Research On Active Steering Control Strategy Of Medium-sized Unmanned Vehicle

The automatic sorting of goods in modern logistics and the intelligent distribution of production materials in modern factories are inseparable from low-speed and medium-sized unmanned vehicles.The steering-by-wire of medium-sized unmanned vehicles is one of the key technologies to realize its intelligent driving.However,due to the influence of different weights and positions of the loaded goods and the manufacturing process of the chassis,the steering-by-wire precision is difficult to guarantee,resulting in medium-sized unmanned the vehicle’s driving path,space usage efficiency and transmission efficiency are greatly restricted.Therefore,the intelligent control of the steering-by-wire of medium-sized unmanned vehicles is a current research hotspot.In view of the problem that the steering precision of medium-sized unmanned vehicles is affected by various factors,the steering-by-wire accuracy is not high.The thesis is based on the analysis of the research status of active steering control technology for medium-sized unmanned vehicles at home and abroad,and carry out the reaserch about intelligent control strategy of the medium-sized unmanned vehicle steering-by-wire.The main research contents of the thesis are as follows:1.According to the structural design of the steering-by-wire system and selection of core devices for electronic control design,the overall scheme design of the medium-sized unmanned vehicle steering-by-wire system has been completed.2.Modeling and analysis of vehicle steering movement,including low-speed steering Ackerman steering geometric kinematics model and high-speed steering linear two-degree-of-freedom dynamic model.Combined with the structural parameters of the medium-sized unmanned vehicle in this experiment,a vehicle model was established in CarSim to provide a verification platform for the study of control strategies.3.The relationship between yaw speed and steering performance is expounded,combined with the modeling and analysis of vehicle steering movement,and then the thesis proposes two feasible steering control strategies,namely the front wheel angle feedforward control strategy and the fuzzy PID yaw rate feedback control strategy;in the former research,it is proposed to use the system identification technology to obtain the static steering model of the vehicle,and to combine the yaw rate in the motion to obtain a dynamic model;in the latter study,for the shortcomings of traditional PID,it is proposed to use a fuzzy PID controller to track and adjust the driving parameters to improve the control effect;the strengths and weaknesses of the two strategies are analyzed,and the fusion control strategy combining the two strategies is obtained.The joint simulation platform established by MATLAB / Simulink and CarSim was used to verify the program.The simulation results show that the medium-sized unmanned vehicle adopting active steering fusion control strategy can eliminate steering errors caused by external factors,and can achieve accurate steering at both low and high speed with good handling stability.4.Based on STM32F429IGT6,a steering-by-wire controller equipped with a fusion control strategy is designed.The experimental test vehicle is equipped with a steering-by-wire controller and equipped with a VBOX test device that can collect motion trajectories.The actual steering radius of the vehicle at low-speed and high-speed steering is respectively collected and compared with the expected value.The experimental results can meet the expected standard,which also proves that the active steering fusion control strategy designed in this thesis is feasible and effective.