Robust control design for a wheel loader using and feedback linearization based methods

The heavy equipment industry is building more and more equipment with electro-hydraulic control systems. The existing industry practices for the design of control systems in construction machines primarily rely on classical designs coupled with ad-hoc synthesis procedures. Such practices produce desirable results, but lack a systematic procedure to account for invariably present plant uncertainties in the design process as well as coupled dynamics of the multi-input multi-output (MIMO) configuration. In this paper, two H_∞ based robust control designs are presented for an automatic bucket leveling mechanism of a wheel loader. In one case, the controller is designed for the base plant model. In another case, the controller is designed for the plant with a feedback linearization control law applied yielding improved stability robustness. A MIMO nonlinear model for an electro-hydraulically actuated wheel loader linkage is considered. The robustness of the controller designs are validated by using analysis and by simulation using a complete nonlinear model of the wheel loader linkage and hydraulic system.     

一种步行机构的图谱辅助综合法

首先采用一种Ｓｔｅｐｈｅｎｓｏｎ型六杆机构作为机器人的步行机构，然后根据足端的相对轨迹要求，借助于铰链四杆机构的连杆曲线图谱求找该步行机构的初始尺寸。在此基础上，利用优化设计方法对机构的全部尺寸进行了精化。最后完成了整个机构的设计。     

Feasible parameter design spaces for force and root-mean-square moment balancing an in-line 4R 4-bar synthesized for kinematic criteria

The paper contains application oriented additions to the theory developed by Berkof and Lowen for root-mean-square (RMS) shaking moment optimization of a force balanced in-line 4R 4-bar linkage. The theory is extended to the problem of force-RMS moment balancing by mass redistribution when all link length ratios are fixed to satisfy kinematic design criteria. Feasible parameter design spaces and parameter inter-relationship monographs are presented. These aid in the selection of numerical values for five of the eight design parameters so that the three balancing equations can be solved for physically realistic values of the remaining three parameters.     

可控连杆机构系统预定轨迹下的动态优化综合

以两自由度可控连杆机构系统为研究对象,在所建系统机电耦合动态模型的基础上,考虑了系统结构参数和控制电机的电磁参数对连杆中点的动态响应的影响。针对系统预定圆轨迹下的动态响应,建立了参数优化数学模型。采用基于混沌的粒子群优化算法,实现了系统动态性能优化。     

Multicriterion optimization of the kinematics of the spatial mechanisms of passenger car wheel suspensions

Four spatial mechanisms simulating passenger car wheel suspensions and steering linkages and power drives are considered. A structural analysis of the mechanisms is provided. A method for calculating the coordinates of characteristic points and the main kinematic characteristics of these mechanisms is proposed. The problem of multicriterion optimization of the kinematic characteristics is defined. A subproblem of the multicriterion optimization consists in the synthesis of a mechanism ensuring the required motion of a wheel. Some optimization results are presented.     

Grinding force and power modeling based on chip thickness analysis

The ability to predict grinding force and power is important to many aspects of grinding process optimization, monitoring, and control. This paper presents the predictive modeling of grinding force and power based on the probabilistic distribution of undeformed chip thickness as a function of the kinematic conditions, material properties, wheel microstructure, and dynamic effects. The chip thickness is the main random variable and it is expected to assume a Rayleigh probability density function. The model takes into account the microstructure of the grinding wheel given by the grain geometry and the static grain density in terms of the radial depth into the wheel. The dynamic cutting edge density was calculated incorporating the effects of kinematic and dynamic phenomena such as the kinematic hidden grains and the local grain deflection. The elastic deformation of the grinding contact length was also considered. The model was used to predict the total tangential and normal forces in surface grinding and the total grinding power in cylindrical grinding. In both cases experimental measurement data in the context of chip thickness probability density, tangential force, normal force, and power have been presented and compared to model calculations.     

单排连续切换全向轮移动机器人的布局方式与运动的稳定性分析

研讨了一种单排的连续切换全向轮及其全方位移动机器人的全向轮布局选择与运动时的稳定性问题,提出了一种单排的连续切换全向轮的结构,并基于此结构建立了移动机器人系统的运动学模型,通过解析系统速度逆雅可比矩阵的秩,得到了系统实现全方位运动的条件,分析给出了实现全方位运动所需的三轮、四轮的布局方式。同时,根据非完整系统的劳斯方程,建立了全向轮机器人的动力学方程,计算了车体在斜坡上运动时不发生后翻和侧翻的条件,并用ADAMS软件进行仿真验证了模型。研究为此类系统的设计和控制提供了理论基础。     

机械式娱乐机器人手臂联动机构的设计与研究

针对目前娱乐机器人多自由度手臂机构设计存在成本高、发展速度缓慢等问题提出机械式手臂联动机构,即利用六杆机构实现手臂前、后、左、右同步或交错摇摆,从而完成鼓掌、欢呼的动作。将优化设计思想与Matlab相结合,利用外惩罚函数法对两次简化后的手臂异步联动进行建模优化,求解出参数并用分支定界法确定杆件参数;利用控制变量法对手臂同步联动进行参数优化,以SolidWorks、ADAMS软件为工具,建立其仿真模型,进行运动学仿真,结果显示,优化设计的六杆机构异步联动行程比系数最优、同步联动两臂相位差最小,能很好地满足机器人手臂娱乐需要。最终从六杆机构参数映射到手臂联动机构,为娱乐机器人手臂联动机构的设计和计算提供参考。     

八连杆轮式装载机动臂的结构分析与设计改进

对八连杆装载机动臂的结构特点与承载特点进行了全面分析,总结出装载机八连杆动臂在作业过程中遇到的铲入正载、铲入偏载、掘起正载、掘起偏载四种工况及各工况下承受的载荷特点。然后利用先进的CAE分析软件ANSYS软件,建立了动臂的有限元计算模型,并计算出各工况下动臂的应力分布云图。经过对动臂四种工况的有限元分析结果研究,分析出了导致动臂变形反馈的根本原因,并就此提出了动臂结构的改进方案。校核改进后动臂的强度,比改进前提高了27%,从而改善了动臂性能,同时此种思路也为以后的设计提供了参考。     

平面四杆机构轨迹近似综合的全方案优选

本文将连续法与优化理论相结合，首次解决了平面四杆机构轨迹近似综合的全方案优选问题。文中首先将四杆机构拆分成主、从两支并分别建立各支优化的目标函数；然后用连续法依次求出主、从支优化目标函数对应梯度方程组的全部解，进而得到每个目标函数的全部极小值点（即优化问题的全部解），排除没有物理意义的解，得到主、从两支的全部方案；最后将主、从支进行组合便得到能近似实现给定轨迹点的全部机构方案。     

Partial balancing of the shaking force of a spatial 4-bar RCCC linkage by the optimization methodчacтичнoe ypaвнoвeщивaниe peзyльтиpyющeй cилы инepции пpocтpaнcтвeннoгo чeтыpexзвeннoгo мexaнизмa

In order to obtain partial balancing of the shaking force of a spatial 4-bar RCCC linkage, three counterweights are attached to moving links of the RCCC linkage respectively and optimal vectors of the position of the counterweights are computed by optimization procedure BFS or BFGS (Broyden-Fletcher-Goldfarb-Shanno), which is a variable metric method. In this way, the RMS norm of the shaking force of the RCCC linkage is reduced by half.     

Generalized study of crank-rocker mechanisms driven by a d.c. motor Part I. Mathematical model

A mathematical model is developed for analyzing a 4-bar linkage driven through a speed reducer by a separately-excited d.c. motor. A set of nonlinear differential equations, governing the dynamic response of this system, is derived and converted to dimensionless form. This dimensionless form is described by newly defined linkage and drive parameters. It is believed that these parameters may find convenient use in estimating the overall behavior of motor-mechanism systems from performance graphs and guidelines which can be established by numerical study of typical cases.

The performance characteristics which are considered in this analysis are the steady-state speed fluctuation of the mechanism and its steady-state energy consumption as well as the time required for mechanism “start-up” and the energy consumption during start-up. Expressions are derived in a dimensionless form to represent these performance characteristics. In Part II of this paper, specific numerical examples are presented which relate the performance characteristics to the linkage and drive parameters for two different mechanisms.     

基于能耗指标的拟人机器人步态优化与分析

通过引入基于平均功率、平均功率偏差、平均力矩损耗三个能耗指标对拟人机器人步态进行了优化与分析.基于拉格朗日方程推导了各个关节驱动力矩的计算公式,建立了拟人机器人步态优化的数学模型.使用Matlab作为优化与仿真工具,得到了一組拟人机器人步态参数最优解,分析了拟人机器人各个步态参数与拟人机器人能量消耗之间的关系.并给出了拟人机器人步态优化与分析的数值实例.     

平面连杆机构的计算机辅助设计

所介绍的自行开发的平面连杆机构计算机辅助设计系统，能对常用的平面连杆机构进行运动分析及综合。阐述了该系统的结构，系统设计的原则、设计目标以及有关的建模与求解方法，最后给出一个应用实例。     

Multibody approach for tolerance analysis and optimization of mechanical systems

A multibody approach is suitable for tolerance analysis of mechanical systems since multibody formulation can directly consider part-level tolerance variables. In this study, procedures for performing tolerance analysis and corresponding sensitivity analysis for spatial multibody systems are proposed. First, statistical formulation for performing multibody system tolerance analysis is developed to obtain system level tolerance for given part-level tolerances. One very useful aspect of the proposed formulation is that in the process of computing system tolerance, the sensitivity of system tolerance with respect to part-level tolerances can be additionally obtained. The kinematics of spatial multibody systems has been redefined in terms of both generalized coordinates and part-level tolerance variables. Tolerances in geometry of a body are specified in terms of the variations in relative locations of joint definition points and relative distance between them. Tolerances in the joint kinematics are defined through variations in vector closure equations and orthogonality equations that are two fundamental constraint equations for most kinematic joints. To demonstrate the validity and effectiveness of the proposed tolerance analysis procedure, tolerance analysis of a spatial 4-bar mechanism and tolerance optimization are performed.     

Kinematics and dynamics analysis of the 3PUS-PRU parallel mechanism module designed for a novel 6-DOF gantry hybrid machine tool

A hybrid kinematic machine (HKM) tool with the respective advantages of serial and parallel mechanism is a significant direction for the innovation and development of current advanced sophisticated manufacturing equipment. This paper considers the configuration design, kinematics analysis and dynamics analysis of a 1-translational-3-rotational (1T3R) parallel manipulator, which acts as the main movement module of a novel 6-DOF reconfigurable HKM. The key parallel manipulator with 4 DOFs is composed of one middle PRU kinematic chain and three identical PUS kinematic chains. First, complete kinematics characteristics, including position, velocity, acceleration and jerk, are deeply analyzed by a vector analysis approach. Reachable position workspace and orientation workspace were derived through the workspace boundary search method. Furthermore, complete inverse dynamics model of the 3PUS-PRU parallel manipulator was formulated by virtue of the virtual work principle with considering the inertial and gravitational properties of struts. Finally, a driving power and energy consumption model of each actuated motor under the prescribed trajectory were obtained, resulting in the decouple contribution of each motion part correspondingly. This systematic and rigorous methodology aims at laying a solid theoretical and technical foundation for configuration design and performance analysis of this homologous type HKM.

     

Comprehensive optimum and adaptable design methodology for the working mechanism of a wheel loader

The working mechanism is an important part of a wheel loader. It is used to accomplish the shoveling, loading, lifting, and dumping tasks. Usually, the working mechanism is a Z-bar linkage and the dimensional design of the linkage directly affects the loader’s service performance, such as dumping clearance and dumping height. As there are many other performance indexes and various field requirements for the loader, comprehensive optimum, and adaptable design methodology with full-parameterized kinematic model attracts engineers’ research interests. Focusing on the multi-objective and multi-variable problems, this paper firstly establishes an accurate and simplified kinematic model of the Z-bar linkage with deduced expression of the basic parameters, and then investigates the performance indexes including mechanism transmission ratio, lifting stationary, dumping angle in any position, bucket flat setting, and extreme transmission angle, etc. With the full-parameterized kinematic model and the optimum algorithm, modified complex method, a comprehensive and adaptable design platform is built to solve the multi-objective and multi-variable problems of the Z-bar linkage. A case study with two optimization schemes as “full variables design” and “partial variable design” is conducted. The simulation results show that both schemes are better than the original one. The methodology and platform in this paper are of importance in generating user requirement oriented linkage design schemes with enough consideration and optimization of multiple performance indexes.     

Error analysis and optimization of a 3-degree of freedom translational Parallel Kinematic Machine

In this paper, error modeling and analysis of a typical 3-degree of freedom translational Parallel Kinematic Machine is presented. This mechanism provides translational motion along the Cartesian X-, Y- and Z-axes. It consists of three limbs each having an arm and forearm with prismatic-revolute-revolute-revolute joints. The moving or tool platform maintains same orientation in the entire workspace due to its joint arrangement. From inverse kinematics, the joint angles for a given position of tool platform necessary for the error modeling and analysis are obtained. Error modeling is done based on the differentiation of the inverse kinematic equations. Variation of pose errors along X, Y and Z directions for a set of dimensions of the parallel kinematic machine is presented. A non-dimensional performance index, namely, global error transformation index is used to study the influence of dimensions and its corresponding global maximum pose error is reported. An attempt is made to find the optimal dimensions of the Parallel Kinematic Machine using Genetic Algorithms in MATLAB. The methodology presented and the results obtained are useful for predicting the performance capability of the Parallel Kinematic Machine under study.     

基于UG NX的双横臂独立悬架转向系统的仿真分析及优化

利用UG NX软件建立某客车双横臂独立悬架转向系统模型。基于NX CAD/Motion/Natran协同仿真平台,对转向系统结构进行系统动力学仿真,绘制前束角变化曲线,同时对内、外侧前轮转向角关系仿真曲线与阿克曼理论曲线进行对比分析。运用NX/Nastran与NX/Motion共同建立刚柔混合模型并对转向节臂进行柔性分析和拓扑优化。     

Testing a 32-channel integrated circuit for recording signals of silicon detectors

A 32-channel integrated microcircuit for microstrip silicon detectors of the ??Nuklon?? project for studying ionizing radiation in space conditions is tested. The microcircuit allows one to record signals of relativistic particles and nuclei with a charge from Z = 1 up to Z > 50 from silicon detectors. A structural diagram of the microcircuit and its main experimental characteristics are given. The power consumption does not exceed 1.5 mW/channel, and the dynamic range of recorded signals is not smaller than 100 pC.