Research On The Electric Power Steering Characteristics And Control System Of All Terrain Vehicle

Electric power steering system (EPS) is a new power steering device in recent years. Compared with hydraulic power steering deveice, it has the advantages of environmental protection, energy saving and installation, commissioning, repair, maintenance conmenience. More and more widely applied to the field of vehicle. At present EPS has been applied in low grade sedan in domestic. But the reports are rarely seen that the EPS is applied in the all terrain vehicle (ATV). ATV is more and more widely used in all walks of life. Because ATV traveling road surface are often more complicated. Beach, grassland, potholes all make the steering become very difficult. Therefore. ATV EPS research and development to improve the safety and comfort of driving have certain realistic and long-term significance.In order to realize electric assisted steering power function of ATV, need to study electric assisted steering power system to ATV and need to solve the key technical problems. This paper focus on three issues, namely, assist characteristic curve problem, hardware design problem and software design problems.Through the analyzed of system structure characteristics and dynamics, established mathematical model. The established model includes the linear two degrees of freedom vehicle steering system model, motor model and electric power steering. And using MATLAB/Simulink software to simulation and verification, Especially for ATV electric power steering key design steps in the assist process. The results can provide the theoretical basi reference data for the design of software and hardware.For the study of ATV electric power steering system, analyzed and researched three kinds of power curve on linear type, broken line and curve type. By established3D graph of the force output, speed and motor current to compare their performances and change relationship in the power steering control process.Through analysis and study, established the electric power steering composite type curves in the paper have the characteristics that rapid response like the linear power and steering smooth lile the curve type. Research shows that composite type assist curve design of ATV electric power steering is more reasonable.The hardware design is the software design plaform of ATV electric power steeing control system. The hardware design is intended to develop the hardware circuit which Applies to the ATV electric power steering control system. The control chip are selected to reach-40℃to+125℃temperature range in the design to meet the temperature range requirements of automotive electronic products. From the performance analysis of the absorption curent, the design of ATV steering control system hardware circuit is absorption current value small, work efficiency high and heat less. The hardware design not only provides a platform for software design, but also has important practical value for development and application of ATV eletric power steering system.The research of software design includes the control strategy, the program flow and fault diagnosis of ATV EPS. The control strategy ensures the steering process is smooth and light. Adopted control strategy is the fuzzy adaptive PID control in the paper and designed the fuzzy adaptive PID controller of ATV. Fuzzy cntrol is designed to make P I D parameters online correction changing with the input. Results shows that fuzzy adaptive PID control is better performance than traditional PID control of ATV electric power steering control system, it makes the steering control more stable and more reliable. Determined the control strategy, based the composite power curve and combined hardware design to design the software of ATV steering control system. Through the way of program flow to reflect the software design thought of ATV electric power steering control system. The fault tree and fault diagnosis chart are given in the software design. Software design has important practical value for the ATV electric power steering system development and application.The AVT electric power steering system controller that has been researched and developted was detected in the domestic relevant EPS detection mechanism. From the sixth chapter of this thesis, the indicators have reached the industry standards. From the test results (detection curve or data) analysis that power curve is smooth, jitter is small and test results are satisfactory. Also known from the power curve, that power limit current can up to50A. Through the results analysis of power current and absorption current, the heat is small, response speed and following is better, control performance is superior of the ATV electric power steering system controllemvhich researched and developted in the paper.The control system of theoretical analysis, computer simulation and experimental bench, real vehicle test results are in good agreement to the ATV electric power steering. It has important theoretical and practical significance for the based research, design and application to ATV electric power steering control system.