Microprocessor Based Position and Velocity Control of a Pneumatic Actuator for Low Cost Automation Applications

In every industry, automation has become essential to meet the global standards and requirements. But it is highly costlier in doing it in a conventional way. This paper describes how microprocessor based controls can be used to produce low cost automation. Position and velocity control is a common requirement in the industry. About 70% of the industry requirements don't need high precision of operation.

In this paper, an attempt is made to control the position and velocity of a pneumatic actuator. The test system includes a servovalve (modified), pneumatic rotary actuator, flywheel, incremental encoder, microprocessor, stepper motor and micrometer. All the components are connected with each other in a closed loop system.

Two circuits were designed to interface the encoder and stepper motor with microprocessor. Experiments were conducted to obtain the characteristics of the servo valve and the actuator. Based on characteristic curves, assembly level programs were written to control both the position and velocity of the pneumatic actuator. Both the parameters were successfully controlled within the desired accuracy, i.e., position within ± 5 Revolutions and velocity or speed ± 30 RPM. This finds applications in fixed automation, robotics, pick and place and etc.