Lock-in control system for spring suspended ring laser gyroscope

Claim 2

In combination with a spring-suspended ring laser gyroscope for providing a gyroscope readout which is proportional to angular input rate: a torquer, means for measuring the optical phase angle of the gyroscope and generating a signal proportional thereto, means for measuring the dither rate of the gyroscope and generating a signal proportinal thereto, and a feedback control unit for controlling the torquer to dither the gyroscope at a rate which is essentially equal to the lock-in characteristic of the gyroscope, the feedback control unit having as inputs the signals which are proportional to the gyro optical phase angle and to the dither rate.

Claim 3

The apparatus of claim 1 in which the angular acceleration u produced by the torquer is represented by the equation u=-k[ω.sub.d +ω.sub.L sin ψ]+Dω.sub.d where D is the damping factor of the suspension system ω L is the lock-in frequency k is a gain ω d is the measured dither rate ψ is the measured optical phase angle

Claim 4

The apparatus of claim 1 in which the angular acceleration u produced by the torquer is represented by the equation u=-k[ω.sub.d +ω.sub.L σ]+Dω.sub.d where σ is a signal representing the sine of the optical phase angle D is the damping factor of the suspension system ω L is the lock-in frequency k is a gain ω d is the measured dither rate

Claim 5

Apparatus according to claim 1 in which the feedback control unit includes: (a) a sine function generator having the gyroscope phase angle signal as an input and providing an output proportional to the sine of its input; (b) a first amplifier having the output of the sine function generator as an input and multiplying the input by an angular rate corresponding to the lock-in frequency; (c) a summing junction having the output of the first multiplier as one input and the measured dither rate as another input; (d) a second amplifier for multiplying the output of the summing junction by a factor sufficient to minimize the residual lock-in effect and for inverting the product; (e) a third amplifier having the measured dither rate as an input and multiplying the input by an amount proportional to the gyro scale factor; and (f) a second summing junction having the outputs of the second and the third amplifiers as inputs.

Claim 6

Apparatus according to claim 1 in which the feedback control unit includes: (a) a first multiplier for multiplying an output signal of the gyroscope representing the sine of the optical angle by an angular rate corresponding to the lock-in frequency; (b) a first summing junction having as inputs the output of the first multiplier and the measured dither rate; (c) a second multiplier for multiplying the output of the first summing junction by a factor sufficient to minimize the residual lock-in effect and for inverting the product; (d) a third multiplier for multiplying the measured dither rate by an amount proportional to the gyro scale factor; and (e) a second summing junction having the outputs of the second and third multipliers as inputs.