Inertial reference system

Abstract

An inertial sensor assembly (ISA) includes a cluster of three ring laser gyros, each gyro producing an output signal having a pulse repetition rate representative of the rate of angular deviation of the ISA about one of three coordinate axes X, Y, and Z. The ring laser gyros are synchronously dithered at a relatively constant rate. The ISA also includes a triad of three accelerometers, with each accelerometer producing an output signal representative of the rate of velocity deviation of the ISA along one of the X, Y, and Z coordinate axes. A first processor, P1, accumulates the pulses produced by each ring laser gyro over its dither period. The resultant counts are stored in registers for subsequent sampling by the P1 processor at a periodic sampling rate which is greater than the dither rate. The P1 processor then synchronizes each sampled pulse count to a common sampling interval, thereby eliminating errors otherwise caused by using positional data values taken at different times. The P1 processor also compensates the ring laser gyro and accelerometer-produced signals at the sensor and the system level for effects such as temperature, bias offsets, scale factor and misalignment by the use of compensating coefficients stored in electrically erasable, programmable read-only memory. The processed data from the P1 processor are passed to a P2 processor which performs navigational computations to thereby produce computed positional information.