Optimizing a Hybrid Diesel Power Unit Using Extremum-Seeking Control

In this paper, the problem of optimizing the steady-state efficiency of a hybrid single-cylinder diesel power unit at a specified electrical output power level is investigated. The special characteristic of the proposed concept is that the high dynamic torque trajectory generated by the electric motor is used as an optimization variable and no modeling of the thermodynamic processes is necessary. The resulting problem corresponds to an equality-constrained optimal control problem that is solved by applying the discrete-time variant of extremum-seeking control together with a separate feedback controller. The stability of this extremum-seeking-based optimization scheme is comprehensively analyzed by using singular perturbation and averaging methods. Simulation results based on a mathematical model of the plant demonstrate the robustness and accuracy of the concept. Besides that, experimental results are presented that attest the need for a model-free optimization approach as well as the efficacy of the concept.