Parallel robot with improved torsional stiffness

Abstract

The invention relates to a parallel robot (1) comprising a frame (2) connected to a mobile platform (3) by a plurality of telescopic actuators (4.1-4.6) that are articulated with the frame (2) and the platform (3), the parallel robot (1) comprising a passive device (10) for the torsional stiffening of the mobile platform (3) relative to the frame (2) about a first axis of rotation (01), said device being a flexible transmission shaft.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION

[0003] Parallel robot with improved torsional rigidity

[0004] TECHNICAL FIELD

[0005] The invention relates to the field of robotics and more specifically to the field of parallel robots or parallel architectures.

[0006] STATE OF THE PRIOR ART

[0007] Parallel robots are robotic machines composed of several independent kinematic chains, generally telescopic actuators articulated at their two ends on a frame and a mobile platform.

[0008] This type of robot is frequently used in the manufacturing industry for assembly, welding, painting, and heavy lifting, as well as in robotic surgery due to the precision and complexity of the movements required for surgical procedures. This type of robot is also used in flight simulators for realistic flight simulation during pilot training, as well as in the dynamic positioning of 3D printer platforms.

[0009] Their parallel architecture offers high precision and excellent capacity to perform complex and precise movements. However, such architectures, due in particular to the articulations present at their ends, do not allow precise work requiring the recovery of torsional torque to be carried out, in particular around axes intersecting a plane defined by the ends of the actuators which are articulated on the platform. DISCLOSURE OF THE INVENTION

[0010] For this purpose, a parallel robot is provided comprising a frame connected to a mobile platform by a plurality of telescopic actuators articulated on the frame and the platform; According to the invention, the parallel robot comprises a passive device for torsionally stiffening the platform relative to the frame around a first axis of rotation. The passive stiffening device comprises a first shaft connected at its first end to the frame by a first coupling, the shaft being connected at its second end to the platform by a second coupling.

[0011] This gives a parallel robot whose mobile platform 3 can easily absorb torsional forces around the axis 01. Such a robot 1 makes it possible to take advantage of the precision qualities of a parallel architecture with the capacity to absorb significant torques. Such a robot is thus suitable for carrying out machining or drilling operations requiring the absorption of torques applied to the mobile platform, particularly around the first axis.

[0012] According to other particular, non-exclusive and optional embodiments of the invention: the first coupling is arranged to allow rotation of the shaft relative to the frame around a second axis substantially orthogonal to the first axis and / or the second coupling is arranged to allow rotation of the shaft relative to the frame around a third axis substantially orthogonal to the first axis; the shaft is a telescopic shaft; the shaft is mounted to slide relative to the frame and / or the platform via a sliding guide device; the sliding guide device comprises a sliding carriage relative to a frame secured to the frame or the platform.Such a carriage can be advantageously used in combination with a rigid, articulated, telescopic or flexible shaft; the sliding guide device comprises a second splined shaft; the first shaft is a flexible transmission shaft; the first shaft comprises a relaxation loop; the parallel robot comprises an additional shaft for transmitting a motor torque to an effector secured to the platform; the first shaft is hollow and defines an internal housing, the additional shaft being a flexible additional shaft which extends into the internal housing; the additional shaft is rotationally guided by at least one bearing carried by the passive stiffening device.

[0013] Other characteristics and advantages of the invention will appear on reading the following description of a particular non-limiting embodiment of the invention.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Reference will be made to the attached figures, including:

[0016] [Fig. 1] Figure 1 is a schematic perspective representation of a parallel robot according to a first embodiment of the invention;

[0017] [Fig. 2] Figure 2 is a schematic representation in front view of the stiffening device of the parallel robot of Figure 1;

[0018] [Fig. 3] Figure 3 is a schematic representation in front view of a second embodiment of the stiffening device according to the invention;

[0019] [Fig. 4] Figure 4 is a schematic representation in front view of a third embodiment of the stiffening device according to the invention;

[0020] [Fig. 5] Figure 5 is a schematic representation in front view of a fourth embodiment of the stiffening device according to the invention;

[0021] [Fig. 6] Figure 6 is a schematic representation in front view of a fifth embodiment of the stiffening device according to the invention;

[0022] [Fig. 7] Figure 7 is a schematic representation in front view of a sixth embodiment of the stiffening device according to the invention;

[0023] [Fig. 8] Figure 8 is a schematic representation in front view of a seventh embodiment of the stiffening device according to the invention; [Fig. 9] Figure 9 is a schematic representation in perspective of a detail of the stiffening device of Figure 8;

[0024] [Fig. 10] Figure 10 is a schematic representation in front view of an eighth embodiment of the stiffening device according to the invention.

[0025] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0026] According to a first embodiment of the invention, and with reference to Figures 1 and 2, the parallel robot according to the invention, designated 1, comprises a frame 2 connected to a mobile platform 3 by a plurality of telescopic actuators - here six electric cylinders 4.1 to 4.6 articulated at each of their ends on the frame 2 and the platform 3. Thus the respective lower ends 5.1 to 5.6 of the actuators 4.1 to 4.6 are articulated on the frame 2 and the respective upper ends 6.1 to 6.6 of the actuators 4.1 to 4.6 are articulated on the platform 3. The cylinders 4.1 to 4.6 are connected to a command and control unit 90 which supplies them with electrical energy and recovers the deployment information of the cylinders 4.1 to 4.6 via sensors integrated into the cylinders 4.1 and 4.6.

[0027] The robot 1 comprises a passive torsional stiffening device 10 for stiffening the platform 3 relative to the frame 2 around a first axis of rotation 01. The axis of rotation 01 connects, here, a first isobarycenter 2.1 of the lower ends 5.1 to 5.6 and a second isobarycenter 3.1 of the upper ends 6.1 to 6.6 when the parallel robot is in a rest situation or neutral position; The axis 01 is, conventionally, orthogonal to the platform 3 in all configurations of the robot 1. The device is said to be passive in that it does not require any external energy input to be able to carry out its stiffening action.

[0028] As seen in Figure 2, the device 10 comprises a first shaft 11 connected at its first end 11.1 to the frame 2 by a first coupling 12. The shaft 11 is also connected at its second end 11.2 to the platform 3 by a second coupling 13. The shaft 11 is, here, a telescopic shaft providing a sliding connection and which comprises a male portion 11.10 slidably engaged in a female portion 11.20. The male portion 11.10 comprises a stud 11.11 which is engaged in a groove 11.21 of the female portion 11.20.

[0029] The couplings 12 and 13 are, here, flexible couplings with metal bellows which provide a cardan-type connection of the shaft 11 to the frame 2 and the platform 3. A cardan-type connection is a coupling joint which allows an angular offset between the two coupled elements. In the context of the invention, the joint may be homokinetic or heterokinetic. The coupling 12 is, at a minimum, arranged to allow rotation of the shaft 11 relative to the frame 2 around a second axis 02 substantially orthogonal to the first axis 01. The coupling 13 is arranged to allow rotation of the shaft relative to the frame around a third axis 03 substantially orthogonal to the first axis 01, and, here, substantially orthogonal to the second axis 02.

[0030] As visible in figure 2, the coupling 12 comprises a first portion 12.1 of first coupling 12 rigidly secured in rotation around the axis 01 with the frame 2 and the coupling 13 comprises a second portion 13.1 of second coupling 13 rigidly secured in rotation around the axis 01 with the platform 3.

[0031] This gives a parallel robot 1 whose mobile platform 3 can easily absorb torsional forces around the axis 01. Such a robot 1 makes it possible to take advantage of the precision qualities of a parallel architecture with the capacity to absorb significant torques. Such a robot is thus suitable for carrying out machining or drilling operations requiring the absorption of torques applied to the mobile platform.

[0032] Elements identical or analogous to those previously described will bear a numerical reference identical to this one in the following description of a second, third, fourth, fifth, sixth, seventh and eighth embodiments of the invention.

[0033] According to a second embodiment of the invention shown in Figure 3, the first coupling 12 and the second coupling 13 are cardan joint type couplings which provide a rotational connection of the shaft 11 to the frame 2 and the platform 3. The coupling 12 comprises a portion 12.1 rigidly secured in rotation about the axis 01 with the frame 2 and the coupling 13 comprises a second portion 13.1 of second coupling 13 rigidly secured in rotation about the axis 01 with the platform 3.

[0034] The coupling 12 is arranged to allow rotation of the shaft 11 relative to the frame 2 about a second axis 02 substantially orthogonal to the first axis 01. The coupling 13 is arranged to allow rotation of the shaft relative to the frame about a third axis 03 substantially orthogonal to the first axis 01, and, here, substantially orthogonal to the second axis 02. The coupling 12 is also arranged to allow rotation of the shaft 11 relative to the frame 2 about a fourth axis 04 substantially orthogonal to the first axis 01 and to the second axis 02. The coupling 13 is also arranged to allow rotation of the shaft 11 relative to the platform 3 about a fifth axis 05 substantially orthogonal to the first axis 01 and to the third axis 03.

[0035] The shaft 11 is, here, a fixed-length single-piece shaft. The portion 12.1 of the coupling 12 is slidably mounted relative to the frame 2 via a sliding guide device 20. The device 20 comprises a carriage 21 sliding relative to a frame 22 secured to the frame 2. To do this, the carriage 21 comprises three arms 23 (only two of which are visible in FIG. 3) extending at one hundred and twenty degrees from each other and the ends 24 of which are provided with ball bushings 25 engaged on shafts 26 secured to the frame 22. Managing the sliding of the shaft 11 relative to the frame 2 according to this embodiment makes it possible to more effectively absorb the shear forces due to torsion and thus allows an increase in the torsion lever arm.

[0036] According to a third embodiment shown in Figure 4, the shaft 11 is a flexible transmission shaft and the guide device 20 comprises a second splined shaft 30 cooperating with a splined bushing 31 secured to the frame 2. For the purposes of the present application, a shaft 11 is flexible when it is deformable in a direction substantially orthogonal to an axis of rotation of the shaft 11 without causing significant stress on the actuators 4.1 to 4.6 of the robot 1 (less than ten percent of the nominal power of the actuator).

[0037] The couplings 12 and 13 correspond, here, respectively to the portions 11.20 and 11.30 of the shaft 11 which are located near the ends 11.1 and 11.2 of the shaft 11 respectively.

[0038] The couplings 12 and 13 provide a cardan-type connection between the shaft 11 on the frame 2 and the platform 3. The coupling 12 comprises a first portion 12.1 of the first coupling 12 rigidly secured in rotation about the axis 01 with the frame 2 and the coupling 13 comprises a second portion 13.1 of the second coupling 13 rigidly secured in rotation about the axis 01 with the platform 3.

[0039] According to a fourth embodiment shown in Figure 5, the tree

[0040] 11 is a flexible transmission shaft identical to that of the second embodiment and the guide device 20 comprises the carriage 21 and the frame 22 according to the second embodiment of the invention.

[0041] According to a fifth embodiment shown in Figure 6, the shaft 11 is a flexible transmission shaft identical to that of the second embodiment. The shaft 11 is, according to the fourth embodiment, embedded at its two ends 11.1 and 11.2 respectively on the frame 2 and the platform 3. The shaft 11 comprises a relaxation loop 40. The relaxation loop 40 comprises a succession of two inflections 41 and 42 of the flexible shaft 11 which allow a relative displacement of the ends 11.1 and 11.2 of the shaft 11 in a direction substantially parallel to the axis 01. The couplings

[0042] 12 and 13 correspond, here, respectively to the portions 11.20 and 11.30 of the shaft 11 which are located near the ends 11.1 and 11.2 of the shaft 11 respectively.

[0043] The couplings 12 and 13 provide a cardan-type connection of the shaft 11 to the frame 2 and the platform 3. The coupling 12 comprises a first portion 12.1 of the first coupling 12 rigidly secured in rotation about the axis 01 with the frame 2 and the coupling 13 comprises a second portion 13.1 of the second coupling 13 rigidly secured in rotation about the axis 01 with the platform 3. According to a sixth embodiment shown in FIG. 7, the shaft 11 is hollow and defines an internal housing 50. The shaft 11 is connected at its first end 11.1 to the frame 2 by the coupling 12 and at its second end 11.2 to the platform 3 by the coupling 13.

[0044] The shaft 11 is here a fixed-length single-piece shaft. The couplings 12 and 13 are, here, flexible couplings with metal bellows which provide a cardan-type connection of the shaft 11 to the frame 2 and the platform 3.

[0045] The portion 12.1 of the coupling 12 is slidably mounted relative to the frame 2 via a sliding guide device 20. The device 20 comprises a carriage 21 sliding relative to a frame 22 secured to the frame 2. The carriage 21 comprises three arms 23 (only two of which are visible in FIG. 3) extending at one hundred and twenty degrees from each other and the ends 24 of which are provided with ball bushings 25 engaged on shafts 26 secured to the frame 22.

[0046] The first portion 12.1 of the coupling 12 and the second portion

[0047] 13.1 of the coupling 13 as well as the third portion 12.2 of the coupling 12 rigidly connected to the first end 11.1 of the shaft 11 and the fourth portion 13.2 of the coupling 13 rigidly connected to the second end 11.2 of the shaft 11 each comprise a central bore for receiving an additional flexible transmission shaft 60 which extends into the internal housing 50. The first portion

[0048] 12.1 thus comprises a first counterbore 70 for receiving a first bearing 71 for guiding the rotation of the shaft 60. The second portion 13.1 comprises a second counterbore 72 for receiving a second bearing 73 for guiding the rotation of the shaft 60. The third portion

[0049] 12.2 comprises a second counterbore 72 for receiving a second bearing 73 for guiding the rotation of the shaft 60. Similarly, the third portion 12.2 comprises a third counterbore 74 for receiving a third bearing 75 for guiding the rotation of the shaft 60. The fourth portion 13.4 comprises a fourth counterbore 76 for receiving a fourth bearing 77 for guiding the rotation of the shaft 60.

[0050] A milling head 80 secured to the platform 3 is connected to the upper end 61 of the shaft 60. The lower end 62 of the shaft 60 is connected to a motor 85 for actuating the milling head 80 and which is mounted on the carriage 21. The shaft 60 thus transmits a motor torque from the motor 85 to the milling head 80.

[0051] This gives a parallel robot 1 whose mobile platform 3 is connected by a passive rotational stiffening device 10 to the frame 2 and which is thus able to carry out operations requiring the recovery of torques applied to the platform 3, such as for example drilling or machining operations.

[0052] According to a seventh embodiment of the invention shown in Figures 8 and 9, the first coupling 12 is an Oldham joint type coupling and the second coupling 13 is a recessed coupling. The couplings 12 and 13 thus provide a rotational connection of the shaft 11 to the frame 2 and the platform 3.

[0053] The coupling 12 comprises a portion 12.1 rigidly secured in rotation around the axis 01 with the frame 2 and the coupling 13 comprises a second portion 13.1 of second coupling 13 - here the female portion 11.20 of the shaft 11 - rigidly secured in rotation around the axis 01 with the platform 3.

[0054] According to an eighth embodiment of the invention shown in figures 10, the first coupling 12 and the second coupling 13 are sliding pivot type couplings which provide a rotational connection of the shaft 11 to the frame 2 and the platform 3. The sliding pivot of the first coupling 12 is a sliding pivot with axis 012 substantially parallel to the axis 02, and the sliding pivot of the second coupling 13 is a sliding pivot with axis 013 substantially parallel to the axis 03. The shaft 11 is here the telescopic shaft of the first embodiment.

[0055] The coupling 12 comprises a portion 12.1 rigidly secured in rotation about the axis 01 with the frame 2 and the coupling 13 comprises a second portion 13.1 of second coupling 13 rigidly secured in rotation about the axis 01 with the platform 3.

[0056] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims. In particular, although here the platform comprises six electric cylinders, the invention also applies to other types of linear actuators such as, for example, hydraulic cylinders or linear motors. The number of actuators making up the plurality is dependent on the number of degrees of freedom whose control is desired and can vary from two to more than six; although here the shaft 11 comprises a sliding guide of a male portion in a female portion using a stud / groove assembly, the invention also applies to other types of sliding shaft such as, for example, a shaft comprising splines with clearance adjustment, a ball-splined shaft or a shaft comprising ball runners engaged in rails;although here the shaft is slidably mounted relative to the frame, ; the invention also applies to a shaft slidably mounted relative to the platform; although here the carriage comprises three arms, the invention also applies to a carriage provided with a different number of arms for its sliding guidance relative to the frame such as for example a single arm, two or more than three; although here the carriage is slidably guided relative to the frame using ball bushings engaged on shafts, the invention also applies to other linear guidance means such as for example pads of all shapes and corresponding rails, rollers or dovetails, a splined shaft; although here the splined guidance has been described in combination with a flexible shaft, the invention also applies to a splined guidance and a rigid shaft mounted on a cardan joint;although here the spline guidance has been described in combination with a flexible shaft, the invention also applies to a spline guidance and a rigid shaft mounted on a cardan joint; although here the additional shaft extends into the internal housing, the invention also applies to an additional shaft that is offset and that would be decoupled from the stiffening device; although here the additional shaft is guided in rotation using four bearings, the invention also applies to an additional shaft that would be mounted freely, without guidance in rotation and / or in translation; although here the mobile platform carries a milling head, the invention also applies to other types of effector integral with the platform such as for example a drill, a grinder, a gripping device or a feeler; - - although here the frame is integral with the frame, the invention also applies to a frame integral with the platform;

[0057] - although here the actuating motor is integral with the carriage, the invention also applies to other types of mounting of the actuating motor such as for example a motor mounted to slide using a sliding connection relative to the frame.

Claims

CLAIMS 1. Parallel robot (1) comprising a frame (2) connected to a mobile platform (3) by a plurality of telescopic actuators (4.1-4.6) articulated on the frame (2) and the platform (3), the parallel robot (1) comprising a passive stiffening device (10) for torsion of the mobile platform (3) relative to the frame (2) around a first axis of rotation (01), the passive stiffening device (10) comprising a first shaft (11) connected at its first end (11.1) to the frame by a first coupling (12), the first shaft (11) being connected at its second end (11.2) to the mobile platform (3) by a second coupling (13), and in which the first shaft (11) is a flexible transmission shaft.

2. Parallel robot (1) according to claim 1, wherein the first coupling (12) is arranged to allow rotation of the first shaft (11) relative to the frame (2) around a second axis (02) substantially orthogonal to the first axis (01) and / or the second coupling (13) is arranged to allow rotation of the first shaft (11) relative to the frame (2) around a third axis (03) substantially orthogonal to the first axis (01).

3. Parallel robot (1) according to claim 1 or 2, wherein the first shaft (11) is a telescopic shaft.

4. Parallel robot (1) according to claim 1, wherein the first shaft (11) comprises a relaxation loop (40).

5. Parallel robot (1) according to any one of the preceding claims, wherein the first shaft (11) is mounted at sliding relative to the frame (2) and / or the platform (3) via a sliding guide device (20).

6. Parallel robot (1) according to claim 5, in which the sliding guide device (20) comprises a carriage (21) sliding relative to a frame (22) secured to the frame (2) or the platform (3).

7. Parallel robot (1) according to claim 5, wherein the sliding guide device (20) comprises a second splined shaft (30).

8. Parallel robot (1) according to any one of the preceding claims, comprising an additional shaft (60) for transmitting a motor torque to an effector (80) secured to the platform (3).

9. A parallel robot (1) according to any preceding claim, wherein the first shaft (11) is hollow and defines an internal housing (50), the further shaft (60) being a flexible shaft which extends into the internal housing (50).

10. Parallel robot (1) according to claim 9, wherein the additional shaft (60) is guided in rotation by at least one bearing (71, 73, 75, 77) carried by the passive stiffening device (10).

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