A Hybrid Path Planning Method Based on Articulated Vehicle Model

Due to the unique steering mechanism and driving characteristics of the articulated vehicle,a hybrid path planning method based on the articulated vehicle model is proposed to meet the demand of obstacle avoidance and searching the path back and forth of the articulated vehicle.First,Support Vector Machine(SVM)theory is used to obtain the two-dimensional optimal zero potential curve and the maximum margin,and then,several key points are selected from the optimal zero potential curves by using Longest Accessible Path(LAP)method.Next,the Cubic Bezier(CB)curve is adopted to connect the curve that satisfies the curvature constraint of the articulated vehicle between every two key points.Finally,Back and Forth Rapidly-exploring Random Tree with Course Correction(BFRRT-CC)is designed to connect paths that do not meet articulated vehicle curvature requirements.Simulation results show that the proposed hybrid path planning method can search a feasible path with a 90-degree turn,which meets the demand for obstacle avoidance and articulated vehicle back-and-forth movement.

Design of a Preview Controller for Articulated Heavy Vehicles

The paper presents a preview controller design for ATS （active trailer steering） systems to improve high-speed stability of AHVs （articulated heavy vehicles）. An AHV consists of a towing unit, namely tractor or truck, and one or more towed units which called trailers. Individual units are connected to one another at articulated joints by mechanical couplings. Due to the multi-unit configurations, AHVs exhibit unique unstable motion modes, including jack-knifing, trailer swing and rollover. These unstable motion modes are the leading cause of highway accidents. To prevent these unstable motion modes, the preview controller, namely the LPDP （lateral position deviation preview） controller, is proposed. For a truck/full-trailer combination, the LPDP controller is designed to control the steering of the front and rear axle wheels of the trailing unit. The calculation of the corrective steering angle of the trailer front axle wheels is based on the preview information of the lateral position deviation of the trajectory of the axle center from that of the truck front axle center. Similarly, the steering angle of the trailer rear axle wheels is calculated by using the lateral position deviation of the trajectory of the axle center from that of the truck front axle. To perform closed-loop dynamic simulations and evaluate the vehicle performance measure, a driver model is introduced and it ＇derives＇ the AHV model based on well-defined testing specifications. The proposed preview control scheme in the continuous time domain is developed by using the LQR （linear quadratic regular） technique. The closed-loop simulation results indicate that the performance of the AHV with the LPDP controller is improved by decreasing rearward amplification ratio from the baseline value of 1.28 to 0.98 and reducing transient off-tracking by 95.03%. The proposed LPDP control algorithm provides an alternative method for the design optimization of AHVs with ATS systems.

MODALS RELATED TO STABILITY AND COMFORTABILITY OF ARTICULATED VEHICLE

An articulated vehicle is simplified as a multibody system. tires are simplified asparagraphic linear springs with damping, and the differential equations of system motion aregiven. Taking the ZL10 loader as an example, and measuring three-dimensional dynamicstiffness and damping of the tires, seven orders of natural frequencies and related natural modesare obtained by modal analysis, and shown on the computer with three-dimensional moving pic-tures. The following conclusions are obtained: the first order frequency relates to the horizontalstability, the second order frequency relates to the vertical stability, and each order of frequencyrelates to the comfortability. All results of this work can be applied .to monitor stability and eval-uate comfortability.

Mechanical-Hydraulic Co-Simulation of Full Hydraulic Articulated Steering System

With the development and improvement of the hydraulic steering system,the articulated steering system became the research focus of numerous domestic and foreign scholars.The full hydraulic steering system with a compact structure and ease of operation,is widely used in articulated steering mode.Furthermore,its performance can directly impact the steering sensitivity and stability.This paper studies the working principle and actual structure of the priority valve and the steering control valve,which are very important.By setting up a mathematic model,the system’s load-sensing characteristics and the impact of steering control valve bypass throttle damping on steering stability can be analyzed.The Hydraulic Components Design(HCD)model was established for the hydraulic part of this system.It is proved that the model can reflect the system’s actual properties by comparing simulation and experimental results.The dynamic model is based on its actual prototype parameters by taking the tire and ground forces into account.The steering process’s dynamic characteristics are co-simulated in the 1D+3D system model by combining AMESim and Virtual.Lab Motion.The simulation results show that the system’s load-sensing characteristics ensure the sensitivity of the steering operation,and the bypass throttle damping has significantly improved the operation stability and lowered down the cylinder pressure fluctuations.This can improve the system performance by appropriate optimization.

四旋翼无人机滑模-CPCMAC联合控制半物理仿真系统

针对四旋翼无人机强耦合、欠驱动、非线性等特点,以及在实际飞行过程中极易受到干扰的问题,对四旋翼无人机动力学模型进行分析,提出了一种基于联合的四旋翼无人机姿态控制算法,并在此基础上设计了四旋翼无人机半物理仿真系统。首先,针对非线性系统设计滑模控制器,选择跟踪航迹和翻滚角设计位置控制率和姿态控制率。其次,滑模控制器在实际应用中易产生震荡,利用基于信用积分的小脑模型神经网络(CPCMAC)来学习滑模控制的方式。最后,搭建基于LabVIEW的控制站,同Matlab/Simulink进行数据收发控制。仿真结果表明,在跟踪目标相同时,提出的四旋翼无人机滑模-CPCMAC联合控制相比于传统的比例积分微分(PID)控制和积分反步法控制优势明显,能够抑制超调和余差,在快速性和鲁棒性方面都更加优越。同时,构建的四旋翼无人机半物理仿真平台能清晰反馈出无人机参数的变化,应用预留的参数接口和地面控制站,降低了无人机飞控算法的开发难度,提高了开发效率,具有明显的实用价值。

基于应变测试矿用汽车车架结构优化设计分析

矿用铰接车采用液压举升机构实现货物卸载,受力情况复杂,对车架结构影响大且要求高。针对某自卸车后车架和货箱在不同运行条件下的承载特性进行分析,获取各工况的载荷情况和边界条件;根据前述分析,建立后车架和货箱的有限元分析模型,选取多个典型工况开展分析,获取应力应变的分布情况;采用材料升级、圆角优化及焊接工艺提升等,针对应力集中和较大位置进行优化设计,降低应力值,保证安全裕度满足要求;采用直角应变测试法,针对实际自卸车车架开展应力测试,在分析的关键位置布置应变片,选取典型工况开展测试,并与仿真结果开展对比。结果可知:自卸车铰接点和液压举升缸鹅颈支撑处应力较大,并且出现了应力集中,但均在许可范围之内;采用厚度提升、直径增大及焊接工艺提升等方法,有效提升应力分布,最大值明显降低;实车测试和仿真分析,满载工况应力分布基本一致,最大值误差低于5.8%;优化后结果明显低于优化前;结果表明分析模型和优化方法的可靠性,为此类分析设计提供参考。

多铰接车辆路径跟踪控制及仿真分析

针对多铰接车辆的车身结构限制了车辆的灵活性,导致后车在行驶过程中容易出现路径偏移的问题,提出一种以理想铰接角为控制目标的前馈加反馈路径跟踪控制方法,通过最小化理想与实际铰接角的偏差来实现后车对期望路径的准确跟踪。根据车辆和期望路径的几何位置关系,从适用范围和误差累积两个角度改进了传统的理想铰接角计算方法;基于车辆理想铰接角,考虑了控制方法的适用范围,设计了不依赖具体模型的前馈加径向基(RBF)神经网络PID反馈控制器;搭建了TruckSim和MATLAB/Simulink多铰接车辆联合仿真平台,比较分析了不同工况下车辆的路径跟踪性能。仿真结果表明:所提方法对不同工况具有良好的适用性和较高的跟踪精度,有效地降低了后车的误差累积。

紧急制动工况下虚拟轨道列车车间铰接力研究

围绕一种新型多轴铰接式城市轨道交通工具——虚拟轨道列车,针对路面附着条件变化会造成轮胎制动力不足、车轮抱死和车间铰接力增大的问题,提出了一种考虑路面附着系数的列车自动紧急制动策略.首先,采用扩展卡尔曼滤波和模型预测控制原理设计了上层控制器,基于实时估计的路面附着系数、列车制动舒适性和安全性,确定列车期望制动加速度;其次,基于轴荷比例分配原则和PID反馈补偿控制原理设计了下层控制器,根据列车期望制动加速度确定列车各轮胎的制动力矩;最后,搭建了Matlab/Simulink与Trucksim联合仿真平台,研究了列车制动过程中车间铰接力变化情况.结果表明,列车载重、制动初始车速以及路面附着系数变化对车间最大铰接力有影响;本文的制动策略具有良好的鲁棒性,在不同工况下能够有效防止车轮抱死、减小最大铰接力,提高列车制动过程中的舒适性和安全性.

三联关节平车在扭曲线路上的安全性分析

通过SIMPACK软件建立三联关节平车动力学仿真模型,基于AS标准规定的轨道扭曲形状参数搭建扭曲线路进行仿真计算,分析三联关节平车在通过扭曲线路时的安全性能。研究结果表明,所评估车轮最大减载量满足要求,可以安全通过标准规定的扭曲线路。

基于PXI实时平台铰接式车辆转向轨迹特性分析

根据双油缸“缸体前置式”布置的地下矿用铰接车转向系统的结构特点,获取油缸行程和整车转向角度之间的关系,并对转向过程中前后轮的坐标位置进行分析,获得数学模型。基于Simulink搭建分析模型,获得不同运行速度时的转向轨迹。基于ADAMS建立某铰接车的多自由度分析模型,与转向轨迹模型结合,嵌入PXI驾驶员在环测试实时平台,对整车的转向轨迹进行分析;基于实车测试,选取双移线转向工况,根据结果对仿真结果进行验证。分析可知:车辆运行速度低于6m/s时,行驶稳定性良好,转向过程比较平缓;当速度高于6m/s时,应该先减速,当到达适合转向行驶的速度再实施转向动作;驾驶员在环实时测试模拟、数学模型与实车测试获得转向轨迹,具有较高的重合度,转向角的误差小于3%,进一步地说明转向轨迹分析的准确性,为实际设计提供参考。

无人驾驶铰接转向车辆路径跟踪控制研究综述

路径跟踪是无人驾驶技术的重要组成部分,是实现铰接转向车辆准确平稳自主行驶的关键,对提高铰接转向车辆在农业、林业、矿山及建筑等行业的作业效率和安全性具有重要意义。车辆模型构建、控制算法设计和算法验证评估是路径跟踪控制研究的基础,围绕这3方面阐述了铰接转向车辆路径跟踪控制研究的进展。首先回顾了铰接转向车辆的几何学模型、运动学模型和动力学模型,并讨论了各类模型在路径跟踪控制研究中的适用场景及局限性;在此基础上,阐述了铰接转向车辆路径跟踪控制算法的研究现状,对比并总结了每种算法的优缺点及适用范围,并进一步归纳了算法的验证与评估手段;最后展望了铰接转向车辆路径跟踪技术未来的研究重点及方向:考虑车辆动力学因素及模型参数动态时变特性的车辆建模研究;融合各类算法适应性并结合智能算法的多工况自适应控制算法设计;标准化、流程化的高保真仿真场景开发及集成准确性、稳定性、安全性等多性能的评估方法研究。

基于横摆运动补偿的煤矿重载铰接车辆主动电液转向控制研究

煤矿重载铰接车辆采用折腰转向,横向刚度弱且所受扰动因素复杂,操控难度加大,极易引起安全事故。为改善煤矿重型铰接车辆在湿滑低附着路面环境中的安全驾驶操控性能、进一步提升煤矿辅助运输智能化水平,设计了一种具有横摆运动反馈补偿功能的泵控电液动力转向系统。建立了包含前车体纵向、侧向、横摆及后车体横摆运动在内的铰接车辆4自由度车体动力学模型以及泵控电液转向系统数学模型,在解耦动力学模型横摆角速度与横向加速度的基础上,设计了“转向操纵跟随−横摆稳定补偿”双通道铰接转向控制策略,其中,转向操纵跟随通道可实现前后车体铰接角对驾驶员的转向操控输入的实时跟踪,而横摆稳定补偿通道则通过主动调节车体铰接角以确保实际横摆角速度逼近理想横摆角速度。通过设置预滤波器和衰减积分器,设计了主动转向控制系统,该系统通过调整转向角度来提供纠正作用,以确保车辆能够遵循驾驶员意图保持路径跟随。基于dSPACE/DS1007半实物仿真平台,对铰接矿车低附着转向工况进行了仿真测试;模拟J型转弯工况,选择低摩擦因数路面条件中低速运行,验证了主动控制器对于铰接车辆跟踪期望路径的有效性。同时,基于冰雪覆盖路面等效低附着系数路面的实验条件,利用煤矿井下25 t级重型铰接式支架搬运车进行了实车转弯实验;结果表明:建立的铰接车辆车体动力学模型和泵控电液转向系统模型,通过横摆角速度与横向加速度进行解耦,能够比较真实的反应该类车辆的折腰运动状态;基于铰接车辆横摆稳定性控制分析,制定的“转向操纵跟随−横摆稳定补偿”双通道铰接转向控制策略,以及设计的主动控制系统,能够有效提高铰接车辆在低附着路面工况下的横摆稳定性,且该系统对于驾驶员的驾驶感觉没有改变,主动控制干预后能够及时、安全、平稳地将车辆的驾驶权交还给驾驶员。

轮式铰接工程车辆转向系统结构的优化

轮式铰接工程车辆以其良好的机动性和通过性,广泛应用于农业、建筑、矿场等复杂路况环境。转向系统作为铰接车的重要组成系统之一,其油缸等结构位置及布置方式直接影响车辆转向稳定性及轻便性。为提高铰接转向车辆转向性能,首先,在多体动力学仿真软件ADAMS中建立了某铰接转向车辆模型,并通过实车平顺性实验验证了所建模型的准确性。其次,以转向油缸与前后车体连接点及车辆铰接点位置坐标为设计变量,以油缸伸缩比、铰接角为约束条件,同时考虑转向油缸不发生运动干涉。最后,通过ADAMS和isight联合仿真方法,利用多岛遗传算法对设计变量进行优化并得到优化解集,优化结果表明,相同油缸压力条件下最大折腰角、最大行程差、最大力臂差等目标参数均得到了较大提升。

矿用分布式驱动铰接车辆差速控制策略研究

针对矿用分布式驱动铰接车辆在转向时容易打滑的问题,提出一种基于PID滑模控制的电子差速控制策略。建立了分布式驱动铰接车辆的动力学模型和基于运动学模型的滑移率计算模块,基于PID滑模面和指数趋近律设计了PID滑模控制器。通过MATLAB/Simulink对分布式驱动铰接车辆转向工况进行了仿真。结果表明:基于PID滑模控制的差速控制策略在小角度和大角度转向工况下内外侧车轮均具有良好的差速性能,即使部分车轮进入低附着路面,车轮滑移率也有效调控在0.2附近。该差速控制策略可以有效减少打滑,减轻轮胎磨损,对于提高矿用分布式电驱动铰接车的稳定性与动力性具有重要意义。

铰接列车最小转弯直径测量方法研究

本文通过研究铰接列车最小转弯直径理论计算方法和国内外相关测量标准,提出铰接列车最小转弯直径测量方法。试验证明此方法是可行的。

铰接农用车路径跟踪控制算法研究

针对铰接农用车在变附着系数路面条件下的路径跟踪精度难以保证的问题,提出了引入侧滑补偿的非线性模型预测控制(Nonlinear Model Predictive Control,NMPC)算法。首先,构建了考虑侧滑补偿的铰接农用车二自由度运动学模型,并基于该模型在Simulink中构建了NMPC控制器,最后以Adams环境中的虚拟铰接农用车为被控对象,以农业典型的地头转弯路径为参考路径,开展了变附着系数路面条件下的试验验证。结果表明,该算法的跟踪误差最大约为0.03 m,能够实现铰接农用车在变附着系数路面下的高精度路径跟踪。

一种针对铰接转向车辆的状态预测方法

车辆状态预测对于风险评估以及规划控制意义重大。提出了一种用于铰接转向车辆的状态预测方法。首先构建了模型预测控制器,并根据控制信息设计了虚拟测量向量。接着设计了一种卡尔曼滤波预测器,融合了虚拟测量向量以及模型预测结果并输出最终预测结果。仿真结果表明,提出的状态预测算法可以准确预测0.5秒内铰接转向车辆的铰接转角、速度以及位置。

Active steering control strategy for articulated vehicles

To improve maneuverability and stability of articulated vehicles, we design an active steering controller, including tractor and trailer controllers, based on linear quadratic regulator(LQR) theory. First, a three-degree-of-freedom(3-DOF) model of the tractor-trailer with steered trailer axles is built. The simulated annealing particle swarm optimization(SAPSO) algorithm is applied to identify the key parameters of the model under specified vehicle speed and steering wheel angle. Thus, the key parameters of the simplified model can be obtained according to the vehicle conditions using an online look-up table and interpolation. Simulation results show that vehicle parameter outputs of the simplified model and Truck Sim agree well, thus providing the ideal reference yaw rate for the controller. Then the active steering controller of the tractor and trailer based on LQR is designed to follow the desired yaw rate and minimize their side-slip angle of the center of gravity(CG) at the same time. Finally, simulation tests at both low speed and high speed are conducted based on the Truck Sim-Simulink program. The results show significant effects on the active steering controller on improving maneuverability at low speed and lateral stability at high speed for the articulated vehicle. The control strategy is applicable for steering not only along gentle curves but also along sharp curves.

基于联合模型铰接汽车原地转向工况特性分析

铰接汽车的转弯半径小,结构简单,被广泛应用适合于地下巷道运输。此类车辆原地转向呈“折腰”现象,在建立模型时影响因素多误差大。根据双液压缸转向系统的结构布置特点,对原地转向工况进行几何学分析,获取该工况的转向轨迹;基于轨迹分析,应用Simulink建立分析模型;针对整车和液压系统,分别应用ADAMS和AMEsim建立模型,联合建立分析模型;将原地工况液压缸受力拟合方程施加到模型中,对铰接点受力和整车轨迹进行分析;选取车体质心位置向前、向后等的变化,对铰接点受力、车轮受力及轨迹等的影响进行分析。结果可知:原地转向时,前后车体内外轮运动方向相反,且受力方向相反,实现整车顺利转向;后车体车轮所受垂向力波动比较频繁,这对铰接车转向稳定性有很大影响;当后车体质心位置前移或后移时,铰接体所受的纵向和横向的力均增大,后移时,受力情况更为恶劣;模型获得的原地转向轨迹呈现的是一种类似于“折腰现象”的转向方式,这与实际运行情况相符,解决了模型误差大的问题,为此类设计研究提供参考。

基于协同转向的铰接车辆轨迹跟随控制研究

针对铰接车辆后轴主动转向实现跟踪首轴轨迹的问题,本文提出一种基于多轴协同转向的补偿模糊PID控制方案.首先,根据各车轴具有同一转动中心的假设,利用扩展阿克曼转向原理确定了车轴的前馈控制转角;其次,依据首轴中心行驶轨迹,计算后轴的跟随偏差及变化率,并利用模糊PID控制理论,确定后轴的补偿控制转角,提高车辆的轨迹跟随控制性能;最后,在典型道路工况上,通过设置不同速度、道路附着系数及控制方案检验补偿模糊PID控制方案的轨迹跟随性能及鲁棒性.结果表明:在相同速度及道路附着系数下,相比于扩展阿克曼转向前馈控制及模糊PID控制方案,本文设计的补偿模糊PID控制进一步降低了轨迹跟随时各车体的横向偏差,并减小了车辆之间的横向铰接力;与PID控制相比,在不同速度及道路附着系数下,验证了补偿模糊PID控制具有一定的自适应性能.