Dead Zone Compensation in Pneumatic Servo Systems

This paper presents an approach for dead zone compensation in pneumatic position servo systems. The dead zone is an inherent nonlinearity in pneumatic servovalves, where for a range of input control values, the valve gives no output flow. Although pneumatic actuators are very common in industry, they have limitations in servo pneumatic applications that are caused by typical non-linearities of Pneumatics, as servovalve dead zone, air flow-pressure relationship through valve orifice, air compressibility and friction effects between contact surfaces in actuator seals. The servovalve dead zone compensation is easy to implement and brings important results in trajectory tracking control applications, according to depicted in this paper. A mathematical model to dead zone in pneumatic servovalves is presented, followed by the method used to compensation, that is made with the addition of an inverse dead zone function in control system. Tests are carried out to validation using controllers with and without dead zone compensation to comparison. Experimental results show that dead zone compensation improves controller performance. Dead zone compensation is easy to carry out, turns possible use simpler controllers in control and is an important procedure to develop controllers to application of Pneumatics in Robotics.