Characterising Angular Accelerometers using a Two-Axis Motion Simulator

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Abstract

Fault-Tolerant Flight Control (FTFC) systems reconfigure aircraft flight control laws to help restore a controlled flight and preserve acceptable performance under systemfaults. A typical approach to achieve fault tolerance is using inertial sensor measurementswhich can provide robustness to abrupt changes in the aircraft dynamics. This method does not rely on an accurate and full aerodynamic model, but only requires an estimate of the control effectiveness and an additional reconfiguration mechanism to the control laws such as switching, model following, matching, and adaptive compensation. With the inertial sensor being at the very heart of the control laws, to have proven and well-understood sensors is essential to increase the operational performance of a post-failure aircraft. Recent developments lead to FTFC systems that require angular acceleration feedback, which with the current conventional Inertial Measurement Unit (IMU) is obtained by taking the first derivative of the angular rates measured by gyroscopes. Because differentiation commonly intensifies noise and incurs a delay, a direct measurement of angular acceleration is anticipated to enhance the quality of the feedback signal. However, angular accelerometers are currently not part of the commercial aircraft system, which prompts the need to understand their characteristics. This thesis aims to investigate how an angular accelerometer can be evaluated and calibrated in a systematic fashion.