Research On The Omni Directional Steering System Of Space Saving Electric Vehicle Based On In-Wheel Motor

With the increasing number of vehicles in urban areas, environmental pollution, energy crisis, travelling and parking in the city have become significant problems in our country. The development of new energy vehicles has a positive significance to reduce the environmental pollution and alleviate the energy crisis. At the same time, developing the high operational mini electric vehicle is becoming an effective way to overcome the congestion of traffic and improve the utilization rate of roads and parking lots based on the advantages of in-wheel motor. In order to improve the mobility of vehicle, reduce the difficulty of parking operation and get a high utilization rate of roads and parking lots, this thesis carries out a research on the novel omni directional steering system of electric vehicle based on in-wheel motor. The main researches of this thesis focus on the following:First of all, the thesis presents a novel omni directional steering system with higher maneuverability and stability.It achieves the design of omni directional independent steering mechanisms based on the advantages of in-wheel motor after analyzing the advantages and disadvantages of the mainly omni directional steering mechanisms. It proposes the novel steering system which consists of both the novel omni directional independent steering mechanisms and the redesigned 2 front wheel steering mechanisms to take account of both maneuverability and stability, so it could make full use of the advantages of steering by wire technology and conventional mechanical steering technology. Then it completes the 3D modeling and optimization of steering system based on Solidworks. For achieving the omni directional motions and conventional motions with omni directional steering mechanisms, it proposes a novel control system and control strategy. To validate the feasibility of omni directional motion, a set of omni directional independent steering mechanisms is processed, assembled and tested. Also, it purchases and checkes the corresponding driving control device and steering control device according to the requirements of the steering control system.Secondly, the kinematics modeling and analysis of the omni directional steering system are proposed in this thesis.It completes the kinematics modeling and analysis of the omni directional independent steering structure based on the kinematics theory of four bar linkage, and it gets the functional relationship between steering angle of the wheel and driving angle of the steering motor. According to the different steering modes of vehicle, it makes the kinematics modeling and analysis of vehicle, and obtains the function of each wheel steering angle control and each wheel driving speed control. It provides theoretical guidance and reference for steering by wire control and driving by wire control of vehicle.Finally, this thesis focuses on the simulation of the omni directional steering system.It chooses the PID control algorithm as the control strategy of steering motor and driving motor depending on the requirement of response speed, stability and accuracy of steering control and driving control, then it establishes simulation models of steering control system and driving control system using Matlab/Simulink. In order to demonstrate the performances of steering control and driving control under the conventional steering motions and omni directional steering motions, it has done the simulation experiments with Matlab. The results show that response speed, stability and accuracy of the proposed steering by wire and driving by wire control systems perform very well.