A Low Cost Implementation of a PWM Controlled Servo-Pneumatic Axis

The paper is aimed at describing a low cost solution for a PWM controlled servo pneumatic axis, which is is part of a cartesian robot. The project fulfilled three main purposes: allowing students to practise with pneumatic actuators also in non-standard applications; demonstrating the feasibility of a position control for pneumatic actuators using commercial low cost components; researching in PWM control algorithms, dealing with static friction effects with two original tricks, based on special pulse for starting or short move- ments and a pulse duration correction dependent on the air path lenght. The paper describes into details the testbed, the implemented algorithms and the achieved results in terms of positioning accuracy, overall stroke time and motion uniformity.