Research On Differential Steering Control System Of Four-wheel Drive With In-wheel Motor

Steering control system is an important part in moving control of vehicle. Existing turning way of four-wheel vehicle are front-wheel steering, all-wheel steering and crab-craw steering. Among them, differential steering model of front-wheels driving is currently used mostly widely. The advantage is that the controlling is relatively simple, but the disadvantage is the turning radius is too large. Especially when moving slowly, differential steering model of front-wheels driving is lack of some flexibilities. This paper mainly studies on the following works based on four-wheel vehicle.(1) Establish of kinematics and dynamics models of differential steering system with front and rear wheels reverse rotation. Analyzing the Ackermann-Jeantand characteristic function of the traditional front-wheel differential steering model. According to the analysis of the characteristic function, deriving and verifying the characteristic function of steering model of front and rear wheels reverse rotation in differential speed, built kinematics and dynamics models for research.(2) Study on electrical differential controlling strategy to vehicle moving. The main controller coordinates and distributes the four-wheel speeds when driving in straight line and in turning, In order to sure the vehicle moving in the expected locus, the motor driven controller adjust the motor speed with Fuzzy-PID control algorithm to lead the actual motor speed mostly closing to the theoretical speed output from main controller.(3) In simulation environment, combined with the mathematical model of in-wheel motor and analysis results of steering model of front and rear wheels reverse rotation in differential speed, make simulation between the wheel speed and velocity & steering angle under the steering model. The simulation results show that the design of electronic differential control strategy can realize the speed control of each wheel, achieve the smooth moving in medium and small steering angle.(4) Develop corresponding hardware and software system, experimental verification for the differential steering control strategy and speed control arithmetic. According to functional allocation of steering control system, on the hardware side, design all kinds of circuit, such as receiving and sending out of control signals circuit, and speed testing circuit based on ARM chip, four speed regulation motor driven controller circuit based on PIC SCM. On the software side, design programs such as receiving and sending out of control signals, motor driven controller and Fuzzy-PID speed adjustment. Finally, did test to validate the research contents, which show out the feasibility of the control strategy of differential steering system with front and rear wheels reverse rotation and the practicality of the Fuzzy-PID speed regulating control method.