重型载货汽车长下坡制动控制策略

Long Downhill Braking Control Strategy for Heavy-duty Truck

单一制动器温度升高出现制动热衰退现象后,其余制动器热负荷增加会影响整车制动效能,针对此问题提出了基于制动力观测模型的重型载货汽车长大下坡制动控制策略。首先,利用制动鼓温度能够准确表征制动力的特性建立了制动力观测模型;其次,依据整车制动器热衰退演变机理及车辆制动失稳机理,提出了结合散热量、地面附着率、滑移率及轴载的控制策略;然后,为了实现制动力的跟踪控制,建立了基于MPC制动力优化控制模型;为了验证提出的控制策略,建立了基于TruckSim和Matlab联合仿真模型;最后,进行低温制动工况、高温制动工况和基于滑移率的制动控制策略仿真验证。结果表明:低温工况能够抑制制动器温度的快速升高;高温工况能够降低制动器提前出现热衰退的风险,在保证整车制动效能的同时,预留了必要安全措施时间;基于滑移率的控制策略可以保证车辆制动稳定性。结果表明:所提出的控制策略既能相对均衡地控制制动器温度上升速度,又能避免因某一制动器温度快速升高而增加其余制动器热负荷,且保证制动稳定性,从而提高了重型载货汽车长下坡制动安全性。

When a certain brake’s temperature rises and brake thermal degradation occurs,the thermal load increase of other brakes will affect the braking efficiency of entire vehicle.Due to this issue,the long downhill braking control strategy for heavy-duty truck was proposed based on the braking force observation model.First,the braking force observation model was developed by using the brake drum’s characteristic of accurately characterizing the braking force.Second,the control strategy incorporating heat dissipation,ground adhesion rate,slip rate,and axle load was proposed according to the evolution mechanism of brake thermal decay and vehicle brake instability.Then,the optimized control model based on MPC was constructed to accurately track and control the braking force.To realize the proposed control strategy,the joint simulation model by using TruckSim and Matlab software was established.Finally,the proposed control strategy was simulated and validated based on the low-temperature braking condition,high-temperature braking condition and slip rate.The result indicates that the low-temperature braking conditions can suppress the rapid increase of brake’s temperature.The high-temperature braking conditions can reduce the risk of premature thermal decay of brake,which not only guarantees the vehicle braking efficacy,but also increases the safe response time.Furthermore,the braking control strategy based on slip rate can ensure the vehicle braking stability.These results demonstrate that the proposed control strategy not only evenly controls the temperature rising speed of brakes,but also avoids the thermal load of other brakes caused by the rapid temperature increase of single brake.The braking stability is ensured to improve the long downhill braking safety of heavy-duty trucks.