Abstract
The difficulty caused by the non-linearity of a pneumatic servo system is overcome by linearization of input-output via Direct Feedback Linearization (DFL), and a state feedback controller is then designed using the linear system theory. Good dynamics and high disturbance force rejection level are achieved by putting the non-dominant poles near the imaginary axis and far away from origin, and high disturbance force rejection enables the system to have high precision and high stiffness. Nonlinear uncertainty of pseudo linear system resulting from the changing running conditions and the inaccuracy of the model are established together with its linear bound. The analysis completed by applying Zero Exclusion Principle (ZEP) showed the controller is robust. Experimental results proved that the nonlinear state feedback controller is robust; it has an accuracy of±0.02mm and a repeated accuracy (3σ) of ±0.05mm; the smallest step command the system can follow is 0.2mm; and it has a fairly high stiffness, too.
