Abstract: A rotational sensing system for a Multioscillator ring laser gyroscope is disclosed herein that can operate with a simple upright symmetric optics mechanism, where the required signal separation is performed fully electronically, with the use of a local oscillator. The technique allows for rotational rate and direction detection, as well as cavity length control, with a minimum of cross-talk.

Abstract: Single and multiple axis fiber optic gyroscope systems employ orthogonal sequences to minimize the effects of both intra and inter-axis crosstalk. Sequences for driving electro-optic modulators are derived by examination of underlying primary and secondary demodulation sequences. Such underlying sequences are examined for orthogonality in accordance with a number of selection rules. When the selection rules are satisfied, the corresponding modulation sequences for driving the gyro(s) are identified and applied. By selecting the modulation waveforms in accordance with orthogonality criteria, one is assured of mean-zero bias errors within a predetermined number of loop transit times.

Abstract: A ring laser gyro having a ring laser that preferably has four legs and four corner mirrors. At least one of the corner mirror is partly transmissive, and the transmitted beam is sensed and converted into a digital signal. The digital signal is fed back in two computer loops to at least one digital-to-analog converter, and thence to a transducer which drives at least one corner mirror inward and outward. One of the computer loops includes a stepped demodulator having four steps per cycle. The steps have voltages at the operating voltage of the transducer, that voltage plus an increment, the operating voltage, and that voltage less a decrement. The first loop sends an operating voltage to the digital-to-analog converters. The second loop demodulates the beam signal at a second harmonic of the demodulation of the first loop to produce a voltage signal which controls the amplitude of dithering of the movable mirrors.

Abstract: Digitized heterodyne signals in a ring laser gyroscope are processed to determine the phase and acceleration of heterodyne signals at turnarounds in the angular motion of the frame of the ring laser. A hybrid analog/digital design that incorporates the necessary logic processes the turnaround data to produce a phase correction that can be added to the gyroscope count to correct phase errors that at each turnaround. Separation of high speed data processing from lower rate data simplifies the code and permits evaluation of turnaround correction performance. A fully digital system determines a phase distribution for the detected turnarounds and processes the phase distributions of the heterodyne signals for a multiplicity of turnarounds to determine an angle towards which the phase distributions are skewed and the amount of that skew.

Abstract: A dither drive system for a ring laser gyroscope includes a computer, a digital to analog converter, a filter, and a power amplifier. The system senses the dither frequency of the gyro frame and produces a digital signal that corresponds to a specified dither drive signal and toggles the dither drive signal to drive the flexure at its resonant frequency. The dither drive system generates digital waveforms that approximate the sine function and digital waveforms that approximate the cosine function and applies the digital waveforms in quadrature to the flexure.

Abstract: An apparatus and method of determining gyro het phase and acceleration at turnaround using the digitized heterodyne signals. A digital design that incorporates the necessary logic and is integrated into a gyro unit. An integer algorithm that processes the turnaround data to produce a phase correction that can be added to the gyroscope count. Separation of high speed data processing from lower rate data to simplify the code and permit evaluation of turnaround correction performance.

Abstract: The use of a high speed moving average filter is shown to filter high speed errors, including white noise in angle and quantization errors, from the output data of a ring laser gyro while it is being tested. The filtered data permits investigation of the lower speed, random walk in angle error of the gyro being tested. For best results, several moving average filters are connected in series.

Abstract: A phase locked loop is disclosed which subtracts an estimated signal from an input signal and operates upon the residual signal. The residual signal is demodulated and applied to a controlled oscillator which produces feedback signals approximately the sine and cosine of the input signal. The cosine feedback signal is multiplied by the residual signal whose resultant signal is a frequency correction signal. The sine feedback signal is multiplied by the residual signal for multiplication again by the sine feedback signal to produce the estimated signal which is amplitude and frequency controlled. This signal is then subtracted from the input signal to reduce the residual signal to near zero.

Abstract: A nuclear magnetic resonance gyroscope is disclosed that operates on the principle of sensing angular rotation rate as a shift in the Larmor frequency of one or more nuclear species that possess nuclear magnetic moments.