Adaptive Control of MEMS Mirror Laser Sensors

Scoring competitions such as gymnastics have a particularly high demand for accuracy and fairness of judgment. In recent years, Fujitsu has collaborated with the International Gymnastics Federation and Japan Gymnastics Association to develop an “artificial intelligence gymnastics judgement system” using three-dimensional laser sensors. In this system, multiple microelectromechanical system (MEMS) mirror-type laser sensors are used for the stereoscopic measurement of gymnastics. MEMS mirrors are typically driven at the same frequency as their mechanical resonance frequency. Because the amplitude and phase greatly fluctuate with changes in resonance frequency, controlling the rotation angle to keep the amplitude and phase accurate is crucial. Herein, we developed an amplitude control method that does not use the mirror rotation angular velocity using a sin/cos amplitude model. We developed an adaptive control system for system parameter fluctuations because of changes in the resonance frequency of a MEMS mirror system. Using the developed method for the sin/cos amplitude model, we can theoretically evaluate the stability of the control system and the convergence to the target value. Through numerical simulations where this controller was applied to a high-order model with characteristics similar to those of the actual machine, we confirmed that the amplitude tracking error and convergence time were reduced even when the system parameters fluctuated significantly, demonstrating the usefulness of the proposed adaptive control system.