Robotic arm and system and method for installing the same

Abstract

Robotic arm for subsea use is disclosed, comprising a base (100); a first arm (200) comprising a first end (210) rotatably connected to the base (100) for rotation around a first rotational degree of freedom (R1), and a second end (220) opposite the first end (210); a second arm (300) comprising a third end (310) rotatably connected to the second end (220) for rotation around a second rotational degree of freedom (R2) parallel to the first rotational degree of freedom (R1), and a fourth end (320) opposite the third end (310) of the second arm (300); an end effector (400) connected to the fourth end (320) for rotation around a third rotational degree of freedom (R3) being parallel to the second rotational degree of freedom (R2); and wherein the first arm (200) and the second arm (300) are configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm. A system and method with the same are also disclosed.

Description

[0001] ROBOTIC ARM AND SYSTEM AND METHOD FOR INSTALLING THE SAME

[0002] Technical Field

[0003] The present disclosure relates generally to the field of robotic arm used subsea mainly in the oil and gas industry. More specifically, the present disclosure describes a robotic arm for subsea use, and a system and method for installing the same.

[0004] Background

[0005] Robotic arms are used to support operations on subsea devices. The robotic arms can be used with subsea devices such as manifolds, trees, pumps, and blowout preventers. Robotic arms for manipulating devices subsea are know from EP3165709B1 and EP3296505B1.

[0006] It is a problem to provide a robotic arm that has a long reach and at the same time has a topology that can assure position accuracy and transmission of forces. A problem is moving the robotic arm through the splash zone when installing or uninstalling the robotic arm subsea. The waves, water, wind, etc. tend to separate and open up the robotic links when moved through the splash zone. This may result in damage to the robotic arm, failure to properly install the robotic arm, or even loss of the robotic arm. A further problem is the uneven weight distribution of the robotic arm. These problems make installation or uninstallation very difficult, time consuming, and costly. A robotic arm is sensitive to impacts. For example, jumpers and wires, or the robotic links themselves, can easily be damaged by external forces. A further problem is how to store the robotic arm when not in use, and how to avoid damages to a robotic arm when not in use and / or transported.

[0007] It is desirable to provide a robotic arm for subsea use that addresses these problems, is inexpensive to manufacture, is easy to manufacture and assemble, and is robust and reliable. The robotic arm should be easy to move through the splash zone and also be able to provide a good and reliable operation of the well equipment. The present disclosure is directed to overcoming one or more of the problems as set forth above.

[0008] SUMMARY

[0009] It is an objective of the present invention to provide a robotic arm for subsea use, and a system and method for installing the same. This objective can be achieved by the features as defined by the independent claims. Further enhancements are characterized by the dependent claims. The invention is defined by the claims.

[0010] According to a first embodiment, there is provided a robotic arm for subsea use. The robotic arm comprises a base 100; a first arm 200 comprising a first end 210 rotatably connected to the base 100 for rotation around a first rotational degree of freedom R1, and a second end 220 opposite the first end 210; a second arm 300 comprising a third end 310 rotatably connected to the second end 220 for rotation around a second rotational degree of freedom R2 parallel to the first rotational degree of freedom R1, and a fourth end 320 opposite the third end 310 of the second arm 300; and an end effector 400 connected to the fourth end 320 for rotation around a third rotational degree of freedom R3 being parallel to the second rotational degree of freedom R2. The first arm 200 and the second arm 300 are configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm. A major part is at least half or more. At least a major part of the first or second arms 200, 300 or of the end effector 400 is to be understood to be at least half the first or second arms 200, 300 or at least half the end effector 400, and preferably at least three quarters, and preferably substantially all. The base 100 may comprise one or more attachment means 130 for lifting the robotic arm.

[0011] The second arm 300 and the end effector 400 may be configured to have complimentary shapes to allow at least a major part of the end effector 400 to fold in to the second arm 300 such that when they are folded together at least a major part of the end effector 400 may be positioned within the outer boundary of the second arm 300.

[0012] The first arm 200 may further comprises two first arm side supports 230, 232 each arranged from the first end 210 to the second end 220, the two first arm side supports 230, 232 may be spaced apart to form a first opening 234 between them, the first opening 234 allowing at least a major part of the second arm 300 to be folded into the first opening 234. The second arm 300 may further comprises two second arm side supports 330, 332 each arranged from the third end 310 to the fourth end 320, the two second arm side supports 330, 332 may be spaced apart to form a second opening 334 between them, the second opening 334 allowing at least a major part of the end effector 400 to be folded into the second opening 334. The robotic arm may be configured to have a mass centre lying on a vertical plane going through two attachment means 130, when the first arm 200, the second arm 300, and the end effector 400 are folded together. In one embodiment the end effector 400 may fold in one direction into the second arm 300, the second arm 300 may fold in the same direction into the first arm 200, and the first arm 200 may fold flat onto the base 100 in the opposite direction.

[0013] According to one embodiment, a system for installing a robotic arm is disclosed. The system comprises the robotic arm with the attachment means 130, and a gripper 500 for engaging the one or more attachment means 130 for lifting the robotic arm, the gripper 500 being configured for preventing the first arm 200, the second arm 300, and the end effector 400 to unfold.

[0014] According to a one embodiment, there is provided a method for installing a robotic arm subsea. The method comprises the following steps in any order: providing 710 the system mentioned herein; folding 720 the robotic arm together; attaching 730 the gripper 500 to the base 100 and thereby holding the robotic arm folded together; and moving 740 the robotic arm and the gripper trough a splash zone for installing or uninstalling the robotic arm subsea. The method may also comprise having the robotic arm folded together during installing or during uninstalling the robotic arm subsea. The method may also comprise keeping the robotic arm folded together when not in use.

[0015] At least one of the above embodiments provides one or more solutions to the problems and disadvantages with the background art. Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following description and claims. Various embodiments of the present application obtain only a subset of the advantages set forth. No one advantage is critical to the embodiments. Any claimed embodiment may be technically combined with any other claimed embodiment or embodiments.

[0016] Brief Description of the Drawings

[0017] The disclosure will be further described with reference to examples depicted in the accompanying figures in which:

[0018] FIG 1 is a schematic illustration of a robotic arm and a base according to one embodiment, where the first arm 200, the second arm 300, and the end effector 400 are unfolded; FIG 2 is a schematic illustration of a robotic arm and a base according to one embodiment, where the first arm 200, the second arm 300 are unfolded, and the end effector 400 is folded into the second arm 300;

[0019] FIG 3 is a schematic illustration of a robotic arm and a base according to one embodiment, where the first arm 200 is unfolded, and the second arm 300 and the end effector 400 are folded into the first arm 200;

[0020] FIG 4 is a schematic illustration of a robotic arm and a base according to one embodiment, where the first arm 200 is folded onto the base 100, and the second arm 300 and the end effector 400 are folded into the first arm 200; and

[0021] FIG 5 is a schematic illustration of a method according to an embodiment.

[0022] Detailed Description

[0023] Embodiments of the present invention provide a robotic arm and a system and method for installing and uninstalling the robotic arm. This detailed description describes in detail at least one way of carrying out the claimed invention by referring to the drawings. Figures 1 to 4 illustrates the unfolded robotic arm in figure 1 and how the robotic arm may be folded together in figures 2 to 4. Figure 4 showing the robotic arm folded together and flat of the base robotic arm. In Figure 4 a gripper for transporting the robotic arm is schematically illustrated in dotted lines. Figure 5 illustrates the method of installing the robotic arm from above the sea surface to an installed position subsea.

[0024] Figure 1 illustrates a robotic arm for subsea use. The robotic arm comprises a base 100, a first arm 200, a second arm 300, and an end effector 400. The first arm 200 comprises a first end 210 rotatably connected to the base 100 for rotation around a first rotational degree of freedom R1 , and a second end 220 opposite the first end 210. The second arm 300 comprises a third end 310 rotatably connected to the second end 220 for rotation around a second rotational degree of freedom R2 parallel to the first rotational degree of freedom R1, and a fourth end 320 opposite the third end 310 of the second arm 300. The end effector 400 is connected to the fourth end 320 for rotation around a third rotational degree of freedom R3 being parallel to the second rotational degree of freedom R2. The first arm 200 and the second arm 300 are configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm. For example, the second arm 300 may fold into the first arm 100. This movement is best shown from figure 2 to figure 3, where the second arm 300 rotates around the second rotational degree of freedom R2. At least a major part of one of the arms is to be understood to be at least half the arm. Preferably at least three quarters, and preferably substantially all of the arm is positioned within the outer boundary of the other arm. As illustrated in figure 3 more than half the second arm 300 is within the outer boundary of the first arm 200. In figure 3 substantially all of the second arm 300 is within the outer boundary of the first arm 200. In figure 3 the second arm 300 is aligned with the first arm 200, they are adjusted in a straight line with each other, the second arm 300 being inside the other arm. The second arm 300 is folded into the first arm 200 such that the second arm 300 is protected by the first arm 200, for example when stored or transported through the splash zone.

[0025] The base 100 may be suitable for being installed subsea to a manifold, a tree, a blowout preventer, a pump, or any other equipment subsea. The robotic arm may allow to perform operations such as, for example, opening / closing a valve, making a connection, switching a lever, etc. The base 100 may comprise an elongate part that can be placed in an opening, for example a funnel, of the subsea equipment. In this way the base 100 with the robotic arm may be installed on, for example, a manifold. The base 100 may provide a fourth rotational degree of freedom R4. The fourth rotational degree of freedom R4 may be along an axis of the elongate part as illustrated in figure 2, and may be perpendicular to the first rotational degree of freedom R1. The first arm 200 may be the first link in the robotic arm and may be connected to the base 100 for rotation around the first rotational degree of freedom R1. The first arm 200 may be attached for rotation at an outer side, the periphery, of the base 100, for the purpose of extending the reach of the robotic arm. The first arm 200, the second arm 300, and the end effector 400 may form the robotic arm as three links, like three chain links, with the first, second, and third rotational degrees of freedom R1, R2, and R3 being all parallel to each other and perpendicular to the fourth rotational degree of freedom R4. The second arm 300 may be arranged between the first arm 200 and the end effector 400. The end effector 400 may be the last link of the robotic arm. The arms 200, 300 may be straight arms. The end effector 400 may carry a tool, such as for example a gripper or a torque tool.

[0026] Means may be used for the purpose of rotatably connect for rotation around a rotational degree of freedom as mentioned herein, and may for example be an electric motor. The means for rotation rotates the arms and / or the end effector in relation to the base. These rotations can be controlled for the purpose of the robotic arm to move.

[0027] The second arm 300 and the end effector 400 may be configured to have complimentary shapes to allow at least a major part of the end effector 400 to fold, for example by rotation around the third rotational degree of freedom R3, in to the second arm 300 such that when they are folded together at least a major part of the end effector 400 is positioned within the outer boundary of the second arm 300. At least a major part of one of the end effector 400 is to be understood to be at least half the end effector 400. Preferably at least three quarters, and preferably substantially all of the end effector 400 is positioned within the outer boundary of the second arm 300. As illustrated in figures 2 to 4 more than half the end effector 400 is within the outer boundary of the second arm 300. As may best be taken from figures 1 to 4 the end effector 400 and the second arm 300 may both fold in to the first arm 200 such that when they are all three folded together they are aligned with each other, the second arm 300 and the end effector 400 may be substantially inside the first arm 200, or at least a major part of both the second arm 300 and the end effector 400 may be substantially inside the first arm 200.

[0028] The first arm 200 may further comprise two first arm side supports 230, 232. Each side support 230, 232 may be arranged from the first end 210 to the second end 220 of the first arm 200. The two side supports may make up the length of the first arm 200. The two first arm side supports 230, 232 may be spaced apart to form a first opening 234 between them. The first opening 234 may allow at least a major part of the second arm 300 to be folded into the first opening 234. The second arm 300 may be substantially within the first opening 234. The two side supports 230, 232 may form sides of the outer boundary of the first arm 200. The first arm 200 may be longer and wider than the second arm 300 such that the first opening 234 can accommodate the second arm 300, or at least a major part of the second arm 300.

[0029] The second arm 300 may further comprise two second arm side supports 330, 332. Each side supports 330, 332 may be arranged from the third end 310 to the fourth end 320 of the second arm 300. The two second arm side supports 330, 332 may be spaced apart to form a second opening 334 between them. The second opening 334 may allow at least a major part of the end effector 400 to be folded into the second opening 334. The end effector 400 may be substantially within the second opening 334. The two side supports 330, 332 may form sides of the outer boundary of the second arm 300. The second arm 300 may be longer and wider than the end effector 400 such that the second opening 334 can accommodate the end effector 400, or at least a major part of the end effector 400.

[0030] Each of the two first arm side supports 230, 232 may be rotatably connected to one of the two second arm side supports 330, 332, respectively. The robotic arms are sturdy when having two rotatable connections supporting the rotations around the first, second, and third rotational degrees of freedom R1, R2, and R3. In between the two connections a motor for rotating the arms may be provided.

[0031] The second arm 300 may further comprise a panel 340 extending between, and connecting opposite side edges of, the two second arm side supports 330, 332. The panel 340 may be arranged on an outer side when the second arm is folded in to the first arm. This is best illustrated in figures 1 and 2. The panel 340 may be arranged such that when the end effector 400 and the second arm 300 are both folded in to the first arm 200, and the first arm 200 is folded onto the base 100, then the panel 340 is facing upwards, as illustrated best in figure 4. In figure 3 the end effector 400 is between the panel 340 and the base 100. In this folded position the panel 340 protects the end effector 400. The panel 340 and the two second arm side supports 330, 332 may form three sides of the second opening 334.

[0032] One or more of the two first arm side supports 230, 232 and the two second arm side supports 330, 332 may comprise wirings for the robotic arm. The wiring may include power cables and / or control cables. The wiring may be completely inside the arms to avoid that the wiring can be damaged during use or when stored or when transported through the splash zone. One or more of the two first arm side supports 230, 232 and the two second arm side supports 330, 332 may comprise one or more anodes 236 for protecting the robotic arm against deteriorating.

[0033] The base 100 may comprise a male connector 120 for connecting the robotic arm subsea in its working position. The male connector 120 may be a protrusion that fits an opening where the robotic arm is going to be installed, for example a funnel on a manifold. The robotic arm may be held in position by only its own weight and the male connector 120 entering a female connector, for example a key and a slot. No further element may be necessary to fix the robotic arm to the subsea equipment. The elongate part of the base 100 may be inserted into an opening of the subsea equipment. The base 100 may comprise, instead or in addition, a female connector for a male connector in its working position. The use of only a male connector 120 and a female connector to position and keep the robotic arm in place may be sufficient, and not require any additional means, for holding the robotic arm in place.

[0034] The base 100 may comprise one or more attachment means 130 for lifting the robotic arm. Preferably there may be two attachment means 130, one on each side of the base 100, preferably on the same sides as the one or more of the two first arm side supports 230, 232 and the two second arm side supports 330, 332. The attachment means may be, for example openings, means suitable for a gripper 500 to connect to. The gripper 500 is described in more detail herein. The one or more attachment means 130 allows the robotic arm to be lifted, transported, and installed. In the figures 1 to 4 only one of the attachment means 130 is visible, preferably a second one is opposite on the other side of the base 100. As may best be taken from figure 4, a U-shaped gripper 500 may attach to two attachment means 130 opposite each other.

[0035] The base 100 comprises means 110 for rotating the base 100 around a fourth rotational degree of freedom R4 perpendicular to the first rotational degree of freedom R1. The means 110 may be a swivel. The means 110 may allow the first arm 200, the second arm 300, and the end effector 400 to be rotated perpendicular to the first, second, and third rotational degrees of freedom R1, R2, R3.

[0036] The end effector 400 may comprise a flexible element 410 allowing the end effector 400 to rotate around a fifth rotational degree of freedom R5 perpendicular to the third rotational degree of freedom R3. The fifth rotational degree of freedom R5 may also, or alternatively, be perpendicular to a sixth rotational degree of freedom R6. The flexible element 410 may, for example, be a torsion bar allowing the base to rotate, for example allowing 5-10 degrees flexibility, around the fifth rotational degree of freedom R5. The flexible element 410 may, for example, be a spring or a gimbal. This flexibility allows the end effector 400 to align with its working position. The fifth rotational degree of freedom R5 may be passive, that is there may not be any drive means for rotation around the fifth rotational degree of freedom R5, instead the flexible element 410 may allow the robotic arm to be flexible. The flexibility may be plus / minus 5 to 10 degrees. As an alternative, or addition, hereto, the base 100 may comprise a flexible element allowing the base 100 to rotate around a further rotational degree of freedom perpendicular to the first rotational degree of freedom R1. The fifth rotational degree of freedom R5 may also be perpendicular to the fourth rotational degree of freedom R4. The end effector 400 may further comprise rotational means 450 for rotating an end of the end effector, or a tool attached to the end effector, around a sixth rotational degree of freedom R6 being perpendicular to the third rotational degree of freedom R3. The end effector 400 may further comprise additional rotational means for rotating the end around a further rotational degree of freedom being perpendicular to the sixth rotational degree of freedom R6 and the third rotational degree of freedom R3.

[0037] The robotic arm may be configured to have a mass centre lying on a vertical plane going through two attachment means 130, when the first arm 200, the second arm 300, and the end effector 400 are folded together, preferably folded together and lying on the base 100, as best illustrated in figure 4. The mass centre may be lying on a straight line between two attachment means 130. This improves the robotic arm’s possibility to be handled in a safe manner without tipping over and possibility to be transported through the splash zone. The mass centre is in this case very similar to the centre of gravity. The mass centres of the base 100, the first arm 200, the second arm 300, the end effector 400, when folded together onto the base 100 may be close to each other, and the combined mass centre hereof may be lying in a vertical plane that goes through the two attachment means 130. The plane may extend in the direction of the fourth rotational degree of freedom R4.

[0038] The end effector 400 may fold in one direction into the second arm 300, the second arm 300 may fold in the same direction into the first arm 200, and the first arm 200 may fold flat onto the base 100 in the opposite direction. This may provide a safe and secure way to lock the robotic arm in the folded position, as best illustrated in figure 4. This may also allow the panel 340 to end up in the folded position facing upwards in figure 4 and this may protect the robotic arm and its components.

[0039] The first arm 200 is preferably longer, wider, and higher than the second arm 300; and the second arm 300 is preferably longer and wider than the end effector 400. The first opening 234 may be a substantially hollow rectangular cuboid, a hollow rectangular parallelepiped, formed by the rotational connections, the side supports 230, 232, and optionally a panel, each on one side and the last side open for the second arm 300 to fold into. The second opening 334 may be a substantially hollow rectangular cuboid, a hollow rectangular parallelepiped, formed by the rotational connections, the side supports 330, 332, and a panel 340, each on one side and the last side open for the end effector 400 to fold into. The first arm 200 may further comprise a panel extending between the two first arm side supports 230, 232, correspondingly to the panel 340. A bar may be arranged in the ends of the arms, at least partly around the rotational joints, and may protect the joints of the arms from impact when moving and in the folded position.

[0040] According to one embodiment, a system for installing the robotic arm, according to any one of the embodiments disclosed herein, is described. The system comprises any embodiment of the robotic arm with the one or more attachment means 130. The system further comprises a gripper 500 for engaging the one or more attachment means 130 for lifting the robotic arm, the gripper 500 being configured for preventing the first arm 200, the second arm 300, and the end effector 400 to unfold. This may best be taken from figure 4 where the gripper 500 has been schematically illustrated in dotted lines. The gripper 500 may be configured for holding, engaging, one or more of the first arm 200, the second arm 300, and the end effector 400 to keep the robotic arm folded together when the gripper 500 is attached to the base 100. The gripper 500 may be configured for engaging the first arm 200, with the second arm 300 and the end effector 400 substantially folded inside the first arm 200. The gripper 500 may be configured for clamping the first arm 200, with the second arm 300 and the end effector 400 substantially folded inside the first arm 200, between the gripper 500 and the base 100, thereby limiting, preventing, the first arm 200 to move, unfold, relative to the base 100 where the attachment means 130 are. This provides a simple yet effective way of handling the folded robotic arm with the gripper 500 and ensuring that the robotic arm cannot unfold when, for example, being moved through the splash zone.

[0041] A method for installing a robotic arm subsea is disclosed. The method comprises the following steps in any order: providing 710 a system as described herein; folding 720 the robotic arm together; attaching 730 the gripper 500 to the base 100 and thereby holding the robotic arm folded together; moving 740 the robotic arm and the gripper 500 through a splash zone for installing or uninstalling the robotic arm subsea. This is best illustrated in figures 4 and 5. The system may be the gripper 500 and any embodiment of the robotic arm mentioned herein. The method may also comprise having the robotic arm folded together during installing or uninstalling the robotic arm subsea. The method may also comprise keeping the robotic arm folded together when not in use. This protects the robotic arm.

[0042] With a system comprising the gripper 500 and the robotic arm as described herein, the robotic arm may be folded together as described herein and best shown in figure 4 where the end effector 400 and the second arm 300 are folded into the first arm 200, and the first arm 200 is folded onto the base 100. The gripper 500 may be attached to two of the attachment means 130 of the base 100 and, as illustrated in figure 4, hold the end effector 400 and the second arm 300 folded in the first arm 200 between the gripper 500 and the base 100. In this way the gripper 500 can move the robotic arm through the splash zone ensuring that the robotic arm does not unfold due to the water, waves and wind in the splash zone. The Gripper 500 may move the robotic arm to an equipment subsea, for example a manifold. There the gripper 500 may lower the robotic arm into an opening of the subsea equipment and thereby install the robotic arm. Uninstalling the robotic arm may be made in the reverse order. The preference is to have the robotic arm in the folded position when not in use, and held in the folded position by the gripper 500 when moved.

[0043] It will be apparent to those skilled in the art that various modifications and variations can be made to the robotic arm, the system and the method for installing a robotic arm subsea. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and method. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

Claims1 Robotic arm for subsea use, comprising a base (100); a first arm (200) comprising a first end (210) rotatably connected to the base (100) for rotation around a first rotational degree of freedom (R1), and a second end (220) opposite the first end (210); a second arm (300) comprising a third end (310) rotatably connected to the second end (220) for rotation around a second rotational degree of freedom (R2) parallel to the first rotational degree of freedom (R1), and a fourth end (320) opposite the third end (310) of the second arm (300); an end effector (400) connected to the fourth end (320) for rotation around a third rotational degree of freedom (R3) being parallel to the second rotational degree of freedom (R2); and wherein the first arm (200) and the second arm (300) are configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm.2 The robotic arm according to claim 1, wherein the second arm (300) and the end effector (400) are configured to have complimentary shapes to allow at least a major part of the end effector (400) to fold in to the second arm (300) such that when they are folded together at least a major part of the end effector (400) is positioned within the outer boundary of the second arm (300).3 The robotic arm according to claim 1 or 2, wherein the first arm (200) further comprises two first arm side supports (230, 232) each arranged from the first end (210) to the second end (220), the two first arm side supports (230, 232) being spaced apart to form a first opening (234) between them, the first opening (234) allowing at least a major part of the second arm (300) to be folded into the first opening (234); and wherein the second arm (300) further comprises two second arm side supports (330, 332) each arranged from the third end (310) to the fourth end (320), the two second arm side supports (330, 332) being spaced apart to form a secondopening (334) between them, the second opening (334) allowing at least a major part of the end effector (400) to be folded into the second opening (334).4 The robotic arm according to claim 3, wherein the second arm (300) further comprises a panel (340) extending between, and connecting opposite side edges of, the two second arm side supports (330, 332).5 The robotic arm according to claim 3, wherein one or more of the two first arm side supports (230, 232) and the two second arm side supports (330, 332) comprise wirings for the robotic arm.6 The robotic arm according to any one of the preceding claims, wherein the base (100) comprises a male connector (120) for connecting the robotic arm subsea in its working position.7 The robotic arm according to any one of the preceding claims, wherein the base (100) comprises one or more attachment means (130) for lifting the robotic arm.8 The robotic arm according to any one of the preceding claims, wherein the base (100) comprises means (110) for rotating the base (100) around a fourth rotational degree of freedom (R4) perpendicular to the first rotational degree of freedom (R1).9 The robotic arm according to any one of the preceding claims, wherein the end effector (400) comprises a flexible element (410) allowing the end effector (400) to rotate around a fifth rotational degree of freedom (R5) perpendicular to the third rotational degree of freedom (R3).10 The robotic arm according to any one of the preceding claims, wherein the end effector (400) further comprising rotational means (450) for rotating an end of the end effector around a sixth rotational degree of freedom (R6) being perpendicular to the third rotational degree of freedom (R3).11 The robotic arm according to claim 7, wherein the robotic arm is configured to have a mass centre lying on a vertical plane going through the two attachment means (130), when the first arm (200), the second arm (300), and the end effector (400) are folded together.12 The robotic arm according to any one of the preceding claims, wherein the end effector (400) folds in one direction into the second arm (300), the second arm (300) folds in the same direction into the first arm (200), and the first arm (200) folds flat onto the base (100) in the opposite direction.13 A system for installing a robotic arm, the system comprising the robotic arm according to claim 7 or 11 and further comprising a gripper (500) for engaging the one or more attachment means (130) for lifting the robotic arm, the gripper (500) being configured for preventing the first arm (200), the second arm (300), and the end effector (400) to unfold.14 A method for installing a robotic arm subsea, the method comprising the following steps in any order: providing (710) a system according to claim 13; folding (720) the robotic arm together; attaching (730) the gripper (500) to the base (100) and thereby holding the robotic arm folded together; moving (740) the robotic arm and the gripper trough a splash zone for installing or uninstalling the robotic arm subsea.15 The method according to claim 1 , wherein the robotic arm is folded together during installing or uninstalling the robotic arm subsea and kept folded together when not in use.

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