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21 June 2019 An improved control structure for the tracking of sine command in a motion simulator
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The evaluation of inertial sensor’s frequency response is a crucial step during the development of such sensors (gyroscope, accelerometer…) or of embedding systems. An accurate measurement of the sensor’s gain and phase requires a test equipment, usually a motion simulator, able to create accurately controlled motions over a wide frequency band, with minimum amplitude and phase uncertainty. State-of-the-art motion simulators use permanent magnet synchronous motors as actuators and optical encoders as angular position sensor. They also include a servo-loop whose bandwidth is necessarily limited either for theoretical reasons, like the Bode Integral Theorem, or for physical ones, such as the inevitable time-lags occurring in the loop, or even mechanical resonances. Nevertheless, the appropriate bandwidth is required to allow for an accurate inertial sensor characterization. A well-known way of coping with the intrinsic limitations of the feedback control structure in a servo-drive consists in introducing a specific filter (called feedforward) between the motion trajectory generator and the feedback loop, to provide an anticipation independently of the feedback structure. This compensation requires a good modelling of the controlled system transfer function but is never perfect. Moreover, in a motion simulator, the tested inertial equipment is subject to change, and a unique feedforward filter cannot provide an accurate enough compensation. Thus, iXblue has introduced an adaptive feedforward structure in the controllers of their motion simulators, leading to a more accurate tracking of sine commands, beyond the initial closed-loop bandwidth. The benefits of this control structure are quite significant: the sine tracking is very accurate, having very little amplitude attenuation and phase lag.
Conference Presentation
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Bernard Vau, Damien Ponceau, and Mehdi Bussutil "An improved control structure for the tracking of sine command in a motion simulator", Proc. SPIE 11057, Modeling Aspects in Optical Metrology VII, 110570U (21 June 2019);

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