research article analytical modeling of a ball screw feed ......guide module can be preloaded at a...

9
Research Article Analytical Modeling of a Ball Screw Feed Drive for Vibration Prediction of Feeding Carriage of a Spindle Lei Zhang, 1,2 Taiyong Wang, 1,2 Songling Tian, 1,2 and Yong Wang 1,3 1 School of Mechanical Engineering, Tianjin University, Tianjin 300072, China 2 Key Laboratory of Mechanism eory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China 3 School of Mechanical Engineering, Tianjin University of Commerce, Tianjin 300134, China Correspondence should be addressed to Taiyong Wang; [email protected] Received 30 July 2016; Revised 21 October 2016; Accepted 14 November 2016 Academic Editor: Jaromir Horacek Copyright ยฉ 2016 Lei Zhang et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An analytical modeling approach for ball screw feed drives is proposed to predict the dynamic behavior of the feeding carriage of a spindle. Mainly considering the rigidity of linear guide modules, a ball-screw-feeding spindle is modeled by a mass-spring system. e contact sti๏ฌ€ness of rolling interfaces in linear guide modules is accurately calculated according to the Hertzian theory. Next, a mathematical model is derived using the Lagrange method. e presented model is veri๏ฌed by conducting modal experiments. It is found that the simulated results correspond closely with the experimental data. In order to show the applicability of the proposed mathematical model, parameter-dependent dynamics of the feeding carriage of the spindle is investigated. e work will contribute to the vibration prediction of spindles. 1. Introduction Ball screw feed drives are frequently used to position the spindle (or stage) to the desired location due to their high sti๏ฌ€ness and accuracy. e positioning precision and e๏ฌƒciency directly determine the quality and productivity of machine tools [1]. Hence, it is necessary to possess insight into the e๏ฌ€ect of ball screw feed drives on the dynamic characteristics of spindles or stages. It has become mainstream to consider the e๏ฌ€ect of ball screw feed drives in the study of dynamic characteristics of stages. For instance, taking the sti๏ฌ€ness of the ball bearings, the screw sha๏ฌ…, and the screw-nut interface into account, the vibration characteristics of the stage were investigated by means of lumped-parameter method [2โ€“5]. Besides, con- sidering the e๏ฌ€ects of the preload and rigidity of linear guide modules, the vibration characteristics of the stage were researched using the FE method [6โ€“9]. In the analytical model of a linear feeding stage [10], the rigidity of linear guide modules was also taken into account. However, the rolling interfaces between the guide rail and slider were oversimpli๏ฌed. Brie๏ฌ‚y, the ball screw feed drives have a strong in๏ฌ‚uence on the dynamic behavior of stages. Nevertheless, the modeling accuracy of the linear guide module requires further improvement. Research on the dynamic behavior of spindles was con- ducted using a variety of approaches [11โ€“13]. e dynamic models accounted for the spindle sha๏ฌ… and bearing, the holder and cutter, and the frame structure of machine tools. However, the mechanical characteristics of ball screw feed drives were rarely taken into consideration. Preloading of the ball screw feed drive was considered and the dynamic behavior of a vertical column-spindle system was analyzed by Hung et al. [14, 15]. But, it is time-consuming to obtain the desired results with the FE model. erefore, further research on the vibration characteristics of spindles under the in๏ฌ‚uences of ball screw feed drives should be conducted. In order to make a contribution to the vibration pre- diction of spindles, an analytical modeling approach is proposed to establish a mathematical model for a ball-screw- feeding spindle system (BSFSS). e BSFSS is simpli๏ฌed as a mass-spring system with six degrees of freedom. e rolling interfaces in linear guide modules are emphatically considered and accurately described. e motion equations Hindawi Publishing Corporation Mathematical Problems in Engineering Volume 2016, Article ID 2739208, 8 pages http://dx.doi.org/10.1155/2016/2739208

Upload: others

Post on 19-Feb-2021

2 views

Category:

Documents


0 download

TRANSCRIPT

  • Research ArticleAnalytical Modeling of a Ball Screw Feed Drive for VibrationPrediction of Feeding Carriage of a Spindle

    Lei Zhang,1,2 Taiyong Wang,1,2 Songling Tian,1,2 and Yong Wang1,3

    1School of Mechanical Engineering, Tianjin University, Tianjin 300072, China2Key Laboratory of MechanismTheory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China3School of Mechanical Engineering, Tianjin University of Commerce, Tianjin 300134, China

    Correspondence should be addressed to Taiyong Wang; [email protected]

    Received 30 July 2016; Revised 21 October 2016; Accepted 14 November 2016

    Academic Editor: Jaromir Horacek

    Copyright ยฉ 2016 Lei Zhang et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

    An analytical modeling approach for ball screw feed drives is proposed to predict the dynamic behavior of the feeding carriage of aspindle. Mainly considering the rigidity of linear guide modules, a ball-screw-feeding spindle is modeled by a mass-spring system.The contact stiffness of rolling interfaces in linear guide modules is accurately calculated according to the Hertzian theory. Next, amathematical model is derived using the Lagrange method.The presented model is verified by conducting modal experiments. It isfound that the simulated results correspond closely with the experimental data. In order to show the applicability of the proposedmathematical model, parameter-dependent dynamics of the feeding carriage of the spindle is investigated.Thework will contributeto the vibration prediction of spindles.

    1. Introduction

    Ball screw feed drives are frequently used to position thespindle (or stage) to the desired location due to theirhigh stiffness and accuracy. The positioning precision andefficiency directly determine the quality and productivity ofmachine tools [1]. Hence, it is necessary to possess insightinto the effect of ball screw feed drives on the dynamiccharacteristics of spindles or stages.

    It has become mainstream to consider the effect of ballscrew feed drives in the study of dynamic characteristics ofstages. For instance, taking the stiffness of the ball bearings,the screw shaft, and the screw-nut interface into account,the vibration characteristics of the stage were investigatedby means of lumped-parameter method [2โ€“5]. Besides, con-sidering the effects of the preload and rigidity of linearguide modules, the vibration characteristics of the stage wereresearched using the FE method [6โ€“9]. In the analyticalmodel of a linear feeding stage [10], the rigidity of linearguide modules was also taken into account. However, therolling interfaces between the guide rail and slider wereoversimplified. Briefly, the ball screw feed drives have a strong

    influence on the dynamic behavior of stages. Nevertheless,the modeling accuracy of the linear guide module requiresfurther improvement.

    Research on the dynamic behavior of spindles was con-ducted using a variety of approaches [11โ€“13]. The dynamicmodels accounted for the spindle shaft and bearing, theholder and cutter, and the frame structure of machine tools.However, the mechanical characteristics of ball screw feeddrives were rarely taken into consideration. Preloading ofthe ball screw feed drive was considered and the dynamicbehavior of a vertical column-spindle system was analyzedby Hung et al. [14, 15]. But, it is time-consuming to obtainthe desired results with the FE model. Therefore, furtherresearch on the vibration characteristics of spindles under theinfluences of ball screw feed drives should be conducted.

    In order to make a contribution to the vibration pre-diction of spindles, an analytical modeling approach isproposed to establish a mathematical model for a ball-screw-feeding spindle system (BSFSS). The BSFSS is simplifiedas a mass-spring system with six degrees of freedom. Therolling interfaces in linear guide modules are emphaticallyconsidered and accurately described. The motion equations

    Hindawi Publishing CorporationMathematical Problems in EngineeringVolume 2016, Article ID 2739208, 8 pageshttp://dx.doi.org/10.1155/2016/2739208

  • 2 Mathematical Problems in Engineering

    y

    z

    x

    ba

    Ball bearing NutFeeding carriage

    Ball screw Ball bearing

    Linear guidemodule

    Spindle

    l

    lef

    Figure 1: Schematic drawing of the BSFSS.

    y

    z

    x

    kna

    knrkbskb

    m

    (a)

    v

    u

    w

    d d

    cc

    y

    z

    x

    ๐œƒ

    d0

    c0

    ๐œ™

    ๐œ‘ki1

    ki2 ki3

    ki4

    ๐›ฝ

    (b)

    Figure 2: Simplified mechanical model of the BSFSS.

    and numerical solutions are derived.The modal experimentsare conducted for validation of the presented model. Withthe proposed mathematical model, parameter-dependentdynamics of the feeding carriage of the spindle (FCoS) is alsodiscussed. Finally, a conclusion is drawn.

    2. Analytical Modeling Approach

    2.1. Dynamic Model. A BSFSS considered here is shown inFigure 1. The spindle is fixed on the feeding carriage. Thefeeding carriage driven by the ball screw is mounted onthe machine base through a pair of linear guides. The ballscrew is supported by ball bearings. At the left end, twoangular contact ball bearings are mounted back to back tosustain the axial and radial forces. At the right end, one deepgroove ball bearing is installed to provide the radial force.Thecommercial linear guide module (composed of a linear guideand a slider) has four ball grooves with a circular arc profileforming a point contact at the angle of 45 degrees. The linearguide module can be preloaded at a different amount. Thepreloads are quantified as low preload (Z0, 0.01๐ถ), mediumpreload (ZA, 0.06๐ถ), and high preload (ZB, 0.11๐ถ), where ๐ถdenotes the dynamic load rating (7.83 kN) [16].

    The joints between the spindle and feeding carriage alsoinfluence the dynamic behavior of the spindle. For simplifi-cation, the joint stiffness is assumed to be infinite. And the

    spindle and feeding carriage are represented together as arigid body with a total mass of ๐‘š, as depicted in Figure 2(a).The ball bearings at the left end aremodeled by a linear elasticconnection with axial stiffness ๐‘˜๐‘. The radial stiffness of ballbearings mainly determines the bending vibration of the ballscrew. In the study of the axial and torsional vibration of theball screw, the radial stiffness of ball bearings is normallyneglected [5, 17, 18]. Inspired by those studies, the radialstiffness of ball bearings is not considered in the model here.The screw shaft is simplified as a linear elastic connectionwithaxial stiffness ๐‘˜bs.The screw-nut interface is endowed with anaxial stiffness ๐‘˜na and a torsional stiffness ๐‘˜nr.

    The rigidity of the linear guide module is governed by thecontact stiffness of rolling interfaces between rolling balls andgrooves because the guide rail and slider are more rigid instructure. Hence, by neglecting the mass of rolling balls, eachslider is assumed to be supported by four spring elementsin the direction of the contact angle. The spring elementis located at the middle of each ball groove longitudinally.As shown in Figure 2(b), the spring elements are quantifiedwith stiffness values ๐‘˜๐‘–1, ๐‘˜๐‘–2, ๐‘˜๐‘–3, and ๐‘˜๐‘–4 for each linear guidemodule (๐‘– = 1, 2, 3, 4).

    A coordinate system for vibration motions of the FCoSis illustrated in Figure 2(b). The origin of the coordinatesystem is the gravity center of the simplified rigid body ๐‘š.The feeding direction of the spindle is along ๐‘ฅ-axis. ๐‘ ยฑ ๐‘0 and

  • Mathematical Problems in Engineering 3

    ๐›ฝ

    Q

    Q

    R2

    R1Oc Or

    Figure 3: Contact model of the ball and grooves.

    ๐‘‘ ยฑ ๐‘‘0 are the distances from the contact points betweenthe rolling balls and sliders to x-y plane and x-z plane,respectively. As depicted in Figure 1, ๐‘Ž and ๐‘ are defined asthe distances from the contact points to y-z plane.

    According to the aforementioned simplification, theBSFSS is modeled as a mass-spring system. The vibrationmodes associated with the motion degrees of freedom can bedefined. The translational motions ๐‘ข, V, and ๐‘ค are defined aslinear displacements in axial, lateral, and vertical directions,respectively. The displacement in the axial direction is calledaxial vibration mode. The rocking motion ๐œ‘ about ๐‘ฅ-axis isknown as rolling vibrationmode.The rockingmotion๐œ™ abouty-axis is pitching vibration mode and the rocking motion ๐œƒabout z-axis is yawing vibration mode.

    2.2. Contact Stiffness of Rolling Interfaces. In the linear guidemodule, the stiffness of the spring elements is determined bythe contact characteristics of rolling interfaces. The contactstiffness of the rolling interface can be calculated accordingto the Hertzian theory [19]. As illustrated in Figure 3, ๐‘…1is the radius of the ball, ๐‘…2 is the radius of grooves in theguide rail and the slider, ๐›ฝ is the contact angle, and๐‘„ denotesthe contact force. To enhance the accuracy of the model, thecontact is regarded as elastic.

    The contact force can be related to the local deformationat the contact point by the Hertzian expression [20]:

    ๐‘„ = ๐‘˜โ„Ž๐‘‘3/2, (1)where ๐‘‘ is the elastic deformation at the contact point.๐‘˜โ„Ž [N/m3/2] representing the Hertz constant is determined as

    ๐‘˜โ„Ž = 4โˆš23๐ต3/2๐ธ๐‘…1/2 , (2)where

    ๐ธ = 1 โˆ’ ๐‘ข21๐ธ1 + 1 โˆ’ ๐‘ข22๐ธ2 ,

    ๐‘… = ๐œŒ11 + ๐œŒ12 + ๐œŒ21 + ๐œŒ22 = 1๐‘…1 + 1๐‘…1 + 0 โˆ’ 1๐‘…2 ,๐‘“ (๐œŒ) = (๐œŒ11 โˆ’ ๐œŒ12) + (๐œŒ21 โˆ’ ๐œŒ22)๐‘… .

    (3)

    In the above equations, ๐ธ [m2/N] describes the compre-hensive material property of the ball and groove. ๐ธ1 and ๐ธ2are Youngโ€™s modulus for materials of the ball and groove,respectively. ๐‘ข1 and ๐‘ข2 are Poissonโ€™s ratios. ๐‘… [mโˆ’1] is thesynthetic curvature of the ball and groove. ๐ต, named as theHertz coefficient, can be obtained based on the value of ๐‘“(๐œŒ)[21]. ๐‘“(๐œŒ) and ๐ต are both dimensionless.The contact stiffness๐พ๐‘› between the ball and groove can then be obtained using

    ๐พ๐‘› = d๐‘„d๐‘‘ = 32๐‘˜โ„Ž๐‘‘1/2 = 32๐‘˜2/3โ„Ž ๐‘„1/3. (4)As revealed in (4), the contact stiffness depends nonlin-

    early on the contact force, which is essentially determined bythe preload set on the rolling ball.

    2.3. Mathematical Model and Analytical Solution. Thekineticenergy ๐‘‡ regarding the mass and inertia of the system is

    ๐‘‡ = 12๐‘š๏ฟฝฬ‡๏ฟฝ2 + 12๐‘šVฬ‡2 + 12๐‘š๏ฟฝฬ‡๏ฟฝ2 + 12๐ฝ๐‘ฅ๏ฟฝฬ‡๏ฟฝ2 + 12๐ฝ๐‘ฆ๏ฟฝฬ‡๏ฟฝ2+ 12๐ฝ๐‘ง๏ฟฝฬ‡๏ฟฝ2.

    (5)

    The potential energy๐‘ˆ, due to the ball bearing, the ball screw,and the linear guide module, can be written as

    ๐‘ˆ = 4โˆ‘๐‘–=1

    4โˆ‘๐‘—=1

    12๐‘˜๐‘–๐‘—๐›ฟ2๐‘–๐‘— + 12๐‘˜eq๐‘ข2 + 12๐‘˜nr๐œ‘2

    = 4โˆ‘๐‘–=1

    12 [๐‘˜๐‘–1 (๐ด ๐‘–1 cos๐›ฝ + ๐ต๐‘–1 sin๐›ฝ)2+ ๐‘˜๐‘–2 (๐ด ๐‘–2 cos๐›ฝ โˆ’ ๐ต๐‘–2 sin๐›ฝ)2+ ๐‘˜๐‘–3 (๐ด ๐‘–3 cos๐›ฝ + ๐ต๐‘–3 sin๐›ฝ)2+ ๐‘˜๐‘–4 (๐ด ๐‘–4 cos๐›ฝ โˆ’ ๐ต๐‘–4 sin๐›ฝ)2] + 12๐‘˜eq๐‘ข2 + 12๐‘˜nr๐œ‘2,

    (6)

    where

    ๐ด11 = V + (๐‘ + ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต11 = ๐‘ค โˆ’ (๐‘‘ + ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด12 = V + (๐‘ โˆ’ ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต12 = ๐‘ค โˆ’ (๐‘‘ + ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด13 = V + (๐‘ โˆ’ ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต13 = ๐‘ค โˆ’ (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด14 = V + (๐‘ + ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต14 = ๐‘ค โˆ’ (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด21 = V โˆ’ (๐‘ + ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต21 = ๐‘ค + (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,

  • 4 Mathematical Problems in Engineering

    ๐ด22 = V โˆ’ (๐‘ โˆ’ ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต22 = ๐‘ค + (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด23 = V โˆ’ (๐‘ โˆ’ ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต23 = ๐‘ค + (๐‘‘ + ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด24 = V โˆ’ (๐‘ + ๐‘0) ๐œ‘ + ๐‘Ž๐œƒ,๐ต24 = ๐‘ค + (๐‘‘ + ๐‘‘0) ๐œ‘ โˆ’ ๐‘Ž๐œ™,๐ด31 = V โˆ’ (๐‘ + ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต31 = ๐‘ค + (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด32 = V โˆ’ (๐‘ โˆ’ ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต32 = ๐‘ค + (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด33 = V โˆ’ (๐‘ โˆ’ ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต33 = ๐‘ค + (๐‘‘ + ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด34 = V โˆ’ (๐‘ + ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต34 = ๐‘ค + (๐‘‘ + ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด41 = V + (๐‘ + ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต41 = ๐‘ค โˆ’ (๐‘‘ + ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด42 = V + (๐‘ โˆ’ ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต42 = ๐‘ค โˆ’ (๐‘‘ + ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด43 = V + (๐‘ โˆ’ ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต43 = ๐‘ค โˆ’ (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ + ๐‘๐œ™,๐ด44 = V + (๐‘ + ๐‘0) ๐œ‘ โˆ’ ๐‘๐œƒ,๐ต44 = ๐‘ค โˆ’ (๐‘‘ โˆ’ ๐‘‘0) ๐œ‘ + ๐‘๐œ™.

    (7)

    In the above equations, ๐ฝ๐‘ฅ, ๐ฝ๐‘ฆ, and ๐ฝ๐‘ง are moments ofinertia of the simplified rigid body ๐‘š about x-axis, y-axis,and z-axis, respectively. ๐›ฟ๐‘–๐‘— is the displacement of the slider.The subscripts ๐‘– = 1, 2, 3, 4 represent the four sliders. Thesubscripts ๐‘— = 1, 2, 3, 4 represent the four rows of grooves ineach slider.

    Assume that all the linear guide modules have thesame specifications and preloaded amounts and that all thevibration motions meet the small displacement assumption.The stiffness of the spring elements can then be presented as

    ๐‘˜๐‘–1 = ๐‘˜๐‘–2 = ๐‘˜๐‘–3 = ๐‘˜๐‘–4 = ๐‘˜ = ๐พ๐‘›2 , ๐‘– = 1, 2, 3, 4. (8)As shown in Figure 2(a), the linear elastic connections ๐‘˜๐‘,๐‘˜bs, and ๐‘˜na are in series. Hence, the equivalent axial stiffness

    can be derived as 1๐‘˜eq = 1๐‘˜๐‘ + 1๐‘˜bs + 1๐‘˜na , (9)

    where

    ๐‘˜bs = ๐ธ๐œ‹๐ท24๐‘™ef , (10)with Youngโ€™s modulus ๐ธ, the diameter ๐ท, and the equivalentlength ๐‘™ef of the screw shaft. The torsional stiffness of thescrew-nut interface can be obtained using

    ๐‘˜nr = ( ๐‘2๐œ‹)2 ๐‘˜na (11)with lead p of the screw shaft.

    Applying the Lagrange approach to (5)โ€“(11), the motionequations of the mass-spring system can be derived:

    ๐‘š๏ฟฝฬˆ๏ฟฝ + ๐‘˜eq๐‘ข = 0,๐‘šVฬˆ + 16๐‘˜ cos2๐›ฝ โ‹… V + 8๐‘˜ (๐‘Ž โˆ’ ๐‘) cos2๐›ฝ โ‹… ๐œƒ = 0,๐‘š๏ฟฝฬˆ๏ฟฝ + 16๐‘˜ sin2๐›ฝ โ‹… ๐‘ค + 8๐‘˜ (๐‘ โˆ’ ๐‘Ž) sin2๐›ฝ โ‹… ๐œ™ = 0,๐ฝ๐‘ฅ๏ฟฝฬˆ๏ฟฝ + 16๐‘˜ [(๐‘2 + ๐‘20 ) cos2๐›ฝ + (๐‘‘2 + ๐‘‘20) sin2๐›ฝ] ๐œ‘+ ๐‘˜nr๐œ‘ = 0,

    ๐ฝ๐‘ฆ๏ฟฝฬˆ๏ฟฝ + 8๐‘˜ (๐‘Ž2 + ๐‘2) sin2๐›ฝ โ‹… ๐œ™+ 8๐‘˜ (๐‘ โˆ’ ๐‘Ž) sin2๐›ฝ โ‹… ๐‘ค = 0,

    ๐ฝ๐‘ง๏ฟฝฬˆ๏ฟฝ + 8๐‘˜ (๐‘Ž2 + ๐‘2) cos2๐›ฝ โ‹… ๐œƒ + 8๐‘˜ (๐‘ โˆ’ ๐‘Ž) cos2๐›ฝ โ‹… V = 0.

    (12)

    It is noticed that the first motion equation governs thedisplacement u along x-axis, and the fourth motion equationdescribes the angular displacement ๐œ‘ about x-axis. Thenatural frequencies including the axial (๐‘“๐ด) and rolling (๐‘“๐‘…)modes can be calculated using

    ๐‘“๐ด = 12๐œ‹โˆš๐‘˜eq๐‘š ,๐‘“๐‘… = 12๐œ‹โ‹… โˆš 16๐‘˜ [(๐‘2 + ๐‘20 ) cos2๐›ฝ + (๐‘‘2 + ๐‘‘20) sin2๐›ฝ] + ๐‘˜nr๐ฝ๐‘ฅ .

    (13)

    As revealed in (12), the linear displacement v and theangular displacement ๐œƒ are highly coupled. The solution isassumed to be the form

    V = V โ‹… ๐‘’๐‘—๐œ”๐‘ก,๐œƒ = ๐œƒ โ‹… ๐‘’๐‘—๐œ”๐‘ก. (14)

    Substituting (14) into the second and the sixth motionequations of (12), the characteristic equation can be derivedas

    ๐‘š๐ฝ๐‘ง๐œ”4 โˆ’ (๐ต1๐ฝ๐‘ง + ๐ต2๐‘š)๐œ”2 + ๐ต1๐ต2 โˆ’ ๐ต23 = 0, (15)

  • Mathematical Problems in Engineering 5

    where

    ๐ต1 = 16๐‘˜ cos2๐›ฝ,๐ต2 = 8๐‘˜ (๐‘Ž2 + ๐‘2) cos2๐›ฝ,๐ต3 = 8๐‘˜ (๐‘Ž โˆ’ ๐‘) cos2๐›ฝ.

    (16)

    Similarly, the characteristic equation for the linear displace-ment ๐‘ค and the angular displacement ๐œ™ can also be derivedas

    ๐‘š๐ฝ๐‘ฆ๐œ”4 โˆ’ (๐ถ1๐ฝ๐‘ฆ + ๐ถ2๐‘š)๐œ”2 + ๐ถ1๐ถ2 โˆ’ ๐ถ23 = 0, (17)where

    ๐ถ1 = 16๐‘˜ sin2๐›ฝ,๐ถ2 = 8๐‘˜ (๐‘Ž2 + ๐‘2) sin2๐›ฝ,๐ถ3 = 8๐‘˜ (๐‘ โˆ’ ๐‘Ž) sin2๐›ฝ.

    (18)

    Finally, the natural frequencies of the yawing (๐‘“๐‘Œ) andpitching (๐‘“๐‘ƒ)modes are computed as

    ๐‘“๐‘Œ = ๐œ”12๐œ‹ ,๐‘“๐‘ƒ = ๐œ”22๐œ‹ ,

    (19)

    where

    ๐œ”21= ๐ต1๐ฝ๐‘ง + ๐ต2๐‘š โˆ’ โˆš(๐ต1๐ฝ๐‘ง + ๐ต2๐‘š)2 โˆ’ 4๐‘š๐ฝ๐‘ง (๐ต1๐ต2 โˆ’ ๐ต23)2๐‘š๐ฝ๐‘ง ,๐œ”22= ๐ถ1๐ฝ๐‘ฆ + ๐ถ2๐‘š โˆ’ โˆš(๐ถ1๐ฝ๐‘ฆ + ๐ถ2๐‘š)

    2 โˆ’ 4๐‘š๐ฝ๐‘ฆ (๐ถ1๐ถ2 โˆ’ ๐ถ23)2๐‘š๐ฝ๐‘ฆ .

    (20)

    The parameters of the BSFSS are either obtained frommanufacturersโ€™ catalogs or computed from the CAD modelof the components, as listed in Table 1. With the low preloadset on the linear guide modules (๐‘˜ = 1.9888N/๐œ‡m) andthe spindle positioned at the middle of its travel range(๐‘™ef = 242.5mm), the natural frequencies associated withthe fundamental vibration modes of the FCoS are calculatedand listed in Table 2. Substituting the eigenvalues into thecharacteristic equation, the corresponding eigenvectors canalso be derived, which describe the vibration modes. Theyawingmode (๐‘“๐‘Œ) stands for the coupling of the translationalmotion v and the rocking motion ๐œƒ, in which the rockingmotion ๐œƒ is primary. The pitching mode (๐‘“๐‘ƒ) expresses thecoupling of the translational motion ๐‘ค and the rockingmotion ๐œ™, where the rocking motion ๐œ™ is dominant. Therolling mode (๐‘“๐‘…)means the rocking motion ๐œ‘, and the axialmode (๐‘“๐ด) represents the translational motion ๐‘ข.

    Table 1: Parameters of the BSFSS.

    Parameter Value Unit๐‘…1 and ๐‘…2 1.389๐‘’ โˆ’ 3 and 1.45๐‘’ โˆ’ 3 m๐ธ1 = ๐ธ2 2.06e11 Pa๐‘ข1 = ๐‘ข2 0.3 โ€”๐›ฝ ๐œ‹/4 rad๐ธ 2.11e11 Pa๐‘™,๐ท, and ๐‘ 0.78, 0.016, and 0.005 m๐‘š 13.7 Kg๐ฝ๐‘ฅ, ๐ฝ๐‘ฆ, and ๐ฝ๐‘ง 0.06, 0.016, and 0.12 Kgโ‹…m2๐‘˜๐‘ and ๐‘˜na 2.45e7 and 1.078e8 N/m๐‘˜ (low, middle, and highpreload) 1.9888e6, 3.6139e6, and 4.4231e6 N/m๐‘Ž and ๐‘ 0.0195 and 0.0445 m๐‘ and ๐‘0 0.093 and 0.0025 m๐‘‘ and ๐‘‘0 0.0325 and 0.0075 mTable 2: Predicted and experimental natural frequencies of theBSFSS.

    Vibrationmode Prediction/Hz Experiment/Hz Relative error/%

    Yawing mode 36.7 35.1 4.56%Pitching mode 86.7 81.8 5.99%Rolling mode 162.1 149.1 8.72%Axial mode 182.0 166.3 9.44%

    P1

    P2

    P3

    P4P5 P5

    P4y

    z

    x

    Figure 4: Experimental setup.

    3. Experimental Validation and Discussion

    3.1.Modal Test Validation. As depicted in Figure 4, themodaltest is conducted on a ball-screw-feeding spindle setup. Thelinear guide modules are preloaded at low amounts (Z0)and the spindle is positioned at the middle of its travelrange. Using the impact testing method, the hammeringpoint is placed on the side (small dot) of the feeding carriagein the opposite direction of x-axis. Four accelerometersare arranged at the corners on the upper surface of thefeeding carriage. Another accelerometer is located near thehammering point. The accelerometer at point P1 can obtainthree-direction acceleration signals.The three accelerometersat points P2, P3, and P4 can obtain the acceleration signals inthe direction of z-axis. The last accelerometer at point P5 canobtain the acceleration signals in the direction of x-axis. Thedirections of the signals are consistentwith those of the BSFSScoordinates, and three tests are performed.

    With the impulse excitations at point P5, the FRFs ofpoint P1 (in three directions), point P2 (in the direction

  • 6 Mathematical Problems in Engineering

    P1zP1yP1x

    P2zP5x

    3582

    149

    166

    231

    200 250 30010050 1500Frequency (Hz)

    0

    0.005

    0.01

    0.015

    0.02

    0.025

    0.03

    Am

    plitu

    de (d

    B)

    Figure 5: FRFs of points P1, P2, and P5.

    of z-axis), and point P5 (in the direction of x-axis) areobtained using the LMS impact testing system. As illustratedin Figure 5, the natural frequency at 35Hz stands for theyawing dominant vibration, which excites the accelerationin the direction of y-axis. The pitching dominant vibrationat 82Hz and the rolling dominant vibration at 149Hz bothinduce the acceleration in the direction of z-axis. The axialdominant vibration at 166Hz arouses the acceleration inthe direction of x-axis. The coupling vibration of the rigidpitching mode and the flexible bending mode at 231Hz,which is not contained in the mathematical model, alsocauses the acceleration in the direction of z-axis.

    With the FRFs, the dynamic parameters at low frequen-cies can be estimated. The experimental natural frequenciesof different vibration modes are listed in Table 2 for com-parison. The maximum relative error between the predictednatural frequency and the experimental natural frequencyis 9.44%. According to the LMS modal analysis software,the modal damping ratio of the vibration modes, rangingfrom 0.83% to 9.05%, can be estimated. The low dampingratio has little effect on the natural frequency estimation.It can be concluded that the predicted results have a goodagreement with the experiment. The deviation may be dueto the inaccuracy or ignorance of various stiffness, damping,and inertia.

    3.2. Effects of Structural Parameters. According to the pro-posed mathematical model of the BSFSS, some numer-ical simulations have been conducted to investigate theparameter-dependent dynamics of the FCoS. Figure 6 depictsthe dependence of natural frequencies on the preload set onthe linear guidemodule.This reveals apparent dependence ofnatural frequencies associated with the yawing and pitchingmodes on the preload. It is also shown that the preload hasa strong influence on the natural frequency correspondingto the rolling mode. For the natural frequency of the axialmode, the preload has no effect at all. The reason is that theaxial mode is mainly determined by the stiffness of the ballbearings, the ball screw, and the screw-nut interface ratherthan the rigidity of the linear guide module.

    36.749.5

    54.8

    86.7

    116.9129.4

    162.1

    218.4241.7

    182.0

    YawingPitching

    RollingAxial

    ZA ZBZ0Preload (N)

    50

    100

    150

    200

    250

    Freq

    uenc

    y (H

    z)

    Figure 6: Dependence of the natural frequencies on the preload.

    36.748.1

    59.570.8

    86.799.1 103.6

    105.5

    162.1

    182

    YawingPitching

    RollingAxial

    10080 907060 120 130110Span of sliders (mm)

    40

    60

    80

    100

    120

    140

    160

    180

    Freq

    uenc

    y (H

    z)

    Figure 7: Influence of the span of sliders on the natural frequencies.

    On the other hand, Figure 7 presents the influence of thespan of sliders on the natural frequencies. With the span ofsliders increasing from 64mm to 124mm, the yawing naturalfrequency changes from 36.7Hz to 70.8Hz, and the pitchingnatural frequency increases to 105.5Hz from the original86.7Hz. Obviously, the span of sliders has no effect on thenatural frequencies of the rolling mode and axial mode.

    As observed from the analysis, the dependence of naturalfrequencies for the FCoS on various structural parametersis distinct. When the preload and span of sliders change,the maximum changing rates of natural frequencies reach49.1% and 21.7%, respectively. Meanwhile, the preload andspan of sliders both have no effect on certain natural

  • Mathematical Problems in Engineering 7

    frequencies. Hence, the analysis and obtaining parameter-dependent dynamics of the FCoS are useful and meaningful.The selection of ball screw feed drives can be rapidly finalizedso that the dynamic characteristics of the FCoS can beoptimized in prototyping design.

    In the engineering practice, the lateral and vertical defor-mation of the ball screw, which is neglected in the proposedmodel, may have some influence on the yawing and pitchingvibrations of the FCoS, especiallywith the FCoS feeding alongthe ball screw. Hence, the bending deformation of the ballscrew will be additionally considered in the future work.

    4. Conclusions

    Mainly considering the rolling interfaces in the linear guidemodules, a mathematical model of the BSFSS is derived. Thepredicted results correspond closely with the experimentaldata. The ball screw feed drive, especially the linear guidemodule, is shown to determine the vibration behavior of theFCoS. The bending deformation of the ball screw and thebearing stiffness of the spindle will be additionally consideredto predict the dynamic behavior of spindles.

    With the mathematical model, the vibration behavior ofthe FCoS is rapidly analyzed for various structural param-eters. This will be helpful for optimizing the structuralparameters of ball screw feed drives in prototyping design.

    Competing Interests

    The authors declare that there are no competing interestsregarding the publication of this paper.

    Acknowledgments

    The authors would like to thank Mr. Guofeng Wang for hishelp in design and manufacturing of the experimental setup.And this work was supported in part by National Natural Sci-ence Foundation of China (Grant no. 51475324) and NaturalScience Foundation of Tianjin (Grant no. 13JCZDJC34000).

    References

    [1] Y. Altintas, A. Verl, C. Brecher, L. Uriarte, and G. Pritschow,โ€œMachine tool feed drives,โ€ CIRP Annalsโ€”Manufacturing Tech-nology, vol. 60, no. 2, pp. 779โ€“796, 2011.

    [2] R. Wang, T. Zhao, P. Ye, and Y. Liu, โ€œThree-dimensionalmodeling for predicting the vibration modes of twin ballscrew driving table,โ€ Chinese Journal of Mechanical Engineering(English Edition), vol. 27, no. 1, pp. 211โ€“218, 2014.

    [3] S. Frey, A. Dadalau, and A. Verl, โ€œExpedient modeling of ballscrew feed drives,โ€Production Engineering, vol. 6, no. 2, pp. 205โ€“211, 2012.

    [4] H. J. Zhang, J. Zhang, H. Liu, T. Liang, and W. H. Zhao,โ€œDynamic modeling and analysis of the high-speed ball screwfeed system,โ€ Proceedings of the Institution of Mechanical Engi-neers, Part B: Journal of Engineering Manufacture, vol. 229, no.5, pp. 870โ€“877, 2015.

    [5] Y. Zhou, F. Y. Peng, and X. H. Cao, โ€œParameter sensitivityanalysis of axial vibration for lead-screw feed drives with time-varying framework,โ€Mechanika, vol. 17, no. 5, pp. 523โ€“528, 2011.

    [6] L. Mi, G.-F. Yin, M.-N. Sun, and X.-H. Wang, โ€œEffects ofpreloads on joints on dynamic stiffness of a whole machine toolstructure,โ€ Journal ofMechanical Science andTechnology, vol. 26,no. 2, pp. 495โ€“508, 2012.

    [7] D. Wang, Y. Lu, T. Zhang, K. Wang, and A. Rinoshika, โ€œEffectof stiffness of rolling joints on the dynamic characteristic of ballscrew feed systems in a milling machine,โ€ Shock and Vibration,vol. 2015, Article ID 697540, 2015.

    [8] Y.-L. Lai and J.-P. Hung, โ€œInfluence of linear guide arrangementon the vibration characteristics of a positioning stage,โ€ Journalof the Chinese Society of Mechanical Engineers, vol. 33, no. 2, pp.113โ€“122, 2012.

    [9] W. Sun, X. Kong, and B. Wang, โ€œPrecise finite element mod-eling and analysis of dynamics of linear rolling guideway onsupporting direction,โ€ Journal of Vibroengineering, vol. 15, no.3, pp. 1330โ€“1340, 2013.

    [10] J.-C. Chang and J.-P. Hung, โ€œAnalytical and finite elementmodeling of the dynamic characteristics of a linear feeding stagewith different arrangements of rolling guides,โ€ MathematicalProblems in Engineering, vol. 2014, Article ID 454156, 11 pages,2014.

    [11] A. Ertuฬˆrk, H. N. Oฬˆzguฬˆven, and E. Budak, โ€œAnalytical modelingof spindle-tool dynamics on machine tools using Timoshenkobeam model and receptance coupling for the prediction oftool point FRF,โ€ International Journal of Machine Tools andManufacture, vol. 46, no. 15, pp. 1901โ€“1912, 2006.

    [12] J.-P. Hung, Y.-L. Lai, T.-L. Luo, and H.-C. Su, โ€œAnalysis ofthe machining stability of a milling machine considering theeffect of machine frame structure and spindle bearings: exper-imental and finite element approaches,โ€ International Journalof Advanced Manufacturing Technology, vol. 68, no. 9โ€“12, pp.2393โ€“2405, 2013.

    [13] C.-W. Lin, Y.-K. Lin, and C.-H. Chu, โ€œDynamic models anddesign of spindle-bearing systems of machine tools: a review,โ€International Journal of Precision Engineering and Manufactur-ing, vol. 14, no. 3, pp. 513โ€“521, 2013.

    [14] C. Yuan Lin, J. Pin Hung, and T. Liang Lo, โ€œEffect of preload oflinear guides on dynamic characteristics of a vertical columnโ€”spindle system,โ€ International Journal of Machine Tools andManufacture, vol. 50, no. 8, pp. 741โ€“746, 2010.

    [15] J.-P. Hung, Y.-L. Lai, C.-Y. Lin, and T.-L. Lo, โ€œModeling themachining stability of a vertical milling machine under theinfluence of the preloaded linear guide,โ€ International Journalof Machine Tools and Manufacture, vol. 51, no. 9, pp. 731โ€“739,2011.

    [16] Hiwin Technologies Company, Hiwin Linear Guideway Techni-cal Information, Hiwin Company, Hiwin, Taiwan, 2000.

    [17] D. A. Vicente, R. L. Hecker, F. J. Villegas, and G. M. Flores,โ€œModeling and vibration mode analysis of a ball screw drive,โ€International Journal of Advanced Manufacturing Technology,vol. 58, no. 1โ€“4, pp. 257โ€“265, 2012.

    [18] B. Henke, O. Sawodny, and R. Neumann, โ€œDistributed param-eter modeling of flexible ball screw drives using ritz seriesdiscretization,โ€ IEEE/ASME Transactions on Mechatronics, vol.20, no. 3, pp. 1226โ€“1235, 2015.

    [19] D. E. Brewe and B. J. Hamrock, โ€œSimplified solution forelliptical-contact deformation between two elastic solids,โ€ Jour-nal of Lubrication Technology, vol. 99, no. 4, pp. 485โ€“487, 1977.

  • 8 Mathematical Problems in Engineering

    [20] J. A. Greenwood, โ€œAnalysis of elliptical Hertzian contacts,โ€Tribology International, vol. 30, no. 3, pp. 235โ€“237, 1997.

    [21] S. Dai,ManualMachine Rolling Bearings Application Handbook,Mechanical Industry Press, Beijing, China, 1993.

  • Submit your manuscripts athttp://www.hindawi.com

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    MathematicsJournal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Mathematical Problems in Engineering

    Hindawi Publishing Corporationhttp://www.hindawi.com

    Differential EquationsInternational Journal of

    Volume 2014

    Applied MathematicsJournal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Probability and StatisticsHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Journal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Mathematical PhysicsAdvances in

    Complex AnalysisJournal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    OptimizationJournal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    CombinatoricsHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    International Journal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Operations ResearchAdvances in

    Journal of

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Function Spaces

    Abstract and Applied AnalysisHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    International Journal of Mathematics and Mathematical Sciences

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    The Scientific World JournalHindawi Publishing Corporation http://www.hindawi.com Volume 2014

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Algebra

    Discrete Dynamics in Nature and Society

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Decision SciencesAdvances in

    Discrete MathematicsJournal of

    Hindawi Publishing Corporationhttp://www.hindawi.com

    Volume 2014 Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

    Stochastic AnalysisInternational Journal of