Mathematical models for analysis and synthesis of spatial mechanisms—IV Seven-link spatial mechanismsMathematische modelle zur analyse und synthese von räumlichen mechanismen. Teil 4: Räumliche mechanismen mit sieben gelenken

In this paper the decomposition method for kinematic synthesis and analysis is extended to 7-link spatial mechanisms. By the way of examples mathematical models for the general 7R mechanism, and RRRPRRR, RRRRPPRR, RRPRPPR 7-link spatial mechanisms are developed whichi are representative of the 42 types of single-loop 7-link spatial mechanisms.     

基于自适应遗传算法的三轴光电跟踪策略

三轴光电跟踪系统由于存在一个冗余横倾轴,可以解决传统两轴光电跟踪系统存在的空间跟踪盲区,全方位跟踪空间目标。在详细分析三轴光电跟踪系统运动学特性的前提下,运用四元数方法建立了存在一个冗余自由度的运动学模型,并设计出一种新的基于自适应遗传算法的三轴跟踪策略。仿真及实验结果表明,基于自适应遗传算法的三轴跟踪策略不需要进行轴系间的运动切换即可避免跟踪盲区,真正实现了系统的三轴联动全方位连续跟踪运动;而且与现有两轴跟踪策略和三轴切换跟踪策略相比,各轴所需的转动角度减小了30%以上,因而提升了系统的跟踪性能,其跟踪快速性提高了30%以上。     

Mathematical models for analysis and synthesis of spatial mechanisms—II: Five-link spatial mechanismsMathematische modelle zur analyse und synthese von räumlichen mechanismen. Teil 2: Räumliche 5gliedrige mechanismen

In this paper the decomposition method for kinematic synthesis and analysis is extended to all 5-link, single-loop spatial mechanisms. This is accomplished by solving sets of equations which can be used to describe the mathematical models of all spatial 5-link mechanisms. These sets of equations can be sub-divided into sets of three equations describing the intersection of two planes and a sphere (computer program PREB0), and into sets of pairs of equations describing the intersection of a plane and a sphere (computer program PREB1). By way of examples the mathematic models for RRRSR, RSRRR, RRTTR, RRPSP and RTPPC spatial mechanisms are described, and an RRRSR mechanism used in sewing machines is analyzed.     

Mathematical models for analysis and synthesis of spatial mechanisms—III Six-link spatial mechanismsMathematische modelle zur analyse und synthese von räumlichen mechanismen. Teil 3: räumliche mechanismen mit sechs gelenken

In this paper the decomposition method for kinematic synthesis and analysis is extended to all 6-link, single-loop spatial mechanisms. This is accomplished by solving sets of equations which can be used to describe mathematical models of all 6-link spatial mechanisms. These sets of equations are solved sequentially in an organised way by subdividing the sets of equations into groups of equations which describe the intersection of two planes with a unit radius sphere (computer programme PREB3), and the intersection of a plane and a unit radius sphere (computer programme PREB2). By way of examples mathematical models for RRRTRR, RRPRTR, RTRPRP, RRPPRC spatial mechanisms are described which are representative of the 130 distinct 6-link spatial mechanisms.     

空间曲面线切割多轴联动加工系统开发及应用

开发了能实现空间曲面零件电火花线切割加工的多轴联动加工系统,分析了系统的组成和运动参数。依据空间解析几何直纹曲面形成原理,建立了五轴联动加工的数学模型体系,获得了五轴联动加工三导线曲面零件的数学模型。研制了多轴联动加工系统的执行机构转摆摆数控工作台及数控系统,加工出理想的实验样件。解决了空间曲面零件的加工难题,拓宽了高速走丝电火花线切割加工的应用范围。该方法在模具制造及空间曲面零件加工中得到广泛应用。     

Velocity fluctuation in spatial slider crank mechanisms

Velocity fluctuations have been recognized as important in the statics and dynamics of mechanisms [1]. The geometric conditions governing the existence of extreme velocity ratios in a spatial 4-link mechanism having two revolute, one cylindrical and one prismatic pair have been obtained. The present investigation presents an algebriac solution of the velocity fluctuation problem. It is shown that, in the general case, the extreme velocity ratios must be among the real roots of an 8th degree polynomial in gemometric parameters of the mechanism. The extreme velocity ratios of any given mechanism can be obtained from the above results. Numerical example is presented to illustrate the procedure.The results presented in this paper can be extended to synthesize a spatial four link mechanism with prescribed extreme velocity ratios.     

Displacement analysis of the generalised RSSR mechanism

The generalised 4-link RSSR mechanism is analysed which is kinematically equivalent to the more general 7-link spatial $\text{R}$

$\text{R}$ mechanism.

and

joint arrangements represent, respectively, two and three co-intersecting revolute pairs.     

The complete shaking force balancing of a spatial linkageПoлнoe ypaвнoвeшивaниe peзyльтиpyюшeй cил инepции пpocтpaнcтвeнныx мexaнизмoв нин-xин-чэнь

The equations for complete shaking force balancing of an open-loop spatial chain consisting of pairs without sliding freedom, a single loop spatial n-bar linkage with R-R link consisting of pairs without sliding freedom, as well as a single loop spatial n-bar linkage with only one P pair are derived in this paper. For a single loop n-bar linkage with R-S link, the equations of complete shaking force balancing are derived also, if the mass center of the R-S link has some constraint. In the examples, the equations of complete shaking force balancing of Bennett, RRRSR, RRPSR and RRSRR linkages are given.     

Multiobjective optimization of a steering linkage

In this paper, multi-objective optimization of a rack-and-pinion steering linkage is proposed. This steering linkage is a common mechanism used in small cars with three advantages as it is simple to construct, economical to manufacture, and compact and easy to operate. In the previous works, many researchers tried to minimize a steering error but minimization of a turning radius is somewhat ignored. As a result, a multi-objective optimization problem is assigned to simultaneously minimize a steering error and a turning radius. The design variables are linkage dimensions. The design problem is solved by the hybrid of multi-objective population-based incremental learning and differential evolution with various constraint handling schemes. The new design strategy leads to effective design of rack-and-pinion steering linkages satisfying both steering error and turning radius criteria.

     

(2PSR+PUU)&RP混联机床的位置及其工作空间分析

针对并联机床摆角小,难以加工复杂曲面零件的缺点,提出一种新型(2PSR+PUU)&RP混联机床的机构构型。首先运用螺旋理论以及修正的K-G公式对机构自由度进行分析计算与验证。运用闭环矢量法对机构进行运动学分析,给出该机构的位置逆解以及基于粒子群算法的正解,确定驱动块和动平台的位姿关系。在SolidWorks软件中采用动静结合法绘制出其工作空间,并利用ADAMS对其摆角进行测算,验证了机构模型的正确性以及机构运动的可实现性。研究表明,混联机床具有3T2R这5个自由度,有较大的工作空间,且其刀具摆角可达(0°～90°),通过刀具的大摆角转动和五轴联动可应用于部分汽轮机,水轮机和航空发动机的叶片和复杂曲面零件的加工。     

钳夹车并联起升机构分析与电液称重实验研究

为解决长大货物铁路运输钳夹车自身精确称重问题,基于空间闭环机构自由度计算公式,对钳夹车并联起升机构进行了机构自由度分析,基于坐标变换法对钳夹车并联起升机构进行了运动学分析,建立了货物起升位置与压柱油缸输入映射模型,得到了起升机构速度传递雅可比矩阵,结合系统静力平衡方程,建立了压柱油缸起升力与货物质量间力映射模型。分别针对钳形梁结构变形和压柱油缸摩擦对并联起升机构称重精度的影响进行了分析计算,在此基础上,设计并研制了钳夹车并联起升机构样机及其电液称重实验系统,开展了基于摩擦补偿的钳夹车电液称重实验研究,提高了钳夹车电液称重精度。     

缝纫机弯针空间复合运动的空间机构创新设计

双重环缝缝纫机以双自由度多杆空间机构实现弯针空间复合进给运动,由于包含有多个球面副带来了制造工艺复杂及磨损大等问题。通过分析弯针空间复合进给工艺动作的运动特征,提出了两种基于空间RCCC机构弯针空间复合进给运动新方案,把双自由度的弯针空间复合进给运动转化为不含球面副的空间RCCC机构的近似函数综合问题,采用空间机构自适应综合方法进行求解,得到了空间RCCC机构的尺度,能够在狭小空间内实现双重环缝缝纫机弯针空间复合进给运动要求。     

VELOCITY ANALYSIS OF A SPATIALM ECHANISM USING THE PRINCIPLEOF VIRTUAL FORCES

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模切机肘杆机构连杆的有限元分析

针对MP1040B型模切机肘杆机构中的连杆在使用中破损故障时有发生,在运动学和动力学分析的基础上,利用有限元方法进行了强度分析,结果表明,当在正常模切力2 450 kN时连杆的强度满足要求,当在极限模切力3 136 kN时连杆的强度不满足要求,分析结果为结构的改进或材料的选择提供了依据.     

An approach to the displacement analysis of spatial mechanisms—I : Principles and mechanisms with low degree equations

The use of direction cosines and projections is shown to be adequate and efficient for deriving the input-output displacement equations for spatial mechanisms, up to 6-link 5R-C mechanisms. The displacement equations are derived for several 5-link mechanisms and 6-link 4R-P-C mechanisms. These derivations are quick and direct and automatically avoid extraneous roots. The method of derivation for 6-link 5R-C mechanisms is indicated, showing how extraneous roots are avoided by the approach. Part I explains the method, applied to 5-link mechanisms that yield a 4th degree equation. Part II shows the application to 5- and 6-link mechanisms with equations of higher degree.     

Synthesis of spatial automatic operators with the aid of Electronic Digital ComputersCинтec пp;ocтpaнcтвeннoгo aвтooпepaтopa пpи пoмoщи эцвм

This paper deals with the synthesis of a spatial 4-link mechanism with two kinematic revolute pairs, a spherical pair and a spherical pair with a latch, using the Rosenbrock method of optimization.Several variants are considered according to various rhythms of the tracing of a point on the coupler along the traced curve. The digital data obtained during the synthesis of the mechanism was displayed on the “Mir-2” Electronic Digital Computer.     

Multiple-motion mode switching robot platform

Developing an intelligent robot platform that has multiple motion modes and can actively adjust the motion mode according to an operation situation is necessary in resolving the inability of single-mode robots to adapt completely to complex environments. In this study, we designed a robot that has multiple motion modes and can switch freely in these existing modes. The robot has the following modes: Four-legged walking, two-legged walking, pulse scrolling, and crawler movement. In the robot’s design, these modes are not just simple mechanisms involving superposition and motion switching. These modes involve a degree of freedom in reuse, thereby reducing the number of drives and obtaining a compact structure while achieving a coherent transition of each action mode. For higher load ratios, motion continuity are increased. The robot platform can balance itself during movement by adjusting its own mechanism or providing additional force and change its shape and posture over some obstacles by adjusting its own mechanism.

     

A new method to study the degree of freedom of spatial parallel mechanisms

The traditional formulae for degree of freedom are not valid in solving the platform for certain complex spatial parallel mechanisms. Therefore, by uniformly depicting the kinematic and geometric constraints of a mechanism with a screw theory, we put forward a new method to study the degree of freedom for the platform of spatial parallel mechanisms. This method should solve the analysis and calculation problems of the degree of freedom in many complex spatial parallel mechanisms, which may not always be solved correctly with traditional formulae.     

用一个示力副法作单闭合空间机构的受力分析

与传统的分析法不同,本文对单闭合空间机构的受力分析采用了先求出一个运动副中约束反力的方法。这个示力副中的约束反力在无过约束的空间机构中是静定的,文中详细讨论了用矩阵法确定的过程并举四杆RCCC及五杆RRSRR机构为例进行分析。对RCCC机构还进一步讨论了其他运动副中约束反力和原动件上平衡力的确定。本文所提示力副法可推广于作任意复杂空间机构的受力分析。     

Design and analysis of a novel parallel mechanism for prosthetic knee wear test simulators

Using a parallel mechanism in the wear test simulators of prosthetic knees provides an easy access to the femoral and tibial components during tests. Moreover, because of its higher accuracy and load capacity, in comparison with serial mechanisms, it allows simulation of heavier tasks, such as climbing stairs, to be performed. This paper describes a new 3 Degree of freedom (DoF) spatial 2T1R (T: Translational DoF; R: Rotational DoF) parallel mechanism, for reproducing the force and motion of the tibial component of the knee prostheses in a wear test simulator. Kinematics and dynamics analysis of the mechanism indicated that it can satisfy the required DoFs, workspace and load capacity prescribed in the standard. Also, evaluation of the performance of the mechanism using the simMechanics toolbox of MATLAB revealed that it can reproduce the prescribed forces/torques with relatively high accuracy. However, the mechanism’s force outcomes were found to be affected by inaccuracies in mounting the prosthesis components, although less than the previous serial simulators. In comparison of the different possible architectures, a lateral leg angulation of 45 degrees provided the best efficacy, considering the size of actuators, the overall size of the mechanism and the accessibility of the test sample.