Abstract:

A large number of researches have been carried out in China on speed ratio optimization of the transmission system, such as genetic algorithm, particle swarm optimization algorithm and PARETO optimal solution. The principle of gear ratio optimization is to evaluate the power and economy of the system under different gear ratio combinations, and then select the gear ratio combination with the best performance. When the gear ratio combination changes, the system shift pattern will change, and it is necessary to recalculate the shift pattern for each gear ratio combination, which adds complexity to the entire optimization calculation. The existing gear ratio optimization methods do not consider the changes in gear shifting patterns under different gear ratio combinations, or simplify them to varying degrees, which to some extent affects the calculation accuracy. This poses challenges to the implementation of various optimization algorithms.

Therefore, targeted solutions are proposed to address the issue. Firstly, a speed ratio optimization method for power coupling devices based on the exhaustive method is proposed to address the situation where the gear ratio optimization is prone to falling into local optima and the shifting patterns may change under different gear ratio combinations. Then, the results obtained through this algorithm cover all gear ratio combinations and can intuitively reflect the changes in fuel consumption and power performance under different gear ratio combinations. This method can ensure the globally optimal calculation results, and can quickly select the required speed ratio combination based on the calculation results when the economic and dynamic requirements change. Besides, in response to the problem of high computational complexity in the exhaustive method, biased proportional constraints, impact constraints and dynamic constraints are added to the speed ratio combination based on the previous speed ratio optimization, reducing the search range of speed ratios. In the calculation of gear shifting patterns under different gear ratios, multi threaded technology is used to optimize the calculation, keeping the calculation time within a reasonable range.

The final result shows that at low speeds, with medium to low valve openings, the optimized speed ratio of the operating point of the car engine increases, and the economy is effectively improved. In addition, the results before and after the optimization are obtained through simulation of the economic and power shift patterns. Through data analysis, it can be seen that although the power performance of the optimized vehicle decreases by 11.15%, the economic efficiency increases by 4.44%, which fails to validate the rationality of this method.