Adaptive control of a pneumatic valve with unknown parameters and disturbances

The pneumatic valve is a position control plant with uncertain parameters and unknown disturbances such as friction and discharge fluctuation. An adaptive nonlinear switching-type robust control strategy is proposed to adjust the valve position in a closed loop manner. The controller consists of a feedforward compensator, a linear state feedback term, a parameter and constant disturbance identifier, along with a nonlinear switching controller to deal with time-varying disturbance. System stability is proved by use of the second method of Lyapunov. Experimental results show that the adaptive nonlinear control is effective in friction and discharge fluctuation attenuation, and guarantees good system performance in the presence of unknown plant parameters.