基于最优控制理论的电动汽车机械式自动变速器换档控制

Shifting control of automatic mechanical transmissions for electric vehicles based on optimal control theory

提出了一种用于电动汽车的动力保持型二档机械式自动变速器,该变速器主要由行星齿轮系统、离心摩擦离合器、带式制动器构成,可以在两个档位之间进行无缝切换。解决了传统机械式自动变速器(AMT)在换档过程中存在的动力中断问题。建立了电动汽车动力传动系统的动力学模型,采用基于动态规划和带约束的凸优化的变速器换档过程的最优控制方法,以冲击度和滑摩功为评价指标,求解换档过程的最优控制量,实现变速器的最优换档控制。通过动力学建模与仿真,对基于最优控制的变速器换档控制进行分析和优化,对普通分段控制方法和最优控制方法进行对比。仿真结果表明:该最优控制方法能够有效提高电动汽车的换档舒适性,并在保证动力性能不降低的前提下减少离合器和带式制动器的摩擦损失。

A two-speed,automatic mechanical transmission（AMT）is developed for electric vehicles with a planetary gear system,a centrifugal clutch and a belt brake. The transmission shifts seamlessly between the two gears to eliminate the power interruption problem during gear shifting in conventional AMT.The electric vehicle driveline is modeled to get the optimal control method using dynamic programming and convex optimization.The optimal control variables and optimal control system minimize vehicle jerk and frictional losses.A normal sectional control method is also used during gear shifting for comparison in simulations.The simulations indicate that the optimal control method significantly improves the gear shift comfort while maintaining the dynamic performance as well as vehicle acceleration with decreases of frictional losses in the clutch and brake.