Study On The Brake's Heat-fade Performance And Corresponding Braking Safety Detection Of Vehicle

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 onâ…¡type 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 theâ…¡type 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.