Modelling and Non-linear Control Design for Coupled Twin Tank Level Process

The liquid level control in Coupled Tank System is a basic problem in process industries. Many times the liquids will be processed by chemical or mixing treatment in the tanks, but always the level of fluid in the tanks must be controlled and the flow between tanks must be regulated in presence of non-linearity, disturbance and time varying system parameters. The control of liquid level in tanks presents a challenging problem due to its non-linear behavior. This paper deals with non-linear control designs using higher order Sliding Mode Control (SMC). For the consideration of non-linearity and to realize level position regulating and tracking control, a non-linear Integral Sliding Mode Control (ISMC) is used which guarantees the asymptotic stability of closed loop system and reduce the chattering problem associated with Standard Sliding Mode Control (SSMC). The goal of the control algorithm is to track the desired level of liquid in second tank by using flow rate of liquid into first tank as the manipulated variable.