Vehicle Stability Control System Research Based On Side-slip Angle Phase

Vehicle Stability Control System Research Based on Side-slip Angle PhaseVehicle Electronic Stability Control system (ESC) is widely accepted as an active safetycontrol system, which is able to significantly improve the vehicle handling stability, and ESCsystem is in the stage of popularization in China. Due to the stability analysis, control andevaluation problems in the research of vehicle stability control system and heavy rely on theforeign technology in the application of ESC system, this thesis combined with the researchof National High-tech R&D Program of China (863Program), using the improvement ofindependent research and development capabilities of ESC system as its starting point, andone domestic A0type car as its research object, based on the objective of side-slip anglestability analysis, control and evaluation, to systematically study the vehicle stability control.Based on ESC system development process, the systematical research of vehicle stabilitycontrol is significantly meaningful to the richness of vehicle stability theoretical system andimprovement of road transportation safety as a result of the popularization of ECS in China.By building ESC system software simulation environment, constructing ESC system HiLtest bed, and developing system test vehicle, this thesis has realized V pattern developmentprocess of software simulation—HiL test—real vehicle test, built the V pattern researchplatform of ESC system and provided technical scheme to the development of ESC systemand platform to the systematical research of vehicle stability control system.Based on theESC system V pattern platform, this thesis did the following research on the fundamentalproblems in the development of ESC system: the research on the controller and executorhardware, control logic and the software framework of the algorithm, integration andoptimization of ESC system. Besides, this thesis also did further studies on the analysis ofvehicle stability, control and evaluation fields as follows:(1) Research on stability analysis and control method based on side-slip angle phase: bystudying vehicle dynamic model and UniTire model, this thesis built the vehicle dynamicanalysis system, studied the influence of side-slip angle on vehicle stability and the changingrules of the boundary of stability area in the side-slip angle phase plane as the change ofvehicle speed and road friction coefficient, and proposed the method of determining thestable boundary of side-slip angle phase plane.(2) Research on the estimation of vehicle state and stability control strategy: since someimportant vehicle state parameters cannot be measured in the ESC system, this thesisadopted sliding mode observer to estimate the side-slip angle, combined the wheelspeed method with slope method to estimate vehicle speed, combined ABS logic road recognizingwith friction ellipse method to estimate road friction coefficient. Then the ESC controlstragedy is propssed based on the vehicle state estimation and the determining method of thestable boundary of side-slip angle phase plane. Combined wuth the control stragedy based onyaw rate, the yaw moment for stability control is decided and verified by fuzzy logicaccording to the influence of velocity and road friction coefficient. The wheel cylinderpressure distribution method is proposed to provide proper yaw moment.(3) Research on the executive mechanism and pressure estimation of wheel cylinder: bystudying the HCU principle and structure in ESC system, structure modeling of HCU wasachieved. Analysis of sensitivity of some relative parameters in HCU model can guide thestudy of HCU’s characteristics. By studying the HCU’s characteristics by V pattern researchplatform of ESC system and parametric modeling of HCU based on HCU’s stable pressureregulating property, this thesis proposed the open-loop estimation method of wheel cylinderpressure. And then, by utilizing the pressure state gained from the estimation method, theHCU’s closed-loop control method by ESC system was put forward. Moreover, the vehiclestability controlled by yaw moment was realized by distributing the pressure of wheelcylinder.(4) Research on analysis methods of ESC system control strategy and real vehicle tests:given the influence of ESC system on the overall performance of vehicle, and based on thechoice of driver-vehicle-road closed-loop objective evaluation indexes, by augmenting theindexes that represent control system performance, such as the indexes that control theenergy requirement and time requirement of the system, the ESC system control strategyanalysis method was proposed, which can evaluate the overall performance of control logicand direct the optimization and determining of the control logic parameters in real vehicletests. By validating with the real vehicle tests, the ESC system and the proposed stabilitycontrol stragedy in this thesis are able to effectively improve the vehicle stability.Furthermore, by studying the vehicle stability control system of side-slip angle, the researchsystem of vehicle stability after introducing the control system was enriched.Major Innovations of the Dissertation:(1) The method of determining the boundary of phase plane in vehicle stability controlwas proposed, by studying the change rules of stable boundary of phase plane of side-slipangle as the variety of vehicle speed and friction coefficient;(2) The stability control strategy of phase of side-slip angle was proposed by estimatingside-slip angle with sliding mode observer and determining the stable boundary. Based onco-restraining the slip angle and its change ratio, the vehicle stability control was achievedby distributing the yaw moment;(3) Based on the stable pressure regulation property of the HCU, the open-loop estimation method of wheel cylinder pressure was proposed. According to the estimatedpressure state information, ESC system is able to control the vehicle yaw stability byclosed-loop controlling HCU.