PWM controlled Micro ER Valve and Its Application to Micro Actuator Control

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ER fluids are one of a family of functional fluids, which show dramatic and reversible rheological changes in several millisecond when the electric field is applied. Therefore, in the ER fluid hydraulic circuit systems, it impossible to control the pressure and flow rate using an ER valve consisting of only electrodes with no moving parts. In this research, the PWM control of the ER valve has been proposed because the ER valve works as an ON-OFF valve, and in order to develop a micro-actuator system driven by PWM controlled micro-ER valves featuring the miniaturization of the ER valve, the following investigations have been done.(1) The flow rate control characteristics and micro flow patterns of fundamental ER valves consisting of two glass electrodes whose gap ranges from 0.8 to 0.1 mm have been investigated under DC electric control and PWM control, and the effects of the gap size, the applied DC electric field strength, the carrier frequency of the PWM wave and the pressure differe … More nce across the ER valves on the flow rate control characteristics and micro flow patterns have been clarified.(2) For the oscillatory flow of an ER fluid within a two-dimensional rectangular channel consisting of two glass electrodes. the micro-structural flow patterns have been observed using a microscope, relating to the viscoelastic properties of the ER fluid evaluated from the relationship between a defined fluid strain and the pressure difference. The effects of the fluid strain amplitude and frequency of the oscillatory flow and applied electric field strength have been clarified.(3) On the basis of the above results, a miniature bellows actuator driven by three ports ER valve having a pair of micro ER valves has been developed, The several synchronized control strategies of a pair of PWM controlled ER valves have been tried to determine the suitable one. And then, a position feedback control strategy with P11)compensator in which the duty ratio of PWM wave for the ER valves was varied in proportion to the output -signal of the PID compensator was applied to the developed miniature actuator, and the control performance was investigated to construct a high precision micro servo-system using the ER fluid. Less