To achieve more accurate tracking control, a control strategy for servo pneumatic systems based on the feedback linearization theory is presented. The nonlinear pneumatic actuator system is transformed into a linear system description, with a linear input–output map by regular static state feedback and state coordinate transformation. A servo tracking controller is then developed for the system based on the linear system model. Since there exists an inverse transformation for the new coordinate system, the designed servo control is transformed back to the original state coordinates with the original input variables. Two different cases are discussed: the pneumatic cylinder is driven (1) by a single five-port proportional valve and (2) by two three-port proportional valves. At the initial stage, for the convenience of analysis, the static friction forces are ignored. They are treated as uncertainties addition to the system in the later sections. For on-line implementation, the controller is simplified to require only position and velocity state variables in its feedback. The simulation results show that the simplified controller can drive the system to achieve the required tracking accuracy.
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