Development of Novel Continuous Variable Current Control for a Full-digital Pneumatic Cylinder Position Control System

摘要

Digital pneumatic and hydraulics is a quickly developing alternative for applications requiring cylinder motion control. In this paper, we describes the development of continuous variables current input for a full-digital pneumatic cylinder position control system and focus on a full-digital control valve (FDCV) which consists of four parallel connected 2/2 pneumatic on-off valves with different multiple flow-rate outputs. Compared to the conventional PWM-controlled proportional flow control valve using four fast-switching pneumatic 2/2 on-off valves, the new FDCV possesses several advantages like low operating noise, long life, ease of control and low cost. A simple but effective binary coding system is chosen for this study. Therefore, in this paper, a combination continuous variables current input for a novel full-digital control structure for a pneumatic positioning control system is developed to achieve better proportionality and reduce steady-state error. Finally, experiment results prove that the amplitude of the steady-state error is significantly reduced by using the proposed variable current input control and full-digital control scheme, therefore the FDCV together with the proposed novel variable current input control strategy is a potential alternative for precise close-loop pneumatic cylinder position controls.