Rigid parallel robot

Abstract

Title: Rigid Parallel Robot The invention relates to a parallel robot (1) extending along a principal longitudinal axis (X), characterized in that it comprises a first frame (10), a second frame (20) mounted on the first frame by a pivot joint, a movable platform (30) connected to the second frame by a first (41), a second (42), and a third connecting rod (43), and comprising a first (50a) and a second (50b) movement element respectively connected by a pivot joint to the first and second connecting rods and by a sliding joint to the second frame, each of the connecting rods being articulated by a pivot joint and connected to a connecting element (50c) positioned on the platform such that the movement of the elements allows the platform to be translated, and the movement of the second frame allows the platform to be rotated (R) about the principal longitudinal axis. Figure for the abstract: Fig. 1

Description

Title of the invention: Rigid parallel robot Technical field

[0001] The present invention relates to the field of robotics and more precisely to the field of parallel robots also called parallel robotic architectures. It finds a particularly advantageous application in the field of machining carried out by a parallel robotic architecture in a difficult-to-access environment, especially with a restricted radial space, such as the renovation of piping from the inside. STATE OF THE ART

[0002] There are different parallel robotic architectures that can be used in restricted environments such as the renovation of the inside of piping.

[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 second end of the first, second and third connecting rods each being articulated by a pivot joint having an axis of rotation perpendicular to the main longitudinal axis and connected to at least one connecting element positioned on the mobile platform such that the displacement of the first and second displacement elements allows the mobile platform to be translated in a plane perpendicular to the main longitudinal axis, and the movement of the second frame relative to the first frame allows the mobile platform to rotate around the main longitudinal axis, relative to the first frame.

[0011] Thus, the invention provides a solution for performing maintenance in a confined space. More specifically, the invention provides a solution with sufficient rigidity to withstand radially directed forces, even when the invention is deployed in a longitudinal direction. The invention therefore enables internal pipe maintenance while maintaining sufficient rigidity to perform this operation precisely.

[0012] The use of pivots whose axes are perpendicular to the longitudinal axis, rather than ball joints / half-circle joints (a technological constraint implied by the architectural choices of many parallel systems), in 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 an axis that is not perpendicular to the longitudinal axis—this contributes to the robot's rigidity, 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 presenting an easy installation allowing to ensure the position of the robot in the pipe and the rigidity of the latter. BRIEF DESCRIPTION OF THE 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.

[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 or second displacement element and by a pivot joint having an axis of rotation perpendicular 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 a face of the moving platform contained in a plane perpendicular to the main longitudinal axis at an angle with respect to the main longitudinal axis.

[0025] This allows the platform to be kept at a constant angle of 90° to the longitudinal direction of the robot, ensuring its proper operation. Indeed, this ensures the rigidity of the entire robot assembly.

[0026] According to one example, the first frame and the second frame are cylindrical with a circular base, the second frame surrounding the first frame.

[0027] 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.

[0028] 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.

[0029] This ensures the transfer of axial and radial forces as well as good rigidity.

[0030] 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.

[0031] The actuator for this rotation must be free of backlash and must allow sufficient forces to be supplied for machining.

[0032] According to one example, the first and second displacement elements are taken from among electric cylinders or linear motors.

[0033] According to one example, electric actuators are electric actuators with ball screws or trapezoidal screws with backlash compensation or satellite roller screws.

[0034] This allows sufficient force to be applied to move the platform while exhibiting axial rigidity.

[0035] 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.

[0036] Preferably, the pivot connections should each be made by two ball bearings separated as much as possible.

[0037] This ensures good rigidity of the system.

[0038] 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.

[0039] This allows for maintaining high axial and radial rigidity and thus ensuring proper operation of the robot in a radially restricted environment.

[0040] In one example, the mobile platform includes an end effector, the end effector extending in a direction perpendicular to the main longitudinal axis. In another example, the end effector is configured to perform machining of the pipe.

[0041] 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.

[0042] 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 by each other via one or more other parts. The same applies to other expressions such as, for example, the expression "A acts on B," which may mean "A acts directly on B" or "A acts on B via one or more other parts."

[0043] In this patent application, the term "mobile" refers to a rotational movement or a translational movement or a combination of movements, for example a combination of rotation and translation.

[0044] 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.

[0045] A reference frame will also be used whose transverse or rear / front direction corresponds to the Z axis, the longitudinal or right / left direction corresponds to the X axis and the vertical or bottom / top direction corresponds to the Y axis.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 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.

[0050] The robot 1 also includes a mobile platform 30. The platform 30 is connected to the second frame 20 by a plurality of connecting rods 40. More specifically, 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.

[0051] Each of the first, second and third connecting rods 41, 42, 43, is articulated by a first end on the second frame 20.

[0052] The robot 1 comprises a first movement element 50a. The robot also comprises a second movement element 50b. Preferably, the first movement element 50a and the second movement element 50b are identical. This ensures a symmetrical design and similar rigidity of the robot 1.

[0053] 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 has an axis of rotation about an axis perpendicular to the main longitudinal axis X. Additionally, the first displacement element 50a is connected by a sliding joint to the second frame 20. The sliding joint allows translation along an axis parallel to the main longitudinal axis X.

[0054] 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 perpendicular 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 along an axis parallel to the main longitudinal axis X.

[0055] Each of said sliding joints is configured to allow a translation T of the first end of the first connecting rod 41 and of the second connecting rod 42. More Specifically, this translation of the displacement elements 50a, 50b, is carried out parallel to the main longitudinal axis X.

[0056] Each of the first, second and third connecting rods 41, 42, 43, is articulated by a second end on the mobile platform 30.

[0057] 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 perpendicular to the main longitudinal axis X.

[0058] 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. The displacement of the first 50a and second 50b displacement elements by translation T causes the displacement by translation T of the platform 30 in a plane perpendicular to the main longitudinal axis X.

[0059] 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 allows the rotation R of the mobile platform 30 around the main longitudinal axis X.

[0060] The robot 1 thus presents a hybrid architecture with 2 parallel axes allowing translational movements in a plane (ZY) and an upstream rotation axis allowing this plane to be rotated around the longitudinal axis X.

[0061] The first 10 and second building 20:

[0062] 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. 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 still allowing rotation R around the longitudinal axis X. As a result, the rigidity of the robot 1 is optimized.

[0063] The pivot joint between the first frame 10 and the second frame 20 can then be achieved by two angular contact bearings mounted in an "O" configuration. The bearings ensure the transfer of axial and radial forces as well as good rigidity. Preferably, the center distance between these two bearings should be as large as possible. The center distance must 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.

[0064] The first 50a and second 50b displacement element:

[0065] 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. Additionally, the third connecting rod 43 is connected at its second end by means of a pivot joint having an axis of rotation perpendicular 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. Additionally, it allows the platform 30 to be maintained at a fixed angle θ with respect to the main longitudinal axis X and ensures proper operation of the invention. The fixed angle θ is thus a constant angle. Therefore, the fixed angle θ does not vary when the robot is in operation.

[0066] The first 50a and the second 50b displacement element are, for example, taken from electric cylinders or linear motors.

[0067] 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.

[0068] The first 50a and second 50b displacement elements can be configured to be guided in translation T by ball rails or two ball bushings installed in parallel.

[0069] Preferably, the 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.

[0070] The plurality of connecting rod s 40:

[0071] The third connecting rod 43 is advantageously configured to maintain a face of the movable platform 30 lying in a plane perpendicular to the main longitudinal axis at a fixed angle to the main longitudinal axis. This example is 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 performed by the displacement elements 50a, 50b, the platform is translated while maintaining a fixed angle through its connection with the third connecting rod 43.

[0072] 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, thus ensuring its proper operation. This fixed angle maintenance contributes to the rigidity of the entire robot 1 assembly.

[0073] According to one example, the first 41, second 42, and third 43 connecting rods each extend over a length L between their first and second ends. The length L of the connecting rods is preferably fixed. A fixed length maintains high axial and radial rigidity, thus ensuring proper robot operation in a radially constrained environment. The length of the connecting rod 43 can be adjusted to select the angle 0 according to the application.

[0074] 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.

[0075] Platform 30:

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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 perpendicular 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. 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 thus enables machining of the inner wall of a pipe. For example, the end effector 31, in the form of a ball cutter, can create a through-hole in a pipe as shown in Figures 1 to 3.

[0080] 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 selected from 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 selected from 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.

[0081] The 50c bonding elements:

[0082] 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 perpendicular to the main longitudinal axis X.

[0083] 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.

[0084] 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 main 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 perpendicular to the main longitudinal axis X during the translational movements of the displacement elements 50a, 50b and during the rotational movements of the second frame 20 relative to the first frame 10.

[0085] System 3;

[0086] 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.

[0087] 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 main longitudinal axis X extending in a manner coinciding with a longitudinal axis of the pipe 2.

[0088] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

[0089] NUMERICAL REFERENCES 1. Parallel Robot 10. First building 20. Second building 30. Mobile platform 31: Effector 40. Plurality of connecting rods 41. 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 at one end on the second frame (20) and at one 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 second end of the first (41), second (42) and third connecting rod (43) each being articulated by a pivot joint having an axis of rotation perpendicular to the main longitudinal axis (X) and connected to at least one connecting element (50c) positioned on the mobile platform (30) such that the displacement of the first (50a) and second (50b) displacement elements allows the mobile platform (30) to be translated in a plane perpendicular to the main longitudinal axis (X), and the displacement of the second frame (20) relative to the first frame allowing a rotation (R) of the mobile platform (30) around the main longitudinal axis (X), relative to the first frame (10).

2. Parallel robot (1) according to the preceding claim, wherein the third connecting rod (43) is connected by its first end to one of the first displacement element (50a) or the second displacement element (50b) and by a pivot joint having an axis of rotation perpendicular to the main longitudinal axis (X) of its second end to a linking element (50c) of the moving platform (30).

3. Parallel robot (1) according to any one of the preceding claims wherein, the third connecting rod (43) is configured to maintain a face of the moving platform (30) contained in a plane perpendicular to the main longitudinal axis (X) at an angle (0) with respect to the main longitudinal axis (X).

4. 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).

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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 the pipe.

11. 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 fixed relative to the pipe (2).

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