功率分流混合动力系统发动机停机优化控制

Optimal Control of Engine Shutdown for Power-Split Hybrid System

针对功率分流混合动力系统,为减小e-CVT混合动力模式与纯电动模式切换过程中发动机起停引起的整车纵向冲击度,提出一种发动机停机优化控制策略。首先,基于Matlab/Simulink平台建立功率分流混合动力传动系模型,确定最有利于发动机再次起动的曲轴转角为其最优停机位置;其次,利用动态规划算法设计发动机停机过程最优拖转转速轨迹,并在发动机转速小于200 r/min时协调控制电机与制动器对曲轴转角进行实时动态调节,使得发动机停止在最优目标位置附近;最后,通过仿真和台架试验对所开发的发动机停机优化控制策略进行验证。结果表明,所提出的控制策略可使发动机停止在最优位置±6°范围内,保证了发动机起、停阶段的整车驾驶平顺性。

In order to reduce the longitudinal impact of the vehicle caused by engine start and stop during the mode transition process between e-CVT hybrid mode and pure electric mode,an optimal control strategy of engine shutdown is proposed for the power-split hybrid system.Firstly,the power-split hybrid powertrain model is established based on the Matlab/Simulink platform,and the crankshaft angle which is the most conducive to the restart of engine is determined as the optimal engine stop position.Secondly,the optimal speed trajectory during engine shutdown is designed by the dynamic programming algorithm.When the engine speed is less than 200 r/min,the motor and brake are coordinated to dynamically adjust the crank angle in real time,so that the engine stops near the optimal target position.Finally,the optimal control strategy of engine shutdown is verified by simulation and bench test.The results show that the proposed control strategy can make the engine stop within±6°of the optimal position,ensuring the ride comfort of the vehicle in engine start and stop stages.