Research On Multi-Mode Switching Control Of Automotive Adaptive Cruise Control System

With the advancement of technology and the rise of the smart driving boom,the advanced driver assistance systems for automobiles have become a hot topic at home and abroad.As an important part of the advanced driver assistance system,the research of adaptive cruise control system has also received extensive attention in recent years.At present,the adaptive cruise control system has many shortcomings,such as simple in function,the system is unable to adapt to the complicated and changeable traffic environment and the design of the controller has insufficient considerations for comfort and fuel economy.In this paper,an adaptive cruise control system based on multi-mode switching is designed.Based on the feedforward control algorithm,PID control algorithm and model predictive control algorithm,the adaptive cruise controller is designed with fully considering the performance indicators such as safety,comfort and fuel economy.The main research content is detailed below.First of all,this paper carries on the overall design plan of the automobile adaptive cruise control system,defines the system function,divides the system module,and has determined the key technology of each module.In response to the vehicle dynamics model in key technologies,a dynamic model was established in CarSim which has a powerful dynamic database.Based on the dynamic model,a corresponding inverse longitudinal dynamics model is established,including an inverse engine model and a reverse braking system model,and the switching strategies of the two are given.Then,adaptive cruising conditions are analyzed,and the working conditions are re-divided according to the horizontal and vertical travel conditions of the front and rear cars as the four conditions of takeover,cruising,follow-up,and lane-changing.Based on the workshop distance,vehicle speed,and lane change signal,the switching logic between operating conditions is planned to conform to the normal driver operating habits.The requirements for inter-vehicle distance are different for different conditions.This paper calculates the takeover distance accurately based on the distance strategy of the acceleration of the preceding vehicle.Determine the appropriate expected follow-up distance and cruising distance based on the stable headway strategy.In addition,taking into account the different follow-up styles of different drivers,three follow-up headways are set for the driver to choose.Second,an adaptive cruise controller is designed using a layered control mechanism.The lane change and cruise operating conditions only control the vertical speed,so a simple PID control algorithm is used to design the upper controller.The follow-up process needs to maintain the distance from the preceding vehicle,and also to maintain a certain speed to follow the preceding vehicle.In addition,the comfort and fuel economy must be considered.Therefore,a model prediction algorithm that can control the target with multiple constraints is selected to design the follow-up vehicle controller.The lower controller should use the vehicle dynamics system as the control object to complete the tracking control of the acceleration,this paper uses the PID control algorithm and feedforward algorithm to design the lower controller with consideration of the strong nonlinearity of the vehicle dynamics system and hysteresis of brake hydraulic system.Finally,general-purpose modules are used to establish a control system model in Simulink and a vehicle dynamics model is established in CarSim.The combination of the two sets up an adaptive cruise off-line co-simulation model to verify the effectiveness of the control system.This paper sets up five kinds of operating conditions: takeover,lane changing,cruising,following car and full mode switching.The simulation results show that the control algorithm designed in this paper has good control effect and the designed adaptive cruise control system meets the requirements.