Adaptive Trajectory Tracking Control for Nonholonomic Wheeled Mobile Robots:A Barrier Function Sliding Mode Approach

The trajectory tracking control performance of nonholonomic wheeled mobile robots(NWMRs)is subject to nonholonomic constraints,system uncertainties,and external disturbances.This paper proposes a barrier function-based adaptive sliding mode control(BFASMC)method to provide high-precision,fast-response performance and robustness for NWMRs.Compared with the conventional adaptive sliding mode control,the proposed control strategy can guarantee that the sliding mode variables converge to a predefined neighborhood of origin with a predefined reaching time independent of the prior knowledge of the uncertainties and disturbances bounds.Another advantage of the proposed algorithm is that the control gains can be adaptively adjusted to follow the disturbances amplitudes thanks to the barrier function.The benefit is that the overestimation of control gain can be eliminated,resulting in chattering reduction.Moreover,a modified barrier function-like control gain is employed to prevent the input saturation problem due to the physical limit of the actuator.The stability analysis and comparative experiments demonstrate that the proposed BFASMC can ensure the prespecified convergence performance of the NWMR system output variables and strong robustness against uncertainties/disturbances.

Numerical Prediction of Ride Comfort of Tracked Vehicle Equipped with Novel Flexible Road Wheels

Enhancing ride comfort has always constituted a crucial focus in the design and research of modern tracked vehicles,heavily reliant on the driving system's performance.While the road wheel is a key component of the driving system,traditional road wheels predominantly adopt a solid structure,exhibiting subpar adhesion performance and damping effects,thereby falling short of meeting the demands for high-speed,stable,and long-distance driving in tracked vehicles.Addressing this issue,this paper proposes a novel type of flexible road wheel(FRW)characterized by a catenary construction.The study investigates the ride comfort of tracked vehicles equipped with flexible road wheels by integrating finite element and vehicle dynamic.First,three-dimensional(3D)finite element(FE)models of both flexible and rigid road wheels are established,considering material and contact nonlinearities.These models are validated through a wheel radial loading test.Based on the validated FE model,the paper uncovers the relationship between load and radial deformation of the road wheel,forming the basis for a nonlinear mathematical model.Subsequently,a half-car model of a tracked vehicle with seven degrees of freedom is established using Newton's second law.A random road model,considering the track effect and employing white noise,is constructed.The study concludes by examining the ride comfort of tracked vehicles equipped with flexible and rigid road wheels under various speeds and road grades.The results demonstrate that,in comparison to the rigid road wheel(RRW),the flexible road wheel enhances the ride comfort of tracked vehicles on randomly uneven roads.This research provides a theoretical foundation for the implementation of flexible road wheels in tracked vehicles.

Research on the strain gauge mounting scheme of track wheel force measurement system based on high-speed wheel/rail relationship test rig

Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approach-Finite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces.Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.Findings-The results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism,both tensile and compressive states exit on the surface of the web.When vertical force is applied,Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110mmof the web.Under lateral force,high Mises stress and strain are observed near the radius of 670mmon the inner and outer sides of the web.As the wheel-rail force application point shifts laterally toward the outer side,the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web.Under lateral force,the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point.Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces,the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force,while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/value-The research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.

Dynamic analysis of axle box bearings on the high-speed train caused by wheel-rail excitation

To explore the impact of wheel-rail excitation on the dynamic performance of axle box bearings,a dynamic model of the high-speed train including axle box bearings is developed.Subsequently,the dynamic response characteristics of the axle box bearing are examined.The investigation focuses on the acceleration characteristics of bearing vibration under excitation of track irregularities and wheel flats.In addition,experiments on both normal and faulty bearings are conducted separately,and the correctness of the model and some conclusions are verified.According to the research,track irregularity is unfavorable for bearing fault detection based on resonance demodulation.Under the same speed conditions,the acceleration peak of bearing is inversely proportional to the length of the wheel flat and directly proportional to its depth.The paper will contribute to a deeper understanding of the dynamic performance of axle box bearings.

Relationship between repeated triaxial test and Hamburg wheel tracking test on asphalt mixtures

Both the repeated triaxial test （RTT） and the Hamburg wheel tracking test （HWTT） are adopted to evaluate the high temperature performance of the stone mastic asphalt （SMA） and the mastic asphalt （MA）. The correlation of the permanent deformations of the MA and the correlation of the deformation developments of the SMA between the two tests are analyzed, respectively. Results show that both the two tests can effectively identify the high temperature performance of mixtures, and the correlation between the final results of the two tests as well as that between the deformation developments of the two tests are excellent with R20.9. In order to further prove the correlation, viscoelastic parameters estimated from the RTT results is used to simulate the rutting development in the HWTT slabs by the finite element method （FEM）. Results indicate that the correlation between the two tests is significant with errors less than 10%. It is suitable to predict the rutting development with the viscoelastic parameters obtained from the RTT.

Wheel-rail Profiles Matching Design Considering Railway Track Parameters

The profile of wheel/rail has great concern with the vehicle running safety, the wheel/rail wear and the rolling contact fatigue between wheel and rail, due to its severer impact on the dynamic behavior of both the railway vehicle/track, and the wheel/rail rolling contact status. However, recent studies in this respect are mainly explored in reverse methods, where track parameters are predetermined and invariable during the optimizing process. This paper attempts to propose a wheel-rail profiles matching design method considering multi-parameter, through optimizing wheel/rail profile under different rail cants and track gauges, based on the existed optimization technology for the normal gap of wheel/rail. The method presented in this paper can also, compared with the prior reverse methods, be called ＂forward solution method＂ in which the riding comfort, wheel unloading rate and wheel/rail contact stress of the speed-up railway passenger car are calculated by means of a vehicle-track coupling dynamic model, with the range of the rail cant varying from 1/20 to 1/40 and the rail gauge from 1 433 mm to 1 441 mm. These results show that the distribution status of the pairs of contact points can be obviously improved and the contact stress can be reduced significantly; a great influence is exposed by the rail cant and track gauge on the dynamic behavior of the high speed passenger car, and an optimal vehicle dynamics behavior are obtained with the optimized wheel/rail profile when the rail cant is 1/30 and the track gauge is 1 435 mm. This research can provide important references for the investigation of the wheel-rail profiles matching design method considering multi-parameter.

Mechanics analysis of a wheelchair robot with wheel-track coupling mechanism

A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.

Deep learning-based fault diagnostic network of high-speed train secondary suspension systems for immunity to track irregularities and wheel wear

Fault detection and isolation of high-speed train suspension systems is of critical importance to guarantee train running safety. Firstly, the existing methods concerning fault detection or isolation of train suspension systems are briefly reviewed and divided into two categories, i.e., model-based and data-driven approaches. The advantages and disadvantages of these two categories of approaches are briefly summarized. Secondly, a 1D convolution network-based fault diagnostic method for highspeed train suspension systems is designed. To improve the robustness of the method, a Gaussian white noise strategy(GWN-strategy) for immunity to track irregularities and an edge sample training strategy(EST-strategy) for immunity to wheel wear are proposed. The whole network is called GWN-EST-1 DCNN method. Thirdly, to show the performance of this method, a multibody dynamics simulation model of a high-speed train is built to generate the lateral acceleration of a bogie frame corresponding to different track irregularities, wheel profiles, and secondary suspension faults. The simulated signals are then inputted into the diagnostic network, and the results show the correctness and superiority of the GWN-EST-1DCNN method. Finally,the 1DCNN method is further validated using tracking data of a CRH3 train running on a high-speed railway line.

Adaptive trajectory tracking control of two-wheeled self-balance robot

Wheeled mobile robot is one of the well-known nonholonomic systems. A two-wheeled sell-balance robot is taken as the research objective. This paper carried out a detailed force analysis of the robot and established a non-linear dynamics model. An adaptive tracking controller for the kinematic model of a nonhotonomic mobile robot with unknown parameters is also proposed. Using control Lyapunov function （CLF）, the controller＇s global asymptotic stability has been proven. The adaptive trajectory tracking controller decreases the disturbance in the course of tracking control and enhances the real-time control characteristics. The simulation result indicated that the wheeled mobile robot tracking can be effectively controlled.

Interaction of subway LIM vehicle with ballasted track in polygonal wheel wear development

This paper develops a coupled dynamics model for a linear induction motor （LIM） vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen– Hedrick–Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system （LMS）, Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.

Track Tension Analysis of Four-Wheel Drive Tracked Vehicles

The distribution of track tension on track link is complex when the tracked vehicles run at a high speed.A multi-drive track link structure,which changes the traditional induction wheel into the driving wheel was proposed.The mathematical model of the system was established and the distribution of track tension was studied.The combined simulation model of RecurDyn and Simulink of the structure with multi-drive track was established.The simulation results show that our proposed structure has more uniform tension distribution than traditional structures,especially under the high speed condition.The maximum tension can be reduced by 28 kN-36 kN and the transmission efficiency can be improved by10%-16% under high speed condition with this new structure.

Real-time Non-linear Target Tracking Control of Wheeled Mobile Robots

A control strategy for real-time target tracking for wheeled mobile robots is presented.Using a modified Kalman filter for environment perception,a novel tracking control law derived from Lyapunov stability theory is introduced.Tuning of linear velocity and angular velocity with mechanical constraints is applied.The proposed control system can simultaneously solve the target trajectory prediction,real-time tracking,and posture regulation problems of a wheeled mobile robot.Experimental results illustrate the effectiveness of the proposed tracking control laws.

Calculation and Analysis for Temperature Field of Tank Track and Wheels

To know the temperature status of track and wheels on tank,the finite element calculation of temperature field was implemented with ANSYS software.The detailed temperature distributions for road wheel,drive wheel,idle wheel and track loop were obtained.The effect of factors,such as tank speed,environment temperature,sun radiant energy,ground deformation resistant and tank load,on the temperature of road wheel was studied.The sensitivity analysis shows that the effect of tank load on the temperature is the most,and the effect of ground deformation resistant is the least.The temperature testing device for road wheel on tank was developed to perform the experiments in real time.The calculated temperatures are in accord well with the experimental values.

Rutting Resistance of Asphalt Overlay with Multilayer Wheel Tracking Test

The rutting resistance of maltilayer asphalt overlay was researched by using laboratoty wheel tracking test. The effects of loading level and test temperature on rutting resistance of asphalt overlay structure were evahuaed by means of multilayer specimens . In comparison with multilayer tests, standard specimens of various layers were also conducted to evaluate the rutting resistance. Experimental results indicated that the test tempercature and applied load have a significant effect on rutting resistance of asphalt concrete. Higher test tempercature and heavier applied load resulted in higher rut depths. In addition, the mutilayer wheel tracking test has been demonstrated to be a more reasonable solution in evaluation on rutting resistance of asphatt pavement structure beasuse it reflects the cumulative permanent deformation in all of asphalt layers.

Embedded System Development for Detection of Railway Track Surface Deformation Using Contour Feature Algorithm

Derailment of trains is not unusual all around the world,especially in developing countries,due to unidentified track or rolling stock faults that cause massive casualties each year.For this purpose,a proper condition monitoring system is essential to avoid accidents and heavy losses.Generally,the detection and classification of railway track surface faults in real-time requires massive computational processing and memory resources and is prone to a noisy environment.Therefore,in this paper,we present the development of a novel embedded system prototype for condition monitoring of railway track.The proposed prototype system works in real-time by acquiring railway track surface images and performing two tasks a)detect deformation(i.e.,faults)like squats,shelling,and spalling using the contour feature algorithm and b)the vibration signature on that faulty spot by synchronizing acceleration and image data.A new illumination scheme is also proposed to avoid the sunlight reflection that badly affects the image acquisition process.The contour detection algorithm is applied here to detect the uneven shapes and discontinuities in the geometrical structure of the railway track surface,which ultimately detects unhealthy regions.It works by converting Red,Green,and Blue(RGB)images into binary images,which distinguishes the unhealthy regions by making them white color while the healthy regions in black color.We have used the multiprocessing technique to overcome the massive processing and memory issues.This embedded system is developed on Raspberry Pi by interfacing a vision camera,an accelerometer,a proximity sensor,and a Global Positioning System(GPS)sensors(i.e.,multi-sensors).The developed embedded system prototype is tested in real-time onsite by installing it on a Railway Inspection Trolley(RIT),which runs at an average speed of 15 km/h.The functional verification of the proposed system is done successfully by detecting and recording the various railway track surface faults.An unhealthy frame’s onsite detection processing time was recorded at approximately 25.6ms.The proposed system can synchronize the acceleration data on specific railway track deformation.The proposed novel embedded system may be beneficial for detecting faults to overcome the conventional manual railway track condition monitoring,which is still being practiced in various developing or underdeveloped countries.

The effect of track alignment irregularity on wheel-rail contact geometry relationship in a turnout zone

The irregularity is a key factor affecting the wheel-rail contact geometry relationship. In this paper, we calculated the wheel-rail contact points at typical sections and obtained the longitudinal variation of the wheel-rail geometry relationship with the trace line method. The profile of the key rail sections was matched by cubic spline curve, and the shape interpolation was realized in non-controlling sections. The results show that the roll angles at each typical section increases gradually with the enlargement of track alignment irregularity. When the flange contact occurs, the roll angle increases dramatically. Proper track alignment irregularity towards the switch rail improves the structure irregularity of the turnout.

具有不确定滑转的轮式移动机器人轨迹跟踪控制方法

轮式移动机器人在松软复杂地形条件下容易发生车轮滑转,影响轨迹跟踪精度.为提高机器人在该情况下的轨迹跟踪准确性,提出了一种基于容错控制的自适应滑转补偿控制器.首先,考虑车轮滑转率建立了四轮移动机器人运动学模型,并构建了相应的轨迹跟踪误差模型;然后,根据容错控制方法设计了滑转补偿项,并基于Lyapunov稳定性理论证明了自适应滑转补偿控制器的稳定性,实现了对由车轮滑转引起的速度误差的准确补偿;最后,利用四轮移动机器人进行了两种工况下的实验验证.结果表明,设计的控制器能够使移动机器人在未知的车轮滑转率条件下准确跟踪理想路径,并且相较于常规控制器有更强的鲁棒性和更高的跟踪精度.

地面机动平台可重构轮履复合推进机构研究现状与展望

可重构轮履复合推进机构兼具轮式推进机构的快速性和履带推进机构的通过性,是提高地面机动平台在极端地形上综合性能的关键技术,在各类机器人和特种车辆上都得到了一定应用.文中在系统调研国内外相关文献的基础上,按轮履构型重构互换原理对推进机构进行分类,着重对比分析了不同构型的结构特点和应用场景,指出了可重构轮履复合推进机构的主要技术难点和发展前景.

基于交叉迭代法的车辆-轨道非线性空间耦合振动模型及算法改进

针对车辆-轨道非线性空间耦合系统动力学分析计算量大、计算耗时长及计算精度难以保证的问题,对车辆-轨道非线性空间耦合振动模型和交叉迭代法进行改进。运用有限元法分别建立车辆和轨道空间子系统动力学模型,在基于“迹线法”构建轮轨接触几何关系的基础上,提出“投影对点作差法”搜索轮轨空间接触点位置,并引入轮轨准弹性接触对其进行修正,精细化轮轨接触关系;结合车辆-轨道非线性空间耦合系统特点,改进基于Newmark数值积分的交叉迭代求解系统动力学方程的算法,并给出完整的数值计算步骤。通过与相关文献进行对比,验证改进模型和算法的有效性。结果表明:改进模型的分析精度更高,搜索轮轨空间接触点位置的速度更快;改进算法的计算过程更完善,步骤更清晰;改进的模型和算法在提高计算精度的同时,仍然具有较快的计算效率,且使数值编程更易实现,方便工程应用。

自动泊车前轮转角闭环的分层控制方案

为提高自动泊车系统中控制器的抗扰动能力,优化控制律执行效果,提出了前轮转角闭环的分层控制方案.设计了以行驶距离为非时间参考量的fal函数非光滑控制律,输出前轮转角控制量.以阿克曼转向模型为基础,建立了前轮转角观测器,并使用模糊滑模控制器实现前轮转角闭环的横向控制.搭建Carsim/Simulink联合仿真系统,在典型泊车场景下验证所设计控制器的有效性、跟踪效果及鲁棒性.使用实车测试平台开展了试验.结果表明:所设计的前轮转角闭环分层控制方案能够快速准确地跟踪目标路径,提高了泊车系统的横向控制精度,并在未知转向非线性扰动下也具有良好的跟踪控制效果.