Dynamics and Wheel's Slip Ratio of a Wheel-legged Robot in Wheeled Motion Considering the Change of Height

The existing research on dynamics and slip ratio of wheeled mobile robot （WMR） are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS- Ⅱ. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS- Ⅱ in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified, Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

Identification of Maximum Road Friction Coefficient and Optimal Slip Ratio Based on Road Type Recognition

The identification of maximum road friction coefficient and optimal slip ratio is crucial to vehicle dynamics and control.However,it is always not easy to identify the maximum road friction coefficient with high robustness and good adaptability to various vehicle operating conditions.The existing investigations on robust identification of maximum road friction coefficient are unsatisfactory.In this paper,an identification approach based on road type recognition is proposed for the robust identification of maximum road friction coefficient and optimal slip ratio.The instantaneous road friction coefficient is estimated through the recursive least square with a forgetting factor method based on the single wheel model,and the estimated road friction coefficient and slip ratio are grouped in a set of samples in a small time interval before the current time,which are updated with time progressing.The current road type is recognized by comparing the samples of the estimated road friction coefficient with the standard road friction coefficient of each typical road,and the minimum statistical error is used as the recognition principle to improve identification robustness.Once the road type is recognized,the maximum road friction coefficient and optimal slip ratio are determined.The numerical simulation tests are conducted on two typical road friction conditions（single-friction and joint-friction）by using CarSim software.The test results show that there is little identification error between the identified maximum road friction coefficient and the pre-set value in CarSim.The proposed identification method has good robustness performance to external disturbances and good adaptability to various vehicle operating conditions and road variations,and the identification results can be used for the adjustment of vehicle active safety control strategies.

Influence of Tire Dynamics on Slip Ratio Estimation of Independent Driving Wheel System

The independent driving wheel system, which is composed of in-wheel permanent magnet synchronous motor（I-PMSM） and tire, is more convenient to estimate the slip ratio because the rotary speed of the rotor can be accurately measured. However, the ring speed of the tire ring doesn’t equal to the rotor speed considering the tire deformation. For this reason, a deformable tire and a detailed I-PMSM are modeled by using Matlab/Simulink. Moreover, the tire/road contact interface（a slippery road） is accurately described by the non-linear relaxation length-based model and the Magic Formula pragmatic model. Based on the relatively accurate model, the error of slip ratio estimated by the rotor rotary speed is analyzed in both time and frequency domains when a quarter car is started by the I-PMSM with a definite target torque input curve. In addition, the natural frequencies（NFs） of the driving wheel system with variable parameters are illustrated to present the relationship between the slip ratio estimation error and the NF. According to this relationship, a low-pass filter, whose cut-off frequency corresponds to the NF, is proposed to eliminate the error in the estimated slip ratio. The analysis, concerning the effect of the driving wheel parameters and road conditions on slip ratio estimation, shows that the peak estimation error can be reduced up to 75% when the LPF is adopted. The robustness and effectiveness of the LPF are therefore validated. This paper builds up the deformable tire model and the detailed I-PMSM models, and analyzes the effect of the driving wheel parameters and road conditions on slip ratio estimation.

A Fuzzy-based Sliding Mode Control Approach for Acceleration Slip Regulation of Battery Electric Vehicle

Due to quick response and large quantity of electric motor torque,the traction wheels of battery electric vehicle are easy to slip during the initial phase of starting.In this paper,a sliding mode control approach of acceleration slip regulation is designed to prevent the slip of the traction wheels.The wheel slip ratio is used as the state variable for the formulation of system dynamics model.The fuzzy algorithm is utilized to adjust the switch function of sliding mode controller.After stability and robustness analysis,the sliding mode control law is transferred into C code and downloaded into vehicle control unit,which is validated under wet and dry road conditions.The experimental results with a small overshoot and a quick response during starting indicate that the sliding mode controller has good control efect on the slip ratio regulation.This article proposes an acceleration slip regulation method that improves the safety during acceleration for battery electric vehicle.

轮毂式电动汽车电子差速复合控制方法

为实现轮毂式电动汽车在弯道的稳定转向,解决传统控制方法对汽车行驶速度的局限性,提出一种高-低速复合电子差速控制方法。当汽车处于低速行驶状态时,根据Ackermann转向模型获取驱动轮期望转速,提出一种模糊PID控制方法,实现轮速的稳定跟踪;当汽车处于高速行驶状态时,以驱动轮的相对滑移率作为反馈控制量,提出一种基于模糊逼近的滑移率优化控制方法,无需建立精确的系统状态空间模型,同时根据LQR理论保证了汽车驱动轮相对滑移率最小。Matlab/Carsim联合仿真证明,所提出的高-低速复合控制方法能够使汽车在不同行驶速度下实现稳定转向。

新型可拆卸式钢-UHPC组合板的抗弯性能

为探究钢-薄层超高性能混凝土(ultra-high performance concrete,UHPC)轻型组合桥面体系在局部轮载下的抗弯性能,设计并开展了4块基于高强螺栓连接的可拆卸式钢-UHPC组合板的四点弯曲试验,研究了钢板类型、抗剪连接件间距对可拆卸式钢-UHPC组合板的破坏模式、荷载-挠度曲线、界面相对滑移、裂缝宽度、截面应变分布等影响规律,研究结果表明:在正弯矩荷载作用下,采用Q355钢板的组合板的破坏模式为高强螺栓被剪断,而采用负泊松比(negative Poisson’s ratio,NPR)钢板的组合板的破坏模式为部分高强螺栓被剪断、部分预埋带垫加长螺母被拔出、UHPC板由于失稳大面积压溃等;在相同的高强螺栓间距下,采用NPR钢板的组合板的板端相对滑移较小,说明NPR钢板有效延缓并限制了钢板与UHPC板的相对滑移,从而提升两者的协同变形能力,继而提高组合板的抗弯刚度及承载力等;由截面应变分析可知,由于NPR钢板的负泊松比效应、高刚度、高屈服强度,整个加载过程NPR钢板与底部UHPC层的拉应变保持着应变协调性,随着荷载的增大截面塑性中和轴的上移幅度可忽略不计。因此,在采用NPR钢板提升钢-UHPC组合板抗弯性能的前提下,应使UHPC厚度与NPR钢板的性能进行匹配,充分发挥两者的材料性能,避免失稳破坏先于UHPC材料强度破坏。

弹性环式挤压油膜阻尼器一体化圆柱滚子轴承保持架振动特性分析

航空发动机主轴中滚动轴承为了降低系统振动经常与弹性环式挤压油膜阻尼器(elastic ring squeeze film damper, ERSFD)联合使用。基于滚动轴承动力学理论和流体力学控制方程,采用变步长积分算法建立圆柱滚子轴承与ERSFD耦合的动力学分析模型,对外圈带ERSFD的圆柱滚子轴承保持架振动特性和打滑率进行研究。研究结果表明:与未装配ERSFD的圆柱滚子轴承相比,ERSFD可以提高圆柱滚子轴承保持架的稳定性。过大或过小的弹性环凸台数量与宽度都不利于圆柱滚子轴承保持架的稳定性,需要选择合适的凸台数量和宽度。径向载荷与转速对带弹性环的圆柱滚子轴承保持架稳定性影响显著,保持架涡动频率的谐波次数随着径向载荷的增加而减少,其对应的幅值也减小;保持架涡动频率的谐波次数随着转速的增加而增加,其对应幅值也增加。

基于预设性能的飞机全电刹车系统滑模控制

针对飞机全电防滑刹车系统具有较强的非线性特征,以及机电作动器(EMA)中存在的干扰不利于系统稳定性,提出一种有限时间预设性能反演滑模控制方法。在合理简化的基础上,建立含滑移率子系统和EMA子系统的飞机全电防滑刹车系统的数学模型,并引入有限时间预设性能函数;利用预设性能反演控制方法设计滑移率控制器,获得参考刹车压力控制率,保证滑移率跟踪误差在有限时间内收敛到预设范围内;为跟踪参考刹车压力,利用非奇异终端滑模控制方法设计EMA控制器,针对EMA中存在的干扰,设计扩张状态观测器估计,并在控制器中进行补偿,提高控制器的鲁棒性和控制精度;通过干跑道和冰跑道2种情况下的数值仿真验证所提方法控制效果。

滚刀滑移状态下的受力与磨损仿真分析

为探究滚刀滑移状态下破岩的受力与磨损的变化规律,基于离散单元法,建立了同时考虑滚刀自转和绕刀盘公转的滚动圆周切割模型。定义了一个滑移率参数η用于描述滚刀的滑移状态,对不同滑移率工况下滚刀破岩受力和磨损进行了对比分析,并结合工程实例对数值仿真结论进行了验证,结果表明:数值仿真中垂直力F_(V)和滚动力F_(R)在CSM模型计算值附近波动,两者较为吻合,表明了本文模型的合理性。数值仿真结果表明,随着滑移率η的增大,垂直力F_(V)呈轻微减小趋势,滚动力F_(R)明显变大,从滚动破岩到滑动破岩,垂直力F_(V)降幅为23.6%,滚动力F_(R)增幅达83.7%,滑动破岩将导致滚刀偏磨。工程实测数据表明,刀盘上大量滚刀处于正常磨损状态时,主要表现为推力增大。大量滚刀处于偏磨状态时,主要表现为扭矩增大,其中偏磨滚刀占比19.05%和28.57%时,扭矩增幅分别为55.85%和261.51%。滚刀正常磨损和偏磨均大量存在时,表现为扭矩推力同步增大,其中偏磨滚刀占比21.43%时,扭矩增幅为80.89%。数值仿真和实测数据表现出较高的一致性。综合4次开仓换刀结果,可将刀盘扭矩增幅超过50%作为判定大量滚刀发生偏磨的重要依据。

四驱电动汽车变附着路面行驶操稳性控制研究

针对四轮驱动电动汽车行驶时路面峰值附着系数和附着利用率变化的问题,提出利用直接横摆力矩控制提高操纵稳定性的控制策略。该策略采用分层控制,上层控制器负责目标车速的追踪、滑移率调整力矩的计算、以及根据行驶危险程度实现对质心侧偏角和横摆角速度的协调控制,下层控制器包括以轮胎利用率最优为目标的分配算法及集成滑移率控制的分配算法,根据滑移率大小实时切换。Carsim-Simulink联合仿真结果表明,在对开路面行驶时,相比于转矩平均分配控制策略,该控制策略能够使车辆具有良好操稳性的同时保持各车轮处于最佳滑移率区间内,有效改善了车辆性能。

ABS系统多路况下液压制动性能研究

ABS制动系统是保障汽车安全性能的重要部分,针对制动系统在制动过程中的非线性和时变性等问题,进行了汽车ABS控制策略对比研究。对直线制动过程进行研究分析,基于AMESim建立了单轮的防抱死液压系统,利用Simulink建立单车轮动力学模型,并采用以滑移率误差及变化率为输入的模糊PID控制策略和以制动力矩变化率为输入的自寻优控制策略。两种控制策略分别在单一干路面、湿路面和制动后1.5 s湿路面突变成干路面多路况,以车速为90 km/h进行ABS制动仿真,将制动结果进行对比。结果表明,模糊PID与自寻优两种控制方法能在制动过程中防止车轮抱死,自寻优控制方法不仅制动时间更短,而且能更好应对路况突变,验证了自寻优控制具有更强的鲁棒性和更佳的制动效果。

Analysis of torque transmitting behavior and wheel slip prevention control during regenerative braking for high speed EMU trains

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.

往复荷载作用下锈蚀钢筋与混凝土黏结性能研究

采用梁式试件进行25次往复荷载(25%、45%和65%极限荷载)作用下锈蚀钢筋(理论锈蚀率为2%、4%和6%)混凝土间黏结性能试验研究。结果表明:钢筋混凝土梁式试件均发生劈裂破坏;钢筋混凝土间的滑移在前十个往复荷载循环周期内基本完成,而后试件加载前后滑移差逐渐缩小,滑移量基本不再增加;在试件所受荷载等级一定时,试件加载端与自由端钢筋混凝土间的滑移随着锈蚀率增加而增大;而控制纵筋的锈蚀率不变,试件纵筋与混凝土之间自由端和加载端的滑移量随着荷载等级的提高而增加明显;往复荷载等级对于试件滑移量的影响较钢筋锈蚀相比更加明显。

Road identification method based on angular acceleration of vehicle driving wheel

The fundamental principle of road identification by using angular acceleration of driving wheels was demonstrated in this paper. Based on the analysis of energy conversion and parameters variation during the vehicle drive slip process, the change of adhesion coefficient relative to the an- gular acceleration were theoretically studied experimentally validated. The variation shows that the change of adhesion coefficient relative to the angular acceleration and the change of slip ratio in the drive slip process have same trend-both of them exist an only optimal angular acceleration corre- sponding to the peak value of adhesion coefficient. The peak adhesion coefficient of the prototype vehicle is about 0. 14 on the ice-covered road surfaces, with the corresponding optimal angular accel- eration of about 23.5 rad/s2 and optimal slip ratio of about 9. 4%.

Wheel slip-sinkage and its prediction model of lunar rover

In order to investigate wheel slip-sinkage problem, which is important for the design, control and simulation of lunar rovers, experiments were carried out with a wheel-soil interaction test system to measure the sinkage of three types of wheels in dimension with wheel lugs of different heights and numbers under a series of slip ratios (0-0.6). The curves of wheel sinkage versus slip ratio were obtained and it was found that the sinkage with slip ratio of 0.6 is 3-7 times of the static sinkage. Based on the experimental results, the slip-sinkage principle of lunar's rover lugged wheels (including the sinkage caused by longitudinal flow and side flow of soil, and soil digging of wheel lugs) was analyzed, and corresponding calculation equations were derived. All the factors that can cause slip sinkage were considered to improve the conventional wheel-soil interaction model, and a formula of changing the sinkage exponent with the slip ratio was established. Mathematical model for calculating the sinkage of wheel according to vertical load and slip ratio was developed. Calculation results show that this model can predict the slip-sinkage of wheel with high precision, making up the deficiency of Wong-Reece model that mainly reflects longitudinal slip-sinkage.

Slip Suppression of Electric Vehicles Using Sliding Mode Control Method

This paper presents a slip suppression controller using sliding mode control method for electric vehicles which aims to improve the control performance and the energy conservation by controlling the slip ratio of wheel. In this method, a robust sliding mode controller against the model uncertainties is designed to obtain the maximum driving force by suppressing the slip ratio. The numerical simulations for one wheel model under variations in mass of vehicle and road condition are performed and demonstrated to show the effectiveness of the proposed method.

复杂地面车辙识别试验与验证

火星表面地形地貌复杂,为了保证火星车行驶安全,需要对巡视器周边土壤的图像信息进行判别和分类。首先,根据试验场地和图像信息等对图像进行预处理,建立鸟瞰图像。接着,以鸟瞰图像为基础建立图像块并建立数据集,建模集和预测集分别包含315组和135组数据。然后,在划分的数据集基础上建立神经网络模型,并对数据进行训练和分类。最后,根据得到的分类模型对图像进行分类,得到感兴趣区域。分类结果表明:应用ResNet50得到的模型其建模集和预测集的分类准确率分别为75.56%和81.48%。该方法可实现巡视器周边地表类型的分类,并提取图像的感兴趣区域,以便实现更为精准的判别,可用于实现火星车通过性感知、风险预测和路径规划,为未来智能星球车移动系统研制和探测提供理论和技术支持。

一种基于μ-S模型的最佳滑移率辨识估计器设计

为了使基于滑移率识别的汽车防抱死控制器实现最优控制,在Kiencke μ-S模型的基础上,利用改进遗忘因子递推最小二乘算法设计了最佳滑移率辨识估计器,并将辨识估计器的最佳滑移率和峰值附着系数估算结果与Burckhardt μ-S模型下的结果进行了对比.将辨识估计器应用于汽车防抱死制动系统的模糊滑模控制器中,在单一路面和跃变路面条件下进行仿真实验.实验结果表明,辨识估计器的误差小、延迟小,基于最佳滑移率识别的防抱死控制器能实现最佳滑移率的在线辨识和快速追踪,有效提升制动效能.

火星车通过性评估技术现状与展望

火星表面地形地貌复杂,且覆盖有松软的火星土壤,这使得火星车在巡视探测时面临大沉陷、高滑转,甚至不能通过的风险。因此,火星车通过性分析和路径规划对巡视探测至关重要。本文调研了美国索杰纳号、勇气号、机遇号、好奇号、毅力号和我国祝融号火星车的通过性评估策略与方法,并分析基于多信息融合、深度学习和数据驱动的通过性评估研究新进展。最后,对未来火星车通过性判断发展方向进行了展望。

混动履带式无人平台轨迹跟踪控制研究

为了提高履带式无人平台的轨迹跟踪性能,提出了一种考虑纵向速度规划的分层轨迹跟踪算法并进行了联合仿真验证和实车验证。在建立了包含履带的滑移滑转率和质心侧偏角的车辆运动微分方程的基础上,完成分层轨迹跟踪算法框架的构建。上层基于伪谱法的速度规划算法根据路面信息进行纵向速度规划,并将规划的速度作为目标车速下发给下层基于线性时变模型预测控制(LTV-MPC)的轨迹跟踪算法。基于LTV-MPC的算法通过建立预测模型和约束条件,二次规划求解出两侧电机的目标转速。通过Matlab/Simulink和RecurDyn的联合仿真以及实车验证了所提出的算法在不同地面条件下具有良好的轨迹效果。