Integrated design for a CVT: dynamical optimization of actuation and control

With increasing demands on more energy and fuel efficient vehicles, one can achieve the goal by improving the vehicle powertrain system. A continuously variable transmission (CVT) allows the engine or electric machine to operate on its optimal operation points. The optimal operation points are high efficiency points that lead to reduced energy consumption of the vehicle. However, this type of transmission may still have relatively high actuation losses (depending on the actuation type), which hinders the energy saving benefits. Classically, the plant (e.g., actuation system, variator) of the CVT was separately designed from the control design. In this paper, an integrated optimal CVT variator and actuation control design is presented. The aim of the new design is to minimize the CVT mass (pulley sheaves, belt), tracking error and control effort. To achieve this goal, a nested optimization framework is implemented to obtain an optimal transmission system design over a selected drive cycle. The results show that the optimized CVT design yields non-compromising tracking performance, however, with much smaller variator mass (-46%) and control effort (-62%).