A Finite and Instantaneous Screw Based Approach for Topology Design and Kinematic Analysis of 5-Axis Parallel Kinematic Machines

Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for both finite and instantaneous motions are performed by the same mathematical tool. Based upon finite and instantaneous screw theory, a unified and systematic approach for topology design and kinematic analysis of PKMs is proposed in this paper. Using the derivative mapping between finite and instantaneous screws built in the authors’ previous work, the finite and instantaneous motions of PKMs are analytically described by the simple and non?redundant screws in quasi?vector and vector forms. And topological and parametric models of PKMs are algebraically formulated and related. These related topological and parametric models are ready to do type synthesis and kinematic analysis of PKMs under the unified framework of screw theory. In order to show the validity of the proposed approach, a kind of two?translational and three?rotational(2T3R)5?axis PKMs is taken as example. Numerous new structures of the 2T3R PKMs are synthe?sized as the results of topology design, and their Jacobian matrix is obtained easily for parameter optimization and performance evaluation. Some of the synthesized PKMs have outstanding capabilities in terms of large workspaces and flexible orientations, and have great potential for industrial applications of machining and manufacture. Among them, METROM PKM is a typical example which has attracted a lot of attention from global companies and already been developed as commercial products. The approach is a general and unified approach that can be used in the innovative design of different kinds of PKMs.

Atlas Based Kinematic Optimum Design of the Stewart Parallel Manipulator

Optimum design is a key approach to make full use of potential advantages of a parallel manipulator. The optimum design of multi-parameter parallel manipulators（more than three design parameters）, such as Stewart manipulator, relies on analysis based and algorithm based optimum design methods, which fall to be accurate or intuitive. To solve this problem and achieve both accurate and intuition, atlas based optimum design of a general Stewart parallel manipulator is established, with rational selection of design parameters. Based on the defined spherical usable workspace（SUW）, primary kinematic performance indices of the Stewart manipulator involving workspace and condition number are introduced and analyzed. Then, corresponding performance atlases are drawn with the established non-dimensional design space, and impact of joint distribution angles on the manipulator performance is analyzed and illustrated. At last, an example on atlas based optimum design of the Stewart manipulator is accomplished to illustrate the optimum design process, considering the end-effector posture. Deduced atlases can be flexibly applied to both quantitative and qualitative analysis to get the desired optimal design for the Stewart manipulator with respect to related performance requirements. Besides, the established optimum design method can be further applied to other multi-parameter parallel manipulators.

PERFORMANCE ANALYSIS AND KINEMATIC DESIGN OF PURE TRANSLATIONAL PARALLEL MECHANISM WITH VERTICAL GUIDE-WAYS

Performance analysis and kinematic design of the 3-PUU pure translational parallel mechanism with vertical guide-ways are investigated. Two novel performance indices, the critical slider stroke and the main section area of workspace, are defined; The expressions of two other indices, i.e. the global dexterity and global force transfer ratio are revised based on the main section of workspace. Using these indices, performance changes versus the varieties of dimensional parameters of mechanism are investigated in detail and the graphic descriptions of change tendencies of the performance indices are illustrated. By means of these obtained graphic descriptions, kinematic parameters for the 3-PUU pure translational parallel mechanism with better characteristics can be directly acquired.

KINEMATIC DESIGN OF A RECONFIGURABLE MINIATURE PARALLEL KINEMATIC MACHINE

The kinematic design of a reconfigurable miniature parallel kinematic machineis dealt with. It shows that the reconfigurability may be realized by packaging a tripod-basedparallel mechanism with fixed length struts into a compact and rigid frame with which the differentconfigurations can be formed. Utilizing a dual parameter model, the influences of the geometricalparameters on the dexterous performance and the workspace/machine volume ratio are investigated. Anovel global performance index for the dimensional synthesis is proposed and optimized, resulting ina set of dimensionless geometrical parameters.

Optimal Design of a 3-Leg 6-DOF Parallel Manipulator for a Specific Workspace

Researchers seldom study optimum design of a six-degree-of-freedom（DOF） parallel manipulator with three legs based upon the given workspace.An optimal design method of a novel three-leg six-DOF parallel manipulator（TLPM） is presented.The mechanical structure of this robot is introduced,with this structure the kinematic constrain equations is decoupled.Analytical solutions of the forward kinematics are worked out,one configuration of this robot,including position and orientation of the end-effector are graphically displayed.Then,on the basis of several extreme positions of the kinematic performances,the task workspace is given.An algorithm of optimal designing is introduced to find the smallest dimensional parameters of the proposed robot.Examples illustrate the design results,and a design stability index is introduced,which ensures that the robot remains a safe distance from the boundary of sits actual workspace.Finally,one prototype of the robot is developed based on this method.This method can easily find appropriate kinematic parameters that can size a robot having the smallest workspace enclosing a predefined task workspace.It improves the design efficiency,ensures that the robot has a small mechanical size possesses a large given workspace volume,and meets the lightweight design requirements.

DIMENSIONAL DESIGN THEORY AND METHODOLOGY OF 6-DOF SCISSOR PARALLEL MANIPULATOR

Parallel manipulators have many advantages over serial manipulators in termsof high load/weight ratio, velocity, stiffness and precision. A dimensional design theory andmethodology of six degrees of freedom scissor parallel manipulator (SPM) is investigated. The SPMkinematics inverse equation is given. Based on the formulation of the local dexterity and thedefinition about the indexes of workspace incircle radius, the effects of the design parameters onthe dexterity and workspace are discussed. Moreover the incircle radius change ratio about workspaceare defined and used as the evaluated indicator to analyze the effects of the design parameters onthe performances. A dimensional design theory that could satisfy the requirement of dexterity andworkspace is proposed. The dimensional design theory and methodology can be of help in the design,trajectory planning and control of parallel manipulator.

Optimal design of the link lengths for a planar parallel manipulator

This paper addresses geometry design of a new kind of 2-DOF parallel manipulator actuated horizontally by linear actua- tors. The first step of the optimum design involves developing a non-dimensional structure of the planar 2-DOF parallel manipulator. The global conditioning index, global velocity index, global stiffness index and global payload index of the 2-DOF parallel manipu- lators are investigated, and the geometrical parameters without dimension are determined with respect to the specification on per- formances. Finally, based on the optimum non-dimensional result, the optimum dimensional parameters are achieved which is suit- able for the desired workspace. The optimum methodology of this paper is convenient and can be extended to other parallel mecha-

Paralleled DC-DC Power Converters Sliding Mode Control with Dual Stages Design

This paper proposes the new cascaded series parallel design for improved dynamic performance of DC-DC buck boost converters by a new Sliding Mode Control (SMC) method. The converter is controlled using Sliding Mode Control method that utilizes the converter’s duty ratio to determine the skidding surface. System modeling and simulation results are presented. The results also showed an improved overall performance over typical PID controller, and there was no overshoot or settling time, tracking the desired output nicely. Improved converter performance and robustness were expected.

Series-parallel Hybrid Vehicle Control Strategy Design and Optimization Using Real-valued Genetic Algorithm

Despite the series-parallel hybrid electric vehicle inherits the performance advantages from both series and parallel hybrid electric vehicle, few researches about the series-parallel hybrid electric vehicle have been revealed because of its complex co nstruction and control strategy. In this paper, a series-parallel hybrid electric bus as well as its control strategy is revealed, and a control parameter optimization approach using the real-valued genetic algorithm is proposed. The optimization objective is to minimize the fuel consumption while sustain the battery state of charge, a tangent penalty function of state of charge（SOC） is embodied in the objective function to recast this multi-objective nonlinear optimization problem as a single linear optimization problem. For this strategy, the vehicle operating mode is switched based on the vehicle speed, and an ＂optimal line＂ typed strategy is designed for the parallel control. The optimization parameters include the speed threshold for mode switching, the highest state of charge allowed, the lowest state of charge allowed and the scale factor of the engine optimal torque to the engine maximum torque at a rotational speed. They are optimized through numerical experiments based on real-value genes, arithmetic crossover and mutation operators. The hybrid bus has been evaluated at the Chinese Transit Bus City Driving Cycle via road test, in which a control area network-based monitor system was used to trace the driving schedule. The test result shows that this approach is feasible for the control parameter optimization. This approach can be applied to not only the novel construction presented in this paper, but also other types of hybrid electric vehicles.

Inverse kinematic optimal design of 6-DOF parallel manipulators

To obtain the required articular velocities as lower as possible for the given kinematics of the moving platform, this paper focuses on this kind of articular velocities optimization of 6-DOF parallel manipulators. Based on the inverse kinematic analysis, the H∞ norm of the weighted Jacobian matrix was adopted as the performance index to minimize the articular velocities, and then the optimal design problem was formulated to find a manipulator geometry that minimized the global performance index with the constraints of the workspace and structural parameters limits. Since the optimal design problem is a constrained nonlinear optimization problem without explicit analytical expressions, the genetic algorithm was applied to numerically solve the problem. Simulation results indicate that the articular velocities of the optimal manipulators can be the minimum while the kinematic requirements of the moving platform are satisfied.

Combined method for parallel manipulator configuration design

Configuration design is an essential, creative and decision-making step in parallel manipulator design process, in which modeling and assembly are iterative and trivial. Combined approach with automatic parametric modeling and automatic assembly is proposed for parallel manipulator configuration design. The design process and key techniques, such as configuration design, configuration verification, poses calculation of all parts in parallel manipulator, virtual assembly and etc., are discussed and demonstrated by an example. A software package is developed for parallel manipulator configuration design based on the proposed method with Visual C+ + and UG/OPEN on Unigraphics.

A Trace-state Based Approach to Specification and Design of Parallel Programs

In this paper they deal with the issue of specification and design of parallel communicatingprocesses. A trace-state based model is introduced to describe the behaviour of concurrent programs. They presenta formal system based on that model to achieve hierarchical and modular development and verification methods. Anumber of refinement rules are used to decompose the specification into smaller ones and calculate program fromthe

Parallel Processing Design for LTE PUSCH Demodulation and Decoding Based on Multi-Core Processor

The Long Term Evolution (LTE) system imposes high requirements for dispatching delay.Moreover,very large air interface rate of LTE requires good processing capability for the devices processing the baseband signals.Consequently,the single-core processor cannot meet the requirements of LTE system.This paper analyzes how to use multi-core processors to achieve parallel processing of uplink demodulation and decoding in LTE systems and designs an approach to parallel processing.The test results prove that this approach works quite well.

Real-time Parallel Processing System Design and Implementation for Underwater Acoustic Communication Based on Multiple Processors

ADSP-TS101 is a high performance DSP with good properties of parallel processing and high speed.According to the real-time processing requirements of underwater acoustic communication algorithms,a real-time parallel processing system with multi-channel synchronous sample,which is composed of multiple ADSP-TS101s,is designed and carried out.For the hardware design,field programmable gate array(FPGA)logical control is adopted for the design of multi-channel synchronous sample module and cluster/data flow associated pin connection mode is adopted for multiprocessing parallel processing configuration respectively.And the software is optimized by two kinds of communication ways:broadcast writing way through shared bus and point-to-point way through link ports.Through the whole system installation,connective debugging,and experiments in a lake,the results show that the real-time parallel processing system has good stability and real-time processing capability and meets the technical design requirements of real-time processing.

运动解耦且大工作空间三平移机构拓扑设计

根据基于方位特征(POC)方程的并联机构拓扑设计方法和运动解耦设计原理,提出一个运动解耦性优异的单回路三平移子并联机构;设计一类4个具有正向位置符号化、部分运动解耦性且具有较大工作空间的三平移(3T)并联机构;对这类机构进行拓扑特性分析,得到相同的方位特征集(POC)、自由度(DOF)、耦合度(κ)、运动解耦性等主要拓扑特性;对其中一个机构进行运动学、动力学性能分析。根据基于拓扑特征运动学建模原理,求出其符号化位置正反解,以及速度、加速度曲线;基于推导出的位置逆解公式,分析机构的奇异位形及工作空间;根据基于序单开链的虚功原理,进行其动力学建模与分析,求解出机构的驱动力。

PSCAD的发电机准同期并列综合实验设计

针对电力系统自动化实验教学中存在的不足,设计了同步发电机准同期并列综合实验。实验模型采用PSCAD/EMTDC,建立了包含发电机及并网系统、原动机及其调速器、励磁系统、准同期并列控制单元、电压向量的动态显示等关键部件。依托实验模型设计了循序渐进的教学实验项目,主要有机组启动与并网的验证性实验、不同并列条件影响的分析性实验、频率差和电压差调节的设计性实验。该实验将电路、电机学、自动控制理论、电力系统分析等多门专业核心课程贯穿起来,提升了学生综合运用知识解决复杂工程问题的能力。

考虑润滑间隙效应的空间并联机构动力学优化

为了改善润滑间隙效应引起的空间并联机构动态性能的渐变劣化问题,以3-RRPaR冗余并联机构为研究对象,提出一种考虑润滑间隙效应的空间并联机构动力学优化方法。建立了考虑润滑转动副间隙的3-RRPaR冗余并联机构动力学模型;以优化末端执行器的动力学响应误差和优化间隙关节处的约束反力为目的设置目标函数,通过优化末端执行器质量以及转动惯量的方式来缓解运动副间隙导致的劣化效应,建立了考虑润滑间隙效应3-RRPaR冗余并联机构动力学优化模型;试验验证了所建动力学模型的有效性,对比分析两种目标函数对优化效果的影响以选择最佳优化方式,并分析优化前后考虑润滑间隙效应的空间并联机构动力学特性,结果表明动力学优化使润滑间隙转动副处约束反力峰值降低16.16%,为改善间隙效应提高空间并联机构动态性能提供了理论支撑。

平行闸板阀阀座孔加工专用车削刀具设计及实验研究

平行闸板阀被广泛应用在石油钻采配套装备中。采用普通内孔车削刀具加工平行闸板阀阀座孔,需要调头加工,难以使用切削液,并且由于刀杆刚度和硬度较小引起“颤抖”现象,加工工件时不易保证阀座孔的加工质量和形位公差。基于此设计了一套专用车削刀具,增大刀杆的刚度和硬度,方便使用切削液,而且仅需一次装夹,避免掉头加工,以满足阀座孔的形位公差和加工质量要求。采用有限元法对所设计刀具进行了强度校核。通过实验验证,所设计的刀具可以提高加工效率,满足加工质量和形位公差精度要求。

基于结构相似性的并联机构拓扑与尺寸同步设计方法

随着并联机构从单一尺寸设计和拓扑设计向两者融合方向不断发展,基于拓扑叠加-再惩罚和全变量正交设计-再拓扑的同步设计方法得到广泛应用,但两者存在设计效率低等不足。为解决上述问题,本文提出了一种基于结构相似性的并联机构拓扑与尺寸同步设计方法,该方法拓扑优化时以相同质量保留此条件下尺寸参数小范围变化对拓扑结构微弱影响为切入点,通过拓扑结构参数化缩放和刚度-质量元模型构建,形成并联机构尺寸-拓扑同步高效设计流程。以典型■RS并联机构为例开展算例验证与对比分析,结果表明,相同质量条件下,所提设计方法比尺寸设计方法得到的各向刚度更高,即拓扑优化使RS连杆的材料分布更加合理。

基于改进蚁群优化算法的船舶管路布局设计

为了实现在多种约束和目标限制下,能以较短时间为工程师提供多种优质船舶布管方案,提出一种基于改进蚁群优化算法的新型船舶管路布局设计方法。该方法基于网格空间分解模型,将适应度函数中的优化目标进行规范化,对蚁群优化算法的关键步骤,如:蚂蚁行进方向选择、信息素更新机制、蚂蚁寻路过程等进行改进,采用最优解集合保存适应度相同但管路布局效果不同的多个优解,引入辅助点策略和并行计算机制提升算法整体寻优能力和效率。通过仿真算例验证了算法的有效性和先进性。