Research On The Testing Platform For The Development Of BBW System

Due to the good maintainability, the strong functional scalability and the avoidance of hydraulic transmission lag, BBW (Brake-by-Wire) system has been the main tendency of the future vehicle’s brake control system and is adopted by more and more vehicles nowadays. To facilitate the development of BBW system, this thesis carries out a research on the testing platform for simulation purpose of human-vehicle-pavement closed loop system. This testing platform has a good quality of real-time operation, high stability and good reliability. As part of the testing platform, vehicle model, driver model and malfunction model are also emphatically investigated through the research.This testing platform employs the NI PXI real-time equipment and integrates the steering wheel, the brake pedal, the vacuum booster, the seat, the BBW system etc. The hardware-in-loop real-time simulation for the BBW controllers and actuators can be therefore conducted. The controller collects information on vehicle states from the vehicle model, which is configured in the professional software Carsim by using the data measured from the real vehicle. The software/hardware interfaces are developed to transport data of the vehicle states and the wheel cylinder pressures on the platform in real time. An I/O board is developed to generate the wheel speed signal of active/passive wheel speed sensor, vehicle longitudinal speed signal, lateral acceleration signal, yaw speed signal etc.The traditional driver models used in the research on vehicle stabilities never concern the pavement conditions and the steering wheel torque. Therefore the traditional driver models cannot inspect and validate the control strategy of BBW system working under special braking conditions. The driver model proposed in this thesis is specialized for application on the development of BBW system. This thesis conducts a large number of field tests and investigates the handling characteristics of various drivers under the braking conditions of different initial speeds and different fluctuations in brake fluid pressures. The Crossover Model is used to characterize the driver handling behaviors and the least square method is employed to identify the model parameters through the field test data. This driver model considers mainly the influence of the steering wheel torque and is specially oriented to the simulation tests for vehicle braking stability. The simulation results of the driver model agree well with the field test data.This thesis also takes account of the influence of the failure conditions, such as the sensor failure, the actuator failure and the special adhesion conditions of the pavements, to better inspect the control logics and the control strategies of the BBW system. Two methods are used to layout the failure tests, namely the hardware-in-loop simulation on the testing platform and the pure numerical simulation in the personal computer. The failure conditions are achieved with the software or by using the defective hardware directly. The more efficient simulation method is adopted to research the failure conditions according to the objectives of specific tasks.