Phase locked loop control system gyroscope wheel speed control system - uses phase-locked loop having low response provided by frequency divider and low pass loop filter

摘要

The phase-locked loop includes a h.f. (e.g. 20 MHz) crystal controlled voltage controlled oscillator (VCXO); a divider (33b) for dividing the VCXO frequency down (e.g. by six decades); a phase comparator (35) for comparing the output of the divider with a low frequency reference signal. A loop filter (37) is provided for filtering the output of the phase comparator so as to give the loop its desired dynamic response characteristic and bandwidth. A summing amplifier (39) sums the output of the phase comparator with a modulation signal. The arrangement controls the frequency of the power applied to a gyroscope to rotate the seismic mass (wheel) of the gyro so as to compensate for movement of the gyro case about the spin axis of the gyro, the modulation signal having a voltage level linearly related to the rate of movement of the gyro case about its spin axis. This signal is obtained from a second gyro mounted so as to sense movement about the spin axis of the gyro whose power frequency is being modulated.