基于滑转率的六轮纵列式月球车驱动控制研究

基于车轮滑转率和车轮地面力学,研究了月球车在松软月面行驶时的车轮过度下陷问题.将 月球车车轮下陷和车轮—土壤作用力表达为车轮滑转率的函数,结合车辆地面力学理论并考 虑纵列式车轮多通过性土壤参数的修正,建立了月球车的动力学模型.判断车轮是否发生过 度下陷的标准为土壤所提供给驱动轮的土壤推力能否克服土壤对车轮的阻力.利用建立的动 力学模型,计算出能够保证车轮不会过度下陷的期望滑转率.考虑到月球车动力学系统的非 线性和不确定性,设计了以车轮滑转率为状态变量的滑模驱动控制器.仿真结果表明,采用 该控制器可以较快地跟踪期望滑转率,避免车轮的过度滑转下陷,保证月球车能够在软质路 面上正常行驶.     

基于地面力学的月球车爬坡轮—地相互作用模型

月球车爬坡地面力学模型在月球车的设计、越障性能评价、控制和仿真等方面具有极其重要作用．利 用月球车轮地相互作用测试系统进行车轮爬坡性能实验,结合实验数据在传统车轮—土壤相互作用应力分布模型之 上推导出爬坡轮—地相互作用模型,同时考虑爬坡角度对浅层月壤应力分布的影响,提出了随滑转率变化的沉陷 因数经验公式,来反映月壤压实、刮带、侧向流动等引起的滑转沉陷．通过对应力分布公式进行积分转化得到集中 力／力矩计算模型,利用ADAMS 二次开发的柔性爬坡仿真环境并结合实验数据进行模型验证．在斜坡角度为16±, 载荷为100 N,当滑转率从0 增加到0.6 时,将模型的车轮斜坡法向载荷、挂钩牵引力和驱动力矩的计算值与实验数 据相对比,结果相对误差不超过10%,因而该爬坡模型可以有效地用于月球车轮地相互作用的力学计算．     

月球车驱动轮爬坡性能的影响因素研究

研究了驱动轮的滑转率、结构参数和载荷对月球车爬坡性能的影响。针对月表复杂路况下车辆通过性较差问题,为提高月球车爬坡性能,基于车辆地面力学中土壤的承压和剪切特性理论,建立了刚性驱动轮与月面斜坡松软月壤间的相互作用模型。通过车轮实例对月球车爬坡性能进行预测和分析。实验结果表明,增大驱动轮的滑转率、半径、宽度、轮刺高度和减小载荷能够增强月球车爬坡能力和提高车轮驱动效率,但随着爬坡能力的增强,车轮驱动效率呈现先增大后减小的趋势。研究结果为月球车轮结构设计以及控制策略的研究提供了参考。     

履带车多刚体建模与仿真分析

首先以车辆地面力学理论为基础,分析了典型的履带与地面相互作用关系及其在RecurDyn/Track(LM)程序中的处理,分别定义了两种典型地面土力学参数,从而建立了基于Bekker理论与Janosi & Hanamoto理论的循环动载荷作用下履带与地面相互作用力学模型;同时分析了履带系统各部件之间的接触力学模型,定义各接触参数及约束关系,从而准确合理地建立了履带车多刚体模型,通过施加运动函数,实现模型在典型地面参数下的行走特性仿真分析,仿真结果与理论分析及实际情况相符合,互为验证,从而为进一步深入研究提供了理论依据与有效分析手段.     

滑转率对月球车车轮驱动力学特性的影响分析

应用车辆地面力学理论研究滑转率对月球车车轮挂钩牵引力、驱动效率以及功率消耗的影响.建立刚性车轮与松软月壤交互作用的动力学模型.通过实例对月球车车轮驱动动力学特性进行仿真分析.研究结果表明,车轮的挂钩牵引力、驱动效率以及驱动能耗均受到车轮滑转率的制约.存在一个最优的滑转率区间,在此区间内车轮可获得较大的挂钩牵引力、较高的驱动效率以及较低的驱动能耗.求取轮、地相对速度,对月球车车轮的地面摩擦力功率进行了估算.     

基于比利时路的某牵引车车架疲劳分析

为分析某牵引车在比利时路上的车架疲劳,建立该牵引车整车多体动力学模型。将试验测得的车轮六分力加载到模型中进行仿真分析,并与试验结果对比,验证模型的可信性。提取多体动力学仿真结果中的车架载荷历程,基于模态应力恢复理论对车架进行疲劳分析,预测车架疲劳寿命。仿真结果表明该分析方法可作为车架疲劳分析的有效手段。     

土壤碰撞问题的刚-散耦合动力学分析

本文以探测器着陆行星土壤为背景,对土壤碰撞问题进行刚-散耦合动力学建模与仿真分析研究.结合离散元方法和多体动力学方法,对半球壳装置土壤跌落问题进行耦合动力学仿真.通过与实验结果及有限元仿真结果对比,验证所采用离散元方法的有效性.分析了颗粒场中颗粒尺寸、恢复系数、静摩擦系数等参数,对碰撞中物体和颗粒场的碰撞加速度、碰撞持续时间、振动波形等动力学响应的影响.本研究将拓展对刚-散耦合动力学问题的理论认识,为探测器着陆系统的设计提供技术支持.     

双轮驱动球形机器人的动力学建模与仿真

针对用于电缆通道环境监测的双轮驱动球形机器人,基于拉格朗日方程实现其动力学建模.通过驱动车轮的转角、球形机器人两自由度位置坐标、驱动车体的姿态角直观的计算出系统的动能和势能;考虑球形机器人位置坐标、驱动车体姿态角、球形机器人运动方向角和左右驱动车轮的转角的约束关系,选择左右驱动车轮的转角、球形机器人的移动距离、驱动车体的姿态角作为广义坐标;考虑驱动车轮和球壳、球壳与地面的摩擦得到系统的广义力和耗散能量,建立了能够描述双轮驱动球形机器人在二维水平面运动、驱动车体姿态的多体动力学.最后,在Matlab/Simulink环境中开展了模型的仿真分析,仿真结果表明所建模型的有效性.     

月球车驱动轮爬坡牵引性能预测

月球表面可通过性较差,预测月球车驱动轮的爬坡牵引性能,对于保证探测工作的正常进行有重要意义。在传统地面车辆理论与研究方法的基础上,考虑斜坡角度对浅层月壤应力分布的影响和轮刺作用,给出了刚性车轮与月壤的相互作用模型。通过实例,计算和分析了不同参数的变化对车轮牵引性能的影响。分析结果表明:车轮的挂钩牵引力和滚动阻转矩受到车轮滑转率、结构尺寸和轮刺高度等参数变化的影响;车轮驱动效率随滑转率变化呈现先增大后减小的趋势,在最优的滑转率区间内能获得较大值。分析结论为月球车车轮的设计和控制提供了参考。     

径向载荷下胎唇对钢制车轮胎圈座作用力分布的影响

针对汽车车轮径向疲劳仿真中传统径向载荷加载方式导致仿真结果误差明显的问题,本文进行了胎唇对钢制车轮胎圈座作用力分布的研究。首先通过径向载荷作用下轮胎变形实验,确定了用于计算胎唇与胎圈座之间作用力的橡胶轮胎材料模型;然后,考虑轮胎变形对轮辋应力分布的影响,进行了车轮径向载荷下的有限元分析;最后,对径向载荷作用下的实验测试数据与装配轮胎模型的车轮径向强度仿真结果、传统加载方式的仿真结果进行了对比分析。研究结果表明,汽车车轮径向疲劳仿真中传统的径向载荷加载分布确实存在明显误差;为获得准确的径向载荷作用下的仿真结果,应使用装配有轮胎的车轮模型。     

松软月面上月球车动力学建模及运动控制研究

通过分析松软月面上车轮下陷原因,建立了车轮与月面相互作用模型,在此基础上对ADAMS进行二次开发,通过等效转换建立了松软月面上月球车仿真模型。由于月球车行走运动时需要考虑能耗、驱动能力等多方面因素,以速度跟踪和驱动能力为控制目标,设计了基于车轮滑转率的协调控制器,并对不同运动工况进行了动力学仿真及分析,验证了所提方法的有效性,为下一步综合设计月球车运动控制策略提供了依据。     

On the cosimulation of multibody systems and hydraulic dynamics

Multibody System Dynamics - The simulation of mechanical devices using multibody system dynamics (MBS) algorithms frequently requires the consideration of their interaction with components of a...     

Multibody System Dynamics: Roots and Perspectives

The paper reviews the roots, the state-of-the-art and perspectives of multibody system dynamics. Some historical remarks show that multibody system dynamics is based on classical mechanics and its engineering applications ranging from mechanisms, gyroscopes, satellites and robots to biomechanics. The state-of-the-art in rigid multibody systems is presented with reference to textbooks and proceedings. Multibody system dynamics is characterized by algorithms or formalisms, respectively, ready for computer implementation. As a result simulation and animation are most important. The state-of-the-art in flexible multibody systems is considered in a companion review by Shabana.Future research fields in multibody dynamics are identified as standardization of data, coupling with CAD systems, parameter identification, real-time animation, contact and impact problems, extension to control and mechatronic systems, optimal system design, strength analysis and interaction with fluids. Further, there is a strong interest on multibody systems in analytical and numerical mathematics resulting in reduction methods for rigorous treatment of simple models and special integration codes for ODE and DAE representations supporting the numerical efficiency. New software engineering tools with modular approaches promise improved efficiency still required for the more demanding needs in biomechanics, robotics and vehicle dynamics.     

Three Approaches for Elastodynamic Contact in Multibody Systems

In machine dynamics impacts may occur by interaction of solid bodies. There is no doubt that the method of multibody systems is most efficient for the dynamical analysis of the overall motion. However, during impact energy is lost macromechanically measured by the coefficient of restitution. This coefficient has to be estimated from experiments and experience but cannot be computed within the multibody system approach. The impacts, on the other hand, are generating waves in the bodies which are propagating until they are vanishing due to material damping. These high frequency phenomena are analyzed using wave propagation, modal approach and finite elements. The results of the simulation on the fast time scale are used to compute the coefficient of restitution which is then fed back to the multibody system equations and the solution continues on the related slow time scale. The efficiency of the approach presented is shown for the impact of a steel sphere on four different shaped aluminum bodies of comparable mass. The simulation results are verified with experiments performed on different time scales, too. Using the impact of a double pendulum on a stop as example, the application of the multiscale approach to a multibody system is shown.     

A novel micromechanical model of nonlinear compression hysteresis in compliant interfaces of multibody systems

A micromechanical model of nonlinear hysteretic compression between interacting bodies of multibody systems, covered with fibrous structures, has been created and validated experimentally in this work. As an application, a multibody dynamic model of an upright piano action mechanism with felt-covered contacting bodies is considered, and the obtained results were verified using experiments. Felt, as a typical nonwoven fiber assembly, has been used in various contact surfaces of piano action mechanisms to transfer the force applied on the key to other components, smoothly and continuously. To keep the simulation time tractable in the mechanistic multibody dynamic model, interaction between felt-lined interfaces has to be simplified enough so that in each step of simulation time, contact forces can be calculated as a function of penetration depth between colliding objects. The developed micromechanical approach is capable of estimating nonlinear bulk response of felt in terms of microstructural parameters of the network, assuming a binomial distribution of the number of fiber contacts and bending of constituent fibers. Hysteresis is included based on a fiber-to-fiber friction approach, which generates a speed-independent response to compressive loading schemes, as has been observed in experiments. A computational algorithm is introduced to apply the sophisticated hysteretic micromechanical model to the multibody systems simulation, including transitions between loading–unloading stages.     

Interaction of flexible multibody systems with fluids analyzed by means of smoothed particle hydrodynamics

The present work deals with a computational approach to fluid-structure interaction (FSI) problems by coupling of flexible multibody system dynamics and fluid dynamics. Since the methods for the numerical modeling are well known, both for the structural and the fluid part, the focus of this work lies on the coupling formalism. Moreover, the applicability of the presented approach to arbitrary geometries and high structural stiffness is studied, as well as an easy model setup. No restriction should be made on the topology of the structure or the complexity of motion.For the fluid part a meshless method, known as smoothed particle hydrodynamics (SPH) is applied, which fulfills the above requirements. While an explicit time integration scheme in SPH provides a fast simulation of the fluid dynamics, advanced methods from flexible multibody dynamics provide a variety of benefits for the simulation of the solid part. Amongst these are specialized structural finite elements for both small and large deformation bodies, joints, stable implicit time-integration schemes, and model reduction techniques.A rule for the interaction between fluids and structures is derived from imposing a distributed potential over boundary segments of the structures, which the fluid particles respond to. The work is concluded by illustrative examples, demonstrating the successful coupling of flexible multibody systems with fluids.     

虚拟原型多体动力学中设计模式仿真模型研究

通过分析机械系统多体动力学解算模型特点。从机械产品的协作开发与仿真角度。研究了基于组件方法建立机械系统虚拟原型,提出利用MVC设计模式构建多体动力学解算仿真模型。这种解算模式,实现了多体动力学解算仿真中。模型与解算逻辑的分离,维护了系统仿真中构件、铰约束、力元等组件的状态一致性。利于在不同的解算逻辑下组件和仿真方案的配置,方便了基于组件的协同开发与仿真。结果表明,基于组件的机械虚拟原型模型与多体动力学MVC仿真模型是可行的。     

A criterion on inclusion of stress stiffening effects in flexible multibody dynamic system simulation

This paper presents a criterion on inclusion of stress stiffening effects in dynamic simulation of flexible multibody systems. The proposed criterion examines numerically the eigenvalue variation of the total modal stiffness matrix that is a combination of the modal stress stiffness matrix and the conventional linear modal stiffness matrix prior to actual dynamic simulation. If the variation is sufficiently large for any flexible body in the multibody system, then stress stiffening effects must be included in dynamic simulation of flexible multibody systems for accurate prediction of dynamic behavior. Since the criterion uses the most general stress stiffness matrix contributed from applied and constraint reaction loads as well as from a system of 12 inertial loads, this criterion is applicable to any general flexible multibody dynamic system. Several numerical results are presented to show the effectiveness of the proposed criterion.     

Towards dynamics of controlled multibody systems with magnetostrictive transducers

The paper addresses mechatronic issue of multibody systems comprising giant magnetostrictive material based transducers (sensors and/or actuators). Interaction between dynamics and control in multibody system with smart material based transducers makes it possible to change system properties and functionality substantially as a response to applied electric, magnetic or temperature fields. To use this interaction in an optimal way, the proper mathematical models of controlled electro-magneto-elastic multibody systems need to be developed. In the paper, a general mathematical model of multibody systems with magnetostrictive transducers is presented. The model consists of the constitutive equations of magnetoelastic behavior of transducers, standard formulae of electromagnetism for induced voltage and current in the pick-up coil due to variation of magnetic field intensity, and finally, the equations of motion of multibody system itself. The last one can be derived using one of the well-known multibody dynamics formalisms. General model has been developed in detail for linearized dynamics of magnetostrictive transducers and implemented virtually for two practically important cases of interaction of hosting multibody system with transducers, namely for systems with displacement driven transducers and for systems with force driven transducers. Physical prototype of magnetostrictive transducer and test rig (hosting multibody system) have been built and used successfully for verification of developed models.