Longitudinal Speed Tracking And Control Method For Intelligent Vehicles

Vehicle motion control,as a core technology of intelligent vehicles,is the premise and foundation to realize intelligent behavior.Thus,in-depth research into it is of great significance.This dissertation focuses on longitudinal speed tracking and control method for intelligent vehicles,and the following research works are carried out,such as longitudinal dynamics modeling and actuator design,speed tracking control,full speed range car following control,and real-time economic speed control.A longitudinal dynamic model for intelligent vehicle is established,which includes overall vehicle dynamics model,powertrain model and brake system model.The data of bench tests and vehicle tests are analyzed,and system control characteristics are partly obtained.To build a test platform for off-road vehicle,an electropneumatic brake system is designed according to the structure and characteristics of the air brake system of original vehicle,which realizes electronic control brake in unmanned driving mode,and reserves pedal brake in manual driving mode.The two modes can be switched freely.The control characteristics of solenoid valve,vehicle rolling resistance coefficient on different roads,the relationship among vehicle deceleration,speed and control inputs of electronic control brake are identified through vehicle tests,which provide experimental bases and theoretical supports for formulating further control strategies.A model predictive speed tracking control approach is proposed to realize high precision speed tracking control.The proposed system has an upper level controller and a lower level controller.The lower level controller is designed according to the control characteristics of the simulation vehicles and test vehicles,and the upper level controller is designed on the basis of model predictive control(MPC).Then the performance of the system is firstly verified by using co-simulation of MATLAB/Simulink and Car Sim,and a passenger car with hydraulic brake system and an off-road vehicle with air brake system are finally used as test platforms to carry out the experimental research,respectively.In order to realize a smooth transition during mode switching for full speed range car following control,a concept of reaction headway is introduced,and only a single control algorithm is used.Combined with the experience of skilled drivers,reaction headway has been used to describe when the subject vehicle should react to the preceding vehicle.The reaction headway is considered in the upper level controller,and linear quadratic regulator(LQR)and MPC controller are designed,respectively.The feasibility of the system is verified by simulations and vehicle tests.In order to make full use of the signal phase and timing(SPaT)information of a single traffic signal to conduct the real-time economic vehicle speed control with a preceding vehicle,the condition without preceding vehicle is firstly carried out.Based on the architecture of MPC,two control strategies,slowing down and stop when encountering a red signal in reaction headway and avoiding idling during the red signal,are designed and implemented.On the basis of simulations,the two control strategies are compared by changing the initial condition.It is pointed out that starting to slow down over a long distance will increase fuel consumption when avoiding idling during the red signal and the quantitative description of the judging condition is given.Thus,a new control strategy is obtained,and simulations and vehicle tests are carried out.Then the economic vehicle speed control without preceding vehicle and the full speed range car following control are integrated to design an economic vehicle speed control system with preceding vehicle,and the feasibility of the system is verified by simulations.