Abstract: A resolver the resolver comprising an excitation coil for receiving an excitation signal formed by amplitude modulation of a high-frequency signal and a detection coil for outputting a detection signal. The resolver is arranged to detect a change in position of a rotor provided with the excitation coil or the detection coil based on the detection signal varying with the change in position of the rotor. The high-frequency signal is a digitized signal generated from a reference clock.

Abstract: Methods and systems are provided for aligning a resolver in an electric motor system. The method includes commanding a d-axis current command and a speed command, operating an electric motor without a load in response to the d-axis current command and the speed command, determining a rotor speed in response to the speed command, and determining an offset of the resolver based on the speed command and the rotor speed when the rotor speed has substantially stabilized.

Abstract: A deflection amount Ps representing a difference between a position detection value Pl of a driven body and a position detection value Pm of a motor is detected. A position calculator proportional constant Kp, a time constant Tp of a first-order lag circuit that inputs a the deflection amount Ps, and a time constant Tv of a first-order lag circuit that inputs a difference between a speed detection value Vl of the driven body and a speed detection value Vm of the motor are changed based on the deflection amount Ps.

Abstract: In accordance with an embodiment of the present invention, a resolver system has at least one resolver and at least one amplifier in electrical communication with each resolver. A reference circuit is in electrical communication with the amplifiers. The reference circuit provides reference signals to the amplifiers. A non-linearity calibration and compensation circuit in communication with each amplifier uses the amplified reference signals to provide scale factors, so as to enhance a precision of the resolver system.

Abstract: A motor controller includes a reference signal generator; an A/D converter performing A/D conversion of the cosine and the sine signals outputted from a resolver; a first amplitude calculator calculating cosine and sine signal amplitudes based on twice-A/D converted cosine and sine signals respectively; a second amplitude calculator calculating averages of the cosine and the sine signals, and that calculates the amplitude of the cosine signal from a difference between the cosine signal average and a latest A/D converted cosine signal, and that calculates the amplitude of the sine signal from a difference between the sine signal average and a latest A/D converted sine signal; a synthesizer synthesizing the cosine and sine signal amplitudes obtained by the first and the second amplitude calculators respectively; a rotational angle calculator calculating a rotational angle based on the synthesized cosine and sine signal amplitudes; and a PWM controller.

Abstract: The invention provides an angular position detector that can be configured at low cost and that accurately detects the angular position of a rotor in a rotary electric device and permits reliable control thereof even when the rotary electric device runs at a high speed. The angular position detector includes a resolver that outputs a signal indicating the rotational angle of the rotor and a signal processing circuit that calculates the rotational angle of the rotor based on the signal output from the resolver. The signal processing circuit samples output signals from the resolver at predetermined intervals and converts the signal into a digital signal. By calculating the angular speed according to the digital signal output from the resolver, the computation process is simpler, and can be performed using a microcomputer with less processing power, which reduces the component costs for the angular position detector.

Abstract: A method of arranging a resolver comprises the steps of: a, setting stator magnetic poles number of the resolver Ns as a number being in integral multiples (t) of a phase number q; b, figuring out rotor magnetic pole number Nr based on a formula; c, arranging the stator and the rotor based on the stator magnetic poles number of the resolver Ns and the rotor magnetic pole number Nr, and producing signals with phase differences.

Abstract: A method of designing a reluctance resolver, and the resolver comprises a stator and a rotor, and an exciting coil and two sets of outputting wires wind around the tooth portion of the stator. The designing method comprises the following steps: fixing relative position; calculating the turn ratio of the stator; winding the coil of the stator; and designing the resolver. And the resultant resolver can improve the precision of calculating the position of the motor rotor.

Abstract: Apparatus and methods are provided for diagnosing faults in multiple, associated motor-resolver systems. One apparatus includes a swapping circuit coupling a first resolver to a first or second decoder, and a swapping circuit coupling a second resolver to the first or second decoder. One method includes applying a signal from a resolver to a first decoder to determine that the first decoder is malfunctioning if the first decoder continues to generate a fault signal, and applying a signal from a different resolver to a second decoder to determine that a motor associated with the first decoder is malfunctioning if the second decoder generates a fault signal. Another method includes transmitting a signal from a resolver to first and second decoders, transmitting a signal from a different resolver to the first and second decoders, and determining if the first decoder, second decoder, a first motor, or a second motor is malfunctioning.

Abstract: An apparatus, system, and method are provided for simulating outputs of a resolver. One apparatus includes an adjustable sine waveform generator for simulating first and second sine wave signals, and an adjustable cosine waveform generator for simulating first and cosine wave signals. The apparatus also includes an adjustable waveform generator and an adjustable gain circuit coupled to the sine waveform generator and cosine waveform generator. The system includes a device simulating a resolver coupled to a motor controller. The device includes an adjustable sine waveform generator and an adjustable cosine waveform generator coupled to an adjustable waveform generator and an adjustable gain circuit. One method includes transmitting a signal simulating at least one resolver fault condition to a motor controller to determine if the motor controller detects the fault condition(s).

Abstract: A control system and method to determine position of a rotor relative to a stator for a synchronous multipole electrical machine is presented, including one for application on a fuel/electric hybrid powertrain for a vehicle. The machine includes a stator, a rotor, and a rotor position sensing mechanism. The control system controls the electrical machine, in conjunction with an electrical storage device and an inverter, using algorithms and calibrations which derive a rotor position based upon a sensorless position sensing technique, and determine an offset from a sensed rotor position. Electrical output from the inverter to the machine is controlled based the offset, which is stored non-volatile memory. A rotor position is derived based upon a sensorless position sensing technique during initial machine operation after startup of the machine, and includes operation in a torque-generative mode and in an electrical energy-generative mode.

Abstract: Methods and systems are provided for aligning a resolver in an electric motor system. The method includes commanding a d-axis current command and a speed command, operating an electric motor without a load in response to the d-axis current command and the speed command, determining a rotor speed in response to the speed command, and determining an offset of the resolver based on the speed command and the rotor speed when the rotor speed has substantially stabilized.

Abstract: A reference position detecting apparatus includes an electric motor and a motor control unit. The electric motor includes a plurality of first coils and a plurality of second coils. The electric motor further includes a rotor that rotates when at least one of the plurality of first coils and the plurality of second coils is supplied with electricity. The motor control unit controls electricity supplied to either one of the plurality of first coils and the plurality of second coils to rotate the rotor to a limit position in a movable range of an object.

Abstract: A motor control apparatus for controlling a motor based on an output from a sensor includes a storage unit storing a value according to an excitation power supply to excite the sensor, a PWM output unit outputting a PWM output signal having a pulse width modulated to have a duty ratio corresponding to a value stored to the storage unit, and a filter input with the PWM output signal from the PWM output unit. The sensor is supplied with the excitation power supply based on an output from the filter.

Abstract: This invention provides methods for electric vehicle motor control and rotor position detection and fault-tolerant processing. The rotor position signal sampled by the system is compared with the previous rotor position ?0. When there is a sudden change, the current position signal acquired is discarded. Instead, a fault-tolerant processing strategy for use during an error condition is employed where the previous sampled rotor position ?0 is used as a base to determine the corrected current rotor position angle ?1?. Then the correcting value is used to control the electric motor.

Abstract: In accordance with an embodiment of the present invention, a resolver system has at least one resolver and at least one amplifier in electrical communication with each resolver. A reference circuit is in electrical communication with the amplifiers. The reference circuit provides reference signals to the amplifiers. A non-linearity calibration and compensation circuit in communication with each amplifier uses the amplified reference signals to provide scale factors, so as to enhance a precision of the resolver system.

Abstract: The rotation angle detection apparatus for detecting a rotation angle of a rotating body on the basis of a resolver signal outputted from a resolver mounted on the rotating body includes a first function of detecting a specific phase timing of the resolver signal, a second function of measuring a time needed for the resolver signal to reach from the specific phase timing to a peak thereof, a third function of generating a sampling timing in accordance with the time measured by the second function, a fourth function of sample-holding the resolver signal at the sampling timing to hold a peak value of the resolver signal, and a fifth function of computing the rotation angle of the rotating body on the basis of the peak value of the resolver signal held by the fourth function.

Abstract: A system for controlling an electric motor includes a controller and a position indicator that provides position information regarding at least one motor component to the controller. The controller utilizes phase relationships indicative of the position information to determine the actual position of the component of interest. The phase information in one example is derived from the output of a resolver that provides two output signals corresponding to sin (?) and cos (?), where ? is the angular position. Utilizing the phase relationship simplifies the task of determining accurate position information that is useful to modify motor control signals to compensate for latency when making position determinations, velocity calculations or both. The inventive system makes it possible to use less expensive electronics to arrive at more reliable results.

Abstract: This invention provides a motor control apparatus and vehicle steering apparatus capable of determining whether the motor control CPU is normal or abnormal with an inexpensive structure.

Abstract: Control over velocity of a model train may be determined based upon the speed of rotation of a control knob. A processor receives electronic pulses indicating rotation of the knob beyond a predetermined increment of angular distance. The processor calculates the amount of power ultimately conveyed to the model train based not only upon the number of pulses received, but also upon the elapsed time between these pulses. The shorter the elapsed time between pulses, the greater the change in power communicated to the train. Initially, a user can rapidly rotate the knob to attain coarse control over a wide range of velocities, and then rotate the knob more slowly to achieve fine-grained control over the coarse velocity. Utilizing the control scheme in accordance with embodiments of the present invention, in a compact and uninterrupted physical motion, a user can rapidly exercise both coarse and fine control over velocity of a model train.

Abstract: The rotor position of a synchronous motor is determined, in that for a plurality of current vectors distributed over one electrical rotation of the synchronous motor, the amount of the current vector which is necessary to attain a defined deflection of the rotor is determined. The position of the rotor may be calculated from the position of the minima of the amounts thus determined, taking into account the direction of rotation of the rotor. The engagement of a brake may ensure that grooving forces and machine vibrations play no role for the method to determine the rotor position.

Abstract: An apparatus for processing a signal output by an encoder, including a frequency multiplication unit to repeatedly multiply each of frequencies of two sinusoidal signals with a phase difference of approximately 90 degrees by a predetermined number a predetermined number of times; a converter to convert each pair of the two frequency-multiplied sinusoidal signals into square wave signals; and a processor to receive the square wave signals and count a number of rising and/or falling edges of the square wave signals in order to determine and control a position of an object to be controlled.

Abstract: A linking interlock mechanism in a biped robot is provided that prevents the reduction gears in the servo device from being damaged due to an external impulsive force. A servo horn is fit to the output shaft protruded from a servo device housing, which includes a motor, reduction gears, and the like. An interlock member for transmitting force externally is press fitted on the junction surface of the servo horn with the locking screw inserted via the washer. Salient portions are formed on the junction surface between the servo horn and the interlock member. The interlock member has depressed portions at the positions engaged with the salient portions. When a strong impulse force is externally added to the interlock member, the linking state between the interlock member and the servo horn is released instantaneously. This can prevent the reduction gears in the servo device from being damaged.

Abstract: A resolver unit having a structure in which the axial length is shortened to prevent the magnetic coupling characteristic between the rotary and stationary sides from being impaired, a winding generates more magnetic fluxes, and multiplexing is easily conducted, and also a resolver using such a resolver unit are provided.

Abstract: A servo driver (3) includes: an input section (11) for input-specifying the type of an encoder (7) at the side of an actuator (2); a control section (13) for generating a control signal (12) according to the type input; and an encoder signal processing IC (20) for switching the input port to which reception data (7S) is input form the encoder (7) according to the control signal (12). The encoder signal processing IC (20) is compatible with processing of an output of either a line-saving encoder or a 14-line encoder and can realize a highly general-purpose servo driver. This can solve the problem that the servo driver should be modified according to the type of the encoder mounted on the actuator.

Abstract: An apparatus and method for determining an angular position of a shaft are disclosed, which comprise resolving an excitation signal at an excitation frequency into at least two orthogonal signals, converting the orthogonal signals to a digital estimate, for each of the orthogonal signals, and evaluating an amplitude and a polarity of the orthogonal signals to determine the angular position. The process of converting the orthogonal signals comprises comparing the orthogonal signal to an analog feedback signal to generate a comparison result and incrementally adjusting the digital estimate in response to sampling the comparison result at an estimation frequency. The converting process also includes converting the digital estimate to the analog feedback signal, collecting a digital estimate history at a sample frequency that is a binary multiple of the excitation frequency, and analyzing the digital estimate history to determine the amplitude and the polarity substantially near the excitation frequency.

Abstract: A rotation angle detecting apparatus having a reference signal-generating device that generated a reference signal; a rotation angle detecting section that generated an output signal in response to the reference signal; a feedback control section that determines a rotational angular speed based on the output signal and performs feedback control to calculate a rotation angle; and a free-running range change device that narrows a free-running range of the rotational angular speed at a time of starting settling of the rotation angle. In the rotation angle detecting apparatus, the free-running range of the rotational angular speed at the time of starting the settling of the rotation angle is narrowed, whereby the settling time can be shortened. Accordingly, the time that elapses before it becomes possible to detect a rotation angle can be shortened correspondingly.

Abstract: A double variable reluctance resolver in which a redundancy is given to a variable reluctance resolver to improve reliability. The double variable reluctance resolver also functions as a multiple speed resolver system.

Abstract: A rotation angle sensor that outputs different axis combination angles as absolute position information by forming a range of salient poles that have different axis combination angles from each other on the rotor and the stator.

Abstract: A variable reluctance resolver has a rotor with magnetic poles with 2× or greater axis combination angles, and is structured so that reliable and accurate zero point detection can be carried out. Concave and convex portions are provided on at least two, but fewer than all, of the magnetic poles of the rotor, and the zero point detection winding is provided on a plurality of electrical poles of the stator. Two or more zero point detection signals are generated simultaneously by a plurality of zero point detection windings. Therefore, even if a portion of the zero point detection signals is lost, the zero point can still be identified based on the correlation between the two or more zero point detection signals.

Abstract: A control apparatus for a machine that can be operated at high precision in a stable control state is provided by driving a movable body with control parameters suited to the mechanical state. A control parameter calculation circuit is provided to obtain control parameters for a drive apparatus control circuit for driving actuators in accordance with the conditions of actuator rotational velocity, the orientation of the movable body, and the position of the movable body, and a control parameter K for the drive apparatus control circuit is varied.

Abstract: A deviation angle detector enlarges the application range by enlarging the detectable deviation angle range. The deviation angle detector has two resolvers, which have rotors, stators, and single excitation windings and multiple output windings that are coiled around the stators. The difference in rotation angles of the resolvers is detected as a deviation angle ?? by calculating the output signal that corresponds to the rotation angles of the resolvers digitally or in analog. The corresponding output windings of the resolvers are connected in series and the output signals are extracted from the serially connected output windings and calculated digitally or in analog.

Abstract: A method and apparatus to process an analog encoder signal. The apparatus includes an analog encoder pattern generating unit, an analog encoder pattern storage unit, a digital/analog converting unit, a comparing unit, a recent state latch unit, a present state determining unit, and a gray code converting unit. The method includes generating an analog encoder pattern by sampling and quantizing a quasi-sinusoidal wave signal output from an analog encoder during initialization; determining a recent state and a present estimated state by comparing the analog encoder pattern with the quasi-sinusoidal wave signal; and generating quadrature signals from the recent state and the present estimated state.

Abstract: A robot system capable of performing automatic updating of data inherent to a robot mechanism section or a mechanical unit thereof when changing the robot mechanism section or the mechanical unit. After changing the robot mechanism section or the mechanical unit, data of identifiers are read by a robot control section from nonvolatile memories associated with encoders in the robot mechanism section or the mechanical unit automatically upon turning-on of a power supply on or a manual operation. If it is determined that a kind of the robot is changed, the data indicating the kind of robot is rewritten in the robot control section. If it is required to change an algorithm for forward/inverse transformation for calculation of a robot locus, the algorithm is changed. If a kind of the robot is not changed, it is determined whether individuality of the whole robot mechanism section or the mechanical unit is changed or not.

Abstract: A control device measures time intervals T1 to T12 from the reference time until when each of the rotational angles ?bn1, ?bn2 output from each of resolvers becomes n×60 degrees (n=1 to 12, i.e., 60 degrees to 720 degrees). Then, the control device calculates a deviation angle ??n at each of the rotational angles at the intervals of 60 degrees by calculating T1/T12 to T11/T12 using the measured T1 to T12. By substituting the calculated deviation angle ??n into an equation, n×60°+??n (n=1 to 11), the control device corrects the rotational angles at the intervals of 60 degrees. The control device generates each of drive signals DRV1, DRV2 using each of the corrected rotational angles, and outputs each of the drive signals DRV1, DRV2 to each of inverters. The inverters drive each of AC motors (M1, M2) based on each of the drive signals DRV1, DRV2.

Abstract: A Hard Disk Drive VCM positioning servo loop comprises an oversampling bitstream Digital to Analog converter. The oversampling DAC is a sigma-delta converter which yields higher resolution and lower noise than Nyquist-rate DACs. This allows driving the VCM with finer level of current control for higher track density. This approach can be implemented in the VCM driver chip (“combo chip”) or in the microprocessor device either in hardware or in software, reducing significantly the development and manufacturing cost. Furthermore this approach can be utilized in combination with a VCM actuation method known as “voltage mode drive” wherein the output of the sigma-delta converter represents the voltage to be applied directly to the VCM actuator. Furthermore this approach can be utilized for optical data storage motor positioning servo loops or any other motor positioning servo loops where high dynamic and resolution is needed.

Abstract: This invention provides an electrically-powered steering apparatus capable of assisting a steering torque appropriately using a resolver. A reference signal is applied to a resolver arithmetic processing I/F circuit 34 and a resolver arithmetic processing I/F circuit 36 through a reference signal input means 38 and a microcomputer 30 obtains a differential in amplification factor from outputs of the resolver arithmetic processing I/F circuit 34 and the resolver arithmetic processing I/F circuit 36 when the reference signal is supplied. A correction value for computing a position from the outputs of the resolver arithmetic processing I/F circuit 34 and the resolver arithmetic processing I/F circuit 36 is computed from the obtained differential.

Abstract: A variable reluctance resolver is provided with an output winding having a reduced effect from externally introduced leakage magnetic flux. A variable reluctance resolver is provided with a resolver excitation winding and a resolver output winding wrapped around multiple stator magnetic poles which respectively output rotary angle X and Y components as a rotor turns. Windings are wound such that the polarities of output voltages on output windings wound around a row of three or more stator magnetic poles will be the same; all of the output windings are divided into an even number, two or greater, of groups, and output windings are serially connected in such a way that adjacent group output voltage polarities mutually differ.

Abstract: The detection of a pulse signal in an initialization pattern is ensured regardless of the position where a DC motor is stopped. A CPU detects the pulse signal generated by the pulse generator and an angle of rotation of a rotating shaft, and controls an angle of rotation of a rotating shaft based on the detected angle of rotation. The pulse generator generates the pulse signal in the initialization pattern, which indicates the position of origin of the angle of rotation, in accordance with the rotation of the DC motor. If a determination means determines that it is impossible to detect the pulse signal in the initialization pattern when the DC motor is rotated in a first direction, the CPU rotates the DC motor in a second direction.

Abstract: A multiplex resolver includes m resolver units disposed in tandem each comprising a rotor and a stator, where m is an integer not less than 2. The stator has a stator yoke, a plurality of stator magnetic poles projecting from the yoke, and excitation and output windings applied to the stator magnetic poles. The number of the stator magnetic poles corresponds to a shaft angle multiplier nX (n is an integer not less than 1) of the resolver. The rotor has n salient poles in accordance with the shaft angle multiplier nX. The respective stators of the resolver units are connected together such that the stator magnetic poles of the stator of one resolver unit do not overlap the stator magnetic poles of the stator of another resolver unit, as viewed in the axial direction.

Abstract: A region judging circuit judges an electric angle region of a three-phase brushless DC motor based on an output signal of a resolver. A latch timing output circuit determines an optimum latch timing. A driving direction judging circuit judges a rotational direction of the motor based on a comparison in largeness between a pair of phase currents. A latch circuit latches a judgement result of the driving direction judging circuit at the latch timing designated by the latch timing output circuit and retains the judgement result until the next latch timing comes.

Abstract: In a coaxial multiplex position detecting apparatus for a rotating machine, a stator includes stator pieces, each stator piece individually being split in a circumferential direction of the stator, an exciting current winding, and a detection winding, the exciting current winding and the detection winding being wound on the respective stator pieces, and a plurality of rotors are disposed on outside and inside positions of the stator in a radial direction of the stator, the respective rotors having convex and recess portions in accordance with the number of poles that the respective rotors have and having different numbers of poles according to the inside and outside positions of the rotors from each other, revolution positions of the respective rotors being determined according to an output signal of the detection winding of the stator.

Abstract: This resolver/digital converter has a resolver, a resolver/digital converting portion and an exciting signal generator. The exciting signal generated from the exciting signal generator is supplied to the resolver, and the resolver signals produced from the resolver are supplied to the resolver/digital converter. This resolver/digital converter further has a conversion trigger generator that generates a conversion trigger signal on the basis of the exciting signal generated from the exciting signal generator, an A/D converter that converts the resolver signals produced from the resolver to digital values in response to the conversion trigger signal generated from the conversion trigger generator, and computing means that detects the failure status on the basis of the digital values produced from the A/D converter.

Abstract: An output terminal is provided at the middle point of each of output windings 112X and 112Y of a resolver 10. A difference between a voltage V2X (V2Y), between one of the end terminals and the middle point of the output winding, and a voltage V1X (V1Y), between the other end terminal and the middle point of the output winding, is detected by a difference voltage detection circuit 101, and supplied to a logical summing circuit 126 via a rectifier circuit 124 and a comparator circuit 125. In accordance with an output from the logical summing circuit 126, a fault of the windings, such as short-circuiting or the like, can be detected even at a specific rotation angle of the rotor. Thus, a resolver in which a fault thereof can be easily detected, as well as a resolver fault detection circuit, can be provided.

Abstract: A motor for reducing torque ripple includes a shaft having a shaft axis, a rotor positioned about the shaft, a first magnet ring positioned on the rotor, the first magnet ring having magnets each occupying a magnet angle &dgr; on the rotor, and a second magnet ring positioned on the rotor, the second magnet ring having magnets each occupying a magnet angle &dgr; on the rotor, wherein the second magnet ring is shifted a non-zero number of degrees relative to the first magnet ring and wherein ends of each magnet within the second magnet ring are located at different angular positions than ends of each magnet within the first magnet ring relative to the shaft axis of the shaft. The magnet angle &dgr; is preferably an optimal magnet angle for minimizing cogging torque and line to line back emf harmonics.

Abstract: A current target angle stored in a target angle register is subtracted from the immediately preceding target angle stored in a register by a subtracting device. As a result, the length (amount) and direction between the immediately preceding target angle to the current angle are generated. With the generated length and direction, a model acceleration generating circuit generates model acceleration data. With a count value of a current velocity detecting counter and a velocity data sequence that is output from a model velocity generating circuit, velocity error data is generated. With a count value of a current position detecting counter and a position data sequence that is output from a model position generating circuit, position error data is generated. The model acceleration data, the velocity error data, and the position error data are added by an adding device. The added result is supplied to a driver. The driver outputs a current that drives a pan motor.

Abstract: Disclosed is an apparatus for measuring an absolute rotation angle and a method thereof. In particular, the apparatus is available for a measurement and servo system in which high precision is required in rotation drive and absolute rotation angle measurement.

Abstract: A region judging circuit judges an electric angle region of a three-phase brushless DC motor based on an output signal of a resolver. A latch timing output circuit determines an optimum latch timing. A driving direction judging circuit judges a rotational direction of the motor based on a comparison in largeness between a pair of phase currents. A latch circuit latches a judgement result of the driving direction judging circuit at the latch timing designated by the latch timing output circuit and retains the judgement result until the next latch timing comes.

Abstract: It is an object to perform a near rotating control of a rotary element. As a construction, disclosed is a rotating position control apparatus having a potentiometer constructed by a contact element rotating in accordance with the rotation of a rotary element and a resistive element on which the contact element slides, a control unit for driving the rotation of the rotary element to a plurality of rotating positions on the basis of an output of the potentiometer, and an insulator which is provided between both ends of the resistive element in the potentiometer and on which the contact element can slide, wherein the apparatus includes an A/D converting unit for A/D converting the output of the potentiometer and drives the rotation of the rotary element from the current rotating position to a target rotating position on the basis of a value obtained by A/D converting the output of the potentiometer through the A/D converting unit and a command code to instruct the rotating position of the rotary element.

Abstract: This invention provides an electrically-powered steering apparatus capable of assisting a steering torque appropriately using a resolver. A reference signal is applied to a resolver arithmetic processing I/F circuit 34 and a resolver arithmetic processing I/F circuit 36 through a reference signal input means 38 and a microcomputer 30 obtains a differential in amplification factor from outputs of the resolver arithmetic processing I/F circuit 34 and the resolver arithmetic processing I/F circuit 36 when the reference signal is supplied. A correction value for computing a position from the outputs of the resolver arithmetic processing I/F circuit 34 and the resolver arithmetic processing I/F circuit 36 is computed from the obtained differential.