Dynamic modeling and fuzzy logic control of vibrations of a railway vehicle for different track irregularities

Safe and comfortable transportation of passengers and goods on railways can be achieved by solving the vibration problem. In this study, the dynamic modeling of the full railway vehicle is used to perform vibration analysis in order to observe displacements and accelerations. The full railway vehicle model consists of 54 degrees of freedom which are defined by differential equations. Additionally, wheel–rail contact problem (i.e. creepage factors and hertzian spring stiffness of rails) is analyzed by finite element method. Dynamic modeling and vibration analysis are carried out using Matlab–Simulink software. Using the developed model, the car body vibrations, caused by a lateral and two vertical sinusoidal track irregularities, are controlled by fuzzy logic controllers placed between the car body and bogies. The fuzzy logic algorithm herein is used for realizing the active control of car body vibrations. The simulations of vibration analysis are obtained in time and frequency domains and compared with passive controlled status. The robustness of the designed controller is verified by simulations, carried out for the cases of car body mass variations. The results show the effectiveness of the proposed algorithm.     

Experimental Verification of a Drift Controller for Autonomous Vehicle Tracking: a Circular Trajectory Using LQR Method

This study develops an autonomous vehicle control method that enables it to perform a drift maneuver which is an expert driving technique consisting of sliding the rear wheel intentionally for fast cornering. By developing an autonomous control algorithm for such an agile maneuver, the safety of the future autonomous vehicle on extreme conditions such as slippery road, will be increased. Drift equilibrium states are derived to find the suitable feedforward control input for the scale car to enter the drifting region. In addition, a feedback controller is designed based on the linear quadratic regulator method in order to track the circular trajectory and maintain drift equilibrium states. To validate the performance of the developed control algorithm a 1:10 scale car experimental platform is developed with on-board control and sensor system. The feasibility of the developed method for the autonomous vehicle is confirmed through both simulation and experiments following circular trajectories while maintaining the desired equilibrium states.

     

多交互车辆轨迹预测研究

现有的车辆轨迹预测大多是单目标轨迹预测,无双向交互和关系推理,不能实现混合实体的交互建模。针对上述问题,结合强化学习的Q-learning算法和深度学习的LSTM网络,设计一个完全可扩展的轨迹预测模型Q-LSTM。该模型中,LSTM网络捕获了车辆轨迹的时间特性,而Q-learning算法则表示了多车辆的交互过程,因此Q-LSTM模型可以实现随机数量车辆多交互建模,并且在长期交互车辆轨迹预测中保证精确度。另外模型中考虑了车辆长宽与坐标之间的关系,避免出现异常的碰撞现象,适合用于多类型车辆轨迹预测的场景。在公开数据集HighD上进行了模型的性能分析实验,实验结果证明Q-LSTM模型在较长期交互车辆轨迹预测精度和减少碰撞现象等方面具有一定优势。     

Lateral acceleration potential field function control for rollover safety of multi-wheel military vehicle with in-wheel-motors

This article proposes an automatic longitudinal deceleration based method for multi-wheel vehicle rollover safety in autonomous mode. The information of lateral acceleration and vehicle roll angle is used to generate the longitudinal acceleration at which the vehicle will remain stable to rollover. The lateral and roll dynamics are coupled with longitudinal dynamics using a potential field function for lateral acceleration. This virtual potential field is developed on g-g diagram which represents vehicle portrait of lateral and longitudinal acceleration on abscissa and ordinate respectively. The motion of vehicle is represented by a point moving on this phase portrait of g-g diagram. TruckSim model of multi-wheel military vehicle with in-wheel motors is used with this algorithm which shows that the vehicle is less susceptible to rollover. The safe longitudinal acceleration is achieved by torque control of in-wheel motors fitted in each wheel. Using this method, the vehicle followed the desired trajectory as higher speeds which are safe. This is particularly useful for vehicle autonomous driving with rollover stability.

     

Path tracking controller design of four wheel independent steering automatic guided vehicle

This paper presents a new type of four wheel independent steering automatic guided vehicle (4WIS-AGV) for carrying heavy baggage and proposes a controller for the 4WIS-AGV to track reference trajectories. To do this task, the followings are done. Firstly, a 4WIS-AGV is designed and manufactured for experimental purpose. Secondly, a kinematic modeling for the 4WIS-AGV is introduced based on a single track vehicle model. Thirdly, based on the modeling, a controller is designed based on Backstepping method for the 4WIS-AGV to track reference trajectories. Fourthly, a control system is developed using industrial PC and AVR ATmega128 microcontrollers to implement the designed controller. Finally, simulations and experiments are conducted to verify the effectiveness and performances of the proposed controller in tracking two types of reference trajectories: a trajectory with sharp edges for parallel steering maneuver and a circular trajectory for zero-sideslip maneuver. The results show that the proposed controller can make the 4WIS-AGV track the trajectory with sharp edges and the circular trajectory very well.     

基于改进型目标重识别算法的高速公路车辆轨迹还原

针对高速公路场景下难以实现车辆轨迹精准还原的问题,提出以新近大规模建设的ETC门架系统作为检测载体,将车牌识别与车辆重识别(ReID)技术结合实现更好的轨迹还原效果.高速公路车辆目标多、速度快,常用目标检测算法难以满足属性检测与重识别要求的情况下,对多目标检测与重识别的FairMOT算法结构作出改进,添加多个并行头输出,对车牌、车辆颜色、类型、品牌及重识别等特征同时训练,输出车辆多标签属性;制作数据集并开发一套数据标注工具以满足多目标、多标签及重识别标注需求.实验表明,车牌识别准确率达到97.32％,车辆重识别rank-1为86.94％.采用车牌识别与ReID相结合的方式,车辆轨迹还原准确率超过85％,与ReID及车牌识别单独使用相比分别提高了14.8％与9.89％.该方法以27.5 fps的推理速度在高速公路车辆轨迹还原实践中取得了较好效果,也为智能算法在高速公路领域深化应用提供了实践基础.     

基于稀疏帧检测的交通目标跟踪

为了获取高速公路交通视频中目标车辆的行驶轨迹,提出一种基于视频的多目标车辆跟踪及实时轨迹分布算法,为交通管理系统和交通决策提供目标车辆交通信息.首先,使用YOLOv4算法检测目标车辆位置及置信度.其次,在不同场景条件下,使用提出的基于稀疏帧检测的跟踪方法,结合KCF跟踪算法,将车辆数据进行关联获取完整轨迹.最后,用车辆分布图和交通场景俯视图显示轨迹,便于交通管理与分析.实验结果表明,提出的跟踪方法在车辆跟踪中有较高的跟踪正确率,同时基于稀疏帧检测的跟踪方法处理速度也较快,实时轨迹分布正确反映了真实场景的车道信息以及目标车辆运动信息.     

MFB50 on-board estimation methodology for combustion control

Due to the increasing request for pollutant emissions reduction, modern closed-loop combustion control strategies require the on-board evaluation of the center of combustion (MFB50), i.e. the angular position where 50% of the injected fuel mass is burned. This work presents an MFB50 estimation algorithm based on engine speed measurement, that can be performed using the same toothed wheel already present on-board. Therefore, this approach is compatible with on-board application and requires no additional hardware cost. The complete methodology has been applied to a Diesel engine mounted on-board a vehicle and the accuracy of the obtained results is compatible with on-board requirements.     

Modelling of Torsion Beam Rear Suspension by Using Multibody Method

The multibody systems analysis has become one of the main simulation techniques to calculate the elasto-kinematics characteristics of a car suspension under wheel loads or to realize complex full vehicle models in order to predict the handling performances or the NVH quality. The modelling of torsion beam rear suspensions—widely adopted in cars belonging to B or C class—presents some problems arising from the structural behaviour of this component. A linear method based on component mode synthesis was used to represent the flexible torsion beam within the multibody model. This kind of approach was compared with a non-linear FE analysis. The elasto-kinematics analysis of the suspension was performed by using SIMPACK multibody code. The main suspension parameters (toe angle, camber angle, wheelbase and track variation) were calculated by changing wheel travel and loads. Static analyses, involving great displacements, were performed and a different number of modes were considered in the modal condensation of the torsion beam. The results of multibody simulations were compared with those obtained from a non-linear FE model. Different stiffness values of the bushings that connect the torsion beam to the vehicle chassis were taken into account.     

多车场满载车辆路径优化算法

针对多车场满载车辆路径问题(MDVRPFL),结合节约法提出了一种依次对车场、配送中心、用户进行循环调整直到最优的迭代算法.该算法具有使总费用随迭代次数逐渐降低的特点,其运算结果能同时得到最优车辆分配方案和车辆行驶路径.最后用该算法对不同规模的算例进行试验.试验结果表明,该算法对多车场车辆路径问题有效适用.     

Simultaneous braking and steering control method based on nonlinear model predictive control for emergency driving support

Autonomous emergency braking (AEB) has drawn a lot of attention as an active safety system preventing rear-end collision avoidance when the relative speed between vehicles is slow. To increase the operation range of current AEB system, this paper suggests a collision avoidance strategy using steering and braking simultaneously with nonlinear model predictive control (NMPC) method. The NMPC predicts the vehicle’s future trajectory with its open-loop dynamics and calculates the error between the predicted and the desired paths. Then NMPC calculates the control inputs such as the wheel steering angle and vehicle acceleration by optimizing the cost function over future receding horizon with predetermined constraints. In this paper, constraints on the wheel steering angle is proposed in consideration of vehicle’s predicted lateral acceleration, which should be smaller than the threshold in order to maintain lateral vehicle’s stability. To verify the performance of the proposed strategy, two simulation scenarios were tested in MATLAB and CarSim simulation environments.

     

Stochastic adaptive tracking for a rehabilitative training walker with control constraints considering the omniwheel touchdown characteristic

ABSTRACT

This article investigates the improvement of trajectory tracking on an omnidirectional rehabilitative training walker (ORTW) with random shifts in the centre of gravity, control constraints, and touchdown characteristics of omniwheels. Analysis of the touchdown characteristic improved the accuracy of the dynamic ORTW model. The control constraints guarantee the safety of the omniwheels and the ORTW training process. After describing the random centre-of-gravity shifts using Wiener process, an improved stochastic dynamic model was constructed. Under trajectory tracking control with adaptive technology, the ORTW followed the trajectory designed by the rehabilitation therapist. The exponentially practical stability in mean absolute of the tracking-error system was derived from stochastic theory and Markov's inequality. The effectiveness of the proposed methods was confirmed in simulations.     

Direct Method Based Control System for an Autonomous Quadrotor

This paper proposes a real time control algorithm for autonomous operation of a quadrotor unmanned air vehicle. The quadrotor is a small agile vehicle, which as well as being a excellent test bed for advanced control techniques could also be suitable for internal surveillance, search and rescue and remote inspection. The proposed control scheme incorporates two key aspects of autonomy; trajectory planning and trajectory following. Using the differentially-flat dynamics property of the system, the trajectory optimization is posed as a non-linear constrained optimization within the output space in the virtual domain, not explicitly related to the time domain. A suitable parameterization using a virtual argument as opposed to time is applied, which ensures initial and terminal constraint satisfaction. The speed profile is optimized independently, followed by the mapping to the time domain achieved using a speed factor. Trajectory following is achieved with a standard multi-variable control technique and a digital switch is used to re-optimize the reference trajectory in the event of infeasibility or mission change. The paper includes simulations using a full dynamic model of the quadrotor demonstrating the suitability of the proposed control scheme.     

Estimation of moving vehicle locations using wheel shape information in single 2-D lateral vehicle images by 3-D computer vision techniques

An approach to the estimation of moving lateral vehicle locations for driving assistance using wheel shape information in single 2-D vehicle images by 3-D computer vision techniques is proposed. The location scheme is supposed to be performed on a vehicle with a camera mounted on the front bumper. An analytical solution is applied to estimate locations of the lateral vehicle. Firstly, the rear wheel shape of a lateral vehicle moving in a nearby lane is imaged. By using the Hough transform, the projected wheel shape, which is an ellipse, is detected. Secondly, the equation of the detected ellipse is used to infer the orientation angle of the lateral vehicle with respect to the camera view direction. Finally, the center of the ellipse shape is used to determine the relative position of the lateral vehicle with respect to the camera lens center. Moreover, an edge-point verification algorithm is utilized to extract the ellipse shape more precisely in the image processing stage. Both computer simulated and real images are tested and good experimental results show the effectiveness of the proposed approach for estimating lateral vehicle locations. The results are useful for driving assistance and vehicle collision avoidance and are discussed in detail.     

基于轨迹段核密度的旅游车辆轨迹聚类算法

为了更好地研究旅游车辆的运营行为，需要通过分析车辆轨迹规律发现车辆运动的典型轨迹，轨迹聚类是其中重要的环节。对于使用传统的密度聚类方法处理大规模旅游车辆轨迹数据存在准确度差和效率低的问题，提出了一种基于轨迹段和核密度的轨迹聚类方法。采用核距离作为轨迹段相似度度量，利用类似DBSCAN算法对轨迹段进行聚类，得出旅游车辆运动典型轨迹。以北京市旅游车辆为例，采用基于轨迹段和核密度的算法对车辆轨迹进行聚类，能从一定程度上提高聚类的效果和准确率，为进一步研究旅游车辆的运营行为打下基础。     

Attitude determination algorithm using state estimation including lever arms between center of gravity and IMU

In this paper, an enhanced attitude determination algorithm is proposed to decrease the estimation error by including an additive state variable for the lever arm. Attitude determination generally is carried out by measurements from an IMU (inertial measurement unit), which is typically located at the center of gravity of the vehicle. The IMU lever arm, which spans the distance between the IMU and the center of gravity, causes extra acceleration in the accelerometer and increases the error in attitude estimates. However, if the extra accelerations caused by the lever arm can be removed from the measurements of accelerometers, the increased attitude error caused by the IMU lever arm can be prevented. Because an IMU lever arm is fixed in a vehicle after installation, it can be considered as an additive element of the state vector in Kalman filter for attitude determination. The proposed algorithm is composed of a quaternion-based Kalman filter and includes an estimation of the IMU lever arm. In addition, in order to determine components of lever arm, the gross measure of modal observability is investigated for the system. An evaluation of the proposed algorithm is carried out by simulations with a noise model based on an actual IMU. Evaluations through simulations show that the proposed algorithm improves the performance with regard to errors.     

Pedestrian tracking for infrared image sequence based on trajectory manifold of spatio-temporal slice

The research of pedestrian tracking in infrared image sequences is a curial part of video surveillance. Considering the particular characteristics of the infrared image, such as low contrast, fuzzy edge and unknown noises interference, the study of infrared pedestrian tracking algorithm becomes a great challenge. Spatio-temporal slice method is effective due to considering both spatial and time scale. It can extract the trajectory of moving targets, reflecting the trajectory manifold variations of targets along the time, to provide ways to depict the regions of targets. However, traditional spatio-temporal based methods only consider the horizontal slice analysis and usually require a large amount of calculation time; this paper proposes a spatio-temporal tracking algorithm to infrared image sequences, using both horizontal and vertical multi-layer slices to obtain the integral trajectory manifold. The integral trajectory is analyzed to obtain the target boundary and position information, with which the target can be tracked in each frame. The experimental results show that the proposed method has a relatively high tracking accuracy with a fast computing speed. Moreover, it can perform effectively in different infrared image sequences with various motion modes by single pedestrian from OTCBVS/05 Terravic Motion IR Database.

     

DV-Hop localization algorithm based on bacterial foraging optimization for wireless multimedia sensor networks

DV-Hop localization algorithm is a classic range free localization algorithm in wireless sensor networks (WSNs). Although easy to be employed in low cost and resource limited WSNs, DV-Hop localization algorithm suffers from low localization accuracy as the other range free localization approaches. To improve the localization accuracy, in this paper we introduce Bacterial Foraging Optimization (BFO), an efficient optimization method that has been widely applied in a variety of scientific and engineering applications. We conduct extensive simulations under different network setting, the simulation results demonstrate that the proposed algorithm achieves significantly higher positioning accuracy than the basic DV-Hop algorithm.

     

基于DSP的单车道车流量实时监测算法

针对传统的车流量检测系统采用感应器设备硬件安装繁杂及通用车流量检测算法无法判别车辆行驶方向的问题,提出一种基于数字信号处理器（DSP）的单车道车流量实时监测算法,并应用于停车场。首先,在虚拟检测带上使用背景差分法完成车辆检测,并对均值法背景建模进行改进;其次,提出一种邻帧二值归类算法对车辆行驶方向进行判别;最后,在虚拟检测带上进行车流量计数并将车位情况实时显示于LED显示屏上。通过模拟实验验证了所提算法的可行性,并在实际测试实验中,得到邻帧二值归类算法方向判别的准确率为96.5%,车位监控算法准确率为92.2%。实验结果表明,该单车道车流量实时监测算法准确率较高,节省了检测系统设备,可以应用于单车道停车场进行车流量实时监测。     

纬度未知条件下捷联惯导摇摆基座自对准方法

针对纬度未知条件下捷联惯导摇摆基座自对准问题,本文将其看作基于特征值分解的优化问题处理,提出一种基于地球系重力矢量的摇摆基座自对准方法.首先,构建基于速度增量形式的目标函数,建立不依赖外部纬度信息的地球系下重力矢量模型,以提高地球系下重力矢量的估计精度;然后,将摇摆基座自对准看作Wahba姿态确定问题,基于地球系下重力矢量建立关于惯性系转换四元数的速度增量式目标函数,增强对噪声及振荡干扰的抑制,利用基于特征值分解的多矢量优化方法完成摇摆基座自对准,以提高对准精度;最后,通过设置捷联惯导摇摆基座初始对准仿真及船舶系泊实验,验证了所提方法的有效性.