Study On Vehicle Stability Control System Based On GPS

Vehicle stability control (VSC) system could adjust the vehicle driving state in real-timeby the on-board control device, to make the vehicle drive in terms of the wish of drivers. It isa kind of active safe device which kept the vehicle from unstability and was a hot topic of theresearch in vehicle active safety field in the world. The paper studied the key stateparameter estimation and the control algorithm of VSC, combining with the HeilongjiangScience and Technology Fund Project “Vehicle stability control system based on GPS”. It alsohad done the bench test and road test under the various working and road condition.First, it established the8DOF vehicle model,2DOF vehicle model and Dugoffnon-linear tire model used for VSC research. The models were programmed with LabVIEWsoftware. The simulation verified that the vehicle modesl were satisfied the VSC requirementunder various operating condition.For the requirement of VSC key parameter estimation, it presented the vehicle state androad parameter measurement and estimation method based on the two antenna GPS system, interms of the aim of real-time and accuracy. It provided the measurement and estimationalgorithm for COG sideslip angle, COG roll angle, vehicle speed, and so on. It designed thecombination method of GPS and INS based on the two level Kalman filters, and had solvedthe problem of GPS signal lost and low update rate. It presented the road friction coefficientestimation algorithm based on GPS. The test research shown the GPS measurement andestimation had good results and satisfied with the design requirenment of VSC controller.Traditional VSC was referred to yaw stability control, and used differential brake as thecontrol tool. From the point of improving the vehicle active safety, the paper provided theintegral control between the yaw stability and rollover stability, and the control methodincluded the differential brake control (DBC) and active front wheel steer (AFS).It had designed VSC total algorithm structure based on the design idea of the hierarchicalcoordination control. The stability controller consisted of upper and lower level. The upperlevel was the coordination level. It coordinated the various control function, such as yawstability control (YSC), rollover stability control (RSC), ABS and so on. It also determinedthe additional yaw moment for keeping vehicle stability. The lower level was actuation level,and included the control of the brake actuator and the AFS actuator. The coordination controlcontained coordination between the YSC and RSC, and the coordination between the DBCand AFS. It optimized the whole YSC control function.It established the YSC algorithm for the control target of yaw rate and GOC sideslip angle, which controlled the yaw moment by coordination of the DBC and AFS, in order tocorrect the vehicle unstability. For the non-linear and time varying vehicle system, it designedthe DBC controller based on Fuzzy control theory and te AFS controller based on slidingmode control theory. It presented the coordination method of DBC and AFS based on β~β&phase plane. It designed the sliding mode varying structure rollover stability controller, andtook the lateral load transfer ratio (LTR) as the control variable. The controller performedRSC by adjusting brake pressure hydraulically. It designed the YSC and RSC coordinationcontrol algorithm. The yaw moment and reducing speed brake force was determined by YSCmodule and RSC module firstly, and then distributed them to each brake wheel, to realize thecoordination of YSC and RSC.The virtual simulation platform of VSC was established based on the vehicle dynamicsmodel and the control algorithm, by means of CarSim and MATLAB/Simulink co-simulationtechnology. The simulation are performed on the platform under various road frictioncondition and different test condition such as double lane change, fishhook steering test, andso on. The VSC algorithms were verified. The results proved that the virtual simulationplatform could finish the simulation and test for VSC algorithms very well. The VSCcontroller could recognize the vehicle driving state, and coordinated DBC subsystem and AFSsubsystem. The controller could solve the confliction of the subsystem integral control andmake full use of the subsystem ability. The controller could prevent from vehicle rollover andyaw unstability and improve vehicle driving stability.The VSC hardware-in-loop (HIL) test platform based on LabVIEW was designed andestablished on the foundation of virtual simulation. The platform included the benches,sensors, actuators, real-time control platform, signal collecting system and software, etc... TheHIL test system simulated the vehicle driving environment by software, and the vehicle yawand roll state were were calculated under the input signals. The DBC and AFS were finishedby the hardware method. The test results shown that the controller could judge the yaw androllover state of the vehicle, and output the control voltage in real time. The brake systemcould output the force accurately and quickly. The AFS could adjust front wheel angle. Thecontroller could limit the dynamic yaw and LTR in safe range. The control algorithm havegood robust for the vehicle structure parameter and handle parameter change.Finally, the road tests were performed on self-developed on-board platform. The resultsproved that the VSC algorithm could improve the vehicle safety, and enhance vehicle drivingability on the curve. The control algorithm have good real time and is satisfied therequirement of actual application.