MR fluid-based threshold-feedback overload-protection system for miniature turbine generator

Miniature turbine generators, which can supply power to miniature mechatronical system by converting natural energy, are promising for future applications in micro-aircraft, ammunition, and missiles. However, turbine generators are at the risk of rotor wear and circuit failure under high wind-penetration conditions. As the feature size decreases, conventional sensors can hardly be integrated in microsystems, making control more difficult. In addition, microspace demands higher practicality of control strategies. Existing complex control units of large-scale systems are not applicable to microsystems. Therefore, a safe and robust control strategy that incorporates practical applications should be considered. This study aims to bridge the gap between the phase-transition properties of magnetorheological (MR) materials and control methods in a microspace. A MR fluid-based threshold-feedback overload-protection strategy is proposed for the miniature turbine generators. This strategy realises the sensorless control of miniature turbine generators by directly capturing the output frequency. To accurately describe the control characteristic of the overload-protection system, a dynamic model of the rotating shaft is proposed. A series of threshold voltages (U_r = 4.0, 5.0 and 6.0 V) is used to test the controllability of the overload-protection system. Experimental results show that the rotational speed of the miniature turbine generator is effectively controlled under hurricane-force wind conditions (v = 40 m s⁻¹). Consequently, this study has developed a control strategy to solve the overload failure of miniature turbine generators. Under low wind speeds, the miniature turbine generator starts reliably. When the wind speed exceeds the threshold value, the miniature turbine generator is protected from overload failure. We believe that this work is invaluable for the functional expansion and performance improvement of miniature turbine generators.