基于Matlab与Labview的柔索并联机器人监控系统联合仿真

针对柔索并联机器人的结构特点,搭建了该机器人监控系统的总体框架。考虑到柔索并联机器人系统具有非线性强、外界干扰等特性,提出带有模糊补偿的自适应控制算法。进一步,通过Matlab与LabVIEW混合编程对柔索并联机器人进行了运动轨迹跟踪的联合仿真、监控界面的设计及网络发布。联合仿真结果表明,柔索并联机器人监控系统具有良好的轨迹跟踪性能,且监控人机界面友好,仿真效果较为直观明显。     

Conditions for parallel realizable configurations in synthesis of constraint-based flexure mechanisms

In synthesis of flexure mechanism, parallel arrangement is paid more attention due to its advantages, such as compact structure and higher stiffness. Researchers have derived many parallel flexure mechanisms, but seldom discuss which kind of flexure mechanism can be realized via fully parallel arrangement. The realizable conditions proposed in current work are complicated to engineering applications. To solve two problems on how to judge whether a flexure mechanism can be realized via fully parallel arrangement and how to realize those flexure mechanisms which cannot be realized via fully parallel arrangement, the algebraic condition is derived to judge whether a freedom space is parallel realizable after introducing the definition of parallel realizable and some propositions, and the condition is there exist 6-n independent line constraints in constraint space reciprocal to dimensional freedom space. Then the realizable constraint spaces reciprocal to freedom spaces with 1-3 dimensions are provided. As a result, not all freedom spaces are parallel realizable. For freedom spaces that are not parallel realizable, the criterion of decomposing DOF is proposed to achieve all motion patterns via parallel or hybrid arrangement, that is a high dimensional freedom space can be realized via combining several low dimensional freedom spaces which are parallel realizable. Specific decomposing strategies for 4 and 5 DOF are provided and a complete flowchart is presented to guide designing flexure mechanisms, particularly those which are not parallel realizable. As case studies, synthesis processes of two helical and 3T1R motions are provided to illustrate the proposed approach. The proposed method provides a feasible approach to realize all motion patterns.     

A novel dynamic model for multiple configurations of machine tools using a coordinate transformation method

Virtual machine tools have been used widely for simulating designs in computer environments to determine optimal design parameters without the need for manufacturing prototypes. Machine tools include different multiple configurations that are designed to be suitable for the differing requirements of production. To date, studies on dynamic analysis have been limited to a few-axis machine tools of a specific configuration, such as a 3-axis milling machine or a 4-axis grinding machine. Here, we propose a novel method to focus on the dynamic analyses of multi-axis machines with differing multiple configurations. The motion equations for multiple degrees of freedom of linear and rotary axes are established by a Lagrange energy method, equilibrium equations, and Newton’s second law. This technique formulates the motion equations for each axis, and then further develops them for a multi-axis machine through a combination process and a transformation matrix. The library includes five dynamic model components, built to simulate 1236 different configurations of a machine tool. A dynamic analysis was applied to a control system to simulate the control signals of a virtual machine, which include stepped, ramped, curved, sinusoidal, and circular responses, and frequency response functions. The simulated and experimental results demonstrated that the method has high accuracy and reliability for one-, two-, and four-axis machine tools. Thus, this method can simulate the dynamic analyses of multi-axis machines and different multi-configurations without the need to build a specific configuration for each machine. It is recommended for selecting optimal motors, design parameters, and control parameters of the multiple configurations in a machine tool.     

基于并行计算的平面可调七杆机构动力学解析模型研究

基于运动学分析、凯恩动力学方程及数字-符号法,提出采用并行计算建立平面可调七杆机构动力学解析模型的方法,并研究了构件杆长及惯性参数变化对驱动力/力矩的影响.利用封闭矢量法对平面可调七杆机构进行运动学分析,得到各构件的速度和加速度表达式;将独立广义坐标、杆长及惯性参数作为符号量,其余参数处理为数值量,导出动力学解析模型的数字-符号表达式,并构造了解析模型的并行算法.由于动力学模型及实时代码优化是离线建立的,并且采用并行计算结构,减少了在线计算时间,从而为实时控制打下了基础.给出的仿真实例证明了此方法的有效性.     

A scheduling model for serial jobs on parallel machines with different preventive maintenance (PM)

In factories during production, preventive maintenance (PM) scheduling is an important problem in preventing and predicting the failure of machines, and most other critical tasks. In this paper, we present a new method of PM scheduling in two modes for more precise and better machine maintenance, as pieces must be replaced or be repaired. Because of the importance of this problem, we define multi-objective functions including makespan, PM cost, variance tardiness, and variance cost; we also consider multi-parallel series machines that perform multiple jobs on each machine and an aid, the analytic network process, to weight these objectives and their alternatives. PM scheduling is an NP-hard problem, so we use a dynamic genetic algorithm (GA) (the probability of mutation and crossover is changed through the main GA) to solve our algorithm and present another heuristic model (particle swarm optimization) algorithm against which to compare the GA’s answer. At the end, a numerical example shows that the presented method is very useful in implementing and maintaining machines and devices.     

基于并行计算的平面可调五杆机构动力学解析模型与仿真

基于凯恩动力学方程、数字-符号方法和并行计算建立了杆长和惯性参数可变平面可调五杆机构的动力学解析模型,并对驱动构件质量和杆长对驱动力/力矩的影响进行了仿真分析。将动力学模型的推导问题转化为特定条件下运用运动学和动力学计算公式求解机构驱动力矩的问题,并将广义坐标以及驱动构件杆长和惯性参数作为符号量,导出了模型矩阵元素数字-符号表达式。     

Wavelet spectrum analysis approach to model validation of dynamic systems

Feature-based validation techniques for dynamic system models could be unreliable for nonlinear, stochastic, and transient dynamic behavior, where the time series is usually non-stationary. This paper presents a wavelet spectral analysis approach to validate a computational model for a dynamic system. Continuous wavelet transform is performed on the time series data for both model prediction and experimental observation using a Morlet wavelet function. The wavelet cross-spectrum is calculated for the two sets of data to construct a time-frequency phase difference map. The Box-plot, an exploratory data analysis technique, is applied to interpret the phase difference for validation purposes. In addition, wavelet time-frequency coherence is calculated using the locally and globally smoothed wavelet power spectra of the two data sets. Significance tests are performed to quantitatively verify whether the wavelet time-varying coherence is significant at a specific time and frequency point, considering uncertainties in both predicted and observed time series data. The proposed wavelet spectrum analysis approach is illustrated with a dynamics validation challenge problem developed at the Sandia National Laboratories. A comparison study is conducted to demonstrate the advantages of the proposed methodologies over classical frequency-independent cross-correlation analysis and time-independent cross-coherence analysis for the validation of dynamic systems.     

Assessing the structural complexity of manufacturing systems configurations

Modern manufacturing systems are increasingly required to be flexible and adaptable to changing market demands, which adds to their structural and operational complexity. One of the major challenges at the early design stages is to select a manufacturing system configuration that both satisfies the production functional requirements and is easy to operate and manage. A new metric for assessing the structural complexity of manufacturing system configurations is presented in this paper. The proposed complexity metric incorporates the quantity of information using an entropy approach. It accounts for the complexity inherent in the various modules in the manufacturing system through the use of an index derived from a newly developed manufacturing systems classification code. The code captures the effect of various component types and technologies used in a manufacturing system on the system’s structural complexity. The presented metric would be helpful in selecting the least complex manufacturing system configuration that meets the requirements. An engine cylinder head production system is used to illustrate the application of the proposed methodology in comparing feasible but different manufacturing system configurations capable of producing the cylinder head based on their structurally inherent complexity.     

Numerical efficiency of CUDA based parallel programming for dynamic analysis of multi-body systems with multi-joints and multi-force elements

The graphic processor unit (GPU) is an ideal solution to problems involving parallel data computations. A serial CPU-based program of dynamic analysis for multi-body systems is rebuilt as a parallel program that uses the GPU’s advantages. We developed an analysis code named GMAP to investigate how the dynamic analysis algorithm of multi-body systems is implemented in the GPU parallel programming. The numerical accuracy of GMAP is compared with the commercial program MSC/ADAMS. The numerical efficiency of GMAP is compared with the sequential CPU-based program. Multiple pendulums with bodies and joints and the net-shape system with bodies and spring-dampers are employed for computer simulations. The simulation results indicate that the accuracy of GMAP’s solution is the same as that of ADAMS. In the net type system that has 2370 spring-dampers, GMAP indicates an improved efficiency of about 566.7 seconds (24.7% improvement). It is noted that the larger the size of the system, the better the time efficiency.     

Criteria of dynamic and kinematic synthesis of parallel mechanisms

The criteria of dynamic and kinematic synthesis are discussed as well as the constraints imposed by kinematic chains of parallel mechanisms. They are to provide the synthesis of these objects on the basis of the most complete consideration of their various properties. Some results obtained earlier are generalized here.     

并联机构动力学建模及控制策略的研究

在总结并联机构动力学分析目标的基础上,对并联机构的动力学建模方法,包括拉格朗日方法、牛顿-欧拉法、虚功原理、凯恩方程法等进行了比较研究,并对控制策略的研究现状进行了综述。     

并联机构动力学建模及控制研究

为了系统地研究并联机构动力学特性,分析了4种基本建模方法（牛顿-欧拉方法、直接拉格朗日方法、拉格朗日-达朗贝尔方法和虚功原理方法）,总结了各种方法的优缺点。在此基础上,对动力学的3种控制算法（经典PD控制、机器人控制中常用的计算力矩控制以及数控加工中的先进轮廓控制）在并联机构上的应用进行了分析研究。针对开发的三自由度（3-DoF）纯平动并联机构Orthopod,采用拉格朗日-达朗贝尔方法进行了动力学建模,并对其进行了控制仿真。研究结果显示,轮廓控制在轮廓误差控制方面具有更好的性能,适合于雕刻机的控制应用。     

并联测量机柔性动力学建模与误差耦合

为解决目前高速机构存在的高速与高精度之间的矛盾,研究了高速并联测量机的柔性问题。应用弹性梁运动学理论和Galerkin模态截断法推导了一维弹性梁运动学变形位移模型;以欧拉-贝努利梁为假设,应用Hamilton原理建立了考虑中线变形的柔性结构耦合动力学模型。最后,基于中线耦合动力学模型,测试了不同速度下弹性振动产生的误差,提出了通过调节黏滞摩擦系数来降低振动耦合误差,进而提高测量精度的方法。基于仿真实验验证了提出方法的有效性和可行性。结果表明:在忽略结构误差前提下,角速度为300rad/s时产生的横向一阶振动耦合误差最大值为28.6μm;合理调整黏滞摩擦在0.4~0.5时,振动耦合误差降低至15μm以内,相比调整前误差降低了13.6μm。提出的方法为进一步解决高速与高精度之间的矛盾和研究高阶弹性振动与精度的耦合机理提供了理论基础。     

Analytical determination of principal twists in serial, parallel and hybrid manipulators using dual vectors and matrices

The determination of principal twists of the end-effector of a multi-degree-of-freedom manipulator plays a central role in their analysis, design, motion planning and determination of singularities. Most approaches to obtain principal twists and the distributions of twists, such as the well-known classical results of cylindroid and hyperboloid, are based on geometric reasoning and involve intuitive choice of coordinate systems. In this paper, we present a formal algebraic approach to obtain the principal twists of any multi-degree-of-freedom serial, parallel or hybrid manipulator, by making use of the algebra of dual numbers, vectors and matrices. We present analytical expressions for the principal twists and the pitches for any manipulator of arbitrary degree-of-freedom. A consequence of our approach is that we can obtain analytical expressions for the screws along which a manipulator can lose or gain degrees-of-freedom at a singularity. The theoretical results are illustrated with the help of examples of parallel and hybrid manipulators.     

空间刚柔耦合并联机构的逆动力学建模与控制

为了提高3-RRRU空间刚柔耦合并联机构的轨迹跟踪精度,提出了一种基于瞬态刚体校正法的逆动力学模型求解方法来构建该机构的非线性控制策略。首先,利用自然坐标法和绝对节点坐标法建立该机构的非线性逆动力学模型,它考虑了各支链柔性空间梁单元的剪切效应,并能描述柔性梁的大范围非线性弹性变形。然后,通过分析刚柔耦合动力学模型在求解过程中出现的相容性问题,结合自然坐标法与理想运动学模型,提出了瞬态刚体校正法并求出逆动力学模型的稳定数值因果解。最后,基于该数值解构建并联机构的非线性控制策略,通过仿真与实验验证了该方法的可行性与有效性。仿真与实验结果表明:逆动力学方程组的求解精度为10-6,约束方程的相容误差为10-8;与刚性并联机构的控制方法相比,该方法在圆形轨迹下的最大跟踪误差降低了0.465mm,圆度误差降低了0.416mm。结果表明:该求解方法解决了闭链机构多体动力学方程的违约问题,有效地改善了系统的综合收敛性能,所构建的控制策略提高了并联机构的轨迹跟踪精度。     

MEMS器件与电路共同仿真原型系统

为了预测MEMS器件与电路组成的完整MEMS系统的行为,建立了一个支持MEMS器件与电路共同仿真的原型系统。首先,根据MEMS系统级仿真与模拟电路仿真的共同特性,提出了MEMS器件与电路共同仿真的原理和方法,并依托国产电路仿真平台Zeni VLG建立了共同仿真原型系统的框架结构;然后,分别根据修正节点分析方法和模拟电路行为级建模方法开发了该共同仿真原型系统所必需的两个参数化模型库。通过一个跷跷板式微加速度计分别与其开环电路和闭环带载波电路的共同仿真对原型系统和模型库进行了测试,与国外商业软件Saber对比,开环仿真结果相对误差为2.1%,表明提出的原型系统能够有效进行MEMS器件与电路共同仿真,并且具有较高的精度。     

冗余驱动串并联机器人运动学联合仿真

为了分析冗余驱动对直角坐标串并联机器人的动力学性能的影响,应用ADAMS和MATLAB对其进行了动态联合仿真,通过对已经建立的实体模型和关节运动控制变量的定义,运动轨迹的选取,以及合理选择运动学求解控制算法,最终可以获取动画、平面图形、具体数据等仿真分析结果,联合仿真的方法为复杂机械系统的改进和完善提供了新思路.     

On configurations of symbolic equations of motion for rigid multibody systems

An algorithmic procedure for generating symbolic equations of motion for rigid multibody systems based on a Matrix-Vector approach is presented in this paper. The ease of computation and power inherent in this approach are demonstrated through a series of illustrative examples. Various techniques such as simultaneous generation of second order differential equations of motion and conversion to first order differential equations of motion in Hamiltonian variables, generalized coordinates transformation, order reduction using holonomic and nonholonomic constraint equations and block construction of equations of motion for the compound system from the equations of motion of the sub-systems are described.     

一种刚柔结合并联机构及其动力学分析

并联机构由于铰链的存在,使得其理论上的高精度高刚度的特点受到很大影响.本文在一种4自由度并联机构基础上,附加柔索随动机构,构建了一种刚柔结合的并联机构,通过预紧减少传动间隙,并对新机构的相关特性进行了分析.对该机构采用D-H坐标对该机床各支链进行了表述,采用牛顿-欧拉法建立了机构的动力学模型.最后采用Matlab对该动力学模型进行了仿真分析.