On the Performance Comparison between PI-LQR and Soft-Constrained MPC Applied to a 4-Tanks System

This paper shows a comparison between two linear controllers, a PI-LQR and a Soft-Constrained MPC applied to a Four-Tank process, which main characteristics are the nonlinearities, multiple inputs and outputs coupled together and slow behavior. The model was linearized around an operating point by using an optimization method, named least square. Also, a general mathematic formulation for both controllers is presented that can be extended to any process control. All the procedure is described in detail, as well as the simulation results for both controllers. To achieve a real performance comparison the experimental data are obtained under the same conditions, and all the response parameters were analyzed.