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动态优化的一种新型高速,高精度的三自由度机械手①
彭兰(兰朋)②,鲁南立,孙立宁,丁倾永
(机械电子工程学院,哈尔滨理工学院,哈尔滨 150001,中国)
( Robotics Institute。Harbin Institute of Technology,Harbin 150001,P。R。China)
摘要
介绍了一种动态优化三自由度高速、高精度相结合,直接驱动臂平面并联机构和线性驱动器,它可以提高其刚度进行了动力学分析软件ADAMS仿真模拟环境中,进行仿真模拟实验.设计调查是由参数分析工具完成处理的,分析了设计变量的近似的敏感性,包括影响参数的每道光束截面和相对位置的线性驱动器上的性能.在适当的方式下,模型可以获得一个轻量级动态优化和小变形的参数。一个平面并联机构不同截面是用来改进机械手的.结果发生明显的改进后的系统动力学仿真分析和另一个未精制一个几乎是几乎相等.但刚度的改进的质量大大降低,说明这种方法更为有效的。
关键词: 机械手、ADAMS、优化、动力学仿真
0 简介
并联结构机械手(PKM)是一个很有前途的机器操作和装配的电子装置,因为他们有一些明显的优势,例如:串行机械手的高负荷承载能力,良好的动态性能和精确定位的优点等. 一种新型复合3一DOF臂的优点和串行机械手,也是并联机构为研究对象,三自由度并联机器人是少自由度并联机器人的重要类型。三自由度并联机器人由于结构简单,控制相对容易,价格便宜等优点,具有很好的应用前景。但由于它们比六自由度并联机器人更复杂的运动特性,增加了这类机构型综合的难度,因此对三自由度并联机器人进行型综合具有理论意义和实际价值。本文利用螺旋理论对三自由度并联机器人进行型综合,以总结某些规律,进一步丰富型综合理论,并为新机型的选型提供理论依据,以下对其进行阐述。
如图-1所示 机械手组成的平面并联机构(PPM)包括平行四边形结构和线性驱动器安装在PPM.两直接驱动电机c整合交流电高分辨率编码器的一部分作为驱动平面并联机械装置.线型致动器驱动的声音线圈发动机.这被认为是理想的驱动短行程的一部分.作为一个非换直接驱动类,音圈电机可以提供高位置敏感和完美的力量与中风的角色,高精密线性编码作为回馈部分保证在垂直方向可重复性。
另一方面,该产品具有较高的刚度比串行机械手,因为它的特点和低封闭环惯性转矩。同时,该系统可以克服了柔性耦合力学弹性、齿轮、轴承、被撕咬支持,连接轴和其他零件,包括古典驱动设备,因此该机械手是更容易得到动力学性能好、精度高。
图-1 3自由度的混合结构的机械手
当长度的各个环节的平面并联机时,构决定于运动学分析和综合[4-7],机械优化设计的首要任务,应加大僵硬、降低质量.关于几个参数模型.这是它重要和必要的影响,研究了各参数对模型表现以进一步优化。本文就开展设计研究工具,通过参数分析亚当斯,又要适当的方式来获得一个轻量级的优化和小变形系统。
1 仿真模型
ADAMS(Automatic Dynamic Analysis 0f Mechanical System)自动机械系统动力学分析是一个完美的软件,对机械系统动力学模拟可处理机制包括有刚性和灵活的部分,仿真模型可以创造出机械手的亚当斯环境 如图-2。OXYz是全球性的参考帧,并OXYz局部坐标系,两个直流驱动电机、交流和02M O1A表示,与线性驱动器CH被视为刚性转子转动惯量电机传动的120kg/cm2。大众的线性驱动器是1.5kg,连接AB、德、03F和LJ被视为柔性体立柱、横梁GK,通用公司和公里,形成一个三角形,也被当作柔性传动长度的链接是决定提前运动学设计为AB =O3F = 7cm,DE=IJ=7cm,GK= 7cm,GM =11.66cm, = 8.338cm。其它维度,这个数字是01A = 02M =7cm,CB=CD=HJ 2.5cm。EF=EG=JK= 3cm。
虽然总平面并联机构的运动都是在水平、垂直和水平刚度必须在竖向刚度特征通常低于水平僵硬,因为它的角色在垂直悬臂梁的截面尺寸计算每一束平面并联机构和相对位置的线性驱动器是两个非常僵硬的影响因素的系统。
运动支链可分为三类:"主动链(由驱动器赋予确定独立运动的支链。一般是单驱动器控制一个自由度的运动),从动链(不带驱动器、被迫作确定运动的支链。又分为以下两种:约束链:独立限制机构自由度的从动链。冗余链:重复限制机构自由度的从动链)复合链(有单驱动器、但限制一个以上的机构自由度的支链,实际是主动链与约束链的组合)-并联机构是由这几种支链用不同形式组合起来的。动链中的约束链除了可以提高机构刚度和作为测量链外,其更主要的作用是用来约束动平台的某一个或几个自由度,以使其实现预期的运动。
图-2 仿真模型
2 仿真模拟结果
在本节中,平均位移的末端是用来描述动态刚度,这是在不同的配置在不同的线性驱动器向前,从最初的位置的目的地,一般的竖向位移的机械手是作为目标来研究竖向刚度,平均差别的横坐标、纵坐标点之间有一个刚性数学模型,模型,作为目标来研究水平刚度。
并联机器人的构型设计即型综合是并联机器人设计的首要环节,其目的是在给定所需自由度和运动要求条件下,寻求并联机构杆副配置、驱动方式和总体布局等的各种可能组合。国内的许多学者正致力于这方面的研究,其中比较有代表性的有如下几种方法:"黄真为代表的约束综合法;杨廷力等人的结构综合法;代表的李代数综合法。以上各种方法自成体系,各有特点,都缺乏理论的完备性。本文提出添加约束法,是从限制自由度的角度出发,增加约束,去除不需要的自由度,因每条主动链只有一个驱动装置,让其控制一个自由度,其余自由度通过纯约束链去除,这样可以使主、从动运动链的作用分离,运动解耦,有利于控制。具有三自由度的并联机床,当采用条主动支链作为驱动时,机构就需要约束另三个自由度,通过选择无驱动装置的从动链来完成,则整个机构成为有确定运动的三自由度的并联机构。黄真等提出的约束综合法对完全对称的少自由度并联机器人机构进行了型综合,完全对称的支链结构相同,都属于复合链,每条支链除都有一个单驱动器,控制一个自由度外,还应约束一个以上自由度才能使机构的六个自由度全部受控,使机构有确定的运动。
2.1 截面效应
扭转变形位移的连结将会引起的,所以,扭转常数的横截面,重力是研究装系统来研究,采取扭转刚度的垂直切片lxx不变的各个环节和梁作为设计变量的变化,从 0.1 x 105mm4 与 3.5 x 105 mm4。
图-3 不断的效果在垂直变形扭转
图-3显示了平均位移与截面扭转常数末端的各个环节和梁,根据它的变化速率的环节,是最大的,AB是链接,LJ依次分别GK梁和KM有在竖向刚度性能。其他的仿真结果表明,水平位移之间的差异进行比较,结果表明该模型体育智力H和刚性模型变化小就改变了恒定不变的时候扭加载惯性力的线性驱动器,但是水平位移的变化,这意味着在这种模拟竖向变形的生产水平位移系统机械手。注意端面线性驱动器的主要原因是水平变形、线性驱动器机器人是由两个节点C和H . 所以,我们计算了不同的Z-coordinate摄氏度之间,如图所示,在图4 -扭转常数的影响差别的链接德。其次是最有效的通用和连接梁,连接O3F,梁GK有效果。
因此,应采取AB和连接区段大扭常数的免疫力,竖向刚度较大并行扭转不变的链接德也使较少的均匀性,降低线性驱动器不可以降低水平变形。
图-4 在不影响扭不变
如图-5、6所展示的影响是区域惯性转矩的设计变量是区域刚度和惯性转矩的各个环节和梁lz,图显示增加lw卡尔减少的速度高于垂直位移的不断增加Ixx扭转。这个Yxx AB、梁的链接,链接O3F是Iyy三个主要因素决定了竖向刚度。
图-6 所示 链接的AB、梁公里,连接03F也是其中的三个主要因素决定的均匀性线性传动装置、不同的分析结果表明,Izz效果好,具有至少两个垂直和水平刚度,这意味着这种结构,具有足够的水平,降低Izz刚度的链接和增加Iyy AB、梁的链接,链接O3F公里的好方法,优化系统。
图-5 瞬间的惯性效应对垂直位移
图-6 转动惯量不平衡的影响
2.2影响的线性驱动器的相对位置
线性执行器的惯性是主要载荷之一,在机械手的运动,不同的相对应的垂直位置产生不同的变形,图7显示了绝对平均的最终效应垂直位移时驱动马达以恒定的加速度旋转,我们可以看到,过低或过高的相对位置会造成比格变形,最好的位置是一对Z = 24毫米的地方大概是从中间环节连接O3F到 AB.
图-7 影响线性驱动器的相对位置
3 分析改进的机械手
根据上述模拟结果,所有改进的机械手的设计,时间如下:链接截面AB,DE,lJ 与30mm的基础和高度,10毫米的厚度;链接O3F和矩形空心梁与30mm的基础和高度工型钢,l0mm法兰和6mm网;梁竞,通用汽车与8mm的坚实基础和30mm高的矩形。
图-8 梯形运动姿态
图-9中回应的是机械手,相比之下,图-10中提高初始的反应,在其中所有的链接和机械手的矩形截面梁的坚实基础,用30毫米,高度的差异是曲线,C和H的曲线积分,二是垂直位移的末端,改进系统中最大位移0.7Um最初的0.12Um相比,争论的振动激励后仍停留在O.06Um±0.15% s±O.05Um相比的初始变形改善系统的初始小于前者具有较少的惯性,因为在相同的步伐不断加快,保持振动瓣膜差不多一样,它对这整个系统中来说,仍然改善系统的刚度,几乎相当于初始制度,针对大规模的平面并联机构在该系统相比下降了30%,这样的初始优化是有效的。
图-9 、 图-10 动态响应
4 结论
本文设计了一种新型三自由度机械手变量的敏感性进行了研究在ADAMS环境中,可以得出以下结论:
1) 机器人具有较大的水平刚度,最终水平位移,效应主要是由机械手垂直变形造成的,因此,更重要的是增加的幅度比刚度竖向刚度。
2) 参数Ixx,Iyy并链接'截面刚度Izz有不同的效应,Iyy已经对垂直刚度的影响最大,Ixx在第二位的是,Ixx具有在垂直刚度的影响最小,他们都较少对水平比垂直刚度刚度。
3) 横截面的不同环节都有不同的影响,连线竖向刚度AB和德应该使用区扭转常数和惯性力矩大,如变形、长方形、横梁KM,,线 03F应该使用区段形梁等重大时刻转动惯量、横梁GK,和GM 可以使用尽可能的一小部分,从而降低了质量。
4) 最佳的线性驱动器的相对位置可以减少变形,最好的位置是垂直的平行结构。
5) 改进的机械手的动态分析表明该优化设计方法研究的基础上的效率。
参考文献
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HIGH TECHNOLOGY LEITERS IVol. 12 No. 1 1 Jan. 2α)6 63
Dynamics optimization of a novel high speed and high precision 3-DOF manipulator①
Lan Peng (兰 朋闷,U Nianli , Sun Lining 铃 ,Ding Qingyong 费
( School of Me.chatroni 臼 Engineering, Har也m Institute of Te<丁hnology, Harbin 15α刷 ,P . R .China) ( • Robotics Institute, H缸bin Institute of Technolo町,Harbin 15仅见I , P.R.China)
Absti古董ct
After introducing a novel 3-DOF high speed and high precision manipulator which combines direct driven planar parallel mechanism and linear actuator, ways of increasing its stiffness a陀 studied through dynamics simulation in ADAMS softw缸它 environment . Design study is carried out by parametric analysis tools to analyze the approximate sensitivity of the design V缸iables , including the effects of p缸沮netens of each beam cross section and relative position of linear actuator on model performance. Conclusions a陀 drdwn on the appropriate way of dynamics optimization to get a lightweight and small deformation manipu lator. A planar parallel mechanism wi出 different cross section is used to an improved manipulator. Re
suits of dynamics simulation of the improved system and another unrefined one 缸e compa配d . η1e sti旺-
ness of them is almost equal , but the mass of 由e improved one decreas臼 greatly , which illustrates the ways efficient .
Key words: manipulator, ADAMS, optimization , dynamics simulation
0 Introduction
Parallel kinematic manipulatons ( PKM ) 耐 a class of promising machine for the manipulation and assemble of electronic device, because they have some advantages
over the serial manipulator, such as high load ca町ing capacity , g0<对 dynamic performance and precise position ing[1l . A novel hybrid 3-DOF manipulator, which com
bines the advantages of parallel manipulator and serial manipulator, is studied in this paper. As shown in Fig. 1, the manipulator is composed of planar parallel
mechanism ( PPM ) including parallelogram structure and linear actuator mounted on the end of PPM . Two A巳 di
陀ct driven moto囚 integrated high 陀田lution em
selected as driven part of planar par苟Ilel mechanism . Lln 回 actuator is driven by voice coil motor, which is con sidered as ideal driven part for short travel . As a kind of non-commutated di陀ct 世ive , hysteresis-free, cog-free
device, voice coil motor can provide both high 归sition sensitivity 阻d pert<叩force vensus stroke character. Hi班
precision linear encoder is used as feedback parts to 伊ar ante悟 出e 陀阴暗tability in vertic况Idirection .
Compared with higher degree of freedom parallel ma
nipulator, for example Steward platform or Tricept robot , kinematic and d严1amic m叫els of PPM ar吃 simple[ i-3] _
On the other hand , it has higher stiffness 由m 出e serial manipulator because of its close loop feature and low mo ment of inertia . Meanwhile, the system can ove陀ome the mechanical elasticity introduced by flexible coupling, gear teeth, be白吨,bearing support , connecting shaft and other parts included by classical drive system . So this ma nipulator is more easily to get well dynamics perfonnance and high p即ision .
Planar parallel mechanism
Motor
Fig.1 3-00F hyhrid structUJ它 manipulator
When the length of each link of pl四ar parallel mechanism is d配ided by kinematics analysis and syn出e sis[4-7l , the primary task of optimal desi伊 should be in creasing the stiffness and dee陀asing 由e mass. With re gard to model wi由several par泪neters, it is important and
咀1at makes real time control possible and is mo陀 precise .
neees
ry to study the influence of each p
neter on
田 缸田
① Supported by 配 High Technology Research and Development Pr咱出nme of China ( No. 2003AA刷刷)) .
② To whom coπ呵lOndence 动 uld be addressed . E而 mail: l皿 p@ sma. 凹阳
Ri,cpjved on Sept. 29,刻Xl4
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64 1-DGH TECHNOLO(,Y LF.ITERSI Vol.12 No. I I Jan. 2(胁
model performance in order tu make fu出er optimization . This paper will carry out design study by parametric anal ysis tools of ADAMS, and then p陀sent appropriate ways of optimization to get a lightweight and small deformation system .
1 Simulation model
ADAMS ( Automatic Dynamic Analy附 of Mechanical System) is a perfect software tool for dynamics simulation of mechanical system . It can deal with mechanism con sisting of both rigid and flexible parts . Simulation model of the manipulator can be created in the ADAMS environ ment as shown in Fig.2. OXYZ is the global reference
frame , and o.切:yz is local reference frame. Two AC direct
driven motors, expressed as 01A and Oi M , and linear actuator CH are t陀ated as rigid 以,dy . 币1e rotor inertia of motor is 120kg · cm2 . 币1e mass of linear actuator is 1.5kg. Links AB, DE, 03F and U are tr臼ted a,;; flexible
effector is used to characterize the dynamic stiffness, which is different at different configuration during the lin
ear actuator moving fmward from initial position to the destination . 咀1e average vertical displacement of the end effector is taken as the ob ective to study vertical stiff n白白. The average difference of X-coordinate and Y『coor dinate of point H between 由is model and a rigid model is 时cen as the objective to study level 叫iffness.
2 .1 Effect of er鸭 ”ction
。
Torsion defonnations of links will cause vertical dis placement of the end-effector. So, torsional constants of cross section are studied first . Gravity is loaded on the system to study the vertical stiffness . Take torsional con stant ι f section of each link and beam as design vari able which varies from 0.1 x la5mm4 to 3 .5 x Ia5mm4 . Fig. 3 shows the average displacement of 由e end-effector
body. Beam『 GK , GM and KM , which form a triangle,
即e also treated as flexible body . The length of links a陀 decided in advance by kinematics design a,;; AB =的F """ 7cm, DE = IJ = 7cm , GK = 7cm , GM = 11.66cm, KM =
8.338cm . 响1e other dimensions in the figure a陀 01 A =
02 M = 7cm, CB = CD = HJ ::: 2.5cm , EF = EC = JK =
3cm.
Although the gross motion of planar parallel mecha nism is in level, ho由 the vertical and level stiffness has to be considered . And the vertical stiffness is usually less than the level stiffness because of its cantilever character
in vertical plane. 咀1e cross section size of each beam of
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,。 ’5 2.0 2.5 3.0 3.6
T惆ional cons阳ts (105mm勺
planar parallel mechanism and the relative position of lin ear actuator 缸e two important factors that affect the stiff ness of the system. Therefore, the following study is done in these respects .
Fig.2 Simulation mudd
2 Simulation r四时t
In this section , the average displacement of the end-
Fig. 3 Effect of torsional constant on vertial deformation
versus cross section torsional constant of each link and be却n . According to it , the change rate of link AB is the biggest . Next is link DE ,日in tum res严ctively . B创ms GK and KM have the least eff白t on vertical stiffness. Other simulation shows that level displacement difference
of point H between this model and a rigid model changes little with respect to a change in the torsional constant when constant level inertia force is loaded on the linear actuator. But the level displacement of the end-effector changes in 出is simulation . η1at means vertical deforτna tion of the system should produce level displacement of end回effector. Note that unevenness of the linear actuator is the main cause of level defonnation of end-effect肘,and the linear actuator is supported by two joints C and H. So we calculate the difference of Z -coordinate between 阳int C and H . As shown in Fig. 4, torsional constant of link DE affects the difference 出e most efficiently . Next is k田n GM and link U in order. Link 03F and beam GK have the leai;;t effect .
咀1erefore, links AB and DE should adopt se<;tion
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HIGH TECHNOLC见Y IEITERSI Vol.12 No. l lJan. 2α)6 65
with big torsional constant to enhance the vertical stiff ness. Bigger torsional constant of link DE also caus臼less unevenness of the linear actuator . Decreasing the uneven ness can reduce the level deformation .
2-link AB
stant ι .四e Irr of link AB , beam KM and link 03F are 出e three main factors that decide the vertical stiffness. Fig. 6 shows the Irr of link AB , beam KM and link 03F
缸它 also the three main facto陀 that decide the unevenness of the linear actuator. Di征erent analysis shows that I,, has the least effect on b 由 vertical and level stiffness . 币iat
means this kind of structure has enough level stiffness. So
4一UnmkUGM
d asing I,, of links and increasing ”’ of link AB,
-be晦 配陀
beam KM and link 03F 缸它 the good ways to optimize the system .
2.2 Effect of the relative position of linear ac阳ator
3.7
3.6
QO 0.5 1.0 1.5 2.0 2.5 3.。 3.5
Torsional constants (1l?mm4)
η1e inertia of linear actuator is one of the main loads during the motion of manipulator . Different relative ve民i cal position should produce different deformation . Fig. 7
Fig.4 Effect of torsional constant on unevenness
What Fig声 .5 and 6 show are the effects of area
m
G
(EE一守LD己 言ωERE昏时唱g- 百多
.0.αJ05
shows the absolute average vertical displacement of end effector when the driven motors rotate at a constant accel
eration . We can see that too low or too hi班 时ative posi
tion will cause bigger defonnation .咀1e best position is at a如ut Z = - 24mm where is approximate the midst from link AB to link 03F.
m
E
。
’6
m
A
.0.0025。。
4一link u
6 beam GM
0.5 1.0 1.5
Moments of iner由(llfmm‘}
J
d
O D41
l
AB
亚 刷
E
u
2.0 2.5 ]
Fig.5 Effect of moments of i阳rtia on vertial defo回国lion
。。
0.0
-«J.0
-40.0 .10.0
Z-coordinate (mm)
篇。 eoo
1 」ink 03F 3---link DE 5一悦am GK
2一link:AB
4--link 日
6--bE姐m GM
Fig.7 Effect of relative position of linear actuator
3
--5
"’
ι乙 』 回南.:::.-..乓芫叫
.. ·
、、
3 Analysis of an improved manipulator
According to above simulation result , an improved manipulator is designed as follows : cross s创ions of links
AB , DE ,日在附 hollow rectangle with 30mm b出e and
2.5 0.0 0.5 1.0
1.5
2.0 2.5
height , 10mm thickne制;link 向F and beam KM 町e I
Moments of inertia (105mm‘)
Fig. 6 Effect of moments of inertia on unevenness
moment of inertia on the stiffness. 'lbe design variable is 脏a moment of inertia lyy and ι of each link and beam . Fig. 5 shows that inc陀凶e of Irr can 配duce the vertical deformation more rapidly than increase of torsional con-
beam with 30mm ba
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