Estimation of Vehicle Speed Based on Wheel Speeds from ASR System in Four-Wheel Drive Vehicles

Three major methods currently in the use of determining vehicle speed based on wheel speeds, the minimum wheel speed, minimum wheel speed corrected by slope method and the Kalman filter method, are analyzed, with merits and defects of each approach stated. Through simulations, the Kalman filter method based on minimum wheel speed shows improved accuracy, in addition to better adaptivity to vehicle reference speed. It also can be used to acceleration ship regulation （ASR） in part-time four-wheel drive vehicles.

Effect of the off-road terrains on the ride comfort of construction vehicles

In order to evaluate the impact of off-road terrains on the ride comfort of construction vehicles,a nonlinear dynamic model of the construction vehicles interacting with the terrain deformations is established based on Matlab/Simulink software.The weighted root mean square(RMS)acceleration responses and the power spectral density(PSD)acceleration responses of the driver s seat heave,the pitch and roll angle of the cab in the low-frequency region are chosen as objective functions under different operation conditions of the vehicle.The results show that the impact of off-road terrains on the driver s ride comfort and health is clear under various conditions of deformable terrains and range of vehicle velocities.In particular,the driver s ride comfort is greatly affected by a soil terrain while the comfortable shake of the driver is strongly affected by a sand terrain.In addition,when the vehicle travels on a poor soil terrain in the frequency range below 4 Hz,more resonance peaks of acceleration PSD responses occurred than that on a rigid road of ISO 2631-1 level C.Thus,the driver s health is significantly affected by the deformable terrain in a low-frequency range.

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.

MPC-based Torque Distribution for Planar Motion of Four-wheel Independently Driven Electric Vehicles:Considering Motor Models and Iron Losses

The most critical obstacle for four-wheel independently driven electric vehicles(4WID-EVs)is the driving range.Being the actuators of 4WID-EVs,motors account for its major power consumption.In this sense,by properly distributing torques to minimize the power consumption,the driving range of 4WID-EV can be effectively improved.This paper proposes a model predictive control(MPC)-based torque distribution scheme,which minimizes the power consumption of 4WID-EVs while guaranteeing its tracking performance of planar motions.By incorporating the motor model considering iron losses,the optimal torque distribution can be achieved without an additional torque controller.Also,for this reason,the proposed control scheme is computationally efficient,since the power consumption term to be optimized,which is expressed as the product of the motor voltages and currents,is much simpler than that derived from the efficiency map.With reasonable simplification and linearization,the MPC problem is converted to a quadratic programming problem,which can be solved efficiently.The simulation results in MATLAB and CarSim co-simulation environments demonstrate that the proposed scheme effectively reduces power consumption with guaranteed tracking performance.

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.

Influences of the Suspension Parameters on the Vehicle Suspension Performance for a Terrain Vehicle

This paper describes an effective methodology for evaluation of the suspension parameters intended to be used for a terrain vehicle. The objective of this approach is to make quick analyses of the sensitivity of the vehicle suspension parameters. For the purpose of developing such a methodology, a mathematical modeling of a quarter vehicles suspension system is developed. Sensitive analysis of the suspension parameters is performed by employing the standard deviation of the vehicle body acceleration, dynamic tire load, and suspension travel. Sensitivity analysis results have shown that the spring stiffness, damping coefficient, tire stiffness and sprung mass have substantial influence on the ride comfort and road holding, while un-sprung mass on the other side has much lower impact in performance of the vehicle suspension system.

ATV(All Terrain Vehicle)全地形车

ATV解读ATV是All Terrain Vehicie的缩写,是一个极为宽泛的概念,意指'全地形车辆'。ATV不是汽车,但传统的越野汽车具备的功能它都有;ATV不是摩托车,但就发展渊源上与摩托车又不无关系。ATV演绎到今天,已经拓展出一个属于自己的庞大族群,与汽车、摩托车的'边界'并不清晰。由于国内对ATV的认知和接触较晚,

SOFT TERRAIN SPECTRUM CAUSING VEHICLE VIBRATION

The soft terrain spectrum is subdivided into three strands. i.e., the original spectrum,the effective spectrum and the rut spectrum. Accordingly, a device for measurements of all thesespetra is developed Based or its measuring results. a dynamic deformation model of theinteraction between vehicle and soft terrain and ancther modelof smoothing the enveloping pro-file of tyre contact area on soft terrain are proposed for further discussion of forming methanismof soft terrain spectrum which dominates vehicle vibration.

A new braking force distribution strategy for electric vehicle based on regenerative braking strength continuity

Regenerative braking was the process of converting the kinetic energy and potential energy, which were stored in the vehicle body when vehicle braked or went downhill, into electrical energy and storing it into battery. The problem on how to distribute braking forces of front wheel and rear wheel for electric vehicles with four-wheel drive was more complex than that for electric vehicles with front-wheel drive or rear-wheel drive. In this work, the frictional braking forces distribution curve of front wheel and rear wheel is determined by optimizing the braking force distribution curve of hydraulic proportional-adjustable valve, and then the safety brake range is obtained correspondingly. A new braking force distribution strategy based on regenerative braking strength continuity is proposed to solve the braking force distribution problem for electric vehicles with four-wheel drive. Highway fuel economy test(HWFET) driving condition is used to provide the speed signals, the braking force equations of front wheel and rear wheel are expressed with linear equations. The feasibility, effectiveness, and practicality of the new braking force distribution strategy based on regenerative braking strength continuity are verified by regenerative braking strength simulation curve and braking force distribution simulation curves of front wheel and rear wheel. The proposed strategy is simple in structure, easy to be implemented and worthy being spread.

A greedy path planning algorithm based on pre-path-planning and real-time-conflict for multiple automated guided vehicles in large-scale outdoor scenarios

With the wide application of automated guided vehicles(AGVs) in large scale outdoor scenarios with complex terrain,the collaborative work of a large number of AGVs becomes the main trend.The effective multi-agent path finding(MAPF) algorithm is urgently needed to ensure the efficiency and realizability of the whole system. The complex terrain of outdoor scenarios is fully considered by using different values of passage cost to quantify different terrain types. The objective of the MAPF problem is to minimize the cost of passage while the Manhattan distance of paths and the time of passage are also evaluated for a comprehensive comparison. The pre-path-planning and real-time-conflict based greedy(PRG) algorithm is proposed as the solution. Simulation is conducted and the proposed PRG algorithm is compared with waiting-stop A^(*) and conflict based search(CBS) algorithms. Results show that the PRG algorithm outperforms the waiting-stop A^(*) algorithm in all three performance indicators,and it is more applicable than the CBS algorithm when a large number of AGVs are working collaboratively with frequent collisions.

Primary safe criterion of earth-brushing flight for flying vehicle over digital surface model

In modern terrain-following guidance it is an important index for flight vehicle to cruise about safely and normally. On the basis of a constructing method of digital surface model (DSM), the definition, classification and scale analysis of an isolated obstacle threatening flight safety of terrain-following guidance are made. When the interval of vertical-and cross-sections on DSM is 12. 5 m, the proportion of isolated obstacles to the data amount of DSM model to be loaded is optimal. The main factors influencing the lowest flying height in terrain-following guidance are analyzed, and a primary safe criterion of the lowest flying height over DSM model is proposed. According to their test errors, the lowest flying height over 1:10 000 DSM model can reach 40. 5 m^45. 0 m in terrain-following guidance. It is shown from the simulation results of a typical urban district that the proposed models and methods are reasonable and feasible.

Application of unscented Kalman filter to novel terrain passive integrated navigation system

To improve the navigation accuracy of an autonomous underwater vehicle （AUV）, a novel terrain passive integrated navigation system （TPINS） is presented. According to the characteristics of the underwater environment and AUV navigation requirements of low cost and high accuracy, a novel TPINS is designed with a configuration of the strapdown inertial navigation system （SINS）, the terrain reference navigation system （TRNS）, the Doppler velocity sonar （DVS）, the magnetic compass and the navigation computer utilizing the unscented Kalman filter （UKF） to fuse the navigation information from various navigation sensors. Linear filter equations for the extended Kalman filter （EKF）, nonlinear filter equations for the UKF and measurement equations of navigation sensors are addressed. It is indicated from the comparable simulation experiments of the EKF and the UKF that AUV navigation precision is improved substantially with the proposed sensors and the UKF when compared to the EKF. The TPINS designed with the proposed sensors and the UKF is effective in reducing AUV navigation position errors and improving the stability and precision of the AUV underwater integrated navigation.

Terrain reconstruction from Chang'e-3 PCAM images

The existing terrain models that describe the local lunar surface have limited resolution and accuracy, which can hardly meet the needs of rover navigation,positioning and geological analysis. China launched the lunar probe Chang＇e-3 in December, 2013. Chang＇e-3 encompassed a lander and a lunar rover called ＂Yutu＂（Jade Rabbit）. A set of panoramic cameras were installed on the rover mast. After acquiring panoramic images of four sites that were explored, the terrain models of the local lunar surface with resolution of 0.02 m were reconstructed. Compared with other data sources, the models derived from Chang＇e-3 data were clear and accurate enough that they could be used to plan the route of Yutu.

扭转减振器式全地形车悬架系统设计及舒适性研究

为解决履带式全地形车辆舒适性及抗冲击性能差的问题,提出一种含弧弹簧阻尼结构的扭转减振器式悬架系统,设计了单负重轮悬架系统并开展动力学建模与舒适性分析,研究了不同工况下整车舒适性及抗冲击性能。研究发现:①单负重轮悬架系统静、动态特性参数值均在合理的范围内;相同路面车速增加时,单负重轮悬架系统车身垂向加速度和悬架动挠度均方根的相对增长率降低;路面等级、车速增加时,单负重轮悬架系统车身垂向加速度传递率(8.5%~6.5%)以较小的数值呈小幅下降趋势。②整车通过D、E级路面和极端路面时,所提悬架系统相对传统扭杆弹簧悬架系统表现出优良的舒适性和抗冲击性,验证了悬架设计方案的正确性和有效性。

基于无人机摄影测量的矿区地形三维重建及精度分析

矿区地形三维重建对于矿区地形分析及安全生产具有重要意义。针对传统重建方式存在效率低、数据更新速度慢、成本高等问题,提出了一种基于无人机摄影测量技术的矿区地形三维重建方法。该方法使用无人机进行低空拍摄,利用SIFT特征点匹配算法得到一系列匹配点,利用特征提取、空三测量、多视影像密集匹配技术,生成不规则三角网格和纹理映射,实现对矿区地形三维模型的自动重建。试验结果表明:在足够数量和合理选取地面控制点的情况下,所提方法可以获得较高精度的矿区地形三维重建结果;三维模型重建可以全面呈现矿区地形整体形态和局部细节特征,同时具有高效和低成本等优点。所提方法可为矿区环境保护及相关分析提供更准确、高效、可靠的地形信息数据源和技术支持。

基于轮力感知装置的软地面通过性测试系统

针对车辆的地面通过性试验方法主要局限于模型试验而缺乏实车试验的现状,提出了一套基于轮力感知装置的软地面通过性测试系统。系统以维轮力感知装置为核心,辅以轮速传感器、视觉传感器、GPS等多种车载设备。试验结果表明本文所提出的测试系统能够在多种软地面条件下完成牵引力、滑移率等通过性关键性指标的实时测量,进而为通过性地图的建立提供有力支撑。

利用前视和测高声呐的UUV地形跟踪动态路径生成方法

保持对海底地形的定高跟踪航行是无人水下航行器(UUV)执行海洋勘测和水下目标搜索任务时常采用的一种运动形式,其核心是UUV如何对未知起伏的海底地形进行实时探测,并基于探测信息在线、动态地生成跟踪路径,以实现对地形的定高跟踪航行,同时避免与地形发生碰撞。针对上述问题,提出了一种基于前视声呐探测地形信息、基于多项式拟合动态生成跟踪路径的方法。首先,UUV利用前视声呐对海底地形进行实时探测,对获得的地形探测数据进行仿射处理后,得到具有离散特性的定高仿射数据。然后,采用基于最小二乘准则的三次多项式方法对仿射数据进行拟合,生成基于多项式函数描述的UUV地形跟踪航行路径。最后,设计了一种包含声呐探测、数据仿射、路径生成和跟踪控制的动态执行框架,实现UUV的实时地形跟踪航行任务。文中所提出的跟踪路径生成和动态执行框架通过对典型的海底“上坡”地形和“山地”地形跟踪的仿真验证,证明了其有效性和可行性。

多足地形自适应起落装置关键技术与研究进展

多足地形自适应起落装置,作为垂直起降飞行器智能化发展的关键技术之一,对解决垂直起降飞行器的机轮式和滑橇式起落架存在野外复杂地形难以着陆及恶劣海况下着舰停靠困难的问题有着重要的意义。结合多足地形自适应起落装置的研究经验和现有成果,本文总结了地形自适应起落装置研制的关键技术,主要集中在腿部轻量化结构与驱动一体化技术、地形识别-腿部闭环控制-飞控系统的协同控制技术、机体集成与试验技术三个方面,分别对各项关键技术展开讨论,对现有研究方法与成果进行详细说明。在多足地形自适应起落装置的设计构型的基础上开展关键技术讨论,给出目前的研究进展,总结了目前阶段存在的不足与技术壁垒,并对该研究领域的未来发展方向进行了展望。

水下地形匹配导航研究综述

地形辅助导航系统以地形高程特征为定位信息源,可为水下航行器提供有界的定位误差,并能显著地抑制捷联惯性导航系统的误差漂移。而地形匹配算法是地形辅助导航系统的关键技术,其输出的匹配位置可作为组合导航滤波器的观测值以修正导航参数,地形匹配精度直接决定了整个导航系统性能。首先概述了现有水下导航定位技术,然后阐述了地形辅助导航基本原理与组成,最后详细总结了中外地形辅助导航系统和地形匹配算法的研究进展,为中国地形辅助导航系统的开发和研制提供有益参考和支撑。

An Integrated Control Framework for Torque Vectoring and Active Suspension System

Four-wheel independently driven electric vehicles(FWID-EV)endow a flexible and scalable control framework to improve vehicle performance.This paper integrates the torque vectoring and active suspension system(ASS)to enhance the vehicle’s longitudinal and vertical motion control performance.While the nonlinear characteristic of the tire model leads to a relatively heavier computational burden.To facilitate the controller design and ease the load,a half-vehicle dynamics system is built and simplified to the linear-time-varying(LTV)model.Then a model predictive controller is developed by formulating the objective function by comprehensively considering the safety,energy-saving and comfort requirements.The in-wheel motor efficiency and the power loss of tire slip are treated as optimization indices in this work to reduce energy consumption.Finally,the effectiveness of the proposed controller is verified through the rapid-control-prototype(RCP)test.The results demonstrate the enhancement of the energy-saving as well as comfort on the basis of vehicle stability.