Abstract: A method of controlling movement of a transport robot including determining a following error of a left driving wheel and a following error of a right driving wheel according to actual moving distances of the left driving wheel and the right driving wheel and a predetermined moving trajectory; determining a deviation error between the actual moving trajectory and the predetermined moving trajectory of the transport robot based on the following error of the left driving wheel and the following error of the right driving wheel, generating a position adjustment instruction of the left driving wheel and a position adjustment instruction of the right driving wheel according to the deviation error; transmitting the position adjustment instruction of the left driving wheel and the position adjustment instruction of the right driving wheel to a first servo driving system and a second servo driving system respectively to reduce a moving deviation.

Abstract: A controller that can perform high-precision synchronous control even when the speed of a master axis changes and a machine learning device are provided.

Abstract: A motor control apparatus includes a position detector for detecting the position of a rotor of a motor, a speed detection unit for calculating a speed detection value based on a position detection value detected by the position detector, a speed command generation unit for generating a speed command which commands a rotation speed of the rotor of the motor, a correction amount calculation unit for calculating a correction amount based on the position detection value detected by the position detector, a correction processing unit for correcting the speed detection value by using the correction amount, and a torque command generation unit for generating a torque command which commands a rotational torque of the motor based on the speed command and the speed detection value corrected by the correction processing unit.

Abstract: In a method and a corresponding device for controlling a rotational speed of a drive driving a shaft, the rotational speed is controlled by a control device which is supplied with a control deviation calculated based on a desired value and an actual value for the rotational speed. The actual value for the rotational speed of the shaft is measured on the shaft with a first sensor and at least one additional sensor and the actual value is calculated from a weighted average of the individual measured values for the rotational speed obtained from the first and the at least one additional sensor.

Abstract: Provided is a reaction force compensation device capable of compensating for a reaction force caused by a motor that is continuously rotating. The reaction force compensation device is configured to compensate for a reaction force generated when a motor including a stator and a rotor, which is combined with the stator to be rotatable, is driven, and includes a housing disposed below the motor, and a rotation support member disposed between the housing and the rotor and configured to support the stator to be rotatable with respect to the housing. The stator rotates by a reaction force generated when the rotor rotates.

Abstract: Stability of a control system for a materials testing system using specified filter parameters is confirmed by inputting to the control system a test signal having a predetermined waveform, automatically monitoring the output of the materials testing system, and automatically comparing the output to a threshold. If the output exceeds the threshold, a first action is taken. If the output does not exceed the threshold, input of a command signal to the control system is permitted.

Abstract: The modular engineering system contains interacting controllers (1-3), each connected with peripheral equipment located in a zone. The controllers are universal and operate using the standard software, and their interfacing with peripheral equipment (10-15) is provided by the address micro-modules (4-9) with microprocessors 33; microprocessors have plug-and-play configuration for dynamic individual event and data processing, their transformation to the unified program code and transmission to the controller (1-3) and for transformation of the unified code of controller (1-3) to the individual commands for peripheral equipment (10-15); the single address space is organized, this provides interfacing of data exchange between peripheral equipment and controllers; and it is possible to register and receive the information about certain events.

Abstract: Position control device for electric motor inputs deviation signal between angle command and angle detection value to position control section and calculates angular velocity command, inputs deviation signal between this angular velocity command and angular velocity detection value to speed control section and calculates torque current command, and controls, according to this torque current command, the electric motor current control section.

Abstract: An anti-rebounding control apparatus is provided, which includes an anti-rebounding controller outputting a first command for setting a torque limit value to “0” if an electric motor speed value is equal to or smaller than an upper threshold value and equal to or larger than a lower threshold value in the case where a speed command value of “0” is input and outputting a second command for setting the torque limit value to a maximum value if the electric motor speed value is smaller than the lower threshold value, a torque regulator setting the torque limit value to “0” when the first command is input and setting the torque limit value to the maximum value when the second command is input, and an electric motor inverter intercepting a power that is supplied to an electric motor if the torque limit value is set to “0” and re-supplying the power to the electric motor if the torque limit value is set to the maximum value.

Abstract: A machine tool includes a main axis 30 to which a touch probe 17 is attached, a motor 15 that rotationally drives the main axis 30, a rotation angle position detector 16 that detects a rotation angle position of the motor 15, and a control device 20. The control device, when a measurement mode command for performing measurement of a workpiece by the touch probe 17 is input, multiplies a d-axis current command value Idc by a d-axis current correction coefficient K that is less than 1 to reduce the d-axis current command value Idc to a d-axis current command correction value Idc?, using a d-axis current command correction section 4. Thus, in the machine tool, small rotation vibrations of the main axis, generated when rotating the main axis to which the probe is attached and performing measurements of a workpiece, can be suppressed to thereby increase the measurement accuracy.

Abstract: A positioning control system for positioning a moving element on a basis of position command data is provided with a feedback loop. The system is also provided with a loop gain modifier for determining a loop gain, which is to be used in a following positioning operation, on a basis of a difference between an amount of overshoot measured in a current positioning operation and a predetermined tolerance or on a basis of a difference between an amount of overshoot measured in a current positioning operation and a first predetermined tolerance and a difference between an amount of undershoot measured in the current positioning operation and a second predetermined tolerance. The first and second tolerances may preferably be the same in absolute value. The moving element may specifically be a steerable mirror for drilling holes in a work by reflecting a laser beam. Also disclosed is a laser drilling machine including the system.

Abstract: Embodiments of the present invention relate to methods, systems, a machine-readable medium operable in a controller, and apparatus for controlling a multi-phase inverter that drives a multi-phase electric machine. When a sensor fault is detected, a phase current angle is computed based on the feedback stator currents, and used to estimate an angular velocity and an angular position of a rotor of the multi-phase electric machine. When the estimated angular velocity of the multi-phase electric machine is less than a transition angular velocity threshold, an open-circuit response can be applied at the multi-phase inverter by controlling all switches in the multi-phase inverter drive to be open. By contrast, when the estimated angular velocity is greater than the transition angular velocity threshold, a short-circuit response can be applied at the multi-phase inverter by controlling selected switches in the multi-phase inverter drive to connect all phases of the multi-phase inverter to a single bus (e.g.

Abstract: The damping force of a damping force generation apparatus is controlled by operating an actuator on the basis of a control input u calculated by a state feedback controller K designed such that an L2 gain of a closed loop control system S which includes a generalized plant G designed by making use of a delay-approximated model M and the state feedback controller K therefor becomes less than a previously set positive constant ?. The delay-approximated model M is designed such that a delay element R representing operation delay of the actuator and a delay compensation element R* cancelling out the delay act on a mechanical motion model of the damping force generation apparatus. The delay-approximated model M is a bilinear system, and is designed to approximate a delay-considered model which is a control model designed on the basis of the mechanical motion model of the damping force generation apparatus and in consideration of the delay.

Abstract: Position control device for electric motor inputs deviation signal between angle command and angle detection value to position control section and calculates angular velocity command, inputs deviation signal between this angular velocity command and angular velocity detection value to speed control section and calculates torque current command, and controls, according to this torque current command, the electric motor current control section.

Abstract: The invention provides, as an aspect thereof, an document reading apparatus that includes: a speed calculating unit that calculates a speed related to the rotation of a motor on the basis of a signal that is outputted from an encoder; and a controlling unit that calculates control amount on the basis of the speed calculated by the speed calculating unit so as to control the rotation of the motor in accordance with the calculated control amount. In the configuration of an document reading apparatus according to this aspect of the invention, the above-mentioned controlling unit controls the motor with an increase in the control amount in a case where there occurs no change in the signal that is outputted from the encoder for a certain period of time. The increase in the control amount is based on the length of time that has elapsed since the last change in the signal.

Abstract: A control system having an integrator component that provides an integrator output signal used to control a load, and a method controlling the same includes conditioning the integrator component during a fraction of the period in which it would tend to otherwise wind-up.

Abstract: A motor controller includes: a notch filter arranged inside a control system; an oscillation frequency estimating section which estimates an oscillation frequency component in a motor; and a notch control section which controls a notch filter so as to change a notch frequency and a notch width. The notch control section changes a frequency between an oscillation frequency and a notch frequency set in a notch filter as a new notch frequency, while changing a notch width to a new notch width such that the notch width is larger after the change than before the change.

Abstract: A controller employed in conjunction with a synchronous generator monitors the output voltage of the generator. The controller employs the monitored output voltage as feedback that is used to control the excitation provided to an exciter field winding. In addition, the controller applies a control loop to the monitored output voltage that detects and modifies voltage ripple signals within the monitored output voltage to generate a compensated signal that is used to control the excitation to the exciter field winding. In particular, by detecting and modifying voltage ripple signals within the monitored output voltage, the controller is able to counteract armature reaction voltage ripples caused by unbalanced short-circuit faults, thereby preventing the build-up of voltage on the DC link.

Abstract: A compensation of cyclical interferences occurring during operation of motor controlled by an electrical motor drive comprising the controllable motor and a speed governor, wherein a position determiner is provided for continuously determining a position of said motor, responsive to a position signal indicative of said position of said motor and wherein a load observer responsive to a first output signal received from said position determiner and to a second output signal received from the speed governor is provided for generating a load signal indicative of an estimated load and continuously applying said load signal to an output of the speed governor.

Abstract: Systems and methods that determine resonant frequencies of a motor system via employing an output of a velocity regulator. The velocity regulator enables the motor drive to command the rotation of the motor at predetermined rotations, by setting rotational speeds of the motor. The output of the velocity regulator can then be stored as a function of time, and a Fast Fourier Transform performed on such time data to obtain a frequency data and a signal power spectrum.

Abstract: In electric vehicle control, system voltage stabilization control is executed to reduce the difference between a target value and detected value of a system voltage generated by a voltage boosting converter for an AC motor. Further, conversion power control is executed to reduce the difference between a command value and detected value of the conversion power, which is defined as the output power of the voltage boosting converter. A conversion power correction quantity is computed from an input power operation quantity of the system voltage stabilization control and reflected in the conversion power control to correct the conversion power. Thus, variations in a system voltage caused by an error or the conversion power control can be reduced.

Abstract: A relatively small, lightweight actuator includes a plurality of motors, an actuation element, a translation member, and a plurality of position sensors. The motors each supply a drive force to the actuation member, causing it to rotate. The translation member is configured, upon rotation of the actuator, to translate to a position. The position sensors sense the translational position of the translation member and the rotational position of each motor. The actuator is relatively small, lightweight, and can withstand the relatively severe environmental conditions and relatively significant levels of vibration and shock associated with many aerospace applications.

Abstract: An apparatus includes a multi-phase inverter, a fault detector to indicate a detection of a fault, a sensor to provide a speed signal indicative of whether a speed of a PM motor is greater than a transition speed, and a controller. The controller is operable to apply either an open-circuit response or a short-circuit response to the multi-phase inverter. The open-circuit response is applied when the speed of the PM motor is greater than the transition speed and a fault is detected. The short-circuit response is applied when the speed of the PM motor is less than the transition speed and the fault is detected. The transition speed is either a fixed predetermined speed or an adjusted predetermined speed.

Abstract: There is provided a control unit capable of rapid and precise stoppage of an object to be driven by a motor for use in a printer. The control unit has a speed control part to control the object by acceleration control, constant speed control, deceleration control, and stoppage control by controlling a current to be applied to the motor, and also an inertia calculating part to calculate inertia of the object based on angular acceleration of the motor under the acceleration control of the object, and current values to be applied to the motor under the acceleration control and the constant speed control of the object. The speed control part uses the calculated inertia for controlling the current to be applied to the motor.

Abstract: Methods and devices for brushless DC motor operation. An example method may include using previously sensed Hall effect sensor transitions to predict a future Hall effect transition, and dividing a time between a most recent Hall effect sensor transition and the predicted Hall effect sensor transition into time increments. The time increments may be used to effect phase advance by selecting a number of time increments to create a time offset for phase advance purposes. The time increments may also be used as a virtual encoder. Devices incorporating controllers and control circuitry for performing like methods are also discussed.

Abstract: In an automatic transmission position control by a motor, it is determined whether the present instant belongs to a starting period, that is, the present instant is immediately after resetting of a control unit or application of power to it. If it is the starting period, an actual shift position that is detected from an output of an output shaft sensor for detecting a rotation position of a motor is set as an instructed shift position. With this measure, even if the control unit is reset for a certain reason while the vehicle is running, the instructed shift position is not changed in association with the resetting. This prevents trouble that the shift position is switched contrary to the intention of the driver, whereby the reliability of a position switching control can be increased.

Abstract: A motor controller system uses a rotary sensor with a plurality of signal conditioning units, coupled to the rotary sensor. Each of these units, which is associated with a particular range of motor output shaft rotation rates, generate a feedback signal indicative of the position of the motor's output shaft. A controller (i) converts a selected motor output shaft rotation rate to a corresponding incremental amount of rotational movement for a selected fixed time period, (ii) selects, at periodic completions of the selected fixed time period, the feedback signal from one of the signal conditioning units for which the particular range of motor output shaft rotation rates associated therewith encompasses the selected motor output shaft rotation rate, and (iii) generates a motor drive signal based on a difference between the incremental amount of rotational movement and the feedback signal from the selected one of the signal conditioning units.

Abstract: A method that provides increased flexibility to measure dynamic range of a rotating system is provided. The method includes the steps of: providing a first rotating member; providing a second rotating member suitably engaged to the first rotating member; providing a set of sensors disposed to sense variations in characteristics along a circumference of the first member and the second member respectively; providing a controller for receiving information sensed by the sensors; determining a rate of rotation of the rotating members; selectively using the sensed information thereby at different rate of rotation different amount of the sensed information is used.

Abstract: There is provided a control unit capable of rapid and precise stoppage of an object to be driven by a motor for use in a printer. The control unit has a speed control part to control the object by acceleration control, constant speed control, deceleration control, and stoppage control by controlling a current to be applied to the motor, and also an inertia calculating part to calculate inertia of the object based on angular acceleration of the motor under the acceleration control of the object, and current values to be applied to the motor under the acceleration control and the constant speed control of the object. The speed control part uses the calculated inertia for controlling the current to be applied to the motor.

Abstract: In one embodiment, a method and machine are provided for tuning compensation parameters in a motion control system associated with a mechanical member. The method includes the steps of receiving an indication of a compensation parameter to be tested, based on the compensation parameter to be tested causing a signal associated with a desired motion of the mechanical member to be commanded, acquiring control data associated with the signal, acquiring measurement data associated with actual motion of the mechanical member in response to the signal, analyzing the control and measurement data; and based on the step of analyzing the control and measurement data, implementing a value of the compensation parameter.

Abstract: An oscillation isolator for supporting an oscillation isolation platform on a pedestal includes an active oscillation isolator having a displacement generating type actuator to reduce oscillation of the platform and a displacement adjuster provided between the active oscillation isolator and the platform or the pedestal for adjusting relative displacement between the active oscillation isolator and the platform or the pedestal. The displacement adjuster has a rigidity higher than that of the active oscillation isolator and is dynamically located in series between the active oscillation isolator and the platform or the pedestal.

Abstract: An electric motor that may be used in a remote location, such as in a wellbore for pumping production fluids. The electric motor is designed to permit real-time adjustment of the position feedback signals to optimize motor performance. A position sensor is coupled to the rotor to sense rotor position. Simultaneously, a parameter, such as shaft twist, is measured, and a feedback control signal is provided. A processor receives the position sensor signals and the feedback control signals, and adjusts the energization of the stator windings to optimize motor performance.

Abstract: A system for electronic control of an actuator of an automatic control system in a motor vehicle, has a control unit with at least one control function unit for controlling the actuator as a function of at least one operating parameter at a defined adjusting speed. The control unit has an adjusting rate limiting device assigned to at least one control function unit, for limiting the desired adjusting speed for controlling the actuator defined by the control function unit, to a defined limit value.

Abstract: A method and apparatus for tuning control loop parameters in a motion control system, is provided. In one embodiment, tuning of the proportional and integral gains of a servocontroller's velocity loop compensator is provided, as well as tuning of the cutoff frequencies of the servocontroller's low pass filters. In this embodiment, random noise excitation is added to the velocity command during a plurality of movement types for a machine tool axis. During each movement type, frequency response measurements are taken. Then, a composite frequency response can be selected by concatenating portions of the various frequency response measurements, so as to simulate a worst case scenario for the machine tool axis. From this composite response, an open loop response can be calculated and displayed, as well as bandwidth, phase margin, and gain margin values. The user can then enter the compensator parameters which were used when this data was taken, as well as proposed parameters.

Abstract: A control system (10) for a door operator (12) for moving a door includes a position sensor (54) to be coupled to the door (28) for sensing the position of the door and generating a position signal. An acceleration sensor (48) is to be coupled to the door for sensing the acceleration of the door (28) and generating an acceleration signal. An integrator (50) integrates the acceleration signal to generate a first velocity signal. A differentiator (56) differentiates the position signal to generate a second velocity signal. A blending filter (42) blends the first and second velocity signal to generate a filtered velocity signal, and a controller (32) regulates the velocity of the door (28) in response to the time and position of the door in a door open or close operation.

Abstract: A control system stabilizes the flexible body bending modes of a space, airborne, or ground-based system, while providing angular position control of an oscillating mass connected to a counter-oscillating counterbalance. The actuating mechanism uses two drive motors to exert torques on the mass and counterbalance, respectively, under the control of a feedback controller. The controller has a first control channel generating a first torque command signal for the first drive based on the angular position of the mass, and a second control channel generating a second torque command signal for the second drive based on the angular position of the counterbalance and a torque cross-feed signal from the first control channel. The second control channel includes a notch filter for removing input frequencies in a predetermined bandwidth about the frequency of the first torque command signal.

Abstract: A control constant identification system which comprises a command generation section for generating a speed command Vref, a speed control section for determining a torque command Tref by the speed command Vref and actual motor speed Vfb and controlling motor speed, an estimation section for simulating the speed control section according to a model and outputting an estimated torque command Tref', and an identification section for identifying inertia J according to a ratio between a value STref resulting from time integration of the torque command Tref output by the speed control section at a predetermined interval [a, b] and a value STref' resulting from time integration of the torque command Tref' output by the estimation section at the predetermined interval [a, b].

Abstract: A driving circuit for generating a motor driving voltage has a positive feedback loop for feeding back the motor driving voltage through a filter. The filter is arranged so as to have a transfer function given as G.sub.F (s) which (1) satisfies G.sub.F (s).apprxeq.1 in a frequency band in which disturbances should be suppressed while (2) satisfies .vertline.G.sub.F (s).vertline.<.vertline.G.sub.open .vertline. in a full range of frequencies, where G.sub.open represents an open loop transfer function of a motor control device in which a positive feedback loop is not provided. With this arrangement, it is possible to suppress disturbances, irrelevant to motor characteristics which may vary. Besides, it is possible to provide a motor control device in which computations for disturbance compensation are considerably decreased.

Abstract: A brushless AC servo motor control and modified motor to minimize the rotational acceleration and deceleration of a semiconductor wafer during processing steps where fluid is applied in a thin coating on the wafer. The control utilizes sine and cosine encoder outputs of single cycle and multiple cycle per revolution to calculate motor shaft position by an inverse tangent calculation of sine and cosine ratios. Resolution of motor shaft position is greatly improved as is rotational velocity control. In response to a prediction of desired shaft position in comparison with actual position the three field currents are adjusted to change the torque applied to the rotor and shaft. In the semiconductor wafer manufacturing application the motor shaft is modified to permit vacuum attachment of the wafer to the disc that rotates with the shaft.

Abstract: A sensorless control for operating an inverter coupled to a switched reluctance machine includes an instantaneous position generation circuit that develops a signal for controlling commutation of the switched reluctance machine. The instantaneous position generation circuit includes a digitally controlled counter which provides a direct interface between a position estimation circuit and commutation logic for the inverter.

Abstract: Methods and systems consistent with the invention generate a motion profile of a motor. A reference acceleration profile, a reference velocity profile, and a reference displacement profile are first defined. Displacement-velocity data defining displacement data with respect to velocity data is then stored in a memory. A plurality of conversion constants which include a maximum velocity ratio K1, a maximum acceleration ratio K2, and a displacement conversion constant K3, are calculated, are then calculated using following equations: ##EQU1## where A.sub.max represents a maximum acceleration value in the reference acceleration profile, V.sub.max represents a maximum velocity value in the reference velocity profile, a.sub.max represents a maximum acceleration value in the generated profile, and V.sub.max represents a maximum velocity data in the profile to be generated. The system then determines a position data of the motor and maps the position data into a reference displacement data.

Abstract: An improved servo control device and method for a VCR that minimizes jitter caused in a reproducing mode of the VCR (reproducing VCR) when it reproduces a video signal recorded by another VCR (recording VCR). A recording characteristic of the recording VCR (such as a duty interval of horizontal synchronous signals contained in the video signal) is used along with one or more reproducing characteristics (such as speed and phase) of the reproducing VCR to control a rotation speed of the reproducing VCR's drum motor.

Abstract: The present invention provides an air bearing type machine tool capable of carrying out a process with a high load for cutting iron or the like and controlling the degree air is used. The air bearing type machine tool includes a main shaft, an air bearing supporting the main shaft, and an air pressure regulating device capable of regulating the pressure of air supplied to the air bearing. The air pressure regulating device, in turn, has an air feed portion supplying air to the air bearing, a processing load detection device for detecting the degree of processing load, a processing power detection device for detecting the degree of processing power, and an air pressure defining device for controlling the pressure of air fed from the air feed portion by using the detected values of the processing load and the processing power.

Abstract: The present invention provides a method for detecting the position, direction of rotation and rotational speed of a rotatably seated part, which are employed, for example, in particular in externally-operated locking parts of motor vehicles (e.g., with an electric window opener with protection against jamming). The method allows a reduction in the number of components and installation space. The method of the present invention has the feature that control commands and the state of the motor are provided to a logical evaluation device. Either the high and low edges of the digitized signal, or one of the high or low edges, together with the signal level at the time of motor start or reversal of the direction of rotation of the motor are assigned to the one or the other direction of movement (direction of rotation).

Abstract: In a displacement machine for compressible media having at least two rotors (14a-c) which are configured as profiled bodies and whose profiles engage with one another in the manner of gearwheels during rotation, the individual rotors are respectively driven by their own electric motors (9a-c) and are kept synchronous in rotational speed and angular position by electronic closed-loop and/or open-loop control units (1; 25a-c) in accordance with the transmission ratio of the displacer unit stage. The electronics can be employed for monitoring further operating data of the pump and also for matching the pump output by changing rotational speed. It can also be used as an overload protection. The rotational speeds and rotational attitudes of the rotors are controlled individually and independently of one another, the required attitude values being specified to the individual control units (25a-c) by means of a main control unit (1).

Abstract: A method for estimating rotor shaft velocity includes adding two counter rotating signal components to a fundamental motor control signal to provide a combined control signal; sensing at least one motor phase signal; determining an extracted portion of the motor phase signal representative of the two counter rotating signal components; and using the extracted portion to estimate rotor shaft velocity. The step of adding two counter rotating signal components may include either adding a single phase signal in a reference frame synchronous to the fundamental motor control signal or adding two separate signals.

Abstract: A method for controlling a servo system (10) having friction, in which the non-linear characteristic (20) of the position controller (12) is defined such that the magnitude of the variable Ns, Vs supplied to the servo system (10) having friction in the case of a control deviation .DELTA.x lying outside a predeterminable target region (21) produces a torque or a force which is adequate to tear the servo system free of the stiction torque or stiction and such that the movement energy of the servo system (10) can be dissipated in the target region (21). The additional use of an integral component, which is preferably a function of the control deviation .DELTA.x, increases the steady state accuracy.

Abstract: A method and apparatus for tuning an external velocity loop servo drive of the type including a controller, a command device, an external velocity servo amplifier, an actuator and a position feedback device. The tuning technique include the use of three unidirectional motion events of descending duration. In the first motion event the controller applies a control signal of known amplitude to the actuator and monitors the actuator velocity based upon the position feedback signals. The controller determines the actuator steady state velocity during the motion event and uses this value to determine a scaling factor for the servo amplifier. In a second motion event, the controller drives the actuator in acceleration and deceleration in response to a control signal of known amplitude. Based upon the times at which the actuator reaches certain anticipated velocities, the controller determines system dynamic characteristics.

Abstract: An apparatus includes a multi-phase inverter, a fault detector to indicate a detection of a fault, a sensor to provide a speed signal indicative of whether a speed of a PM motor is greater than a transition speed, and a controller. The controller is operable to apply either an open-circuit response or a short-circuit response to the multi-phase inverter. The open-circuit response is applied when the speed of the PM motor is greater less than the transition speed and a fault is detected. The short-circuit response is applied when the speed of the PM motor is less greater than the transition speed and the fault is detected. The transition speed is either a fixed predetermined speed or an adjusted predetermined speed.

Abstract: A displacement sensing method of the present invention includes the steps of superimposing a predetermined signal on a torque command to supply a drive torque to a motor, measuring an amplitude spectrum ratio between the drive torque in superimposing the predetermined signal on the torque command and a motor angle measured by a displacement sensor, generating correction data for evening out the amplitude spectrum ratio, and correcting the measured motor angle so that the motor angle measured by the displacement sensor is equal to an actual motor angle using the correction data.