There is provided a light control circuit including a light detector, a frequency detector, an error amplifier, an NMOS driver and a light source. The frequency detector identifies a signal frequency according to detected voltage signals outputted by the light detector and generates a control signal accordingly. The NMOS driver changes a drive current of the light source according to an output of the error amplifier. The error amplifier changes a bandwidth thereof according to the control signal from the frequency detector to regulate a response time of the drive current of the light source.

A rotation angle detection device includes a current meter that measures a current flowing in a direct current motor; a filter that extracts a ripple component from the current; a ripple detector that detects a ripple from a signal that has passed through the filter; and a rotation angle detector that detects a rotation angle of the direct current motor based on the number of ripples. The rotation angle detector measures an observation period based on consecutive ripples, calculates an estimation period between the consecutive ripples based on the observation period, determines whether the observation period is within a normal range based on the estimation period and the observation period, and in response to determining that the observation period is within the normal range and an immediately-previous observation period is outside the normal range, calculates a number of correction ripples CRN so as to correct the number of the ripples.

An angle sensor includes a plurality of magnetic sensors and a processor. The plurality of magnetic sensors generate a plurality of detection values representing directions of a composite magnetic field, which is a composite of a magnetic field to be detected and a noise magnetic field. The processor assumes a group of estimated unknowns. The group of estimated unknowns is a set of estimated values of a first, a second, and a third unknown. The first unknown corresponds to an angle detection value. The second unknown corresponds to the direction of the noise magnetic field. The third unknown corresponds to the strength of the noise magnetic field. The processor executes a process for determining the group of estimated unknowns a plurality of times, and assumes an estimated value of the first unknown in the last determined group of estimated unknowns as the angle detection value.

A motor drive device enabling efficient position control at a low cost is provided. The motor drive device includes a position detection unit configured to detect a current position of an object to be driven by a motor and a motor control unit configured to calculate an output control amount for the motor based on a deviation between the current position and a target position of the object to be driven by the motor while changing an advance angle in a rotational phase of the motor according to the output control amount when the advance angle is within a predetermined advance angle range in the rotational phase of the motor and changing a drive voltage of the motor with the advance angle fixed when the advance angle is outside the predetermined advance angle range.

An electronic device includes a motor, a moving body on which a processing part is mounted, a rotary encoder, a memory; and a controller. The controller is configured to execute a detection process of detecting a position of the moving body based on an encoder signal, a control process including a first control of controlling movement of the moving body by controlling the motor and a second control of controlling a processing operation by the processing part in a constant speed movement section of the moving body, a determination process of determining a detection error of the position of the moving body generated in an acceleration section of the moving body based on information stored in the memory, and a correction process of correcting at least one of the first control and the second control.

An apparatus and a method for detecting a phase delay of a resolver are provided. The apparatus includes a resolver configured to output a signal corresponding to a rotation angle of a motor, an excitation signal generator configured to generate an excitation signal using a square wave signal, and a controller configured to differentiate the signal to obtain a differential signal, detect a time when the differential signal meets a reference voltage as a peak time of the signal, and detect a phase delay time of the signal based on the peak time of the signal and an edge time of the square wave signal.

There is provided an optical encoder including a phase shifter circuit, two multiplexers, two digital circuits and four comparators. The phase shifter circuit receives signals from an amplifier and outputs multiple phase shifted signals. Each of the two multiplexers receives a half of the multiple phase shifted signals and outputs two pairs of phase shifted signals, each pair having 180 degrees phase difference, respectively to two comparators connected thereto. Each of the two digital circuits controls the corresponding multiplexer to select the two pairs of phase shifted signals from the half of the multiple phase shifted signals.

A method for calibrating a position measurement system includes receiving measurement data from the position measurement system and determining that the measurement data includes periodic distortion data. The position measurement system includes a nonius track and a master track. The method also includes modifying the measurement data by decomposing the periodic distortion data into periodic components and removing the periodic components from the measurement data.

The present invention provides a method for detecting a positional change amount due to a movement of a moving body by reading, with a sensor, a plurality of gradations disposed along the direction of the movement. The method includes: a step for taking, as one period, one gradation among the plurality of gradations and acquiring a pseudo sinusoidal signal in response to the positional change amount; a step for executing a Fourier transform on the pseudo sinusoidal signal within the range of at least one gradation, and calculating, from the spectral intensity of each frequency component obtained by the Fourier transform, the signal intensity of a fundamental wave component and the signal intensity of at least one harmonic component; a step for calculating a gain corresponding to each of the at least one harmonic component by dividing each signal intensity of the at least one harmonic component by the signal intensity of the fundamental wave component; and a step for detecting the positional change amount by subtracting, from the pseudo sinusoidal signal, each harmonic component multiplied by a corresponding gain.

A rotation sensing apparatus includes a detected part including a first pattern portion with a plurality of first patterns and a second pattern portion with a plurality of second patterns; a first sensor disposed opposite to the first pattern portion; a second sensor disposed opposite to the second pattern portion; a third sensor disposed at an angle from the first sensor and disposed opposite to the first pattern portion; a fourth sensor disposed at an angle from the second sensor and disposed opposite to the second pattern portion; and a rotation information calculation circuit to calculate rotation information regarding rotation of a rotating body based on first, second, third, and fourth oscillation signals associated with outputs of the first, second, third, and fourth sensors and to compensate for nonlinearity of a differential signal generated based on the first, second, third, and fourth oscillation signals.