An inductive potentiometer for supplying a d.c. output voltage, which is linearly variable as a function of the rotation angle of a spindle. The potentiometer is constituted by a synchro-resolver and two associated circuits, an a.c. voltage supply circuit of one stator winding incorporating an oscillator whose amplitude is controlled by the supply voltage and an output circuit connected to the rotor which incorporates a demodulator stage. The linearization of the voltage as a function of the angular position of the spindle is ensured by a circuit shunt incorporating an amplifier whose gain is close to 0.5 controlling another stator winding. Temperature compensating windings can be included on the stator.
A method and apparatus by which the output value of a resolver position detection system is compensated for systematic phase shift errors produced by signal conditioning circuitry through which the signal passes.
A safety device for a power window in which window glass of a vehicle is made to undergo an opening or closing operation by a driving motor, and which effects safety control against the nipping of a foreign object by detecting the opening and closing positions of the window glass, comprises: a position sensor for detecting the position of an angle of rotation of the driving motor; a detector the opening or closing position of the window glass based on an output of the position sensor; and a controller for effecting safety control against the nipping of the foreign object based on the detector.
A reflective deflector of a light beam which scans in opposite directions across a bar code is controlled in scan angle by monitoring the AC component of a current passing through a winding of a scanning motor which oscillates the deflector to scan the beam across the code over a scan angle. The inductance of the winding corresponds to the length of the scan angle and is measured in terms of the peak to peak value of the AC component during a scan period or frame which occurs over an interval corresponding to the reciprocal of the scan rate. During successive periods, successive trains of pulses are generated. The number of pulses or their duty cycle during each period is changed in accordance with an error signal corresponding to the difference between the desired scan angle and the peak to peak value of the AC component. The pulse trains are translated into trains of current pulses which are passed through another winding of the motor in opposite directions so as to drive the rotor of the motor which reciprocates the reflector in opposite directions over the desired scan angle. By modifying the desired scan angle in accordance with changes in temperature affecting the system, the system can be compensated for temperature changes. By modifying the error signal by processing it with a filter, the response of the system to changes in scan angle can be controlled.
