Optimal designs of a hydromechanical hybrid transmission by minimizing fuel consumption and damage to human health

The hybrid hydromechanical transmission must be sized by fully exploiting its strengths: the energy contribution of the hydraulic source and the possibility of managing the thermal source at the most convenient conditions. Therefore, in this paper we propose a simulation-based optimisation which searches the design parameters values of both transmission and hydraulic source while minimizing the fuel consumption along a typical route. A second objective function involving emissions was also considered. The difficulty of managing numerous chemical species with different dangers has been overcome by summarizing them in a single parameter: the damage to human health. In this way the concept of emission correspond with the concept of damage to health. A study was carried out on a 12 m class urban bus. The results of this study allow us to evaluate the effects of the hybridization of a hydromechanical transmission and the effects of the engine management criteria, not only on the optimal values of the design parameters, but also on fuel consumption and damage to human health.