Two-stage Multivariable IMC Antiwindup (TMIA) control of a Quadruple Tank Process using a PLC

Actuator saturation is a common phenomenon in the control of multivariable systems which causes two major problems for control engineers, namely windup and directionality. This paper focuses on a Two-stage Multivariable IMC Antiwindup (TMIA) structure for open-loop stable plants. This IMC-based control structure is of interest because it tackles the aforementioned problems in an intuitive and easy to tune way. The highlight of this structure is the solution of two low-order quadratic programs to control both steady-state and transient behaviours of the plant. The controller is tested by application to a multivariable Quadruple Tank process controlled by a PLC. The TMIA structure is found to outperform its IMC counterparts in handling windup and directionality. Results obtained demonstrate the realizability of the advanced control technique on an off-the-shelf industrial PLC. Thus the TMIA structure is presented as a competitive alternative in terms of tuning transparency and reduced computations to other advanced control techniques such as MPC which are limited by the low computational power offered by standard PLCs.