Fault Diagnosis Of The Brake-by-wire Actuators Sensors And Coordination Control Of Vehicle Stability

Brake-by-wire system has the characteristic of small capacity, rapid response, highbrake efficiency, and easy to arrange. At the same time brake-by-wire system is anelectro-mechanical system that includs the controllers, communication networks, sensors,actuators, and other components. As the electro-mechanical system is so complicated, it’snecessary to have a fault diagnosis system to supervise the sensors of the brake-by-wiresystem actuators, design the fault tolerant structure of the electronic components, and had aresearch about the stability control of the vehicle after the failure of the brake-by-wiresystem actuators, which is significant import.This paper’s study was based on a protype of a brake-by-wire light vehicle.Fristly,designed the fault tolerant control system of the sensors of the brake pedal, communicationnetwork of the brake-by-wire system, vehicle dynamic control ECU, and batterymanagement system; secondly, a simulation platform of the fault diagnosis system of thebrake-by-wire system actuator sensors and vehicle stability control system was set up; thirdly,put forward the over structure of the fault diagnosis of the brake-by-wire system actuator andvehicle dynamic control, applied the support vector machine(SVM) to fault diagnosis of thebrake-by-wire system actuator and adopt the method of control allocation to the vehiclestability control on the condition of actuator failure; at last, put up theHardware-in-Loop(HIL) test platform, and took the HIL experiment to inspect and verify theeffectiveness of the control algorithm.The main content of the article including:1.Set up the simulation platform of the fault diagnosis of sensors of thebrake-by-wire system actuator and coordination control of vehicle stability.In order to put up an accurate simulation model to inspect and verify the algorithm ofthe fault diagnosis of the sensors and vehicle stability control, the math model of thebrake-by-wire system actuator, active front steering (AFS) and the vehicle dynamic model in the form of simulink were set up.Brake-by-wire system model includs the brushless DCmotor module, transmission module and caliper module.2. Computer simulation study of fault diagnosis of brake-by-wire system actuatorand coordination control of vehicle stability.Firstly, take the advantage of support vector regression(SVR) to build the identificationmodel, the signals of current sensors, force sensors, speed sensors between the simulationmodel and identification model will produce errors, if the errors are larger than the threshold,that show there were faults in the sensors, then a simulation test was taken,and thesimulation results showed the method was effective and reliable. In the operating mode ofsingle actuators failure, this paper utilize the control allocation method to maintain thevehicle stability, and take different control strategy according to the magnitude of the brakepedal force. If the driver have a light brake,only the bake system involved in the control, andif the driver have a moderate and heavy brake,the control allocation method was taken tohave a coordination control of the vehicle stability, brake system and AFS system wouldboth involved in the control system. The simulation results showed the method was effectiveand reliable when an actuator failure, and the vehicle could follow the ideal decelerate andlocus.2. Set up Hardware-in-Loop experimentp platform and experimentp study.In order to validate the reliability of control principle, a HIL test platform was builtbased on xPC Real-time simulation platform. A Tri-core electric pedal sensor module wasestablished in this paper to enhance the reliability of the electric pedal unit, and a redundantcontroller was designed based on hot-standby scheme. The redundant controller concludes amaster chip and a backup chip. The two chips communication with each other using anindependent channel and they work together. In the normal condition, only the control signalof the master chip is available, the backup chip observed the operation condition of themaster chip based on heartbeat signal. Once the master chip is found fault, the backup chipwill take over the work. In this paper, dual CAN network was established to enhance thereliability of the communication of network, the power of the actuators were supplied individually. Then Some HIL tests on the typical working conditions were proceed on thecompleted platform. The results show that: the designed fault diagnosis strategy and thevehicle stability control principle were effective and reliable.