A New Type of AODF Based on an Imitation of the Weft Insertion of a Rapier Loom

electronics

Article A New Type of AODF Based on an Imitation of the Weft Insertion of a Rapier Loom

Shimin Wei, Zheng Yang * , Lei Guo and Yuan Song School of Automation, Beijing University of Posts and Telecommunications, No 10, Xitucheng Road, Haidian District, Beijing 100876, China; [email protected] (S.W.); [email protected] (L.G.); [email protected] (Y.S.) * Correspondence: [email protected]; Tel.: +86-186-1122-2214

Received: 1 November 2018; Accepted: 17 January 2019; Published: 1 February 2019

Abstract: The main distribution frame (MDF) is an important component between the user and the operator that supplies a telecommunication service and is the only layer in the seven-layer communication architecture that is not fully automated. In this paper, a cross-connect method for simulating the rapier picking of a rapier loom (shuttleless loom) is proposed to imitate the shedding and the picking action to achieve quick switching. Using the designed “shedding device” and “picking device”, a model prototype of the automatic optical distribution frame (AODF) was constructed and tested for veriﬁcation.

Keywords: automatic optical distribution frame (AODF); cross-connect; robot; rapier loom; shedding; picking; Petri net

1. Introduction The main distribution frame (MDF) is an important component between external equipment and the user of a communication network supplied by the operator. The MDF contains a large number of physical connections and is the only layer in a seven-layer communication architecture that is not fully automated [1–4]. Traditionally, cross-connections on patch panels are manually installed, but manual operation is complicated and time-consuming and the possibility of errors exists. Because a large number of optical fibers are used in communication networks, operators are required to offer high-level reliability services to customers, quickly resolve line failures, and reduce the costs of operation and maintenance. Service providers have strict requirements for the automatic optical distribution frame (AODF) [5–10]. In communications, the AODF is complicated, and although it was proposed quite early on, few studies have been conducted on its automation [11–16]. Although commercially available AODF products began to appear on the market in the late 2000s, Fiberzone-Networks [12], Telescent [13], Teliswitch Solutions [14], and Huawei [15] provide AODF products, but in small quantities because the current robotic approaches have limitations. Due to the difficulties associated with robotic systems, many organizations use nonrobotic structures such as microelectromechanical systems (MEMS), beam steering, the asymmetrical approach, and locking optical coupling technology [17,18]. Fibers are present in the MDF and in looms. A loom is a device that interlaces two sets of yarns (i.e., warp and weft) to produce fabric [19–23]. Based on the weft insertion device, weaving machines are divided into shuttle looms and shuttleless looms. The three most popular weaving machines are the jet, rapier, and projectile types. The rapier loom uses a flexible or rigid rapier as a weft insertion device to achieve insertion of the weft, and this loom is known for its reliability and performance [24–27]. Previously [28], we proposed a “higher always on top” nonwinding cross-connect method based on the spatial relationship of noncoplanar lines and proposed the analogy of a rapid switching method

Electronics 2019, 8, 157; doi:10.3390/electronics8020157 www.mdpi.com/journal/electronics Electronics 2019, 8, 157 2 of 18 that imitates the picking of a shuttle. The design of the actuator is complicated due to the small gap between the fibers in the MDF. Imitation of the initial shedding of the loom and subsequent picking is better than the simple imitation of the picking of a shuttle, and the requirements for the actuator are not strict. The relationship between warp and weft threads in a textile from a loom is similar to the noncoplanar lines’ spatial relationship of a one-dimensional array of input lines and a one-dimensional array of output lines using a line-match line. In this paper, we propose a cross-connect method that imitates the rapier loom using rapier picking. Imitation of the shedding action and the picking action are used to realize quick switching. The shedding action is achieved by the shedding mechanism, which is the same as forming a shed in a loom. Enlarging the distance between the fibers is beneficial for the robot switching. Picking acts to insert the weft into the shed so that the warp and weft are interlaced. We regarded the target patch cord to be connected as a weft and the switching operation as being similar to the weft insertion, and the robot removes the fiber from the current port and moves it along a specific path (like the shed) to the target port. We designed a “shedding device” and a “picking device”, used Petri nets to characterize the workflow of the entire system, and built the virtual prototype and experimental model for verification [29–35].

2. Cross-Connect Method The textile industry is a traditional stalwart throughout world industry history, and this technology dates back thousands of years. Silk fabrics and ramie fabrics unearthed in Zhejiang Province, China, have a history longer than 4700 years. The loom is a device that interlaces two sets of yarns to produce a fabric, and the first loom was a shuttle loom. The weft insertion device is the most important component of the weaving machine, and its type is usually the basis for classification of the loom. According to the weft insertion method, the loom can be divided into two categories. The traditional shuttle is used as a weft inserter, and this type of loom is known as a shuttle loom. The other type includes a series of looms that were invented at the beginning of the 20th century. The weaving machine that introduces the weft yarn from a fixed bobbin into the shed using a high-speed jet, or a light weft inserter, is known as the shuttleless loom because it does not use the traditional shuttle, replacing it with air, projectiles, rapiers, and water as the weft insertion media. The rapier loom is the most widely used shuttleless loom and is high-speed, highly automated, and produces high-quality products. The weft insertion method of the shuttleless loom varies widely, can be adapted to the weft insertion of various types of yarns, and offers obvious advantages in multicolor weft weaving. The rapier loom uses a flexible or rigid rapier as a weft insertion device to insert the weft and is known for its reliability and performance. The rapier loom is the most commonly used configuration in shuttleless looms. The rapier head picks up the filling yarn and takes it through the shed. After reaching the destination, the empty rapier head returns to pick up the next weft to complete a cycle. Two types of rapier looms exist: (1) Single rapier looms use a single rigid rapier loom that enters the shed from one side, picks up the tip of the filling yarn on the other side, and passes it through the loom as it shrinks, as shown in Figure1. (2) Double rapier looms are operated by a giver head taking the filling yarn from the yarn storage from one side of the weaving machine, carrying it to the centre of the machine, and transferring it to the taker. The taker retracts and brings the filling yarn to the other side. Similar to a single rapier loom, only half of the rapier movements are used in weft insertion. The double rapier configuration can be rigid or flexible. In a flexible rapier loom, the rapier loom has a ribbon structure that can be wrapped around the drum, thus conserving space and allowing a narrower machine width. Double flexible rapier looms are more common than rigid rapier looms. Electronics 2019, 8, 157 3 of 18 Electronics 2018, 7, x FOR PEER REVIEW 3 of 18

FigureFigure 1. 1. WeavingWeaving process diagram fo forr a single rapier loom. The warp yarn is sent from the weaver’s beam by the feeding mechanism, passes through the The warp yarn is sent from the weaver’s beam by the feeding mechanism, passes through the back rest and the drop wires to the harness, penetrates into the heddle eye of the harness according to back rest and the drop wires to the harness, penetrates into the heddle eye of the harness according a certain law, and passes through the reed that holds the warps at uniform spacing. This element is to a certain law, and passes through the reed that holds the warps at uniform spacing. This element designed to beat up the weft thread. The harness is controlled by the shedding mechanism to separate is designed to beat up the weft thread. The harness is controlled by the shedding mechanism to the warp threads into two warp layers to form a shed. The rapier enters the shed from one side, picks separate the warp threads into two warp layers to form a shed. The rapier enters the shed from one up the tip of the weft to the other side of the weaving machine, and retracts to complete the weft side, picks up the tip of the weft to the other side of the weaving machine, and retracts to complete insertion. The shed is closed, and during the closing process, the reed pushes the weft yarn to the fell the weft insertion. The shed is closed, and during the closing process, the reed pushes the weft yarn for beat-up to complete a weaving cycle. In the next weaving cycle, the harness exchange position to the fell for beat-up to complete a weaving cycle. In the next weaving cycle, the harness exchange interlaces the upper and lower warp yarns to form a new shed. position interlaces the upper and lower warp yarns to form a new shed. It can be observed from the process of fabric formation that the lifting rule of the harness It can be observed from the process of fabric formation that the lifting rule of the harness determines the interlacing law of the fabric. In the fabric, all the raised warp yarns are located determines the interlacing law of the fabric. In the fabric, all the raised warp yarns are located above above the weft yarn, and all the warp yarns that are not lifted lie under the weft yarn. To interlace the weft yarn, and all the warp yarns that are not lifted lie under the weft yarn. To interlace the warp the warp and weft threads, the loom must conduct the following important operations: (1) Shedding and weft threads, the loom must conduct the following important operations: (1) Shedding involves involves the separation of the warps into two sheets, one of which is lifted and the other lowered to the separation of the warps into two sheets, one of which is lifted and the other lowered to form the form the shed for the weft insertion. (2) Picking involves the insertion of the weft yarn through the shed for the weft insertion. (2) Picking involves the insertion of the weft yarn through the shed. (3) shed. (3) Beat-up involves the pushing of the inserted weft into the fabric fell. (4) Wrap let-off includes Beat-up involves the pushing of the inserted weft into the fabric fell. (4) Wrap let-off includes the the delivery of the warp to the formation zone at the required rate and at a suitable constant tension by delivery of the warp to the formation zone at the required rate and at a suitable constant tension by unwinding it from the weaver’s beam. (5) Cloth take-up involves the movement of fabric from the unwinding it from the weaver’s beam. (5) Cloth take-up involves the movement of fabric from the formation zone at a constant rate that ensures the required pick spacing and winding of the fabric onto formation zone at a constant rate that ensures the required pick spacing and winding of the fabric a cloth roller. onto a cloth roller. In our previous study [28], we found that the separated warp threads and the weft thread that In our previous study [28], we found that the separated warp threads and the weft thread that is inserted into the shed are noncoplanar lines, and the process of switching is similar to the picking is inserted into the shed are noncoplanar lines, and the process of switching is similar to the picking process. When the cross-connect is manually performed, the connector is pulled by the fingers and process. When the cross-connect is manually performed, the connector is pulled by the fingers and held by the fingers to pass through the gap between the fibers before it is inserted into the target port. held by the fingers to pass through the gap between the fibers before it is inserted into the target port. When the hand passes, the shedding action is automatically completed, and the distance between When the hand passes, the shedding action is automatically completed, and the distance between the the fibers is enlarged so that human fingers can hold the connector through (Figure2). Based on the fibers is enlarged so that human fingers can hold the connector through (Figure 2). Based on the automatic opening of the hand during the cross-connect process, or use of another hand to expand automatic opening of the hand during the cross-connect process, or use of another hand to expand the gap between the fibers, we propose using the cross-connect method of imitating the rapier weft the gap between the fibers, we propose using the cross-connect method of imitating the rapier weft insertion of the rapier loom. The connected fiber patch cords are treated as warps, and the target insertion of the rapier loom. The connected fiber patch cords are treated as warps, and the target fiber fiber to be connected is viewed as a weft. The shedding operation is performed using a “shedding to be connected is viewed as a weft. The shedding operation is performed using a “shedding mechanism” to expand the distance between the fibers, and the rapier is applied for weft insertion, mechanism” to expand the distance between the fibers, and the rapier is applied for weft insertion, i.e., the robot is used to pull out the target fiber from the current port and insert it into the target port. i.e., the robot is used to pull out the target fiber from the current port and insert it into the target port. The robot exits to complete the “picking” operation, and the shedding mechanism closes the shed to The robot exits to complete the “picking” operation, and the shedding mechanism closes the shed to complete the switching process. complete the switching process.

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Figure 2. Manual switching process. Figure 2. Manual switching process. Figure 2. Manual switching process. 3. Design of the Shedding Mechanism 3. Design of the Shedding Mechanism 3. DesignThe shedding of the Shedding action is Mechanism achieved by a shedding mechanism that causes the warp yarns to layer The shedding action is achieved by a shedding mechanism that causes the warp yarns to layer up andThe down shedding to form action a shedis achieved sufficient by afor shedding the rapier mechanism to pass through. that causes As shownthe warp in yarnsFigure to 1, layer two up and down to formform aa shedshed sufﬁcientsufficient forfor thethe rapierrapier toto passpass through.through. As shown in Figure1 1,, twotwo upharnesses and down were to used form to a achieve shed sufficient the shedding for the action rapier. The to warppass through.yarn is divided As shown into upperin Figure and 1, lower two harnesses were used to achieve the shedding action.action. The warp yarn is divided into upper and lower harnesseslayers with were the usedlifting to movement achieve the of shedding the harness, action and. The viewed warp from yarn theis divided side, a intoquadrilateral upper and channel lower layers with the liftinglifting movementmovement of thethe harness,harness, and viewed from the side,side, aa quadrilateralquadrilateral channelchannel layersABDC with is formed the lifting in the movement middle of theof the two harness, layers of and warp viewed yarns from (Figure the 3), side, which a quadrilateral is the shed. Thechannel four ABDC is formed in the middle of the two layers of warp yarns (Figure3 3),), whichwhich is is thethe shed.shed. TheThe fourfour ABDCvertices is offormed the quadrilateral in the middle ABCD of the are two the layers fell, ofth ewarp upper yarns harness, (Figure the 3), lower which harness, is the shed. and Thethe dropfour vertices of the quadrilateralquadrilateral ABCD are the fell, thethe upper harness, the lower harness, and the drop verticeswires, respectively. of the quadrilateral The front ABCD half of arethe theshed fell, AB thC eis upper the working harness, component the lower of harness, the shed, and from the which drop wires, respectively.respectively. TheThe frontfront halfhalf ofof thethe shedshed ABCABC is the working component of the shed, from which wires,the rapier respectively. passes and The fills front in the half weft of the yarn shed to ABcompleteC is the the working warp andcomponent weft interlacing. of the shed, from which the rapier passespasses andand ﬁllsfills inin thethe weftweft yarnyarn toto completecomplete thethe warpwarp andand weftweft interlacing.interlacing. the rapier passes and fills in the weft yarn to complete the warp and weft interlacing.

Figure 3. Schematic diagram of the shed. Figure 3. Schematic diagram of the shed. Figure 3. Schematic diagram of the shed. TheThe harnessharness isis composedcomposed ofof thethe outerouter framesframes andand manymany heddles.heddles. With a holehole inin thethe middlemiddle inin aa The harness is composed of the outer frames and many heddles. With a hole in the middle in a side-by-sideside-by-side manner, eacheach warpwarp threadthread passespasses throughthrough the heddle eye of the corresponding heddle. side-by-sideThe harness manner, is composed each warp of threadthe outer passes frames through and many the heddle heddles. eye With of the a holecorresponding in the middle heddle. in a EachEach fiberfiber onon thethe MDF corresponds toto aa fiberfiber storagestorage containercontainer thatthat suppliessupplies elasticelastic tension,tension, andand each side-by-sideEach fiber on manner, the MDF each corresponds warp thread to a passesfiber storage through container the heddle that eyesupplies of the elastic corresponding tension, and heddle. each fiberfiber storagestorage containercontainer cancan bebe treatedtreated asas aa heddle.heddle. The fiberfiber storage containers arranged togethertogether cancan Eachfiber storagefiber on containerthe MDF correspondscan be treated to as a fibera heddle. storage The container fiber storage that suppliescontainers elastic arranged tension, together and each can bebe viewedviewed asas aa harness.harness. Figure4 4 shows shows aa modelmodel ofof aa sequential sequential one-dimensionalone-dimensional (1-D)(1-D) toto 1-D1-D form,form, fiberbe viewed storage as container a harness. can Figure be treated 4 shows as aa heddle.model ofThe a sequentialfiber storage one-dimensional containers arranged (1-D) togetherto 1-D form, can andand thethe dotteddotted boxbox onon thethe rightright sideside ofof thethe figurefigure indicatesindicates thethe fiberfiber storagestorage container,container, whichwhich cancan bebe beand viewed the dotted as a boxharness. on the Figure right 4side shows of the a model figure of indicates a sequential the fiber one-dimensional storage container, (1-D) which to 1-D can form, be treatedtreated asas aa heddleheddle eyeeye thatthat passespasses throughthrough thethe warp.warp. andtreated the asdotted a heddle box eyeon the that right passes side through of the figure the warp. indicates the fiber storage container, which can be treated as a heddle eye that passes through the warp.

Figure 4.4. Model of a sequence of a one-dimensional (1-D)(1-D) toto 1-D1-D form.form. Figure 4. Model of a sequence of a one-dimensional (1-D) to 1-D form. Figure 4. Model of a sequence of a one-dimensional (1-D) to 1-D form.

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We previously [28] described the fibers in the 1-D to 1-D form, which are constructed in a noncoplanar relationship and are perpendicular to each other, and each fiber moves in its own layer. As shown in Figure3, if the port is established on the X-axis of the illustrated coordinate system, it is easy to determine the plane of any layer where the fiber is located, such as the plane where fiber f is located: z f z = y (1) y f where y f is the Y coordinate of point f and z f is the Z coordinate of point f. The number of harnesses on the loom and the different lifting sequences of the harness form the organization of different fabrics, such as a plain weave or a twill weave. The number of harnesses is determined by the texture, and when the texture is determined, the number of harnesses is determined. The fiber patch cords that operate on the MDF are random and not known in advance, but only one of the optical fiber patch cords is operated during the switching operation. To facilitate the operation, the area where the shedding operation is enlarged is a triangular area located on both sides of the target optical fiber patch cord. At the same time, the texture formed by the cross-connect is a “nonwinding” texture, and the two harnesses meet the requirements of the cross-connect. As shown in Figure4, if the target fiber for the switching operation is fiber f, the shed is a triangular prism with eFg as a cross section as shown in Figure4, the weaving fell is the X-axis, and the corresponding harnesses are the upper harness formed by the upper fiber storage containers a–e, and the lower harness is formed by the lower fiber storage containers g–k. If the target fiber is fiber c, the harnesses are a–b and d–k, respectively. In the loom, the harness is located on the rear side of the effective shed, on the 1-D to 1-D form MDF. The harness is also located on the rear side of the effective shed, and the formed shed contains only the effective portion. The width of the harness in the loom is the width of the weaving fell, which horizontally covers the width of all of the warp threads. On the 1-D to 1-D form MDF, the fiber storage containers and the adapter ports side are perpendicular to each other, i.e., the harness and the fell are vertical, and the position is set according to the needs of the fiber patch cords. Preferably, there are two forms, and the fiber sequence of Figure4 is projected onto the plane XOY, as shown in Figure5. In the X-axis direction, the position of the fiber storage containers can be set in the middle of the adapter port side (Figure5a). It can also be set on one side of the adapter port side (Figure5b). When the rapier is used in weft insertion, the weft thread must be moved from one side of the shed to the other. When the fiber is cross-connected, the rapier robot must also be able to move the fiber from one end of the adapter ports side to the other, i.e., move from port A to port K. R1 and R2 in Figure5 represent the rapier robot in two cases, as can be observed from the figure. It is easy to know:

1 1 R = R = AK (2) 1 2 2 4 where R1 is the length of the rapier robot when the ﬁber storage containers are in the middle, R2 is the length when the ﬁber storage containers are on one side, and AK is the length from port A to port K. ElectronicsElectronics 20182019,, 78,, x 157 FOR PEER REVIEW 66 of of 18 18 Electronics 2018, 7, x FOR PEER REVIEW 6 of 18

Figure 5. Two positions of the fiber storage containers and the adapters in the X-axis direction. (a) FigureFigure 5.5.Two Two positions positions of of the the fiber fiber storage storage containers containers and and the adaptersthe adapters in the in X-axis the X-axis direction. direction. (a) Fiber (a) Fiber storage containers in the middle; (b) fiber storage containers on one side. The following parts storageFiber storage containers containers in the in middle; the middle; (b) fiber (b) storagefiber storage containers containers on one on side. one side. The followingThe following parts parts are are labeled: (R1) the length of the rapier robot, (R2) the length of the rapier robot. labeled:are labeled: (R1) (R the1) lengththe length of the of rapierthe rapier robot, robot, (R2) (R the2) the length length of the of rapierthe rapier robot. robot. For the switching operation, the rapier robot moves at the shed and the adapter ports are located ForFor thethe switchingswitching operation,operation, thethe rapierrapier robotrobot movesmoves atat thethe shedshed andand thethe adapteradapter portsports areare locatedlocated on the fell, i.e., the X-axis, which is also the position the actuator of the robot must reach. As shown onon thethe fell,fell, i.e.,i.e., thethe X-axis,X-axis, whichwhich isis alsoalso thethe positionposition thethe actuatoractuator ofof thethe robotrobot mustmust reach.reach. AsAs shownshown in Figure 6, the dotted line box shows a rapier robot for switching performance, and in the Z-axis inin FigureFigure6 ,6, the the dotted dotted line line box box shows shows a a rapier rapier robot robot for for switching switching performance, performance, and and in in the the Z-axis Z-axis direction, the adapter port is displayed at the middle of the fiber storage containers. direction,direction, thethe adapteradapter portport isis displayeddisplayed atat thethe middlemiddleof ofthe thefiber fiber storage storage containers. containers.

Figure 6. Position of the fiber storage containers and adapter ports’ sides in the Z-axis direction. Figure 6. Position of the fiber storage containers and adapter ports’ sides in the Z-axis direction. Figure 6. Position of the fiber storage containers and adapter ports’ sides in the Z-axis direction. The shedding mechanism of the AODF was designed according to the position of the adapter The shedding mechanism of the AODF was designed according to the position of the adapter port sideThe andshedding the fiber mechanism storage containers, of the AODF as shown was design in Figureed according7. The shedding to the position mechanism of the is divided adapter port side and the fiber storage containers, as shown in Figure 7. The shedding mechanism is divided intoport upperside and and the lower fiber components, storage containers, and the as two shown “harnesses” in Figure described 7. The shedding above are mechanism operated separately.is divided into upper and lower components, and the two “harnesses” described above are operated separately. Theintoshedding upper and mechanism lower components, operates theandharness the two composed“harnesses” of described the fiber storage above are containers operated through separately. the The shedding mechanism operates the harness composed of the fiber storage containers through the bottomThe shedding plate of mechanism the sliding operates table and the the harness locking compos device.ed When of the the fiber AODF storage receives containers an instruction through the to bottom plate of the sliding table and the locking device. When the AODF receives an instruction to performbottom plate switching, of the thesliding target table fiber and is the determined locking device. and the When upper the and AODF lower receives shedding an instruction mechanisms to perform switching, the target fiber is determined and the upper and lower shedding mechanisms simultaneouslyperform switching, move the toward target thefiber middle. is determined The upper and sliding the upper table and moves lower downward shedding to mechanisms the bottom simultaneously move toward the middle. The upper sliding table moves downward to the bottom platesimultaneously to contact the move uppermost toward fiberthe middle. storage The container, upper and sliding the lockingtable moves device downward moves downward to the bottom to the plate to contact the uppermost fiber storage container, and the locking device moves downward to upperplate to side contact of the the target uppermost fiber storage fiber container storage contai and locksner, inand the the upper locking position device of themoves target downward optical fiber to the upper side of the target fiber storage container and locks in the upper position of the target optical sothe that upper all theside upper of the portionstarget fiber of thestorage target container optical fiberand locks become in the a “harness”. upper position The lowerof the target sliding optical table fiber so that all the upper portions of the target optical fiber become a “harness”. The lower sliding movesfiber so upward that all tothe the upper bottom portions plate toof contactthe target the optical lowermost fiber fiberbecome storage a “harness”. container, The and lower the locking sliding table moves upward to the bottom plate to contact the lowermost fiber storage container, and the devicetable moves moves upward upward to to the the bottom lower side plate of to the contac targett the optical lowermost fiber storage fiber containerstorage container, and locks and in thethe locking device moves upward to the lower side of the target optical fiber storage container and locks lowerlocking position device ofmoves the target upward optical to the fiber lower such side that of allthe of target the optical optical fibers fiber st inorage the lower container portion and of locks the in the lower position of the target optical fiber such that all of the optical fibers in the lower portion targetin the opticallower position fiber become of the a target “harness”. optical fiber such that all of the optical fibers in the lower portion of the target optical fiber become a “harness”. of the target optical fiber become a “harness”.

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FigureFigure 7. 7. CompositionComposition ofof thethe sheddingshedding mechanism. mechanism.

FigureFigure 8 8 shows shows thethe the rectificationrectification rectification processprocess process of of of thethe the shedding shedding shedding mechanismmechanism mechanism forfor forthethe thesheddingshedding shedding action.action. action. The The initial-stateTheinitial-state initial-state fiberfiber fiber storagestorage storage containerscontainers containers areare arrangedarranged are arranged inin thethe in middlemiddle the middle positionposition position inin order,order, in order, andand the andthe upperupper the upper andand lowerlowerand lower sliding sliding sliding tables tables tablesare are located located are located at at both both atends ends both (Figure (Figure ends 8a). (Figure8a). After After8a). the the After target target the fiber fiber target is is determined, determined, fiber is determined, the the upper upper andandthe upperlowerlower sliding andsliding lower tablestables sliding eacheach tables movemove eachtoto thethe move middlemiddle to the ununtiltil middle theythey bothboth until contactcontact they both thethe contactfiberfiber storagestorage the fiber containerscontainers storage (Figure(Figurecontainers 8b).8b). (Figure TheThe upperupper8b). The andand upper lowerlower and lockinglocking lower devicesdevices locking eaea deviceschch movemove each toto movethethe twotwo to sides thesides two ofof sidesthethe targettarget of the opticaloptical target fiberfiberoptical storagestorage fiber storagecontainer container container forfor locking locking for locking(Figure (Figure (Figure 8c).8c). AfterAfter8c). locking,locking, After locking, thethe upper upper the upperandand lowerlower and slidinglowersliding sliding tablestables tablesmovemove totomove bothboth to sidessides both toto sides formform to thethe form shedshed the (Figure(Figure shed (Figure 8d).8d). 8d).

FigureFigure 8. 8. SheddingShedding process processprocess inin thethe sheddingshedding mechanism. mechanism.mechanism. ( (a(a)a)) The TheThe initial initialinitial state; state;state; ( b ((b)b) sliding) slidingsliding tables tablestables move movemove to totothe thethe middle; middle;middle; (c) ( locking(cc)) lockinglocking devices devicesdevices move movemove and andand lock; lock;lock; (d) sliding((dd)) slidingsliding tables tablestables move movemove to both toto both sidesboth sidessides to form toto form theform shed. thethe shed.shed. When the shedding is completed, the rapier robot performs the switching operation, the robot is withdrawnWhenWhen thethe after sheddingshedding the target isis completed,completed, ﬁber is inserted thethe rapierrapier into roro thebotbot target performsperforms port, thethe and switchingswitching the upper operation,operation, and lower thethe sliding robotrobot isistables withdrawnwithdrawn simultaneously afterafter thethe move targettarget to fiberfiber the middle isis insertedinserted from intointo the sheddingthethe targettarget state port,port, (Figure andand thethe9a) upperupper to reset andand the lowerlower ﬁber storageslidingsliding tablestablescontainers simultaneously simultaneously (Figure9b). move move The locking to to the the middle middle device from unlocksfrom the the (Figuresh sheddingedding9c) state andstate is(Figure (Figure moves 9a) 9a) to to theto reset reset initial the the state fiber fiber on storage storage both containerscontainerssides (Figure (Figure(Figure9d) to 9b).9b). complete TheThe locking locking the entire devicedevice switching unlocksunlocks process. (Figure(Figure 9c) 9c) and and is is moves moves toto thethe initial initial state state onon both both sidessides (Figure(Figure 9d)9d) toto completecomplete thethe entireentire switchingswitching process.process.

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Figure 9. Shedding mechanism: th thee close shed process. ( a)) The The shedding shedding state; state; ( (b)) sliding tables move to close shed; (c) locking devicesdevices unlock;unlock; ((d)) slidingsliding tablestables andand lockinglocking devicesdevices movemove toto initialinitial state.state. 4. Design of the Rapier Robot 4. Design of the Rapier Robot Picking is the insertion of the weft yarn through the shed into the shed formed by the warp Picking is the insertion of the weft yarn through the shed into the shed formed by the warp shedding. The picking mechanism on the loom carries the weft thread from one side of the shed to the shedding. The picking mechanism on the loom carries the weft thread from one side of the shed to other to complete weft insertion. We considered the target fiber to be a weft and the switching operation the other to complete weft insertion. We considered the target fiber to be a weft and the switching to be similar to the picking process. The fiber is removed from the current port and subsequently operation to be similar to the picking process. The fiber is removed from the current port and moved to the target port along a specific path (similar to the shed). The rapier loom uses a flexible or subsequently moved to the target port along a specific path (similar to the shed). The rapier loom rigid rapier as a weft insertion device to achieve insertion of the weft. The rapier head holds the filling uses a flexible or rigid rapier as a weft insertion device to achieve insertion of the weft. The rapier yarn and takes it through the shed. The earliest to appear is a single rapier loom, which is mounted on head holds the filling yarn and takes it through the shed. The earliest to appear is a single rapier loom, one side of the loom with a long rapier that is wider than the width of the cloth and its transmission which is mounted on one side of the loom with a long rapier that is wider than the width of the cloth mechanism, which carries the weft thread through the shed to the other side. Alternatively, the empty and its transmission mechanism, which carries the weft thread through the shed to the other side. rapier sticks into the opposite side of the shed to clamp the weft during the exit process, and the weft Alternatively, the empty rapier sticks into the opposite side of the shed to clamp the weft during the is pulled into the shed to complete the weft insertion. Because the single rapier is wider than the cloth exit process, and the weft is pulled into the shed to complete the weft insertion. Because the single width, the loom is larger and a double rapier loom is developed. The double flexible rapier loom rapier is wider than the cloth width, the loom is larger and a double rapier loom is developed. The reduces the size of the loom. double flexible rapier loom reduces the size of the loom. On the AODF, the working space of the rapier robot should exceed the width of the “cloth”, On the AODF, the working space of the rapier robot should exceed the width of the “cloth”, i.e., i.e., cover both ends of the adapter port side. At the same time, the dimensions must be as small as cover both ends of the adapter port side. At the same time, the dimensions must be as small as possible while satisfying the aim of the work. It can be observed from Figure 10a that the timing belt possible while satisfying the aim of the work. It can be observed from Figure 10a that the timing belt transmission fixed to plate B allows the object A fixed to the belt to move to the right at the same transmission fixed to plate B allows the object A fixed to the belt to move to the right at the same speed (V1) as the belt. If the belt is fixed at the p-point position on plate C (Figure 10b), the timing speed (V1) as the belt. If the belt is fixed at the p-point position on plate C (Figure 10b), the timing belt belt transmission on plate B continues to be driven at the same speed V1, and object A fixed to the belt transmission on plate B continues to be driven at the same speed V1, and object A fixed to the belt can can obtain the same speed V1 to the right. Through motion analysis, plate B moves to the right at the obtain the same speed V1 to the right. Through motion analysis, plate B moves to the right at the speed, V1/2. When plate B moves to the right by distance S1 with respect to plate C (Figure 10c), object speed, V1/2. When plate B moves to the right by distance S1 with respect to plate C (Figure 10c), object A also moves to the right by distance S1 with respect to plate B, and object A moves to the right by a A also moves to the right by distance S1 with respect to plate B, and object A moves to the right by a distance S2 = 2S1 with respect to plate C. distance S2 = 2S1 with respect to plate C.

Electronics 2019, 8, 157 9 of 18 ElectronicsElectronics 20182018,, 77,, xx FORFOR PEERPEER REVIEWREVIEW 99 ofof 1818

FigureFigure 10. 10. Rapier Rapier robot robot double-layer double-layer telescopic telescopic schematic. schematic. ( (aa))) Basic Basic timing timing belt belt transmission transmission structure; structure; ((bb)) double-layerdouble-layer telescopictelescopic speedspeed schematic;schematic; (((cc))) double-layerdouble-layerdouble-layer telescopictelescopictelescopic displacementdisplacementdisplacement schematic.schematic.schematic. TheThe 1 followingfollowing partsparts areare labeled:labeled:labeled: (V(V11))) belt beltbelt speed, speed,speed, (A) (A)(A) object objectobject A, A,A, (B) (B)(B) plate plateplate B, B, (C) (C) plate plate C, C, (p) (p) fixed ﬁxedfixed pointpoint ofof thethe 1 2 belt,belt, (S(S11))) moving movingmoving distance distancedistance of ofof plate plateplate B, B,B, and and (S (S22)) moving moving distance distance of of object object A. A.

AsAs shownshown inin FigureFigure 1010,10,, objectobject AA isis viewedviewedviewed asas thethethe end-grippingend-grippingend-gripping devicedevicedevice forfor thethethe cross-connectcross-connectcross-connect operation,operation, andand thethe designeddesigned rapierrapier robotrobot isis shownshown inin FigureFigure 1111.11.. The The double-layer double-layerdouble-layer telescopic telescopic structure structure cancan obtainobtainobtain nearly nearlynearly twice twicetwice the thethe working workingworking stroke strokestroke of ofof the thethe body, body,body, which whichwhich is located isis locatedlocated in the inin the shedthe shedshed after afterafter shedding sheddingshedding in a randominin aa randomrandom sequence. sequence.sequence. Plates PlatesPlates C and CC andand B in BB Figure inin FigureFigure 10 correspond 1010 correspondcorrespond to the toto the platesthe platesplates Base BaseBase 1 and 11 andand Base BaseBase 2 in 22 Figure inin FigureFigure 11, respectively.11,11, respectively.respectively. Plate PlatePlate Base BaseBase 1 is 11 fixed isis fixedfixed on theonon the distributionthe distributiondistribution frame, frame,frame, and andand plate plateplate Base BaseBase 2 linearly 22 linearlylinearly reciprocates reciprocatesreciprocates on plateonon plateplate Base BaseBase 1 along 11 alongalong the thethe linear linearlinear guide guideguide on onon plate plateplate Base BaseBase 1. 1.The1. TheThe actuator actuatoractuator linearly linearlylinearly reciprocates reciprocatesreciprocates on onon plate plateplate Base BaseBase 2 along22 alongalong the thethe linear linearlinear guide guideguide on onon plate plateplate Base BaseBase 2, 2,2, and andand the thethe timing timingtimingbelt beltbelt is isis fixed fixedfixed to toto the thethe blue blueblue fixation fixationfixation devicedevicedevice onon thethe rightright sideside ofof plateplate BaseBase 1.1. When When the the motor motor on on plat plateplatee Base Base 22 drivesdrives thethe timingtiming belt,belt, plateplate BaseBase 22 movesmoves whilewhile thethe movementmovement ofof thethethe actuatoractuatoractuator isisis driven.driven.driven.

FigureFigure 11.11. Three-dimensionalThree-dimensional modelmodel ofof thethe rapierrapier robot.robot.

InIn FigureFigure 1111,11,, thethe 1616 adapteradapter portsports areare 300300 mmmm wide.widewide.. The The rapier rapier robotrobot hashas aa lengthlength ofof 200200 mmmm andand cancan reachreach 340340 mmmm throughthrough thethe double-layer double-layer telescopictelescopic devicedevice andand cover cover the width width of of 16 16 adapteradapter ports.ports. ThisThis isis alsoalso thethe reasonreason whywhy thethe positionposition ofof thethe aforementionedafaforementionedorementioned ﬁberfiberfiber storagestorage containerscontainers is is set set onon thethe sideside ofof thethe adapteradapter portsports (Figure(Figure5 5b).5b).b). Figure FigureFigure 12 1212 shows showsshows the thethe states statesstates of ofof full fullfull contraction contractioncontraction and andand full fullfull extension extensionextension ofof thethe rapierrapier robot.robot.

Electronics 20192018,, 87,, 157x FOR PEER REVIEW 10 of 18 Electronics 2018, 7, x FOR PEER REVIEW 10 of 18

Figure 12. Working range diagram of the rapier robot. (a) Full contraction state; (b) full extension Figurestate. 12. WorkingWorkingrange range diagram diagram of of the the rapier rapier robot. robot. (a) Full(a) Full contraction contraction state; state; (b) full (b) extension full extension state. state. In order to ensureensure thethe stabilitystability of thethe clamping,clamping, the clamping action of the clamping device is designedIn order to clamp to ensure in parallel, the stability and the of claw the clamping,piece can be the smoothly clamping fitted ﬁtted action with of the the typeclamping SC (Subscriber device is designedConnector) to connector. clamp in parallel, At At the the andsame the time, claw the piece elonga elongated can beted smoothly structure fitted also with facilitates the type movement SC (Subscriber of the Connector)clamping devicedevice connector. between between At the thethe compact same compact time, adapter adapter the portselonga ports panel.ted panel.structure Figure Figure 13 alsoshows 13facilitates theshows two statesthemovement two of looseningstates of the of clampingandloosening clamping anddevice ofclamping thebetween clamping of thethe deviceclampingcompact that deviceadapter are suitable that ports are for suitablepanel. the SC Figure for connector. the 13SC showsconnector. The allowable the Thetwo allowable insertionstates of looseningforceinsertion and force allowableand clampingand allowable pull-out of the forcepull-out clamping of theforce device SC of are the that described SC are are suitable described in the for Standards in the the SC Standards connector. Publication Publication The [31 allowable], with [31], a insertionmaximumwith a maximum force of 19.6 and N.of allowable After19.6 N. testing, After pull-out thetesting, clampingforce the of clamthe device SCping are we device described designed we designedin can the provide Standards can a provide clamping Publication a frictionclamping [31], of withmorefriction a than maximum of more 25 N forthan of the 19.6 25 SC N N. connector.for After the SCtesting, connector. the clam ping device we designed can provide a clamping friction of more than 25 N for the SC connector.

Figure 13. Two states of the rapier robot’s clamping device: (a) loosening; (b) clamping. Figure 13. Two states of the rapier robot’s clamping device: (a) loosening; (b) clamping. 5. Cross-Connect Described by Petri Net 5. Cross-Connect Described by Petri Net When thethe AODFAODF receivesreceives the the remote remote switching switching command, command, the the shedding shedding mechanisms mechanisms perform perform the sheddingthe sheddingWhen action the action AODF to enlarge to receives enlarge the distance thethe remotedistance between switching between the fibers command,the first,fibers then first,the theshedding then rapier the robotrapiermechanisms does robot the doesperform picking the theactionpicking shedding to action remove action to theremove to fiber enlarge fromthe fibe currentther distancefrom port current andbetween moveport theand it tofibers move the target first, it to then port, the targetthe rapier shedding port, robot the mechanism sheddingdoes the pickingclosesmechanism the action shed, closes to and removethe finally shed, the returnsand fibe finallyr thefrom returns completion current the port completion information. and move information. The it to AODF the target The workflow AODF port, canworkflowthe beshedding seen can in mechanismFigurebe seen 14 in. InFigure closes the system, 14. the In shed, the the andsystem, locking finally the device returns locking and the thede vicecompletion rapier and robot the information. rapier have multiplerobot The have positions, AODF multiple workflow so positions, we chose can beabsoluteso weseen chose in encoders Figure absolute 14. in Inencoders the the prototype system, in the tothe prototype record locking the tode corresponding recordvice and the the corresponding rapier movement robot havemovement position. multiple The position. restpositions, of The the so we chose absolute encoders in the prototype to record the corresponding movement position. The

Electronics 2019, 8, 157 11 of 18 Electronics 2018, 7, x FOR PEER REVIEW 11 of 18 movementrest of the movement has only two has states,only two so eachstates, uses so each two setsuses oftwo photoelectric sets of photoelectric switches switches as detection as detection devices, anddevices, the AODFand the uses AODF an industrial uses an industrial personal person computeral computer as the controller as the controller of the prototype. of the prototype.

Figure 14. Automatic optical distribution frame (AODF) working flow chart. Figure 14. Automatic optical distribution frame (AODF) working flow chart. Petri nets (PNs) have been widely applied, modelled, and evaluated in industrial systems. Petri nets (PNs) have been widely applied, modelled, and evaluated in industrial systems. Petri Petri nets are simple, highly flexible, and effective tools for the modelling and analysis of discrete event nets are simple, highly flexible, and effective tools for the modelling and analysis of discrete event systems. This method can describe the structure of the system and simulate the operation of the system. systems. This method can describe the structure of the system and simulate the operation of the Regardless of whether it is complicated or not, it is executed by graphic or matrix representation. system. Regardless of whether it is complicated or not, it is executed by graphic or matrix A Petri net is composed of two types of nodes that represent conditions (or states) and transitions representation. that represent events, which are interconnected by directed arcs. Formally, a basic net is a graph A Petri net is composed of two types of nodes that represent conditions (or states) and transitions represented by the 4-tuple N = (P, T, F, M0), P ∪ T 6= ∅,P ∩ T = ∅, where P is a finite set of places, T is that represent events, which∪ are interconnected by directed arcs. Formally, a basic net is a graph a finite set of transitions, F (P × T) ∪ (T × P) is a finite set of arcs, sets of input and output places of a represented by the 4-tuple N = (P, T, F, M0), P∪T ≠ ∅, P∩T = ∅, where P is a finite set of places, T is a transition are defined as •F ∪ F• = P ∪ T, and M is an initial marking of the net. finite set of transitions, F (P × T) ∪ (T × P) is a 0finite set of arcs, sets of input and output places of a It can be observed from the above that the switching method for simulating the weft insertion of transition are defined as •F∪F• = P∪T, and M0 is an initial marking of the net. the rapier loom undergoes a significant state change between steps, which can be viewed as discrete It can be observed from the above that the switching method for simulating the weft insertion events described by the basic PNs, as shown in Figure 15. The places are in state P before switching, in of the rapier loom undergoes a significant state change between steps, which0 can be viewed as state P1 during the shedding operation, in state P2 during the weft insertion operation, and in state P3 discrete events described by the basic PNs, as shown in Figure 15. The places are in state P0 before switching, in state P1 during the shedding operation, in state P2 during the weft insertion operation,

Electronics 2018, 7, x FOR PEER REVIEW 12 of 18 and in state P3 during the closing shed (i.e., the state of completing the switching), and the transitions are performing the shedding action t0, the weft insertion action t1, and the closing shed action t2. Electronics 2019, 8, 157 12 of 18 Electronics 2018, 7, x FOR PEER REVIEW 12 of 18 andduring in state the closing P3 during shed the (i.e., closing the state shed of (i.e., completing the state theof completing switching), the and switching), the transitions and arethe performingtransitions are performing the shedding action t0, the weft insertion action t1, and the closing shed action t2. the shedding action t0, the weft insertion action t1, and the closing shed action t2. Figure 15. Petri net that describes the cross-connect process.

The Petri net in Figure 15 describes the entire process of switching, and each of these transitions can be divided into subnets. As observed from the above information, the shedding, picking, and Figure 15. Petri net that describes the cross-connect process. closing shed can be describedFigure 15.by Petrione subnet. net that Indescribes Figure the15, cross-connectt0 indicates the process. shedding action, t2 indicates the closing action, and they are mutually reversible. The state of the action and the action performed The Petri net in Figure 15 describes the entire process of switching, and each of these transitions are shownThe Petri in Table net in 1, Figure the Petri 15 describes net of the the shedding entire proc processess of is switching, shown in Figureand each 16a, of andthese the transitions Petri net can be divided into subnets. As observed from the above information, the shedding, picking, and canof closing be divided the shed into is subnets. shown in As Figure observed 16b. from the above information, the shedding, picking, and closing shed can be described by one subnet. In Figure 15, t0 indicates the shedding action, t2 indicates closing shed can be described by one subnet. In Figure 15, t0 indicates the shedding action, t2 indicates the closing action, and they are mutually reversible. The state of the action and the action performed the closing action,Table 1. and Table they of placesare mutually and transitions reversible. in th eThe shedding state ofprocess the action and closing and the the action shed. performed are shown in Table1, the Petri net of the shedding process is shown in Figure 16a, and the Petri net of are shown in Table 1, the Petri net of the shedding process is shown in Figure 16a, and the Petri net closing the shed isP shown00 The in position Figure 16 ofb. sliding table before the shedding operation of closing the shed is shown in Figure 16b. P01 The sliding table is in contact with the fiber storage containers Table 1.P02Table The of places locking and device transitions reaches in the the shedding locking process position and closing the shed. Table 1. Table of places and transitions in the shedding process and closing the shed. Places P03 The Plocking00 deviceThe position completes of sliding locking table before the shedding operation P The sliding table is in contact with the ﬁber storage containers P0004 The positionsliding01 table of sliding completes table thebefore shedding the shedding process operation P02 The locking device reaches the locking position P0001 The sliding table is in contact with the fiber storage containers Places t The sliding table moves P03 The locking device completes locking Pt0102 The Plocking04 deviceThe sliding reachesmoves table the completes locking the position shedding process

Places t The sliding table moves Pt0203 The locking00 device completesperforms the locking locking operation t01 The locking device moves Pt0304 The sliding table completesmoves in the the shedding shedding direction process t02 The locking device performs the locking operation t0020 The slidingt03 tableThe moves sliding tableto the moves middle in the shedding direction t20 The sliding table moves to the middle Transitions t0121 The locking device movesperforms the unlocking operation

Transitions t21 The locking device performs the unlocking operation t0222 The locking device performsmoves the locking operation t22 The locking device moves 03 t23 The slidingt23 tableThe moves sliding tablein the moves shedding direction t20 The sliding table moves to the middle

Transitions t21 The locking device performs the unlocking operation t22 The locking device moves t23 The sliding table moves

Figure 16. The PetriPetri netsnets ofof the the shedding shedding process process and and closing closing the the shed shed when when the the locking locking device device and and the

slidingthe sliding table table move move separately. separately. (a) The (a) The net ofnet transitions of transitions t0;( bt0); the(b) netthe ofnet transitions of transitions t2. t2.

The shedding,shedding, picking,picking, andand closing closing shed shed in in the the loom loom are are cyclical cyclical processes. processes. During During switching, switching, the cycle action of the weft insertion process is different. The closing shed, after the completion of the weft the cycleFigure action 16. The of thePetri weft nets insertion of the shedding process process is different. and closing The closingthe shed shed, when after the locking the completion device and of the insertion, is not completely a mirror image of the shedding process because when the shed is closed, weft theinsertion, sliding tableis not move completely separately. a mirror(a) The netimage of transitions of the shedding t0; (b) the process net of transitions because twhen2. the shed is theclosed, locking the devicelocking locks device the locks fiber the storage fiber container storage container and is integrated and is integrated with the sliding with the table, sliding whereas table, in thewhereas sheddingThe inshedding, the process, shedding picking, these process, areand independent closingthese are shed independent movements.in the loom movements. are The cyclical Petri The net processes. ofPetri the net shed Duringof the closing shed switching, processclosing theisprocess shown cycle is action in shown Figure of thein 16 Figureb,weft in whichinsertion 16b, thein processwhich places theis are di theplfferent.aces same are The with the closing thesame shedding shed, with after the action, sheddingthe completion but throughaction, of but the weftoppositethrough insertion, the transitions. opposite is not The completelytransitions. transitions a The mirror are transitions such image that of theare the slidingsuch shedding that table the process moves sliding to because thetable reset moves when position tothe the shed t20 reset, the is locking device performs the unlocking operation t , the locking device moves the initial state t , and closed,position the t20 ,locking the locking device device locks performs the fiber thestorage unlocking 21container operation and is integratedt21, the locking with device the sliding moves22 table, the the shedding device moves the initial state t . whereasinitial state in thet22, andshedding the shedding process, devicethese are moves independent23 the initial movements. state t23. The Petri net of the shed closing processThe is upper shown and in lower Figure shedding 16b, in mechanisms which the pl canaces move are at the the same same with time orthe at shedding different times. action, In but the 1–nthrough fibers, the when opposite the target transitions. fiber is 1(n),The transitions only the lower are sidesuch (upper that the side) sliding of the table shedding moves mechanism to the reset is required to complete the shedding operation. position t20, the locking device performs the unlocking operation t21, the locking device moves the As shown in Figure7, the locking device can move on the sliding table, move along with the initial state t22, and the shedding device moves the initial state t23. sliding table, or move independently. The Petri net in Figure 16a shows that the locking device moves

Electronics 2018, 7, x FOR PEER REVIEW 13 of 18

The upper and lower shedding mechanisms can move at the same time or at different times. In the 1–n fibers, when the target fiber is 1(n), only the lower side (upper side) of the shedding mechanism is required to complete the shedding operation. Electronics 2019, 8, 157 13 of 18 As shown in Figure 7, the locking device can move on the sliding table, move along with the sliding table, or move independently. The Petri net in Figure 16a shows that the locking device moves alongalong with with the the sliding sliding table table first, first, then then moves moves independently independently to to the the target target position. position. After After the the locking locking devicedevice is is unlocked, unlocked, the the Petri Petri net net in in Figure Figure 16 16bb shows shows it it first first moves moves to to the the initial initial position position on on the the sliding sliding tabletable and and then then moves moves along along with with the the sliding sliding table. table. IfIf the the locking locking device device moves moves independently independently toto thethe initial initial (target) (target) position position onon the the sliding sliding table table whilewhile the the slidingsliding tabletable isis moving,moving, the Petri nets indicating indicating the the shedding shedding and and the the closing closing are are shown shown in inFigure Figure 17a,b, 17a,b, respectively. respectively. The The sliding sliding table table and and the the locking device move simultaneously,simultaneously, soso theirtheir initialinitial state state is is considered considered separately. separately. In In the the shedding shedding process, process, the the places places are are state state P 000P000of of the the sliding sliding tabletable before before the the shedding shedding operation operation and and state state P P001001 ofof thethe locking devicedevice beforebefore thethe sheddingshedding operation.operation. InIn the the process process of closingof closing the shed,the shed, the locking the locking device de locksvice the locks fiber the storage fiber containers storage containers and is integrated and is withintegrated the sliding with table the sliding first, then table they first, can then move they separately can move after separately unlocking; after the unlocking; places are the state places P020 areof thestate sliding P020 of table the sliding after unlocking table after and unlocking state P021 andof thestate locking P021 of devicethe locking after unlocking.device after unlocking.

FigureFigure 17. 17.The The Petri Petri nets nets of of the the shedding shedding process process and and closing closing the the shed shed when when the lockingthe locking device device and theand slidingthe sliding table table move move simultaneously. simultaneously. (a) The (a) netThe of net transitions of transitions t0;(b )t0 the; (b) net the of net transitions of transitions t2. t2.

In Figure 15, transition t indicates the shedding action. The process of performing the weft In Figure 15, transition 1t1 indicates the shedding action. The process of performing the weft insertioninsertion using using the the rapier rapier robot robot can can be be disassembled disassembled into into multiple multiple steps. steps. The The state state of of the the action action and and thethe action action performed performed are are shown shown in in Table Table2. 2. The The Petri Petri net net description description of of the the entire entire process process is is shown shown in in FigureFigure 18 18.. The The process process of of weft weft insertion insertion can can be be treated treated as as a a cyclical cyclical action action process process of of the the rapier rapier robot robot startingstarting from from the the initial initial state state and and ﬁnally finally returning returning to to the the initial initial state. state.

Table 2. Table of places and transitions (Tr) in the picking process. Table 2. Table of places and transitions (Tr) in the picking process.

P10 The rapier robot on the initial position P10 The rapier robot on the initial position P11 Rapier robot arrives the target fiber position P11 Rapier robot arrives the target fiber position P12 Clamping device arrives target fiber P12 P Clamping13 deviceClamping arrives device target clamps fiber the target fiber P13 P Clamping14 deviceClamping clamps device the pulls target out fiber the target fiber

Places P Rapier robot moves to the target port P14 Clamping15 device pulls out the target fiber

Places P16 Clamping device inserts the target ﬁber P15 Rapier robot moves to the target port P17 Clamping device releases the target ﬁber P16 Clamping device inserts the target fiber P18 Clamping device back to the initial position P17 Clampingt10 deviceRapier releases robot moves the target fiber P18 Clampingt11 deviceClamping back device to the moves initial position t10 Rapiert12 robotClamping moves device clamps t13 Clamping device moves t11 Clamping device moves t14 Rapier robot moves t12 Clamping device clamps t15 Clamping device moves Transitions

Transitions 13 t Clampingt16 deviceClamping moves device release t17 Clamping device moves t18 Rapier robot moves Electronics 2018, 7, x FOR PEER REVIEW 14 of 18

Electronics 2018, 7, x FOR PEER REVIEW 14 of 18 t14 Rapier robot moves t15 Clamping device moves t14 Rapier robot moves t16 Clamping device release t15 Clamping device moves t17 Clamping device moves t16 Clamping device release t18 Rapier robot moves t17 Clamping device moves Electronics 2019, 8, 157 14 of 18 t18 Rapier robot moves

Figure 18. Petri net of the picking process. Figure 18. Petri net of the picking process. The Petri nets are used Figureto represent 18. Petri thenet ofentire the picking cross-connect process. process, and the process is decomposedThe Petri into nets subnets are used for to represent representation, the entire making cross-connect the design process, of the and control the process system is decomposed clearer and The Petri nets are used to represent the entire cross-connect process, and the process is intoeasier. subnets for representation, making the design of the control system clearer and easier. decomposed into subnets for representation, making the design of the control system clearer and easier. 6. Prototype Design and Experiment

6. PrototypeThe rapier Design robot and moves Experiment in the plane of the adapter ports, enabling the connector to be unplugged or plugged in in and and to to stabilize stabilize gripping gripping of of the the connector connector while while it moves it moves in inthe the shed. shed. By combining By combining the The rapier robot moves in the plane of the adapter ports, enabling the connector to be unplugged theadapter adapter port port panel, panel, the shedding the shedding mechanism, mechanism, the input the input and output, and output, the corresponding the corresponding controller, controller, and or plugged in and to stabilize gripping of the connector while it moves in the shed. By combining the andthe frame, the frame, an AODF an AODF prototype prototype was constructed was constructed that imitates that imitates the picking the picking of the ofrapier therapier loom. loom.The three- The adapter port panel, the shedding mechanism, the input and output, the corresponding controller, and three-dimensionaldimensional model model is shown is shown in Figure in Figure 19. The 19. outer The outer dimensions dimensions of the of prototype the prototype are are42 cm 42 cmlong long by the frame, an AODF prototype was constructed that imitates the picking of the rapier loom. The three- by27 cm 27 cmwide wide by by31 cm 31 cmtall. tall. dimensional model is shown in Figure 19. The outer dimensions of the prototype are 42 cm long by 27 cm wide by 31 cm tall.

Figure 19. Drawing of the AODF prototype.

Using SC simplex adaptersFigure can 19. achieve Drawing the of same the AODF insertion prototype. loss and the same return loss as the standard patch panel. There is enough space in the model to set up the the fiber fiber end end face face cleaning cleaning device, device, Using SC simplex adapters can achieve the same insertion loss and the same return loss as the and it was necessary to clean the endend faceface duringduring reconfigurationreconfiguration toto produceproduce low-losslow-loss connections.connections. standard patch panel. There is enough space in the model to set up the fiber end face cleaning device, In the demonstration system, the input terminals are SC simplex adapters and a bend-insensitive bend-insensitive and it was necessary to clean the end face during reconfiguration to produce low-loss connections. single-mode fiberfiber [[32].32]. We created an experimental model of the prototypeprototype and a series of switching In the demonstration system, the input terminals are SC simplex adapters and a bend-insensitive tests were performedperformed on the model.model. Figure 20 showsshows a random sequence of fiberfiber 06 switchingswitching from single-mode fiber [32]. We created an experimental model of the prototype and a series of switching port 03 to port port 15, 15, and and the the fibers fibers on on the the left left to to right right port port are are 07, 07, 15, 15, 06, 06, 02, 02, 11, 11,05, 05,12, 12,04, 04,14, 14,13, 03, 13, 01, 03, tests were performed on the model. Figure 20 shows a random sequence of fiber 06 switching from 01,09, 10, 09, 00, 10, and 00, 08, and where 08, where 00 is the 00 target is the port target of portthe switching of the switching and no fiber and is no inserted. fiber is When inserted. the AODF When port 03 to port 15, and the fibers on the left to right port are 07, 15, 06, 02, 11, 05, 12, 04, 14, 13, 03, 01, thereceives AODF the receives cross-connect the cross-connect command, command,the shedding the mechanism shedding mechanism first performs first a performs shedding a operation shedding 09, 10, 00, and 08, where 00 is the target port of the switching and no fiber is inserted. When the AODF operationaccording accordingto the command to the commandsuch that the such gap that on the both gap sides on bothof the sides target of fiber the target is sufficient fiber is for sufficient the rapier for receives the cross-connect command, the shedding mechanism first performs a shedding operation the rapier robot to enter. The rapier robot extends from the shed to the current position of the target according to the command such that the gap on both sides of the target fiber is sufficient for the rapier fiber, removes the fiber and moves to the target port, inserts the fiber into the target port, and exits the shed. The shedding mechanism closes the shed inward to complete the switching operation. According to the higher always on top method described by Yang et al. [28], fibers 01–05 are above fiber 06, and fibers 07–15 are below fiber 06. During the switching process, fiber 06 passes below fibers 01–05 and crosses over fibers 08–14. Every time the robot crosses over the fiber, two handover Electronics 2018, 7, x FOR PEER REVIEW 15 of 18 robot to enter. The rapier robot extends from the shed to the current position of the target fiber, removes the fiber and moves to the target port, inserts the fiber into the target port, and exits the shed. The shedding mechanism closes the shed inward to complete the switching operation. ElectronicsAccording2019, 8, 157 to the higher always on top method described by Yang et al. [28], fibers 01–0515 ofare 18 above fiber 06, and fibers 07–15 are below fiber 06. During the switching process, fiber 06 passes below fibers 01–05 and crosses over fibers 08–14. Every time the robot crosses over the fiber, two actionshandover are actions required are with required the commutation with the commutation device. The device. entire The process entire requires process seven requires times seven handover times actions.handover In actions. the experiment In the experiment with the prototype with the based prototype on the based higher on always the higher on top always method, on thetop handover method, actionsthe handover occupy actions most of occupy the switching most of process the switchin time. Assumingg process thattime. the Assuming robot has that the samethe robot speed has on the AODF,same speed its motion on the timeAODF, is Tr, its whereas motion time a typical is Tr, shedding whereas a time typical is about shedding 12 seconds, time is andabout the 12 time seconds, for a handoverand the time action for ina handover the previous action higher in the always previous on top higher method always prototype on top is method about 10 prototype seconds. Theis about total × time10 seconds. of the higherThe total always time on of topthe methodhigher always is TH = on Tr top+ 7 method10 s, whereas is TH = T ther + 7 time × 10 for s, thewhereas shedding the time and pickingfor the shedding method is and TS =picking Tr + 12 method s. is TS = Tr + 12 s.

Figure 20. Cross-connect process of a random sequence.

According to the switching test on the experimental model protot prototype,ype, the cross-connect method proposed in this paper can realize rapid switching, but the smaller capacity of the prototype is a weakness. As observed from Figure 6 6,, thethe factorsfactors thatthat restrictrestrict thethe capacitycapacity ofof thethe AODFAODF areare primarilyprimarily the size of the rapier robot and the size of the fiber fiber storage container. If the size of the rapier robot is reduced and the required shedding distance in the Z-direction is reduced, i.e., the height of the shed is reduced, thereby reducing the height of the AO AODF,DF, the reduction in the size of the fiberfiber storage container directly reduces the height ofof thethe AODF.AODF. To reduce the outer dimensions of the device, we configuredconfigured a second layer port on the adapter port side of of the the model model prototype prototype aligned aligned with with the the ga gapp between between the the first first layer layer ports, ports, with with 16 ports 16 ports on on the first layer and 15 on the second layer. A random shedding simulation was performed on the two-layer model, as shown in Figure 21. The shed size satisfies the existing rapier robot for weft insertion. However, to operate the upper and lower connectors, in addition to the current degrees of freedom in the X- and Y-directions, it was necessary to design a Z-direction freedom. Electronics 2018, 7, x FOR PEER REVIEW 16 of 18 theElectronics first layer 2018, and7, x FOR 15 onPEER the REVIEW second layer. A random shedding simulation was performed on the16 two- of 18 layer model, as shown in Figure 21. The shed size satisfies the existing rapier robot for weft insertion. the first layer and 15 on the second layer. A random shedding simulation was performed on the two- However, to operate the upper and lower connectors, in addition to the current degrees of freedom layer model, as shown in Figure 21. The shed size satisfies the existing rapier robot for weft insertion. in the X- and Y-directions, it was necessary to design a Z-direction freedom. ElectronicsHowever,2019 to, 8operate, 157 the upper and lower connectors, in addition to the current degrees of freedom16 of 18 in the X- and Y-directions, it was necessary to design a Z-direction freedom.

Figure 21. Double-port shed diagram.

Referring to the gap configurationFigure 21.of theDouble-port adapter shedports, diagram. the gap of the fiber storage containers can be configured to increase the density of the fiber when the size of the fiber storage container is Referring toto thethe gapgap configuration configuration of of the the adapter adapter ports, ports, the the gap gap of theof the fiber fiber storage storage containers containers can fixed. In the three-dimensional model of Figure 19, the gap configuration of two sets of fiber storage becan configured be configured to increase to increase the density the density of the of fiber the when fiber thewhen size the of thesize fiber of the storage fiber containerstorage container is fixed. Inis containers was tested, as shown in Figure 22. The two circles in the figure represent two sets of fiber thefixed. three-dimensional In the three-dimensional model of Figuremodel 19of ,Figure the gap 19, configuration the gap configuration of two sets of of two fiber sets storage of fiber containers storage storage containers, indicated by the solid and dashed lines of the fibers that denote the possible wascontainers tested, was as showntested, inas Figureshown 22in. Figure The two 22. circlesThe tw ino circles the figure in the represent figure represent two sets two of fiber sets storageof fiber connection of the fiber status. It can be observed from Figure 22 that the double column design of the containers,storage containers, indicated indicated by the solid by andthe dashedsolid and lines dash of theed lines fibers of that the denote fibers thethat possible denote connection the possible of fiber storage containers is feasible. The configuration of the double column and the double layer of theconnection fiber status. of the It fiber can bestatus. observed It can from be observed Figure 22 from that Figure the double 22 that column the double design column of the design fiber storage of the the gap still satisfy the spatial relationship of noncoplanar lines of the 1-D to 1-D form, and the containersfiber storage is containers feasible. The is feasible. configuration The configuration of the double of column the double and column the double and layer the double of the gaplayer still of capacity is doubled while the overall size is generally the same. Similarly, in the case of a single-layer satisfythe gap the still spatial satisfy relationship the spatial of relationship noncoplanar of lines noncoplanar of the 1-D tolines 1-D of form, the and1-Dthe to capacity1-D form, is doubledand the adapter ports, the double column design of the fiber storage containers can also reduce the outer whilecapacity the is overall doubled size while is generally the overall the size same. is generall Similarly,y the in thesame. case Similarly, of a single-layer in the case adapter of a single-layer ports, the dimensions. doubleadapter column ports, the design double of the column fiber storagedesign containersof the fiber can storage also reduce containers the outer can dimensions.also reduce the outer dimensions.

Figure 22. Double ﬁber storage containers: column connect diagram. Figure 22. Double fiber storage containers: column connect diagram. 7. Conclusions 7. Conclusions Figure 22. Double fiber storage containers: column connect diagram. In this paper, we propose a cross-connect method that imitates the weft insertion of the rapier loom,7. ConclusionsIn andthis we paper, designed we propose the corresponding a cross-connect shedding method mechanism that imitates and thethe rapier weft insertion and produced of the a rapier model loom, and we designed the corresponding shedding mechanism and the rapier and produced a prototype.In this PNspaper, were we used propose to analyze a cross-connect the entire method switching that process, imitates clarifying the weft theinsertion switching of the process. rapier model prototype. PNs were used to analyze the entire switching process, clarifying the switching Anloom, experiment and we designed on the prototype the corresponding was conducted shedding to verify mechanism the cross-connect and the rapier method, and which produced greatly a process. An experiment on the prototype was conducted to verify the cross-connect method, which improvedmodel prototype. the switching PNs were speed. used Compared to analyze with the the en highertire switching always on process, top method, clarifying the switching the switching time greatly improved the switching speed. Compared with the higher always on top method, the ofprocess. this method An experiment was faster. on Inthe this prototype method, was the adapterconducted port to panelverify canthe becross-connect set to many method, layers, but which the switching time of this method was faster. In this method, the adapter port panel can be set to many “noncoplanargreatly improved lines” the condition switching must speed. be satisﬁed. Compared The system with the is small higher and always can be easilyon top assembled method, intothe theswitching existing time communication of this method cabinet. was faster. The structure In this method, is simple, the the adapter motors port used panel are relatively can be set small, to many and the power consumption of the whole machine is also low. Future research is planned to optimize this approach and the corresponding mechanisms. Electronics 2019, 8, 157 17 of 18

Author Contributions: Funding acquisition, S.W.; Methodology, Z.Y. and Y.S.; Resources, L.G.; Supervision, L.G.; Validation, Z.Y. and Y.S.; Writing—original draft, Z.Y.; Writing—review & editing, S.W., L.G., and Y.S. All authors have read and approved the final paper. Funding: This work was supported by the Beijing Municipal Natural Science Foundation under Grant L172031, the National Natural Science Foundation of China under Grant 51375059 and Grant 61105103, the National High Technology Research and Development Program of China under Grant 2011AA040203, and the Seed Program of the Beijing University of Posts and Telecommunications Information Network Industry Research Institute. Conflicts of Interest: The authors declare that there are no conflicts of interest.

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