Designing MPC controllers by reverse-engineering existing LTI controllers
For control engineers, this provides a systematic way to retrofit existing LTI controllers with MPC's constraint-handling capabilities, though the approach is incremental.
This paper presents a method to design a constrained output-feedback MPC controller that matches the behavior of an existing LTI controller when constraints are inactive, using an inverse-optimal cost function. The method is demonstrated on three multivariable plants.
This technical report presents a method for designing a constrained output-feedback model predictive controller (MPC) that behaves in the same way as an existing baseline stabilising linear time invariant output-feedback controller when constraints are inactive. The baseline controller is cast into an observer-compensator form and an inverse-optimal cost function is used as the basis of the MPC controller. The available degrees of design freedom are explored, and some guidelines provided for the selection of an appropriate observer-compensator realisation that will best allow exploitation of the constraint-handling and redundancy management capabilities of MPC. Consideration is given to output setpoint tracking, and the method is demonstrated with three different multivariable plants of varying complexity.