A robust repetitive control scheme with relaxed minimum time criterion

A repetitive control scheme is proposed for constrained nonlinear optimal control problems. The lower level of the algorithm adjusts switching times for bang-type controls and parameters of interval polynomial control approximations for non-bang segments. This procedure is based on a linearization of optimal controller and performs reduced optimization with a change of control structure whereas the upper level finds the optimal control and recalculates the linearization each time the deviation from the optimal solution becomes too large. The upper level control uses the MSE (monotonous structure evolution) method to determine the reference optimal control structure. Simulation and experimental tests show that the algorithm leads to the synthesis of an optimizing nonlinear controller, able both to perform close to time-optimal point-to-point transition as well as to stabilize the state.