- Email: [email protected]
insertion
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Gripping tool for the ITER upper port plug RH extraction/insertion Elena V. Rosa ∗ , Luis Ríos Asociación Euratom-Ciemat, Avda. Comlutense 40, 28040 Madrid, Spain
h i g h l i g h t s • • • • •
The gripping tool is based on only one gripping point centred at the plug bottom. The gripping tool should allow the relative displacement in the gripping point to absorb the misalignment between plug and tractor. The gripping tool needs to withstand around 100/30 kN during the plug extraction/insertion. The gripping tool should rely on visual control and it has to avoid force feed-back. The comparison between the features of several gripping tool concepts is assessed.
a r t i c l e
i n f o
Article history: Received 12 September 2013 Received in revised form 7 February 2014 Accepted 24 March 2014 Available online xxx Keywords: ITER Upper port plug Remote handling Gripping tool Plug extraction/insertion Force feedback
a b s t r a c t The conceptual design of several gripping tools and their mechanical interfaces is being carried out for the ITER ECH UPP within the WP10-GOTRH programme. EFDA finances the GOT RH (Goal Oriented Training Programme for Remote Handling). The purpose of this paper is to introduce new concepts of gripping tools for the plug extraction/insertion in the upper port of ITER. All these gripping tools are designed according to IO input data and geometrical constraints. The gripping tools have to be able to extract/insert the plug in the scenario of maximum misalignment between the plug and the tractor. The paper also defines the functional requirements the gripping tools need to comply with. The requirements and input data are verified and validated through 3D simulation with Catia mock-ups of the gripping tools. The strengths and weaknesses of each gripping tool model are compared. © 2014 Elsevier B.V. All rights reserved.
1. Introduction This paper is centred on the development of several gripping tool (GT) concepts to carry out the plug extraction/insertion in the ITER upper port. The main components involved in each tool, as well as the design of the joint interfaces between GT and plug/tractor to absorb the misalignment between plug and tractor are described. Finally, the specific features of each GT are analyzed in order to carry out a comparison between the tools.
2. Previous works and concepts Previous works centred on the interface between UPP and Cask and Plug Remote Handling System (CPRHS) [1,2] summarize the
∗ Corresponding author. Tel.: +34 914962579. E-mail addresses: [email protected] (E.V. Rosa), [email protected] (L. Ríos).
starting point and the progress on the development of the GT concepts. The geometries of the UPP and CPRHS are given by the ITER catia model and an overview of these geometries and their interfaces can be seen in Ref. [1]. They are simplified to see easily the main parts that work in the plug extraction/insertion by the tractor (Fig. 2). According to Ref. [3], it is assumed that the plug is guided by six skids resting on the port duct rails and ramp rails of the Transfer Cask System (TCS). The rails are at an angle of 11◦ relative to the port cell floor (Fig. 2). It is assumed the maximum clearance between skids and rails is 10 mm [3] in order to absorb the 0.1◦ of misalignment between port duct and ramp rails [4]. Thus, the plug weight and tractor force are sloping and misaligned on the rails. In this environment, a previous conceptual kinematic and friction studies was carried out in [1] whose conclusions were the GT should be designed with only one gripping point (GP) centred at the bottom of the surface delimited by the flange for the UPP. The single centred connection point facilitates turning of the UPP and reduces the jamming risk during extraction/insertion. It also makes remote connection/disconnection easier and faster.
http://dx.doi.org/10.1016/j.fusengdes.2014.03.063 0920-3796/© 2014 Elsevier B.V. All rights reserved.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
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FUSION-7408; No. of Pages 5
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2
Table 1 Kinematic study results corresponding to position 1 and 3. Pos.
ϕ
˛
“y” disp.
“z” disp.
1 3
NA 0.523◦
0.423 0.423
16.5 mm 10 mm
3.9 mm 4.1 mm
Further kinematic and friction studies were developed in Ref. [2]. The Catia kinematic study simulated the plug sliding on the rails to assess the maximum clearances between skids and rails (±26.5 mm/±5 mm in “y/z” direction [2]). Thus the maximum movement of the front part of the plug centred at the bottom can be set (±16.5 mm/±5 mm in “y/z”direction, Table 1). That is the clearances in the GP (Fig. 2, “y/z”displacements). The friction study was carried out with a more conservative friction coefficient 0.3 [2] for the most misaligned positions of the plug regarding to the rails during its transference (obtained from kinematic study (ϕ, ˛), Table 1). The friction study solves the static equilibrium of forces between skids and rails for a symmetric geometry. The worst positions regarding misalignment (Table 1) correspond to position 1 (the front and rear skids rested on the port duct rails) and position 3 (the front skids rested on the port cell rails and the rear skids rested on the port duct rails). Where: ϕ is the relative angle between the plug axis and port cell rail axis, ˛ is the relative angle between the plug axis and port duct rail axis and “y/z” displacements are the relative displacements of the “plug interface” (Fig. 2) measured from the axis of the ramp rails (“tractor interface”, Fig. 2) in the y and z directions. 2.1. Kinematic and friction study conclusions The kinematic study suggests adding a curved shape to the inner walls of the skids (Fig. 1). This helps in the turning of the plug and helps to absorb the misalignments. This concept should be dimensioned and assessed by a kinematic study. However, this paper assumes the skids proposed in the ITER documentation [3]. The friction study [2] gives an approximate minimum pushing/pulling tractor force of 95 kN/20 kN. The misalignments between plug and tractor and rails do not have a severe influence on the friction forces. This is due to the fact that the misalignments are very small and due to the symmetric geometry. 2.2. Main GT requirements - Only one GP of connection, thus the balance of friction forces, tractor forces and plug weight is compensated due to the symmetric geometry around the axis that contains the GP. The GT needs to withstand around 100/30 kN during the plug extraction/insertion, respectively. - The GT should allow the relative displacement in the GP to absorb the misalignment between plug and tractor and to reduce the loads between skids and rails during the plug extraction/insertion. For that, it has been assumed a relative
Fig. 1. Suggested double curvature in the skids of the plug.
Fig. 2. Joint between plug/tractor and GT and GP (end-effector) of the GT.
displacement in the GP of ±20 mm horizontally (y) and ±5 mm vertically (z) (Table 1, Fig. 2). - The GT should work with minimum sensor onboard the TCS. Thus, the GT should rely on visual control as much as possible. Concretely, the GT has to avoid force feed-back during the tool engagement/disengagement.
2.3. Key ideas about the GT concepts The GT concept is defined by three parts: the GT part connected to the plug interface, the GP, and the GT part connected to the tractor interface (Fig. 2). The GP displacements can be managed through clearances or degrees of freedom (DoF) in the joints between the three parts of the GT defined above (Fig. 2). These joints are placed at the bottom and in the middle point of the plug and tractor and they can be rigid (–䊉–), articulated (–)–) or with clearances in “y/z” direction (). The “z” GP displacements of the tool (±5 mm) are managed through clearances for all the tools presented in the paper (from Fig. 3 to Fig. 10). This work assumes the plug GT part can be bolted manually on the plug prior to the plug RH extraction. The GTs need electromechanical actuators like stepper motors to actuate the closing system parts. All the closing systems of the GTs presented in this paper feature a back-up stepper motor for the tool recovery in case of failure of the first stepper motor. Stepper motors do not need a gearing system for speed reduction and torque multiplication, so they can be directly coupled to the shaft. This allows to avoid gearing system related failure modes (e.g. blockage). In addition, stepper motors can be used without positional feedback,. All the tools could be operated by visual control without any feedback signals from sensors if the closing system parts are sufficiently visible. In any way, the tool connection/disconnection could be executed by using visual references, such as painting marks on
Fig. 3. GT1. Tow-Hitch.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
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Fig. 5. GT2. Mushroom-Hoop.
Fig. 4. GT1. Components and DoF.
the rails and GT parts that indicate the right position to actuate the closing system. The motor command signal would also give information on the position of the closing system parts. However, if allowed by the limitations regarding the number of sensors on board the TCS, the GT connection/disconnection as well as the plug extraction/insertion could be facilitated with a force sensor that could measure the pulling/pushing force of the tractor. This information would reduce the risk of damage to the plug during connection. In addition, it would provide information about potential problems during extraction/insertion (e.g. tool jamming, skids jamming. . .). This information cannot be inferred from visual observation. 3. Gripping tools 3.1. GT1. Tow-Hitch 3.1.1. Description of the tool The Tow-Hitch gripping tool (Fig. 3) has two turning joints, one connected to the plug interface and the other in the GP, allowing the horizontal GP displacement (±20 mm). This tool uses some alignment concepts for the end-effector similar to the other commercial product made by JOST [5]. They are adapted to the ITER GT requirements for the UPP [1,2] previously summarized. The tool (Fig. 4) is composed of an articulated hitch (bolted to the plug interface) with a hole at its end. The conic structure (part of the GT part connected to the tractor interface) guides the hitch end towards the GP until it presses a trigger. The pressing of the trigger allows a stepper motor to turn a cam which makes a rod go down/up into/out of the hitch hole. The rod is prevented from moving vertically out of the hitch hole by the cam and the motor shaft (holding torque). The engagement/disengagement of the hitch is carried out in a horizontal plane. A shock absorber limits the impact loads on both plug and tractor during connection/disconnection that is carried out in the horizontal plane. When the plug is being pushed/pulled, the axial (x direction) load is taken by the hitch, rod, jacket and shock absorber structure. The cam and stepper motors are not affected by this load. The signal of the motors shows the cam position (the motor shafts is straightly connected to the cam), and are not costly components. The motors could also lock the position of the cam. The visual control of the tool operation could be helped by painting marks on the rails and hitch indicating the position at which the rod can be lowered. The motor command signal would also give information on the position of the cam (and indirectly the rod).
3.1.2. Comparative analysis The double turning joints between plug and tractor (Fig. 3) prevent the appearance of off centred loads in the tool GP. In this way the additional loads associated to torques coming from these off centred loads are avoided. This is not the case in GT2 or GT3. Because of the guidance and alignment provided to the hitch by the cone, the clearances in the gripping point between the plug part and tractor part of the gripping tool are significantly smaller than in other tool concepts such as GT2 or GT3. This limits loads coming from potential hitch movements within this clearance during extraction/insertion of the plug. From the point of view of load bearing, this gripping tool isolates the structural components (hitch, rod, jacket) from the rod actuators (cam, motors shaft). This reduces the dimensioning and risk of failure of the shaft, bearings and motors that actuate the cam. This is a difference with GT2. The tool engagement/disengagement (hitch into/out of cone) and the fastener (rod) movements are carried out in different planes (horizontal/vertical). This prevents the accidental release of the plug (for example, during seismic events). 3.2. GT2. Mushroom-Hoop 3.2.1. Description of the tool The Mushroom-Hoop gripping tool (Fig. 5) is composed by a mushroom grip, one hoop as end-effector and two stepper motors that turn and lock the hoop. The horizontal GP displacements (±20 mm) are managed by clearances in the hoop (tool GP) and rigid joints in the GT-plug and GT-tractor interfaces (Fig. 6). The tool does not need GP alignment. The tool connection/disconnection is carried out in the vertical plane through the hoop turning.
Fig. 6. GT2. DoF and clearances.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
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Fig. 7. GT3. Twist-Lock.
The mushroom shape of the grip prevents the GT disconnection. The wider rear part of the hoop allows to introduce the mushroom head into the hoop. The narrower hoop front part allows only for the required clearances in the GP. The tractor has to do a forward/backward movement in order to reach the GT connection/disconnection position. The closing system is composed by two stepper motors and the hoop. The motor shafts are straightly connected to the hoop turning shaft. The stepper motors are used without position feedback so the signal of the motors indicates the hoop position. They could also be used to lock the hoop position during insertion/extraction of the UPP (holding torque). The tool operation could rely exclusively on visual control with the aid of painted marks. 3.2.2. Comparative analysis Contrary to GT1 and GT4, the clearances in the GP of GT2 allow the free movement of the mushroom grip inside the hoop. This can produce off centred transference of the load that may lead to larger dimensioning of the tool and tractor structure. The misalignments are small, though, so the impact on the dimensioning may be limited. Because of the higher clearance between the tractor and plug parts of the gripping tool, the loads coming from mushroom grip movements within this clearance during extraction/insertion or seismic event will be higher than those expected in GT1 or GT4. Contrary to the other tools, GT2 does not feature a shock absorber to reduce loads during the tool engagement/disengagement due to the fact that the tractor does not need to push the tool to be connected (it is carried out in the vertical plane). The tool dimensioning would need to take into account these dynamic loads. The design could be adapted to include a shock absorber if needed, though. Contrary to GT1 or GT4, the stepper motors shaft, coupled in GT2 to the hoop, will see loads during insertion and extraction of the plug. The bearings on the shaft would need to be dimensioned to take this radial load. The mushroom shape of the grip prevents the accidental release of the plug limiting vertical hoop movement. If the motors are active during extraction/insertion of the plug, they will apply a holding torque acting against an accidental lifting of the hoop. This tool presents the advantage of having an, in principle, simpler design than that of the other tools presented. 3.3. GT3. Twist Lock 3.3.1. Description of the tool The Twist-Lock gripping tool (Fig. 7 and Fig. 8) has the following design features:
Fig. 8. GT3. Components.
A cavity placed in the tool part connected to the plug interface. The twistlock is inserted through a slotted hole in the cavity and then turned to lock (the turning is contained in the “yz” plane). The cavity has enough clearances to absorb the relative displacements between twistlock and cavity appearing during insertion/extraction of the plug (see Table 1). The twist-lock shaft is connected to two stepper motors. The axial load is transferred from the shaft to the tool body structure by a stop feature in the shaft. An articulated joint (tractor interface joint, Fig. 2) allows for some turning of the twistlock supporting structure (Fig. 7). The tractor interface joint is composed by a pin ball, allowing the turning of the whole twistlock supporting structure, and several springs that keep the twistlock supporting structure straight when inserting/extracting the twistlock through the slotted hole into/out of the cavity (Fig. 8). The pin ball increases the contact between the twistlock and twistlock cavity surfaces during extraction/insertion and the springs allow the twistlock and twistlock cavity to be better aligned during tool connection/disconnection. The tool operation could be carried out by visual control and painting marks on the rails and the twist-lock shaft. 3.3.2. Comparative analysis This tool presents the same issues as GT2 regarding clearances in the GP leading to off centred transference of load and dynamic loads coming from relative movements in the GP during plug extraction/insertion. Contrary to GT2, the tool engagement/disengagement (horizontal) and the fastener movement (rotation) are carried out in different planes (horizontal/vertical). This prevents the possibility of accidental plug release. 3.4. GT4. Pin-Plate 3.4.1. Description of the tool The Pin-Plate gripping tool (Fig. 9) uses similar alignment concepts to the commercial tool [5].These concepts are adapted to the ITER GT requirements for the UPP [1,2] that are summarized in Section 2. The horizontal GP displacements (±20 mm) are managed through two turning joints and one rigid joint (Fig. 9). The Mushroom pin-plate tool is comprised of the parts shown in Fig. 10. The mushroom grip is guided by a wedge shaped feature in the plate to the GP. When the mushroom grip is in the GP, a stepper motor turns a cam and the rod moves horizontally, locking the mushroom grip.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
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rod movement in “y” direction that could release the plug. Contrary to GT1, the rod movement is horizontal instead of vertical (design potentially needing more attention to ensure proper functioning and prevent jamming). Similarly to GT1, The tool isolates structurally the rod actuator components (motor and cam) of the load bearing components (rod, plate, mushroom grip) to prevent load transference to the motor shaft. 3.5. Conclusions
Fig. 9. GT4. Mushroom pin-plate.
Fig. 10. GT4. Components and DoF.
A shock absorber limits the impact loads on both UPP and tractor during connection/disconnection due to the tool engagement/disengagement is carried out in the horizontal plane. The locking of the rod in “y” direction (rod axis) is ensured by the holding torque of the motor. This tool features a good visual control for the operations. 3.4.2. Comparative analysis This tool is similar to GT1 regarding the use of a double articulated joint and the absence of clearances in the GP preventing off centred transference of load and dynamic loads coming from relative movements in the GP during plug extraction/insertion. The tool engagement/disengagement (x) and the fastener movement (y) are carried out in the same plane (horizontal). Similarly to GT2, the mushroom shape of the grip prevents the accidental release of the plug by limiting vertical movement of either tractor or plug. The locking action of the motors prevents the accidental
The double turning joints between plug and tractor (GT1 and GT4) reduce the loading on the tool structure and lead to smaller dimensioning. However, the clearances between plug and tractor (GT2 and GT3) avoid the need for tool GP alignment. The accidental release of the plug is better avoided when the tool engagement/disengagement and the fastener movement are carried out in different planes. The vertical movement of the fastener has the advantages of facilitating the engagement and also reducing the risk of plug release. All the GT can be connected/disconnected relying exclusively on visual control. The installation of a force sensor would provide a valuable information impossible to obtain visually that would facilitate the RH connection/disconnection operation. The shock absorber is not required for the tool connection/disconnection. However, it is recommended for those tools for which connection/disconnection is carried out in the horizontal plane (GT1, 3 and 4), as it will limit the loads on plug and tractor. The shock absorber could be installed in all the concepts of tools to limit loads as well during its transference. Acknowledgments This work was carried out under the EFDA Goal Oriented Training Programme (WP10-GOT- GOTRH) and financial support of Ciemat, which are greatly acknowledged. The views and opinions expressed herein do not necessarily reflect those of the European Commission. References [1] E. Rosa, L. Rios, V. Queral, Progress on the interface between UPP and CPRHS tractor/gripping tool for ITER, Fusion Eng. Des. 88 (2013) 2168–2172. [2] E. Rosa, Review Meeting Presentation, Ciemat (March 2013). http://labfus. ciemat.es/AR/2012/CAP4/GOT 2.pdf [3] B. Levesy, Port Plug Handling, IDM PCR-439, IO (June 2012). [4] A. Tesini, J. Preble, J.-J.Cordier, C. Hyung Lee, IS-23-15-001 Upper Port Level Cask to VV Docking Interface, IDM 2F9DR9, IO (May 2010). [5] JOST world (www.jost-world.com).
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
ARTICLE IN PRESS
FUSION-7408; No. of Pages 5
Fusion Engineering and Design xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Gripping tool for the ITER upper port plug RH extraction/insertion Elena V. Rosa ∗ , Luis Ríos Asociación Euratom-Ciemat, Avda. Comlutense 40, 28040 Madrid, Spain
h i g h l i g h t s • • • • •
The gripping tool is based on only one gripping point centred at the plug bottom. The gripping tool should allow the relative displacement in the gripping point to absorb the misalignment between plug and tractor. The gripping tool needs to withstand around 100/30 kN during the plug extraction/insertion. The gripping tool should rely on visual control and it has to avoid force feed-back. The comparison between the features of several gripping tool concepts is assessed.
a r t i c l e
i n f o
Article history: Received 12 September 2013 Received in revised form 7 February 2014 Accepted 24 March 2014 Available online xxx Keywords: ITER Upper port plug Remote handling Gripping tool Plug extraction/insertion Force feedback
a b s t r a c t The conceptual design of several gripping tools and their mechanical interfaces is being carried out for the ITER ECH UPP within the WP10-GOTRH programme. EFDA finances the GOT RH (Goal Oriented Training Programme for Remote Handling). The purpose of this paper is to introduce new concepts of gripping tools for the plug extraction/insertion in the upper port of ITER. All these gripping tools are designed according to IO input data and geometrical constraints. The gripping tools have to be able to extract/insert the plug in the scenario of maximum misalignment between the plug and the tractor. The paper also defines the functional requirements the gripping tools need to comply with. The requirements and input data are verified and validated through 3D simulation with Catia mock-ups of the gripping tools. The strengths and weaknesses of each gripping tool model are compared. © 2014 Elsevier B.V. All rights reserved.
1. Introduction This paper is centred on the development of several gripping tool (GT) concepts to carry out the plug extraction/insertion in the ITER upper port. The main components involved in each tool, as well as the design of the joint interfaces between GT and plug/tractor to absorb the misalignment between plug and tractor are described. Finally, the specific features of each GT are analyzed in order to carry out a comparison between the tools.
2. Previous works and concepts Previous works centred on the interface between UPP and Cask and Plug Remote Handling System (CPRHS) [1,2] summarize the
∗ Corresponding author. Tel.: +34 914962579. E-mail addresses: [email protected] (E.V. Rosa), [email protected] (L. Ríos).
starting point and the progress on the development of the GT concepts. The geometries of the UPP and CPRHS are given by the ITER catia model and an overview of these geometries and their interfaces can be seen in Ref. [1]. They are simplified to see easily the main parts that work in the plug extraction/insertion by the tractor (Fig. 2). According to Ref. [3], it is assumed that the plug is guided by six skids resting on the port duct rails and ramp rails of the Transfer Cask System (TCS). The rails are at an angle of 11◦ relative to the port cell floor (Fig. 2). It is assumed the maximum clearance between skids and rails is 10 mm [3] in order to absorb the 0.1◦ of misalignment between port duct and ramp rails [4]. Thus, the plug weight and tractor force are sloping and misaligned on the rails. In this environment, a previous conceptual kinematic and friction studies was carried out in [1] whose conclusions were the GT should be designed with only one gripping point (GP) centred at the bottom of the surface delimited by the flange for the UPP. The single centred connection point facilitates turning of the UPP and reduces the jamming risk during extraction/insertion. It also makes remote connection/disconnection easier and faster.
http://dx.doi.org/10.1016/j.fusengdes.2014.03.063 0920-3796/© 2014 Elsevier B.V. All rights reserved.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
G Model
ARTICLE IN PRESS
FUSION-7408; No. of Pages 5
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2
Table 1 Kinematic study results corresponding to position 1 and 3. Pos.
ϕ
˛
“y” disp.
“z” disp.
1 3
NA 0.523◦
0.423 0.423
16.5 mm 10 mm
3.9 mm 4.1 mm
Further kinematic and friction studies were developed in Ref. [2]. The Catia kinematic study simulated the plug sliding on the rails to assess the maximum clearances between skids and rails (±26.5 mm/±5 mm in “y/z” direction [2]). Thus the maximum movement of the front part of the plug centred at the bottom can be set (±16.5 mm/±5 mm in “y/z”direction, Table 1). That is the clearances in the GP (Fig. 2, “y/z”displacements). The friction study was carried out with a more conservative friction coefficient 0.3 [2] for the most misaligned positions of the plug regarding to the rails during its transference (obtained from kinematic study (ϕ, ˛), Table 1). The friction study solves the static equilibrium of forces between skids and rails for a symmetric geometry. The worst positions regarding misalignment (Table 1) correspond to position 1 (the front and rear skids rested on the port duct rails) and position 3 (the front skids rested on the port cell rails and the rear skids rested on the port duct rails). Where: ϕ is the relative angle between the plug axis and port cell rail axis, ˛ is the relative angle between the plug axis and port duct rail axis and “y/z” displacements are the relative displacements of the “plug interface” (Fig. 2) measured from the axis of the ramp rails (“tractor interface”, Fig. 2) in the y and z directions. 2.1. Kinematic and friction study conclusions The kinematic study suggests adding a curved shape to the inner walls of the skids (Fig. 1). This helps in the turning of the plug and helps to absorb the misalignments. This concept should be dimensioned and assessed by a kinematic study. However, this paper assumes the skids proposed in the ITER documentation [3]. The friction study [2] gives an approximate minimum pushing/pulling tractor force of 95 kN/20 kN. The misalignments between plug and tractor and rails do not have a severe influence on the friction forces. This is due to the fact that the misalignments are very small and due to the symmetric geometry. 2.2. Main GT requirements - Only one GP of connection, thus the balance of friction forces, tractor forces and plug weight is compensated due to the symmetric geometry around the axis that contains the GP. The GT needs to withstand around 100/30 kN during the plug extraction/insertion, respectively. - The GT should allow the relative displacement in the GP to absorb the misalignment between plug and tractor and to reduce the loads between skids and rails during the plug extraction/insertion. For that, it has been assumed a relative
Fig. 1. Suggested double curvature in the skids of the plug.
Fig. 2. Joint between plug/tractor and GT and GP (end-effector) of the GT.
displacement in the GP of ±20 mm horizontally (y) and ±5 mm vertically (z) (Table 1, Fig. 2). - The GT should work with minimum sensor onboard the TCS. Thus, the GT should rely on visual control as much as possible. Concretely, the GT has to avoid force feed-back during the tool engagement/disengagement.
2.3. Key ideas about the GT concepts The GT concept is defined by three parts: the GT part connected to the plug interface, the GP, and the GT part connected to the tractor interface (Fig. 2). The GP displacements can be managed through clearances or degrees of freedom (DoF) in the joints between the three parts of the GT defined above (Fig. 2). These joints are placed at the bottom and in the middle point of the plug and tractor and they can be rigid (–䊉–), articulated (–)–) or with clearances in “y/z” direction (). The “z” GP displacements of the tool (±5 mm) are managed through clearances for all the tools presented in the paper (from Fig. 3 to Fig. 10). This work assumes the plug GT part can be bolted manually on the plug prior to the plug RH extraction. The GTs need electromechanical actuators like stepper motors to actuate the closing system parts. All the closing systems of the GTs presented in this paper feature a back-up stepper motor for the tool recovery in case of failure of the first stepper motor. Stepper motors do not need a gearing system for speed reduction and torque multiplication, so they can be directly coupled to the shaft. This allows to avoid gearing system related failure modes (e.g. blockage). In addition, stepper motors can be used without positional feedback,. All the tools could be operated by visual control without any feedback signals from sensors if the closing system parts are sufficiently visible. In any way, the tool connection/disconnection could be executed by using visual references, such as painting marks on
Fig. 3. GT1. Tow-Hitch.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
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Fig. 5. GT2. Mushroom-Hoop.
Fig. 4. GT1. Components and DoF.
the rails and GT parts that indicate the right position to actuate the closing system. The motor command signal would also give information on the position of the closing system parts. However, if allowed by the limitations regarding the number of sensors on board the TCS, the GT connection/disconnection as well as the plug extraction/insertion could be facilitated with a force sensor that could measure the pulling/pushing force of the tractor. This information would reduce the risk of damage to the plug during connection. In addition, it would provide information about potential problems during extraction/insertion (e.g. tool jamming, skids jamming. . .). This information cannot be inferred from visual observation. 3. Gripping tools 3.1. GT1. Tow-Hitch 3.1.1. Description of the tool The Tow-Hitch gripping tool (Fig. 3) has two turning joints, one connected to the plug interface and the other in the GP, allowing the horizontal GP displacement (±20 mm). This tool uses some alignment concepts for the end-effector similar to the other commercial product made by JOST [5]. They are adapted to the ITER GT requirements for the UPP [1,2] previously summarized. The tool (Fig. 4) is composed of an articulated hitch (bolted to the plug interface) with a hole at its end. The conic structure (part of the GT part connected to the tractor interface) guides the hitch end towards the GP until it presses a trigger. The pressing of the trigger allows a stepper motor to turn a cam which makes a rod go down/up into/out of the hitch hole. The rod is prevented from moving vertically out of the hitch hole by the cam and the motor shaft (holding torque). The engagement/disengagement of the hitch is carried out in a horizontal plane. A shock absorber limits the impact loads on both plug and tractor during connection/disconnection that is carried out in the horizontal plane. When the plug is being pushed/pulled, the axial (x direction) load is taken by the hitch, rod, jacket and shock absorber structure. The cam and stepper motors are not affected by this load. The signal of the motors shows the cam position (the motor shafts is straightly connected to the cam), and are not costly components. The motors could also lock the position of the cam. The visual control of the tool operation could be helped by painting marks on the rails and hitch indicating the position at which the rod can be lowered. The motor command signal would also give information on the position of the cam (and indirectly the rod).
3.1.2. Comparative analysis The double turning joints between plug and tractor (Fig. 3) prevent the appearance of off centred loads in the tool GP. In this way the additional loads associated to torques coming from these off centred loads are avoided. This is not the case in GT2 or GT3. Because of the guidance and alignment provided to the hitch by the cone, the clearances in the gripping point between the plug part and tractor part of the gripping tool are significantly smaller than in other tool concepts such as GT2 or GT3. This limits loads coming from potential hitch movements within this clearance during extraction/insertion of the plug. From the point of view of load bearing, this gripping tool isolates the structural components (hitch, rod, jacket) from the rod actuators (cam, motors shaft). This reduces the dimensioning and risk of failure of the shaft, bearings and motors that actuate the cam. This is a difference with GT2. The tool engagement/disengagement (hitch into/out of cone) and the fastener (rod) movements are carried out in different planes (horizontal/vertical). This prevents the accidental release of the plug (for example, during seismic events). 3.2. GT2. Mushroom-Hoop 3.2.1. Description of the tool The Mushroom-Hoop gripping tool (Fig. 5) is composed by a mushroom grip, one hoop as end-effector and two stepper motors that turn and lock the hoop. The horizontal GP displacements (±20 mm) are managed by clearances in the hoop (tool GP) and rigid joints in the GT-plug and GT-tractor interfaces (Fig. 6). The tool does not need GP alignment. The tool connection/disconnection is carried out in the vertical plane through the hoop turning.
Fig. 6. GT2. DoF and clearances.
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Fig. 7. GT3. Twist-Lock.
The mushroom shape of the grip prevents the GT disconnection. The wider rear part of the hoop allows to introduce the mushroom head into the hoop. The narrower hoop front part allows only for the required clearances in the GP. The tractor has to do a forward/backward movement in order to reach the GT connection/disconnection position. The closing system is composed by two stepper motors and the hoop. The motor shafts are straightly connected to the hoop turning shaft. The stepper motors are used without position feedback so the signal of the motors indicates the hoop position. They could also be used to lock the hoop position during insertion/extraction of the UPP (holding torque). The tool operation could rely exclusively on visual control with the aid of painted marks. 3.2.2. Comparative analysis Contrary to GT1 and GT4, the clearances in the GP of GT2 allow the free movement of the mushroom grip inside the hoop. This can produce off centred transference of the load that may lead to larger dimensioning of the tool and tractor structure. The misalignments are small, though, so the impact on the dimensioning may be limited. Because of the higher clearance between the tractor and plug parts of the gripping tool, the loads coming from mushroom grip movements within this clearance during extraction/insertion or seismic event will be higher than those expected in GT1 or GT4. Contrary to the other tools, GT2 does not feature a shock absorber to reduce loads during the tool engagement/disengagement due to the fact that the tractor does not need to push the tool to be connected (it is carried out in the vertical plane). The tool dimensioning would need to take into account these dynamic loads. The design could be adapted to include a shock absorber if needed, though. Contrary to GT1 or GT4, the stepper motors shaft, coupled in GT2 to the hoop, will see loads during insertion and extraction of the plug. The bearings on the shaft would need to be dimensioned to take this radial load. The mushroom shape of the grip prevents the accidental release of the plug limiting vertical hoop movement. If the motors are active during extraction/insertion of the plug, they will apply a holding torque acting against an accidental lifting of the hoop. This tool presents the advantage of having an, in principle, simpler design than that of the other tools presented. 3.3. GT3. Twist Lock 3.3.1. Description of the tool The Twist-Lock gripping tool (Fig. 7 and Fig. 8) has the following design features:
Fig. 8. GT3. Components.
A cavity placed in the tool part connected to the plug interface. The twistlock is inserted through a slotted hole in the cavity and then turned to lock (the turning is contained in the “yz” plane). The cavity has enough clearances to absorb the relative displacements between twistlock and cavity appearing during insertion/extraction of the plug (see Table 1). The twist-lock shaft is connected to two stepper motors. The axial load is transferred from the shaft to the tool body structure by a stop feature in the shaft. An articulated joint (tractor interface joint, Fig. 2) allows for some turning of the twistlock supporting structure (Fig. 7). The tractor interface joint is composed by a pin ball, allowing the turning of the whole twistlock supporting structure, and several springs that keep the twistlock supporting structure straight when inserting/extracting the twistlock through the slotted hole into/out of the cavity (Fig. 8). The pin ball increases the contact between the twistlock and twistlock cavity surfaces during extraction/insertion and the springs allow the twistlock and twistlock cavity to be better aligned during tool connection/disconnection. The tool operation could be carried out by visual control and painting marks on the rails and the twist-lock shaft. 3.3.2. Comparative analysis This tool presents the same issues as GT2 regarding clearances in the GP leading to off centred transference of load and dynamic loads coming from relative movements in the GP during plug extraction/insertion. Contrary to GT2, the tool engagement/disengagement (horizontal) and the fastener movement (rotation) are carried out in different planes (horizontal/vertical). This prevents the possibility of accidental plug release. 3.4. GT4. Pin-Plate 3.4.1. Description of the tool The Pin-Plate gripping tool (Fig. 9) uses similar alignment concepts to the commercial tool [5].These concepts are adapted to the ITER GT requirements for the UPP [1,2] that are summarized in Section 2. The horizontal GP displacements (±20 mm) are managed through two turning joints and one rigid joint (Fig. 9). The Mushroom pin-plate tool is comprised of the parts shown in Fig. 10. The mushroom grip is guided by a wedge shaped feature in the plate to the GP. When the mushroom grip is in the GP, a stepper motor turns a cam and the rod moves horizontally, locking the mushroom grip.
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063
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rod movement in “y” direction that could release the plug. Contrary to GT1, the rod movement is horizontal instead of vertical (design potentially needing more attention to ensure proper functioning and prevent jamming). Similarly to GT1, The tool isolates structurally the rod actuator components (motor and cam) of the load bearing components (rod, plate, mushroom grip) to prevent load transference to the motor shaft. 3.5. Conclusions
Fig. 9. GT4. Mushroom pin-plate.
Fig. 10. GT4. Components and DoF.
A shock absorber limits the impact loads on both UPP and tractor during connection/disconnection due to the tool engagement/disengagement is carried out in the horizontal plane. The locking of the rod in “y” direction (rod axis) is ensured by the holding torque of the motor. This tool features a good visual control for the operations. 3.4.2. Comparative analysis This tool is similar to GT1 regarding the use of a double articulated joint and the absence of clearances in the GP preventing off centred transference of load and dynamic loads coming from relative movements in the GP during plug extraction/insertion. The tool engagement/disengagement (x) and the fastener movement (y) are carried out in the same plane (horizontal). Similarly to GT2, the mushroom shape of the grip prevents the accidental release of the plug by limiting vertical movement of either tractor or plug. The locking action of the motors prevents the accidental
The double turning joints between plug and tractor (GT1 and GT4) reduce the loading on the tool structure and lead to smaller dimensioning. However, the clearances between plug and tractor (GT2 and GT3) avoid the need for tool GP alignment. The accidental release of the plug is better avoided when the tool engagement/disengagement and the fastener movement are carried out in different planes. The vertical movement of the fastener has the advantages of facilitating the engagement and also reducing the risk of plug release. All the GT can be connected/disconnected relying exclusively on visual control. The installation of a force sensor would provide a valuable information impossible to obtain visually that would facilitate the RH connection/disconnection operation. The shock absorber is not required for the tool connection/disconnection. However, it is recommended for those tools for which connection/disconnection is carried out in the horizontal plane (GT1, 3 and 4), as it will limit the loads on plug and tractor. The shock absorber could be installed in all the concepts of tools to limit loads as well during its transference. Acknowledgments This work was carried out under the EFDA Goal Oriented Training Programme (WP10-GOT- GOTRH) and financial support of Ciemat, which are greatly acknowledged. The views and opinions expressed herein do not necessarily reflect those of the European Commission. References [1] E. Rosa, L. Rios, V. Queral, Progress on the interface between UPP and CPRHS tractor/gripping tool for ITER, Fusion Eng. Des. 88 (2013) 2168–2172. [2] E. Rosa, Review Meeting Presentation, Ciemat (March 2013). http://labfus. ciemat.es/AR/2012/CAP4/GOT 2.pdf [3] B. Levesy, Port Plug Handling, IDM PCR-439, IO (June 2012). [4] A. Tesini, J. Preble, J.-J.Cordier, C. Hyung Lee, IS-23-15-001 Upper Port Level Cask to VV Docking Interface, IDM 2F9DR9, IO (May 2010). [5] JOST world (www.jost-world.com).
Please cite this article in press as: E.V. Rosa, L. Ríos, Gripping tool for the ITER upper port plug RH extraction/insertion, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.063