Research On Path Tracking Algorithm And Lower Control System For Intelligent Vehicle

The Intelligent Vehicle (IV) is an important part of the Intelligent TransportSystem (ITS), it is the combination of environment observation, decision support,path tracking, lower control and other functions. Among these functions, the pathtracking and the lower control are the most essential technologies of the intelligentvehicle’s autonomous driving, the accuracy and effectiveness of them are the basics ofthe autonomous driving.This work uses the intelligent vehicle BJUT-IV, owned by Beijing University ofTechnology, as the research platform, does the study focused on a key problem of theintelligent vehicle’s movement control–lateral and longitudinal movement control.This work establishes the system structure of the intelligent vehicle, introduces thehardware platform and the main sensor, sets the function of each module andestablishes the CAN communication and UDP communication during them. Thenaccording to the dynamics analysis of the vehicle, this work establishes the dynamicsmodel for the vehicle.This work does the study mainly about the technology of lateral and longitudinalcontrol and path tracking, in order to perform a real-time lateral and longitudinalcontrol on the vehicle. The lateral and longitudinal control can be divided into uppercontrol and lower control. The upper control includes the algorithm of path trackingand the strategy of speed control. The lower control includes the strategy of steeringmotor control and the strategy of throttle and brake control based on the speed.First, this work concentrates on the analysis of the existing classical pathtracking method and finally comes up with an improved algorithm of path trackingbased on the Pure Pursuit path tracking algorithm according to the dynamic model,which improves the stability and accuracy of the movement, and the adaptability tothe speed.Secondly, this work also analyzes the factors which influent the speed, designs astrategy of speed control and establishes the longitudinal control system based on thethrottle control and brake control, which achieves the tracking of the desired speed byswitching between the throttle acceleration and brake deceleration. At the same time,this work designs the improved fuzzy step braking algorithm to prevent the frequentand reciprocating jitter of the footstep during the braking process. In addition, toreduce the time of the switching between the throttle acceleration and brakedeceleration, this work improved the switching rule.Thirdly, according to the requirements of the movement system, this workdesigns the controller of the hardware in lower control, and based on that hardwareplatform, achieves the interactive use between the CAN bus and the serial portcommunication, which makes the lateral and longitudinal movement meets therequirements of the instantaneity. At the same time, this work designs the software foreach of the lower control MCU based on the modular design idea.Finally, this work discusses the overall design idea, hardware composition, software design methods and functions for the movement system. Then, throughmany experiment with the real vehicle, this work proves that the results are fullyapplicable to the BJUT-IV. Besides this, the path tracking situation during theexperiments can proves the effectiveness of the strategy and the related algorithmdesigned by this work.