Study on Appliction of Humn-Robot Collbortive System Using Hnd-Guiding in Production Line FUJII Msku : Mnger, Control & Communiction Technology Deprment, Products Development Center, Corporte Reserch & Development MURAKAMI Hiroki : Deputy Generl Mnger, Products Development Center, Corporte Reserch & Development SONEHARA Mitsuhru : Mnger, Robot Technology Deprtment, Products Development Center, Corporte Reserch & Development Power ssist devices nd utomted fcilities re pplied to the trnsporttion nd ssembly of hevy or lrge prts in production lines to improve efficiency, keep workers sfe nd reduce the number of workers. However, power ssist devices cnnot reduce the number of workers. Moreover, utomted fcilities hve to be equipped with dvnced sensing devices nd controls for positioning purposes nd judging when tsk is complete, nd then such fcilities my hmper utilition or mke the return on investment too smll. In this pper, to resolve such problems, we studied the ppliction of humn-industril robot coopertive system to production line. Sfety, operbility nd the ssistnce of humn skills were studied s they relte to hnd-guiding, in which humn opertes n industril robot directly nd they work collbortively. 1. Introduction In the mnufcturing industry, the reduction in lbor popultion due to the declining birthrte nd growing popultion of elderly people is hmpering the hnding down of the techniques of skilled workers. This is in turn reducing production qulity nd wekening corporte competitiveness due to incresing difficulties in cquiring qulified workers, even when fvorble mrket llows incresing production volumes. To mke up for the lbor shortge nd the lck of skills, utomted production hs been implemented in compnies producing products on lrge scle. However, in contrst to incresing utomtion in welding nd mterils hndling, ssembly work hs not been much utomted. It is difficult to utomticlly perform ssembly work tht require skilled lbor nd confirm the completion of work or the presence or bsence of defects. Also, utomtion requires dvnced control nd sensing technologies. Thus, one of the resons for sluggish dvncement in utomtion of ssembly work is tht these fctors frequently trigger brief shutdowns (suspension of device opertion not by mlfunction but by minor events), thereby reducing opertion rtes nd generting no significnt effects in return on investment for utomtion of production. To solve these issues, we proposed humn-robot collbortive opertion system clled hnd-guiding. (1), (2) In the hnd-guiding system, n industril robot tkes chrge of simple nd repetitive utomtic opertions such s holding workpiece, conveying it to n ssembly re, where ssembly nd instlltion re eecuted using n industril robot controlled by n opertor vi control device locted close to the end-effector of the robot. Hnd-guiding cn decrese the number of brief shutdowns nd sve the opertor such bothersome works in utomtion s detiled positioning nd confirmtion of the completion of works nd the presence or bsence of defects. In ddition, the industril robot cn be used s power ssist device to reduce the physicl burden for the opertor when hndling lrge or long components by supporting hevy weight nd mintining the position of component. There re devices developed for ctively performing power ssist nd work support. (3), (4) However, these devices re not industril robots for utomtic opertion nd require permnent control by opertors in the sme wy s power ssist devices do. One dvntge of estblishing the humn-robot collbortive opertion system using the industril robot is the vilbility, for some works, of utomtic opertion without n opertor. Sfety nd operbility re importnt fctors in the humn-robot collbortive opertion system. For sfety, the interntionl stndrds for sfety requirements for industril robots stipulte the prerequisites for humn-robot collbortive opertion, including the specific requirements for hnd-guiding. Complince with interntionl stndrds is lso required by Jpnese lws nd regultions relted to sfety. In response, bsed on our risk ssessment, we hve proposed systems for securing sfety, incorporting 1 seprtion of workspces for opertors nd industril robots, 2 relese of n interlock so n opertor cn ccess the control device of n industril robot during the collbortive opertion. (1), (2) The operbility is the performnce of the system necessry for enbling the opertor to control the industril robot t his discretion nd complete opertions. We lso proposed the following two methods for improving operbility of humn-robot collbortive opertion system. The one is letting the opertor to chnge the ptterns of robot 24 Vol. 49 No. 1 2016
commnd speeds in ccordnce with types of input devices nd ctuting vribles. (5) This is imed t enbling the opertor to relie opertions just s he intends. The other method is llowing the opertor to select motion es nd to switch robot s rottionl centers. This is imed t enbling the unskilled opertor to esily ccomplish tsks requiring (6), (7) skills. The following sections eplin the outcomes of our study on the subjects to be discussed nd designed when pplying the humn-robot collbortive opertion system to production lines for ssembling works involving lrge or long components. 2. Stndrds, ntionl sfety lws nd regultions nd collbortive opertion configurtion 2.1 Stndrds for humn-robot collbortive opertions The interntionl stndrds stipulting sfety requirements for industril robots re ISO 10218-1: 2011 (8) nd ISO 10218-2: 2011. (9) The former is for n individul robot nd the ltter for robot systems nd integrtion. To hrmonie Jpnese Industril Stndrds (JIS) with interntionl ones, JIS B 8433-1: 2015 (10) ws revised nd JIS B 8433-2: 2015 (11) ws published in Mrch 2015. The prerequisites for humn-robot collbortive opertion re stipulted in these stndrds. Tble 1 shows n outline of prerequisites for collbortive opertion in these stndrds. Of course, mesures to reduce risks to n llowble level must be implemented by conducting risk ssessment. 2.2 Sfety lws nd regultions for the humn-robot collbortive opertion Conventionlly, the sfety requirements for industril robots in Jpn were stipulted in Section 4, Cluse 150 of the Ordinnce on Industril Sfety nd Helth bsed on Cluse 20 of the Industril Sfety nd Helth Act. In the ordinnce, industril robots were defined by rted output of motors (80 W or more) nd the degrees of freedom of motion. The ordinnce lso required the provision of necessry mens, such s fences or enclosures to prevent possible risk of ccidentl contct between humns nd industril robots. Tble 1 Collbortive opertion requirement ccording to the stndrd Generl Collbortion configurtion Sfety-rted monitoring stop Hnd-guiding Speed nd seprtion monitoring Power nd force limiting Requirements (Summry) To provide visul indiction of collbortive opertion. To stisfy ny one of the requirements below. Requirements for robot behvior (suspension nd resumption of utomtic opertion) when humn eists in collbortive workspce. Requirements for the rrngement nd functions of control device required for hnd-guiding equipment; opertion speeds nd posture of robot; nd the indiction of collbortive workspce. Requirements for the speeds of robot nd distnce between humn nd the robot. Requirements for limiting power nd force by inherent design or control. (Note) The collbortive workspce mens workspce llowing humn to simultneously work with robot inside sfety protection spce of robot work cell. However, the ordinnce lcked cler correspondence with interntionl stndrds in terms of requirements for humnrobot collbortive opertion. In 2013, the interprettion of the ordinnce ws reviewed to clrify the correspondence between interntionl stndrds nd ntionl sfety lws nd regultions. Ntionl sfety lws nd regultions currently require sfety mesures for both robots nd robot systems s stipulted in interntionl stndrds. 2.3 Collbortive opertion configurtions Tble 2 shows collbortive opertion configurtion defined by interntionl stndrds. The sfety-rted monitoring stopping nd speed nd seprtion monitoring re configurtions for operting robots for keeping themselves from colliding with opertors. Power nd force limiting is configurtion of limiting robot power nd force so s ccidentl collisions pose only llowble risk to opertors. These collbortion configurtions llow opertors nd robots to shre workspce without physiclly dividing it. In other words, these configurtions mke humn-robot coeistent tsks prcticble. In contrst, hnd-guiding is configurtion for letting n opertor control n industril robot through control device locted close to the end-effector of the industril robot. Hnd-guiding represents collbortive opertions, where opertors re to guide by hnd the industril robots to hndle workpieces held by them. Such wys of performing tsks cn be clled, humn-robot coopertive tsks. Humn-robot coeistent tsk is not significntly different from tht of the conventionl industril robot system, ecept for the need for n electronic detection device (such s light curtin or mt to detect the presence of humns) which performs similr function to fence. In humn-robot coeistent work, industril robots nd opertors ech perform seprtely their own tsks. Conversely, in humn-robot coopertive tsk, industril robots nd opertors collbortively perform one tsk. For emple, when performing certin tsk to convey nd ssemble lrge or long components nd djust their positions without chnging postures, the opertor my use the industril robot s power ssist device nd llow it to perform only trnsltionl motions, restricting rottionl motions. Likewise, when performing tsk to djust postures, the opertor my select pproprite rottionl Collbortion configurtion Sfety-rted monitoring stop Hnd-guiding Speed nd seprtion monitoring Power nd force limiting Tble 2 Method of collbortive opertion Opertion method Opertion of robot is suspended when n opertor eists in collbortive workspce. The position nd speed of n end effector re instructed through n input device situted close to the end effector while n opertor ctivtes the enbling device situted close to n end effector. A robot opertes while the robot nd n opertor keep predetermined seprtion distnce. The opertion of the robot is suspended when they cnnot keep the seprtion distnce. The power nd force of robot re controlled or inherently limited until the risk of n opertor is reduced to n llowble level. Vol. 49 No. 1 2016 25
centers nd to llow the robot to perform only rottionl motions. The humn-robot collbortive opertion system provides the opertor, no mtter whether skilled or unskilled, with the skills needed to perform tsks such s ssembly, llowing him to esily eecute work requiring skills. In the humn-robot collbortive opertion system it is necessry to select n pproprite collbortion configurtion most suitble for the tsk be chieved, tking into considertion the chrcteristics of the configurtions. An pproprite collbortion configurtion must be selected fter pying due considertion to the sfety nd operbility, described below, to obtin benefits from it in the form of higher efficiency, opertion rte, relibility or lower costs thn those obtined from mnul opertion or conventionl utomted systems using industril robots. 3. Design of the humn-robot collbortive opertion system The following three items must be considered when designing humn-robot collbortive opertion system: (1) Collbortion configurtion (2) Sfety (3) Operbility These items re eplined in detil herefter ssuming ppliction to production line to convey nd ssemble lrge workpieces. 3.1 Collbortion configurtion This pper focuses on hnd-guiding design. As described in Section 2.3, hnd-guiding llows opertors to hndle lrge or long components, which cnnot be hndled mnully, by mking robots perform collbortive opertions s power ssist devices. Also, hnd-guiding llows the industril robots to perform utomtic opertions on their own, while the opertors re ble to eecute other tsks. Tht is, while hndguiding llows opertors to hndle workpieces held by robot just s generl power ssist devices do, it cn lso let the robot conduct other utomtic opertions by itself, thus contributing to lborsving. We consider this feture s the dvntge obtined from pplying humn-robot collbortive opertion systems to production lines tht hndle lrge or long components. In the cse of the coeistent tsks where opertors nd industril robots ech perform their respective tsks, however, they could not perform tsks tht cn be ccomplished only through their coopertion. Thus, hndguiding ws selected s the collbortion configurtion for this pper. (1), (2) Figure 1 shows the concept of the hnd-guiding system. The chrcteristic composition elements which distinguish the hnd-guiding system from generl systems using only industril robots re collbortive workspce, where robots nd opertors collbortively eecute tsks; n utomtic opertion workspce, where robots utomticlly eecute tsks without opertor entry; boundry to seprte the two spces using physicl or presence detection; nd hnd-guiding equipment for opertors to control the hnd-guiding system. The following sections eplin these composition elements in detil, from the viewpoint of sfety nd operbility. Hnd-guiding equipment Opertor Collbortive workspce Indiction light Automtic opertion workspce 3.2 Sfety Bsed on JIS B 8433-1: 2015 nd JIS B 8433-2: 2015, the hnd-guiding system must stisfy the following sfety requirements: (1) Implementtion of risk ssessment (2) Provision of visul indiction of collbortive opertion when in progress (3) Arrngement of hnd-guiding equipment (including n emergency stop nd enbling device which conform to JIS B 8433-1: 2015) locted close to the end-effector (4) Avilbility of cler visul confirmtion by the opertor of the entire collbortive workspce (5) Provision of robots, protection nd presence detection devices, nd sfety-rted monitoring speed function which conforms to JIS B 8433-1: 2015 nd JIS B 8433-2: 2015 As required in (1) bove, risk ssessment ws implemented nd, bsed on the ssessment results, the concept ws formulted s shown in Fig. 1, nd n eperimentl system (1), (2) designed s shown in Fig. 2. Conforming to requirement (2), n indiction light is situted t position visible to n opertor s shown in Fig. 1. Also, conforming to requirement (3), the hnd-guiding equipment comprising the 3-position enbling switch, emergency stop switch nd the input device for position nd speed commnds is locted close to the end-effector s shown in Fig. 3. Indiction lights Opertion object workpiece Spce boundry Industril robot Fig. 1 Concept of hnd-guiding system Spce boundry (n opening nd light curtin) (Note) Robot Fence Opertion object workpiece : Collbortive workspce : Automtic opertion workspce Fig. 2 View of eperimentl system 26 Vol. 49 No. 1 2016
End-effector Emergency stop switch 3-position enbling device Fig. 3 Hnd-guiding equipment Input device End-effector control device Aginst the possible risk tht n opertor using only one hnd my get the other free hnd stuck in the robot or workpiece, the enbling device nd the input device re rrnged for respective opertion using either hnd, with sufficient distnce between to prevent the opertor from operting both using one hnd. The input device is joystick type, s shown in Fig. 3, where n inclintion ngle of the joystick becomes sensor vlue input for the robot. Or, the other input device is force sensor tht inputs pplied force to stick used in plce of the joystick, s eplined in lter section. To meet the requirement of (4), fence ws used to clerly mrk the border between the collbortive workspce nd the utomtic opertion workspce s shown in Fig. 2. The fence ws lso used to prevent persons other thn opertors from entering the spces. A prtition nd working tble were instlled to prevent opertors from entering the utomtic opertion workspce. A sfety sensor ( light curtin) ws lso instlled to stop the industril robot when ny prt of n opertor s body enters the utomtic opertion workspce through n opening or the industril robot enters the collbortive workspce during non-collbortive-opertion mode. Also, coeistent opertions s eplined in Section 3.1 cn be combined with the collbortive opertions. For emple, it is possible not to physiclly seprte the collbortive workspce from the utomtic opertion workspce. When this is the cse, fter clerly demrcting the spces by colors pinted on the floor, etc., hnd-guiding cn be performed within the collbortive workspce during collbortive opertion mode, provided tht industril robot opertions re suspended if the distnce between opertor nd industril robot be smller thn the pre-determined cceptble distnce when he enters the collbortive workspce while the industril robot performs its utomtic opertions. The industril robot, control device nd other detection devices re designed to stisfy the requirement of (5). Also, opertion speeds, industril robot movements during collbortive opertion mode, switching control between utomtic opertion nd collbortive opertion nd rrnging respective compositionl elements hve been determined, bsed on risk ssessment results. The mesures eplined in this pper re not sufficient to reduce ll risks to llowble levels nd cnnot be pplied s pproprite to ll systems. It should be noted tht suitble mesures need to be studied by ppropritely implementing risk ssessment of the specific system structures nd usge of the ctul system to be designed. 3.3 Operbility The operbility of the collbortive opertion system in humn-robot coeistent tsks includes such subjects s the switching between utomtic nd collbortive opertion nd return performnce of the industril robot fter it is suspended due to collisions with the opertor or some lrge impcts. Also, the operbility of hnd-guiding includes how to send commnds on positions nd speeds to the industril robot. With well-designed methods, opertions cn be completed speedily with high success rte. The idel operbility is to control the industril robot to the opertor s stisfction, s if he were holding workpieces with his own hnds. The importnt points to consider for chieving such idel operbility re: (1) Types of reltions between ctuting vribles of input devices nd robot velocity commnd vlues (2) Types of input devices Also, the following items re skill support mechnisms for llowing difficult tsks requiring skill to be esily eecuted by supporting unskilled opertors by humn-robot collbortive opertion systems: (3) Limits on degree of freedom of opertion nd TCP (Tool Center Point) selection (4) Conversion of tsk coordinte systems 3.3.1 Reltionships between ctuting vribles of input devices nd robot velocity commnd vlues Preferbly, robots move fst with brod mnipultion when conveying workpieces in direction wy from the opertor, moving slowly nd finely when performing ssembly tsks, etc. Thus, it is importnt wht kind of robot velocity commnd vlue is clculted from the ctuting vrible of the input device. Figure 4 illustrtes two types of reltionships between ctuting vribles of input devices nd robot velocity commnd vlues: one is for clculting the velocity of commnd vlues in proportion to ctuting vribles (Fig. 4-()); the other is for clculting the velocity of commnd vlues in proportion to the squre or cube of ctuting vribles () Liner reltion v = K v K 1 0 K Ded one 1 (b) Nonliner reltion v = K 3 v K 1 0 (Note) K : gin : ctuting vrible (the mimum speed of K between -1 nd 1) v : velocity commnd vlue K 1 v= K Fig. 4 The reltionship between input device nd robot velocity commnd Vol. 49 No. 1 2016 27
(Fig. 4-(b)). As shown in Fig. 4-(), the liner reltion contins ded one to prevent minute velocity commnd vlue from being clculted when the ctuting vrible is ner ero. The eperiment on these clcultion methods reveled tht velocity commnd vlues in reltion to the squre of ctuting vribles produce the shortest time to eecute opertions. (5) However, such effective reltions my chnge depending on the reltive lengths of durtion of fine nd brod mnipultion in hnd-guiding opertions. 3.3.2 Types of input devices (Fig. 5) There re two types of input devices: the joystick types which output inclintion ngles nd the force sensor types which output force nd moment of force, cting on the joystick. Input devices using force sensors re considered to give the opertor the feeling of nturl control s, in generl, people pply forces to objects when holding nd conveying them. After some eperiments on the two types of input devices, opertions using force sensors cpble of 6-is input produced the shortest opertion time. (5) By contrst, in opertions to djust posture by rottionl motion, the force sensor cused more frequent retrying thn joystick. As mentioned bove, force sensors llow opertions to be performed intuitively, but it remins difficult to pply moment of force only in specific direction through lever control. This, we think, is becuse, with the force sensors, the posture of robot rm will unintentionlly chnge to nother direction. Robot rm tip () Joystick (triil type) y, c (b) Force sensor (6-is type) 3.3.3 Limittion on degree of freedom of opertion nd selection of TCP It ws discovered tht force sensors my cuse rottionl movement in unintended directions. In this respect, the hnd-guiding cn limit degree of freedom of opertion by intentionlly preventing the robot from moving in undesired directions. Also, hnd-guiding cn perform opertions more in ccord with the intentions of opertors by chnging the TCP, which is to be set s the center of rottionl motion, ccording to the type of opertion. Moreover, hnd-guiding cn help with tsks requiring skills by chnging the degree of freedom of movement nd switching rottionl centers ccording to the content (phses) of opertion. Hnd-guiding used in this wy is lso clled opertion guidnce. Figure 6 shows n emple of n opertion to ssemble pnel, in which n object workpiece hs holes t four corners. The limittion on degree of freedom of opertion nd TCP selection for respective opertion phses re decided for this ssembling opertion. The emple of opertion guidnce for pnel ssembly is shown in Tble 3. In phse 1, only trnsltionl motion is llowed to move the pnel. In phse 2, 2-il rottionl motion is llowed to lign the pnel prllel to the object onto which the pnel is fitted. In phse 4 of ligning ll the positions of four holes, TCP is shifted to ny one of the holes tht the opertor cn esily see, with the degree of freedom limited to uniil rottion. By n ssembly performnce eperiment, it ws confirmed tht the time required to ssemble the pnel cn be shortened Pnel End-effector b y, b c c y b Object into which pnel is fit Industril robot Control device (Note) : Rottionl direction round is b : Rottionl direction round y is c : Rottionl direction round is Fig. 5 Input device Bolts (t 4 corners) Holes (t 4 corners) Fig. 6 Emple of pnel ssembly Opertion Tble 3 Emple of opertion guidnce for pnel ssembly Phse 1 2 3 4 5 To convey pnel to plce close to n is. To lign the pnel prllel to the object into which the pnel is fit. To lign hole on the pnel with the is. To rotte the pnel round the is to lign the positions of other holes with corresponding es. To fit the pnel. Eplntory digrm Necessry degree of freedom Tri-il trnsltion Biil rottion Biil trnsltion Uniil rottion Uniil trnsltion (Note) The opertion is eecuted from Phse 1 to Phse 5 in series. 28 Vol. 49 No. 1 2016
y Tsk coordinte system 2 Conveyor line Fig. 7 Skew of conveyor line Tsk coordinte system 1 Skew y by using opertion guidnce. (6) It is difficult tsk to djust lrge pnel with si degree of positionl nd posturl freedom by confirming the positionl reltions between the four corner holes nd their corresponding bolts. However, combintion of hnd-guiding with limits on degree of freedom of opertion nd TCP selection cn esily relie such difficult tsk in mnner tht supplements n opertor s skill deficiency. 3.3.4 Conversion of tsk coordinte systems A tsk coordinte system my be chnged if position t which to plce the opertion object workpiece or to perform the ssembling opertion differs from opertion to opertion. For emple, there re cses of opertions conducted on conveyer lines instlled flt nd stright (idelly) on drwing but in fct re instlled skew becuse of imperfect fltness of the ground on which they re plced. Figure 7 shows n emple of skewed conveyer line. In such cses, opertions my be performed by switching between the tsk coordinte systems preset for different opertionl positions. Thus, the opertor cn perform trnsltion opertions using hnd-guiding without regrd to skews on production line s djustments of robot moving direction or posture cn be utomticlly performed. After the eperiment on the effect of tsk coordinte system conversion, we confirmed tht opertion hours were shortened by eliminting time required for djusting posture during hnd-guiding. (7) With generl power ssist devices, opertors need to cquire skills to perform tsks by consciously nd intentionlly djusting device postures ccording to the skew on production line. By contrst, hnd-guiding llows opertors without skills to perform tsks using industril robots nd switching tsk coordinte systems. Therefore, in this sense too, hnd-guiding would serve s compensting mesure for n opertor s skill deficiency. 4. Conclusion In order to pply the humn-robot collbortive opertion system to production line, this pper studied methods to improve sfety nd operbility of the system clled hndguiding. To improve sfety of humn-robot collbortive opertion systems their design needs to be done ccording to the results of risk ssessment nd in complince with interntionl stndrds. To improve operbility, this pper introduced types of input devices nd techniques such s limiting degree of freedom of opertion nd switching TCPs nd tsk coordinte systems. Humn-robot collbortive opertion systems, by combining these techniques, llow opertors to eert control t their own discretion, nd esily perform tsks requiring skill by supplying them with needed skills. As humn-robot collbortive opertion systems llow wide rnge of people, including women nd the elderly, perform tsks requiring skills, these systems would contribute to productivity increses of society s whole. Although ntionl lws nd regultions re revised, few humn-robot collbortive opertion systems hve been introduced. We will continue our efforts to pply the humnrobot collbortive opertion systems to production systems within nd outside our compny nd to further improve sfety nd operbility s promising kind of systems for enhncing the vlue of production lines. REFERENCES (1) M. Fujii, D. Shiokt, H. Murkmi nd M. Sonehr : Proposl of Sfety System for Humn nd Industril Robot Collbortive Working The Robotics nd Mechtronics Conference 2008 (2008. 6) 2A1-A21 (2) M. Fujii, Y. Ogur, H. Murkmi nd M. Sonehr : Proposl of Humn-Robot Collbortive System Using Hnd Guiding Journl of IHI Technologies Vol. 51 No. 2 (2011. 3) pp. 18-24 (3) H. Konosu, I. Arki nd Y. Ymd : Prcticl Development of Skill-Assist Journl of Robotics Society of Jpn Vol. 22 No. 4 (2004. 5) pp. 508-514 (4) H. Murym, K. Fujiwr, N. Tkesue, K. Mtsumoto, H. Konosu nd H. 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