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Stability control strategy of steer-by-wire system based on LQG/LTR

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Science China(Technological Sciences) 2017年第6期60卷 844-853页

作者： ZHANG Han zhao wanzhong College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang University

A control strategy based on LQG/LTR theory for steer-by-wire (SBW) system is proposed in this paper. Firstly, the models of the SBW system and the whole vehicle are constructed. econdly, the control strategy of LQG for SBW system is proposed, in which the LTR is utilized to eliminate the effect from the Kalman filter. Thirdly, simulations based on the co- simulation platform of MATLAB/Simulink and Carsim are performed with the proposed control strategy to identify its performance. At last, field experiments are conducted to further verify the feasibility of the proposed control strategy in real application. The simulation and experiment results indicate that the proposed control strategy has good stability, robustness and feasibility in real application, and is more effective in practical application of SBW system.

关键词： steer-by-wire (SBW) LQG/LTR stability control robustness Kalman filter

Robust control of hand wheel torque for active front steering system

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Science China(Technological Sciences) 2015年第1期58卷 107-116页

作者： zhao wanzhong LI YiJun WANG ChunYan College of Energy & Power Engineering Nanjing University of Aeronautics and Astronautics

Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of *** employs a steering motor to realize the functions of variable steering ratio and vehicle stability ***,it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering *** this paper,the optimum hand wheel torque is designed based on the linear tire *** the uncertainty and disturbance of the steering system and vehicle,an H∞controller is developed to make sure the hand wheel torque follows the reference torque accurately and *** simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.

关键词： active front steering variable steering ratio hand wheel torque H∞ control steering feel

Mixed H_2/H_∞ road feel control of EPS based on genetic algorithm

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Science China(Technological Sciences) 2012年第1期55卷 72-80页

作者： zhao wanzhong WANG ChunYan Department of Automotive Engineering Nanjing University of Aeronautics andAstronautics Nanjing 210016 China State Key Laboratory of Automotive Safety and Energy Tsinghua University Beijing 100084 China

In view of the existence of uncertainties such as system model and disturbance signal in the electric power steering （EPS） system, and the demand for system dynamic performance, the mixed H2/H∞, controller based on genetic algorithm is proposed. In order to obtain satisfactory steering feel, robust performance and steering stability, models of EPS system and a two-degree- of-freedom car are set up, then the state space model and the augmented matrixes are built. The H∞, method is introduced to minimize the effect of disturbances on the outputs, and the H2 method is applied to optimizing the system performance based on genetic algorithm. The simulation results show that the modified mixed H2/H∞ controller, which synthesizes the advantage of H2 control and Ha, control, has better robust performance and robust stability. The designed controller can attenuate the noises and disturbances caused by road random motivation, torque sensor measurement and model parameter uncertainty, enabling the driver to obtain satisfactory road feel.

关键词： vehicle engineering electric power steering the mixed H2/H∞ genetic algorithm road feel

Mode Switching and Consistency Control for Electric-Hydraulic Hybrid Steering System

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Automotive Innovation 2024年第1期7卷 166-181页

作者： Zhongkai Luan wanzhong zhao Chunyan Wang College of Energy and Power Engineering 29 Yudao St.Nanjing 210016China

Electric-hydraulic hybrid power steering(E-HHPS)system,a novel device with multiple modes for commercial electric vehicles,is designed to realize both superior steering feel and high energy ***,inconsistent steering perfor-mance occurs in the mode-switching process due to different dynamic characteristics of electric and hydraulic components,which even threatens driving *** this paper,mode-switching strategy and dynamic compensation control method are proposed for the E-HHPS system to eliminate the inconsistency of steering feel,which comprehensively considers ideal assistance characteristics and energy consumption of the ***,the influence of disturbances on system stability is analyzed,and H_(∞)robust controller is employed to guarantee system robustness and *** experimental results dem-onstrate that the proposed strategy can provide a steering system with natural steering feel without apparent inconsistency and effectively minimize energy consumption.

关键词： Hydraulic hybrid steering system Steering feel Consistency Mode switch Robust control

An actor-critic based learning method for decision-making and planning of autonomous vehicles

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Science China(Technological Sciences) 2021年第5期64卷 984-994页

作者： XU Can zhao wanzhong CHEN QingYun WANG ChunYan Department of Vehicle Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In order to improve the agility and applicability of trajectory planning algorithm for autonomous vehicles, this paper proposes a novel actor-critic based learning method for decision-making and planning in multi-vehicle complex traffic. It is the coupling planning of vehicle’s path and speed thus to make the trajectory more flexible. First, generations from the decided action to the planned trajectory are described by the end-point of the trajectory. Then, the actor-critic based learning method is built to learn an optimal policy for the decision process. It can update the policy by the gradient of the current policy’s advantage. In this process,features of the real traffic are carefully extracted by time headway(TH) and speed distribution. Reward function is built by the safety, efficiency and driving comfort. Furthermore, to make the policy network have better convergency, the policy network is modularized in two parts: the lane-changing network and the lane-keeping network, which decide the optimal end-point of the path and speed candidates respectively. Finally, the curved overtaking scenario and the interaction process with human driver are conducted to illustrate the feasibility and superiority. The results show that the proposed method has better real-time performance and can make the planned coupling trajectory more continuous and smoother than the existing rule-based method.

关键词： trajectory planning decision-making actor-critic feature extraction autonomous driving

An Energy Efficient Control Strategy for Electric Vehicle Driven by In-Wheel-Motors Based on Discrete Adaptive Sliding Mode Control

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Chinese Journal of Mechanical Engineering 2023年第2期36卷 302-313页

作者： Han Zhang Changzhi Zhou Chunyan Wang wanzhong zhao Vehicle Distributed Drive and Intelligent Wire Control Technology Research Center of Jiangsu Province Nanjing University of Aeronautics and AstronauticsNanjing 210016China

This paper presents an energy-efficient control strategy for electric vehicles(EVs)driven by in-wheel-motors(IWMs)based on discrete adaptive sliding mode control(DASMC).The nonlinear vehicle model,tire model and IWM model are established at first to represent the operation mechanism of the whole *** on the modeling,two virtual control variables are used to represent the longitudinal and yaw control efforts to coordinate the vehicle motion *** DASMC method is applied to calculate the required total driving torque and yaw moment,which can improve the tracking performance as well as the system *** to the vehicle nonlinear model,the additional yaw moment can be expressed as a function of longitudinal and lateral tire *** further control scheme development,a tire force estimator using an unscented Kalman filter is designed to estimate real-time tire *** these bases,energy efficient torque allocation method is developed to distribute the total driving torque and differential torque to each IWM,considering the motor energy consumption,the tire slip energy consumption,and the brake energy~?*** results of the proposed control strategy using the co-platform of Matlab/Simulink and CarSim way.

关键词： Electric vehicle Energy optimization Motion control Discrete adaptive sliding mode control

Tracking Performance of Electric Power Steering System Based on the Mixed H_2/H_∞ Strategy

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Chinese Journal of Mechanical Engineering 2011年第4期24卷 584-590页

作者： zhao wanzhong SHI Guobiao LIN Yi NIE Hong College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China

The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road feeling bad, and is influenced by the input steering torque and system measuring noise. However the existing methods have some shortages on system＇s robust dynamic performance and robust stability. The mixed H2/H∞ strategy for recirculating ball-type EPS system in a pure electric bus is proposed, and vehicle dynamic model of the system is established. Due to the existence of system model uncertainty, disturbance signals, sensor noises and the demand of system dynamic performance, the indexes of robust performance and road feeling for drivers are defined as the appraisal control objectives. The H∞ method is introduced to design the H∞ controller, and the H2 method is applied to optimize the H∞ controller, thus the mixed H2/H∞ controller is designed. The response of EPS system to the motor current command with amplitude of 20 A, the road disturbance with amplitude of 500 N and the sensor random noise with the amplitude of 1 A is simulated. The simulation results show that the recirculating ball-type EPS system with the mixed H2/H∞ controller can attenuate the random noises and disturbances and track the boost curve well, so the mixed H2/H∞ controller can improve the system＇s robust performance and dynamic performance. For the purpose of verifying the performance of the designed control strategy, the motor current tracking performance ground tests are conducted with step response input of the steering wheel, double-lane steering test and lemniscate steering test, respectively. The tests show that the mixed H2/H∞ controller for the recirculating ball-type EPS system of pure electric bus is feasible. The designed controller can solve the robust performance and robust stability of the system, thus improve the tracking performance of the EPS system and provide s

关键词： recirculating ball-type electrical power steering (EPS) system tracking performance mixed H2/H∞

Path planning and stability control of collision avoidance system based on active front steering

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Science China(Technological Sciences) 2017年第8期60卷 1231-1243页

作者： WNAG Chun Yan zhao wanzhong XU ZhiJiang ZHOU Guan Department of Automotive Engineering Nanjing University of Aeronautics and Astronautics Key Laboratory of Advanced Manufacture Technology for Automobile Parts Ministry of EducationChongqing University of Technology

Vehicle collision avoidance system is a kind of auxiliary driving system based on vehicle active safety,which can assist the driver to take the initiative to avoid obstacles under certain conditions,so as to effectively improve the driving safety of *** paper presents a collision avoidance system for an autonomous vehicle based on an active front steering,which mainly consists of a path planner and a robust tracking controller.A path planner is designed based on polynomial parameterization optimized by simulated annealing algorithm,which plans an evasive trajectory to bypass the obstacle and avoid *** dynamic models of the AFS system,vehicle as well as the driver model are established,and based on these,a robust tracking controller is proposed,which controls the system to resist external disturbances and work in accordance with the planning *** proposed collision avoidance system is testified through CarSim and Simulink combined simulation *** simulation results show that it can effectively track the planning trajectory,and improve the steering stability and anti-interference performance of the vehicle.

关键词： autonomous vehicle collision avoidance system path planning,μ synthesis robust control active front steering

Research on optimized GA-SVM vehicle speed prediction model based on driver-vehicle-road-traffic system

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Science China(Technological Sciences) 2018年第5期61卷 782-790页

作者： LI YuFang CHEN MingNuo LU XiaoDing zhao wanzhong College of Energy & Power Engineering Nanjing University of Aeronautics and Astronautics

The accurate prediction of vehicle speed plays an important role in vehicle's real-time energy management and online optimization control. However, the current forecast methods are mostly based on traffic conditions to predict the speed, while ignoring the impact of the driver-vehicle-road system on the actual speed profile. In this paper, the correlation of velocity and its effect factors under various driving conditions were firstly analyzed based on driver-vehicle-road-traffic data records for a more accurate prediction model. With the modeling time and prediction time considered separately, the effectiveness and accuracy of several typical artificial-intelligence speed prediction algorithms were analyzed. The results show that the combination of niche immunegenetic algorithm-support vector machine(NIGA-SVM) prediction algorithm on the city roads with genetic algorithmsupport vector machine(GA-SVM) prediction algorithm on the suburb roads and on the freeway can sharply improve the accuracy and timeliness of vehicle speed forecasting. Afterwards, the optimized GA-SVM vehicle speed prediction model was established in accordance with the optimized GA-SVM prediction algorithm at different times. And the test results verified its validity and rationality of the prediction algorithm.

关键词： driver-vehicle-road-traffic data records vehicle speed forecast optimized GA-SVM mode