Manufacturing system and method

Abstract

The manufacturing system includes a coordinate positioning machine (10) having a structure movable within a working volume of the machine, the coordinate positioning machine having a drive for moving the structure around the working volume and a coordinate positioning machine for determining the position of the structure within the working volume to a first accuracy, and the machine (10) removably coupled to a measuring device (30) that measures the position of the structure to a second accuracy higher than the first accuracy when the structure is moved by the drive and the machine (10) is coupled to the measuring device (30).

Description

[Technical field]

[0001] SYSTEMS AND METHODS FOR MANUFACTURING FIELD OF THEINVENTION The present invention relates to manufacturing systems and methods, particularly but not exclusively involving the use of articulated robots. [Background technology]

[0002] Articulated robots are commonly used in a variety of manufacturing applications including assembly, welding, gluing, painting, picking and placing (e.g. printed circuit boards), packaging and labeling, palletizing, product inspection, etc. Their versatility and robustness, long reach and flexibility of movement make them ideal for use in production environments.

[0003] An articulated robot (or "robot" for short) is shown diagrammatically in Figure 1 of the accompanying drawings and comprises an articulated arm 1 extending from a fixed base 2 to a movable flange 3 which supports a tool (or effector end) 4. Typically the flange 3 is provided with a coupling which enables the tool 4 to be conveniently interchangeable so that a variety of tools or end effectors can be used depending on the application involved. Examples include grippers, vacuum cups, cutting tools (including both mechanical and laser cutting tools), drilling tools, milling tools, deburring tools, welding tools and other speciality tools.

[0004] The arm 1 includes multiple segments 5 connected by multiple revolute joints 6, forming a mechanical linkage from one end to the other. In the example shown in Figure 1, there are seven revolute joints 6, which alternate between revolute joints with their rotation axes perpendicular to the longitudinal axis of the connected segments 5 and revolute joints with their rotation axes parallel to the longitudinal axis of the connected segments 5.

[0005] Probably the most common arrangement for an industrial robot is to have six revolute joints, but a robot may also have one or more linear joints. Having multiple joints allows flexibility in moving the tool 4 around the working volume and manipulating it into a variety of different poses. The degree of flexibility can be altered by adding or removing joints in the arm.

[0006] The downside of having additional joints (and therefore additional flexibility) is that each joint contributes a position error or uncertainty, and because of the serial nature of the linkage, these errors are cumulative. It is important to tune the robot to map these errors and uncertainties.

[0007] However, calibration of any type of non-Cartesian machine is a significant challenge, especially for articulated arms with multiple revolute joints, such as that shown in Figure 1, which are not fixed to each other and can combine in complex ways to position the tool in the working volume. Calibration of Cartesian machines is usually simpler, since such machines have three well-defined axes fixed to each other in an orthogonal arrangement, and each axis is largely independent of the others. For articulated robots, the position and orientation of each axis depends on the positions and orientations of the other axes, so the calibration is different for each pose of the machine.

[0008] Many calibration techniques have a common goal of specifying a parametric model of the relevant machine, where multiple parameters are used to characterize the machine geometry. Uncalibrated values ​​are initially assigned to these parameters as a starting point for the machine geometry. During calibration, the machine is moved to a variety of different poses (based on the current estimates of the machine parameters). For each pose, a calibrated measurement device is used to measure the actual pose, so that a measure of the error between the expected machine pose and the actual machine pose can be determined.

[0009] The task of calibrating the machine then becomes one of determining the settings of the machine's various parameter values ​​that minimize the error, using known numerical optimization or error minimization techniques. An example of such a technique is the well-known Levenberg-Marquardt algorithm, which uses a least-squares approach to minimize the error knowing the derivative of the error according to each optimized parameter ("A Method for Solving Certain Nonlinear Problems in the Least Squares Method", Kenneth Levenberg, 1944, Quarterly of Applied Mathematics, 2:164-168, and "An Algorithm for the Least-Square Estimation of Nonlinear Parameters", Donald Marquardt, 1963, SIAM Journal on Applied Mathematics, 11(2):431-441). Other techniques are also possible, such as those based on the maximum likelihood approach.

[0010] For a robot such as that shown in FIG. 1, these machine parameters may include various geometric parameters such as the length of each segment 5, the rotational angular offset of each revolute joint 6 (angle from the encoder plus an actual calibrated offset), and various mechanical parameters such as joint compliance and friction. When all of these machine parameters are known and properly calibrated, it is possible to more reliably predict where the tool 4 will actually be when the various joints 6 are commanded by the robot controller 7 to move to their different respective positions. In other words, the machine parameters resulting from such a calibration provide a more accurate characterization of the machine geometry.

[0011] DE3504464C1 describes the use of a number of telescopic rods which are temporarily attached to an articulated robot for a calibration procedure. Summary of the Invention [Problem to be solved by the invention]

[0012] However, even after calibration of such articulated robots, errors remain, and these errors accumulate due to the serial nature of the mechanical linkages. As a result, the accuracy and repeatability of articulated robots is usually not as good as, for example, conventional 3-axis Cartesian machines. Thus, although articulated robots have the advantage of greater reach, greater flexibility and versatility, they are usually not suitable for use in the most demanding applications where high precision and repeatability are required.

[0013] It would be desirable to address the above shortcomings in order to provide a system that has improved accuracy and / or repeatability but can benefit from the reach and flexibility of articulated robots. [Means for solving the problem]

[0014] According to the present invention there is provided a manufacturing system including a coordinate positioning machine having a structure movable within a working volume of the machine, a drive arrangement for moving the structure about the working volume, and a positioning machine for determining a position of the structure within the working volume to a first accuracy, and wherein the machine is removably coupleable to a metrology arrangement such that when the machine is coupled to a metrology arrangement and the structure is moved by the drive arrangement the metrology arrangement is capable of measuring the position of the structure to a second accuracy higher than the first accuracy.

[0015] If the machine is coupled to a metrology device, the predetermined zone can be regulated within the working volume within which the metrology device can measure the position of the structure with a second degree of accuracy. Measurement equipment , defining a plurality of corresponding respective zones within the working volume.

[0016] The actuator may include multiple segments or links connected or arranged in series by multiple motorized joints. The joints may include at least one revolute joint. The joints may include at least one linear joint. The joints may include only revolute joints.

[0017] The machine may be a robot. The machine may be a serial robot. The machine may be an industrial robot. The machine may be a robot arm. The machine may be another type of machine such as a delta robot (US4976582) or a cable robot (US 2009 / 0066100) or a tri-glide arrangement (US 2003 / 0005786).

[0018] The positioning machine may include a plurality of measurement transducers (eg, encoders) arranged in series to provide a corresponding respective plurality of measurements from which the position of the structure can be determined to a first degree of accuracy.

[0019] The metrology device may include a plurality of measurement transducers (eg, encoders) in a parallel arrangement to provide a corresponding plurality of respective measurements from which the position of the structure can be determined to a second degree of accuracy.

[0020] The measurement device may include six such measurement transducers.

[0021] The metrology device may be a hexapod metrology device.

[0022] The machine may be operable (or adapted) to perform at least one of the following types of operations with the machine also coupled to the metrology device: a measuring operation, a probing operation, a machining operation, a gripping operation, a drilling operation, a painting operation, a pick and place operation, and a gluing operation.

[0023] The machine may be couplable to at least one tool, and the machine is also coupled to a metrology device. The machine may have couplings that allow it to couple to both the at least one tool and the metrology device, such that the machine is coupled to both simultaneously. The machine can be couplable to the at least one tool and the metrology device simultaneously.

[0024] The tool may be for performing an operation such as a measurement operation, a probing operation (e.g., a touch trigger operation or a scanning operation using a contact or non-contact probe), a machining operation, a gripping operation, a drilling operation, a painting device, a pick-and-place operation, or a gluing operation.

[0025] The at least one tool may include at least one of a measurement probe, a gripper, a drilling tool, a welding tool, a bonding tool, and a painting tool. The measurement probe may be a contact probe or a non-contact (e.g., optical) probe. The measurement probe may be a touch-trigger probe or a scanning probe.

[0026] It will be appreciated that the metrology arrangement is not intended for calibration purposes only. In other words, the metrology device is only installed during a set-up and calibration procedure that is performed before the machine is put into service, after which the metrology device is removed from the machine. Rather, the metrology device is placed during actual operational use of the machine, and effectively becomes part of the machine during operational use. In this way, the metrology device can be used to provide metrology results (measurements) related to events that occur during operational use (such as touch-trigger events and pick-and-place events). This is in contrast to the telescoping calibration rod described in DE3504464C1, which is intended for calibration purposes only.

[0027] At least one tool may be provided as an integral part of the metrology device, thereby forming a "smart tool," as described in more detail below. Thus, the metrology device and tool are effectively a single entity to which a machine can be coupled, such that a machine can be coupled to the tool by being coupled to the metrology device, or vice versa. Alternatively, the tool and metrology device may be provided separately, and the machine may be coupled to the tool and metrology device separately.

[0028] The coupling between the coordinate positioning machine and the measuring device may be a physical and / or mechanical coupling.

[0029] The coupling between the coordinate measuring machine and the measuring device is Kinematic coupling ( Kinematic or pseudo-kinematic coupling ) It could be.

[0030] According to another aspect of the invention, there is provided a method of controlling a manufacturing system as described above, the method including performing a first operation on a machine decoupled from the metrology device, determining a position of the structure during the first operation using a positioning arrangement of the machine, coupling the machine to the metrology device, performing a second operation on the machine coupled to the metrology device, measuring a position of the structure during the second operation using the metrology device, and decoupling the machine from the metrology device.

[0031] The first operation is outside and the second operation is performed on the Inside The first action may include removing the machine from another such zone.

[0032] The second operation may include at least one of a measuring operation, a machining operation, and a bonding operation.

[0033] The method may include, for example, removably coupling the machine to a tool required for the second operation prior to coupling to the metrology device.

[0034] With the coordinate positioning machine coupled to the metrology device (e.g., when performing the second operation), the positioning arrangement of the coordinate positioning machine may still be present and / or in place. The positioning arrangement of the coordinate positioning machine may be operable during the second operation.

[0035] The coordinate positioning machine may be controlled during the second operation based on position data from the positioning arrangement of the coordinate positioning machine.

[0036] The coordinate positioning machine may be controlled during the second operation based on position data from the measuring device (so that the measuring device effectively replaces the positioning machine).

[0037] The coordinate positioning machine can be controlled during the second operation based on a combination of position data from the positioning device and the measuring device.

[0038] The structure may include one or more elements of a coordinate positioning machine, for example, the final elements of a serial mechanical linkage, and / or components attached to such elements in a known relationship.

[0039] Measuring or determining the position of a structure may include measuring or determining the position of a component, such as a tool, attached to the structure in a known spatial relationship, where due to the known spatial relationship, determining the position of the structure is substantially equivalent to or equivalent to (and / or may be necessary for) determining the position of the attached component or tool.

[0040] Measuring the "position" of a structure should be understood as measuring the position and / or orientation of the structure in an appropriate number of degrees of freedom. For example, if the position is measured in six degrees of freedom, then both the position and orientation of the structure are determined. However, if the position is measured in only three degrees of freedom, this may or may not include determining the orientation of the structure. The term "measuring the position" should be interpreted accordingly.

[0041] The term "coupleable" as used herein may be taken to mean, for example, releasably coupleable, or easily releasably coupleable, or easily coupleable and decoupleable in such a way that the coordinate positioning machine can be coupled to the measuring device and decoupled from the measuring device again relatively easily and / or without manual (human) involvement or intervention, i.e. in an automated manner. The coupled state is not intended to be a permanent or semi-permanent state, but only a temporary state, in the sense that the coordinate positioning machine is coupled to the measuring device only temporarily for a specific operation or series of operations. For this purpose, dedicated coupling elements may be provided on both the coordinate positioning machine and the measuring device, the coupling elements being adapted to be engageable and disengageable with each other in an automated manner.

[0042] The positions measured before and after coupling the coordinate positioning machine to the measurement device may have different frames of reference. The reference frames can be related to each other through a kinematic coupling arrangement between the coordinate positioning machine and the measurement device to ensure that the relative positioning between them is accurate, known and repeatable.

[0043] The coupling may be a physical and / or mechanical coupling. This is in contrast to, for example, an optical tracking system in which the optical tracker is permanently attached (i.e., not removably coupled in the sense intended herein) and can be switched on and off as needed; such a coupling is switchable (removable), but is an optical coupling, rather than a physical or mechanical coupling. When an optical metrology device is used in an embodiment of the invention, it is removably coupled to the coordinate positioning machine in a physical or mechanical manner, such that the optical metrology device can selectively form or not form part of the coordinate positioning machine, as desired. This should be distinguished from simply switching the optical metrology system on or off, which is not considered a coupling and decoupling in the sense intended herein.

[0044] The coupling may be an automatic coupling rather than a manual coupling. This allows the manufacturing process to proceed without manual intervention when coupling and uncoupling the coordinate positioning machine to the measuring device. Thus, the machine can move from a low accuracy zone to a high accuracy zone, perform an operation in the high accuracy zone, and then move back from the high accuracy zone to the low accuracy zone to perform a further operation without manual intervention. Automatic coupling is in contrast to coupling, which requires manual attachment of the surveying device to the coordinate positioning machine.

[0045] The manufacturing system described above may comprise a machine controller operable (or adapted) to carry out the control method described above.

[0046] According to another aspect of the invention, the second precision is different from, but not necessarily lower than, the first precision. The metrology device is a positioning machine for measuring the position of the structure to the second precision.

[0047] According to another aspect of the invention there is provided a computer program which, when executed by a computer or machine controller, causes the computer or machine controller to carry out the above method according to the invention. The program may be carried on a carrier medium. The carrier medium may be a storage medium. The carrier medium may be a transmission medium.

[0048] According to another aspect of the present invention, there is provided a computer readable medium having stored therein computer program instructions for controlling a computer or machine controller to carry out the above-described method according to the present invention. [Brief description of the drawings]

[0049] Reference will now be made, by way of example, to the accompanying drawings in which: [Figure 1] FIG. 1, as mentioned above, is a schematic diagram of an articulated robot. [Figure 2A]FIG. 2A illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2B] FIG. 2B illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2C] FIG. 2C illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2D] FIG. 2D illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2E] FIG. 2E illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2F] FIG. 2F illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2G] FIG. 2G illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2H] FIG. 2H illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2I] FIG. 2I illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Figure 2J] FIG. 2J illustrates various stages of a manufacturing system and method according to an embodiment of the present invention. [Diagram 3] FIG. 3 shows the hexapod metrology setup of FIGS. 2A through 2J in greater detail. [Figure 4A] FIG. 4A illustrates the concept of "zones" according to an embodiment of the present invention. [Figure 4B] FIG. 4B illustrates the concept of "zones" according to an embodiment of the present invention. [Figure 4C] FIG. 4C illustrates the concept of "zones" according to an embodiment of the present invention. [Figure 4D] FIG. 4D illustrates the concept of "zones" according to an embodiment of the present invention. [Figure 5A]FIG. 5A illustrates a manufacturing system according to another embodiment of the present invention. [Figure 5B] FIG. 5B shows the hexapod metrology device of FIG. 5A in greater detail. [Figure 6] FIG. 6 illustrates a manufacturing system according to yet another embodiment of the present invention. [Figure 7] FIG. 7 illustrates a manufacturing system according to yet another embodiment of the present invention. [Figure 8A] FIG. 8A illustrates a manufacturing system not embodying the present invention in which a drilling operation is followed by an assembly operation. [Figure 8B] FIG. 8B illustrates two alternative manufacturing systems embodying the present invention for performing operations equivalent to those of FIG. 8A. [Figure 8C] FIG. 8C illustrates two alternative manufacturing systems embodying the present invention for performing operations equivalent to those of FIG. 8A. [Figure 9A] FIG. 9A illustrates a manufacturing system and method embodying the present invention in which a tool is picked up by a robot from a rack prior to engagement with a metrology device. [Figure 9B] FIG. 9B illustrates a manufacturing system and method embodying the present invention in which the tool is picked up by a robot from a rack prior to engagement with a metrology device. [Figure 9C] FIG. 9C illustrates a manufacturing system and method embodying the present invention in which the tool is picked up by a robot from a rack prior to engagement with a metrology device. [Figure 9D] FIG. 9D illustrates a manufacturing system and method embodying the present invention in which the tool is picked up by a robot from a rack prior to engagement with a metrology device. [Figure 10] FIG. 10 shows an embodiment in which an optical hexapod metrology arrangement is used instead of a physical hexapod metrology arrangement. [Figure 11] FIG. 11 shows an alternative type of optical metrology device to that of FIG. [Figure 12]FIG. 12 shows an embodiment in which a serial kinematic Cartesian coordinate positioner is used instead of a robot. [Figure 13] FIG. 13 is a schematic diagram of the "modular metrology" concept according to an embodiment of the present invention. [Figure 14] FIG. 14 shows an extension of the "modular metrology" concept of FIG. 13, introducing the "modular tool" concept in addition to the "modular metrology" concept. [Figure 15] FIG. 15 introduces the concept of a "smart tool" to the concept shown in FIG. 14, where the tool is provided with at least one metrology device (or the tool is provided with an integrated metrology device). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] A manufacturing system and method according to a first embodiment of the invention will now be described with reference to Figures 2A to 2J. The manufacturing system, together with other machines and workstations not shown in Figure 2A, may form part of a wider production environment (e.g. a factory) and the described manufacturing method may form part of a wider production process for working with workpieces 20.

[0051] The manufacturing system comprises an articulated robot 10 generally similar to that described above with reference to Fig. 1. The robot 10 of Fig. 2A differs from the robot 10 of Fig. 1 by the tool coupled to the final segment 5 (the flange 3 of Fig. 1 is not present in the robot 10 of Fig. 1, but could in fact be provided). Due to the adaptability of the robot, it is common to couple different types of tools to the robot, or to couple several tools, as shown in Fig. 2A. Thus, instead of the tool 4 shown in Fig. 1, the robot 10 of Fig. 2A comprises a gripper 14 and a coupling element 12.

[0052] The purpose of the coupling element 12 will become clearer below, while the gripper 14 is provided to pick up and transport the workpiece 20 supported on the support 22. As part of a wider manufacturing process, the workpiece 20 may have been worked on (e.g. machined) in another working area of ​​another workstation production environment and then transported to the position shown in FIG. 2A by a conveyor belt (e.g. such that the support 22 is a conveyor belt). Alternatively, the robot 10 itself may have previously worked on the workpiece 20 in situ, for example using a different tool than that shown in FIG. 2A, with the support 22 being a fixed worktable. The concept of interchangeable tools is explained in more detail below with reference to FIG. 9.

[0053] In this example, the workpiece 20 has reached a stage in the manufacturing process where it needs to be measured to check it against acceptable tolerances, in other words to check that it has the correct expected dimensions. As mentioned above, industrial robots are very versatile but they typically have relatively low positioning accuracy, at least compared to conventional coordinate measuring machines, making them unsuitable to carry out the high precision measurement operations required in this example.

[0054] Rather than moving the workpiece 20 to an entirely separate coordinate measuring machine to carry out the high precision measurements currently required at this stage of the manufacturing process, as would normally occur, the applicants have instead devised an approach that combines the versatility of a standard industrial robot with the high precision of a more traditional coordinate measuring machine.

[0055] With the above in mind and referring to Figure 2B, the robot 10 is controlled to position the gripper 14 over the workpiece 20. The gripper 14, which is itself articulated and somewhat extendable, is then controlled to grasp and pick up the workpiece 20. Then, as shown in Figure 2C, with the workpiece 20 carried by the gripper 14, the robot 10 and gripper 14 are controlled to move the workpiece 20 across the metrology device 30 and position the workpiece 20 within its working volume.

[0056] Before describing the next step with reference to Figure 2D, the metrology apparatus 30 will first be described in more detail with reference to Figure 3. The metrology apparatus 30 generally comprises first and second structures 32, 34 supported and moved relative to one another by a number of telescopic or extendable legs 36 disposed therebetween. The first and second structures 32, 34 may also be referred to as platforms or stages, and the extendable legs 36 may also be referred to as struts. As there are six such extendable legs 36, this arrangement is generally referred to as a hexapod, and as a result the metrology apparatus 30 may be referred to as a hexapod metrology apparatus 30.

[0057] The extendable legs 36 are typically mounted on structures 32 and 34 via ball joints 38, with each leg 6 either having its own ball joint 38 at one or both ends (as shown in FIG. 3) or sharing a ball joint 8 with an adjacent leg 36 at one or both ends. Each extendable leg 36 is typically formed as a pair of tubes, one slidable within the other, as indicated by arrow 35, to allow extension and retraction of the extendable leg 36.

[0058] The first structure 32 is movable relative to the second structure 34, as indicated by arrow 31 in Figure 3, and the relative position at any instant between the first and second structures 32, 34 is monitored by a number of length measurement transducers 37, for example one length measurement transducer 37 associated with each extendable leg 36. Each length measurement transducer 37 may include an encoder scale paired with a readhead, with the encoder scale suitably mounted on one of a pair of telescoping tubes and the readhead suitably mounted on the other. Thus, extension of the leg 36 moves the encoder scale past the readhead, thereby generating a signal based on the amount of extension.

[0059] Signals or readings from each transducer 37 are provided to a computer controller 39 which is operable to calculate, based on these signals or readings, the relative position between the first and second structures 32, 34. By having six such length measuring transducers 37, the relative position can be measured in six corresponding respective degrees of freedom (three translational and three rotational degrees of freedom).

[0060] In the configuration shown in FIG. 3, the structure 34 is provided as part of the fixed structure of the machine, and the other structure 32 moves 31 relative to the fixed structure. A measurement probe 40 may be attached to the upper (moving) structure 32 and the workpiece 20 may be attached to the lower (fixed) structure 34 so that a measurement or probing operation can be performed on the workpiece 20. A working volume 42 is defined between the upper structure 32 and the lower structure 34 when they are at their furthest apart position with the tool 40 moving within the working volume 42. Although the arrow 31 is shown to indicate translational motion, the structure 32 may also be rotated. In another configuration, the upper structure 32 may be fixed and the lower structure 34 may be movable (indicated by arrow 33), with the probe 40 mounted on a lower surface of the lower structure 34 and the workpiece mounted below a portion of the fixed structure such that the working volume (or operating volume) of the apparatus is below the lower structure 34 rather than above it.

[0061] However, rather than considering the workload of the metrology device 30 itself, it is perhaps more appropriate to consider the workload of the robot 10 when coupled to the metrology device 30. This is because the robot 10 is still a running machine, and the metrology device 30 is not an independent machine in itself, since it mainly only has measuring means (i.e. the plurality of length measuring transducers 37) and no independent drive means.

[0062] Because the metrology device 30 is passive and does not require any driving components that add weight and generate heat, it is possible to control and reduce measurement errors caused by inertia and thermal distortion of parts (including the measurement scale used to measure distances). Furthermore, because the metrology device 30 does not require any driving components, it can provide low friction joints, whereas drives usually require more robust and substantial joints that necessarily have a higher degree of friction, especially when under load. Thus, the joints of the metrology device 30 can be of the low friction type and are not subject to the same loads as when combined with a drive. Thus, hysteresis effects, whereby different measurements may be recorded depending on the direction of approaching the workpiece, can be reduced by having a dedicated metrology device 30 without any driving components. Thus, by being dedicated to metrology, the metrology device 30 can provide very high accuracy position measurements and can be used to selectively convert a relatively low accuracy machine (e.g., the robot 10) into a relatively high accuracy machine.

[0063] The measuring device 30 may not be considered an independent machine in itself since there is no drive means, but rather the robot 10 may function as a stand-alone work coordinate system, and even without the measuring device 30 the positioning machine has its own drive means and its own positioning means for determining the position of the work tool, using the outputs from the rotary encoders associated with the various rotary joints 6 described with reference to Figure 1.

[0064] Thus, in an embodiment of the invention, the robot 10 is still a machine, but is coupled to a metrology device 30 when necessary, i.e., when greater precision is required. In the embodiment described with reference to Figures 2 and 3, the hexapod metrology device 30 has a more limited range or workload than the robot 10 when it is coupled to the metrology device 30, so that the workload of the combined device (robot 10 and metrology device 30) is limited by the more limited range of movement of the metrology device 30, thereby creating what can be considered a "zone" of high precision within the overall working volume of the robot 10 itself.

[0065] This "zone" concept will now be explained with reference to Figures 4A to 4D. Figure 4A is a schematic diagram of a robot 10 with a working volume W encompassing a number of different working areas A1 to A6. The working volume may also be called a working range, and the working areas may also be called stations or workstations. The intention is that in each of the different working areas A1 to A6, a different task is performed by the robot 10, for example drilling, welding, assembly, cleaning, etc. In the position shown in Figure 4A, the robot 10 is performing operations in a working area A1 equivalent to that shown in Figures 2A and 2B, the positioning of the robot 10 is still based on the robot's own measuring transducers (positioning arrangement), i.e. with a relatively low accuracy. This applies throughout the shaded area in Figure 4A.

[0066] As shown in FIG 4B, when a higher precision operation is required, the robot 10 moves to working area A2, which provides a high precision zone Z1 within the working volume W of the robot 10. The manner in which the transition from the low precision working volume W to the high precision zone Z1 is made is described in more detail below. Subsequently, as shown in FIG 4C, the robot 10 moves across working area A5, which provides another high precision zone Z3 within the working volume W of the robot 10. Next, as shown in FIG 4D, the robot 10 moves across working area A4, which is outside any of the high precision zones Z1 to Z3 and therefore within the low precision working volume W of the robot 10.

[0067] Returning now to steps 2A through 2J, it has been described above how robot 10 is commanded to move workpiece 20 from the position shown in Figure 2A (corresponding to station A1 in Figure 4A) to metrology device 30 and for gripper 14 to release workpiece 20 and place it into metrology device 30 as shown in Figure 2C (corresponding to station A2 or zone Z1 in Figure 4B). Note that robot 10 and gripper 14 are controlled by a controller (not shown for clarity) equivalent to controller 7 in Figure 1.

[0068] Next, as shown in Figure 2D, the robot 10 is controlled to move up and down around the upper platform 32 of the metrology apparatus 30, positioning the coupling element 12 on the upper platform 32 and then lowering it down to engage and couple to the upper platform 32. Figure 2E shows the coupling element 12 of the robot 10 coupled to the upper platform 32 of the metrology apparatus 30, with the gripper 14 out of the way.

[0069] With the robot 10 coupled to the metrology device 30, a measurement operation is performed as shown in Figures 2F and 2G, where the robot 10 moves the measurement probe 40 to contact and engage a first feature (corner) of the workpiece 20 in Figure 2, and then to contact and engage a second feature (corner) of the workpiece 20 in Figure 2G. As is well known, when a touch occurs, a deflectable stylus of the measurement probe 40 deflects and a touch trigger event can be generated to record the position of the measurement probe 40 (and thus the touch point).

[0070] When coupled to the metrology device 30 in this manner, the robot 10 is driven by its own drive means and its position is controlled based on feedback from its own positioning machine (i.e., a rotary encoder), but the metrology device 30 is also able to more accurately determine the position of the touch-trigger event shown in Figures 2F and 2G in situ based on signals from the measurement transducer 37 of the metrology device 30.

[0071] The measurement operation may include making touch-trigger measurements where the measurement probe 40 contacts the surface of the workpiece 20, leaves it, then contacts it again at a different location, and so on, recording the location of each touch-trigger event. The measurement operation may also include a scanning operation where the measurement probe 40 is held in contact with the surface of the workpiece 20 while it is scanned along the surface, or a combination of these is possible using an appropriate type of measurement probe 40.

[0072] Once the measurement operation is completed, the measurement probe 40 is moved away from the workpiece 20 and the coupling element 12 is disengaged or detached from the upper platform 32 of the metrology device 30, as shown in Figure 2H. The gripper is then used again to pick up the workpiece 20, as shown in Figure 2I, and return the workpiece 20 to its original working area (corresponding to working area A1 in Figure 4A), as shown in Figure 2J. After disengagement from the metrology device 30 in Figure 2H, the robot 10 is again operating within its normal (low-precision) working volume, outside the high-precision zone Z1 defined by the metrology device 30.

[0073] The coupling between the coupling element 12 and the structure 32 is preferably in the form of a kinematic or pseudo-kinematic coupling. When placing a body relative to another body, kinematic design considerations should be met by constraining the degrees of freedom of the body's motion using a minimum number of constraints, and in particular over-constraining should be avoided. Over-constraining would result in multiple contact points between the two bodies, and one body may come to rest in multiple positions relative to the other. Thus, the position of the body cannot be reproduced because it is not known where the body will come to rest in several positions. In particular, when there is over-constraint, there is a discrepancy between the constraints that have been placed, so it is not possible to determine with certainty which combination of constraints determines the actual position of the body. These concepts are described in H. J. J. Braddick, "Mechanical Design of Experimental Apparatus", Chapman & Hall, London, 1960, pp. 11-30.

[0074] The use of a kinematic coupling is beneficial as it provides a very accurate and repeatable coupling, so that the position of one half of the coupling (coupling element 12) relative to the other half of the coupling (structure 32) is known with a high degree of certainty for each of a number of separate and independent couplings (associated with a number of corresponding work steps) that may be performed in a typical manufacturing method. This serves to tie or relate the coordinate positioning frame to the metrology device frame of reference, thereby effectively creating a common overall frame of reference for the coupled machines.

[0075] Such a kinematic coupling has a minimum number of contact points (or point-like contacts) to provide ideal constraints, and is also very effective at isolating strains as one half of the coupling is transferred to the other half of the coupling. Thus, the coupling helps to prevent strains in the coupling element 12 from being transmitted to the structure 32 (and thus to the metrology device 30). This provides a well-delineated metrology frame with a sufficient degree of mechanical isolation from the robot 10.

[0076] In particular, in this embodiment, coupling element 12 includes a set of three balls (only two are shown in the schematic diagram) that provide three contact points in accordance with kinematic design principles. The top surface of structure 32 may conveniently be provided with a corresponding set of grooves into which the balls are disposed when coupled, again in accordance with kinematic design principles, to provide six contact points for constraining coupling element 12 relative to structure 32 in six degrees of freedom. Alternatively, balls may instead be provided in grooves on structure 32 and coupling element 12. For further details, reference is made to the Braddick documents cited above.

[0077] Alternatively, a pseudo-kinematic coupling can be provided in the form of multiple elastic spacers or pads instead of rigid balls, for example three such spacers arranged at the corners of a triangle. This provides some degree of kinematic coupling even though the contact points are not point-like but spread over a small area of ​​the elastic spacers. The use of elastic spacers (e.g. made of rubber) is beneficial as they act to absorb some vibrations from the drive of the robot 10, so that they are not transmitted to the metrology device 30. Alternatively, the three rigid balls in one half of the coupling could contact flat surfaces (rather than grooves) in the other half, or three corresponding cup-like recesses.

[0078] In summary, a manufacturing system embodying the invention described above comprises a coordinate positioning machine (e.g., robot 10) having a structure (e.g., a final segment of the robot to which a coupling element 12 and a gripper 14 are attached in a known relationship, or either or both of the coupling element 12 and the gripper 14). The structure is movable within a working volume of the machine (e.g., working volume W shown in FIG. 4). The coordinate positioning machine has its own drive (e.g., a motor associated with rotary joint 6 of FIG. 1) for moving the structure around the working volume, and a positioning mechanism (e.g., a rotary encoder and associated processing means associated with rotary joint 6 of FIG. 1) for determining the position of the structure within the working volume to a first (relatively low) degree of accuracy. Apart from this, the manufacturing system may optionally have a metrology device (e.g., a hexapod metrology device 30) to which the coordinate positioning machine may be coupled (e.g., by engaging the coupling element 12 with the platform 32) so that the machine is adapted to measure the position of the structure with a second accuracy higher than the first accuracy, in which a predetermined (relatively high accuracy) zone is defined within the working volume of the metrology device, in which the structure is moved by the drive. It should be understood that the position of the structure may be measured directly or indirectly. For example, a user may be more interested in the position of the tool 4 or the measurement probe 40 than the structure to which they are attached, but the tool 4 and the measurement probe 40 are attached to the structure in a known relationship, so that determining the position of the tool 4 or the measurement probe 40 effectively involves at least implicitly determining the position of the structure to which it is attached.

[0079] In such a manufacturing system, a manufacturing method can be performed in which a first operation is performed outside of a given zone (hence a component such as a gripper coupled in a known relationship to the structure), the machine is decoupled from the metrology device, and the position of the structure (hence a component such as a gripper coupled in a known relationship to the structure) during the first operation is determined using a positioning machine of the machine. The machine is then coupled to the metrology device and a second operation is performed within the zone with the machine coupled to the metrology device. The position of the structure (hence a component such as a measurement probe coupled in a known relationship to the structure) during the second operation is determined using the metrology device. The machine is then decoupled from the metrology device and begins operating again within a larger (less accurate) working volume.

[0080] Figure 5A is a schematic diagram of a manufacturing system according to another embodiment of the invention, which also comprises an articulated robot 10, which is generally similar to that of the previous embodiment described with reference to Figure 2, except that the coupling element 12 and the gripper 14 in Figure 5A are provided in a different form than the equivalent parts in Figure 2, the main difference being the form of the coupling element 12 and how it couples to the structure 32 of the metrology device 30.

[0081] The metrology device 30 of Fig. 5A is shown in more detail in Fig. 5B and is similar to that of Figs. 2 and 3. The metrology device 30 of Figs. 5A and 5B differs in that a coupling element 52 is provided on the structure 32 (this is only shown diagrammatically in Fig. 5B, in reality there is no need for an actual block feature as shown in Fig. 5A, but it docks directly in some suitable way with the coupling element 12, e.g. the structure 32). Furthermore, the metrology device 30 of Figs. 5A and 5B does not comprise an integrated measurement probe 40. In this embodiment of the manufacturing system, the measurement probe 40 is not supported (within its working volume) on the underside of the platform 32 of the metrology device 30 as in Fig. 2, but is provided outside the working volume of the metrology device 30, as a fixed probe attached to a fixed part of the machine (in this example, under a fixed overhang). This emphasizes the above, that it is appropriate to regulate or take into account the work volume of the robot 10 when coupled to the metrology device 30, and not the work volume of the metrology device 30 itself. 5, the metrology device 30 provides a high-precision metrology frame that can be docked to the robot 10, and it is clear that no tools (e.g. measurement probes) are provided and the robot 10 is otherwise unchanged (i.e. retains its usual drive and positioning devices), thereby again defining a high-precision zone within the overall workload of the robot 10.

[0082] 5, to engage or enter the high precision zone, in this embodiment the coupling element 12 of the robot 10 temporarily couples to a coupling element 52 provided on the structure 32 of the metrology device 30. When so coupled, the position of the workpiece 20 when it contacts the measurement probe 40 can be measured with high precision based on the output from the metrology device 30. Once the measurement operation is completed, the robot 10 can again disengage or detach from the metrology device 30 and return to a lower precision regime, ready to perform other tasks around its workload.

[0083] Fig. 6 is a schematic diagram of a manufacturing system according to another embodiment of the invention. The manufacturing system also includes an articulated robot 10 generally similar to that described with reference to Fig. 2. However, in the embodiment shown in Fig. 6, the gripper 14 and the coupling element 12 are supported on a common member 16 extending from the final segment of the robot 10. The structure 32 of the metrology element includes a slot 54 into which the member 16 can be inserted, so that the robot 10 can position the coupling element 12 on the structure 32 before moving into engagement with the structure 32. To accommodate this positioning, the measurement probe 40 is provided in an upward orientation on the substructure 34 of the metrology device 30, and the workpiece 20, rather than the measurement probe 40, is moved during a series of measurement operations.

[0084] As is evident from the manufacturing system embodying the invention shown in FIG. 7, the coupling of the robot 10 to a metrology device 30 as described above is not only useful when measurement operations are performed. The embodiment of FIG. 7 also illustrates the use of two high-precision zones provided by two different metrology devices 30 (e.g., equivalent to zones Z1 and Z2 in FIG. 4). Once coupled to a first metrology device 30 (left side of FIG. 7), a drilling operation is performed on the workpiece 20 using a drilling tool 42. The robot 10 then detaches from the first metrology device 30 and moves to and docks with a second metrology device 30 equipped with a measurement probe 40 for measuring the machined workpiece 20 with high precision. The workpiece 20 itself can be moved from one station to another, either manually or via a gripper of the robot 10 (not shown), in a similar manner as described with reference to FIG. 2.

[0085] In addition to providing a high precision zone within a manufacturing environment for measuring and drilling or machining, embodiments of the invention also find application in assembly operations, as will be described with reference to Figures 8A to 8C. Figure 8A shows a manufacturing system not embodying the invention, where a drilling operation is performed at a first station (left side of Figure 8A), followed by an assembly operation at a second station (right side of Figure 8A). The assembly operation involves inserting a spigot 44 into a hole drilled in a workpiece 20 in the first operation, which is of course merely an illustrative example. Due to the relatively low precision of the positioning placement of the robot 10, which involves very tight tolerances (such as a very tight fit of the spigot 44 into the drilled hole), the assembly operation is likely to fail in at least some instances (such as the spigot 44 not fitting completely into the hole, as shown on the right side of Figure 8A).

[0086] This situation is improved by a manufacturing system embodying the invention as shown in Figure 8B, where a dockable metrology device 30 provides a high precision zone for the assembly operation, allowing the spigot 44 to be inserted into the hole with a greater success rate, thereby improving the yield from the manufacturing process. The embodiment shown in Figure 8C takes this a step further by providing a high precision zone for both the drilling and assembly operations.

[0087] 9A to 9D show a manufacturing system and method according to another embodiment of the invention. As shown in FIG. 9A, a tool rack (or tool holder) 48 is provided within the working volume of the robot 10. Various tools are held in the rack 48, including a gripper 14, a milling tool 48, a laser cutting tool 46, a drilling tool 42 and a measurement probe 40. A modular coupling system is used, i.e., a tool is picked up from the rack 48 and used to perform an operation, allowing each tool to be removably coupled to the robot 10 as required, and then returned to the rack 48 to pick up another tool as required. The removable coupling allows this to be achieved relatively simply and in an automated manner without manual intervention, thus allowing use in automated manufacturing processes.

[0088] In the example shown in Fig. 9A, the robot 10 is controlled to pick up the drilling tool 42, while in Fig. 9B the robot 10 moves to a working area (high precision zone) where a metrology device 30 is provided. The robot 10 docks with the metrology device 30 as described above via coupling elements 12 and 52 provided on the robot 10 and on the metrology device 30, respectively. So docked and with the high precision metrology available from the metrology device 30, a precision drilling operation is performed on the workpiece 20, as shown in Fig. 9C. Once the operation is completed, the robot 10 can undock again from the metrology device 30 and move back to the lower precision area so that it can continue with other tasks, for example after returning the drilling tool 42 to the rack 48.

[0089] FIG. 10 shows an embodiment in which the physically extendable legs 36 of the hexapod metrology device of the previous embodiment are effectively replaced by optical equivalents. In other words, in this embodiment, an optical hexapod metrology device 60 is used instead of the physical hexapod metrology device 30. A plurality of retroreflectors 64 are disposed on a support structure 62, which is coupled to the robot 10 via the coupling elements 12, 52 described above. A plurality of light sources (e.g., lasers) 66 are disposed on a fixed structure above the support structure 62, each light source being paired with one of the retroreflectors 64 to direct its light to its paired retroreflector 64. These light sources 66 and retroreflectors 64 are equivalent to the ball joints 38 of FIGS. 3 and 5B, and the emitted and reflected light beams are equivalent to the extendable legs 36. Using well-known techniques, the various separations can be measured so that the position of the structure 62 can be determined, for example based on time of flight.

[0090] 11 shows an alternative type of optical metrology arrangement in which an optical target 64 is provided on the tool itself, in this example on the measurement probe 40, with a light source 66 interacting with the optical target 64 to provide multiple measurements of separation from which the position of the measurement probe 40 can be determined. Other optical or image-based (photogrammetry) metrology devices are similarly suitable.

[0091] In one embodiment of the present invention, optical and image-based metrology configurations can be used, but the mechanical hexapod-based metrology device 30 can be provided at a lower cost and with less technical complexity and problems than, for example, laser-based metrology devices. Laser tracking systems in particular can be very costly and complex to use effectively, at least in part because they require complex control systems to ensure that lasers (e.g., laser 66 in FIG. 10) are tracking their respective targets (e.g., reflector 64 in FIG. 10).

[0092] The mechanical hexapod-based metrology device 30 also has advantages over some image-based metrology devices with respect to the speed at which the position of the moving structure 22 can be determined or sampled. For image-based (photogrammetry) metrology devices, the sampling rate is essentially limited by the sampling rate of the image sensor, and further limited by the time it takes to perform complex calculations based on the large amount of image information to derive the position of the moving platform. For example, in the image-based system of EP 3054265 A1 it is stated that "the frame rate provided by the image detector is typically only a few hundred Hertz", which is described as being an advantage as it avoids the detection of unwanted high frequency movements such as vibrations.

[0093] However, applicants have recognized that a much higher dynamic bandwidth can be achieved by direct sampling of data from measurement transducers associated with the extendable legs of a hexapod metrology device. For example, a machine controller might typically request position data from an absolute encoder every 65 μs (15 kHz), although higher sampling rates are possible. Incremental encoder systems generate a continuous sinusoidal output, which allows for even finer motion control, limited only by the rate at which the continuous output can be sampled. Unlike image-based systems, the calculations required to determine the position of the movable structure from these values ​​are not overly time consuming.

[0094] Although a hexapod measurement device 30 capable of measuring in six degrees of freedom has been described above, the present invention is equally applicable in connection with measurement devices that are not in a hexapod configuration, such that fewer than six extendable legs 36 can be used when fewer degrees of freedom need to be measured. Measurement equipment It is also possible to use

[0095] Also, the invention is not limited to using such a robot as a coordinate positioning machine. For example, a serial kinematic Cartesian coordinate positioning machine 80 as shown in FIG. 12 can be used, with three parts connected in series that are movable along orthogonal axes x, y, and z, respectively. As with the other embodiments, the machine can be removably and temporarily coupled to a metrology device 30 to perform high-precision operations, and then again detached from the metrology device 30 to perform other tasks. For example, the machine can have a long y-axis with multiple different working areas defined along its y-axis, at least one of which has a high-precision zone with a dockable metrology device 30, as shown in FIG. 12.

[0096] The concept of zones has been explained above with reference to Figure 4, where high precision zones Z1 to Z3 are defined within the overall working volume W of the robot 10 (or other type of coordinate positioning machine). It will be understood that the robot 10 is not prevented from operating within any of these zones Z1 to Z3 with its own inherent precision, i.e. determining its position using its own positioning machine, since Figure 2C already gives an example where the robot 10 is not connected to the metrology device 30, but is nevertheless operating within the zone of the metrology device 30.

[0097] Following this, it will be clear that the invention is equally applicable to situations where high-precision and low-precision zones overlap in space, but not in time. This means that an embodiment is envisaged in which there is a defined working volume of the coordinate positioning machine, where during a first period the coordinate positioning machine uses less accurate position information from its own positioning device, then it couples to a more accurate positioning device (herein called the metrology device), and during a second period after the first period the coordinate positioning machine operates within the same working volume based on more accurate position information from the more accurate positioning device.

[0098] Such a scheme may, for example, be used on a machine tool where machining operations are performed using the positioning machine that comes standard with the machine tool, but for measurement or probing operations (to measure the machined workpiece) the machine tool can be coupled to a high precision positioning (metrology) device such as the hexapod metrology device described above to measure the workpiece, and then disconnected from the metrology device to perform additional machining operations, all in the same space.

[0099] The general concept underlying the embodiments of the present invention can be summarized as shown in FIG. 13, which shows, in a schematic form, a drive device for moving some structures around a working volume and a positioning machine for determining the position of the structures. The coordinate positioning machine can be removably coupled to one or more metrology devices that can provide position information independent of the position information provided by the positioning device of the coordinate positioning machine itself. To be useful, the position information from the one or more metrology devices will have some advantages over that from the position information from the positioning device of the coordinate positioning machine. For example, as mentioned above, it can be more accurate. Or, a particular type of metrology device can be used in combination with a particular tool that requires a controller that can only understand data from that particular type of metrology device, and not from the positioning device that is standard on the coordinate positioning machine.

[0100] The modular concept can be expanded as shown in Figure 14. In addition to the coordinate positioning machine being removably coupled to any one of one or more metrology devices, the coordinate positioning machine can also be removably coupled to any one of one or more tools, for example such a concept is used in the embodiment shown in Figure 9. Furthermore, as shown diagrammatically in Figure 15, the metrology device can be provided with its own tool (see metrology C / tool ​​C in Figure 15), in which case: Measurement equipmenteffectively functions like a "smart tool", i.e. a tool with its own metrology device, such a concept is used, for example, in the embodiment of Figure 2. Alternatively, the coordinate positioning machine can pick up and use another tool and couple it separately to the metrology device, in which case the metrology device is used purely for metrology, such a concept is used, for example, in the embodiment of Figure 9.

[0101] The positioning mechanism (rotary encoder) of the robot 10 described above allows the position of the tool to be explicitly determined. This provides a closed loop servo control system where motors within the robot 10 are commanded to drive the various revolute joints 6 in specific directions and by specific amounts to move the robot 10 into a new pose or direction, allowing measurements from the encoders to be used to determine the actual position and subsequent commands to be adjusted accordingly.

[0102] Alternatively, in embodiments of the invention having an open loop control system, it is possible to use, for example, a coordinate positioning machine that uses stepper motors where each stepper motor is commanded to move a particular number of steps, and the distance or angle moved in each step is calibrated to determine an expected position based on the number of steps each stepper motor moves, so that the actual position of the machine is not measured per se, but instead is inferred from the stepper counters and the geometry of the machine.

[0103] The term "positioning machine" as used herein is intended to cover both of the above types of machines, i.e., devices used to determine the position of the machine, whether directly or indirectly based on measurements from a set of measurement transducers, for example by counting steps.

[0104] A machine controller is also provided for controlling the operation of the robot (or other type of coordinate positioning machine). The machine controller may be a dedicated electronic control system and / or may include a computer operating under the control of a computer program. For example, the machine controller may comprise a real-time controller for providing low-level instructions to the coordinate positioning machine and a PC for operating the real-time controller.

[0105] It will be appreciated that the operation of the coordinate measuring machine may be controlled by a program running on the machine, by a program running on a coordinate measuring machine controller, such as the controller shown diagrammatically in Figure 1. Such a program may be stored on a computer readable medium or may be embodied in a signal, for example a downloadable data signal provided from an internet website. The appended claims are to be understood as covering an operating program on its own, or as a record on a carrier, or as a signal, or in any other form.

Claims

1. 1. A manufacturing system for performing a manufacturing method, the system comprising: a coordinate positioning machine having a structure movable within a working volume of the coordinate positioning machine, a drive for moving the structure around the working volume, a positioning arrangement for determining with a first accuracy the position of the structure within the working volume during a first operation of the manufacturing method, and a coupling; a separate measuring device to which the coordinate positioning machine is removably coupled via the coupling for a second operation of the manufacturing method, wherein when the coordinate positioning machine is coupled to the measuring device for the second operation, the structure is moved by the drive device of the coordinate positioning machine and the measuring device measures the position of the structure during the second operation with a second accuracy higher than the first accuracy; and Including, A manufacturing system, wherein the metrology device is a passive metrology device with no moving parts.

2. 2. The manufacturing system of claim 1 , wherein a predetermined zone when the coordinate positioning machine is coupled to the passive metrology device is defined within the working volume within which the passive metrology device can measure the position of the structure with the second accuracy.

3. The manufacturing system of claim 2 comprising a plurality of such passive metrology devices about said working volume to define a plurality of corresponding respective zones within said working volume.

4. The manufacturing system of claim 1 , 2 or 3 , wherein the drive comprises a plurality of segments connected in series by motorized joints.

5. The manufacturing system of claim 1 , wherein the coordinate positioning machine is a robotic arm.

6. 6. The manufacturing system of claim 1, wherein the positioning arrangement includes a plurality of measurement transducers arranged in series to provide a corresponding respective plurality of measurements by which the position of the structure can be determined to the first degree of accuracy.

7. 7. The manufacturing system of claim 1, wherein the passive metrology device includes a plurality of measurement transducers arranged in parallel to provide a corresponding respective plurality of measurements by which the position of the structure can be determined to the second degree of accuracy.

8. The manufacturing system of claim 7 , wherein the passive metrology device includes six such measurement transducers.

9. The manufacturing system of claim 1 , wherein the passive metrology device is a passive hexapod metrology device.

10. 10. The manufacturing system of claim 1, wherein the coordinate positioning machine is operable to perform at least one of the following types of operations: measuring operations, probing operations, machining operations, gripping operations, drilling operations, painting operations, pick and place operations, and gluing operations when the coordinate positioning machine is coupled to the passive metrology device.

11. 11. The manufacturing system of claim 1, wherein the coordinate positioning machine is couplable to at least one tool, the coordinate positioning machine also being coupled to the passive metrology device.

12. The manufacturing system of claim 11 , wherein the coupling comprises a bond that allows the coordinate positioning machine to be simultaneously coupled to the at least one tool and the passive metrology device.

13. The manufacturing system of claim 11 or 12, wherein the coordinate positioning machine is coupled to the at least one tool.

14. 14. The manufacturing system of claim 11, 12, or 13, wherein the at least one tool comprises at least one of a measurement probe, a gripping tool, a drilling tool, a welding tool, a bonding tool, and a painting tool.

15. The manufacturing system of claim 11 , wherein at least one tool is provided as an integral part of the passive metrology device.

16. 16. The manufacturing system of claim 1 , wherein the passive metrology device is not coupled to the coordinate positioning machine solely for calibration purposes before the coordinate positioning machine is operationally put into use.

17. The manufacturing system of claim 16 , wherein the passive metrology device effectively becomes part of the coordinate positioning machine during operational use of the coordinate positioning machine.

18. 18. The manufacturing system of claim 1, wherein the coupling is a physical and / or mechanical coupling.

19. 19. The manufacturing system of claim 1 , wherein the coupling between the coordinate positioning machine and the passive measurement device is a kinematic coupling.

20. A method for controlling a control system according to any one of claims 1 to 19, comprising the steps of: performing a first operation on the coordinate positioning machine decoupled from the passive measurement device; determining a position of the structure during the first operation using a positioning arrangement of the coordinate positioning machine; coupling the coordinate positioning machine to the passive measurement device using a drive of the coordinate positioning machine; performing a second operation on the coordinate positioning machine coupled to the passive measurement device; measuring the position of the structure during the second operation using the passive metrology device; decoupling the coordinate positioning machine from the passive measurement device.

21. 21. The method of claim 20, wherein when the coordinate positioning machine is coupled to the passive metrology device, a predetermined zone is defined within a working volume within which the passive metrology device can measure the position of the structure with the second accuracy, and the first operation is performed outside the zone and the second operation is performed inside the zone.

22. 22. The method of claim 21, wherein the first operation comprises moving the coordinate positioning machine from another such zone.

23. 23. The method of claim 20, 21 or 22, wherein the second operation includes at least one of a measuring operation, a probing operation, a machining operation, a drilling operation, and a bonding operation.

24. 24. A method according to any one of claims 20 to 23, comprising coupling the coordinate positioning machine to a tool required for the second operation prior to coupling the coordinate positioning machine to the passive metrology device.

25. 25. A manufacturing system according to any one of claims 1 to 19, comprising a machine controller operable to carry out the method according to any one of claims 20 to 24.

26. A computer program which, when executed by a controller of a manufacturing system according to any one of claims 1 to 19, causes the controller to carry out a method according to any one of claims 20 to 24.

27. A computer readable medium having stored thereon computer program instructions for controlling a manufacturing system according to any one of claims 1 to 19 to carry out a method according to any one of claims 20 to 24.

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