Persistency of excitation in subspace predictive control

Abstract This paper presents a method that ensures persistency of excitation for subspace predictive control. This control method is characterized by the combination of a predictive control law with a subspace predictor. The subspace predictor is continuously being adapted to the controlled system by using input-output data from this system. For this purpose the input-output data should be persistently exciting. In this paper a method is proposed to ensure persistency of excitation by adding a term to the cost function used by the predictive control law. This term is designed such that only the least excited directions of the input space are additionally excited. An advantage of the method is that the optimization problem that needs to be solved for the predictive controller can still be solved by using quadratic programming. The proposed excitation method is evaluated in simulation on a detailed nonlinear model of a transport aircraft. The simulation results clearly show the usefulness of the proposed method.

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