多联轴货车纵向连通空气悬架轴荷平衡机理与控制研究

Longitudinal-connected air suspension system is significant for the improvement of driving stability and safety of multi-axle heavy truck. However, the lack of research in mechanism, optimization and control of load-sharing of multi-axle air suspension are becoming bottlenecks of its performance optimization, popularization and application. The main focus of the proposed research is the optimization of load-sharing, roll stability and ride comfort of multi-axle heavy trucks with longitudinal-connected electronically controlled air suspension (ECAS) under various driving scenarioes. There are six main themes within the proposed research project. The first theme is to develop the high-fidelity three-dimensional road excitation models of smooth pavement, rough pavement and bump/pothole based on data acquisition, Wiener - Khinchin theorem and fast fourier transform (FFT). In the second theme, the nonlinear mathematic model of longitudinal-connected multi-axle air suspension is to be developed using fluid mechanics, thermodynamics and integrated to the mathematical vehicle model. The third theme is to discuss the load-sharing mechanism and load-sharing-based optimization method of key suspension structrual parameters based on both field test and theories such as singularity theory, modified genetic algorithm (MGA), etc. In the fourth theme, the structure of the integrated control scheme of air pressure inside air bags, damping coefficent of each damper and orifice area of connectors is to be designed based on the analysis of coupling characteristics between suspension forces and motion state of whole vehicle. As the posture and driving condition are to be determined using extended kalman filter (EKF) and fuzzy neural network (FNN), the parameters of the integrated control are to be calculated based on simulated annealing algorithm (SAA). The fifth theme is to develop a high-fidelity vehicle-road virtual prototype (VP) model with Trucksim/Simulink for verification and modification of the integrated control scheme. Through the investigation of the project, the load-sharing mechanism and the effect of coordinated mode among suspension forces within an axle group on driving safety will be revealed, which will be useful in structrual design and control of longitudinal-connected ECAS for multi-axle heavy trucks based on driving safety.

纵向连通空气悬架对全面提升多联轴重型货车行驶的稳定性、安全性有重要作用，但纵向连通空气悬架轴荷平衡机理、轴荷平衡能力优化与控制理论的匮乏成为制约其性能提升和推广应用的重要瓶颈。拟考虑纵向连通多联轴空气悬架气囊连接管中气体传输的一维非定常流特性，基于流体力学、热力学完善各气囊非线性耦合动力学模型构建理论；采用奇异性理论、基于混合交叉和维变异的遗传算法等理论分析与实车试验结合的方式，探索纵向连通多联轴空气悬架轴荷平衡机理和基于轴荷平衡的悬架关键结构参数优化方法；依据轴组内各悬架力与整车运动状态动态耦合特性的分析，设计面向综合行驶安全的集成各气囊压强、减振器阻尼、气囊连接管节流孔面积的纵向连通多联轴ECAS快慢响应分步解耦协调控制策略。通过项目的研究，可获得纵向连通多联轴空气悬架轴荷平衡机理及各轴悬架力协调方式对行驶安全影响规律的新认识，为多联轴重型货车行驶安全优化提供新的思路。

纵向连通空气悬架对全面提升多联轴重型货车行驶的稳定性、安全性有重要作用，但纵向连通空气悬架轴荷平衡机理、轴荷平衡能力优化与控制理论的匮乏成为制约其性能提升和推广应用的重要瓶颈。本项目考虑纵向连通多联轴空气悬架气囊连接管中气体传输的一维非定常流特性，基于流体力学、热力学，提出了纵向连通空气悬架模型的构建方法，实车测试结果表明，模型的DLSC、DLC误差为3.3%-21.2%，且模型、试验结果的变化趋势一致。归纳、总结了外界参数（路面等级、车速、载荷等）、悬架结构参数（连接管半径、空气管道半径、初始气压等）对纵向连通多联轴空气悬架轴荷平衡性能的影响机制，得到了纵向连通多联轴空气悬架系统轴荷平衡能力稳定时悬架结构关键设计参数设计范围。为保证车速、载荷、路面不平度变化时，纵向连通ECAS系统的轴荷平衡、平顺性综合性能最优，提出一种新颖的多目标粒子群内外层嵌套优化（DL-MOPSO），其中，内层MOPSO算法用于计算车速、载荷、路面不平度变化时多目标优化函数的变化范围，外层MOPSO算法的适应度函数为目标函数的中值和变化范围之和，通过比较各组设计变量对应的适应度函数值，可不断更新外部归档集中的气囊连接管内径、空气管道内径Pareto解集，并从中选择最优解。在纵向连通ECAS几何参数优化的基础上，基于LQG控制提出了一种ECAS刚度与连续可变阻尼的新型匹配方法，进一步优化整车的综合性能。依据车身弹跳频率的设计要求，确定了满载时牵引车ECAS合适的高度变化范围，根据载荷、行驶速度、路面不平度得到了悬架目标高度的控制算法；考虑连续可变的半主动阻尼的非线性特性，基于LQG控制理论，通过最优总作动力减去空气弹簧力，得到半主动减震器的理想阻尼力，应用该方法后，牵引车的平顺性、轴荷平衡能力显著优于原传统ECAS牵引车。通过项目的研究，得到了纵向连通多联轴空气悬架轴荷平衡机理及气囊刚度、半主动减震器协调方式对行驶安全影响规律的新认识，为多联轴重型货车行驶安全优化提供了新的思路。