VARIABLE STRUCTURE PID CONTROL OF FOUR-TANK SYSTEM WITH INPUT CONSTRAINT

Wang Chen, Han Guangxin

ABSTRACT:The four-tank system has a wide range of application backgrounds in process control, and usually has such prominent features as slow, time-delay, coupling, multiple-input, multiple-output, and strong nonlinearity, which imposes higher requirements on control strategies. In this paper, considering the actually existing input constraint, a variable structure PID control method is studied based on the feedback linearization of nonlinear system. Simulation results show that this control method improves the control performance obviously, compared with conventional PID control and is easier to apply in engineering.

Keywords:Four-tank system, Input constraint, Feedback linearization, Variable structure PID control.