汽车摆振动力学机理研究——位移延时反馈及能量传递分析

主要分析了汽车摆振的动力学机理。通过使用解析法从理论上证明了摆振是由位移延时反馈引起的自激振动现象。利用数值分析方法揭示摆振系统的动力学机制及响应行为,验证了解析分析的相关结论。并进一步计算能量输入与能量传递的值,结果表明能量输入可以用来评价汽车摆振的动力学响应。最后根据能量传递规律提出汽车摆振的抑制措施。     

含双间隙连杆机构动力学仿真与实验

为考察含双间隙连杆机构的动力学行为,进行了仿真和实验研究。在仿真中,基于ADAMS软件建立了一个非线性接触力模型。同时,设计和建立了一个实验装置来对仿真结果进行验证。分别讨论了间隙尺寸、加载频率和加载力幅值对接触碰撞力的影响。结果表明,间隙的存在会影响传递力曲线,使机构产生明显的振动冲击,间隙大小和加载速度是影响机构动态响应的主要因素。实验结果证明了本文模型的正确性。     

起落架结构参数对飞机机轮摆振的影响

建立了飞机机轮摆振运动方程,详细研究了起落架三个重要结构参数;稳定距、支柱刚度和减摆器传动系统扭转刚度对飞机机轮摆振的影响,考虑了各参数之间的耦合作用,严格区分“轮胎型”摆振和“结构型”摆振,并分别予以研究,所得结论为新机防摆设计和现役飞机防摆维护提供了理论依据。     

Design and development of a variable ground clearance,variable wheel track self-leveling hillside vehicle power chassis (V2-HVPC)

This paper presents a design of hillside vehicle power chassis with the balance rocker suspension mechanism. The objective of design is to achieve a variable ground clearance, variable wheel track and self-leveling chassis adapted to the various types of crop grown ridge section and height. The V2-HVPC design consists of the main body, the balance rocker suspension, two driving axles and the steering system. Those assemblies form an H-type chassis structure where both sides of the driving axle and the main body are connected to power transmission. The ground clearance and wheel track have the adjustable function. The balance rocker suspension is a novel mechanism which ensures full-time four-wheel drive in a complex road environment while maintaining the main body level always in the angle bisector of the two driving axle. According to the hillside terrain and agronomic characteristics of various crops, the ground clearance and the wheel track can be adjusted continuously and smoothly by hydraulic system. The topology diagram and power transmission system diagram are all given correspondingly. Moreover simulation analysis and basic experiments have been carried out to verify the mobility and dynamic performance of the V2-HVPC. The results show that the concept of V2-HVPC is approved reasonable and the design and testing methods are feasible and practical.     

Development of a vehicle to study the tractive performance of integrated steering-drive systems

This paper describes a test-bed vehicle for studying the integration of the steering system of a wheeled vehicle with the drive system. The vehicle was produced in order to determine whether such an integrated system is practical; to investigate tractive performance compared to other steering-drive systems; and to determine under which conditions such a system has better performance. The integrated steering-drive system of the test-bed vehicle uses a computer to co-ordinate the independently driven wheel speeds of the drive system (which is also the primary steering system) with the steer angles of the non-driven steerable wheels to produce a beneficial secondary steering effect. The secondary steering system assists the primary steering system when side forces act on the vehicle, while producing minimal conflict. This concept can be applied to agricultural vehicles such as tractors, harvesters, mowers, sprayers and self-propelled windrowers. The test-bed vehicle is able to be configured for the following steering-drive systems types: open differential drive with steerable wheels, independent drive wheels with castors, locked differential drive with steerable wheels and a computer integrated steering-drive system. The capacity of the test-bed vehicle to be configured as described is a significant advantage when measuring tractive performance, as the results obtained will be more valid due to the vehicle parameters being the same.     

Dynamic analysis of planar rigid-body mechanical systems with two-clearance revolute joints

In this paper, the behavior of planar rigid-body mechanical systems due to the dynamic interaction of multiple revolute clearance joints is numerically studied. One revolute clearance joint in a multibody mechanical system is characterized by three motions which are: the continuous contact, the free-flight, and the impact motion modes. Therefore, a mechanical system with n-number of revolute clearance joints will be characterized by 3 ⁿ motions. A slider-crank mechanism is used as a demonstrative example to study the nine simultaneous motion modes at two revolute clearance joints together with their effects on the dynamic performance of the system. The normal and the frictional forces in the revolute clearance joints are respectively modeled using the Lankarani–Nikravesh contact-force and LuGre friction models. The developed computational algorithm is implemented as a MATLAB code and is found to capture the dynamic behavior of the mechanism due to the motions in the revolute clearance joints. This study has shown that clearance joints in a multibody mechanical system have a strong dynamic interaction. The motion mode in one revolute clearance joint will determine the motion mode in the other clearance joints, and this will consequently affect the dynamic behavior of the system. Therefore, in order to capture accurately the dynamic behavior of a multi-body system, all the joints in it should be modeled as clearance joints.     

Nonlinear vibration semi-active control of automotive steering using magneto-rheological damper

Traffic accidents are often caused by vibration of automotive steering because the vibration can make a vehicle run like a snake. A?novel semi-active vibration control strategy of automotive steering with magneto-rheological (MR) damper is proposed in this paper. An adaptive RBF neural sliding mode controller is designed for the vibration system. It is showed that an equivalent dynamic model for the vibration system is established by using Lagrange method, and then treats it as actual system partially. A?feedback control law is designed to make this nominal model stable. Uncertain part of system and outside disturbance are estimated using RBF neural network, and their upper boundary is obtained automatically. By constructing reasonable switch function, state variables can arrive at origin asymptotically along the sliding mode. Strong robust character of control system is proved by stability analysis and a numerical simulation example is performed to support this control scheme.     

Dynamics analysis of 2-DOF complex planar mechanical system with joint clearance and flexible links

Joint clearance and flexible links are two important factors that affect the dynamic behaviors of planar mechanical system. Traditional dynamics studies of planar mechanism rarely take into account both influence of revolute clearance and flexible links, which results in lower accuracy. And many dynamics studies mainly focus on simple mechanism with clearance, the study of complex mechanism with clearance is a few. In order to study dynamic behaviors of two-degree-of-freedom (DOF) complex planar mechanical system more precisely, the dynamic analyses of the mechanical system with joint clearance and flexibility of links are studied in this work. Nonlinear dynamic model of the 2-DOF nine-bar mechanical system with revolute clearance and flexible links is built by Lagrange and finite element method (FEM). Normal and tangential force of the clearance joint is built by the Lankarani–Nikravesh and modified Coulomb’s friction models. The influences of clearance value and driving velocity of the crank on the dynamic behaviors are researched, including motion responses of slider, contact force, driving torques of cranks, penetration depth, shaft center trajectory, Phase diagram, Lyapunov exponents and Poincaré map of clearance joint and slider are both analyzed, respectively. Bifurcation diagrams under different clearance values and different driving velocities of cranks are also investigated. The results show that clearance joint and flexibility of links have a certain impact on dynamic behavior of mechanism, and flexible links can partly decrease dynamic response of the mechanical system with clearance relative to rigid mechanical system with clearance.     

Stabilization of a wheeled robotic vehicle subject to dynamic effects

The paper addresses the problem of designing a stabilization system for a wheeled robotic vehicle with one steering wheel subject to dynamic effects. A solution of the problem is given for the case of coasting. The admissible error of the robot speed in generating a feedback signal is estimated. The general problem of stabilization with allowance for dynamic effects is considered __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 9, pp. 116–126, September 2006.     

Steering performance of an inverted pendulum vehicle with pedals as a personal mobility vehicle

From the viewpoints of environmental protection, support for the aged and ensuring the right to mobility, there is a need to develop a new type of mobility vehicle that provides more effective transportation. The authors propose an inverted pendulum vehicle with pedals as one of the forms of personal mobility vehicles (PMVs). In this paper, the steering performance of the inverted pendulum vehicle with pedals is discussed based on experiments on a prototype. From the experimental results, it was confirmed that the errors from the five subjects for the target trajectory and the five-grade evaluation of the maneuverability were similar. Finally, we created an inverted pendulum vehicle with pedals to which was added a reaction actuator for the steering system. From the experimental results, it was found that setting appropriate feedback gains for the handle steering angle and its rate of rotation, which control the right and left wheel driving torques, resulted in greatly improved maneuverability.     

The problems of multi-axle vehicle drives

The multi-axle drive provides for maximum traction of the vehicle. However, this mode of driving, apart from the complicated design of the driving mechanism, is connected with major problems due to the so-called kinematic discrepancy encountered by a vehicle under operation. In certain conditions, the kinematic discrepancy results in the phenomenon of so-called circulating power which causes, first of all, additional loading on the drive system, then increased energy loss and tyre wear and, in the case of an articulated frame-steer vehicle, the substantial growth of steering resistance.The paper reviews some examples of results of the studies on wheel slips, load on the drive system, and on the 4-wheel-drive articulated frame-steer vehicle's steering gear. The author also discusses a new concept for determining kinematic discrepancy. The suggested equations, when applying the present mathematical models which express the dependence of a tyre's slip rate on longitudinal forces, permit to solve the statically undeterminable problem concerning the distribution of the wheel's longitudinal forces in any multi-axle vehicle.     

基于速度辅助的车载卫星定向模糊度动态确定方法

针对车载双天线卫星定向系统的载波相位模糊度动态确定,探讨了速度辅助对模糊度搜索空间的约束性能,首次提出主天线速度矢量方向与车体纵轴之间偏离角的定量表达式,从而实现了准确设置卫星定向模糊度解算中的航向搜索范围。对实际车载数据的分析验证了该方法的有效性,不但适用于车载纯卫星定向系统,而且适用于多天线卫星定向（定姿）/IMU组合车载航姿确定系统,可显著提高卫星定向动态模糊度搜索速度及成功率,尤其增强车辆机动时的模糊度初始化性能。     

Dynamic analysis of planar mechanisms with revolute clearance joints based on two evaluation indices

Joint clearance is one of the most important factors that influence the dynamic performance of a mechanical system. In this study, a quantitative analysis method, which contains two clearance effect evaluation indices that can better evaluate influence of clearance joints on the dynamic performance of the mechanisms, is proposed. A dynamic modeling approach of planar mechanisms with clearance joints is introduced. A crank-slider mechanism with multiple clearance revolute joints is studied to support the proposed analysis methodology. Besides, different dynamic responses generated by different materials of the clearance joints are also investigated based on the clearance effect evaluation indices.     

A feedback linearization design for the control of vehicle’s lateral dynamics

In this paper, the feedback linearization scheme is applied to the control of vehicle’s lateral dynamics. Based on the assumption of constant driving speed, a second-order nonlinear lateral dynamical model is adopted for controller design. It was observed in (Liaw, D.C., Chung, W.-C. in 2006 IEEE International Conference on Systems, Man, and Cybernetics, 2006) that the saddle-node bifurcation would appear in vehicle dynamics with respect to the variation of the front wheel steering angle, which might result in spin and/or system instability. The vehicle dynamics at the saddle node bifurcation point is derived and then decomposed as an affine nominal model plus the remaining term of the overall system dynamics. Feedback linearization scheme is employed to construct the stabilizing control laws for the nominal model. The stability of the overall vehicle dynamics at the saddle-node bifurcation is then guaranteed by applying Lyapunov stability criteria. Since the remaining term of the vehicle dynamics contains the steering control input, which might change system equilibrium except the designed one. Parametric analysis of system equilibrium for an example vehicle model is also obtained to classify the regime of control gains for potential behavior of vehicle’s dynamical behavior.     

基于ED-LSTM的智能汽车神经网络横向动力学建模与控制

车辆动力学建模过程中通常会进行简化和假设, 导致模型在某些工况下无法准确反映车辆的实际动态特性, 影响控制精度甚至安全性. 鉴于此, 该文提出了一种基于数据驱动的非线性建模与控制方法, 建立了新型神经网络车辆横向动力学多步预测模型, 实现了智能汽车对参考轨迹的跟踪控制. 首先, 在分析车辆单轨模型并考虑轮胎非线性和纵向负载转移的基础上, 基于编码器?解码器结构设计神经网络横向动力学模型. 其中, 使用串行排列来扩展微分方程描述不完全的动力学信息, 隐藏层神经元学习车辆的高度非线性和强耦合特性, 进而提高模型全局计算精度. 利用所构建的数据集进行模型训练和测试, 结果表明, 相比于物理模型, 所提出的模型在不同路面附着系数条件下均具有更高的建模精度, 具有隐式预测路面摩擦条件能力. 其次, 利用提出的模型设计轨迹跟踪控制算法, 根据车辆稳态转向假设, 计算所需的前轮转向角和稳态质心侧偏角, 将稳态质心侧偏角纳入基于路径误差的转向反馈中, 实现参考轨迹跟踪控制. 最后, 使用CarSim/Simulink联合仿真及HIL实验测试进行不同工况试验的对比分析, 对所提出的基于神经网络模型的控制算法进行评价, 结果表明, 该模型能够实现智能汽车在高速下精确的跟踪控制效果, 并具有良好的横向稳定性.      

Interaction of torsion and lateral bending in aircraft nose landing gear shimmy

In this paper we consider the onset of shimmy oscillations of an aircraft nose landing gear. To this end we develop and study a mathematical model with torsional and lateral bending modes that are coupled through a wheel-mounted elastic tyre. The geometric effects of a positive rake angle are fully incorporated into the resulting five-dimensional ordinary differential equation model. A bifurcation analysis in terms of the forward velocity and the vertical force on the gear reveals routes to different types of shimmy oscillations. In particular, we find regions of stable torsional and stable lateral shimmy oscillations, as well as transient quasiperiodic shimmy where both modes are excited.     

流体润滑状态下磨粒尺寸对液压泵磨损的影响

本文研究了流体润滑状态下磨粒尺寸对液压泵磨损的影响。结果表明,在液压系统中,泵的磨损主要决定于磨粒与泵内关键运动副动态间隙之间的尺寸关系:尺寸小于动态间隙的磨粒影响很小;尺寸明显比动态间隙大的磨粒不会对泵产生磨损作用;尺寸与动态间隙很接近的磨粒能使泵发生严重磨损。作者还利用扫描电子显微镜对流体润滑状态下三体磨粒磨损中的磨屑形貌进行了观察与分析,并且提出了控制液压系统中磨粒损磨的可行施措。     

Design of lightweight robots for over-snow mobility

Snowfields are challenging terrain for lightweight (<50 kg) ground robots. Deep sinkage, high snow-compaction resistance, traction loss while turning and ingestion of snow into the drive train can cause immobility within a few meters of travel. However, for suitably designed vehicles, deep snow offers a smooth, uniform terrain that can obliterate obstacles. Key requirements for good over-snow mobility are low ground pressure, large clearance relative to vehicle size and a drive system that tolerates moist, compactable snow.A small robot will invariably encounter deep snow relative to its ground clearance and thus must travel over the snow rather than gain support from the underlying surface. This can be accomplished using low-pressure tracks (<1.5 kPa). Even still, snow-compaction resistance can exceed 20% of vehicle weight. Also, despite relatively high traction coefficients for low track pressures, differential or skid steering is difficult because the outboard track can easily break traction as the vehicle attempts to turn against the snow. Short track lengths (relative to track separation) or coupled articulated robots offer steering solutions for deep snow.This paper presents guidance to design lightweight robots for good mobility over snow based on tests of two custom-designed over-snow robots, SnoBot and SnoBot-2, and driving experience with two commercially available robots, PackBot and Talon. Moreover, we used the present guidance to design SnoBot-2, and it displays excellent over-snow mobility. Because many other considerations constrain robot designs, this guidance can also help with development of winterization kits to improve the over-snow performance of existing robots.     

Vehicle dynamics—Steering I

The consistent theme running through the Vehicle Dynamics—Steering sessions at the 1990 ISTVS Conference was more sophisticated analysis applied to off-road vehicle problems. Of particular note was the gradual progress being made with improvements to the modelling of tracked vehicle steering, including some promising work by Ehlert et al. in verifying model predictions against measured results. State-of-of-art computer software for multibody system dynamics problems was reviewed by Xie and Claar with reference to a tractor-trailer problem. Throughout the papers, in these sessions, it is clear that improved software packages for dynamic analysis are responsible for raising the level of analytical sophistication applied to off-road vehicle design.