Development of a control method for micro-gyroscopes using self-excitation and frequency measurement techniques

Micro-Hemispherical Resonator Gyroscopes (MHRGs) serve as essential components in inertial navigation systems. This research introduces a novel digital closed-loop control system for the application of the force-to-rebalance mode. The proposed methodology utilizes a self-excitation technique to initiate oscillation. First, the amplitude of the oscillatory signal detected by the Analog-to-Digital Converter (ADC) is calculated. This amplitude is subsequently amplified by a predetermined factor and multiplied with the ADC-detected signal. The resultant product serves as the input for the digital-to-analog converter, facilitating the generation of a drive signal for the MRHG. Upon the oscillation amplitude attaining a specified threshold, the control system transitions the drive control to the Direct Digital Synthesis (DDS) module. Concurrently, we employ a high-frequency clock to measure the frequency of the ADC sampling signal. The measured frequency is then used to establish a reference frequency range for the Proportional-Integral-Derivative (PID) controller, with the aim of expediting the convergence speed. Finally, a PID block based on the standard IEEE-754 floating-point format is implemented to perform fine-grained adjustment of the DDS frequency control word. Experimental results demonstrate that the amplitude control shows a variation of ±1% with respect to the reference value. For MHRGs with different Q factors and resonant frequencies, the phase error between the drive and detection signals is maintained within ±0.5°.