Investigation To Vehicle Lateral Stability Using Active Suspension System

Handling and stability of vehicles is the most complex performance of vehicles. Itmainly refers to the car’s ability to follow the driver’s instructions and the ability to resistinterference.i.e. maneuverability and stability. With the rapid development of China’sautomobile industry, car ownership Increased substantially. The relationship of human-vehicle-road is becoming more and more complex. At the same time, handling and stabilityof vehicles is one of important content of automotive active safety. These groundsabove-mentioned accelerate the pace of research of handling and stability of vehicles, so thework in this paper is meaningful and has profound background.The root cause for vehicle’s instability in the lateral direction is at the limit of adhesionof wheel. Load transfer fiercely not only between the front tire and rear tire but also betweenthe left tire and right tire, when car moving on curve road. Load transferring will lead tirecannot provide sufficient lateral force for lateral movement of car.This article begins from the vehicle dynamics model of automobile. firstly, anautomotive vehicle model has been established using virtual prototyping technology, which isconsist of front and rear Suspensions, steer mechanism, chassis systems,tire model and roadmodel which is relevant to car model. Components and their assembly relationships wereacquired from three-dimensional software. So the model has the same physical parameterssuch as mass and moment of inertia as the actual car. On this basis, the moving relationshipbetween the various components has been examined and then those components have beenassembled up. lastly, vehicle model has been verified,and the result showed that there are27degrees,namely,6degrees for body of car,4degrees for4wheel’s rotation,4degrees forlower wishbone of front and rear suspension,4degrees for up wishbone of front and rearsuspension,4degrees for4MR dampers,4degrees for mounts of MR damper. In order tocontrol strategy’s parameters, linear model of two degrees of freedom has been established tofigure out the driver intent.Sprung mass will roll about the rolling center when car moving on the curve road.thismay affect not only comfort but also the load on tires. This paper systematically analyzes theimpact of sprung mass rolling on load of tires, and then quantitatively obtained relationshipbetween the size of load transfer and roll stiffness of suspension. The size of suspension’srolling stiffness is relative to stiffness of the suspension. So we can effective change the loadtransfer by changing the stiffness of suspension when sprung mass rolling. However, thedamper characteristics will affect stiffness of suspension, currently, semi-active suspensionwhose damp is Variable, has been applied to a number of cars. This paper established a certain type of mathematical model of magnetorheological suspension by using of Bouc-wenmodel. Suspension characteristics can be indirectly affected by controlling current. Aftersystematic studying of the automobile lateral stability theory, the corresponding controlstrategy has been put forward. On this basis two fuzzy controllers has been set up, one is foradditional yaw moment controlling,and the other is for semi-active suspension controlling,both of them considered yaw rate and sideslip angle and the error of them as input,and theirout put are respective additional yaw moment and current. Finally, simulation of semi-activesuspension and automotive’s lateral stability has been done via virtual prototype analysissoftware ADAMS and MATLAB. To illustrate the control strategy and methods to beeffective, typical test such as step, the double lane change, fishhook has been done. Theresults show that, at variety of working conditions, vehicle without any control shows theworst stability. While, vehicle with DYC control whose stability has been improved to acertain extent, but it still cannot move like expectation, however, vehicle with activesuspension control male the actual trajectory curve and stability parameters be nearly thesame.