"Initial Tuning of Predictive Controllers by Reverse Engineering"
Edward Hartley
Dep. of Engineering, University of Cambridge
Abstract:
The tuning of MPC controllers is considered by some to be a "dark art". This talk demonstrates an alternative method for finding an initial tuning of a linear MPC controller by using an existing LTI output feedback controller as its basis. A state observer and cost function are obtained to provide an unconstrained MPC controller that reproduces the behaviour of an existing output-feedback controller, although it is not necessary for the existing controller to be of the same order as the plant. Having transformed the original controller into the form of an MPC controller, the additional benefits of using constrained optimisation can be realised.
The observer and cost function that reproduce the original unconstrained controller are non-unique. However, the different realisations can differ greatly from each other in their closed loop performance once constraints are added to the mixture. The effects of this degree of design freedom are explored, and suggestions proposed for obtaining an effective constrained controller in this manner.
Finally, the method is demonstrated by application to the final phase of a spacecraft rendezvous scenario.
(slides)
