液力计算法及DFI-PID下液力缓速器恒力矩制动性能建模与仿真分析
Modeling and Simulation Analysis of Constant Torque Braking for Hydraulic Retarder Based on Hydraulic Calculation Method and DFI-PID

重型车辆在崎岖山路或下长坡行驶时，可以通过控制液力缓速器实现恒力矩制动特性达到稳定行驶的目的。针对液力缓速器能在短时间内产生高制动力现象，提出一套液压控制系统，实现缓速器恒力矩制动性能。这套控制系统通过考虑缓速器充液率、排油阀开度和内腔油压，采用液力计算法解决液力缓速器建模的液力损失问题。并基于整车制动仿真和微分先行增量式PID（DFI-PID）控制策略仿真，建立液力缓速器液压控制联合仿真的模型，得到在较高充液率情况下，排油阀开度和内腔油压的变化规律，最终实现恒力矩制动性能的控制。分析结果表明：在制动过程中，在较高充液率的前提下，需要调节排油阀的开度来保证液力缓速器较高强度的恒力矩功能。
Along rugged mountain roads or downhill roads, heavy-duty vehicles can achieve the purpose of stable driving with the constant torque braking of a hydraulic retarder. Considering the hydraulic retarder can produce high braking torque in a short time, we proposes a hydraulic control system to realize the constant torque braking. Because the hydraulic control system considers the liquid filling rate of the hydraulic retarder, its vent valve opening and cavity pressure, the hydraulic loss of the hydraulic retarder is reduced through hydrodynamic calculation. Besides, based on the vehicle braking and control simulation and the differential forward incremental PID (DFI-PID) simulation, the co-simulation of the control of the hydraulic retarder was carried out, thus obtaining the changes in vent valve opening and cavity pressure at higher liquid filling rate and then realizing the constant torque braking. The analysis results show that, during braking, at higher liquid filling rate, the vent valve opening needs to be adjusted to ensure that the hydraulic retarder has the constant torque braking of high strength