On the Influence of Velocity and Acceleration Estimators on a Servopneumatic System Behaviour

Pneumatic systems are clean and reliable actuators, presenting very high force to weight ratios. They further present some advantages, such as inherent compliance and suitability for fire hazard environments. However, their intrinsic nonlinearities have hindered a more wide range of applications, leading to the use of complex control laws that typically require the knowledge of velocity and acceleration. This means that the velocity and acceleration estimators might play a crucial role in servopneumatic systems control, since a difficult to achieve balance between differentiation noise and phase lag must be inferred by the control engineer. This paper experimentally compares the performance of several velocity and acceleration estimators, relying upon a digital encoder position signal. The comparison is performed not only regarding the quality of the actual estimates per se but also on their effect on the control error and control action obtained when using a nonlinear sliding mode-based controller.