The goal of this research was to investigate the performance of the Articulated Transporter and Manipulator System (ATMS) during various tasks relative to the choice of wrist/end-effector configuration. The approach taken was to generate computer graphics-aided three-dimensional interactive application (CATIA) system-based models of four wrist/end-effector combinations and consider the volumetric reach of each of these configurations based on the capacity of the ATMS. The results indicate that a simple, lightweight end-effector provides a greater volumetric reach. The greatest variation presented herein is {approximately}40% when comparing a 7-degree-of-freedom (DOF) dexterous arm with a simple 3-DOF arm; however, the benefit of increasing volumetric reach by only 40% by using a simple arm may be outweighed by the loss of dexterity. 10 refs., 5 figs., 3 tabs

Babcock, S. M.

Bills, K. C. (Martin Marietta Energy Systems, Inc., Oak Ridge, TN (USA))

Hamel, W. R. (Oak Ridge National Lab., TN (USA))

Kress, R. L.

UNT Digital Library

T.. ,._. /F:J 5 -......J' C0NF-910223--3_%.DEgl 004390/rc/,,_6_VOLUMETRIC REACH COMPARISON OF I_0POSSIBLE END-EFFECTORS FOR "THEARTICULATED TRANSPORTER AND L........MANIPULATOR SYSTEM* " ..R. L. KRESS, S. M. BABCOCK, and W. R. HAMELOak Ridge National Laborator), tRobotics and Process Systems DivisionPost Office Box 2008Oak Ridge, Tennessee 37831--6304o =rK. C. BILLS _=_=°="Martin Marietta Energy Systems, Inc. _ _=._, g _ _,_ _ v,Engineering Divison _: _ "' =: _ =Post Office Box 2009 = _ 9 _ _ " 'Oak Ridge, Tennessee 37831-8201 _ _ w _=_ _, z =_lrhOted by I! controclo,r of the U.S. m m . B _ _._ k _AC05-84OR21400. Aor.ord_. the U.S. m _ 1= _._,.o,_,,,o_,_ ,o,us._o.,.,.,,.,, _.= _ _ _, _ c_=,,, gPaper to be presented at the ,_-='_ _..-._,_,, e _ g__ _. = _=_AMERICAN NUCLEAR SOCIETY _ ,_ _ _ .. _ =_FOURTH TOPICAL MEETING ON ROBOTICS AND REMOTE SYSTEMS ,g_-__ 7_o='___Albuquerque, New Mexico _ 8 = _ _- ,, __,= _oFebruary 24-28, 1991 _ _ _ = o ,_ = " o._,._*Research sponsored by the Office of Nuclear Energy and _.heOffice of TechnologySupport Programs, U.S. Department of Energy, under Contract No. DE-AC05-84OR21400with Martin Marietta Energy Systems, Inc._TBIBUTIOI_OF THtr;/_,U_,_FNTI_ft_P_-.,,e._VOLUMETRIC REACH COMPARISON OFPOSSIBLE END-EFFECTORS FOR THEARTICULATED TRANSPORTER ANDMANIPULATOR SYSTEM*R. L. KRESS, S. M. BABCOCK, andW. R. HAMELOak Ridge National Laboratory fRobotics and Process Systems DivisionP.O. Box 2008Oak Ridge, Tennessee 37831-6304K. C. BILLSMartin Marietta Energy Systems. Inc.Engineering DivisionP.O. Box 2009Oak Ridge, Tennessee 37831-8201ABSTRACTThe goal of this research was to investigate the performanceof the Articulated Transporter and Manipulator System (ATMS)during various tasks relative to the choice of wrist/end-effectorconfiguration. "l"he approach taken was to generate computergraphics-aided three-dimensional interactive application (CATIA)system-based models of four wrist/end-effector combinations andconsider the volumetric reach of each of these configurations basedon the capacity of the ATMS. The results indicate that a simple,lightweight end-effector provides a greater volumetric reach, Thegreatest variation presented herein is -40% when comparing a7-degree-of-freedom (DOF) dexterous arm with a simple 3-DOFarm; however, the benefit of increasing volumetric reach by only40% by using a simple arm may be outweighed by the loss ofdexterity.INTRODUCTIONAs p,'u-tof the Nuclear Engineering (NE) program funded by the Departmentof Energy (DOE), a unique transporter system, called the Articulated Transporterand Manipulator System (ATMS), is being studied as a possible mobile platformfor manipulators intended for maintenance in nuclear facilities. The ATMS wasdesigned jointly by Odetics, Inc., (Anaheim, California) and The University ofFlorida, Department of Mechanical and Nuclem" Engineering (Gainsville, Florida).*Research sponsored by the Office of Nuclear Energy and the Office of TechnologySupport Programs, U.S. Department of Energy, undcr Contract No. DE-AC05-84OR214(X)with Martin MarictLa Energy Systcms..Managed t_,,,b.lartin Nlarielta t-nerey S v',tcm,;, Inc. l_r lhc I_J.S. l)cpartment _,1 l-_ncr_y.It is a unique teleoperated robot designed for remote maintenance and surveillancein a highly unstructured and possibly hazardous environment. Possibleenvironments include, but are not limited to, nuclear power plants, chemicalprocessing plants, and waste disposal and storage facilities. This study addressesthe choice of an end-effector system for the ATMS based solely uponconsideration of the total volumetric reach of each candidate.The ATMS, shown in FIG. 1, is a snake-like manipulator designed tonavigate in an unstructured and crowded environment. The ATMS is comprisedFIG. 1. Articulated Transporter and Manipulator System (ATMS).of 18 segments, each with a pitch joint on one end, a yaw joint on the other end,and two drive wheels. _ach segment is 0.292-m (11.5 in.) wide x 0.330-m(13 in.) high x 0.610-m (24 in.) long. The wheels are 0.178 m (7 in.) indiameter [ I]. Maneuvering the ATMS will be accomplished by an operator whoestablishes the direction and velocity of the front segments and subsequentsegme,ats follow one another. Horizontal and vertical navigation algorithms arepresently being studied that will allow the ATMS to move along a plane and tomove over and under obstacles. The ATMS is controlled through a 6..degree-of-freedom (DOl=) joystick. Each DOF of the joystick can be locked to reduce theDOFs.The most i,;nificant feature of the ATMS is its ability to cross horizontal..... gaps of several feet and move vertically over obstacles. The extent of thiscapability is determined by the choice of manipulator system used as the ATMSend-effector; however, this capability is unique and is far in excess of thecapabilities of traditional platforms employed in the nuclear industry (e.g., bipeds[2] and wheeled platforms [3,4]). If the ATMS is to perform any useful work, awrist/end-effector (or ama/end-effector) must be attached to the final link. Withthis basic concept, the final link or links become the slave manipulator of atelembot.The first design requirement guiding the selection of candidate wrist/end-effectors was to achieve modularity. The wrist/end-effector must be remotelydetachable from the final section of the ATMS. A second requirement was that thewrist/end-effector be an independent module so that different wrists/end-effectorscould be used with different tasks.When the ATMS reaches its work area, the final link or links may berequired to rise so that the manipulator(s) may access the component requiringmaintenance. In this event, the maximum number of links that can be lifteddetermines the overall reach of the ATMS/manipulator system and is a function Ofthe total mass of the manipulators. Computer graphics-aided three-dimensionalinteractive application (CATIA)-based models of several different wrist/end-effector combinations were constructed and used to geometrically determine thevolumetric reaches of each of the systems. The first three systems consideredwere1. Oak Ridge National Laboratory (ORNL)/Human Engineering Laboratory(HEL) 3-DOF wrist with parallel-jaw tong;2. dual arm, 6-DOF RM-10A [5,6]; and3. dual arm, gear-driven, electronically counterbalanced 7-DOFLaboratory Telerobotic Manipulator (LTM) [7].As in the design of any manipulator system, the choice of gripper/hand forthe ATMS is determined by the particular task environment envisioned for thesystem. ']?he ATMS will be able to navigate around, over, and through manyobstacles; however, the effectiveness of the ATMS in completing a particular taskis directly fled to the choice of wrist/end-effector mounted on the flu'st link of thechain. Each of these three candidate systems already listed uses a simple parallel-jaw-type gripper. Multiple-DOF hand designs exist today [8,9]. At least onedesign needed to consider the possibility of implementing a multiple-DOF hand.Thus, an additional candidate system was considered;4. ORNL/HEL 3-DOF wrist with ORNL-designed three-finger hand.APPROACHVolumetric reach is defined as the volume accessible by the manipulator. Itis a function of arm length and mass; joint design, placement, and limits; actuatordesign; and gripper/hand design. Volumetric reach is an important parameter indescribing any manipulator designed for work in an unstructured environment;however, the successful completion of most tasks requires the manipulator systemto maneuver around obstacles while accessing (in appropriate orientations) objectsconnected with the maintenance task. Other measures of manipulator performanceexist (e.g., a dynamic simulation); however, volumetric reach is a simple, basicwdy to compare manipulator systems.Volumetric reach was calculated for each system in the following manner.For the ATMS to rise, each link must be capable of lifting the mass of thesuccessive links as well as the end-effector. For static conditions, the sum of themoments about any of the ATMS links must be zero. This condition is illustratedin FIG. 2 for the ATMS with two links elevated.0.46m"_------_1Sum of the torques _ e om t ozo o\ , 1I- Ii SaN II _\ [ / 88N 133N W Nforendeffector[ Distributed [ [ (_ y[ Weight ][ 88NTypical Link u,, L ,,-LIFIG. 2. ATMS elevated for task.Note that the end-effector is connectedto the last complete link by an end-interfacelink having a weight of 133 N (30 Ibf) and a length of 0.46 m (18 in.). This staticsystemis solved for the numberof links capableof being elevated. The solution isgiven by Eq. (1):T=[N+ _ (i-I)]Wd+WE(Nd+0.23)+(Nd+0.46)WAr m , (l)i=lwhereT = Torque developed by the joint (Nm),W = Weight of each ATMS segment (88 N),WE = Weight of the end ATMS segment (133 N),WArm = Weight of the end-effector system (N),d = Length of the ATMS segments (0.6 m),'L = Total length lifted in Fig. 2 (m),N = Number of segments elevated.The maximum torques that can be developed by the ATMS pitch and yaw jointsare 4067 Nm (3000 ft-lbf) and 2034 Nm (1500 ft-lbf), respectively. Assumingthat the ATMS is pc_:itioned in a worst-case orientation, which would require theyaw joint to oppose gravity, then 2034 Nm is the limiting torque. The reachablevolume is determined by using both side and top views of the area enclosed by themanipulator system when the ATMS joints and the arm joints are moved throughtheir maximum ranges of motion.An important point to consider is that the working reach may be verydifferent from the volumetric reach. The working reach is defined as the volumein which the manipulator not only can reach a point but also can achieve a usableorientation. (A usable orientation will be determined by the task underconsideration.) The working reach is, therefore, a task characteristic as well as amanipulator characteristic. To simplify this analysis, it is assumed that theworking volume is equal to the volumetric rv.ach.RESULTSResults are presented for each of the wrist/end-effector combinations. The"a" part of each table has joint ranges of motion, and the "b" part has volumetricreach data. The volumetric reach data are presented for ali of the possibleconfigurations; that is, from "no segments elevated" (arms only) to the "maximumnumber of segments elevate&"ORNL/HEL Wrist with Parallel-Jaw ToneThe mass of the HEL wrist system, shown in FIG. 3, is 34 kg. Its motionranges are given in TABLE Ia. Solving Eq. (1) for d translates into four segmentsas lift,able. Volumetric reach data are summarized in TABLE Ib.FIG. 3. The HEL wrist.TABLE Ia. Joint ranges of motion TABLE Ib. Volumetric reach for thefor the HEL wrist. HEL wrist........ Motio_l No. of ATMS Volumetric ReachJoint Description Range segments elevated (m3)(rad) 0 0.761 Pitcla +n:/4 1 6.65-3_:/4 .... 2 29.14,, --2 Yaw +_:/2 - 3 80.93-n:/2 ' 4 171.883 Rol( +71:.......Source." ORNL Dwg. X3E 12651-00I_M-10A SystemThe mass of the RM-10A system, shown in FIG. 4, is 57 kg. Iis motionranges are given in TABLE IIa. Solving Eq. (1) for d translates into threesegments as liftable. Volumetric reach data are summarized in TABLE lib.FIG. 4. The RM-10A system.TABLE IIa. Joint ranges of motion TABLE lib. Volumetric reach for thefor the RM-10A system. RM-10A system.Motion - No. OfATMS Volumetric Reach, Joint Description Range segments elevated (m3)(rad) Oa) 5.69Oa) Arm Roll +n/2 ,-0- 1 21.95• 1 Shoulder +2n/3 2 ....... 66.77Pitch -2n/3 3 147.08.ml i2 Shoulder +2n/3 a)This is the arm only.Roll -2n/3- 3 Elbow Pitch +5n:/9-5n/94 Elbow Roll +5n/2-5n/25 Wrist Pitch +1 ln/36-11n/366 Wrist Roll +5n/2-5ft/2Source: White [6]a)Property of ATMS.¢_TM SystemThe mass of the LTM system, shown in FIG. 5, is ~100 kg. Iis motionranges are given in TABLE IIIa. Solving Eq. (1) for d translates into twosegments as liftable. Volumetric reach data are summarized in TABLE IIIb.FIG. 5. The LTM system.TABLE IIIa. Joint ranges of motion TABLE IIIb. Volumetric reach for thefor the LTM. LTM.- 191otion No.of ATMS Volumetric ReachJoint Description Range segments elevated (m 3),, (rad)Oa) _ Roll +7t/2 O a) 1"6.68-0, .... 1 - 51.341 Shoulder -_3_/4 2' 12"4.23Pitch -7t/4 a)This is the arm only.-- "2 ..... Shoulder +_: -Yaw -=3 -- Elbow Pitci:l +3_/4-_/4: ....4 Elbow Yaw +Tr-11;5 ' wrist Pitch +3_/a,-/1;/4- 6 Wr{st Yaw "+_- "'--71;.....7 Wrist Roll +_-IZSource: ORNL LTM CriticaJ" - ....Design Review, Dec. 8-9, 1987.a)Proper_y of ATMS.QRNL/IiEL Wrist with ORNL-desigrled threg-finger handThe mass of the HEL wrist with the ORNL-Jdesigned three-finger hand isassumed to be approximately the same as its mass with the parallel-jaw tong;therefore, the volumetric reach data are the same as TABLE Ib for the HEL wristwith parallel-jaw tong.DISCUSSIONThis study illustrated some general concepts about the selection of an end-effector for the ATMS. One important consideration is that the choice of end-effector is determined not only by the ATMS mechanical capabilities but also bythe task requirements and the environment in which the task will be performed.For example, the ORNL/HEL wrist is the lightest of the candidate systems, whichmeans that, mechanically, the ATMS can be more flexible with this end-effectorthan with the others. This end-effector is restricted, however, to tasks requiringlittle or no dexterity because it is only 3-DOF, as opposed to 6- or 7-DOF. It mustrely on the ATMS to provide the other DOFs. Note that even though more of theATMS links are liftabJ.e for the lighter end-effector, it should not be inferred thatthe lighter, fewer DOFs end-effectors have more dexterity than the heavier, 6- or 7-DOF end-effectors resulting from the added DOFs of the ATMS links. The ATMSlinks have large cross-sectional areas (0.096 m 2, or--1 ft2) and large volumes(0.059 m3, or-2 ft3); therefore, they are not as maneuverable as a link of anRM-10A or LTM arm (e.g., 0.023 m2, or 0.25 ft2 in cross section for the LTM).The added mobility of being able to lift additional links is helpful, but it is not asimportant as the dexterity gained by having additional arm segments. For moredetails, see Kress et al. [10].CONCLUSIONSThe work cited in this report is only a stnall portion of the basic design effortrequired to complete the design of a wrist/end-effector for the articulatedtransporter and manipulator system, lt does, however, compare and summarizethe basic properties of some candidate end-effector systems. Clearly, the choice ofend-effector depends upon the desired task; however, based on the results of thisstudy, the general conclusion can be made that a lightweight, redundantmanipulator with a dexterous hand seems best suited for the ATMS end-effector.Light weight and redundancy are usually conflicting requirements and is the casefor ali of the systems presented herein. The development of a lightweight, high-capacity, dexterous, multi-finger hand could extend the set of tasks performable bythe ATMS; however, the tasks would still be limited by the size and dexterity ofthe ATMS segments.REFERENCES1. R. N. Stauffer, "Researching Tomorrow's Robots", Robotics Today 2 (5), 27-35,(October 1987).2. Y. F. Zheng and J. Shen, "A Motion Scheme for a Biped Robot to Climb SlopingSurfaces", paper 2-1 in Proceedings of the ANS Third Topical Meeting on Robotics and RemoteSystems, Charleston, South Carolina, March 13-16, 1989.3. W.W. Manges, et al., "Development of the Hermies III Mobile Robot Research Testbed atOak Ridge National Laboratory", paper 2-3 in Proceedings of the ANS Third Topical Meeting onRobotics and Remote Systems, Ch_uleston, South Carolina, March 13-16, 1989.viJ4. R. F. Fogle and W. I. Lewis, "Multipurpose Robotic Vehicle Development at SavannahRiver", paper 2--4 in Proceedings of the ANS Third Topical Meeting on Robotics and RemoteSystems, Charleston, South Carolina, March 13-16, 1989.5. RM-10A Rpbolic Manioulator Descrbtion, REMOTEC 1987 Document No. 50032-001,available from REMOTEC, 114 Union Valley Road, Oak Ridge, Tennessee, (615) 483-0228.6. J. R. White, J. B. Coughlan, H. W. Harvey, and R. G. Upton, "RM-10A RoboticManipulator System", pp. 65--68 in Proceedings of the 36th Conference on Remote SystemsTechnology, Washington, D.C., 1988.7. J.N. Herndon, et al., "Telerobotic Manipulator Developments for Ground-Based SpaceResearch", paper 3-1 in Proceedings of the ANS Third Topical Meeting on Robotics and RemoteSystems, Charleston, South Carolina, March 13-16, 1989.8. S.C. Jacobsen, E. K. Inerson, D. F. Knutti, R. T. Johnson, and K. B_ Biggers, "Design ofthe Utah/MIT Dexterous Hand", pp. 1520--1532 in Proceedings of the IEEE InternationalConference on Robotics and Automation, San Francisco, California, April 7-10, lY86.9. K. Sadar0,oto, ed., Mechanical Hands Illustrated, (P.B. Co. Ltd., Tokyo 1982).10. R. L. Kress, S. M. Babcock, K. C. Bills, and W. R. Hamel, "Comparison of Possible End-Effectors for the Articulated Transporter and Manipulator System", Oak Ridge NationalLaboratory Technical Manuscript, ORNI./TM- 1I341 (in press, December 1990).| T

Volumetric reach comparison of possible end-effectors for the articulated transporter and manipulator system

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Volumetric reach comparison of possible end-effectors for the articulated transporter and manipulator system

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