混合动力汽车下坡辅助控制方法

Downhill Assist Control Method for Hybrid Electric Vehicle

为减轻混合动力汽车(Hybrid electric vehicle,HEV)下坡过程中驾驶员的驾驶负担,提高车辆运行的安全性和经济性,提出一种满足驾驶员主观意图、确保下坡安全性和提高制动能量回收性能的下坡辅助控制(Down-hill assist control,DAC)方法。上层根据车辆下坡行驶过程中安全性需求,以满足驾驶员的主观驾驶意图为原则,提出下坡辅助控制启动和退出策略,并制定辅助控制的目标。中层依据辅助控制目标,利用比例积分微分(Proportional integral derivative,PID)方法计算总需求制动转矩,根据总制动转矩、各制动系统的制动能力和制动原理,提出电机单独制动、电机-发动机联合制动及电机-发动机-液压联合制动的转矩分配策略。下层针对电机、发动机和液压系统响应特性的不同,提出发动机接入过程的动态协调控制策略与液压转矩变化过程的动态协调控制策略。进行实车验证,结果表明该方法在减轻驾驶员的操纵负担、提高混合动力汽车下坡路段安全性的同时,能降低油耗,并改善舒适性。

To alleviate the burden for driving a hybrid electric vehicle（HEV） during downhill, a downhill assistant hierarchical control technique is presented. It can satisfy the driver＇s maneuver intention, meanwhile, improve the performance of braking energy regeneration. According to driver＇s intention and safety requirements, in the upper controller, start and exit strategies are put forward, and the goal of the downhill assistant control is set. Based on the control object, the total demanded torque is computed by proportional integral derivative（PID） in the middle controller, which is distributed to different braking systems according to the braking torque distribution strategy. This strategy is developed after considering brake capacity and principle of each of the braking systems, which can be divided as several forms including motor, motor-engine joint and motor-engine-hydraulic joint brake. Focusing on difference of response characteristics of each module, the lower controller proposes dynamic coordination control strategies for the access of engine and changing of hydraulic torque. A vehicle test is carried out to verify the control method. The results show that while reducing the burden of drivers and enhancing the downhill safety performance of HEV, the method can reduce fuel consumption and improve comfort.