Study On Fault Tolerant Control Of X-by-wire Electric Vehicle With Four Wheels Independent Control

Currently faced with serious problems such as roar demand in traffic service, increasingconsumption of fossil fuels, serious environmental pollution and greenhouse effect caused bymassive usage of internal combustion engine vehicles, governments, automotive companiesand research institutes all around the world are searching solutions to sustainabletransportation in21st century. Electric vehicles which use secondary energy–electricity arereceiving rising attention. The X-by-Wire electric vehicle with four wheels independentcontrol (4WIC EV) is a new type of electric vehicle in system configuration which is basedon the X-by-Wire technology and can control the drive, steer and brake movement in everywheel corner. Compared with traditional vehicles,4WIC EV has more degrees of freedom inactuator control, so it has many driving mode improving mobility in the crowded city; basedon the characteristics that each wheel can be independently controlled, driving, braking andsteering of the vehicle can be controlled integratedly so as to optimize vehicle dynamics andimprove vehicle handling and stability. More importantly, based on actuator redundancy in4WIC EV the reconfigurable control allocation method in over-actuated system can beapplied to improving post-fault vehicle stability and safety. In summary,4WIC EV has apromising electric vehicle configuration, is the excellent platform for the study of advancedvehicle dynamics control method, and represents the trend of the future vehicles.Based on the programs “Research on Chassis Control Method and Key Technology forX-by-Wire Automobile”(Grant No.50775096) and “Research on Steer-by-Wire SystemControl Joystick and Its Bilateral Control Method”(Grant No.51105165) supported byNational Natural Science Foundation of China and “Study on State Estimation and RoadCondition Identification of4WID/4WIS Electric Vehicles”(Grant No.20121088) supported by Graduate Innovation Fund of Jilin University, the actuator fault tolerant control problemof4WIC EV has been studied aiming to maximize vehicle stability margin after the failuresof actuators. For the above research objectives, main contents of this thesis are as follows:(1) Vehicle Dynamics Modeling for4WIC EVAn11DOF vehicle dynamic model for4WIC EV has been established. Based on the vehiclebody3DOF planar motion model, driving/braking system model, steering systems and tiremodel have been built. Compared with CarSim vehicle model in several simulationexperiments, results have shown that the established model can characterize the couplingrelationships between vehicle longitudinal, lateral, and yaw motion. So the dynamic modelfor4WIC EV can be used for development for the fault tolerant control algorithms.(2) Study on Actuator Fault Tolerant Control for4WIC EVHierarchical control structure based on control allocation has been employed to design thealgorithm and consist of upper motion controller and lower reconfigurable control allocator.The motion controller adopts the model predictive control theory to optimize the vehiclemotion; the reconfigurable control allocator employs the reconfigurable control allocationmethod using designed re-allocation laws to ensure vehicle performance and safety.(3) Experimental Verification for Fault Tolerant Control AlgorithmIn order to validate fault tolerant control algorithms under a variety of actuator failuresituations, firstly simulation experiments have been conducted in3conditions of differentfault types, road adhesion, the steering operation and driving speed. Then the robustness ofthe algorithm is studied under the influence of the noise, in order to against noise effects anoise mitigation scheme is proposed. Finally the effectiveness of the fault tolerant controlalgorithm has been validated on the EV platform under several conditions.