ABSTRACT
High dynamic and static performances of the pneumatic actuators with closed-loop control systems can be achieved using “multilevel” (displacement, velocity, acceleration, and others) feedback modern control algorithms. An effort to achieve accurate state variables of the pneumatic actuator is the major aim of a design process in such systems. This issue can be solved by two approaches:
1. Measurement of these parameters using appropriate sensors 2. Application of parameter estimation techniques
In general, the displacement, velocity, acceleration, force, moment, and pressure can be measured in the pneumatic actuator. Different sensor designs may read incrementally or absolutely; they may contact a sensed object or operate without contact; and they probably will range through various levels of performance and price. Direct measurement of all state parameters of the pneumatic actuator during operation may be sometimes exceedingly difficult and expensive, if possible at all. Hence, the application of parameter estimation techniques can provide this key information indirectly. A variety of such techniques is available; however, one of the most powerful is the observer method. In state regulators, the differential method is often used; in this case, the velocity and acceleration of the actuator load are calculated by differentiating a measured displacement signal.
