Improving energy efficiency and robustness of a novel variable valve actuation system for engines

This study presents a new variable valve actuation (VVA) system, which is optimized to pursue the minimum energy consumption and the minimum sensitivity of the valve lift to cycle-to-cycle variations of engine pressure. Therefore, an experimentally verified mathematical model is proposed to calculate the objective function and constraints at each optimization step. Due to the complexity and constraints of the objective function along with the possible existence of local minima, a non-derivative optimization method i.e. a genetic algorithm (GA) is employed to find the optimum design parameters. The method of dynamic penalties is used to satisfy the optimization constraints. To remove the trade-off that exists between the system's power consumption and sensitivity, an energy recovery technique is proposed and implemented. The results show that the optimized system has a low variability of about 5% (0.5 mm) to cycle-to-cycle variations of 50% in the in-cylinder gas force. It is also observed that the optimized VVA with the proposed energy recovery system (ERS) consumes about 58% of the energy used in a conventional cam driven valvetrain.