基于改进NSGA-Ⅱ算法的发动机活塞机构优化设计

Optimal Design of Engine Piston Mechanism Based on Imporoved NSGA-Ⅱ

为提高发动机活塞机构的运动性能,提出了以最小跟踪误差和传动角与直角的偏差最小为优化目标,建立发动机活塞机构多目标优化模型,引入NSGA-Ⅱ算法对活塞机构进行多目标优化。为提高NSGA-Ⅱ算法的种群的多样性和搜索能力,对交叉算子和变异算子进行改进,应用NSGA-Ⅱ算法与改进算法对发动机活塞机构优化问题进行求解,分别得到各自的Pareto解集,并通过逼近理想解排序法选出最优解进行对比。通过实验对比表明,改进算法的Pareto解集分别更均匀、收敛速度快、跟踪误差更小,能为发动机活塞机构的优化设计提供参考依据。

In order to improve the motion performance of engine piston mechanism, both the mechanism＇s tracking error and deviation of its transmission angle from 90° are presented, the multi-objective engine piston mechanism optimization model is established, the non--dominated sorting genetic algorithm-Ⅱ （NSGA-Ⅱ ） is used to the multi-objective optimization of engine piston mechanism. To enhance the population diversity and the search ability ofNSGA-Ⅱ,the crossover operator and mutation operator are improved. The NSGA- Ⅱ algorithm and improved algorithm are used for solving the optimization problem of engine piston mechanism, two set of Pareto solutions are obtained respectively. The comparison of optimal solutions which selected from Pareto solution set by similarity to ideal solution. The comparison shows that the proposed algorithm distinctly outperforms NSGA-Ⅱ the uniform distribution of Pareto front, the rate of convergenee and tracking error, it can provide a reference basis for the optimization design of the engine piston institutions.