Development of Low-Cost Pressure Control Type Quasi-Servo Valve Using Embedded Controller

Today, the advanced age and less children society is growing up rapidly. The care and welfare equipment to support a nursing care and a self-reliance of the senior and the disabled are actively researched and developed by many researchers. However, the power assisted device required many degrees of freedom. The total weight of the wearable devices using fluid control devices increases so that the number of actuator and control valves increases according to the degree of freedom. Therefore, in our previous study, we developed a small and light-weight quasi-servo valve to reduce the burden of the user. In this paper, we proposed and tested a quasi-servo valve by using the small, light-weight and low-cost on/off valves driven by the pulse width modulation method. The valve consists of two on/off valves and a microcomputer. Both valves are connected in serial. One valve is used as a switching valve to exhaust or supply, and another is used as a PWM control valve that can adjust the valve opening. And we confirmed that the output flow rate of the tested valve could be adjusted in analog way. We also proposed the precise analytical model of the tested valve. By comparing the experimental result with the calculated results using the proposed model and the identified parameters, we confirmed that the model of the valve was valid. In the next step, a pressure control type quasi-servo valve is proposed and tested. The tested valve consists of the quasi-servo valve, a pressure transducer and an inexpensive tiny micro-computer. As a result, by using the tested valve and P control method with the compensation for the supplied and exhausted flow rates, the pressure control performance of the tested valve could be improved.