Stepper motor control

Claim 1

In a stepper motor control system for moving an output member to a position proportional to an electric analog input signal an analog voltage generating member responsive to said position for generating an electric analog feedback signal proportional to said position, motor means, control means for supplying a control voltage for actuation of said motor means, said control means including members responsive to the difference between said input and feedback signals for delivering a control voltage proportional to the magnitude and direction of said difference, said motor means comprising a rotor element having permanently magnetized poles around its periphery and a stator element having a plurality of phase windings arranged to advance said rotor element one pole space each time said windings are selectively energized. said control means also including converting means responsive to said control voltage for generating electric pulses for energizing said stator windings, said converting means comprising an error direction comparator for delivering a logic signal for one polarity of said voltage and a different logic signal for the opposite polarity of said voltage, an absolute value amplifier for delivering a regulating voltage proportional to the absolute value of said control voltage, a voltage controlled oscillator responsive to said regulating voltage for generating pulses at a frequency directly related to said regulating voltage, interface means responsive to said logic signals and to said pulses for establishing a sequence of pulses for controlling the operation of said motor, amplifying means for said sequential pulses for energizing said windings, power cut-off means interposed between said interface means and said amplifier means, and a one shot timer module receiving pulses from said voltage controlled oscillator and providing output pulses of limited duration for controlling said power cut-off means.