Integrated Longitudinal And Lateral Motion Control Of Distributed Electric Vehicles

The movement of vehicle on the road can be divided into longitudinal motion andlateral motion. Integrated longitudinal and lateral motion control system can improvethe vehicle handling stability and energy efficiency by controlling the drive/brakesystem and the active steering system. The existing researches mainly focus on theconventional ICE (Internal Combustion Engine) vehicles and centralized EV (ElectricVehicles). For the integrated longitudinal and lateral motion control of distributed EV,there are some problems in the existing researches, such as the control system isincomplete, the accuracy and robustness of the vehicle state estimation is not highenough, the performance index of tire force distribution is not optimal, and the accuracyof inverse tire model is limited. Considering these problems, for the distributed EVequipped with active front steering system, an integrated longitudinal and lateral motioncontrol system is proposed in order to improve the handling stability and energyefficiency. The key technologies, including vehicle state estimation, optimum tire forcedistribution and tire force control, are studied in this dissertation.The state estimator is established in order to estimate some key vehicle stateswhich are hard to measure directly, such as longitudinal velocity and vehicle sideslipangle. Combining the signals from GPS and INS, and integrating the kinematic anddynamic estimation method, real-time and accurate estimation result of longitudinalvelocity and vehicle sideslip angle can be obtained.The upper controller is used for the tire force distribution. Longitudinal and lateraltire forces are allocated based on the optimization of tire workload and tire energydissipation respectively. A dynamic regulation method between these two performanceindexes is proposed in order to improve the vehicle handling stability and energyefficiency.The lower controller is built for the tire force control. The desired tire forces aretransformed to tire slip ratio and sideslip angle, which are easier to measure and control.Meanwhile, the longitudinal force and lateral force are decoupled. A sliding modecontroller and a feedforward/feedback combined controller are established for thecontrol of the tire slip ratio and sideslip angle respectively.To verify the effectiveness of the integrated longitudinal and lateral motion control system of distributed EV, simulation and field test in different operating conditions arecarried out. The simulation and field test results show that the coordinated controlsystem can improve the vehicle handling stability and energy efficiency effectively.