An improved LuGre model for calculating static steering torque of rubber tracked chassis

Tire and rubber track interchangeable chassis combines the advantages of tire and rubber track,which can greatly improve the maneuverability of military construction machinery.However,there is almost no effective calculation model for the real-time static steering torque.When the relative sliding speed is greater than 0.01 m/s,the influence of friction heating can not be ignored.An improved LuGre model is established to calculate the static real-time steering torque of tire and rubber track interchangeable chassis.Firstly,the friction heating model between rubber and ground is established.Combined with the influence of temperature on the dynamic performance of rubber material,the influence of friction heating on the stiffness and friction coefficient of rubber track is analyzed,and the improved LuGre friction model is established.The steering torque of tire and rubber track interchangeable chassis is affected by rubber material properties,steering speed,pavement type,and ambient temperature.Compared with the original Lu Gre model,the improved LuGre model captures the change in friction torque during multiple in-situ turns due to frictional heating.The error with the experimental data is small,which verifies the effectiveness of the improved LuGre model.

Disturbance Observer Based Control for Four Wheel Steering Vehicles With Model Reference

This paper presents a disturbance observer based control strategy for four wheel steering systems in order to improve vehicle handling stability. By combination of feedforward control and feedback control, the front and rear wheel steering angles are controlled simultaneously to follow both the desired sideslip angle and the yaw rate of the reference vehicle model.A nonlinear three degree-of-freedom four wheel steering vehicle model containing lateral, yaw and roll motions is built up, which also takes the dynamic effects of crosswind into consideration.The disturbance observer based control method is provided to cope with ignored nonlinear dynamics and to handle exogenous disturbances. Finally, a simulation experiment is carried out,which shows that the proposed four wheel steering vehicle can guarantee handling stability and present strong robustness against external disturbances.

Analysis of steering performance of differential coupling wheelset

In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differential cou- pling wheelset （DCW） was developed in this work. The DCW was composed of two independently rotating wheels （IRWs） coupled by a clutch-type limited slip differential. The differential contains a static pre-stress clutch, which could lock both sides of IRWs of the DCW to ensure a good steering performance in curves with large radius and tangent track. In contrast, the clutch could unlock the two IRWs of the DCW in a sharp curve to endue it with the characteristic of an IRW, so that the vehicles can go through the tight curve smoothly. To study the dynamic performance of the DCW, a multi-body dynamic model of single bogie with DCWs was established. The self-centering capability, hunting stability, and self-steering performance on a curved track were analyzed and then compared with those of the conventional wheelset and IRW. Finally, the effect of coupling parameters of the DCW on the dynamic performance was investigated.

Steering Control of Wheeled Armored Vehicle with Brushless DC Motor

Considering the steering characters of one type of wheeled armored vehicle, a brushless direct current （DC） motor is adapted as the actuator for steering control. After investigating the known algorithms, one kind of algorithm, which combines the fuzzy logic control with the self-adapting PID control and the startup and pre-hrake control, is put forward. Then a test-bed is constructed, and an experiment is conducted. The result of experiment confirms the validity of this algorithm in steering control of wheeled armored vehicle with brushless DC motor.

Research on Vehicle Control Technology Using Four-Wheel Independent Steering System

The enhancement of vehicle handling stability and maneuverability through active and independent rear wheels control is presented. Firstly, the configuration of four-wheel independent steering prototype vehide is introduced briefly. Then the concrete overall design of the electronic controllers of four wheel independent steering system （4WIS） is formulated in details. Under the control strategy of zero sideslip angle at mass center, the mathematical model of 4WIS is established to deduce the equations of separated rear wheel steering angles. According to these equations, simulation analysis for 4WIS vehicle performances is finished to show that 4WIS vehicle can improve the maneuverability greatly at low speed and increase the handling stability at high speed. Finally, the road test of 4WIS vehide has performed to verify the correctness of simulation and show that compared with the conventional four wheel steering （4WS） vehicle, the 4WIS vehicle not only improves the kinematical harmony but also decreases steering resistance and lighten abrasion of tires.

Fatigue behavior of magnesium alloy and application in auto steering wheel frame

The low-cycle fatigue behaviors of AZ91HP-F,AZ91HP-T6,AZ91HP-T4 and AM50HP-F were investigated,and the potential application of AM50HP-F in steering wheel frame was studied.The steering wheel properties were characterized by bend fatigue and tensile testing,and the fatigue fracture was analyzed by SEM.The results show that the fatigue lives of AZ91HP-F and AZ91HP-T6 have little difference by comparing the low-cycles fatigue properties of different heat treatment states.The crack propagation velocity of AZ91HP-T4 is lower than that of AZ91HP-F and AZ91HP-T6.The die casting technological parameters of the magnesium steering wheel have been optimized with the aid of flow-3D software.The tensile testing results of the different part of magnesium steering wheel show that the ultimate tensile strength and elongation in the wheel arm and wheel rim have no difference and the average value are 220 MPa and 5%,respectively.The fracture is in the brittleness mode and the fatigue crack initiates at the outside of the wheel rim.

Torque Distribution of Electric Vehicle with Four In-Wheel Motors Based on Road Adhesion Margin

With the worsening of energy crisis and environmental pollution,electric vehicles with four in?wheel motors have been paid more and more attention. The main research subject is how to reasonably distribute the driving torque of each wheel. Considering the longitudinal motion,lateral motion,yaw movement and rotation of the four wheels,the tire model and the seven DOF dynamic model of the vehicle are established in this paper. Then,the torque distribution method is proposed based on road adhesion margin,which can be divided into anti ? slip control layer and torque distribution layer. The anti?slip control layer is built based on sliding mode variable structure control,whose main function is to avoid the excessive slip of wheels caused by road conditions. The torque distribution layer is responsible for selecting the torque distribution method based on road adhesion margin. The simulation results show that the proposed torque distribution method can ensure the vehicle quickly adapt to current road adhesion conditions,and improve the handling stability and dynamic performance of the vehicle in the driving process.

Sensor-less Terrain Estimation and Torque Control of a Wheeled Mobile Robot

As unmanned electric wheeled mobile robots have been increasingly applied to high-speed operations in unknown environments,the wheel slip becomes a problem when the robot is either accelerating,decelerating,or turning at high speed.Ignoring the effect of wheel slip may cause the mobile robot to deviate from the desired path.In this paper a recently proposed method is implemented to estimate the surface conditions encountered by an unmanned wheeled mobile robot,without using extra sensors.The method is simple,economical and needs less processing power than for other methods.A reaction torque observer is used to obtain the rolling resistance torque and it is applied to a wheeled mobile robot to obtain the surface condition in real-time for each wheel.The slip information is observed by comparing the reaction torque of each wheel.The obtained slip information is then used to control the torque of both wheels using a torque controller.Wheel slip is minimized by controlling the torque of each wheel.Minimizing the slip improves the ability of the unmanned electric wheeled mobile robot to navigate in the desired path in an unknown environment,regardless of the nature of the surface.

All-Electric Aircraft Nose Wheel Steering System with Two Worm Gears

As all-electric aircraft has many advantages,an aircraft nose wheel steering system would be developed to the all-electric direction.Concerning the control demand of the nose wheel steering system,based on the basic principles of nose wheel steering system and the design technique of mechanotronics,an all-electric aircraft nose wheel steering system,composed of a nose wheel steering mechanism of two worm gear and a control servo system of fly-by-wire with both steering and anti-shimmy functions is designed to meet the demand for operation control in the nose wheel steering system.Then,based on the LMS-AMESim software,the simulation model of the system is established to simulate the dynamics for the verification of its steering function.The simulation results indicate that the nose wheel steering system is reasonable,and can meet the requirements of the general project.Furthermore,the prototypes of the steering mechanism and control system are studied to validate the design,and the steering test bench is prepared to test the designed system.The test results,such as steer angle,rotate speed of motor are analyzed in details and compared with the theoretical results.The analysis and comparison results show that the design is reasonable and the property of the prototype can achieve the design objectives.

Multi-objective Optimization of Differential Steering System of Electric Vehicle with Motorized Wheels

A differential steering system is presented for electric vehicle with motorized wheels and a dynamic model of three-freedom car is built.Based on these models,the quantitative expressions of the road feel,sensitivity,and operation stability of the steering are derived.Then,according to the features of multi-constrained optimization of multi-objective function,a multi-island genetic algorithm(MIGA)is designed.Taking the road feel and the sensitivity of the steering as optimization objectives and the operation stability of the steering as a constraint,the system parameters are optimized.The simulation results show that the system optimized with MIGA can improve the steering road feel,and guarantee the operation stability and steering sensibility.

Steering mechanical analysis for lunar rover wheel

Facing the requirement of establishing a steering mechanical model for the wheel configuration design,selection of steering motors, dynamic analysis and simulation of the lunar rover, shear force beneaththe steering wheel, bulldozing resistance acting on steering wheel rims and side surfaces respectively areconducted on the basis of the wheel-loose soil interaction. The quantitative relation between steering resistancemoment (SRM) and steering radius, dimension of the wheel, soil parameters is established. Tovalidate the model, a single-wheel test bed is employed to test the steering performance of a wheel with0.15735m radius and 0.165m width when the steering radius is 0.00m, 0.04m, 0.08m, 0.12m and0.16m, respectively. The SRM is approached asymptotically with the increasing steering angle and almostproportional to the steering radius. The theoretical results of SRM are compact with the experimental results,which shows that the steering model can predict the experimental results well.

Research on the Variable Steering Ratio of Four-Wheel-Steering Vehicle

The steering characteristic of a four-wheel-steering vehicle is numerically simulated for in-depth research of the handling stability of four-wheel steering. The research results show that the deteriorating tendency of the steering stability due to the increase of the vehicle speed is improved obviously in the case of four-wheel steering. The approach of variable steering ratio is discussed. The use of the variable steering ratio can not only raise the steering stability of vechicles at high vehicle speed, but also reduce the dicomfort and steering burden of drivers; and hence is helpful for the subjective evaluation of four-wheel steering vehicles.

Research on Steering Resistance Moment of Wheel Loader

The wheel loader as the research object in present article,its steering mechanism is analyzed for the relationship between the steering cylinder displacement and the steering angle,which means,the relationship between the arm of steering resistance moment and the steering angle.In addition,the relationship between the in-situ steering resistance moment and the wheel angle is also be analyzed by integrating the interaction between the tire and the ground.The Matlab will help to build the mathematical modeling for verification.

Robust control of hand wheel torque for active front steering system

Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of vehicles.It employs a steering motor to realize the functions of variable steering ratio and vehicle stability control.However,it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering angle.In this paper,the optimum hand wheel torque is designed based on the linear tire model.Considering 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 quickly.The simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.

Lateral stability region conservativeness estimation and torque distribution for FWIA electric vehicle steering

Estimation of the lateral stability region and torque distribution on steering is very important to improve stability in lateral handling for all wheel drive electric vehicles.Based on the built-nonlinear vehicle dynamic model,the lateral stability region of the vehicle related to steering is estimated using Lyapunov function.We obtained stable equilibrium points of non-straight driving according to the estimated lateral stability region and also reconstructed the Lyapunov function matrix,which proved that the closed-loop system composed of yaw rate and lateral velocity is satisfied with negative definite property.In addition,the designed controller dynamically allocates the drive torque in terms of the vertical load and slip rate of the four wheels.The simulation results show that the estimated lateral stability region and the designed controller are satisfactory in handling stability performance against different roads and vehicle parameters.

Kalman Filter-Based Fusion Estimation Method of Steering Feedback Torque for Steer-by-Wire Systems

Universal challenge lies in torque feedback accuracy for steer-by-wire systems,especially on uneven and low-friction road.Therefore,this paper proposes a fusion method based on Kalman filter that combines a dynamics-reconstruction method and disturbance observer-based method.The dynamics-reconstruction method is designed according to the vehicle dynamics and used as the prediction model of the Kalman filter.While the disturbance observer-based method is performed as an observer model of the Kalman filter.The performance of all three methods is comprehensively evaluated in a hardware-in-the-loop system.Experimental results show that the proposed fusion method outperforms dynamics reconstruction method and disturbance observer-based method.Specifically,compared with the dynamics-reconstruction method,the root mean square error is reduced by 36.58%at the maximum on the flat road.Compared with the disturbance observer-based method,the root mean square error is reduced by 39.11%at the maximum on different-friction and uneven road.

基于电动方向盘的拖拉机自动导航转向控制方法

为提高轮式拖拉机自动导航过程中转向控制的精度与稳定性,该研究以雷沃欧豹M704-2H拖拉机作为试验平台,采用电动方向盘作为转向执行机构,分析转向机械间隙对控制精度的影响,针对转向间隙特性设计转向控制算法。首先,为了获得准确的转向角,利用GNSS(global navigation satellite system)与二轮车模型快速标定虚拟轮转角,标定结果表明:虚拟轮转角的最大误差为1.3°,平均误差为0.11°。然后,对转向系统的机械间隙进行分析,设计一种带有间隙补偿的模糊PD(proportional derivative)转向控制算法,并在Simulink中验证算法的可行性。实车试验结果表明,该算法跟踪方波转角信号的响应时间为1.1 s,最大稳态误差为0.65°,平均稳态绝对误差为0.132°。跟踪正弦波转角信号的平均延时为0.5 s,最大误差为1.91°,平均绝对误差为1.09°。与无间隙补偿算法相比,有间隙补偿算法跟踪方波信号最大稳态误差减小了0.022°,平均稳态绝对误差减少了0.112°,角度误差在±0.2°内的时间提升了71%;跟踪正弦波信号最大误差减小了0.68°,平均绝对误差减小0.23°。田间直线导航转向控制试验结果表明,转角跟踪的绝对平均误差为0.61°,最大跟踪误差为2.82°,转向控制跟踪精度较高,稳定性好,满足导航作业需求。

两轴径向独立轮副轨道车辆动力学性能

针对独立车轮导向问题提出后倾角导向方法,使独立轮副轨道车辆获得自导向能力。阐述车辆的自导向原理,利用横向轮轨力和后倾角力臂形成摇头力矩,使独立车轮自动转向。关于中心对称的前后独立轮副分别向相反方向转向,使独立车轮处于径向位置。采用多体动力学方法分析独立轮副轨道车辆的自导向性能。结果表明:在直线轨道上,后倾角对车辆横向位移和摇头角的影响明显。带后倾角车辆出现类蛇行运动现象。具有后倾角的车辆在直线轨道上能够自动复位。在曲线轨道上,左前导向轮具有较大的冲角。后倾角能够使车辆动态对中,最终回到轨道中心线位置。带后倾角的独立轮副轨道车辆在曲线轨道上具有有限的导向能力。

线控主动四轮转向汽车控制策略研究

目的针对线控四轮转向汽车横向稳定性不足及控制鲁棒性差等问题,提出一种主动转向反馈控制策略。方法使用Simulink搭建线控转向系统转向执行机构动力学模型,将MATLAB/Simulink与Carsim联合仿真,建立线控四轮转向整车模型;基于二自由度模型分析横摆角速度和质心侧偏角对汽车稳定性的影响,推导理想的横摆角速度和质心侧偏角;以横摆角速度增益恒定为依据设计理想传动比,得到期望前轮转角,以横摆角速度误差为控制量设计模糊控制器得到附加前轮转角对期望转角实时修正,实现前轮主动转向;针对横摆角速度和质心侧偏角与理想值之间的误差,加权得到稳定性控制目标;设计自适应积分滑模反馈控制策略输出后轮转角,对理想值进行跟踪,实现后轮主动转向。结果仿真实验结果表明:所搭建的线控转向系统能够准确反映汽车动力学特性。相比无控制的机械前轮转向汽车与横摆反馈控制的四轮转向汽车,线控主动四轮转向汽车在双移线工况下将质心侧偏角控制在0值附近波动,横摆角速度跟踪误差控制在1.149 deg/s以内;在角阶跃工况下将质心侧偏角稳态值控制在0.065 deg,横摆角速度稳态值误差为0.074 deg/s。结论线控主动四轮转向控制策略在双移线和角阶跃工况下控制效果显著,鲁棒性能好,能有效提高汽车的操纵稳定性和主动安全性。