Force to Rebalance Control of HRG and Suppression of Its Errors on the Basis of FPGA

Xu Wang,Wenqi Wu,Bing Luo,Zhen Fang,Yun Li,Qingan Jiang

doi:10.3390/s111211761

Xu Wang, Wenqi Wu + Show 4 more

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https://doi.org/10.3390/s111211761

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Abstract

A novel design of force to rebalance control for a hemispherical resonator gyro (HRG) based on FPGA is demonstrated in this paper. The proposed design takes advantage of the automatic gain control loop and phase lock loop configuration in the drive mode while making full use of the quadrature control loop and rebalance control loop in controlling the oscillating dynamics in the sense mode. First, the math model of HRG with inhomogeneous damping and frequency split is theoretically analyzed. In addition, the major drift mechanisms in the HRG are described and the methods that can suppress the gyro drift are mentioned. Based on the math model and drift mechanisms suppression method, four control loops are employed to realize the manipulation of the HRG by using a FPGA circuit. The reference-phase loop and amplitude control loop are used to maintain the vibration of primary mode at its natural frequency with constant amplitude. The frequency split is readily eliminated by the quadrature loop with a DC voltage feedback from the quadrature component of the node. The secondary mode response to the angle rate input is nullified by the rebalance control loop. In order to validate the effect of the digital control of HRG, experiments are carried out with a turntable. The experimental results show that the design is suitable for the control of HRG which has good linearity scale factor and bias stability.

Highlights

A hemispherical resonator gyro is a solid state gyroscope which has achieved inertial grade performance
The power and signals were transmitted through a slip ring to the related hemispherical resonator gyro (HRG) device and an oscillograph was applied to monitor the working status of the HRG
A FPGA digital circuit board design for a HRG is realized based on the proposed control scheme and math model and relative experiments that are described in this paper

Summary

Introduction

A hemispherical resonator gyro is a solid state gyroscope which has achieved inertial grade performance. In [4], the principle of WA mode operation is reviewed and its electrical control and readout methods are discussed in detail In this mode, the standing wave of a vibrating pattern is allowed to precess freely around the circumference of the resonator. Matthews employed the HRG with a 30 mm in diameter resonator operating as a rate gyroscope, which is operated under the condition of “Force-ToRebalance” (FTR) mode [6,7] In this mode, the standing wave of the vibrating pattern is maintained at a prescribed position, usually with the antinode of the standing wave aligning with 0° electrode. Comparing the two working modes, the “Force-To-Rebalance” mode has a higher resolution and a much simpler readout system than that of the “Whole Angle” mode [8]

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