Research On Key Technologies Of Autonomous Steering Control Based On EPS

In recent years,the new round of technological changes represented by intelligence,automation and electric power are fundamentally affecting the automobile industry and mass transportation,especially the driving technology under intelligence and automation.Automatic driving covers a wide range of technologies,including environment awareness,planning and decision making,and bottom control execution.The steering control in the bottom control is the key to ensure the safe running of the vehicle.Based on electric power steering system(EPS)platform,this paper conducts research on automatic steering control and driving mode switching.Its specific research contents are as follows:First of all,the classification of electric power steering system is studied,In this paper,the column electric power steering system(C-EPS)is used as the steering actuator of automatic driving according to the situation of experimental vehicles.Existing laws and regulations specify self-driving cars must have a combination of automated driving and manned two driving modes,so this paper studies the different driving modes working principle of C-EPS,the dynamics model is established,and the key components of the power steering system motor and the angle torque sensor selection and research.Secondly,combined with the relevant knowledge of control theory,the overall design scheme of "three closed-loop" automatic steering controller based on fuzzy control theory is developed,including PI controller with current loop,PI controller with speed loop and fuzzy PID controller with position loop.Based on the calibration software developed by the company,the basic parameters of the three controllers are adjusted online.Then,the principle of fuzzy PID control is studied,and a reasonable fuzzy controller is designed for automatic steering system.Then the fuzzy PID software design process is presented,and MATLAB toolbox is used to generate offline query table,in order to facilitate the implementation of the algorithm in the embedded system.In order to verify the performance of the designed controller,the vehicle experiment of the designed automatic driving and automatic steering controller was carried out according to the technical index of automatic driving EPS.In the end,the switch from automatic driving mode to manual driving mode is studied,and the two key problems involved in EPS based driving mode switching are deeply explored.The first key problem is to accurately perceive the driver's intervention in steering system.The second key issue is how to ensure the smoothness and safety of steering when the control is transferred when the driver is perceived to have interfered with the steering system.Aiming at the first problem,this paper analyzes the reason why using the torque sensor value as the judgment condition is easy to cause false judgment.Therefore,based on the observer theory,this paper uses the extended observer to estimate the driver's hand torque and as the steering intervention judgment condition,and USES the simulation and experiment to verify the effectiveness of the designed algorithm.After estimating the driver's hand moment correctly,the moment threshold and time window are discussed.To solve the second problem above,in the process of switching from autonomous driving to manual driving,a sharing transition module is added.Under this module,autonomous driving and manual driving coexist to ensure a smooth transfer of control by changing the driving weight.In order to verify the effectiveness of the designed driving mode switching method,the designed driving mode switching method was tested in a real car.