Quadrature control of Hemispherical Resonator Gyro based on FPGA

The quadrature drift mechanism of the Hemispherical Resonator Gyro is analyzed and its equation is deduced in order to suppress the quadrature drift. The resonator's two vibration modes which have different frequencies and damping decay rates cause the quadrature drift. Furthermore, the drift caused by different damping decay rates can usually be reduced by calibration, but the drift caused by different frequencies only can be suppressed by the quadrature control loop. The phase error of the 0-degree and 45-degree vibration signals are employed to eliminate frequencies split with quadrature control loop. And the FPGA digital control loop is introduced. Experiments show that the quadrature drift can be suppressed effectively by using the method mentioned before.