The Longitudinal Dynamic Control Of Vehicle Based On Road Identification

Because of the crucial roles which longitudinal dynamic control systems play in the vehiclepower performance, braking performance and driving safety field, more and more enterprises andscholars have put their attention to these systems researches. But the current longitudinal controlsystems usually adapt the logic threshold control method, unable to get the best controlperformance in different conditions, and the corresponding road identification method can onlyget the graded road friction information, unable to obtain the tire-road friction coefficientaccurately. To these two disadvantages of current longitudinal dynamic control system, this paperproposes the longitudinal dynamic control methods based on road identification. First, to theapplication of traction or braking control system, designed the road identification method thatbased on state observer estimation to calculate the tire-road friction coefficient accurately. Thenin the braking condition, based on the identified road friction coefficient, designing the pressurecontrol strategy with less wheel speed and braking pressure fluctuations. And in the drivingcondition, based on the identified road friction coefficient, designing the integrated controlmethod which including engine, transmission and braking system to improve its drivingperformance.This paper research content is as follows:(1) Built the road identification algorithm. The road recognition method based on thresholdwhich used in current traction or braking control systems is be introduced briefly first. Thendesigned the road identification method based on state observer, including the vehicle statecalculator, tire force observer and recursive least squares estimator. In the tire force observer, twodifferent observers, sliding mode observer and kalman filter observer, had been designedrespectively.(2) Designed driving and braking control strategies. In the braking condition, designed thebraking pressure control methods based on logic threshold or based on sliding mode control. Inthe driving condition, introduced the whole control logic of traction control first, then calculatedthe target speed and vehicle driving flags, designed control methods of engine, transmission andbraking system in different driving condition.(3) Built verification and test platform of algorithm. Introduced the V development processfirst, then based on this development process, built up off-line simulation platform, hardware inthe loop simulation platform and vehicle test and development platform.(4) Off-line simulation and hardware in the loop test of driving condition. The off-line simulation includes starting acceleration on low friction coefficient road, starting acceleration onshifty friction coefficient road, starting acceleration on split friction coefficient road andacceleration during steering. The starting acceleration on split friction coefficient road conditionwas been test and verified on hardware in loop platform.(5) In the braking condition, the control performances of logic threshold method and slidingmode control method have been compared and validated, and the designed road identificationbased on these two control methods have been analyzed by off-line simulation. The braking teston shifty friction coefficient roads had been test in summer and winter respectively, to verify theroad identification method based on state observer.