Design Methods of Oscillation Loop for Vibratory Gyroscopes using Working Range of Phase Locked Loop
In this paper, the systematic design and analysis of an oscillation loop for vibratory gyroscopes is proposed. A vibratory gyroscope measures the external angular rate by detecting the Coriolis force of the resonator. Therefore, the gyroscope structure must vibrate at all times. An oscillation loop is an electronic circuit that induces and sustains the vibration of the resonator of a gyroscope and it is an important part of the vibratory gyroscope. To obtain high performance, the oscillation loop must fix the vibration frequency to its resonant frequency. Because the oscillation loop decides a frequency of the vibration of the gyroscope resonator, it is an important part of vibratory gyroscopes. The oscillation loop has the same form as PLL widely used in various fields of electronic applications. Therefore, the design and analysis of phase control loop is deeply involved in the PLL theories.
This paper is organized as follows. First, a brief introduction of PLL and a linear PLL model is presented. Second, the PLL used in an oscillation loop is examined and its characteristics are specified. Third, stability analysis and working conditions of the specified PLL is represented. Finally, based on the previous results, a systematic design method of the phase control loop is proposed. The designed control loop made by the suggested method is simulated using parameters of ring type MEMS gyroscope. The simulation corresponds well to the desired performance. Moreover, experiments are also performed using real gyroscopes. Experiment results not only show that the loop operates well, but also corresponds with simulation results.
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