Boehme, T., Frank, B., Schultalbers, M., Schori, M. et al., "Solutions of Hybrid Energy-Optimal Control for Model-based Calibrations of HEV Powertrains," SAE Technical Paper 2013-01-1747, 2013, doi:10.4271/2013-01-1747.
In this paper optimal control problems for hybrid powertrain vehicles with different drive-modes are considered and solved using numerical techniques. This leads to the formulation of hybrid optimal control problems. The aim is to find optimal controls and optimal switchings between the drive-modes to minimize a cost function resembling fuel consumption. The problem is nonlinear and subject to constraints concerning both controls and state. The techniques include indirect methods as well as direct optimization methods. Efficiency and accuracy are evaluated for all methods using simulation studies. An experimental test on a near mass-production vehicle confirms the usability of the direct optimization approach.