Study On Coordinated Control Strategy Of Active Front Steering And Electronic Stability Control For Vehicle

Both AFS and ESC have an important role in improving the stability of the vehicle.But there are differences in characteristic of AFS and ESC, so there is interference in theprocess of control. To resolve this question, and make best of the advantage of AFS andESC to further improve the stability of the vehicle.At present, the distributed structurewhich is low in integration is mostly used to study the coordination control of electronicsystem at home,this kind of control have little effect in improving the performance of thevehicle. The integrated structure which is high in integration is mostly used to study thecoordination control of electronic system at abroad, this kind of control is too complex andconformity ability is low, even if hierarchical structure is used in some studies, few studiesuse the dynamic control according to the state of the vehicle. the paper study on thecoordination control strategy.The main contents are as follows:1) Analysis of the characteristics of AFS and ESCThe structure, the principle, the effect on the stability of AFS and ESC and theeffective area that AFS and ESC work are analyzed to lay a theoretical foundation for thestrategy of coordination control of AFS and ESC.2) The division of the stability regionDue to the stability domain boundaries can be described by the non-stable equilibriumpoint of the phase plane quantitatively. The control region is divided based on the phaseplane. The stability region is different with the change of front wheel angle, vehicle speed,and road adhesion coefficient, since the kinetic equation of the phase plane is the equationof front wheel angle, vehicle speed, and road adhesion coefficient. The vehicle condition isdivided into eighteen kinds of conditions, the state of the vehicle can be cooresponded to atypical condition and the genetic algorithms is used to determine its non-stable equilibriumpoints which determine the stability region boundary.3) The division of the coordination control area of AFS and ESCThe stability region boundary is translated inward and outward to get the coordinationcontrol area. the coordination control area is affected by the vehicle speed and the front wheel angle, so the Fuzzy control which has good robustness is applied, and the vehiclespeed and the front wheel angle are made as the inputs, and the control coefficients whichdetermine the offset are made as outputs to divide the coordination control area.4) The determine of the target yaw momentSince the sliding mode control theory has good robustness on system parameters andoutside interference, so the sliding mode control theory is applied to get the target yawmoment.5) The distribution of the target yaw momentThe workload of AFS and ESC is different when the state of the vehicle is different.The area which the vehicle locates is determined based on the principle of division of theregion to distribute the workload of AFS and ESC.In order to validate the validity and advantage of the coordinated control strategy ofAFS and ESC, simulation platform on which the off-line simulation is carried out is built inMATLAB/SIMULINK environment. The simulation results show that this control strategyimproved the stability of the vehicle effectively.The innovation of this paper is as follows:1) The speed, the front wheel angle and the road friction coefficient are made as theinfluencing factor to recognize the dynamic coordination control stable region to enhancethe effect of the coordinated control.2) The genetic optimization algorithm is applied to resolve the nonlinear system.3）The speed and the front wheel angle which effect the division of the coordinationcontrol region are considered, The Fuzzy control which has good robustness is applied todivide the coordination control region to enhance the effect of the coordinated control.