Magnetorheological Fluid-Based Threshold-Feedback Overload Protection System for the Miniature Turbine Generator

How to combine phase transition properties of magnetorheological (MR) material with control strategies in a micro-space is the key to promote the application of micro rotary mechanical system. Current control strategies are mainly developed for large-scale magnetorheological actuators, for which the energy conversion efficiency is different from that of the miniature MR actuator. This study proposes a threshold-feedback overload protection strategy for a miniature turbine generator. Sensorless control for the miniature turbine generator's rotational speed is also developed by directly capturing the frequency of the output voltage. The MR fluid-based threshold-feedback overload protection system is systematically modelled to explain its operating principle for the rotational speed. A series of threshold voltage (Ur=4.0 V, 5.0 V and 6.0 V) was used to test the threshold-feedback overload protection control effect. Results show that the rotational speed is controlled from 8333 r/min to 5312 r/min with a threshold voltage of 4.0 V. Experimental results can be well explained by the proposed MR fluid-based threshold-feedback model. A favourable threshold-feedback overload protection effect is also demonstrated under the variable wind speed condition. We believe this work is significant for the function expanding and performance improvement of miniature turbine generator.