Adaptive Speed Control Of Electric Vehicles In All Conditions Based On Mass And Slope Estimation

With the aggravation of environmental protection and energy problems,electric vehicles are facing significant development opportunities.The torque of each driving wheel of the inwheel-motor drive electric vehicle is independent controllable,which provides a good platform for the control of chassis dynamics.At the same time,with the continuous development of intelligent driving technology in recent years,the vehicle gradually tends to become an intelligent carrier that can meet the needs of people for a good driving experience.Various types of advanced driver assistance and autonomous driving technologies are also emerging in an endless stream,among which adaptive cruise control is an important one.Adaptive cruise control means that after the driver completes the setting of the desired vehicle motion state,the cruise control system takes over the vehicle completely,and completes the vehicle’s longitudinal motion control according to the optimal state,reducing the driver’s physical labor,improving traffic efficiency,and reducing traffic accident risk.At present,the research on adaptive cruise control is mostly focused on the multi-objective optimization and decision algorithm design of the planning decision level.In addition,the research on the adaptability of system working conditions has gradually become another hot topic.In particular,the relatively complex turning condition planning decision and motion control issues that have been studied less before have gradually attracted attention.Aiming at the common problems of the existing adaptive cruise control in the adaptability of working conditions,this paper proposes an all driving conditions adaptive speed control method based on quality and slope estimation,which effectively improves the adaptability of the speed controller in all driving conditions,and improves the response speed,stability and robustness of speed control.This paper can be divided into four parts as follows:1.In order to facilitate the simulation analysis and control strategy verification,this paper completes the vehicle dynamics modeling based on Car Sim and MATLAB / Simulink software.Firstly,the vehicle dynamic model with millimeter wave radar is built based on Car Sim software,and the driving motor model,braking system model and lateral driver model are built in Matlab/ Simulink software.Finally,the accuracy and reliability of the model are verified through cosimulation.2.In order to improve the adaptability of the adaptive cruise system to straight and curve conditions with slope,and ensure the speed control accuracy,stability,response speed and robustness,this paper designs a planning decision strategy with curve adaptability and a speed control strategy based on the vehicle longitudinal dynamic equation under all driving conditions.The vehicle speed control strategy is designed according to the hierarchical architecture,which mainly includes the planning decision layer and the motion control layer.The planning decision strategy divides the adaptive cruise control into cruise mode and follow mode.In cruise mode,the PID speed controller is established,and the curve speed is constrained by the safety index.In the following mode,firstly,the distance correction model for the detection workshop of the radar and the estimation model of the curve radius based on the trajectory fitting of the target vehicle are designed to obtain the actual workshop distance under all working conditions.Then,the ideal workshop distance model aiming at safety and comfort is designed,and the PID distance control model is designed.Considering the problem of radar detection failure in curve,a compensation mechanism is designed.The motion control strategy includes speed control strategy and drive / brake switching strategy.Firstly,the feedforward speed controller is established based on the vehicle longitudinal dynamic equation.Then,the mechanism of turning resistance is deduced based on the three degree of freedom vehicle model.And the turning resistance is introduced into the feedforward speed controller to solve the problem of decisionmaking torque deviation caused by the additional resistance of the traditional feedforward speed controller in the turning condition.In addition,in order to reduce the influence of environment interference and sensor noise on vehicle speed control,an active disturbance rejection controller with anti-interference capability is designed.In order to ensure that the desired drive / brake torque command determined by the speed controller is executed by the correct system,this paper also designs the driving / braking mode switching strategy.3.In order to solve the problem that the parameters of feedforward speed controller are many and complex,and the change of parameters will reduce the speed control accuracy,stability and response speed,this paper designs the all driving conditions mass estimator and joint slope estimator respectively.Firstly,through theoretical derivation and simulation verification,the influence of parameters of feedforward controller on vehicle speed control is analyzed,and the finally choice is to estimate the vehicle mass and road slope.Then,the principles of recursive least square method and kalman filter algorithm are analyzed and deduced.Finally,the all driving conditions mass estimator and the joint slope estimator are designed to provide accurate mass and slope values for the speed controller,which improves the adaptability of the speed controller to the working conditions,and ensures the speed control accuracy,stability and response speed of the all driving conditions.4.In order to verify the correctness and effectiveness of the all driving conditions parameter estimator and speed control strategy,this paper builds a co-simulation platform based on MATLAB / Simulink and Car Sim.The simulation results show that in turning conditions,compared with the traditional parameter estimator,the estimator designed in this paper has higher estimation accuracy.Compared with the traditional speed control strategy,the all driving conditons speed control strategy designed in this paper has better speed control accuracy,response speed and robustness.