Abstract
The speed control of a pneumatic cylinder is usually of an open loop type, adjusted manually by a flow control valve. In this manner, especially when operated at a low driving speed, the constant speed can barely be obtained due to the friction or variations in the load force.
In this study, for low and constant driving speed, the PWM mode feedback speed control method is proposed in which the piston speed is controlled by the PWM mode being driven by an on-off valve. The control system is constructed by using an automobile-type fuel injection valve with high response and endurance as the valve driven in the PWM mode. The characteristics and performance of the control system are analyzed and discussed to obtain the following results.
1) An electro-pneumatic speed servomechanism can be cheaply constructed and it can easily realize a very low and constant driving speed.
2) The theoretical index for the proper choice of the carrier frequency in the PWM was obtained. The stability and limit of stick-slip generation could be theoretically evaluated. Thus, the design guide of the control system could be derived.
