外文翻译设计并联机床使用kinetostatic标准的表现机械制造数控机床_机械制造-数控机床.pdf
1/36 THE DESIGN OF PARALLEL KINEMATIC MACHINE TOOLS USING KINETOSTATIC PERFORMANCE CRITERIA 1.INTRODUCTION Most industrial machine tools have a serial kinematic architecture,which means that each axis has to carry the following one,including its actuators and joints.High Speed Machining highlights some drawbacks of such architectures:heavy moving parts require from the machine structure high stiffness to limit bending problems that lower the machine accuracy,and limit the dynamic performances of the feed axes.That is why PKMs attract more and more researchers and companies,because they are claimed to offer several advantages over their serial counterparts,like high structural rigidity and high dynamic capacities.Indeed,the parallel kinematic arrangement of the links provides higher stiffness and lower moving masses that reduce inertia effects.Thus,PKMs have better dynamic performances.However,the design of a 2/36 parallel kinematic machine tool(PKMT)is a hard task that requires further research studies before wide industrial use can be expected.Many criteria need to be taken into account in the design of a PKMT.We pay special attention to the description of kinetostatic criteria that rely on the conditioning of the Jacobian matrix of the mechanism.The organisation of this paper is as follows:next section introduces general remarks about PKMs,then is explained why PKMs can be interesting alternative machine tool designs.Then are presented existing PKMTs.An application to the design of a small-scale machine tool prototype developed at IRCCyN is presented at the end of this paper.2.ABOUT PARALLEL KINEMATIC MACHINES 2.1.General Remarks The first industrial application of PKMs was the Gough platform(Figure 1),行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为3/36 designed in 1957 to test tyres1.PKMs have then been used for many years in flight simulators and robotic applications2 because of their low moving mass and high dynamic performances.Since the development of high speed machining,PKMTs have become interesting alternative machine tool designs3,4.Figure 1.The Gough platform In a PKM,the tool is connected to the base through several kinematic chains or legs that are mounted in parallel.The legs are generally made of either telescopic struts with fixed node points(Figure 2a),or fixed length struts with gliding node points(Figure 2b).Along with high-speed cuttings unceasing development,the 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为4/36 traditional tandem type organization constructs the platform the structure rigidity and the traveling carriage high speed becomes the technological development gradually the bottleneck,but the parallel platform then becomes the best candidate object,but was opposite in the tandem engine bed,the parallel working platform had the following characteristic and the merit:(1)structure is simple,the price is low The engine bed mechanical spare part number is series connected constructs the platform to reduce largely,mainly by the ball bearing guide screw,the Hooke articulation,the ball articulation,the servo electrical machinery and so on common module is composed,these common modules may by the special factory production,thus this engine beds manufacture and the inventory cost are much lower than the same functions traditional engine bed,easy to assemble and the transporting.(2)structure rigidity is high Because used closeness structure(closed-loop structure)to enable it to have high rigid and the high speed merit,its structural load streamline was short,but shouldered decomposes pulls,the pressure also to withstand by six connecting rods,by materials mechanics viewpoint,when the external force was certain,the bracket quantitys stress and the distortion were biggest,the both sides inserted the(build-in)next best,came is again both sides Jan supports(simply-supported),next 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为5/36 was the bearing two strength structure,what the stress and the distortion were smallest was the tensity two strength structure,therefore it had the high rigidity.Its rigidity load ratio is higher than traditional the numerically-controlled machine tool.(3)processing speed is high,the inertia is low If the structure withstands the strength will change the direction,(will be situated between tensity and pressure),two strength components will be most save the material the structure,but it will move to the moving parts weight to reduce to lowly and simultaneously will actuate by six actuating units,therefore machine very easy high speed,and will have the low inertia.(4)working accuracy is high Because it for the multiple spindle parallel organization composition,six expandable pole poles long alone has an effect to cutting tools position and the posture,thus does not have the traditional engine bed(i.e.connects engine bed)the geometrical error accumulation and the enlargement phenomenon,even also has the being uniform effect(averaging effect);It has the hot symmetrical structural design,therefore the thermal deformation is small;Therefore it has the high accuracy merit.(5)multi-purpose flexible Is convenient as a result of this engine bed organization simple control,easily according to processing object,but designs it the special purpose machine,simultaneously 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为6/36 may also develop the general engine bed,with realizes the milling,boring,processings and so on grinding,but may also provide the essential measuring tool to compose it the measuring engine,realizes engine beds multi-purpose.This will bring the very big application and the market prospect,has the very broad application prospect in the national defense and the civil aspect.(6)service life is long Because the stress structure is reasonable,the moving part attrition is small,and does not have the guide rail,does not have the iron filings either the refrigerant enters the guide rail interior to cause it to scratch,the attrition or the corrosion phenomenon.(7)Stewart platform suits in the modular production Regarding the different machine scope,only need change the connecting rod length and the contact position,maintains also easily,does not need to carry on parts remaking and to adjust,only need the new organization parameter input.(8)transformation coordinate system is convenient Because does not have the entity coordinate system,the engine bed coordinate system and the work piece coordinate system transform depend on the software to complete completely,is convenient.When the Stewart platform applies in the engine bed and the robot,may reduce the static error(,because high rigidity),as well as 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为7/36 dynamic error(because low inertia).But Stewart the platform inferiority lies in its working space to be small,and it has the singular point limit in the working space,but the serial operation platform,the controller meets time the singular point,accountant will figure out the actuation order which the drive is unable to achieve to create the ning error,but the Stewart platform will lose the support partial directions in the strange position the strength or moment of force ability,will be unable to complete the constant load object.Figure 2a.A bipod PKM Figure 2b.A biglide PKM 2.2.Singularities 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为8/36 The singular configurations(also called singularities)of a PKM may appear inside the workspace or at its boundaries.There are two types of singularities5.A configuration where a finite tool velocity requires infinite joint rates is called a serial singularity.A configuration where the tool cannot resist any effort and in turn,becomes uncontrollable,is called a parallel singularity.Parallel singularities are particularly undesirable because they induce the following problems:-a high increase in forces in joints and links,that may damage the structure,-a decrease of the mechanism stiffness that can lead to uncontrolled motions of the tool though actuated joints are locked.Figures 3a and 3b show the singularities for the biglide mechanism of Fig.2b.In Fig.3a,we have a serial singularity.The velocity amplification factor along the vertical direction is null and the force amplification factor is infinite.Figure 3b shows a parallel singularity.The velocity amplification 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为9/36 factor is infinite along the vertical direction and the force amplification factor is close to zero.Note that a high velocity amplification factor is not necessarily desirable because the actuator encoder resolution is amplified and thus the accuracy is lower.Figure 3a.A serial singularity Figure 3b.A parallel singularity 2.3.Working and Assembly Modes A serial(resp.parallel)singularity is associated with a change of working mode6(resp.of assembly mode).For example,the biglide has four possible working modes for 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为10/36 a given tool position(each leg node point can be to the left or to the right of the intermediate position corresponding to the serial singularity,Fig.4a)and two assembly modes for a given actuator joint input(the tool is above or below the horizontal line corresponding to the parallel singularity,Fig.4b).The choice of the assembly mode and of the working mode may influence significantly the behaviour of the mechanism5.Figure 4a.The four working modes Figure 4b.The two assembly modes 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为11/36 3.PKMs AS ALTERNATIVE MACHINE TOOL DESIGNS 3.1.Limitations of Serial Machine Tools Today,newly designed machine tools benefit from technological improvements of components such as spindles,linear actuators,bearings.Most machine tools are based on a serial architecture(Figure 5),whose advantage is that input/output relations are simple.Nevertheless,heavy masses to be carried and moved by each axis limit the dynamic performances,like feed rates or accelerations.That is why machine tools manufacturers have started being interested into PKMs since 1990.3.2.PKMs Potentialities for Machine Tool Design The low moving mass of PKMs and their good stiffness allow high feed rates(up to 100 m/min)and accelerations(from 1 to 5g),which are the performances required by High Speed Machining.行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为12/36 PKMs are said to be very accurate,which is not true in every case4,but another advantage is that the struts only work in traction or compression.However,there are many structural differences between serial and parallel machine tools,which makes it hard to strictly compare their performances.3.3.Problems with PKMs a)The workspace of a PKM has not a simple geometric shape,and its functional volume is reduced,compared to the space occupied by the machine7,as we can see on Fig.5 Figure 5.Workspace sections of Tricept 805 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为13/36 b)For a serial mechanism,the velocity and force transmission ratios are constant in the workspace.For a parallel mechanism,in contrast,these ratios may vary significantly in the workspace because the displacement of the tool is not linearly related to the displacement of the actuators.In some parts of the workspace,the maximal velocities and forces measured at the tool may differ significantly from the maximal velocities and forces that the actuators can produce.This is particularly true in the vicinity of THE DESIGN OF PKMT USING KINETOSTATIC PERFORMANCE CRITERIA 5 singularities.At a singularity,the velocity,accuracy and force ratios reach extreme values.c)Calibration of PKMs is quite complicated because of kinematic models complexity8.4.EXISTING PKMT DESIGNS 行机构和联接点高速加工突出了一些弊端例如架构较重的运动部件需要从机械结构高刚度以限制弯曲问题即降低机床精度并限制动态表现的曲线这就是为什么并联机床吸引了越来越多的研究人员和公司因为它们据称提供了单独的优机床有更好的动态性能然而计一个并联机床是一个艰巨的任务在进一步的研究之前广泛地在工业用途中的调研是必不可少的许多标准要考虑到在计一个并联机床我们要特别注意描述并联机床标准依赖于现有的雅可比矩阵的机制该组的应用了一次小规模的机床样机研制关于并联机床总论第一次工业应用并联机床是平台图设计于年以测试并联机床当时已使用多年在飞行模拟器和机器人因为他们的低移动质量和高动态表演由于发展的高速切削加工并联机床已成为14/36 In this section will be presented some existing PKMTs.4.1.Fully Parallel Machine Tools What we call fully parallel machine tools are PKMs that have as many degrees of freedom as s
