The fuel optimal control of modern vehicles involves the control of several components: the automated manual transmission, power split between the engine and secondary power converter, vehicle velocity, clutch position and motor start-stop. These controls are often optimized separate from each other, which leads to suboptimal results. In this paper we focus on the combined optimization of hybrid system use, gearbox and vehicle velocity. A novel cost function description is used which describes the influence of the automated manual transmission, the potential of brake energy recovery, and the vehicle velocity with one control signal, and, therefore, reduces the computational complexity. The cost is modeled using a piecewise affine continuous function, which has the advantage of the control appearing affine in the Hamiltonian. Besides the standard optimal control solution for systems with an affine cost function, non-smooth optimal control theory is involved to obtain a solution shape that fulfills the necessary conditions of optimality. Since the length and cost of each subarc, that fulfills the necessary conditions of optimality, in travel time and fuel consumption, can analytically be expressed in its start and end state, the fuel optimal control of a vehicle with energy recovery options is rewritten as a nonlinear optimization problem.
|Title of host publication||Proceedings of the 18th IFAC World Congress, 28 August - 2 September 2011, Milan, Italy|
|Place of Publication||Oxford|
|Publication status||Published - 2011|