The Research On Phase Plane Vehicle Coordination Control Of Active Front Steering And Active Braking

With the improvement of people’s living standard and the rapid development ofautomobile technology, people put forward to higher and higher requirements for the safetyof the car. In the recent decades, the vehicle chassis stability control system is during a rapiddevelopment, coordinated control system also arises at the historic moment. Eachsubsystem has its own independent functions. If we simply install them together, they willnot promote each other, instead, they will inevitably occur coupling and cause the conflictand interference between subsystems. Both active braking control and active steeringcontrol can control the vehicle’s lateral stability, but the interference is inevitable, thisphenomenon may lead to various subsystems work frequently, thus reduce the function ofthe vehicle system and cannot assure reliability. Through the coordinated chassis control thevehicle can eliminate the interaction in system dynamics and avoid the unnecessaryinfluence between each subsystem. Chassis coordinated control can also optimize thevehicle driving performance, achieve better than the results that two subsystems simplywork together.In this paper a sedan active braking and active steering coordinate control based onphase plane is studied. The main contents of this paper include:（1） On the basis of model assumptions, set up nonlinear tire model and nonlineartwo degree of freedom model based on side slip angle and yaw rate. Establishedthe vehicle state observer and use it to solve the vehicle’s speed and tire-roadfriction coefficient and so on. Designed the whole vehicle control model andsolved the ideal yaw rate and side slip angle.（2） Based on phase plane, completed the design of active braking and active steering coordinate controller. Explored the relationship between the stabilityboundary and the vehicle speed, road adhesion coefficient and front wheel angle.Then using the sliding-model control theory calculated the required yaw momentof active braking system and the required angle of active front steering system.Selected the-phase plane and divided into three areas. In the inside controlregion it is controlled by active steering along, in the outer region it is controlledby active braking along, in the middle region it is control by both of them. Theywork coordinated and take full advantages of each other. The intercept of thecoordinated control area boundary is optimized by particle swarm optimization. Inthe coordination control area, the distribution of the s-shaped membership functionis used to determine the distribution coefficient. Analyzed the efficient rules todistribute the required torque to specific wheel in the process of active braking.（3） Introduced the vehicle offline simulation commonly used simulation softwareMATLAB, CarSim and the reason of selection of four typical load cases. UsingMATLAB co-simulation with CarSim in four different conditions to verify theeffectiveness of the algorithm in this paper.