抄録
As charging time is greater than exhausting time in a pneumatic resistance-capacitance circuit, the step-up and step-down response behaviors of the pressure feedback system are also different. This paper proposes a method of using an asymmetric pneumatic servovalve with software compensation, whose downstream portwidth is bigger than upstream one, for equalizing the rise time and step-down time with almost the same satiability instead of using a symmetric valve with software compensation for the high-speed force control of a pneumatic system in a spot welding machine. Using mathematical models of the pneumatic force control system, simulations of fuzzy control and proportional control systems with symmetric and asymmetric servovalve were carried out. When rise time is kept constant to be 3ms and the valve operates in linear and saturation ranges, step-down time is improved and reduced from 18ms for the symmetric servovalve with software compensation method to 5.6ms for the asymmetric servovalve with software compensation method.
