Exponential reaching law based adaptive sliding mode control of multivariable liquid level processes: An experiment study on quadruple tank process control

Industrial processes are complex and have uncertainties. The dynamic behaviour of these processes are needed in order to analyse and effectively control the process outputs of the system. An example of such a system is a Quadruple Tank Process (QTP) with multiple inputs and multiple outputs and nonlinearity due to coupling of the tanks. Therefore, Exponential Reaching Law Based Adaptive Sliding Mode Control (ERL-ASMC) has been proposed to solve the problem of nonlinearity, disturbances and parameter uncertainties. It is able to adjust to the control gain of the discontinous switching function so as to reduce the reaching time. It is very useful in minimizing chattering due to high frequency gain. It has also been compared with Adaptive Sliding Mode Control (ASMC) and Adaptive Pole Placement Control (APPC) which also use Parameter Estimation method like the ERL to determine the parameters of the QTP. These controllers are then finally compared with a Proportional-Integral-Derivative (PID) in order to better evaluate their performances. The evaluations are carried out based on the transient response specifications and the performances indices. The controllers are first simulated and then implemented on the real QTP in the laboratory. The proposed ERL-ASMC has the best performance in simulation and satisfactory results in the experiment. Key words: Quadruple Tank, Parameter Estimation, Adaptive Pole Placement control Sliding Mode Control, Exponential Reaching Law Based Adaptive Sliding Mode control