【作者】 赵凯辉；

【导师】 魏朗；

【作者基本信息】 长安大学 ， 车辆工程， 2010， 博士

【摘要】 随着道路条件日益改善以及行驶车速的不断提高,汽车制动能耗也有了较大增加。有时汽车在一些路段上的控速制动或车辆动力学控制作用常会使汽车产生严重热衰退,同时影响与此相关制动安全性。基于虚拟试验环境可以快速、经济地对数字化汽车仿真模型进行抗热衰退性能或制动安全性检测等方面试验研究。本文在人-车-环境系统框架内,综合考虑制动器摩擦性能热衰退、汽车制动效能变化、制动方向稳定性等方面与不同使用工况条件下相关影响因素之间的耦合作用关系及作用机理,运用不同建模方法进行深入研究,这对于目前复杂道路交通环境中常见肇事运营车辆——大、中型客车及商用车的制动器温度场耦合分析及热衰退摩擦性能确定、整车的抗热衰退性能研究及必要研究平台构建、汽车制动热衰退安全性检测分析与评价等有关研究的方法探索及获取必要关键支持技术具有重要理论和实际意义。针对制动器输出力矩热衰退的多物理过程耦合事实,建立了描述其热-机耦合传热规律的数学模型及三维热-机耦合有限元模型,通过耦合温度场仿真结果与台架试验结果比较验证蹄-鼓副的摩擦系数温度特性。提出了结合摩擦系数温度特性进行制动器热衰退及后续的汽车抗热衰退性能研究思路,根据QC/T 479-1999,编程构建制动器摩擦性能热衰退虚拟试验系统,进行热衰退摩擦性能分析与评价。根据Ⅰ型试验要求,明确参考汽车在循环制动过程中所存在耦合问题的层次、耦合类型、载体、耦合参数等信息。对应用系统集成整合方法建立的耦合制动车辆模型进行道路试验验证；利用验证后的车辆模型,依据GB12676-1999中Ⅰ型试验要求,编程构建循环制动汽车抗热衰退性能虚拟试验系统,对不同因素变化时的制动器热衰退、汽车抗热衰退性能等进行分析探讨,另外还对装用ABS时的循环紧急制动情况也进行了相关的探讨分析。根据Ⅱ型试验要求,明确参考汽车在恒速制动过程中所存在耦合问题的层次、耦合类型、载体、耦合参数等信息。根据前向与后向相结合的系统建模方法及GB12676-1999中Ⅱ型试验要求,编程构建恒速制动汽车抗热衰退性能虚拟试验系统并对不同因素以及发动机档位选择变化时的各制动器热衰退、汽车抗热衰退性能等进行研究。根据循环制动过程与恒速制动过程中汽车在热衰退方面的差异和区别,考虑在汽车下坡行驶过程中利用模糊控速调节策略的循环减速下坡方式,在保证不影响交通顺畅及平均车速不致过大降低的情况下,可较好地提高汽车抗热衰退性能和改善制动器输出力矩稳定性。从方法探索及应用的角度,明确制动热衰退安全性检测的必要性。推导得到热衰退过程中实际制动力分配系数与名义分配系数之间定量关系表达式。根据安全性检测主要内容和方法以及循环与恒速制动汽车抗热衰退性能虚拟试验系统,通过编程构建的汽车制动热衰退安全性检测分析评价系统对在不同影响因素作用下的典型直线制动热衰退过程中有关安全性检测内容进行了检测分析,并做出相应的安全性评价。更多还原

【Abstract】 With the increasing improvment of road and the enhancement velocity of vehicle, the total braking engery consumption has been greater than ever. In some braking cases, such as speed-controlled braking or the action of vehicle dynamic integrated control systems, the serious braking heat-fade of vehicle can be generated. The related braking safety is degraded. In the vitual test environment, the study including vehicle’s antifade performance, braking safety detection and so on can be carried out rapidly and economically by simulating the digitzed vehicle model. Within the framework of HVE(Human Vehicle Environment) system and in light of comprehensive considerations of coupling relationships or coupling mechanism among the affecting factors including brakes’frictional properties, braking effectiveness, directional stabilities and so on, the relative studies are carried out deeply by using various modeling methods. There are more important theoretical and practical significances for method explorations and pivotal supporting technologies of relative studies which are mainly including coupling analysises and determinations of brake temperature field and its frictional performance variation, the studies and corresponding research platform estabilishments of vehicle’s anti-heatfade performance, the safety detections and assessments of braking fade process.In light of coupling reality of multi-physical process of the brake’s output torque variation, the mathematical model and its corresponding 3D thermo-mechanical finite element simulation model which describe heat transfer mechanism and temperature distribution are established. The relationship between temperature and frictional factor of rubbing pairs (RTFFRP) is validated through comparing the simulation results with test data. A new thought is put forward which concerns that the virtual test systems of brake’s frictional performance and subsequent anti-heatfade performance of vehicle is established by using the validated relationship. The virtual test and assessment of brake frictional performance are carried out by using brake virtual bench test system.Based on I type test requirements, the hierarchy, type, carrier and parameters of coupled problem need to be specified. The vehicle dynamic simulation model with brake temeperature variation (VDSMBTV) is validated by comparing the simulation results with the road test results. The virtual cycle braking test system which is based on the I type test requirements of standard GB12676-1999 is used to analyzing the variations of brake heat-fade or vehicle anti-fade performance which are caused by different factors. In addition, the corresponding analysises of emergent 20-cycles braking are carried out for the test vehicle with ABS(anti-lock braking system).Based onⅡtype test requirements, the hierarchy, type, carrier and parameters of coupled problem need to be specified. The corresponding virtual test system is established which is based on the system method combining the forward direction with the backward direction and is accorded with theⅡtype test requirements of standard GB 12676-1999. Then the virtual system is used to analyzing the variations of brake heat-fade or vehicle anti-fade performance which are caused by different factors including various gears in engine braking. On the basis of the differences between cycles braking and downhill braking wih constant velocity, the fuzzy-logical velocity regulations are utilized during driving on the continuous downhill path. The virtual test results indicate that the vehicle’s anti-fade performance and the stability of brake’s output torque are all improved or bettered by this way which ensures the smooth traffic and don’t decelerate the velocity greatly.From the viewpoint of the exploration and application of method, the necessity of braking safety detection need to be specified. The expression of quantitative relationship between nominal braking force distribution coefficient and practical braking force distribution coefficient is derived and received. Based on the main contents or methods of braking safety detection and the corresponding virtual test systems of continuous cycle or downhill braking, the braking safety detection and accessment system are established. The related contents of braking safety detection are carried out under various factor influences and the corresponding safety assessments are put out.更多还原