Gyro motor control

Claim 1

In a precision gyroscope, an improved drive system for the gyro wheel comprising: (a) an induction motor having first and second stator windings and a rotor, said rotor mechanically coupled to the gyro wheel; (b) a magnet on said rotor and sensing coil means on said stator to provide sensing means with a pulse train output having a frequency proportional to the rotational speed of said rotor with the pulses of said pulse train having a phase related to the phase of said motor within a given cycle of rotation; (c) means to supply a reference frequency; (d) a phase detector having as inputs the detected phase of said rotor and said reference frequency and providing an output representing the phase error therebetween; (e) a voltage controlled oscillator having said phase error coupled thereto as an input and developing an output related thereto; and (f) motor control means coupled to said voltage controlled oscillator for developing two-phase signals for energizing said first and second windings comprising: (i) first and second bridges, each bridge comprised of four solid state switches in a bridge configuration, a respective first or second winding coupled across one diagonal of said bridge and a DC voltage across the other diagonal of said bridge; and (ii) means for developing from said voltage controlled oscillator output two signals shifted 90° in phase and at the desired operating frequency for driving the switches of said bridges.