Path Planning of Multi-Axis Robotic Arm Based on Improved RRT*

An improved RRT∗algorithm,referred to as the AGP-RRT∗algorithm,is proposed to address the problems of poor directionality,long generated paths,and slow convergence speed in multi-axis robotic arm path planning.First,an adaptive biased probabilistic sampling strategy is adopted to dynamically adjust the target deviation threshold and optimize the selection of random sampling points and the direction of generating new nodes in order to reduce the search space and improve the search efficiency.Second,a gravitationally adjustable step size strategy is used to guide the search process and dynamically adjust the step-size to accelerate the search speed of the algorithm.Finally,the planning path is processed by pruning,removing redundant points and path smoothing fitting using cubic B-spline curves to improve the flexibility of the robotic arm.Through the six-axis robotic arm path planning simulation experiments on the MATLAB platform,the results show that the AGP-RRT∗algorithm reduces 87.34%in terms of the average running time and 40.39%in terms of the average path cost;Meanwhile,under two sets of complex environments A and B,the average running time of the AGP-RRT∗algorithm is shortened by 94.56%vs.95.37%,and the average path cost is reduced by 55.28%vs.47.82%,which proves the effectiveness of the AGP-RRT∗algorithm in improving the efficiency of multi-axis robotic arm path planning.

Scheduling on tractor and trailer transportation considering the influence of disrupted events based on the contract net and simulated annealing algorithm

To provide a much more resilient transport scheme for tractor and trailer transportation systems,this paper explores the generation method of tractor and trailer transport schemes considering the influence of disrupted events.Three states of tractors including towing loaded trailers,towing empty trailers,and idle driving are taken into account.Based on the disruption management theory,a scheduling model is constructed to minimize the total deviation cost including transportation time,transportation path,and number of used vehicles under the three states of tractors.A heuristics based on the contract net and simulated annealing algorithm is designed to solve the proposed model.Through comparative analysis of examples with different numbers of newly added transportation tasks and different types of road networks,the performance of the contract net algorithm in terms of deviations in idle driving paths,empty trailer paths,loaded trailer paths,time,number of used vehicles,and total deviation cost are analyzed.The results demonstrate the effectiveness of the model and algorithm,highlighting the superiority of the disruption management model and the contract net annealing algorithm.The study provides a reference for handling unexpected events in the tractor and trailer transportation industry.

Microstructure and mechanical properties of isothermal multi-axial forging formed AZ61 Mg alloy

Microstructure and mechanical properties of AZ61 Mg alloy during isothermal multi-axial forging （MAF） were studied. The mechanisms of grain refinement and relationship between the microstructures and mechanical properties were discussed. The results show that the average grain size decreases with increasing the number of MAF passes. The grains are significantly refined at the 1st and 2nd MAF passes, and gradually refined at higher MAF passes. The initial grain size of 148 lam decreases to about 14 gm after 6 MAF passes. The grain refinement occurs mainly by continuous dynamic recrystallization. With increasing the MAF passes, both the tensile strength and the elongation to failure of the alloy are significantly enhanced.

Dynamic precipitation during multi-axial forging of an Mg-7Gd-5Y-1Nd-0.5Zr alloy

The dynamic precipitation behavior during multi-axial forging in an Mg-7Gd-5Y-1Nd-0.5Zr alloy has been investigated and compared with that in static precipitation treatment. The results indicated that dynamic precipitation does occur during multi-axial forging. The dynamic precipitate can be deduced as β phase with face-centered cubic crystal structure (a = 2.22 nm). Most of the β precipitates locate at the dynamic recrystallization grain boundaries. The morphology and orientation relationship is different from that of the β phase formed in the static precipitation treated alloys, although the crystal structure is the same. The precipitation temperature of β phase during MAF is higher than that in the static precipitation treatment.

Multi-axial strain-stiffening elastic potentials with energy bounds:explicit approach based on uniaxial data

According to the well-known models for rubberlike elasticity with strain- stii^ening effects, the unbounded strain energy is generated with the unlimitedly growing stress when the stretch approaches certain limits. Toward a solution to this issue, an explicit approach is proposed to derive the multi-axial elastic potentials directly from the uniaxial potentials. Then, a new multi-axial potential is presented to characterize the strain-stiffening effect by prescribing suitable forms of uniaxia] potentials so that the strain energy is always bounded as the stress grows to infinity. Numerical examples show good agreement with a number of test data.

Research on Risk Assessment Method of Long-Tube Trailer Road Transportation

Road transport safety has always been paid attention to by the safety production managers of enterprises. In this study, cloud model and analytic hierarchy process were applied to the safety of long-tube trailer transport. The opinions of 30 experts were analyzed, from which 29 key parameters were selected. The study addressed the relevance of the parameters and the possibility of automatic collection and transmission to obtain 12 core risk factors. The macro-safety risk indicator system for long-tube trailers was established based on the identified risk indicators. Finally, a risk assessment model for road transport of long tube trailers consisting of 3 dimensions of likelihood, severity and sensitivity was constructed. This model provides a technical method for strengthening the risk control of road transport of long-tube trailers.

基于模糊快速滑模的农用牵引车辆直线路径跟踪控制

为解决无人驾驶牵引式农机在非结构化环境中作业时直线跟踪精度低、上线速度慢、抗干扰能力差等问题,提出了一种基于模糊快速滑模控制的农用牵引式车辆直线路径跟踪控制方法。首先利用车辆运动学模型与参考路径建立牵引车辆直线路径跟踪误差模型,并提出一种基于模糊参数整定的快速滑模直线路径跟踪方法,解决了滑模控制算法的控制器抖振与机具快速上线问题。通过Lyapunov稳定性分析可知,所设计控制方法可保证牵引机具跟踪参考路径,同时铰接角收敛至零。最后,基于Simulink仿真与实车试验对该控制方法的有效性与优越性进行测试。田间实车试验表明,使用本文控制方法时,拖车和挂车最大路径跟踪横向误差分别为0.11、0.12 m,拖车和挂车跟踪误差方差分别为0.0013、0.0015 m^(2);相较于传统基于等速趋近律设计的滑模控制器,上线时间提升约58%,最大跟踪误差减小约66%。

Analysis of the Effect of Trailer Tire Size on the Articulated Vehicle’s Stability

This research paper aims to identify the effect of tire size on the handling characteristics of a trailer attached to a vehicle. In various stability tests, different models with different tires from the market were tested. A successful outcome of this research would generate an efficient tire selection process and improve the handling of a trailer attached to a vehicle while maximizing fuel efficiency. In this study, different accurate tire models using the magic formula were developed in vehicle dynamics modelling and simulation software. These models were then simulated on on-road conditions to predict vehicle and trailer behaviour under different conditions within the software. Two distinct tests were conducted, the J-Turn test and the Double Lane change test. The results of these tests were used to evaluate the handling characteristics and decide on a better tire size for the trailer attached to the vehicle.

拖曳水池教学实验室拖车设计与研制

按照“设计—研制—标定”的思路,完成了船模拖曳水池拖车系统研制。设计阶段结合教学科研需求完成拖车结构设计、最大航速确定和拖车重量预估,并用数值模拟方法完成强度校核和模态分析;研制阶段先在工厂进行分段制造,后运输至实验室现场组装调试,完成了机械调试和电路调试两部分;标定阶段完成了拖车振动测试、标模阻力测试和敞水测试。将新拖车用于本科教学,提高了教学效率,丰富了教学手段,有助于提升学生对实验现象的观察与知识点的理解。

特种公路运输半挂车转向液压系统优化设计

针对某特种公路运输半挂车转向液压系统进行了优化,优化后的液压系统降低了车辆受环境温度变化的影响、消除了行车摆尾现象,改善了整车的转向性能。

复杂场景下工程机器人的机械结构分析与设计

依托于RoboMaster机甲大师赛,提出了一种应用于复杂场景下的工程机器人机械结构分析与设计方法,并基于该原则对工程机器人进行了结构设计,使工程机器人可以实现稳定行走、取弹、登岛、救援等功能。工程机器人的行驶系统采用四轮独立悬挂搭配麦克纳姆轮来进行全方向灵活移动,取弹系统采用一组M3508电机进行夹取和补弹,救援系统采用CDJ-10型迷你气缸和曲柄连杆进行拖车救援。

基于点云技术的汽车外廓尺寸测量方法研究

针对《机动车安全技术检验项目和方法》(GB 38900—2020)中对于汽车外廓尺寸测量的新要求,采用整车点云数据技术,对牵引车与各类挂车连接后外形上的共性和外廓分割的关键位置进行了研究。通过改进三维点云分割算法,提出一种一并式测量汽车列车和挂车外廓尺寸的测量新方法。该方法可在不改变硬件的前提下,仅通过软件和算法升级,实现一次测量即可测得汽车列车(牵引车、半挂车组合)外廓尺寸参数。以多种结构挂车为试验案例验证了所提方法的可行性,并通过适应性试验分析了所提方法的有效性。研究结果表明,该方法完全能够满足GB 38900—2020中的新增要求,具有广泛的适用性与较高的测量精确度。该方法可将传统方法测量耗时从“小时级”提升为“秒级”,显著提高相关机构的工作效率。

小型集材挂车满载工况下的有限元建模与分析

小型集材挂车于林间作业存在多种工况,包括满载弯曲、满载扭转、紧急制动和急速转弯。为解决挂车在满载工况下车载系统的可靠性与安全性较差的问题,建立小型集材挂车的三维装配模型,进行静态分析。通过有限元分析,研究挂车在4种典型工况下的结构变形和应力分布。研究表明,满载弯曲工况下,最大位移为4.5177 mm,最大应力为115.19 MPa,安全系数为3.08;满载扭转工况下,最大位移为0.98448 mm,最大应力为71.929 MPa,安全系数为4.935;满载制动工况下,最大位移为4.9946 mm,最大应力为120.05 MPa,安全系数为2.957;紧急转弯工况下,最大位移为4.3658 mm,最大应力为104.64 MPa,安全系数为3.39。结果显示研究设计的小型集材挂车在林间作业时满载工况下稳定性较强,确保木材的可靠采集和运输。基于该结果可进一步优化挂车设计和性能,以适应不断变化的需求和环境要求。

双挂汽车列车横向稳定性控制策略

双挂汽车列车相较于传统半挂车具有更高的运输效率和较低的运输成本,更适合未来公路运输绿色、便捷、高效的发展趋势,但较长的车身总长度和组成单元个数必然会对双挂汽车列车的整车稳定性产生影响.为研究并验证控制策略对双挂汽车列车横向稳定性的改善情况,基于Trucksim仿真平台搭建双挂汽车列车(B型双挂车)动力学模型,依据运动力学定律建立Simulink双挂汽车列车简化参考模型,分别以动力学和参考模型中各个单元的横摆角速度偏差、横向载荷转移率偏差为输入,结合模糊推理和PID(proportional-integral-derivative control,PID)控制理论构建整车横摆和侧倾稳定性主动控制策略,并根据车辆状态识别结果对控制策略的介入时机进行调整.模拟结果显示:主动控制策略使双挂汽车列车横向稳定性评价参数的波动幅度均有明显减小;各个单元的质心侧偏角峰值降低5.7%∼53%,横摆角速度峰值降低4.9%∼23.8%,侧倾角峰值降低0.5%∼24.9%,质心侧偏角峰值降低0.3%∼32.9%.表明本工作所设计的控制策略对双挂汽车列车的横向稳定性有改善作用,研究结果可为未来双挂汽车列车的横向稳定性研究提供参考.

换挂模式下的公路卡车货运优化问题

本文深入研究了换挂模式在公路卡车货运中的应用,通过卡车间的挂车交换,有效减少卡车空载现象,进而降低运输总成本。为了探讨卡车个体特征对换挂模式的影响,基于一般换挂模式扩展了受限换挂模式,并构建了两种模式下公路卡车货运优化问题的混合整数线性规划模型。该模型旨在最小化卡车的总成本,包括卡车运输成本和货物延迟送达惩罚成本。鉴于原模型无法在可接受的时间内求得问题最优解,引入两个辅助参数,将原模型转换为纯整数规划模型。然而,受限换挂模式下的卡车个体收益四维约束求解难度依然很大,因此,基于卡车潜在换挂节点集和节点潜在换挂卡车集的分析,对卡车个体收益约束进行了拆分和删减。实验结果显示,相较于传统模式,一般换挂模式和受限换挂模式在降低总成本、减少油耗、降低卡车空载率、缩短行驶时间方面均取得显著效果,具体地,两种模式分别使总成本平均降低28.3%和25.1%,油耗减少33.3%和29.7%,空载率下降33.1%和29.4%,行驶时间缩短35.0%和27.6%。然而,换挂模式在货物时效性方面略显不足,延迟送达率平均为15.4%和12.9%。此外,一般换挂模式下,部分卡车的行驶时间会略微延长,平均增长率为7.4%。最后,卡车空载系数灵敏度分析结果显示,在不同系数下换挂模式的性能仍然显著。

甩挂运输中牵引车与挂车数量配置优化仿真

牵引车与挂车数量合理配置是道路甩挂运输中的重要内容,对提高牵引车使用效率、降低车辆的购置费用具有重要意义。以牵引车购置费用、牵引车运行费用以及牵引车等待时间费用最小为目标,考虑甩挂运输任务时间窗约束和牵引车运行径路约束,构建了上述问题的数学规划模型。针对牵引车与挂车数量配比问题的组合爆炸特点,设计了结合模拟退火邻域搜索策略的并行蚁群搜索算法。最后以郑州市某个物流企业进行实例分析,结果表明所提方法能够在较短时间内获得满意解,有效地减少了整个甩挂运输系统的综合成本。

半挂液罐车弯道安全车速优化控制

为降低半挂液罐车驶过弯道路段过程中的侧翻事故风险,提出了基于最优控制的半挂液罐车弯道安全车速优化控制方法。该控制方法以侧翻事故防控为优先目标,以高效通行为辅助目标,帮助半挂液罐车在驶向弯道时提前获得无横向失稳隐患的最优车速控制方案,实现“预防式”的车辆主动安全控制。同时为提高控制方案有效性,利用正弦波动方程拟合罐内液体纵向转移过程,结合基于改进准静态法的罐内液体横向偏移规律,构建了具有纵横双维度描述能力的罐内液体晃动模型,提高了最优控制问题成本函数中半挂液罐车横向稳态表征指标的准确性。仿真结果表明:受控半挂液罐车驶过弯道过程中的瞬时横向载荷转移率始终处于[-0.7,0.7]的安全范围内;不同弯道半径下车辆瞬时横向载荷转移率均有下降,且在弯道半径61 m时降幅最大;受控半挂液罐车最大瞬时横向载荷转移率最大降幅达到0.07;车速控制对道路通行效率的负面影响较小。该控制方法帮助半挂液罐车避免侧翻事故,适用于多种不同半径的弯道路段。

基于稀疏化数据的重载半挂牵引车工况构建

针对北方环境下重载半挂牵引车跨区域典型行驶工况的缺位现象,以及工况构建对优质数据的高度依赖问题,应用道格拉斯-普克(Douglas-Peucker,DP)算法将采集数据处理为稀疏节点数据与驾驶行为特征数据,基于稀疏节点数据划分行驶片段,经主成分分析和k-means聚类构建初始工况,初始工况与驾驶行为特征数据匹配和叠加形成典型行驶工况。结果表明,该工况构建方法的平均相对误差相比传统方法降低了约19.63%,其仿真油耗与原始数据仿真油耗的相对误差也在5%以内。同时,该方法可以实现低频数据向高频数据的映射,有助于解决工况构建对采集数据颗粒度的高度敏感性问题。

拖曳水池拖车的结构设计及分析

针对港口及近海工程模型试验中对于拖车实验的需求,提出一种大型拖曳水池拖车机构,具体为拖车车架的结构进行设计、分析、校核。应用三维设计软件SOILDWORKS,基于参数设计了拖车的三维模型。在此基础上,采用有限元分析软件ANSYS对拖车模型进行网格划分以及静刚度和强度、固有频率的分析计算。研究结果证明:所设计拖车的结构强度和频率性能等均可满足设计要求。

拖拉机挂车气制动系统设计

介绍了拖拉机挂车气制动系统的通用要求,阐述了储气筒、空气压缩机和卸荷阀的设计要点。分别从储气筒、刹车阀、卸荷阀、空气压缩机出气管和气制动管路等方面介绍挂车气制动系统的布置原则。介绍了管路直径、材料选取规范,对管路固定和连接、软管布置、零部件通用化进行说明。