新型铰接转向机构参数优化设计

该文介绍了一种新型的铰接转向机构,采用特殊的双摇杆转向型式,以采用此转向机构的某重载车辆为研究对象,利用CAE软件ADAMS,建立了机构铰点参数化的虚拟样机,采用Design study方法,得出转向机构参数性能的变化情况以及设计参数的近似敏感度,得到关联度最大铰点。采用OPTDES-SQP优化模型,设置目标函数,建立了以综合转向性能最优为优化目标的优化设计模型。经过优化,转向力臂差变化比率 为﹣74.6%,转向角度增加+2.22%,通过实际应用,减小了转向过程转向液压系统的振动和冲击,增加了系统转向稳定性,取得了良好的效果,为该转向系统的控制与操作提供了必要的依据。     

整车建模和转向性能分析

转向性能研究中一般会更多地关注方向盘力矩的变化。所以,转向系统对分析精度起决定性影响,必须建立详尽的模型来描述其内部特性,如惯性、刚度、摩擦、阻尼和助力曲线,这些因素对方向盘力矩变化有非常显著的影响,以致影响转向性能。本文阐述了在AMESim软件中建立液压助力转向系统和整车模型的过程。首先提出了一种新的计算转向阀过流面积的方法,以获得真实的转向助力特性,然后建立了包含这个比较详尽的转向系统的整车动力学模型,用于转向性能研究,最后选用了几种实车道路试验结果来验证此模型的准确性。     

Proportional directional valve based automatic steering system for tractors

Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3- position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressurecompensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative (PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.     

一种抑制大型飞机液压伺服作动系统耦合振荡的方法

针对大型飞机液压伺服作动系统与飞机结构之间的耦合振荡问题,提出了一种在液压伺服作动系统中通过加装双向节流阀抑制耦合振荡的方法,具体是在液压伺服作动器的作动筒的进油通路与回油通路之间串接一个双向节流阀,增大液压伺服作动系统阻尼以增加系统的频宽,进而增大液压伺服作动系统与飞机结构之间的频宽倍比,从而有效抑制了系统的耦合振荡.该方法通过仿真分析及试验,验证了其可行性及合理性,并取得了很好的效果,为工程应用提供了依据.     

基于整车动力学模型的EPS预测控制策略仿真研究

为了提高车辆的转向性能,基于整车动力学模型,研究电动助力转向系统(EPS)控制策略;针对PID控制参数固定不变,无法实时控制EPS动态响应的问题,提出了一种滚动优化的预测控制策略,并运用CarSim整车模型与Matlab软件相结合,实现了EPS控制仿真;通过对比仿真结果中横摆角速度和质心侧偏角等转向性能参数表明:用预测控制算法对EPS实施控制,比传统控制方法更精确,可有效提高车辆的转向性能和操纵稳定性,使EPS操控更加精准和轻捷。     

Vehicle Dynamics Modeling and Electronic Stability Program/ Active Front Steering Sliding Mode Integrated Control

Chassis integrated control can significantly improve vehicle handling stability and comfort. Because of the complexity of the problem, it has attracted significant research attention. We built a vehicle nonlinear dynamic model with multi‐degree freedom, including body movement, wheel movement, and electronically controlled hydraulic power steering system. We compared the magic formula tire model, Dugoff tire model, brush tire model, and LuGre dynamic friction tire model and steady model. The precision of the model was verified by a comparison between simulation results and the real vehicle test results. Then, based on the vehicle dynamics model, an AFS (active front steering) controller was designed based on sliding mode variable structure control, and an AFS and ESP (electronic stability program) integrated coordination controller was proposed. Finally, based on the nonlinear tire model and multi‐DOF (degree of freedom) vehicle model, sinusoidal and step steering angle input simulation analysis was proposed on different road friction coefficients. The results show that the vehicle has better response characteristics with coordinated control strategy when compared with AFS and ESP only control. The evidence suggests that the proposed integrated control system in this paper can improve vehicle stability and safety.     

牵引车–飞机系统的自适应滑模变结构控制

将自动转向技术应用于牵引车–飞机系统, 并以侧偏位移和相对横摆角作为反馈, 提出一种牵引车四轮主动转向控制策略. 重点考虑牵引车和飞机的侧向和横摆运动, 建立含铰接角在内的牵引车–飞机系统非线性动力学模型. 将牵引车和飞机的轮胎侧偏刚度视为有界的不确定性参数, 将侧向风等因素视为未知的外在扰动, 采用自适应滑模变结构控制方法设计牵引车转向角控制器. 仿真结果表明, 设计出的前、后轮转向控制器能使控制系统同时获得很好的轨迹跟踪性和操纵稳定性, 并且能够有效的克服参数摄动和外界干扰对系统操作性的影响.     

机载液压舵机伺服系统优化控制研究与仿真

研究机载液压舵机伺服系统液位精确控制问题。飞行器在空中起降高度发生大幅变化时导致气压不稳,液压受到气压不稳的影响发生不规律性和非线性波动。传统液压舵机伺服控制方法中,以PID算法为基础,控制参数灵活,不能很好地处理液压异常变化带来的液位零漂、滞后造成的影响,造成液位控制精度不高的问题。为此提出了参数动态调整的机载液压舵机伺服系统液位优化控制算法,通过建立参数动态模型,运用动态模型使得液压参数可以根据实际情况变化,保证了干扰条件下的控制精度。仿真结果表明,优化控制方法能够有效解决气压干扰下液位的控制精度,为系统优化提供思路。     

Full perimeter obstacle contact sensor based on flex sensors

This paper presents an obstacle contact sensor system that can detect both the contact state and the direction of contact parallel to the movement plane of a mobile system carrying the sensor. This sensor system is based on a regular- or irregular-shaped ring surrounding the mobile system’s perimeter, connected to the mobile system’s body by a set of soft springs and also coupled mechanically to a set of four flex sensors measuring the relative displacement and direction of the ring when contacting an obstacle. The set of flex sensors is connected to a low-cost electronic module that implements a data acquisition block and a fuzzy processing block, delivering a value representing the estimated contact zone of the ring. Some experiments show how this detection system effectively reduces the sensor count needed for full coverage of the mobile system’s perimeter. Despite the kind of output implemented in the experiments, the contact force can also be estimated.     

铰接式履带车辆转向特性仿真研究

针对深海富钴结壳行走装置必须适应复杂恶劣地形和较强的越障性能,提出一种具有四个液压缸的主动式联结装置的铰接式履带车辆,通过对铰接式履带车辆进行转向运动学分析,以及对联接装置的转向工作机理进行分析,得出了转向液压缸活塞杆伸长量与车辆理论转向半径的关系,并采用多体动力学仿真软件ADAMS的履带车辆工具箱ATV 建立了铰接式履带车辆的虚拟样机模型,仿真得到了铰接转向角速度,铰接转向半径,铰接转向所耗功率与差速转向所耗功率的关系,仿真结果表明,仿真模型具有较高的精度,能够对转向过程中主要参数随时间的变化历程进行仿真,可以为铰接式履带车辆转向过程的研究提供理论分析根据.     

The Virtual Prototype Model Simulation on the Steady-state Machine Performance

Articulated tracked vehicles have high mobility and steering performance. The unique structure of articulated tracked vehicles can avoid the subsidence of tracks caused by high traction from instantaneous braking and steering. In order to improve the accuracy of the steady-state steering of the articulated tracked vehicle, the velocity of both sides of the track and the deflection angle of the articulated point need to match better to achieve the purpose of steering accurately and reduce energy consumption and wear of components. In this study, a virtual prototype model of the articulated tracked vehicle is established based on the multi-body dynamic software RecurDyn. The trend of the driving torque and power of each track changes as the velocity difference of two sides of the tracks and the traveling trajectory of the mass center of the front vehicle change in a specific condition are obtained by the experiment. The experimental results are compared and verified with the results obtained from the virtual prototype simulation. The change law of driving power in the steadystate steering process on the horizontal firm ground as changing the velocity difference of two sides of the tracks, the theoretical steering radius, and the ground friction is obtained by the virtual prototype model simulation analysis. The steering inaccuracy and track slip rate are used as indexes in evaluating the steady-state steering performance of the articulated tracked vehicle. The research provides references for the study of steady-state steering performance of articulated tracked vehicles.     

ADAMS／Car在汽车操纵稳定性仿真中的应用

在研究汽车动力学特性中,针对车辆响和操纵稳定性,利用ADAMS/Car软件建立了某轿车的操纵动力学多体仿真模型,考虑前后悬架系统、转向系统、轮胎、衬套和载重等的影响,较为真实地仿真了汽车在方向盘转角阶跃输入条件下的转向情况,为汽车的操纵稳定性分析奠定了基础,并较为详细地分析了汽车在转向盘转角的转向特性。通过对不同车速、不同载荷下的仿真研究,得出汽车在这些不同条件下的响应,研究汽车的转向特性与车速、载荷的关系。为以后汽车的操纵稳定性等此类问题的设计研究提供了参考依据。     

基于阻尼多级分段调节的半主动悬架系统

为提高汽车的平顺性和舒适性,提出了一种多级分段调节减振器阻尼的方法。为创建该方法,首先建立了汽车半主动悬架动力学模型,通过分析模型得到和减振器匹配的阻尼控制规律和最优解。设计了一种基于电磁阀控制节流孔通道的硬件结构。对减振器阻尼大小进行了分级定义,对不同的路面状况,匹配不同级别的减振器阻尼。探讨了半主动悬架可控减震器节流参数控制规律,根据该规律构思了此减振器的控制方法。开展了针对多级分段调节的半主动悬架系统的路面试验,试验表明该种减振器具有较好的减震效果,能够有效的提升汽车的的行驶平顺性和稳定性。     

基于Adams/Car汽车转向系统力矩波动优化分析

详细阐述转向系统力矩波动的基本原理,并基于Adams/Car悬架系统模型进行DOE分析,找到对转向传动比波动影响最关键的因素;然后结合实际车辆,优化得到转向传动比波动最小时的相位角最佳值.在实车上对优化方案进行验证.     

Yaw stability control of articulated frame off-highway vehicles via displacement controlled steer-by-wire

Off-highway vehicles have not received the same level of scrutiny that their on-highway counterparts did relative to safety, comfort, fuel economy, and automation. Over the past few decades, various active chassis safety control systems, architectures, and schemes have been researched and developed to improve the stability and handling of on-highway vehicles, including articulated vehicles such as tractor–trailer applications. In this paper, the authors investigate a yaw stability control system for articulated frame steering off-highway vehicles via novel steer-by-wire technology that they have recently developed. A high-fidelity vehicle dynamics model is derived while keeping the yaw rate decoupled from the lateral acceleration, in order to separate the primary path-following task (driver) from the secondary disturbance–attenuation task (controller). The control algorithm is then designed such that the two tasks do not hamper one another, and that the automatic controller is quickly activated for a short period of time to counteract instabilities, and then smoothly relinquishes control back to the human operator. Simulation and experimental testing results are obtained to validate the vehicle dynamics model, the control algorithm design, and the new system's efficacy in counteracting yaw instabilities on low-friction surfaces using standard vehicle dynamic maneuvers.     

Proposing an interactive speaking improvement system for EFL learners

This paper proposes a web-based interactive speaking improvement system for EFL learners. Using fuzzy matching, the system automatically compares the learner’s and the system’s pronunciation and immediately provides corrective interaction whereby the student can improve speaking via continuous imitation and practice at the computer. The system, having been tested on Taiwanese students who needed to achieve a speaking proficiency equivalent to CEF Level A2, is found to be highly effective for the intended purpose.     

基于功率键合图装载机转向系统建模与仿真

为了使装载机转向系统的设计能够保证在作业或行驶时的机动性、安全性 和敏捷性,一般要对该系统进行虚拟仿真设计。首先分析小型多功能装载机液压转向系统工 作特性,包括系统组成,转向工作原理,及系统模型简化;然后以键合图理论为建模工具, 根据能量和信息流动与转换过程的不同,将转向系统各组成元件抽象为键合图元,建立了液 压转向系统的功率键合图;接着推导了液压转向系统工作过程的状态方程;最后,在 MWORKS 软件环境中建立了液压转向系统功仿真模型,并对转向过程进行了仿真测试。为 小型多功能装载机转向系统设计制提供了一套完整的理论与方法,对装载机转向系统的设计 具有着重要的理论和工程应用价值。     

基于端到端深度学习的智能车自动转向研究*

为解决由图像直接计算出控制量的端到端深度学习算法中感知器和控制器难以区分的问题,对其网络结构进行了改进。通过预训练一个自编码器,得到良好的道路特征编码后,将编码器作为感知器和和转角预测控制器一起进行端到端的训练。训练结果表明,改进后的自动转向网络模型收敛的更快,预测的角度在测试集上能较好的跟随实际角度变化而变化。利用解码器和特征图反向传播法分别还原出道路图片,可视化了该自动转向模型重点关注的道路特征。