考虑主、轮缸液压力差异的制动增强控制

Braking Enhancement Control Considering the Difference in Pressure Between the Master Cylinder and the Wheel Cylinder

摘要:

现有电子液压制动系统（EHB）在常规制动工况下均是以主缸液压力传感器为反馈进行液压力控制，而忽略了主、轮缸液压力的差异性对制动控制带来的影响。针对此，首先通过电磁阀测试台架测试了液压控制单元（HCU）增压阀在全开工况下的正、反向的压差流量特性。之后，通过制动测试台架测试了轮缸压力体积（PV）特性，建立了非极限工况下的主、轮缸液压力的动态模型，并通过试验数据验证了模型的准确性。将由上述模型估计的轮缸液压力作为反馈，替换原始的主缸液压力传感器信号，引入到EHB的液压力控制算法中，而并不改变原控制算法。基于经典控制理论，分析了该新控制系统的快速性和稳定性。最后进行了液压力控制的实车试验，结果表明，在相同的目标阶跃工况下，相比于主缸液压力反馈控制，所提出的新控制系统可将轮缸液压力及制动减速度的响应速度提高12 %左右，从而缩短紧急制动工况下的制动距离。此外，由于估算的轮缸液压力比主缸液压力更加平稳且没有超调，新控制系统在快速建压过程中运行更加平稳，显著提升噪声、振动与声振粗糙度（NVH）性能。最后，多工况下的实车试验表明新控制系统是稳定的。

Abstract:

Nowadays， the electro-hydraulic brake system （EHB） adopts the master cylinder pressure sensor as feedback for pressure control under normal braking conditions， while ignoring the difference in pressure between the master and the wheel cylinder. Therefore， first， through the solenoid valve test bench， the forward and reverse throttling characteristic of the inlet valve of the hydraulic control unit （HCU） in the fully open state is tested. After that， the pressure volume （PV） characteristic of the wheel cylinder is tested by the brake test bench. Based on the above， a dynamic model between the pressure of the master cylinder and the wheel cylinder under non-limiting conditions is established， and the accuracy of the model is verified by real test data. The wheel cylinder pressure estimated by the above model rather than the master cylinder pressure sensor is adopted as the feedback and introduced into the master cylinder pressure control algorithm of the EHB without changing the original control algorithm. Based on the classical control theory， the rapidity and stability of the new control system is analyzed. Finally， real vehicle test of pressure control is conducted. The results show that under the same target step condition， the response speed of the wheel cylinder pressure and vehicle deceleration is increased by about 12 %， thereby shortening the braking distance under emergency braking conditions. In addition， since the estimated wheel cylinder pressure is smoother than that of the master cylinder without overshoot， the new control system runs more smoothly during the rapid pressurization process， significantly improving the noise， vibration， and harshness （NVH） performance. Finally， real vehicle tests under multiple conditions indicate that the new control system is stable.