Nonlinear observer for pneumatic system with non-negligible connection port restriction

This paper presents an approach to design an observer for a pneumatic cylinder system for which the connection port comprises a non-negligible restriction. The pressure chamber of this system is difficult to control because the servo valve and the connection port form a double restriction. Moreover, the pressure in the cylinder cannot be directly measured and cannot be expressed as an explicit function of the measurable pressure. A nonlinear observer is further designed to estimate the pressure in the chamber by using the measured pressure outside the cylinder. The linear matrix inequality (LMI) approach is used to calculate the observer gains which ensure the exponential stability of the estimation error. Simulation results show good performance of the proposed observer.