Abstract: Three rotation sensors circumferentially arranged at 90 degree intervals in a disk code wheel attached to a motor's output shaft respectively output a signal corresponding the rotational speed of the wheel. An error component of one period (one-periodic component) or an error component of two period (two-periodic component) is generated per rotation when the code wheel is eccentric to the output shaft or is elliptically deformed, respectively. Control means averages the signals of the first and second sensors to obtain a first correction signal and subtracts the signal of the third sensor from the signal of the first sensor to obtain a second correction signal while removing the two-periodic component. The control means subtracts or adds the first correction signal relative to the second correction signal upon coinciding these signals in phase and amplitude to calculate a rotation measurement signal from which the periodic components are removed.

Abstract: Three rotation sensors circumferentially arranged at 90 degree intervals in a disk code wheel attached to a motor's output shaft respectively output a signal corresponding the rotational speed of the wheel. An error component of one period (one-periodic component) or an error component of two period (two-periodic component) is generated per rotation when the code wheel is eccentric to the output shaft or is elliptically deformed, respectively. Control means averages the signals of the first and second sensors to obtain a first correction signal and subtracts the signal of the third sensor from the signal of the first sensor to obtain a second correction signal while removing the two-periodic component. The control means subtracts or adds the first correction signal relative to the second correction signal upon coinciding these signals in phase and amplitude to calculate a rotation measurement signal from which the periodic components are removed.

Abstract: A circuit board includes rotation sensors, each of which outputs a signal that corresponds to a rotational speed of a sensor plate secured to an output shaft. Each rotation sensor includes two opposed arms, which are spaced from each other in a direction parallel to an axial direction of the output shaft and receives a portion of the sensor plate between the opposed arms. The circuit board has a through hole or recess, which penetrates through the circuit board in the axial direction of the output shaft to receive a tubular portion of a stator base and which is elongated in a direction perpendicular to the axial direction of the output shaft.

Abstract: A circuit board includes rotation sensors, each of which outputs a signal that corresponds to a rotational speed of a sensor plate secured to an output shaft. Each rotation sensor includes two opposed arms, which are spaced from each other in a direction parallel to an axial direction of the output shaft and receives a portion of the sensor plate between the opposed arms. The circuit board has a through hole or recess, which penetrates through the circuit board in the axial direction of the output shaft to receive a tubular portion of a stator base and which is elongated in a direction perpendicular to the axial direction of the output shaft.

Abstract: Disclosed is a rotary actuator having a rotor and a stator which rotatably supports the rotor. The stator includes a coil bobbin, a stator coil, a pair of tapered poles and a yoke. The coil bobbin is formed from a non-magnetic material into a cylindrical shape and has the stator coil wound circumferentially thereabout. The pair of poles are disposed on the internal circumference of the coil bobbin. The yoke covers the outer surface of the coil bobbin and is in contact with the respective poles. The rotor comprises a rotary shaft and a diametrically polarized cylindrical magnet. The rotary shaft is inserted into the coil bobbin and is rotatably supported by the yoke. The magnet is carried by the circumference of the rotary shaft and is rotatable integrally therewith.