Design and implementation of a control scheme for a MEMS rate integrating gyroscope

Abstract

MEMS gyroscopes are found across a large range of applications, from low precision low cost applications through to high budget projects that require almost perfect accuracy. MEMS gyroscopes fall into two categories – ‘rate’ and ‘rate integrating’, with the latter offering superior performance. The key advantage that the rate integrating type possesses is that it directly measures angle, eliminating the need for any integration step. This reduces the potential for errors, particularly at high rates. However, the manufacturing precision required is far tighter than that of the rate gyroscope, and this has thus far limited the development of rate integrating gyroscopes. This thesis proposes a method for reducing the effect of structural imperfections on the performance of a rate integrating gyroscope. By taking a conventional rate gyroscope and adjusting its control scheme to operate in rate integrating mode, the thesis shows that it is possible to artificially eliminate the effect of some structural imperfections on the accuracy of angular measurement through the combined use of electrostatic tuning and capacitive forcing. Further, it demonstrates that it is viable to base the designs for rate integrating gyroscopes on existing rate gyroscope architectures, albeit with some modifications. Initially, the control scheme is derived through the method of multiple scales and its potential efficacy demonstrated through computational modelling using Simulink. The control scheme is then implemented onto an existing rate gyroscope architecture, with a series of tests conducted that benchmark the gyroscope performance in comparison to standard performance measures. Experimental work demonstrates the angle measurement capability of the rate integrating control scheme, with the gyroscope shown to be able to measure angle, although not to the precision necessary for commercial implementation. However, the scheme is shown to be viable with some modifications to the gyroscope architecture, and initial tests on an alternative architecture based on these results are presented.