis in a joint that connects rotation axes of an articulated robot.

  As shown in FIG. 1, the operation state of the robot 10 is controlled by a robot controller 80. The robot 10 is a 6-axis vertical articulated robot, for example, and includes a first axis 11 and a second axis 12 as arms.

  FIG. 2 is an enlarged schematic view of a portion surrounded by a circle A in FIG. The arm of the robot 10 includes a first shaft 11, a second shaft 12, a motor 20, a speed reducer 30, an input shaft encoder 40, an output shaft encoder 50, and the like.

  A motor 20 and a speed reducer 30 are fixed to the first shaft 11. The drive shaft of the motor 20 is an input shaft 21 that inputs rotation to the speed reducer 30. The driving state of the motor 20 is controlled by the robot controller 80. An input shaft encoder 40 that detects the angular position of the input shaft 21 is attached to the motor 20. The speed reducer 30 may be fixed to the motor 20.

  The input shaft encoder 40 includes a disk-shaped disk 41, a detection element 42, and the like. The disk 41 is concentrically attached to the input shaft 21. The detection element 42 is attached to the housing of the input shaft encoder 40. The detection element 42 is disposed to face a predetermined position on the outer peripheral edge of the detection surface of the disk 41. The detection element 42 detects an on / off signal corresponding to the angular position of the disk 41. The on / off signal (that is, the angular position) detected by the detection element 42 is input to the robot controller 80. As the input shaft encoder 40, a transmissive optical encoder, a reflective optical encoder, a magnetic encoder, or the like can be employed.

  The speed reducer 30 decelerates the rotation of the input shaft 21 at a predetermined reduction ratio and outputs it as the rotation of the second shaft 12. That is, the second shaft 12 (corresponding to a predetermined shaft) rotates integrally with the output shaft of the speed reducer 30. As the speed reducer 30, a wave gear type speed reducer, a planetary gear type speed reducer, or the like can be employed. An output shaft encoder 50 that detects the angular position of the second shaft 12 is attached to the second shaft 12. Note that a configuration in which the output shaft encoder 50 is attached to the first shaft 11 or the speed reducer 30 may be employed. In that case, the output shaft encoder 50 detects the angular position of the output shaft (corresponding to a predetermined shaft) of the speed reducer 30.

  The output shaft encoder 50 includes a disk-shaped disk 51, a detection element 52, and the like. The disk 51 is concentrically attached to the detection shaft 31 attached to the second shaft 12. The detection element 52 is attached to the housing of the output shaft encoder 50 or the first shaft 11. The detection element 52 is disposed to face a predetermined position on the outer peripheral edge of the detection surface of the disk 51. The detection element 52 detects an on / off signal corresponding to the angular position of the disk 51. The on / off signal (that is, the angular position) detected by the detection element 52 is input to the robot controller 80. As the output shaft encoder 50, a transmissive optical encoder, a reflective optical encoder, a magnetic encoder, or the like can be employed.

  The input shaft 21, the disk 41, the detection shaft 31, and the disk 51 are arranged concentrically. That is, the center lines of the input shaft 21, the disc 41, the detection shaft 31, and the disc 51 coincide with each other at the axis C1. However, the center of the input shaft 21 and the center of the detection shaft 31 or the center of the disk 51 are eccentric when the input shaft encoder 40 and the output shaft encoder 50 are assembled to the arm. Further, the eccentricity between the center of the input shaft 21 and the center of the disk 41 has been eliminated in advance, or the detection error of the input shaft encoder 40 caused by the eccentricity between the center of the input shaft 21 and the center of the disk 41 has been corrected. It shall be.

  The robot controller 80 is a microcomputer including a CPU, a ROM, a RAM, an input / output port, a drive circuit, and the like. The robot controller 80 inputs detection values from various sensors such as the input shaft encoder 40 and the output shaft encoder 50, and controls the driving state of various actuators such as the motor 20. The robot controller 80 calculates the angular position of the disk 41, that is, the input shaft 21, based on the on / off signal detected by the detection element 42 of the input shaft encoder 40. Then, the robot controller 80 (corresponding to the input side angular position calculation unit) is based on the angular position of the input shaft 21 and the reduction ratio of the speed reducer 30, and is the input side that is the angular position of the second shaft 12 (detection shaft 31). Calculate the angular position. This input-side angular position corresponds to the angular position of the second shaft 12 in a state where it is not affected by torsion due to deflection and elastic deformation. Further, the robot controller 80 (corresponding to the output side angular position calculation unit) outputs the disk 51, that is, the angular position of the second shaft 12, based on the on / off signal detected by the detection element 52 of the output shaft encoder 50. The side angular position is calculated. The input shaft encoder 40, the output shaft encoder 50, and the robot controller 80 constitute an angular position detection device.

  FIG. 3 is a schematic diagram illustrating a state in which the arm of the robot 10 is bent. As shown in the figure, the load F (gravity) is applied to the second shaft 12 of the arm due to the mass W corresponding to the mass of the second shaft 12 itself, the mass of the tool attached to the arm, the mass of the workpiece to be gripped, and the like. Act. When a load moment is applied to the second shaft 12 by the load F, deflection occurs according to the rigidity of the speed reducer 30 and the second shaft 12. Note that when an external force in the direction of twisting the second shaft 12 acts on the second shaft 12, the second shaft 12 is twisted due to elastic deformation. The deflection angle of the reduction gear 30 and the second shaft 12 and the torsion angle due to elastic deformation increase as the load moment acting on the second shaft 12 increases, and increase as the rigidity of the reduction gear 30 and the second shaft 12 decreases. Become. Due to such deflection and twist, the angular position θ of the second shaft 12 detected by the output shaft encoder 50 changes, and a detection error occurs.

  Therefore, in this embodiment, the robot controller 80 (corresponding to a load moment calculation unit, a detection error calculation unit, and a correction unit) detects the angular position (output side) of the second shaft 12 detected by the output shaft encoder 50 as follows. The angular position θout) is corrected.

  The output-side angular position θout is a composite of the true angular position θa of the second shaft 12 (angular position with respect to the first shaft 11) and the eccentric error Δθe caused by the eccentricity during assembly. The angular position θa includes an angular error Δθg due to deflection caused by gravity acting on the mass W and a torsion angle Δθt due to external force acting on the second shaft 12, and the angular position to be detected by the output shaft encoder 50. It corresponds to. That is, the output side angular position θout is expressed as follows.

θout = θa + Δθe (1)
Here, the detected angle difference Δθd between the input side angular position θin, which is the angular position of the second shaft 12 calculated based on the angular position of the input shaft 21 detected by the input shaft encoder 40, and the output side angular position θout is: It is expressed as follows.

Δθd = θout−θin (2)
On the other hand, the detected angle difference Δθd is a composite of an angle error Δθg due to deflection caused by gravity acting on the mass W, a torsion angle Δθt due to an external force acting on the second shaft 12, and an eccentric error Δθe. That is, the detected angle difference Δθd can also be expressed as follows.

Δθd = Δθg + Δθt + Δθe (3)
Further, when the output shaft of the speed reducer 30, that is, the second shaft 12 is stationary by the driving torque of the motor 20, the driving torque of the motor 20 and the load moment M acting on the second shaft 12 are balanced. For this reason, the change in the detected angular position due to deflection and torsion is equal to the change in the angular position calculated based on the load moment M, the reduction gear 30 and the rigidity k of the second shaft 12. That is, in the state where the second shaft 12 is stopped by the driving torque of the motor 20, the following expression is established.

Δθg + Δθt = M / k (4)
The load moment M can be calculated based on the detected current by detecting the current flowing through the motor 20 with a current sensor or the like.

  When Expression (3) is transformed, the following is obtained.

Δθe = Δθd− (Δθg + Δθt) (5)
Substituting Δθd in equation (2) and (Δθg + Δθt) in equation (4) into equation (5) results in the following.

Δθe = (θout−θin) −M / k (6)
In Expression (6), the output-side angular position θout, the input-side angular position θin, and the load moment M can be calculated, respectively, and the stiffness k is a known value. For this reason, the eccentricity error Δθe can be calculated from the equation (6). Then, by changing the angular position of the second shaft 12 by a predetermined angle, the second shaft 12 is made stationary by the driving torque of the motor 20, and the eccentric error Δθe is calculated by the equation (6). Repeat over the movable range.

  When formula (1) is transformed, it becomes as follows.

θa = θout−Δθe (7)
Therefore, at each angular position of the second axis 12, by substituting the detected output side angular position θout and the eccentric error Δθe calculated by the expression (6) into Expression (7), The true angular position θa can be calculated. That is, the output-side angular position θout can be corrected by the angle error Δθg due to deflection, the twist angle Δθt due to external force, and the eccentric error Δθe. Furthermore, by using the corrected output side angular position θout, it is possible to estimate the load torque acting on the arm and the position of the tip of the arm with high accuracy.

  The embodiment described in detail above has the following advantages.

  The deflection angle of the members constituting the speed reducer 30 and the torsion angle Δθt due to elastic deformation increase as the load moment M acting on the second shaft 12 increases, and increase as the rigidity k of the speed reducer 30 decreases. The change (Δθg + Δθt) of the detected angular position due to these deflections and twists is the input-side angular position θin that is the angular position of the second shaft 12 calculated based on the angular position detected by the input shaft encoder 40, and the output shaft encoder. This corresponds to the difference from the output-side angular position θout which is the angular position of the second shaft 12 detected by 50. Further, the load moment M acting on the second shaft 12 has a correlation with the current flowing through the motor 20, and can be calculated based on the current flowing through the motor 20. Therefore, the detection error (Δθe) of the output shaft encoder 50 can be calculated based on the input side angular position θin, the output side angular position θout, the load moment M, and the rigidity k of the speed reducer 30.

  The output side angular position θout detected by the output shaft encoder 50 is corrected by the calculated detection error. For this reason, even if a detection error occurs according to each use state after the encoders 40 and 50 are assembled to the arm, the detection errors can be corrected after the encoders 40 and 50 are assembled to the arm. As a result, the angular position θa of the second shaft 12 that rotates integrally with the output shaft of the speed reducer 30 can be accurately detected.

  In a state where the second shaft 12 of the speed reducer 30 is stationary by the driving torque of the motor 20, the driving torque of the motor 20 and the load moment M acting on the second shaft 12 of the speed reducer 30 are balanced. For this reason, the change (Δθg + Δθt) of the detected angular position due to deflection and torsion is equal to the change (M / k) of the angular position calculated based on the load moment M and the rigidity k of the speed reducer 30. Therefore, the robot controller 80 has the input side angular position θin, the output side angular position θout, the load moment M, and the rigidity k of the speed reducer 30 in a state where the second shaft 12 is stationary by the driving torque of the motor 20. Based on the above, a detection error (Δθe) is calculated. Therefore, the detection error can be calculated by making the second shaft 12 of the speed reducer 30 stationary by the driving torque of the motor 20.

(Second Embodiment)
Hereinafter, the second embodiment will be described focusing on differences from the first embodiment. As in the first embodiment, the angular position of the second shaft 12 is changed by a predetermined angle, the second shaft 12 is made stationary by the driving torque of the motor 20, and the eccentricity error Δθe is calculated by Equation (6). It may take a long time to repeat this over the movable range of the second shaft 12. In the present embodiment, the detection error is calculated while moving the second shaft 12 of the speed reducer 30 by the driving torque of the motor 20.

  In FIG. 3, the load moment M acting on the output shaft of the speed reducer 30, that is, the second shaft 12 is different between when the motor 20 is rotated forward and when it is rotated reversely. . For example, the magnitude of the frictional force generated by the speed reducer 30 varies depending on the rotation direction of the motor 20, or the relationship between the direction of gravity (the direction of the load F indicated by the arrow) and the second shaft 12 of the arm varies. For this reason, the current flowing through the motor 20 depends on the rotation direction of the motor 20, and the load moment M is appropriately set based on the current flowing through the motor 20 unless the influence of the current on the rotation direction of the motor 20 is taken into consideration. Cannot be calculated.

  Therefore, in the present embodiment, the robot controller 80 (corresponding to the load moment calculation unit) has a current flowing when the motor 20 is rotated in the reverse direction and a current flowing when the motor 20 is rotated in the respective angular positions of the second shaft 12. Based on the average current, the load moment M acting on the second shaft 12 at each angular position of the second shaft 12 is calculated. Specifically, when Δθe = (θout−θin) −M / k in the above equation (6), the load moment M− is a load moment M− when the motor 20 is rotated in the reverse direction and the load moment M− when the motor 20 is rotated in the reverse direction. And the average. That is, the following equation (8) is used instead of equation (6).

Δθe = (θout−θin) − {(M +) + (M −)} / 2k (8)
The load moment M + can be calculated based on the detected current by detecting the current flowing through the motor 20 when the motor 20 is rotated forward by a current sensor or the like. The load moment M− can be calculated based on the detected current by detecting the current flowing through the motor 20 when the motor 20 is reversely rotated by a current sensor or the like.

  Here, calculating the load moment M + corresponding to each angular position while changing the angular position of the second shaft 12 by a predetermined angle in the forward rotation direction is repeated over the movable range of the second shaft 12. Further, the calculation of the load moment M− corresponding to each angular position is repeated over the movable range of the second axis 12 while changing the angular position of the second axis 12 by a predetermined angle in the reverse rotation direction.

  Then, at each angular position of the second axis 12, by substituting the detected output side angular position θout and the eccentric error Δθe calculated by the expression (8) into the above equation (7), the second axis 12 The true angular position θa is calculated.

  FIG. 4 is a graph showing a result of obtaining an actual measurement value and a calculated value of the eccentric error Δθe with respect to the input side angular position θin in a state where the load moment M does not act on the second shaft 12. The state in which the load moment M does not act on the second shaft 12 is realized by removing the tip end portion of the arm from the output shaft of the speed reducer 30 and applying no external force such as torsional force to the arm. Yes.

  As shown in the figure, the measured value of the eccentricity error Δθe indicated by the broken line and the calculated value of the eccentricity error Δθe indicated by the solid line coincide with each other with high accuracy. Therefore, even if the eccentric error Δθe is calculated while moving the second shaft 12 of the speed reducer 30 by the driving torque of the motor 20, the eccentric error Δθe can be accurately calculated. Note that, even when the eccentricity error Δθe is calculated according to the first embodiment, the measured value and the calculated value of the eccentricity error Δθe coincide with each other with high accuracy.

  This embodiment has the following advantages. Here, only differences from the first embodiment will be described.

  The robot controller 80 is configured so that each angular position of the second shaft 12 is based on the average current of the current that flows when the motor 20 rotates forward and the current that flows when the motor 20 rotates backward at each angular position of the second shaft 12. A load moment M acting on the second shaft 12 at the angular position is calculated. For this reason, a change in current due to the rotation direction of the motor 20 can be canceled, and the load moment M can be calculated appropriately based on the current flowing through the motor 20.

  The robot controller 80 detects the detection error based on the input side angular position θin, the output side angular position θout, the load moment M calculated corresponding to the input side angular position θin, and the rigidity k of the speed reducer 30. Is calculated. Therefore, it is not necessary to make the output shaft (second shaft 12) of the speed reducer 30 stationary by the driving torque of the motor 20, and the detection error can be calculated quickly while rotating the second shaft 12.

  Note that the first and second embodiments can be modified as follows.

  Whether the detection error is calculated while the output shaft (second shaft 12) of the speed reducer 30 is stationary by the drive torque of the motor 20, or the detection error is calculated while rotating the output shaft, the second It is necessary to calculate a detection error for each angular position of the shaft 12. The robot controller 80 executes such detection error calculation in the calibration of the robot 10. However, it may take a long time to start the operation of the robot 10 (angular position detection device).

  Therefore, the robot controller 80 (corresponding to the detection error calculation unit) includes a detection error measured in advance corresponding to the angular position of the second axis 12 as a table, and the calculated input side angular position θin and the table are included in the table. The detection error may be calculated based on this. According to such a configuration, when the robot 10 is calibrated (at the start of operation), it is not necessary to newly calculate a detection error for each angular position of the second axis 12, and the operation of the robot 10 can be started quickly. it can.

  A so-called manipulator can be employed in addition to the arm of the robot 10.

  DESCRIPTION OF SYMBOLS 10 ... Robot, 12 ... 2nd axis (predetermined axis), 20 ... Motor, 21 ... Input shaft, 30 ... Reducer, 40 ... Input shaft encoder, 50 ... Output shaft encoder, 80 ... Robot controller.

Claims (4)

An angle provided with an input shaft encoder that detects an angular position of an input shaft of a speed reducer to which rotation of a motor is input, and an output shaft encoder that detects an angular position of a predetermined shaft that rotates together with the output shaft of the speed reducer A position detecting device,
An input-side angular position calculation unit that calculates an input-side angular position that is an angular position of the predetermined axis based on an angular position of the input shaft detected by the input shaft encoder;
A load moment calculating unit that calculates a load moment acting on the output shaft based on a current flowing through the motor;
The input-side angular position calculated by the input-side angular position calculation unit, the output-side angular position that is the angular position of the predetermined axis detected by the output shaft encoder, and the load moment calculation unit A detection error calculation unit for calculating a detection error of the output shaft encoder based on a load moment and the rigidity of the reduction gear;
A correction unit that corrects the output-side angular position detected by the output shaft encoder based on the detection error calculated by the detection error calculation unit;
An angular position detection device comprising:   The detection error calculation unit is configured to detect the input-side angular position calculated by the input-side angular position calculation unit and the output-shaft encoder in a state where the output shaft is stopped by the driving torque of the motor. The angular position detection device according to claim 1, wherein the detection error is calculated based on an output side angular position, the load moment calculated by the load moment calculation unit, and rigidity of the reduction gear. The load moment calculation unit is configured to determine each angle of the output shaft based on an average current of a current that flows when the motor rotates in the forward direction and a current that flows when the motor rotates in the reverse direction at each angular position of the output shaft. Calculate the load moment acting on the output shaft at the position,
The detection error calculation unit corresponds to the input side angular position calculated by the input side angular position calculation unit, the output side angular position detected by the output shaft encoder, and the input side angular position. The angular position detection device according to claim 1, wherein the detection error is calculated based on the load moment calculated by a load moment calculation unit and rigidity of the speed reducer.   The detection error calculation unit includes the detection error measured in advance corresponding to the angular position of the output shaft as a table, and the input-side angular position calculated by the input-side angular position calculation unit and the table The angular position detection device according to claim 2, wherein the detection error is calculated based on the angle.

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