GB2576618A - Position measuring method and system for use on a floating installation - Google Patents

Position measuring method and system for use on a floating installation Download PDF

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Publication number
GB2576618A
GB2576618A GB1909575.1A GB201909575A GB2576618A GB 2576618 A GB2576618 A GB 2576618A GB 201909575 A GB201909575 A GB 201909575A GB 2576618 A GB2576618 A GB 2576618A
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GB
United Kingdom
Prior art keywords
arm
base
relative
inclination
pivotable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1909575.1A
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GB201909575D0 (en
Inventor
Mydland Petter
Abusdal Morten
Lien Geir
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Mhwirth AS
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Mhwirth AS
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Publication date
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Publication of GB201909575D0 publication Critical patent/GB201909575D0/en
Publication of GB2576618A publication Critical patent/GB2576618A/en
Withdrawn legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
    • E21B19/14—Racks, ramps, troughs or bins, for holding the lengths of rod singly or connected; Handling between storage place and borehole
    • E21B19/143—Racks, ramps, troughs or bins, for holding the lengths of rod singly or connected; Handling between storage place and borehole specially adapted for underwater drilling
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C9/00—Measuring inclination, e.g. by clinometers, by levels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B27/00—Arrangement of ship-based loading or unloading equipment for cargo or passengers
    • B63B27/36—Arrangement of ship-based loading or unloading equipment for floating cargo
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B35/4413—Floating drilling platforms, e.g. carrying water-oil separating devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/14—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude for indicating inclination or duration of roll
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C13/00—Other constructional features or details
    • B66C13/18—Control systems or devices
    • B66C13/46—Position indicators for suspended loads or for crane elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C15/00—Safety gear
    • B66C15/04—Safety gear for preventing collisions, e.g. between cranes or trolleys operating on the same track
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
    • B66C23/18—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes specially adapted for use in particular purposes
    • B66C23/36—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes specially adapted for use in particular purposes mounted on road or rail vehicles; Manually-movable jib-cranes for use in workshops; Floating cranes
    • B66C23/52—Floating cranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
    • B66C23/88—Safety gear
    • B66C23/90—Devices for indicating or limiting lifting moment
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
    • E21B19/002—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables specially adapted for underwater drilling
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B19/00—Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
    • E21B19/08—Apparatus for feeding the rods or cables; Apparatus for increasing or decreasing the pressure on the drilling tool; Apparatus for counterbalancing the weight of the rods
    • E21B19/087—Apparatus for feeding the rods or cables; Apparatus for increasing or decreasing the pressure on the drilling tool; Apparatus for counterbalancing the weight of the rods by means of a swinging arm
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/22—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring angles or tapers; for testing the alignment of axes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B17/00—Vessels parts, details, or accessories, not otherwise provided for
    • B63B2017/0072—Seaway compensators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B27/00—Arrangement of ship-based loading or unloading equipment for cargo or passengers
    • B63B27/10—Arrangement of ship-based loading or unloading equipment for cargo or passengers of cranes

Abstract

A floating drilling installation comprises a machine 20 with a base 24 and an arm 22 pivotable relative to the base 24 about a pivot axis. An inclinometer 28 mounted on the arm 22 determines the absolute angle of inclination of the arm relative to the earth. An inclinometer 30 mounted on the installation 11 determines the absolute inclination of the floating base. A processor connected to the inclinometers 28, 30 receives first and second inclination signals from the inclinometers 28, 30 and is programmed to determine the position of the pivotable arm relative to the base using both the inclination signals. Trigonometry is used to determine the relative position of the arm on the floating installation in knowledge of the relative absolute inclinations of the pivoting arm 22 relative to the floating installation 11. The arm may be a pipe handler apparatus 20 or a crane arm.

Description

Position Measuring Method and System for use on a Floating Installation
The present invention relates to a position measuring method and system for use on a floating installation such as a drilling rig for use in drilling an off-shore well bore.
It is known for machines on a floating installation such as an off-shore drilling rig to have a part which is pivotable relative to a base of the machine. Such a machine may, for example, be a pipe handler with a pivotable pipe handler arm. During operation of the machines on the drilling rig, it is desirable for an operator or operating system to be able to determine the position of the pivotable part relative to the machine base and/or other equipment on the rig. This may be necessary, for example, to prevent the pivotable part from colliding with another piece of equipment or part of the rig, or in the case of a pipe handler to determine if it is in the correct position relative to a pipe to activate a grabber to engage with and maybe pick up the pipe.
Typically this is achieved using measurements from a plurality of sensors including encoders, linear measurement sensors, proximity sensors, ultrasonic sensors, laser sensors, radar sensors, and LIDAR sensors, and/or visual motion detection using CCTV.
It is an object of the present invention to simplify, and therefore reduce the cost of, the equipment required to monitor the position of a pivotable part of a machine relative to the machine base.
According to a first aspect of the invention we provide a floating drilling installation comprising a machine having a base and a pivotal part which is mounted on and pivotable relative to the base about a pivot axis, and a position measuring apparatus for measuring the position of the pivotable part of the machine, the position measuring apparatus comprising a first inclinometer which is mounted on the pivotable part in order provide an inclination signal representing the absolute angle of inclination of the pivotable part, a second inclinometer which is mounted on the base in order to provide an inclination signal representing the absolute angle of inclination of the base, and a processor which is connected to the first and second inclinometers so as to receive first and second inclination signals from the first and second inclinometers respectively, and which is programmed to determine the position of the pivotable part of the machine relative to the base using both the first and second inclination signals.
The processor may be programmed to use information concerning the length of the pivotable part and the height of pivotable part relative to the base, and the first and second inclination signals to determine the location of an end of the pivotable part relative to the base.
The pivotable part may comprise an arm having a first end which is mounted on the base, there being a tool mounted at a second end of the arm.
The machine may be a pipe handling apparatus, and the tool comprise a gripper operable to engage with a tubular element so that the tubular element can be lifted by the arm.
The base may be mounted on or an integral part of the floating installation.
According to a second aspect of the invention, we provide a method of measuring the position of a pivotable part of a machine having a base, the pivotable part being mounted on and pivotable relative to the base about a pivot axis, using a position measuring apparatus comprising a first inclinometer which is mounted on the pivotable part and which provides an inclination signal representing the absolute angle of inclination of the pivotable part, a second inclinometer which is mounted on the base and which provides an inclination signal representing the absolute angle of inclination of the base, the method comprising
a) using both first and second inclination signals from the first and second inclinometers respectively to determine the position of the pivotable part of the machine relative to the base.
The method may include using information concerning the length of the pivotable part and the height of pivot part relative to the base, and the first and second inclination signals to determine the location of an end of the pivotable part relative to the base.
According to a third aspect of the invention we provide a data processing apparatus comprising means for carrying out the method according to the first aspect of the invention, the data processing apparatus being configured to process the first and second inclination signals to determine the position of the pivotable part of the machine relative to the base.
The data processing apparatus may be provided with information concerning the length of the pivotable part and the height of pivot part relative to the base, and be programmed to use this information and the first and second inclination signals to determine the location of an end of the pivotable part relative to the base.
According to a fourth aspect ofthe invention we provide a computer-readable medium comprising instructions which, when executed by a computer, causes the computer to carry out step a of the method according to the second aspect of the invention.
The instructions may, when executed by a computer cause the computer to use information concerning the length ofthe pivotable part and the height of pivot part relative to the base and the first and second inclination signals to determine the location of an end of the pivotable part relative to the base.
According to a fifth aspect of the invention we provide a position measuring apparatus for measuring the position of a pivotable part of a machine having a base, the pivotable part being mounted on and pivotable relative to the base, the apparatus comprising a first inclinometer which is adapted to be mounted on the pivotable part in order provide an inclination signal representing the absolute angle of inclination of the pivotable part, a second inclinometer which is adapted to be mounted on the base in order to provide an inclination signal representing the absolute angle of inclination of the base, and a processor which is connected to the first and second inclinometers so as to receive first and second inclination signals from the first and second inclinometers respectively, and which is programmed to determine the position ofthe pivotable part ofthe machine relative to the base using both the first and second inclination signals.
According to a sixth aspect ofthe invention we provide a position measuring system comprising a machine having a base and a pivotal part which is mounted on a pivotable relative to the base about a pivot axis, the system comprising a first inclinometer is mounted on the pivotable part in order provide an inclination signal representing the absolute angle of inclination ofthe pivotable part, a second inclinometer which is mounted on the base in order to provide an inclination signal representing the absolute angle of inclination of the base, and a processor which is connected to the first and second inclinometers so as to receive first and second inclination signals from the first and second inclinometers respectively, and which is programmed to determine the position of the pivotable part of the machine relative to the base using both the first and second inclination signals.
The processor may be programmed to determine the position of the pivotable part of the machine relative to the base using information concerning the height of the pivot axis relative to the base, and the length of the pivotable part, along with the first and second inclination signals to determine the position of an end of the pivotable part relative to the base.
The pivotable part may comprise an arm having a first end which is mounted on the base, there being a tool mounted at a second end of the arm.
The machine may be a pipe handling apparatus, the tool comprising a gripper operable to engage with a tubular element so that the tubular element can be lifted by the arm.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings of which,
FIGURE 1 shows a schematic illustration of a floating drilling installation according to the first aspect of the invention,
FIGURE 2 is a schematic illustration of a position measuring apparatus suitable for use in the floating drilling installation illustrated in Figure 1,
FIGURE 3 is a graph illustrating the position of the pivotable arm of the pipe handling apparatus shown in Figure 1 with the platform of the floating drilling installation in a horizontal position,
FIGURE 4 is a graph illustrating the position of the pivotable arm of the pipe handling apparatus shown in Figure 1 with the platform of the floating drilling installation tilted about the x axis,
FIGURE 5 is a graph illustrating the position of the pivotable arm of the pipe handling apparatus shown in Figure 1 with the platform of the floating drilling installation tilted about the x and y axes,
FIGURE 6 is a graph illustrating, in plan view, the position of the pivotable arm of the pipe handling apparatus shown in Figure 1 with the platform of the floating drilling installation tilted about the x and y axes, and the arm rotated about the z axis,
FIGURE 7 is a graph illustrating the position of an upwardly oriented pivotable arm mounted on a base which is tilted about the x and y axes, and
FIGURE 8 is a graph illustrating the position of an alternative configuration of pivotal part with three relatively pivotal links.
Referring now to Figure 1, there is shown a floating installation 10 according to the invention, which, in this embodiment comprises a floating drilling platform 11. Mounted on the drilling platform 11 is a rig 12 from which the drill string 14 is suspended, the drill string 14 extending down into a marine riser 16 which is suspended from the underside of the platform using a riser tensioner system 18. A pipe handler apparatus 20 is also provided on the platform 11, and is operable to a lift section of drill pipe 21 for its insertion into the drill string 14. The pipe handler apparatus 20 is provided with an arm 22 having a first end which is mounted on a base 24 of the apparatus, and a second end on which is mounted a gripper 26 which is operable to grab and hold onto a section of drill pipe 21, in order for the drill pipe 21 to be lifted into a desired position.
All these features are conventional on drilling platforms.
The floating installation 10 is also provided with a position measuring apparatus comprising a first inclinometer 28 which is mounted on the arm 22 of the pipe handler apparatus 20 and which provides an inclination signal representing the absolute angle of inclination of the arm 22 (i.e. the angle of inclination of the arm 22 relative to the earth), and a second inclinometer 30 which is mounted on the platform 11 and which provides an inclination signal representing the absolute angle of inclination of the platform 11 (i.e. the inclination of the platform 11 relative to the earth). The position measuring apparatus also comprises a processor 32 which is connected to both the first and second inclinometers 28, 30 so as to receive first and second inclination signals from the first and second inclinometers 28, 30 respectively, and which is programmed to determine the position of the arm 22 relative to the platform using both the first and second inclination signals. The processor 32 is connected to a visual display unit 34 which is configured to display the position of the end of the arm 22 for viewing by an operator. The position of the end of the arm 22 may thus be used by the operator of the control equipment by means of which the arm 22 is moved.
The processor 32 may also be connected to the control equipment so that the arm can be moved automatically to a desired position.
The position measuring apparatus is illustrated in Figure 2.
Inclinometers suitable for use in the position measuring apparatus are widely available, and examples of suitable inclinometers are the Q20L60 and QR24 inclinometers supplied by Hans Turck GmbH & Co. KG (Turck).
Referring now to Figure 3, there is shown a graph illustrating the position of the arm 22, which will be used to explain how the first and second inclination signals can be used to determine its position.
In this example, the position of the arm 22 is illustrated in relation to three orthogonal axes - the x and y axes forming a plane which is generally parallel to earth's surface, and a z axis which is perpendicular to the earth's surface. These axes are therefore fixed in space. At present, it is assumed that the plane formed by the x and y axes lie on a plane corresponding to the surface of the platform 11.
The arm 22 is pivotable about axis A, which is parallel to the x axis, and therefore moves in the plane formed by the y and z axes. In this example, the first end of the arm 22 is mounted on the base 24 so that it is elevated above the platform by a height h, and the arm 22 is pivoted so that its second end, and therefore the gripper 26, is lower than its first end, in order to pick up a section of drill pipe 21 on the platform 11.
The arm 22 has a length I, and the first inclinometer 28 is arranged to measure the angle of the arm 22 relative to axis B which is a horizontal axis parallel to the y axis, and to the longitudinal axis of the arm 22. This measured angle is designated 0meas. From basic trigonometry, it will be appreciated that the y and z coordinates (ymeas and zmeas) of the second end of the arm 22 (marked as pmeas) relative to the platform 11, can be determined using the measured angle and the known length of the arm 22 using the following equations:
ymeas = i cos omeas
Zmeas = h -1 sin emeas
The desired position of the second end of the arm 22, i.e. the position of the arm 22 which puts the gripper 26 in the right position to be operable to grab the drill pipe 21, is marked as point P in Figure 3, and represented by the y and z coordinates of Y and Z. Again, using basic trigonometry it will be appreciated that angle of inclination of the arm 22 when the gripper 26 is in the desired position (designated Θ) can be determined using these coordinates and the following equations:
θ = cos 1 (Y/l)
However, as mentioned above, the inclinometers 28, 30 measure an absolute angle of inclination, i.e. the angle of inclination relative to the earth. As such this method will only work if both the base 24 of the pipe handler apparatus 20 and the drill pipe 21 are stationary, and the platform 11 remains parallel to the surface of the earth. It will be appreciated, however, that, as both are located on a floating installation 10, this is unlikely to be the case. The floating installation will move with the heave of the ocean, and/or as a result of changes in weight or weight distribution on the platform 11. If this movement were purely vertical or horizontal translational movement, the above method would be applicable, but it will be appreciated that it is also unlikely. It is far more probable that the floating installation will tilt during the operation of the pipe handler apparatus 20.
The effect of this tilting of the platform 11 on the above method will be described with reference to Figure 4. For the sake of simplicity, it is assumed, in the first instance, that the platform 11 tilts by an angle of -τ (negative because it represents rotation in an anticlockwise direction) about an axis which is parallel to the x axis. The surface of the platform 11 now lies in a plane formed by the x axis and a new y' axis illustrated in Figure 4, and is perpendicular to new z axis z'. The second inclinometer 30 is configured to determine the angle of the platform 11 relative earth, of course, and is arranged to measure the angle ofthe y' axis relative to the horizontal, so the inclination signal from the second inclinometer represents the angle -τ.
This tilting of the platform 11 will result in upwards movement of the drill pipe 21 in space, and therefore upwards movement of the desired position of the second end of the arm 22 to a new position relative to the platform 11 marked as pmeas' in Figure 4.
Although the arm 22 and therefore the first inclinometer 28 has also tilted through the same angle, as the inclinometers provide a signal which represents the absolute angle of inclination, the inclination signal from the first inclinometers 28 still represents the angle of inclination ofthe arm 22 relative to the B axis. In order to calculate the position ofthe arm 22 relative to the platform 11, it is necessary to use the signals from both inclinometers 28, 30 as follows:
Ymeas = I cos (0meas - (- τ)) = I cos (0meas + τ)
Zmeas = h -1 sin (0meas - (- τ)) = h -1 sin (0meas + τ)
It will be appreciated that if arm 22 is moved so that its angle of inclination is θ as calculated above, the gripper 26 will no longer be in the right place to grab the drill pipe 21. In fact, if the platform 11 tilts far enough, and the desired position is relative close to the surface of the platform 11, pivoting the arm 22 to an angle θ could cause the end of the arm 22 to crash into the surface ofthe platform 11.
To move the arm 22 so that the gripper 26 is in the desired position relative to the platform 11 (i.e. at position represented by the y' and z' coordinates Y and Z), the arm 22 must now be moved so that its angle of inclination relative to the B axis is θ - τ, or cos_1(Y/I) - τ.
It is, of course, unlikely that the floating installation 10 will only tilt about an axis which is exactly parallel to the axis of rotation of the arm 22. It is likely that the floating installation will tilt such that angle of the surface of the platform 11 changes relative to both the x and y axes. When this happens, the arm 22 will be rotated in space about its longitudinal axis, and when pivoted about axis A will pivot in a plane which is at an angle to the vertical. As such, the plane including the arm 22 and the y and z axes . and will no longer lie in a plane parallel to axis B. The surface ofthe platform 11 now lies in a plane formed by a new x axis and a new y axis illustrated in Figure 5, and is perpendicular to new axis z. The x, y and z axes are in the same position relative to the platform 11 as the original x, y and z axis, but are in different positions in space. The arm 22 now pivots about an A” axis which is parallel to the x axis, to move in a plane formed by the x and y axes, but this plane is no longer vertical.
Of course, the first inclinometer 28 measures the angle of the arm 22 relative to a horizontal axis which lies in a vertical plane in which the arm 22 extends. As such, the angle measured by the first inclinometer 28 will be slightly smaller than the angle of the arm 22 relative to the y axis. The same applies to the second inclinometer 30 too. The reading from this inclinometer 30 will not represent exactly τ the angle of the y axis to the horizontal in the plane formed by the y and z axes- it will also give an angle which is slightly smaller.
Having said that, in practical terms, the overall angle of tilt of the platform 11 is relatively small, and the differences in angle described above will be smaller still. The inaccuracy in terms of the y coordinate of the end of the arm 22 introduced by this discrepancy is related to the cosine of the angle, which for small angles is approximately equal to 1. As such, it is possible to ignore this discrepancy, and to use the inclination signals from the first and second inclinometers 28, 30 to represent 0meas and τ in the equations above, in order to determine the position of the end of the arm 22 even when the platform 11 tilts relative to both the x and y axes.
It will also be appreciated that the arm 22 could also be configured to pivot about an axis of rotation which is perpendicular to the plane of the platform 11, in order to pick sections of drill pipes 21 from different points on the platform 11.
In one embodiment, this is achieved by configuring the base 24 to be pivotable relative to the platform 11 about an axis which is perpendicular to the plane of the platform 11. In this case, the second inclinometer 30 is advantageously, mounted on the base 24, so that it rotates with the base, and always measures the angle of inclination of the platform in the same direction relative to the arm 22. In other words, irrespective of the rotation of the arm 22, the axis of the second inclinometer 30 and the arm 22 always lie in a single plane - a plane formed by an axis y' which lies in the plane of the platform 11 and the axis B of the first inclinometer 28.
In this case, the height of the end of the arm 22 above the surface of the platform 11 (i.e. Zmeas) can be determined as before, using the equation:
Zmeas = h -1 sin (0meas - (- τ)) = h -1 sin (0meas + τ)
However, if the full position of the end of the arm 22 relative to the platform 11 is to required, it is necessary for the position measuring apparatus to further include an orientation sensor which is connected to the processor 32 and which is configured to provide the processor 32 with a signal representing the angle λ through which the base 24 has rotated, relative to a reference plane which extends perpendicular to the plane of the platform 11 and in which the axis of rotation of the base 24 lies.
The processor 32 use the inputs from the inclinometers 28, 30 to determine 0meas, the angle between the arm 22 and the horizontal axis B, and angle τ, the angle of the axis y' to the horizontal, and the angle λ to determine the position of the y' axis relative to the platform 11.
For example, if the reference plane extends along the axis y on the plane of the platform
11, and the arm 22 has been rotated clockwise about the z axis through an angle λ, as illustrated in the plan view of the platform 11 shown in Figure 6, the position of the end of the arm 22 relative to the x, y and z axes on the platform 11 can be calculated as follows:
Xmeas = sin λ . I cos (0meas + c) ymeas = cos λ . | cos (Qmeas + τ)
Zmeas = h -1 sin (gmeas + τ)
Alternatively, if the second inclinometer 30 is mounted on the platform 11, and therefore does not rotate with the base 24, or if the arm 22 rotates about an axis which is perpendicular to the plane of the platform 11, it is necessary for the second inclinometer 30 to be biaxial, i.e. to measure inclination relative to two orthogonal axis, the orientation of which relative to the reference plane, is known. The processor 32 is, in this case, programmed to use the signals from the second inclinometer 30, and the signal from the orientation sensor, to determine the angle of tilt of the y' axis relative to the horizontal, in orderto determine the value ofc.
The same principles can be applied to determining the position of an arm 22, such as a crane arm, which extends upwardly so that its second end is higher than its pivot axis A”, as illustrated in Figure 7. Again, in this case, the platform has tilted through an angle of-τ (i.e. τ anticlockwise) relative to the y axis, and the arm 22 rotated through an angle of λ (clockwise) about the z axis, but this time, the arm 22 is inclined at an angle of-0meas (anticlockwise) relative to the horizontal.
In this case, the position of the second end of the arm 22 can be determined using the following equations:
Xmeas = sin λ . I cos (0meas-r) ymeas = cos λ . | cos (Qmeas _ τ) zmeas = h + I sin (emeas - t)
The invention is not restricted to use with a pipe handling apparatus or crane, it could be used to determine the position of any pivotable part, relative to the platform 11, for example to determine if the pivotable part is likely to collide with another fixed or movable part of, or mounted on, the platform.
It will also be appreciated that the length of the arm 22 may be variable, for example if the arm 22 is telescopic. In this case, the system would further comprise means to enable the processor to determine the length of the arm 22, so that the arm length 22 can be matched with the corresponding angle of inclination at any one time, and used as the value I in the above calculations. For example, where a hydraulic or pneumatic cylinder is used to extend the arm the system may further comprise a position sensor which is connected to the processor 32 and provides an input signal representing the degree of extension of the cylinder. This can be added to the unextended length of the arm 22 to obtain the extended length I.
The pivotal connection of the arm 22 to the base 24 may also be movable perpendicular to the platform 11. For example, the pipe handling apparatus or crane may be provided with a winch and wire system which can be used to raise or lower the arm 22 relative to the base
24. In this case, the system would further comprise means to enable the processor to determine the height of the pivot axis of the arm 22, so that the pivot axis height can be matched with the corresponding angle of inclination at any one time, and used as the value h in the above calculations.
It will be appreciated that in the examples above, the position of the end of the arm 22 is determined in relation to x and y axes having their origin set by the position of the base 24 of the pipe handler apparatus 20. It is conventional, however, to define locations of the platform 11 of a drilling installation 10 with reference to a point of origin at the well centre. In order to determine the location of the end of the arm 22 relative to the well centre, it would be necessary to combine the x and y coordinates of the origin defined by the base 24 of the pipe handler apparatus 20 relative to the well centre, with the xmeas and Ymeas coordinates determined as described above using the first and second inclination signals.
A floating installation may be provided with more than one machine with a pivotable arm, and in order to determine the positions of the end of the pivotable arm of each such machine, it would be necessary to provide a first inclinometer on each pivotable arm. It may not be necessary to provide a second inclinometer for each machine. For example, if all the pivotable arms pivot in mutually parallel planes, it will be possible to use inclination signal from the same platform 11 or base 24 mounted inclinometer 30 to determine the angle τ for all of the arms 22. If, however, the arms 22 pivot in planes which are not mutually parallel, it will be necessary either to provide a second inclinometer 30 for each machine, each second inclinometer 30 being arranged to measure the inclination of the platform relative to the horizontal in the direction of its associated arm 22, or to provide a single second inclinometer 30 for all the machines which is a biaxial inclinometer, and the processor configured to use the signals from the biaxial second inclinometer 30 to determine a different angle τ for each machine, depending on the orientation of the arm 22 of that machine relative to the two axes of the second inclinometer 30.
In the embodiments described above, a machine which a simple single boom arm 22 is shown. It will be appreciated, however, that the invention could equally be applied to a machine with a more complex arm, for example one in which the arm has multiple pivotally connected links. In this case, if the angle between adjacent links can be varied, in addition to pivoting the arm 22 about the pivotal connection with the base 24, it would be necessary to provide means for measuring the angle of each pivotal link, and use this information, and the length of each link, in standard geometrical calculations to determine the position of end ofthe arm 22. For example, an inclinometer may be provided on each such linkage, and the signal from each of these inclinometers and the second inclinometer 30 used to determine the position of the end of the arm 22.
An example of such an arrangement is illustrated in Figure 8. In this embodiment, the arm 22 is provided with three links 22a, 22b and 22c, arranged end to end. Each link 22a, 22b, 22c is pivotally connected to the adjacent link or links, and an inclinometer is mounted on each link to measure the angle of the link relative to the horizontal. Where the links have length la, lb, lc respectively, and the platform 11 has tilted through an angle of-τ (so anticlockwise), and the inclinometers on each link 22a, 22b, 22c measure an angle of 0measl, 0meas2, and 0meas3 respectively, the position ofthe end ofthe arm 22 can be calculated using the following equations:
Xmeas = sin λ . (la. cos (0measl + τ) + lb . cos (0meas2 + τ) + lc. cos (0meas3 + τ)) ymeas = cos λ (|a cos (Qmeasl + τ) + |b . COS (0meas2 + τ) + lc . COS (0meas3 + τ))
Zmeas = h - la. sin (0measl + τ) - lb. sin (0measl + τ) - lc. sin (0meas3 + τ).

Claims (4)

1. A floating drilling installation comprising a machine having a base and a pivotal part which is mounted on and pivotable relative to the base about a pivot axis, and a position measuring apparatus for measuring the position of the pivotable part of the machine, the position measuring apparatus comprising a first inclinometer which is mounted on the pivotable part in order provide an inclination signal representing the absolute angle of inclination of the pivotable part, a second inclinometer which is mounted on the base in order to provide an inclination signal representing the absolute angle of inclination of the base, and a processor which is connected to the first and second inclinometers so as to receive first and second inclination signals from the first and second inclinometers respectively, and which is programmed to determine the position of the pivotable part of the machine relative to the base using both the first and second inclination signals.
2. The floating drilling installation according to claim 1 wherein the processor is programmed to use information concerning the length of the pivotable part and the height of pivotable part relative to the base, and the first and second inclination signals to determine the location of an end of the pivotable part relative to the base.
3. The floating drilling installation according to claim 1 or 2 wherein the pivotable part comprises an arm having a first end which is mounted on the base, there being a tool mounted at a second end of the arm.
4. The floating drilling installation according to claim 3 wherein the machine is a pipe handling apparatus, and the tool comprises a gripper operable to engage with a tubular element so that the tubular element can be lifted by the arm.
GB1909575.1A 2018-07-05 2019-07-03 Position measuring method and system for use on a floating installation Withdrawn GB2576618A (en)

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