ROBOT DRILLING CLAMP

Abstract

A clamp for a robotic drill and related method and system for robotic drilling of a component. The clamp attaches to a drilling tool of a robotic drill. The clamp includes: an attachment portion configured for attachment to the drilling tool; a frame linearly moveable relative to the attachment portion along a central axis of the clamp parallel to a drilling direction of the drilling tool; an actuation mechanism including a servo motor configured to drive linear movement of the frame relative to the drilling tool; a workpiece contacting portion at a distal end of the frame, including a surface for contacting a surface of a workpiece to be drilled and an aperture allowing for passage of a drill bit of the drilling tool through to the workpiece surface; and a force sensor arranged to measure a force acting on the workpiece contacting portion in the drilling direction.

Claims

1. A clamp configured for attachment to a drilling tool of a robotic drill, the clamp comprising: an attachment portion configured for attachment to the drilling tool; a frame linearly moveable relative to the attachment portion along a central axis of the clamp concentric with a drilling direction of the drilling tool; an actuation mechanism comprising a servo motor configured to drive linear movement of the frame relative to the drilling tool; a workpiece contacting portion at a distal end of the frame, comprising a surface for contacting a surface of a workpiece to be drilled and an aperture allowing for passage of a drill bit of the drilling tool through to the workpiece surface; and a force sensor arranged to measure a force acting on the workpiece contacting portion in the drilling direction.

2. The clamp of claim 1, wherein the workpiece contacting portion has a non-slip surface for contacting the workpiece surface.

3. The clamp of claim 1, wherein the frame has a pair of arms extending in the drilling direction on either side of the central axis and a distal end piece extending between the pair of arms.

4. The clamp of claim 3, wherein the arms and end piece are of unitary construction.

5. The clamp according to claim 3, wherein the servo motor is configured to drive each of the arms of the frame by rotation of respective rods extending along each arm.

6. The clamp according to claim 5, comprising a pulley or timing belt extending between the pair of arms arranged to synchronise rotation of the rods.

7. A robotic drilling system, comprising: a robotic drill having a drilling tool; a workpiece holder for holding a workpiece to be machined; a clamp attached to the drilling tool, the clamp comprising: an attachment portion attached to the drilling tool; a frame linearly moveable relative to the attachment portion along a central axis of the clamp concentric with a drilling direction of the drilling tool; an actuation mechanism comprising a servo motor configured to drive linear movement of the frame relative to the drilling tool; a workpiece contacting portion at a distal end of the frame, comprising a surface for contacting a surface of a workpiece to be drilled and an aperture allowing for passage of a drill bit of the drilling tool through to the workpiece surface; and a force sensor arranged to measure a force acting on the workpiece contacting portion in the drilling direction, the robotic drilling system further comprising: a controller connected and arranged for control of the robotic drill and clamp, wherein the controller is configured to: actuate the robotic drill to contact the surface of the workpiece contacting portion of the clamp with a workpiece to be machined; actuate the servo motor to drive the clamp on to the workpiece while measuring a force from the force sensor until a predetermined force has been reached; and operate the drilling tool to drill a hole into the workpiece.

8. The robotic drilling system of claim 7 further comprising a metrology system for measuring a position of the drilling tool relative to the workpiece to be machined.

9. The robotic drilling system of claim 8, wherein the metrology system comprises a first plurality of datums located on the robotic drill and a second plurality of datums located on the workpiece holder.

10. The robotic drilling system of claim 9, wherein the controller is configured to receive signals from the first and second plurality of datums to determine a position of the drilling tool relative to the workpiece.

11. The robotic drilling system of claim 10, wherein the metrology system is an optical metrology system, and the first and second plurality of datums comprise optical emitters, the metrology system comprising a plurality of optical sensors arranged to determine a position of the tool relative to the workpiece holder based on signals received by the optical sensors from the first and second plurality of optical emitters.

12. The robotic drilling system of claim 8 wherein, in a first mode, the controller is configured to: actuate the robotic drill to contact the surface of the workpiece contacting portion of the clamp with a predetermined location on the workpiece to be machined; measure a first position of the drilling tool relative to the workpiece with the metrology system; actuate the servo motor to drive the clamp on to the workpiece while measuring a force from the force sensor until a predetermined force has been reached; measure a second position of the drilling tool relative to the workpiece with the metrology system; determine a bias from a difference between the first and second measured positions; and store the determined bias for the predetermined location.

13. The robotic drilling system of claim 12, wherein the controller is configured to determine and store a bias for a plurality of predetermined locations on the workpiece.

14. The robotic drilling system of claim 8, wherein in a second mode, the controller is configured to: retrieve a stored bias for a predetermined location of a workpiece to be machined; actuate the robotic drill to contact the surface of the workpiece contacting portion of the clamp at the predetermined location offset by the retrieved bias; actuate the servo motor to drive the clamp on to the workpiece while measuring a force from the force sensor until a predetermined force has been reached; and operate the drilling tool to drill a hole at the predetermined location of the workpiece.

15. The robotic drilling system of claim 14 wherein the controller is configured to measure a position of the drilling tool after actuating the servo motor and to update the stored bias for the predetermined location.

16. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

Description

DETAILED DESCRIPTION

[0061] The invention is described in further detail below by way of example and with reference to the accompanying drawings, in which:

[0062] FIG. 1 is a schematic diagram illustrating three different types of positioning errors in a robotic arm;

[0063] FIG. 2 is a schematic sectional view of an example clamp attached to a drilling tool;

[0064] FIG. 3 is a schematic diagram of an example robotic drilling system;

[0065] FIG. 4 is a schematic flow diagram of an example method of operating a robotic drill in a first mode;

[0066] FIG. 5 is a schematic flow diagram of an example method of operating a robotic drill in a second mode;

[0067] FIG. 6 is a diagram of an example robotic drilling system; and

[0068] FIG. 7 is a diagram of an example clamp attached to a drilling tool of a robotic drill.

[0069] FIGS. 1a), 1b) and 1c) show a robotic arm 100, illustrating different sources of positional inaccuracy, as described in the background section above.

[0070] FIG. 2 is a schematic drawing of an example clamp 200 configured for attachment to a drilling tool 201 of a robotic drill, which may for example comprise a robotic arm of the type shown in FIG. 1. The clamp 200 comprises an attachment portion 220 for attachment to the drilling tool 201, and a frame 202 that is linearly moveable relative to the attachment portion 220 along a central axis 203 of the drilling tool 201, i.e. along a rotational axis of a drill bit 204 attached to the drilling tool 201. The drilling tool 201 is configured to drill a workpiece by actuating the drill bit 204 along the central axis 203 in the direction indicated by arrow 221.

[0071] The clamp 200 comprises an actuation mechanism comprising a servo motor 205 configured to drive linear movement of the frame 202 relative to the attachment portion 220, i.e. relative to the drilling tool 201. A workpiece contacting portion 206 at a distal end 207 of the frame 202 comprises a surface 208 for contacting a surface of a workpiece to be drilled and an aperture 209 allowing for passage of the drill bit 204 through to the workpiece surface.

[0072] A force sensor 210 is arranged to measure a force acting on the workpiece contacting portion 206 in the drilling direction. The force sensor 210 may for example form part of the workpiece contacting portion 206 or may be provided elsewhere in the frame 200 or attachment portion 220 to measure a force acting along the central axis 203 between the workpiece and the drilling tool 201.

[0073] The workpiece contacting portion 206 may have a non-slip surface 208 for contacting the workpiece.

[0074] The frame 202 in the example of FIG. 2 generally has a C-shape, with a pair of arms 211a, 211b extending in the drilling direction on either side of the central axis 203 and a distal end piece 212 extending between the pair of arms 211a, 211b. The arms 211a, 211b and the distal end piece 212 may be of unitary construction, for example formed of a single piece of metal, to aid stiffness and prevent distortion of the frame 202 during use. Other shapes may also be possible, and the frame 202 may have more than two arms 211a, 211b.

[0075] The servo motor 205 drives each of the arms 211a, 211b of the frame 202 by driving respective rods 213a, 213b extending along each arm 211a, 211b. A pulley or timing belt 214 extends between the pair of arms 211a, 211b across the distal end section 212, allowing for the rotation of the rods 213a, 213b to be synchronised so that the frame 202 moves in a uniform linear direction along the central axis 203, thereby applying a force on the workpiece parallel with the drilling direction.

[0076] A plurality of datums 215 may be provided, which may be attached to the part of the clamp that is secured to the drilling tool 201, i.e. the attachment portion 220, to allow for a metrology system to determine a location of the drilling tool 201, described in further detail below. Typically at least three datums 215 will be required to enable a precise location and orientation in three-dimensional space to be determined.

[0077] FIG. 3 illustrates schematically an example robotic drilling system 300. The system 300 comprises a robotic drill 301 comprising a drilling tool 201, on to which a clamp 200 of the type described above is attached. A workpiece holder 302 is provided for holding a workpiece (not shown) to be machined. A controller 303 is connected to the robotic drill 301 for control of the robotic drill 301 and clamp 200. The controller 303 actuates the robotic drill 301 to contact the surface of the workpiece contacting portion 208 (FIG. 2) to the surface of a workpiece to be machined and actuates the servo motor 205 in the clamp 200 to drive the clamp 200 on to the workpiece while measuring a force from the force sensor 206 until a predetermined force has been reached. The controller 303 may then operate the drilling tool 201 to drill a hole into the workpiece.

[0078] The system 300 may comprise a metrology system for measuring a position of the drilling tool 201 relative to the workpiece to be machined. The metrology system comprises a first plurality of datums 215 on the robotic drill 301, specifically on the part of the clamp 200 that is attached to the drilling tool 201, i.e. the attachment portion 220, and a second plurality of datums 315 on the workpiece holder 302. Each plurality of datums 215, 315 comprises at least three datums to enable accurate positioning and orientation of the workpiece holder 302 and drilling tool 201 in three-dimensional space relative to each other. The datums 215, 315 may for example be light emitting elements, for example light emitting diodes. A plurality of light detecting elements 304 may be arranged to receive light from each of the light emitting elements 215, 315, signals from which are received by a metrology control unit 305. The metrology control unit 305 also controls operation of the light emitting elements 215, 315. The metrology control unit 305 may provide position information to a computer 306, which also communicates with the controller 303.

[0079] Although the controller 303, computer 306 and metrology control unit 305 are illustrated as separate components in FIG. 3, these components may be contained in, or considered as being, a single controller, or a controller may be considered to be distributed between and among the different functional components 303, 306, 305.

[0080] The metrology system allows the robotic drilling system 300 to measure the relative locations of the drilling tool 201 and workpiece holder 302, thereby allowing the controller 303 to compensate for any difference in location of the drilling tool 201 after actuation of the clamp 200 before a drilling operation. This may for example be carried out during each drilling operation or may be carried out prior to performing any drilling operations on a workpiece.

[0081] FIG. 4 is a schematic flow diagram illustrating a method of operation of the system 300 in a first mode, in which a bias is measured and determined for each of a plurality of predetermined drilling locations on a workpiece. In a first step 401, the robotic drill is actuated to contact the surface of the workpiece contacting portion of the clamp to the workpiece to be machined. In a second step 402, a first position of the drilling tool relative to the workpiece is measured using the metrology system. In a third step 403, the servo motor is actuated to drive the clamp on to the workpiece to be machined, while measuring a force from the force sensor until a predetermined force has been reached. In a fourth step 404, a second position of the drilling tool relative to the workpiece is measured using the metrology system. In a fifth step 405, a bias is determined from a difference between the first and second measured positions. In a sixth step 406, the determined bias is stored for the predetermined location. The method may then be repeated for further predetermined locations on the workpiece until all locations for drilling operations have been covered.

[0082] In a second mode of operation, the controller may perform the method as outlined in FIG. 5. In a first step 501, a stored bias for a predetermined location of a workpiece to be machined is retrieved. In a second step 502, the robotic drill is actuated to contact the surface of the workpiece contacting portion of the clamp at the predetermined location offset by the retrieved bias. In a third step 503, the servo motor is actuated to drive the clamp on to the workpiece while measuring a force from the force sensor until a predetermined force has been reached. In a fourth step 504, the drilling tool is operated to drill a hole at the predetermined location of the workpiece. The method may then be repeated until all locations for drilling have been covered. The position of the drilling tool may continue to be measured during the second mode of operation, which can be used to update a stored bias for the predetermined location.

[0083] The second mode of operation may be carried out separately from the first mode, i.e. with the stored bias for each predetermined location having been previously determined.

[0084] The optical metrology system may operate by locating the position of multiple LEDs on the drilling tool 201 and workpiece holder 302 so that when the robotic drill 301 performs a drilling operation the optical metrology system enables the drilling tool to drill a hole in the workpiece to a greater degree of accuracy than may be possible using positional encoders on the robotic drill alone. The optical metrology system may for example have a positional accuracy within around 0.1 mm of a nominal target position, The bias between an unclamped and clamped position can be used by the controller to predict what bias or offset to apply to the robotic drill for future drilling operations. Multiple bias measurements may be incorporated into a machine learning algorithm to predict a bias to be used for a robotic drilling system.

[0085] FIG. 6 is a drawing indicating various component parts of an example robotic drilling system 600, including a robotic drill 601 with a tool frame 602 comprising a drilling tool and clamp of the type described above. The robotic drill 601 is mounted on a robot base frame 603 that is associated with a robot system origin 604. A workpiece 605 to be machined is mounted on a workpiece holder 606, which may be attached to the robot base frame 603. In operation, the robot tool frame 602 is moved from the system origin 604 to a target 607, which may be determined by a 3D CAD model relative to an origin 608 of the workpiece 605 or workpiece holder 606. Operation of the robotic drill 601 may then be as described above.

[0086] FIG. 7 illustrates a more detailed example of a clamp attached to a drilling tool 700 of a robotic drill 701, the clamp having the general form as shown in FIG. 2 and described above. The clamp comprises an electro-mechanical servo-driven mechanism 702 for high precision clamp-up, and has a non-skid surface 703 at the clamp “nose”, or workpiece contacting portion. An integrated force feedback system 704 enables the servo to be driven until a desired force is met. Linear rails 705 with a pulley or timing belt ensure that force is applied to the structure, i.e. the workpiece to be machined, that is central to the clamp nose and not offset, which can amplify any skid. A rigid C-shaped frame 706 is designed to prevent distortion, deflection and skid of the clamp nose.

[0087] Other embodiments are intentionally within the scope of the invention as defined by the appended claims.