Rigid parallel robot
The parallel robot design addresses torsional rigidity issues in radially constrained spaces by using pivot joints and controlled movements, ensuring precise operations in environments like pipe interiors.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
- Filing Date
- 2025-12-08
- Publication Date
- 2026-06-12
AI Technical Summary
Conventional parallel robotic architectures face issues with insufficient torsional rigidity when deployed in radially constrained environments, such as inside pipes, leading to inaccuracies in operations requiring radially directed forces.
A parallel robot design featuring a first and second frame connected by pivot joints, with a mobile platform connected by connecting rods and displacement elements, allowing for orthogonal pivot joints and controlled movements to maintain rigidity and precision in radially restricted spaces.
The design ensures sufficient rigidity to withstand radially directed forces, enabling precise operations like pipe milling with reduced play and flexibility, maintaining accuracy and stability in challenging environments.
Smart Images
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Abstract
Description
Title of the invention: Rigid parallel robot technical field
[0001] The present invention relates to the field of robotics and more specifically to the field of parallel robots, also called parallel robotic architectures. Its particularly advantageous application lies in the field of machining performed by a parallel robotic architecture in a difficult-to-access environment, particularly with limited radial space, such as the internal renovation of piping. STATE OF THE ART
[0002] There are various parallel robotic architectures that can be used in restricted environments such as the renovation of the inside of pipes.
[0003] Generally, parallel architectures are robotic machines composed of several independent kinematic chains, usually telescopic actuators articulated at their two ends on a frame and a mobile platform.
[0004] A conventional robot of this type is described in US patent 4732525. The robot comprises three adjustment devices, in combination with a central tube that carries a positioning head at one end. The central tube provides three degrees of freedom relative to the machine base. Each adjustment device is connected to the positioning head by a three-degree-of-freedom joint and to the machine base by a two-degree-of-freedom joint, so as to allow the positioning head to move within a limited working range.
[0005] This type of robot allows complex movements to be performed.
[0006] However, for applications involving the robot's engagement in an environment whose geometry is radially constrained (such as the inside of a pipe, especially if the pipe diameter is small) the torsional rigidity of the robot may be insufficient to guarantee the accuracy of the operations carried out by the robot.
[0007] This is particularly true when the robot has to be deployed along the length of the inside of a pipe (or generally of a radially constrained environment), and perform operations by its actuator involving radially directed forces (for example: milling the internal wall of the pipe).
[0008] An object of the present invention is therefore to propose a solution improving the accuracy of machining carried out in a cluttered environment, in particular a radially restricted environment.
[0009] The other objects, features and advantages of the present invention will become apparent from an examination of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY
[0010] To achieve this objective, according to one embodiment, a parallel robot extending along a main longitudinal axis is provided, characterized in that it comprises: • a first structure extending along the main longitudinal axis, • a second frame mounted on the first frame with a pivot joint along the main longitudinal axis, • a mobile platform connected to the second frame by a first connecting rod, a second connecting rod and a third connecting rod, each connecting rod being articulated at one end on the second frame and at the other end on the mobile platform, • a first displacement element and a second displacement element, the first displacement element being connected by a pivot joint to the first end of the first connecting rod and also being connected by a sliding joint to the second frame, and the second displacement element being connected by a pivot joint to the first end of the second connecting rod and also being connected by a sliding joint to the second frame, each of said sliding joints being configured to allow translation of the first end of the first connecting rod and of the second connecting rod parallel to the main longitudinal axis, the respective second ends of the first and second connecting rods each being articulated on the moving platform by a respective pivot joint and connected to at least one connecting element fixed on said platform, the third connecting rod being connected by its first end by a pivot joint to one of the first or second moving element and by a pivot joint of its second end to a connecting element of the moving platform, each pivot joint having an axis of rotation, the axes of rotation of the pivot joints of the first, second and third connecting rods all being parallel to each other and orthogonal to the main longitudinal axis such that the displacement of the first and second moving elements allows the moving platform to be moved in a plane which includes the main longitudinal axis and whose normal is parallel to the axes of rotation of the pivot joints of the first,second and third connecting rods, and the displacement of the second frame relative to the first frame, allowing the mobile platform to rotate in a plane orthogonal to the main longitudinal axis, relative to the first frame.
[0011] Thus, the invention proposes a solution for conducting an interview in a space restricted. More specifically, the invention proposes a solution with sufficient rigidity to withstand radially directed forces, even when the invention is deployed in a longitudinal direction. The invention thus enables internal pipe maintenance while maintaining sufficient rigidity to perform this operation precisely.
[0012] The use of pivots whose axes are orthogonal to the longitudinal axis, rather than ball joints / half-cardan joints (a technological constraint implied by the architectural choices of many parallel systems), at the level of the articulated mechanical system ensures good rigidity. The proposed invention also has the advantage of having fewer joints than many of the parallel architectures mentioned earlier, which reduces the possibility of play and flexibility at the joints. Furthermore, in the case of the invention, a single joint allows rotation around the longitudinal axis – this contributes to the rigidity of the robot, particularly when it is deployed in the longitudinal direction.
[0013] According to another aspect, a pipe milling system is provided comprising a pipe and a parallel robot as defined above in which the first frame is positioned and held fixed relative to the pipe.
[0014] Thus, the invention proposes a solution with simplified installation that ensures the robot's position within the pipe and the pipe's rigidity. BRIEF DESCRIPTION OF FIGURES
[0015] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:
[0016] [Fig. 1] The [Fig. 1] represents a cross-sectional view of the pipe incorporating the robot according to the invention.
[0017] [Fig.2] Fig.2 represents a top view of the pipe incorporating the robot according to the invention.
[0018] [Fig.3] Fig.3 represents a front view of the pipe integrating the robot according to the invention, the robot being in the configuration also shown in Fig.2.
[0019] [Fig.4] Fig.4 represents a schematic view of the robot according to the invention.
[0020] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. DETAILED DESCRIPTION
[0021] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:
[0022] According to one example, the third connecting rod is connected by its first end to one of the first displacement element or the second displacement element and by a pivot joint having an axis of rotation orthogonal to the main longitudinal axis of its second end to a linking element of the mobile platform.
[0023] This helps to maintain sufficient rigidity for the robot's operation. It also helps to keep the platform at a specific angle and ensures the proper functioning of the invention.
[0024] According to one example, the third connecting rod is configured to hold the robot's end effector, which is carried by the robot's mobile platform, oriented in a direction that has a fixed angle with respect to the robot's main longitudinal axis.
[0025] This fixed angle can take any value. In particular, it can be 90°.
[0026] This ensures proper operation of the robot and provides rigidity to the entire robot.
[0027] This is advantageous, particularly when the end effector operates in a direction orthogonal to the longitudinal axis. Indeed, when the angle is 90°, an end effector positioned on the moving platform in a direction orthogonal to the longitudinal axis (as illustrated in the figures) is oriented in a direction normal to the wall of the pipe in which the robot is engaged (assuming that this wall is cylindrical), thus enabling, for example, a simple drilling operation. Furthermore, an outward radial translational movement of the platform carrying the end effector generates only a compressive force on the end effector, without any additional bending. This results in greater rigidity for this type of action.
[0028] Thus, generally speaking and by way of example, the third connecting rod is configured to maintain one face of the moving platform at a fixed angle relative to the main longitudinal axis. This angle can be 90° as mentioned in the preceding paragraph. But more generally, it is also possible to configure the robot, and in particular its connecting rods, so that this angle is different from 90°.
[0029] This makes it possible to maintain the rigidity of the robot regardless of the desired angle.
[0030] According to one example, the first frame and the second frame are cylindrical with a circular base, the second frame surrounding the first frame.
[0031] This allows all rotational movements of the platform around the longitudinal axis to be carried out with a single pivot joint - thus limiting the possible play as much as possible. As a result, the rigidity of the robot is optimized.
[0032] According to one example, the pivot joint between the first frame and the second frame is achieved by two angular contact bearings mounted in an "O" configuration. The center distance between these two bearings must be as large as possible.
[0033] This ensures the transfer of axial and radial forces as well as good rigidity.
[0034] According to one example, the rotation of the mobile platform is achieved by an actuator taken from among a backlash-free coaxial reduction motor with a high reduction ratio or a long-torque direct drive motor.
[0035] The actuator for this rotation must be free of backlash and must allow sufficient forces to be supplied for machining.
[0036] According to one example, the first and second displacement elements are taken from among electric cylinders or linear motors.
[0037] According to one example, electric actuators are electric actuators with ball screws or trapezoidal screws with backlash compensation or satellite roller screws.
[0038] This allows sufficient force to be applied to move the platform while exhibiting axial rigidity.
[0039] According to one example, the first and second displacement elements are configured to be guided in translation by ball rails or two ball bushings installed in parallel.
[0040] Preferably, the pivot joints should each be made by two ball bearings separated as much as possible.
[0041] This ensures good rigidity of the system.
[0042] According to one example, the first, second and third connecting rods extend between their first end and their second end over a length L, with the length L fixed.
[0043] This allows for maintaining high axial and radial rigidity and thus ensuring proper operation of the robot in a radially restricted environment.
[0044] In one example, the mobile platform includes an end effector, the end effector extending in a direction orthogonal to the main longitudinal axis. In another example, the end effector is configured to perform machining of a pipe.
[0045] This makes it possible to ensure that the effector is always positioned so as to be directed towards the inner wall of the pipe and that the rigidity is sufficient to carry out this machining.
[0046] In the following description, the term "on" does not necessarily mean "directly on". Thus, when it is stated that a part or component A is supported "on" a part or component B, this does not mean that parts or components A and B are necessarily in direct contact with each other. These parts or components A and B may be either in direct contact or supported on each other. through one or more other parts. The same applies to other expressions such as, for example, the expression "A acts on B" which can mean "A acts directly on B" or "A acts on B through one or more other parts".
[0047] In the present patent application, the term "mobile" corresponds to a rotational movement or a translational movement or a combination of movements, for example the combination of a rotation and a translation.
[0048] In the detailed description that follows, terms such as "horizontal," "vertical," "longitudinal," "transverse," "upper," "lower," "top," "bottom," "front," "back," "inside," and "outside" may be used. These terms should be interpreted relatively in relation to the normal position of the robot in a pipe and the normal extension direction. For example, the terms "horizontal" and "longitudinal" correspond to the principal extension direction of the robot and the principal extension direction of a pipe.
[0049] A frame of reference will also be used whose transverse directions correspond to all the directions included in the (Y,Z) plane and therefore to the axes perpendicular to the X axis and the longitudinal direction corresponds to a direction parallel to the X axis. These directions are understood within the framework of a fixed frame of reference linked to the first frame 10.
[0050] A first fixed frame (X,Y,Z) is defined with respect to the first frame 10 in which the X axis is the longitudinal direction.
[0051] A frame of reference (X2, Y2, Z2) attached to the second frame 20, which undergoes a rotation about the X axis relative to the (X, Y, Z) frame of the first frame, can also be used. This frame is illustrated, for example, in [Fig. 2]. The X2 axis coincides with the X axis. The Y2 and Z2 axes are attached to the second frame and define a transverse plane that is perpendicular to the X2 axis.
[0052] The present invention relates to a parallel robot 1. A parallel robot 1 according to the invention will now be described with reference to Figures 1 to 4. Without limitation, the parallel robot is represented in a pipe 2.
[0053] In general, the parallel robot 1 extends along a main longitudinal axis X. The main longitudinal axis X of the parallel robot 1 can be coincident with the longitudinal axis of the pipe 2 in which the parallel robot 1 can be positioned.
[0054] The robot 1 generally comprises a first frame 10. The first frame 10 extends along the main longitudinal axis X. Advantageously, the first frame 10 may have dimensions smaller than the dimensions of a pipe 2. Furthermore, the first frame 10 may have a cylindrical structure extending along the longitudinal axis main X. The cylindrical structure may preferably have a circular base.
[0055] The robot 1 also includes a second frame 20. The second frame 20 is mounted on the first frame 10. More precisely, the second frame 20 is mounted on the first frame 10 with a pivot joint about the main longitudinal axis X. The second frame 20 can then also have, like the first frame 10, a cylindrical structure extending along the main longitudinal axis X. The displacement of the second frame 20 relative to the first frame 10 thus allows a rotation R of the second frame 20 around the main longitudinal axis X, relative to the first frame 10.
[0056] The robot 1 also includes a mobile platform 30. The platform 30 may have a parallelepiped shape. The parallelepiped shape may, for example, be cubic. The platform 30 may thus have several faces. The platform 30 is connected to the second frame 20 by a plurality of connecting rods 40. More precisely, the mobile platform 30 is connected to the second frame 20 by a first connecting rod 41, a second connecting rod 42, and a third connecting rod 43.
[0057] Each of the first, second and third connecting rods 41, 42, 43, is articulated by a first respective end on the second frame 20.
[0058] The robot 1 comprises a first movement element 50a. The robot also comprises a second movement element 50b. The first movement element 50a and the second movement element 50b can be configured to move the platform 30. More specifically, as illustrated in [Fig. 1], they can be configured to move the platform 30 such that the trajectory of the platform 30 makes at least one translation T1, T2.
[0059] The first displacement element 50a and the second displacement element 50b are positioned on the second frame 20.
[0060] The movements of the first movement element 50a and the second movement element 50b are controlled independently of each other. Each of these movement elements 50a and 50b can thus perform a translation relative to the frame 20, along the longitudinal direction parallel to the X axis (by respective sliding links which connect the first movement element 50a and the second movement element 50b to the second frame 20).
[0061] The movements of the first movement element 50a and the second movement element 50b are controlled synchronously, so that these movements generate a desired movement of the platform 30. The movements of the first movement element 50a and the second movement element 50b are controlled synchronously so that these movements generate a desired movement of the end effector positioned on the platform 30.
[0062] It is thus possible to move the platform 30 in translation by controlled movements of the first displacement element 50a and the second displacement element 50b.
[0063] According to one example, a translational displacement along the principal longitudinal axis X of the first displacement element 50a and the second displacement element 50b in opposite directions can result in a translation Tl of the platform 30 along the transverse direction Y2, perpendicular to the longitudinal axis X2. This translation Tl is illustrated in [Fig. 1]. The longitudinal axis X2 coincides with the principal longitudinal axis X.
[0064] According to another example, a translational displacement along the main longitudinal axis X of the first displacement element 50a and second displacement element 50b in the same direction can generate a translational displacement T2 of the mobile platform 30 along the main longitudinal axis X.
[0065] More specifically, the displacement of the first displacement element 50a and second displacement element 50b along the main longitudinal direction X causes the displacement of the platform 30 in a plane comprising the main longitudinal axis X, the normal to said plane being parallel to the pivot joint axes of the first 41, second 42 and third 43 connecting rods.
[0066] Additionally, a rotation R of the second frame 20 relative to the first frame 10 displaces the platform 30 in rotation around the main longitudinal axis X. Thus following a rotation R of the second frame 20, the platform 30 can additionally by the movement of the first 50a and second 50b displacement elements, carry out a first translation T1 along a direction Y2 and / or carry out at least a second translation T2 along a direction X2.
[0067] Preferably, the first displacement element 50a is configured to accommodate one connecting rod and the second displacement element 50b is configured to accommodate two connecting rods. Preferably, the first displacement element 50a and the second displacement element 50b are identical. In the case where the second frame 20 is cylindrical, the first displacement element 50a and the second displacement element 50b are positioned diametrically opposite each other. This ensures a symmetrical design and symmetrical rigidity of the robot 1.
[0068] The first displacement element 50a is connected by a pivot joint to the first end of the first connecting rod 4L. The pivot joint of the first end of the first connecting rod 41 with respect to the first displacement element 50a has an axis of rotation about an axis orthogonal to the principal longitudinal axis X. Additionally, the first displacement element 50a is connected by a sliding joint to the second frame 20. This sliding joint allows for translation of the first displacement element 50a relative to the second frame 20, along an axis parallel to the main longitudinal axis X.
[0069] Similar to the first displacement element 50a, the second displacement element 50b is connected by a pivot joint to the first end of the second connecting rod 42. The pivot joint of the first end of the second connecting rod 42 has an axis of rotation about an axis orthogonal to the main longitudinal axis X. Additionally, the second displacement element 50b is connected by a sliding joint to the second frame 20. The sliding joint allows translation of the second displacement element 50b relative to the second frame 20 along an axis parallel to the main longitudinal axis X.
[0070] Each of said sliding joints can be configured to allow at least one translation T1, T2 of the platform 30. As illustrated in [Fig. 1], a translation of the first end of the first connecting rod 41 and the second connecting rod 42 parallel to the main longitudinal axis X in opposite directions results in a translation T1 of the platform 30 along an axis orthogonal to the main longitudinal axis X. Additionally, a translation of the first end of the first connecting rod 41 and the second connecting rod 42 parallel to the main longitudinal axis X in the same direction results in a translation T2 of the platform 30 along an axis parallel to the main longitudinal axis X. More precisely, this translation of the displacement elements 50a, 50b is carried out parallel to the main longitudinal axis X.
[0071] Each of the first, second and third connecting rods 41, 42, 43, is articulated by a second end on the mobile platform 30.
[0072] More specifically, the second end of the first 41, second 42, and third 43 connecting rod are each articulated by a pivot joint. The pivot joint has an axis of rotation orthogonal to the principal longitudinal axis X. The respective axes of rotation of the pivot joints located at the first and second ends of the first 41, second 42, and third 43 connecting rods are all parallel to each other.
[0073] And these axes of rotation of the pivot joints are orthogonal to the longitudinal axis X.
[0074] The second ends of the first 41, second 42, and third 43 connecting rod are connected to the mobile platform 30 by at least one connecting element 50c positioned on the mobile platform 30. More precisely, each of the second ends of the first 41, second 42, and third 43 connecting rod is connected to a connecting element 50c. The translational displacement of the first 50a and second 50b displacement elements results in the translational displacement T1, T2 of the platform 30 in a plane including the principal longitudinal axis X.
[0075] The mobile platform 30 is thus connected to the second frame 20; the movement of the second frame 20 relative to the first frame 10 thus enables the rotation R of the mobile platform 30 around the main longitudinal axis X. Thus, it is the rotation R between the first frame 10 and the second frame 20 that allows the platform 30 to be moved in a plane YZ perpendicular to the longitudinal axis X.
[0076] The robot 1 thus presents a hybrid architecture with two parallel axes allowing translational movements in a plane (in the case of the frame fixed to the second frame 20 illustrated in [Fig.2] the (Y2, Z2) plane) and an upstream rotation axis allowing this plane to be rotated around the longitudinal axis X.
[0077] The first 10 and second building 20:
[0078] The first frame 10 and the second frame 20 are, for example, cylindrical with a circular base. The second frame 20 surrounds the first frame 10. Preferably, the first frame 10 and the second frame 20 are concentric with the main longitudinal axis X. To achieve this, the second frame 20 has an outer diameter greater than or equal to, preferably greater than, an inner diameter of the first frame 10. Since the second frame 20 and the first frame 10 are connected by a pivot joint, this configuration minimizes any play and radial forces between the two frames, while allowing rotation R of the second frame 20 around the longitudinal axis X. This, in turn, contributes to optimizing the rigidity of the robot 1.
[0079] The pivot joint between the first frame 10 and the second frame 20 can be achieved by two angular contact bearings mounted in an "O" configuration. The bearings ensure the transfer of axial forces along the X-axis and radial forces along the Y and Z axes. Furthermore, the bearings contribute to the rigidity of the second frame 20 relative to the first frame 10, and therefore of the robot 1. Preferably, the center distance between these two bearings should be as large as possible. The center distance should be at least equal to, and preferably at least 1.5 times greater than, the overhang distance between the last bearing and the effector 31 in its most fully extended position. This ensures a guide length greater than the overhang.
[0080] The first 50a and second 50b displacement element:
[0081] The third connecting rod 43 is advantageously connected at its first end to either the first displacement element 50a or the second displacement element 50b. The third connecting rod 43 can be connected at its first end by a pivot joint. The pivot joint has an axis of rotation orthogonal to the main longitudinal axis X. Additionally, the third connecting rod 43 is connected at its second end by a pivot joint having an axis of rotation orthogonal to the main longitudinal axis X to a connecting element 50c of the mobile platform 30. This further contributes to the rigidity of the robot 1. This additionally allows the platform 30 to be kept at a predetermined angle θ with respect to the main longitudinal axis X and ensures proper operation of the invention. The predetermined angle θ is thus a angle which remains fixed. Thus, the angle determined 0 does not vary when robot 1 is in operation.
[0082] The third connecting rod 43 can form a quadrilateral with either the first connecting rod 41 or the second connecting rod 42. More precisely, the quadrilateral can be formed by the first and second ends of the third connecting rod 43 and either the first 41 or the second connecting rod 42.
[0083] The first 50a and the second 50b displacement element are, for example, taken from electric cylinders or linear motors.
[0084] For example, the electric actuators are ball screw or trapezoidal screw electric actuators with backlash compensation or satellite roller screw electric actuators. This contributes to rigidity while moving the platform 30, and while exhibiting axial rigidity.
[0085] The first 50a and second 50b displacement elements can be configured to be guided in translation along a direction parallel to the main longitudinal axis X by ball rails or two ball bushings installed in parallel.
[0086] Preferably, the described pivot joints should each be made by two ball bearings spaced as far apart as possible. This ensures good rigidity of the system. The two ball bearings can thus be positioned far apart for better resistance to torsional forces. The further apart they are, the better this resistance will be.
[0087] The plurality of connecting rod s 40:
[0088] The third connecting rod 43 is advantageously configured to maintain the end effector 31 of the robot which is carried by the mobile platform 30 of the robot, oriented in a direction which has a fixed angle 0 with respect to the main longitudinal axis of the robot.
[0089] In this regard, in one embodiment the effector is fixed relative to the platform 30. Therefore, controlling the orientation of the platform in space implies controlling the orientation of the effector 31.
[0090] In such an embodiment in which the effector is fixed relative to the platform 30, the third connecting rod 43 is advantageously configured to maintain a face of the movable platform 30 contained in an inclined plane at a desired angle 0 relative to the main longitudinal axis X.
[0091] This angle 0 can in particular be 90°.
[0092] This control of the orientation of the platform 30 with a fixed angle with respect to the longitudinal axis X results from the fact that the respective first ends of the two connecting rods 42 and 43 are fixed (with respective pivoting links) on the means of movement 50b, and that the respective second ends of the two connecting rods 42 and 43 are fixed on the mobile platform 30 (also with respective pivoting links).
[0093] This leads in effect to the fact that the two connecting rods 42, 43 form the opposite sides of a deformable quadrilateral, whose four corners are the four ends of the two connecting rods 42, 43.
[0094] When the two connecting rods 42, 43 are of the same length and are arranged parallel to each other, this deformable quadrilateral is a deformable parallelogram.
[0095] This example is indeed advantageously implemented in combination with the fact that the third connecting rod 43 is connected to at least one of the displacement elements 50a, 50b. Thus, during the translation carried out by the displacement elements 50a, 50b, the platform is moved while maintaining a fixed angle θ with respect to the principal longitudinal axis X. The angle θ can be fixed by the length of the third connecting rod 43 relative to the lengths of the first 41 and second 42 connecting rods.
[0096] This allows the platform 30 to be maintained at an angle 0, for example, equal to 90° with respect to the principal longitudinal direction X of the robot 1, and ensures its proper operation. It is clear that, in this way, one face of the movable platform 30 is maintained at a fixed angle 0 with respect to the principal longitudinal direction X of the robot 1. This angle 0 can vary depending on a chosen length for the third connecting rod 43. A length of the third connecting rod 43 can then define the fixed angle 0. This fixed angle maintenance contributes to the rigidity of the entire robot 1.
[0097] According to one example, the first 41, second 42 and third 43 connecting rods each extend between their first end and their second end over the same length L. The length L of the connecting rods is preferably fixed.
[0098] Preferably, the length L of the first 41, second 42, and third 43 connecting rods is identical for all three. If the third connecting rod 43 has a length L identical to the length L of the first connecting rod 41 and the second connecting rod 42, then the resulting quadrilateral is a parallelogram.
[0099] Furthermore, the third connecting rod 43 forms the two opposite sides of this parallelogram with the first connecting rod 41 or with the second connecting rod 42 in a plane perpendicular to the axes of the connecting rod pivot joints. A fixed length ensures high axial and radial rigidity, thus guaranteeing proper operation of the robot in a radially constrained environment.
[0100] The length of the third connecting rod 43 can be adjusted to select the angle 0 according to the application. Similarly, the length L of the third connecting rod 43 can be different from the lengths of the first 41 and second 42 connecting rods. Adjustable means a length selected as desired but fixed during the operation of the robot 1. This length L of the third connecting rod 43 is preferably chosen beforehand during the assembly of the robot 1.
[0101] Thus, the length of the third connecting rod 43 can be chosen beforehand depending on the use of the robot 1. The length of the third connecting rod 43 can be chosen to define a desired angle 0. Indeed, depending on the use of the robot, an angle 0 other than 90° could be used. It is clear from this description that the length of the third connecting rod 43 is adjustable, but this setting remains fixed during the use of the robot 1. In the case where the length L of the third connecting rod 43 is modified to change the angle 0, the length L of the third connecting rod 43 is not equal to the length L of the first connecting rod 41 or the length L of the second connecting rod 42.
[0102] According to one example, the robot 1 may include a fourth connecting rod. The fourth connecting rod may then have the same functions as the third connecting rod 43. The fourth connecting rod 43 may then be connected to the other, either the first movement element 50a or the second movement element 50b. In this case, the third connecting rod 43 and the fourth connecting rod must be adjustable in length to avoid any over-constraint. Redundancy increases rigidity.
[0103] Platform 30:
[0104] The mobile platform 30 may, for example, have a parallelepiped shape. More precisely, the mobile platform 30 may have a cubic shape. Thus, the mobile platform 30 may have six faces. Advantageously, the platform 30 has a shape with dimensions smaller than one transverse dimension of a pipe 2.
[0105] According to one example, the mobile platform 30 has at least one of its six faces positioned perpendicular to the main longitudinal axis X. Advantageously, this face is always positioned in a plane perpendicular to the longitudinal axis during the translational displacements T of the displacement elements 50a, 50b and during the rotation R of the second frame 20. Preferably, the mobile platform 30 has at least two faces positioned perpendicular to the main longitudinal axis.
[0106] The mobile platform 30 advantageously includes an end effector 31. The end effector 31 may have the shape of a ball cutter. The end effector 31 may be motorized within the platform 30. The end effector 31 may also, according to another example, be motorized by a motor positioned outside the platform 30. For example, the motor may be connected to a flexible shaft with a right-angle drive.
[0107] According to one example, the end effector 31 extends from a face of the moving platform 30. The end effector 31 preferably extends in a direction orthogonal to the principal longitudinal axis X. Thus, advantageously, the end effector 31 extends from a face positioned in a plane that contains the principal longitudinal axis X of the platform 30. Therefore, a cutter of the end effector 31 is positioned so as to be directed towards the inner wall of the pipe during the operation of the robot 1. The end effector 31 allows This allows for machining the internal wall of a pipe. For example, the end piece 31, in the form of a ball cutter, can create a through opening in a pipe as shown in Figures 1 to 3.
[0108] During the operation of the robot 1, the rotation of the platform 30 is achieved by the rotation R of the second frame 20 relative to the first frame 10. The rotation of the mobile platform 30 can then be achieved by an actuator chosen from among a backlash-free coaxial reduction motor with a high reduction ratio or a high-torque direct-drive motor. Similarly, the rotation R of the second frame 20 is achieved by an actuator chosen from among a backlash-free coaxial reduction motor with a high reduction ratio or a high-torque direct-drive motor. Thus, the actuator for this rotation R must be backlash-free and must be able to provide sufficient forces for machining.
[0109] The 50c bonding elements:
[0110] According to one example, the first 41, second 42, and third 43 connecting rods are connected at their second ends to at least one connecting element 50c. More precisely, each first 41, second 42, and third 43 connecting rod is connected by a pivot joint to a connecting element 50c. The pivot joint has an axis of rotation about an axis orthogonal to the principal longitudinal axis X.
[0111] It is clear from the description that each of the pivot joints has an axis of rotation around an axis orthogonal to the main longitudinal axis X. Each of the pivot joints of the first 41, second 42 and third 43 connecting rods are parallel to each other.
[0112] To ensure the movement of the mobile platform 30, at least two connecting elements 50c can be positioned on two different faces of the mobile platform 30. More precisely, at least two connecting elements 50c are positioned on two opposite faces. These two faces are preferably positioned in a plane parallel to the principal longitudinal axis X. According to one example, the at least two preceding elements are connected to the second end of the first 41 and the second 42 connecting rod.
[0113] According to one example, at least one other additional connecting element 50c is positioned on another face of the platform 30. This at least one other additional connecting element 50c is positioned on a face that extends in a plane perpendicular to the principal longitudinal axis X. This at least one other additional connecting element 50c is connected to the second end of the third connecting rod 43. The third connecting rod 43 makes it possible to maintain sufficient rigidity and thus maintain the platform 30 with the face comprising the at least one other additional connecting element 50c positioned, for example, perpendicular to the principal longitudinal axis X during translational movements of the displacement elements 50a. 50b and during rotational movements of the second frame 20 relative to the first frame 10.
[0114] System 3;
[0115] According to one embodiment, the robot 1 is mainly used for maintaining the internal wall of the already positioned pipe. Thus, another aspect of the invention relates to a pipe milling system 3 comprising a pipe and a parallel robot 1 as described above.
[0116] The first frame 10 can then be positioned and held fixedly relative to the pipe 2. The first frame 10 can, for example, be held directly on the pipe. The first frame 10 can also, according to another example, be held by an external device positioned so as to align the robot 1 with its principal longitudinal axis X extending in a manner coinciding with a longitudinal axis of the pipe 2.
[0117] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.
[0118] NUMERICAL REFERENCES 1. Parallel Robot 10. First building 20. Second building 30. Mobile platform 31: Effector 40. Plurality of connecting rods 4L First connecting rod 42. Second connecting rod 43. Third connecting rod 50a. First element of displacement 50b. Second element of displacement 50c. connecting element 60: milling element 2: pipe 3: system T: translation R: rotation of the second frame relative to the first frame Y: main longitudinal axis 0: tilt angle of the mobile platform
Claims
1. Demands Parallel robot (1) extending along a principal longitudinal axis (X), characterized in that it comprises: • a first frame (10) extending along the main longitudinal axis (X), • a second frame (20) mounted on the first frame (10) with a pivot joint along the main longitudinal axis (X), • a mobile platform (30) connected to the second frame (20) by a first connecting rod (41), a second connecting rod (42) and a third connecting rod (43), each connecting rod (41, 42, 43) being articulated by a first end on the second frame (20) and by a second end on the mobile platform (30), • a first displacement element (50a) and a second displacement element (50b), the first (50a) displacement element being connected by a pivot joint to the first end of the first connecting rod (41) and also being connected by a sliding joint to the second frame (20) and the second (50b) displacement element being connected by a pivot joint to the first end of the second connecting rod (42) and also being connected by a sliding joint to the second frame (20), each of said sliding joints being configured to allow a translation (T) of the first end of the first connecting rod and of the second connecting rod parallel to the main longitudinal axis (X), the respective second ends of the first (41) and second (42) connecting rods each being articulated to the mobile platform (30) by a respective pivot joint and connected to at least one connecting element (50c) fixed to said platform, the third connecting rod (43) being connected by its first end by a pivot joint to one of the first displacement element (50a) or the second displacement element (50b) and by a pivot joint of its second end to a connecting element (50c) of the mobile platform (30), each pivot joint having an axis of rotation, the axes of rotation of the pivot joints of the first (41), second (42) (42) and third (43) connecting rods being all parallel to each other and being orthogonal to the main longitudinal axis (X) so that the displacement of the first (50a) and second (50b) displacement elements allows the mobile platform (30) to be moved in a plane which includes the main longitudinal axis (X) and whose normal is parallel to the axes of rotation of the pivot links of the first (41), second (42 and third (43) connecting rods, and the displacement of the second frame (20) relative to the first frame allows a rotation (R) of the mobile platform (30) to be made in a plane orthogonal to the main longitudinal axis (X), relative to the first frame (10).
2. Parallel robot (1) according to the preceding claim in which, the third connecting rod (43) is configured to hold an effector (31) of the robot (1) carried by the mobile platform (30) oriented in a direction which has a fixed angle (0) with respect to the main longitudinal axis (X).
3. Parallel robot (1) according to any one of the preceding claims, wherein the first frame (10) and the second frame (20) are cylindrical, the second frame (20) surrounding the first frame (10).
4. Parallel robot (1) according to any one of the preceding claims, wherein the pivot connection between the first frame (10) and the second frame (20) is achieved by two angular contact bearings mounted in an "O" configuration.
5. Parallel robot (1) according to any one of the preceding claims, wherein the rotation of the mobile platform (30) is achieved by an actuator taken from among a backlash-free coaxial reduction motor with a high reduction ratio or a direct drive long-torque motor.
6. Parallel robot (1) according to any one of the preceding claims wherein the first (50a) and second (50b) movement element are taken from electric actuators or linear motors.
7. Parallel robot (1) according to any one of the preceding claims, wherein the first (50a) and second (50b) displacement element are configured to be guided in translation by ball rails or two ball bushings installed in parallel.
8. Parallel robot (1) according to any one of the preceding claims wherein the first (41), second (42) and third (43) connecting rods extend between their first end and their second end over a length L, with the length L fixed.
9. Parallel robot (1) according to any one of the preceding claims wherein the mobile platform (30) comprises an end effector (31), the end effector (31) extending in a direction perpendicular to the main longitudinal axis (X) and being configured to perform machining of a pipe.
10. Pipe milling system (3) comprising a pipe (2) and a parallel robot (1) according to any one of the preceding claims wherein the first frame (10) is positioned and held fixedly relative to the pipe (2).