N次谐波凸轮的随机搜索法优化设计

为解决发动机配气机构N次谐波凸轮设计问题中设计参数多、设计参数与控制指标之间没有确定规律的问题,提出了采用点控加段控策略减少设计参数,并应用随机搜索法求解的优化设计方法.计算结果表明,随机搜索法对此类问题具有非常好的适应性.对称型N次谐波凸轮的最佳负加速段宽度的变化范围非常小,采用负加速度段宽度点控条件可以确保更有效地控制负加速度段的段控目标.负加速度段气门惯性力-弹簧力匹配和等曲率半径段控条件的联合使用可以取得不过分降低飞脱转速情况下,增进凸轮桃尖区润滑特性和改善凸轮抗疲劳性能的综合效果.

Nth-degree harmonic cam optimal design with random search technique

The paper presents a modified model to design an Nth-degree harmonic cam profile,with the point control strategy plus section control strategy to reduce its design parameters.An optimal random search technique was adopted to solve the Nth-degree harmonic cam design problem whose control indexes and design parameters has no certain correlations.It is proved that the random search method is most adaptive to solve the problem.Analytical results show that the range of length of the negative acceleration section is extremely small,and point control of that makes spring-inertia force match characteristics and constant curvature radius control in the corresponding section more effectively.As a result, the lifter-cam lubrication and fatigue-resistant properties are improved without lowering the valve train jump-up-camshaft-speed.