DEVELOPMENT OF A MICROPROCESSOR-BASED CONTROL-SYSTEM FOR A PNEUMATIC ROTARY ACTUATOR

A microprocessor based control system has been developed and used to provide satisfactory control of a pneumatic servo system. This paper describes how microprocessor based controls can be used to produce low cost pneumatic servo drives which could find a wide range of application in manufacturing industries. The pneumatic actuator is a piston air motor constructed of aluminium, utilising a proportional spool valve to allow air flow control. The dynamics of the air motor in conjunction with the solenoid valve have been experimentally determined. Control is based on a modified PID (proportional, integral and derivative) controller which adjusts the command issued to the control valve. This takes account of the inherent non-linear behaviour of the air motor. The motor has been used to actuate a single-degree-of-freedom (SDOF) robot arm. The results show that digitally controlled air motors have the potential of providing an alternative solution to their electric and hydraulic motor counterparts. Air motors, through inherent low cost, good power to weight ratio and intrinsically safe operation, can be utilised to control a wide range of industrial machines.