US3912227A - Motion compensation and/or weight control system - Google Patents

Motion compensation and/or weight control system Download PDF

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Publication number
US3912227A
US3912227A US407051A US40705173A US3912227A US 3912227 A US3912227 A US 3912227A US 407051 A US407051 A US 407051A US 40705173 A US40705173 A US 40705173A US 3912227 A US3912227 A US 3912227A
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United States
Prior art keywords
cylinder
load
piston
primary
fluid
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US407051A
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English (en)
Inventor
Joseph Fitzpatrick Meeker
Michael Donahoo Keen
Larry E Lee
Roderick Charles Lejeune
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Drilling Systems International Inc
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Drilling Systems International Inc
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Priority to US407051A priority Critical patent/US3912227A/en
Priority to GB5238675A priority patent/GB1476672A/en
Priority to GB5239775A priority patent/GB1476673A/en
Priority to GB3762874A priority patent/GB1476671A/en
Priority to AU73102/74A priority patent/AU7310274A/en
Priority to JP49116802A priority patent/JPS5067201A/ja
Priority to DE19742448813 priority patent/DE2448813A1/de
Priority to NL7413626A priority patent/NL7413626A/xx
Priority to FR7434842A priority patent/FR2248225A1/fr
Application granted granted Critical
Publication of US3912227A publication Critical patent/US3912227A/en
Priority to NO800210A priority patent/NO800210L/no
Priority to NO800211A priority patent/NO800211L/no
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/08—Servomotor systems incorporating electrically operated control means
    • F15B21/087—Control strategy, e.g. with block diagram
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK 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
    • E21B19/09—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 specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S254/00—Implements or apparatus for applying pushing or pulling force
    • Y10S254/90—Cable pulling drum having wave motion responsive actuator for operating drive or rotation retarding means

Definitions

  • This invention relates to a motion compensation and- /or weight control system for an assembly that supports a load.
  • This invention has particular application to a load-supporting assembly, such as an earth-boring assembly, mounted on a floating structure.
  • U.S. Pat. No. 3,259,37l to Goepfert et al discloses a motion compensation system for use with a loadsupporting assembly mounted on a floating structure which is a combination passive and active system.
  • the Goepfert motion compensation system includes a linear positioning device or expansible and contractible mechanism which has coupled to one end thereof a source of constant pressure fluid and which has coupled to the other end thereof a hydraulic control valve connected to a pump and to a source of hydraulic fluid.
  • the control valve is operated by electrical signals generated by a controller responsive to the linear position of the floating structure relative to the earth and the linear position of the linear positioning device relative to its activator rod.
  • Prior art motion compensation and/or weight control systems usually have operated either in a pressure mode, that is, responsive to changes in the pressure of the fluid in the expansible and contractible mechanism, or in a position mode, that is, responsive to the expansion and contraction of the expansible and contractible mechanism and the movement of the floating structure relative to the earth.
  • a pressure mode that is, responsive to changes in the pressure of the fluid in the expansible and contractible mechanism
  • a position mode that is, responsive to the expansion and contraction of the expansible and contractible mechanism and the movement of the floating structure relative to the earth.
  • there are certain advantages attendant to operating either in the pressure mode or the position mode there are certain advantages attendant to operating either in the pressure mode or the position mode.'Most of the prior art motion compensation and- /or weight control systems cannot be readily switched between the pressure mode and the position mode.
  • those' prior art motion compensation and/or weight control systems which are capable of operating in the position mode function responsive to input data indicative'orily of the magnitude and direction of the expansion and contraction of the expansible and con tractible mechanism and of the movement of the floatingstructure relative to the earth.
  • the improved motion compensation and/or weight control system according to this invention is a combination passive and active system which overcomes the disadvantages of the purely passive systems and the purely active systems, and is an improvement over the combination passive and active system disclosed in Goepfert et al U.S. Pat. No. 3,259,371.
  • the improved motion compensation and/or weight control system may be generally described as a system mounted on a loadsupporting assembly for supporting a load which is movable relative to the load-supporting assembly.
  • the system includes an improved expansible and contractible mechanism which preferably depends from a traveling block, drill head or the like mounted in a derrick, tower or the like.
  • the load to be supported then depends from the improved expansible and contractible mechanism.
  • the improved expansible and contractible mechanism according to this invention includes at least one primary piston and cylinder assembly, preferably passively operated, providing forces at least sufflcient to support the load.
  • the improved expansible and contractible mechanism also includes at least one secondary piston and cylinder assembly, preferably actively operated, providing forces opposing the forces of the primary piston and cylinder assembly.
  • the motion compensation and/or weight control system can be operated in either the pressure mode or the position mode.
  • hydraulic fluid is actively supplied to and withdrawn from the secondary piston and cylinder assembly responsive not only to the magnitude and direction of the expansion and contraction of the expansible and contractible mechanism and of the movement of the floating structure relative to the earth, but also to the velocity of such expansion and contraction and such movement.
  • FIG. 1 is a diagramatic view of an embodiment of a I motion compensation and/or weight controlsystem according to this invention in association with an earthboring assembly mounted .on' a floating structure for drilling a well hole beneath a body-of water.
  • FIG. 2 is a front elevational view, with certain parts shown in longitudinal section of the expansible and contractible mechanism of the system disclosed in FIG. 1 in a partially telescoped position, and with the components of the system for passively supplying hydraulicv
  • FIG. 3 is a graph depicting with respect to time thetypical vertical movement of a floating drilling rig and the typical vertical movement of the piston rod of the expansible and contractible mechanism relative to its outer'cylinder.
  • FIG. 4 is a schematic and block diagram of a preferred arrangement of the electrical components-of the control means in the active portion of the system.
  • FIG. '5 is a front elevational view,'with certain parts shown in longitudinal section, of an alternate component for actively supplying hydraulic fluid to the'expansible and contractible mechanism disclosed in FIG. 2.
  • FIG. 6 is a'front elevational view, with certain parts shown in longitudinal section, of an alternate expansible and contractible mechanism according to this invention.
  • FIG. 7 is a diagrammatic view of an alternate embodiment of the motion compensation and/or weight control system according to this inventionin association with an earth-boring apparatus having a hydraulically supported drill head and mounted on a floating structure.
  • FIG. 8 is a front elevational view, with certain parts shown in longitudinal section, of still another embodimentof an expansible and contractible mechanism according to this invention.
  • FIG. 9 is a front elevational view, with certain parts shown in longitudinal section, of still another embodiment of an expansible and contractible mechanism according to this invention.
  • FIG. 10 is a front elevation view, with certain parts shown in longitudinal section, of still another embodiment of an expansible and contractible mechanism ac- DESCRIPTION OF PREFERRED EMBODIMENTS OF INVENTION
  • the earth-boring assembly is illustrated drilling a vertical well hole 11 into a sub-aqueous seabed l2.
  • the floating structure 13 is suitably anchored (not shown) against excessive lateral displacement for the purpose of holding the drill string 14 in centered relation with respect to the well hole.
  • a drill bit15 is secured to the lower end of the drill string 14 and is in contact with the earth.
  • a marine riser 16 extends from the wellhead 17 at the sea floor upwardly to a location adjacent the floating structure 13.
  • the upper portion of the drill string 14 is secured to a kelly 18 passing through a rotary table 19.
  • the upper end of the kelly is secured to a swivel 20 which is in turn suspended from a hook 21 connected to the lower portion of the expansible and contractible mechanism 22 of the improved motion compensating and/or weight control system according to this invention.
  • a mud line 23 is connected to the swivel.
  • the earth-boring assembly illustrated in FIG. 1 employs a derrick 24 having a crown block 25 secured at the top thereof.
  • a derrick 24 having a crown block 25 secured at the top thereof.
  • Cable 26 is dead-ended to the floating structure 13 at a selected point 28, extended upwardly and suitably reeved about crown block 25 and traveling block 27, then extended downwardly to the drawworks 29.
  • the drawworks 29 winds-in or winds-out the cable 26 to raise and lower the traveling block 27.
  • a weight indicator30 preferably is coupled into the cable 26 at a selected location, such as adjacent the dead-end thereof. 5
  • the motion compensation and/or weight control system utilizes an expansible and contractible mechanism 22 to provide a desired telescoping action whereby selected movement of the load relative to the floating structure can be effected or, if the load is incontact with the earth, a certain pressure can be maintained between the load and the earth.
  • the expansible and contractible mechanism 22 of the motion compensating and/or weight control system according to this invention is shown in FIG. 1 secured or interposed between traveling block 27 and hook 21.
  • the weight of the load hooked to or supported by the expansible and contractible mechanism 22 is referred to as the hook load.
  • the required amount of expansion and contraction of the mechanism 22 is reduced. For example, assuming that the crown block and traveling block provided a ten to one reduction in the movement of the cable 26, an expansible and contractible mechanism mounted between the floating structure 13 and the dead-end of the cable 26 would have to expand and contract a distance of forty feet to move the load four feet. Additionally, an expansible block or on the floating structure must contend-with the friction forces generated by the reversal of the I crown block and the traveling block as ,the cable is reeved in and out during the compensation cy,cle.
  • an oil/air interface tank 35 Mounted on the floating structure 13 is an oil/air interface tank 35, a bank 36 of air accumulator tanks, and a means 37 for actively supplying hydraulic fluid.
  • the oil/air interface tank 35 and the bank 36 of air accumulator tanks function to passively introduce and withdraw hydraulic fluid to and from the expansible and contractible mechanism 22 and means 37 functions to actively introduce and withdraw hydraulic fluid to and from the expansible and contractible mechanism 22.
  • a rotatable drum 38 which, as will be hereinafter explained, is employed in determining the vertical position of the floating structure with respect to the seabed.
  • a preferredembodiment of the expansible and contractible mechanism 22 comprises two identical piston and cylinder assemblies 39 and 39.
  • Each of the piston and cylinder assemblies 39 and 39 is secured to a support member 40 which inturn is secured to the traveling block 27.
  • Movable longitudinally within each of the cylinders 39 and 39 is a piston rod 41 and 41, respectively.
  • Piston rods 41 and 41 are secured to a second support member 42, from which depends the hook 21.
  • each of the two piston and cylinder assemblies of the expansible and contractible mechanism 22 extends upwardly along the side of'the traveling block. For a selected size of expansible'and contractible mechanism, this reduces the height beneath the derrick of the total mechanism.
  • the expansible and contractible mechanism of the improved motion compensation and- 1 can comprise more than two cylinder and piston assemblies surrounding a traveling block, one cylinder and piston assembly depending from the'traveling block (as hereinafter described), or other configurations (some of which are hereinafter described).
  • Each of the piston and cylinder assemblies 39 and 39 (only piston and cylinder assembly 39 will be described fully hereinafter) in this embodiment of this invention comprises an outer, primary cylinder 43 having end plates 44 and 45. Attached to the upper end plate 44 of outer cylinder 43 and depending therefrom is an inner cylinder 46 disposed concentrically within the outer cylinder 43. Inner cylinder 46 preferably extends the full length of outer cylinder 43'and protrudes a slight distance beyond the lower end plate 45 of outer cylinder 43.
  • the piston rod 41 previously referred to' is cylindrical and hollow, and is slidably disposed around the inner cylinder 46.
  • a first piston'47 is secured to the 7 upper end of the piston rod 41 within the annular' chamber formed between the inner cylinder 46 andthe ,low erlend of thepiston rod comprises a second piston "50 v
  • the annular chamber formed between the lower end plate 45, outer cylinder 43, piston rod 41, and first piston 47 comprises a primary chamber 51, sometimes referred to as the passive chamber.
  • the chamber formed within the upper end plate 44, inner cylinder 46, hollow piston rod 41, and the second piston 50 comprises a secondary chamber 52, sometimes referred to as the active chamber.
  • the annular chamber formed between the upper end plate 44, first piston 47, and inner cylinder 46 comprises a deceleration chamber 53.
  • a port 54 is provided in the lower part of outer cylinder 43 in fluid communication with passive chamber 51.
  • a conduit 55 provides fluid communication from the port 54 to the oil/airinterface tank 35.
  • the oil/air interface tank 35 is in fluid communication through conduit 56 with the bank 36 of air accumulator tanks.
  • the'bank of air accumulator tanks and the oil/air interface tank provide the standard pneumatic/hydraulic system for passively supplying and receiving pressurized hydraulic fluid to and from the primary chamber 51.
  • a pressure transducer 57 In fluid communication with the hydraulic fluid in primary chamber 51 is a pressure transducer 57 which d'etermines the pressure of the hydraulic fluid and generates an electrical signal proportional thereto.
  • A'port 58 is provided through the upper end plates and into each of the secondary or active chambers 52 and 52.
  • a conduit 59 places active chambers 52 and 52- in fluid communication with'a means 37-for introducingand withdrawing hydraulic fluid intoand from active chambers 52 and 52.
  • a pressure transducer 60 such as a Tyco instruments Model AF-f3000, is in communication with the active'hydraulic' fluid being supplied to active chambers 52 and 52'.- Such pressure transducer determines the pressure of the fluid in the active chambers and generates a signal proportional thereto.
  • Conduit 59 is influid communication with a pump 61.
  • Pump 61 is in fluid communication through conduit 62 with a sump 63 in which hydraulic fluid is maintained.
  • Pump 61 may be any of various commercially available devices, but preferably is a variable volume, bidirectional, over-center pump such as manufactured by Von Roll, Ltd. of Switzerland, Rex Roth, Sunstrand, or Dynapower. In the preferred pump, the direction in which hydraulic fluid is pumped and the volume ofhydraulic fluid so pumped is controlled by the position of the yoke of the pump.
  • the position of the yoke ofithe pump is controlled by a servo value 64 such as is well known to those skilled in the art.
  • the operation of the servo value is controlled by electrical signals supplied thereto from control means 65.
  • Control means 65 operates, as will hereafter be explained, responsive to a feedback signal from servo valve 64 and input signals supplied to the control means 65 which vary depending uponwhether the system is operated in the tied-toground mode or the pressure mode.
  • annular chamber 53 between the upper end plate 44 of the outer cylinder 43, the inner cylinder 46, and the first piston 47.
  • This annular chamber 53 is a deceleration chamber. It preferably contains a selected amount of hydraulic fluid.
  • the upper end plate 44 of outer cylinder 43 preferably has inclined shoulders 66 providing a tapered, truncated surface leading to one or more orifices 67 which communicate with an exterior chamber 68.
  • FIG. 3 illustrates graphically with respect to time the typical vertical movement of the floating structure 13 relative to the wellhead 17.
  • the vertical movement of the floating structure responsive to normal wave motion produces a graph 71 which is sinusoidal.
  • the floating structure 13 is farthest from the wellhead 17 at point in time 72 when it is on the crest of the wave and,
  • the piston rods 41 and 41 should move relative to the outer cylinders 43 and 43 in the direction opposite to the floating structure at a distance and at a velocity equal to the movement of the floating structure, as illustrated by the dashed sinusoidal line 74.
  • the movement of the piston rods relative to the, outer cylinders will not necessarily track" the movement of the floating structure.
  • the various sensors utilized to produce input data for the control means 65 will vary depending upon the mode in which the system is operated.
  • the pressure transducers 57 and 60 previously described constitute one set of sensors for generating input signals.
  • the other set of sensors comprises means for determining the position of the piston rods 41 and 41' relative to the outer cylinders 43 and 43',
  • illusa Lockheed Electronics position transducer preferably comprises a spring-loaded rotary element 76 secured to thefirst support member and a line or cable 77 secured to the second support member 42. Linear movement of the second support member 42 relative to the first support member 40 causes the cable 77 to wind onto and unwind from the rotary element 76, thereby rotating the rotary element.
  • the position transducer generates an electrical signal proportional to the direction and magnitude of the rotation of the rotary element, which electrical signal is coupled via a conductor (not shown) to the control means 65.
  • the means for determining the direction and the velocity of the movement of the piston rods relative to the outer cylinders preferablycomprises a velocity transducer 78, such as a Servotek DC Tachometer or other commercially available device, also secured between the first and second support members.
  • a velocity transducer 78 comprises a spring-loaded rotary'member secured to the first support member and a line or cable secured to the second support member. Linear movement of the two support members relative to eachother causes the cable to wind onto and'unwind from the rotaryelement.
  • the velocity transducer 78 generates an electrical signal proportional to the direction and velocity of the rotation of the rotary element, which electrical signal is coupled to the control'means 65 via conductor (not shown).
  • the means for determining the linear position of the floating structure relative to the wellhead preferably comprises, as illustrated in FIG. 1, a' cable 79 secured to the marine riser 20, which in turn is secured to the wellhead on the sea floor. Alternately, the cable 79 could be connected to the guidelines or directly to the wellhead. The cable 79 is reeved around the rotat able drum 38.
  • Drum 38 maintains a constant tension on the cable 79 and windsor unwinds the cable responsive or one of the numerous shaft encoders manufactured by Astrosystems, Inc. and well known in the art, is attached to drum 38.
  • the position transducer produces an electrical signal proportional to the direction and magnitude of the rotation of such drum 38, which signal is coupled to the control means 65 via conductor (not shown).
  • the means for determining the direction and the velocity of the movement of the floating structure relative to the wellhead preferably comprises a rotatable velocity transducer 81, such as is well known to those skilled in the art, attached to drum 38.
  • the velocity transducer 81 produces an electrical signal proportional to the direction and velocity of rotation of the drum 38, which signal is coupled to the control means 65 via conductor (not shown). 1
  • An optional sensor'means comprises another position indicating device (not shown) associated with the draw works 29 or with the crown block 25 for indicating the amount of cable 26 wound-in or wound-out by the draw works 29.
  • Such position indicating device generates an electrical signal proportional to the length of the cable 26 wound-in or wound-out from the draw works, which signal may be utilized to determine the position of the traveling block 27 relative to the floating structure 13.
  • a typical position transducer would be the Beckman potentiometer, Bourns potentiometer, or Lockheed Electronics position transducers.
  • control means 65 functions responsiveto the electrical signals generated by position transducer 75, velocity transducer 78, position transducer 80, and velocity transducer 81, to cause servo valve 64 to operate pump 61 such that hydraulic fluid is supplied to and withdrawn from the active chambers 52 and 52.
  • control means 65 will cause the servovalve to operate pump 61 such that at point in time 82 no additional hydraulic fluid is either withdrawn from or supplied to the active chambers 52 and 52'. Thereafter, as the floating structure 13 moves further downward, such as at point in time 83, additional hydraulic fluid must be withdrawn from the active chambers 52 and 52' to compensate for the additional error in the passive portion of the system.
  • Q is the volume of the hydraulic fluid supplied to or withdrawn from the active chambers
  • k is a constant
  • Vs is the direction and velocity of the movement of the floating structure
  • k is a constant
  • Ve is the difference between the direction and velocity of the movement of the floating structure and the direction and velocity of the movement of the piston rods 41 and 41' (herein sometimes referred to as velocity error)
  • k is a constant
  • Le is the difference in the position of the floating structure relative to the wellhead and the position of the piston rods relative to the outer cylinders (herein sometimes referred to as position error).
  • FIG. 4 illustrates partially in schematic and partially in block diagram a preferred arrangement of the electrical components comprising the control means 65.
  • Position transducer 80 generates an electrical signal proportional to the linear position of the floating structure relative to the wellhead. This electrical signal is added to an electrical signal generated by potentiometer 85, which is adjusted to a magnitude proportional to the tide.
  • This combined electrical signal is coupled to the input of an operational amplifier 86, such as a type 741.
  • an electrical signal generated by position transducer which is proportional to the linear position of the piston rods 41 and 41' relative to the outer cylinders 43 and 43'. Amplifier 86 functions to compare the two electrical signals supplied to its input and generate an electrical signal proportional to the difference therebetween. This electrical signal generated by amplifier 86 is proportional to the position error.
  • Velocity transducer 78 generates an electrical signal proportional to the direction and velocity of the movement of the piston rods relative to the outer cylinders.
  • Velocity transducer 81 generates an electrical signal proportional to the direction and velocity of the movement of the floating structure relative to the wellhead. These two electrical signals are coupled to an operational amplifier 87 which functions to compare them and generate an electrical signal proportional thereto. The electrical signal generated by amplifier 87 is proportional to the velocity error.
  • the position error signal generated by amplifier 86 and the velocity error signal generated by amplifier 87 are coupled to an operational amplifier 88 which functions to compare them and generate an electrical signal proportional to theirsum.
  • the electrical signal generated by amplifier 88 and the velocity signal generated byv transducer 81 are coupled to operational amplifier 89 which functions to compare the two signals and generate an electrical signal proportional ,to their sum.
  • the electrical signal generated by amplifier 89 is proportional to the volume of hydraulic fluid which should be supplied to or withdrawn-from the active chambers 52 and 52 to obtain substantially error-free motion compensation when the system is operated in the position mode.
  • the electrical signal generated by amplifier 89 is coupled through switch 90 to the input of a conversion means 91. Also coupled to the input of conversion means 91 is an electrical signal generated by tachometer 92 which is proportional to the speed of the motor (not shown) driving pump 61.
  • the conversion means 91 any of numerous devices well known to those skilled in the art, functions to convert the input electrical signal which is proportional to the volume of hydraulic fluid to be supplied to or withdrawn from the active chambers, into an electrical signal which is inversely-proportional to the speed of the pump 61.'The output of conversion means 91 is coupled to the input of non-linear compensation means 93 which functions to alter the electrical signal to compensate for any nonlinearity in the system.
  • non-linear compensation means 93 is coupled to the input of an operational amplifier 94. Also coupled to the input of amplifier 94 is a feedback electrical signal generated by linear variable differential transformer (LVDT) 95 which functions to transduce the position of the yoke of pump 61. into an electrical signal proportional thereto.
  • the amplifier 94 functions to compare the two electrical signals supplied to its input and generate an electrical signal proportional to the difference therebetween.
  • the electrical signal generated by amplifier 94 is coupled to servo driver 96 which functions to supply the desired electrical signals to servo valve 64.
  • Servo valve 64 is mechanically connected to the yoke of pump 61.
  • the desired magnitudes of the constants k,, k and k in formula (I as well as the various resistances, capacitances, inductances to be added to the circuitry and adjustments to the amplifiers to incorporate the constants k and k;; are easily designable by those skilled in the art with only a routine amount of experimentation.
  • control means 65 functions responsive to the electrical signals generated by the pressure transducer 57 and the pressure transducer 60 to cause servo valve 64 to operate pump 61 such that hydraulic fluid is supplied to and from the active chambers 52 and 52'. It has been discovered empirically that when the system is operated in the pressure mode, there is no need to monitor the velocity of the movement of the floating structure relative to the wellhead or the velocity of the movement of the piston rods relative to the outer cylinders. Proper weight control may be obtained simply by monitoring the pressure of the hydraulic fluid in the passive chambers andthe pressure of the hydraulic fluid in the active chambers. Accordingly, it is preferred that the control-means 65 cause pump 61 to supply and withdraw hydraulic fluid to and from the active chambers in accordance with the following equation:
  • Q 1 r z 2 K Q 1 r z 2 K wherein Q is the volume of the hydraulic fluid supplied to or withdrawn from the active chambers, P is the pressure of the hydraulic fluid in thepassive chambers, A, is the effective cross-sectional area of the passive chambers, P is the pressure of the hydraulic fluid in the active chambers, A is the effective cross-sectional area .of the active chambers, and K is the desired hook load.
  • Pressure transducer 57 transduces the pressure of the hydraulic fluid in the passive chambers 51 into an electrical signal proportional thereto.
  • Pressure transducer 60 transduces the pressure of the hydraulic fluid in the active chambers 52 into an electrical signal proportional thereto.
  • Amplifier 101 functions to compare the two electrical signals supplied to its input and generate an electrical signal proportional to the difference therebetween.
  • the electrical signal generated by amplifier 101 is coupled through switch 103 to the input of the conversion means 91.
  • the conversion means 91 and;the remaining components acting responsive to the output of conversion means 91 are as heretofore explained.
  • the electrical signal generated byposition transducer is coupled to the input of operational amplifier.
  • an electrical signal generated by potentiometer 106 which is proportional to a selected, desired linear position of the piston rods 41 relative to the outer cylinders 43.
  • potentiometer 106 is adjusted to generate an electrical signal proportional to the position of the piston rods 41 either at the center of their stroke or at the top of their stroke.
  • Amplifier 104 functions to compare thetwo electrical signals supplied to its input and generate an electrical signal proportional to the difference therebetween.
  • the electrical signal generated by amplifier 104 is coupled through switch 107 to the conversion means 91.
  • switch 107 When this portion of the circuitry is utilized, switch 107 is closed and switches and 103 are opened. Amplifier 104 then generates the necessary electrical signal to cause pump 61 to supply or withdraw hydraulic fluid to and from the active chambers such that, irrespective of the movement of the floating structure or any losses in the system, the piston rods remain at the selected, desired position, such as, at the center of their stroke or at the top of their stroke.
  • Coupled to the output of amplifier 86 is an opera-v tional amplifier 109. Coupled to the other input of such amplifier 109 is an electrical signal generated by potentiometer 1 10, which is adjusted to a selected magnitude. Amplifier 109 functions to compare the two electrical signals supplied to its input and generate a logic signal responsive thereto. Preferably, the potentiometer 110 is adjusted whereby the logic signal generated by amplifier 109 indicates whether the position of the piston rods relative to the center of their stroke equals the position of the floating structure relative to the center of its range of heave.
  • amplifier 109 If this portion of the circuitry is activated, when the position of the floating structure relative to the center of its range of heave equals the position of the piston rods relative to the center of their stroke, amplifier 109 generates a logic signal which causes switch 90 to close and switches 103 and 107 to open. The system then operates in the position mode.
  • an operational amplifier 111 Coupled to the output of amplifier 101 is an operational amplifier 111. Also coupled to the input of amplifier 111 is an electrical signal generated by potentiometer 112, which is adjusted to a preselected magnitude. Amplifier lll functions to compare the two electrical signals supplied to its input and generate a logic signal responsive thereto. Preferably, potentiometer 112 is adjusted whereby the logic signal generated by amplifier 111 indicates when the actual load supported by hook 21 equals thep'reselected hook load K in formula (2). If this portion of .the circuitry is activated, when the actual load supported by the hook equals the preselected hook load, amplifier 111 generates a logic signal which causes switch 103 to close and switches 90 and 107 to open. The system then operates in the pressure mode. l
  • the improved motion compensation and/or weight control system preferably is operated in the position mode when it is desired to maintain a load in a selected position relative to the earthor to move a load at a selected velocity relative to the earth.
  • the earthboring assembly illustrated in FIG. 1 is being utilized to land a 250,000 pound blowout preventer (not shown) on the wellhead 17.
  • the total load supported by hook 21 is 300,000 pounds.
  • the floating structure 13 is experiencing wave heaves six feet in either direction, that is, moving through a total distance of twelve feet.
  • the pressure of the air in the bank 36 of air accumulator tanks will bein the range of 1500 to 2000 pounds per square inch.
  • the total up ward force supplied by the passive portion of the systern will be in the range of approximately 330,000
  • the portion 'of the electrical circuitry in FIG. 4 relating to amplifier 104 is energized by closing switch 107 and opening switches and 103.
  • Pump 61 is thus caused to actively pump hydraulic fluid into active chambers 52-and 52' to provide a downward force opposing the force of the hydraulic fluid in the passive chambers. If the total effective cross-sectional area of the two active chambers is approximately 23 square inches, the pressure of the active fluid supplied to the active chambers will vary within the range of approximately pounds per square inch to 2500 pounds per square inch.
  • Thepressure of the hydraulic fluid in the active chambers 52 and 52' is increased until the piston rods 41 and 41' have been moved downwardly to the position selected in the adjustment of potentiometer 106; preferably the mid-point of their movement range.
  • the ratio of the effective cross-sectional area of the active chambers to the passive chambers preferably is 1:4 or less to reduce the amount of the hydraulic fluid to be moved into and out of the active chambers, thereby reducing the flow rate of the hydraulic fluid through the pump 61 and consequently the required horsepower of the pump 61.
  • the maximum heave in which the-motion compensation and/or weight control system will operate is one that moves the floating structure 20 feet vertically in 18 seconds
  • the velocity of such heave can approach 5 feet per second. It has been determined that to compensate for such five foot per second movement, it may be necessary to move as much as 3100 gallons per minute of hydraulic fluid" into and out of the passive chambers 51 and 51. But if the cross-sectional area of the active chambers is one-fourth or less than that of the passive chamber, then only 730 gallons per minute maximum would have to be actively pumped into and out of the active chambers 52 and 52.
  • the improved motion compensation and/or weight control-system When it'is desired that the improved motion compensation and/or weight control-system according to this invention operate in the position mode to maintain the load in a selected position relative to the earth, the portion of the electrical circuitry in H6. 4 relating to amplifier 109' is'energized.
  • amplifier 109 When the floating structure moves-through the center ofits range of heave (the piston rods are being held at the center of their stroke), amplifier 109 emits a logic signal which closes switch 90 and opens switch 107. Hydraulic fluid is then actively supplied to and withdrawn from the active chambers in accordance with formula (l) above.
  • pump 61 will actively supplyhydraulic fluid into active chambers 52 and 52' at the rate necessary to drive piston rods 41 and 41' downwardly to match the upward movement of the floating vessel.
  • Downward movement of piston rods 41 and 41' of course moves first pistons 47 and 47' downwardly, thereby forcing hydraulic fluid out of the passive chambers 51 and 51 and back into oil/air interface tank 35.
  • control means 65 is operating responsive to signals representative of the movement and the velocity of the movement of the floating structure with respect to the wellhead and the movement and the velocity of the movement of piston rods 41 and 41 with respect to outer cylinders 43 and 43', the control means detects the change in the velocity of the piston rods relative to the outer cylinders as a result of the change in the pressure of the hydraulic fluid in the passive chambers and causes pump 61 to supply even more hydraulic fluid to the active chambers 52 and 52' to overcome these increased upward forces.
  • the piston rods 41 and 41' have been driven downwardly 6 feet.
  • the pressure of the fluid in the passive chambers will have increased such that the total upward forces of the passive portion of the system may be in the range of approximately 360,000 pounds.
  • control means 65 causes pump 61 to commence pumping hydraulic fluid out of the active chambers 52 and 52' and back into the sump 63. Since the upward forces maintain a pressure of 50,000 pounds between the drill on the first pistons 47 and 47 are now increased to approximately 360,000 pounds due to the decrease in the volume of the air in the passive system, piston rods 47 and 47' and the 300,000 pound load depending therefrom easily and smoothly move upwardly relative to the outer cylinders 43 and 43' as the floating structure 13 moves downwardly and hydraulic fluid is pumped out of the active chambers.
  • Pump 61 continues to withdraw hydraulic fluid from the active chambers as the piston rods 41 and 41 moves upwardly, and increases the withdrawal of such hydraulic fluid as necessary to overcome the pressure losses existing in the physical components of the system and the pressure losses attendant to the expansion of the air in the bank 36 of air accumulator tanks and the oil/air interface tank 35.
  • the floating vessel 13 moves upwardly and downary relative to the wellhead.
  • the improved motion compensation and/or weight control system When the improved motion compensation and/or weight control system according to this invention operates in the position mode, it is quite easy to move the load upward or downward at a selected velocity relative to the earth. For example, assume it is desirable to lower the blowout preventer into the wellhead from its present stationary position about the wellhead. This is generally accomplished by causing the draw works 29 to commence unwinding cable so that the traveling block 27, the expansible and contractible mechanism 22, and the load are all lowered toward the wellhead.
  • the control means 65 will not be cognizant of this change in the vertical reference position of the BOP and will continue to generate the necessary electrical signals such that the mechanism 22 will expand and contract to offset the heaves of the floating structure. The BOP can thus be lowered smoothly into place on the wellhead.
  • the improved motion compensation and/or weight control system p'referably is operated in the pressure mode to maintain a selected weight on a tool in contact with the earth (as' will hereinafter be explained), the system may be oper-" ated in the position mode toaccomplish such task.
  • the system may be oper-" ated in the position mode toaccomplish such task.
  • the motion compensation and/or weight control system must therefore supply an upward force of 250,000 pounds to the load. This 250,000 pound load on the hook 21 is the hook load.
  • control means 65 operates responsive to the electrical signals from transducers 81 and 78 and 80 and 75 to cause pump 61 to supply or withdraw hydraulic fluid to or from the active chambers 52 and 52' responsive to the movement of the floating structure 13 relative to the wellhead and the movement of the piston rods 41 and 41' relative to the outer cylinders 43 and 43'.
  • the improved motion compensation and/or weight control system preferably is operated in the position mode to maintain a tool in a selected vertical position (as explained above), the system may also be operated in the pressure mode to maintain a tool in a selected vertical position.
  • the system is supporting a 300,000 pound load comprising a 250,000 pound blowout preventer (not shown) and the drill string to which the BOP is secured. Assume that this blowout preventer is being held ten feet above the wellhead.
  • the air in the bank 36 of accumulator tanks is pressurized to the extent necessary to raise piston rods 41 and 41 the top of their strokes or a point adjacent the top of their strokes.
  • Control means 65 will, responsive to signals from pressure transducers 57 and 60, cause pump 61 to supply additional hydraulic fluid to the active chambers to increase the downward force generated by the hydraulic fluid in such active chambers.
  • the system is operated such that the upward force of the hydraulic fluid in the passive chambers, minus the downward force of the hydraulic fluid in the active chambers, continues to equal the selected upward force of 300,000 pounds necessary to maintain the BOP stationary.
  • Control means 65 will then cause pump 61 to withdraw additional hydraulic fluid from the active chambers 51 and 51 to decrease the downward forcesof the hydraulic fluid in the active chambers whereby the algebraic sum of the upward forces generated by the passive fluid and the downward forces generated by the active fluid continues to equal the 300,000 pound hook load.
  • the motion compensation and/or weight control system preferably is operated in the pressure mode when it is'desired to maintain a selected weight on a tool in contact with the earth.
  • the system is being used with an earth-boring assembly mounted on a floating structure.
  • the hook 21 is supporting a total load of 350,000 comprising a drill stringand drill bit.
  • the toolpusher wishes to maintain the drill bit in contact with the earth at a pressure of 50,000 pounds.
  • the hook load will then be 300,000 pounds.
  • the air in the bank 36 of air accumulator tanks is v pressurized to the magnitude necessary to move piston rods 41 and 41 to the top or near the top of their movement range with the entire 350,000 pound load supported by the hook.
  • suffrcient hydraulic fluid is supplied bypump 61 into the active chambers to lower the. piston rods downward to the mid-point of their movement range.
  • the control means 65 is then set whereby the system operates in the position mode and pump 61 introduces and withdraws hydraulic fluid into and out of the active chambers to maintain the drill string stationary relative to the earth. Cable 26 is then unwound from draw works 29 to the extent necessary to lower traveling block 27 and the expansible and contractible mechanism 22 sufficiently to place the drill bitin contact with the earth.
  • control means 65 operates in accordance with formula (2) above the cause pump 61 to introduce and withdraw hydraulic fluid to and from the active chambers so that the expansible and contractible mechanism 22 will maintain a constant 300,000 pound upward force on theload.
  • the system operates as an automatic driller.
  • the motion compensation and/or weight control system according to this invention is being used as an automatic driller in connection with a stationary earthboring apparatus (such as a land rig), there is no need to move the piston rods 41 and 41 downward a selected distance from the top of their movement range prior to commencing drilling. This downward movement of the piston rods is simply to give the expansible and contractible mechanism 22 room to contract in order to compensate for the possible downward movement of the floating structurefThe rest of the procedure for operating the system would be as previously explained.
  • drawworks 29 is equipped with a commercially available automatic driller, such as the automatic driller manufactured by Martin-Decker, which can unwind the cable 26 responsive to a selected signal
  • the improved motion compensation and/or weight control system can accomplish another desirable function.
  • position transducers or limit switches attached to the expansible and contractible mechanism can be utilized to determine 'when piston rods 41 and 41 have moved downwardly a selected distance.
  • aselected signal can be transmitted to drawworks 29 to cause it to unwind a selected amount of cable 26. Unwindin'g the cable causes the traveling block 27 to be moved 'downwardly a selected distance.
  • control means 65 will sense the increase in the pressure of the hydraulic fluid in the passive chambers and transmit the necessary signal to pump 61 to cause it to withdraw fluid from the active chambers. Piston rods 41 and 41' will then move upwardly to maintain the selected 300,000 pound hook load.
  • the improved motion compensation and/or weight control system of this invention is capable of obtaining maximum accuracy in supporting its load at all points within the telescoping movement range of its expansible and contractible mechanism, but with a minimum of horse-power.
  • the motion compensation and/or weightcontrol system can, due to the interaction of the passive and active portions of the system, provide rapid, smooth, and positive telescoping of its expansible and contractible mechanism, even with heavy hook loads.
  • the passive portion of the system unlike purely passive systems, is pressurized to a magnitude sufficient to move the load upward to the furthest limit of the movement range of the expansible and contractible mechanism.
  • only relatively small volumes of hydraulic fluid compared with purely active systems, need be supplied to or withdrawn from the system to bias the expansible and contractible mechanism to any point of its movement range.
  • the improved motion compensation and/or weight control system has still other advantages over prior purely passive or active systems. For example, even with a given magnitude load, it is often necessary to lift the loada selected distance, such as lifting the drill string to set it on the slips.
  • a purely passive motion compensation and/or weight control system is utilized to so lift the drill string, the pressure of the air in the bank of accumulator tanks must be increased to raise the piston rod above its normal operating position. As these is a large volume of air in the bank of accumulator tanks, considerable horsepower may be utilized. Once the drill bit is to again contact the earth, air must be bled out of the bank of accumulator tanks.
  • the air in the bank of accumulator tanks is pressurized only once for any given loadto a magnitude sufflcient to move the piston rods to the top of their stroke. Thereafter, downward movement of the piston rod is accomplished by providing hydraulic fluid to the active chambers. There is much less horse-power utilized in moving a relatively small volume of a noncompressible hydraulic fluid into and out of the active chambers than in repeatedly pressurizing and depressurizing a relatively large volume of a compressible gas.
  • the embodiment of the expansible and contractible mechanism 22 illustrated in FIGS. 1 and 2 is additionally advantageous in that the active chambers function as deceleration means. If the load should suddenly part and piston rods 41 and 41' move upwardly rapidly, the upward movement of pistons 47 and 47' will tend to force the hydraulic fluid in the active chambers back through conduit 59 and pump 61 into sump 63. The orifices 58 and 58' will restrict this flow and cause the hydraulic fluid in the active chambers to resist the upward movement of the piston rods. Of course the pressure of the hydraulic fluid in the active chambers will increase dramatically. If the inner cylinder 46 was not contained within the piston rod 41, the size of the inner cylinder would have to be substantially larger to withstand these great pressures.
  • the load is attached to hook 21 at an elevation below that at which support member 42 attaches to piston rods 41 and 41'.
  • the system when operated in the position mode, provides compensation for a certain degree of lateral movement of the floating structure. If the floating structure should move laterally from above the wellhead, additional cable 79 will be unwound from drum 38.
  • Control means 65 operting responsive to signals received from the position and velocity transducers 80 and 81 associated with drum 38, will then cause pump 61 to supply additional hydraulic fluid to the active chambers to compensate for this lateral movement.
  • FIG. 5 illustrates an alternate means 37 for actively supplying and withdrawing hydraulic fluid into and from the active chambers 52 and 52'.
  • An auxiliary compensating cylinder 116 is secured by vertical members 117 to the floating structure 13. Movable longitudinally within compensating cylinder 116 is a compensating piston 118. Piston 118 is slidably sealed against the interior of cylinder 116 by seal ring 119. Depending from the compensating piston 118 is a piston rod 120. Piston rod 120 extends through the lower end of compensating cylinder 116 and is slidably sealed there-" against by seal ring 121. Secured to the lower end of piston rod 120 is a cable 122 which is secured to the sea bottom directly or otherwise.
  • variable chamber 123 formed beneath piston 120 and within compensating cylinder 116 is the auxiliary compensating chamber 123.
  • a port 124 is provided in the lower portion of compensating cylinder 116.
  • Conduit 59 from the; active chambers 52 and 52' (FIG. 2) provides fluid communication between the compensating chamber 123 and the active chambers 52 and 52'.
  • hydraulic fluid at a selected pressure is introduced into the closed sys'tem comprising the active chambers 52 and 52', conduit 59, and compensating chamber 123, by means- (-not shown) well known to those skilled in the art.
  • the pressure of such active hydraulic fluid and the effective cross-sectional area of compensating chamber 123 are chosen such that the downward force of the hydraulic fluid in active chambers 52 and 52' against active pistons 50 and 50' will substantially compensate for the errors in the passive portion of the system.
  • compensating piston 118 will move vertically.
  • the increasing and decreasing volume of compensating chamber 123 allows the active hydraulic fluid to flow through conduit 59 between the active chambers 52 and 52 and the compensating chamber 123.
  • the motion compensation and/or weight control system is supporting a 300,000 pound hook load.
  • the air in bank 36 of air accumulator tanks (FIG. 2) has been pressurized to approximately 330,000 pounds.
  • the crosssectional area of compensating chamber 123 and the pressure of the hydraulic fluid therein is such that, with compensating piston 118 in the mid-point of its movementrange, the downward force produced by the hydraulic fluid in active chambers 52 and 52'against active pistons 50 and 50' is approximately 30,000 pounds.
  • the piston rod 41 and 41 are stabilized in the mid-point of their movement. rangerand the 300,000 pound hook load is being supported at equilibrium. I
  • piston rods 47 and 47 will move downwardly with the load. Hydraulic fluid will be forced out of the passive chambers 51 and 51 into the oil/air interface tank 35, thereby compressing the air in the oil/air interface tank and the bank 36 of air accumulator tanks. As the air is compressed, its pressure will increase. Thus, piston rods 41 and 41 will not move downward as far as they should to compensate for the upward movement of the floating structure 13. However, as floating structure 13 moves upward, compensating piston 118 is pulled downward in compensating cylinder 116. This decreases the volume of compensating chamber 23 and forces hydraulic fluid from compensating chamber 123 through conduit 59 into the-active chambers 52 and 52.
  • the pressure ofthe hydraulic fluid contained in compensating chamber 123 and the cross-sectional area of compensating chamber 123 has been chosen such that the increased force against active pistons 50 and 50' inactive chambers 52 and 52 substantially equals and cancels the increase in the pressuure of the hydraulic fluid in the passive chambers 51 and 51.
  • the piston rods 41 and 41 are moved downwardly to their proper position to compensate for the upward movement of floating structure 13.
  • outer cylinder 43 has an eyelet 127 secured thereto for engagement with a hook 128 depending from the'traveling block 27.
  • the single piston and cylinder assembly is constructed identical to the piston and cylinder assembly 39 described in FIG. 2.
  • hook 21 is secured to piston 50 at the lower end of piston rod 41. Hook 21 engages with an eyelet 129 secured to the top of swivel 20.
  • expansible and contractible mechanism .22 illustrated in FIG. 6 may be disconnected from the traveling block 27 and stored inside the derrick or on the floating structure 13. This eliminates weight during the'tripping cycle and thus reduces cable wear'and pulley wear.
  • the expansible and-contractible mechanism 22 can be reattached beneath the traveling block 27.
  • FIG. 7 illustrates an alternate embodiment of the improved motion compensation and/or weight control system according to this invention wherein the system is adapted for use with an earth-boring assembly utilizing a drill head rather than cables and blocks.
  • Secured to floating structure 13 are vertical members 131 which support a horizontal support member 132.
  • Secured to horizontal support member 132 is an expansible and contractible mechanism 22 according to this invention such as is illustrated and described in FIG. 2.
  • a drill head assembly 133 such as is well known to those skilled in the art.
  • a drill string14 is Depending from the drill head assembly 133. I
  • Hydraulic fluid preferably is supplied to and withdrawn from the active chambers 52 of the expansible and contractible mmechanism-22 by the control means 65 andrelated equipment illustrated in FIG. -2 or the means 37 illustrated in FIG. 5.
  • FIG. 8 illustrates an alternate embodiment of the expansible and contractible mechanism 22 of the improved motion compensation and/or weight control system according to this invention.
  • a first support member 134 and a second support member 135 Secured between a first support member 134 and a second support member 135 are two passive piston and cylinder assemblies 136 and 136' and two active piston and cylinder assemblies 137 and 13.7.
  • the piston and cylinder assemblies could ofcourse extend upward-on either side of the traveling block 27.
  • the forces produced by the active piston and cylinder assemblies 137 and 137' oppose the forces produced by the passive piston and cylinder assemblies 136 and 136.
  • the operation ofthe motion compensation and/or weight control system with the expansible and contractible mechanism22 illustrated in FIG. 8 is as previously described with respect to FIGS; 1 through 5.
  • Hydraulic fluid preferably 'is supplied to and withdrawn from each of the active piston and'cylinder assemblies either by the control means 65 and related equipment illustrated in FIG. 2'or the means. 37,illustrated in FIG. 5.
  • FIG. 9 illustrates still another embodiment of an expansible and contractible mechanism 22 of the improved motion' compensation and/or weight control system according to this invention.
  • a cable 142 and 142 is reeved around pul leys 141 and 141 and extended downwardly through an opening (not shown) in support member 40. Cables 142 and 142 are secured to a support member 143 from which depends hook 21.
  • the variable chambers 144 beneath the pistons 139 are the passive chambers.
  • the annular chambers 145 formed between piston rods 140 and 140' andcylinders 138 and 138' are the active chambers.
  • Piston rods 140 and 140 are preferably formed to have a large crosssectional area such that the cross-sectional area of the annular active chambers 145 are onefourth or less the cross-sectional area of the passive chambers 144.
  • Hydraulic fluid is supplied and withdrawn from the passive chambers through conduit 146.
  • 'Hydraulic fluid is supplied to and withdrawn from the active chambers through'conduit 147.
  • the means for supplying hydraulic fluid to the passive'chambers preferably is as illustrated in FIG. 2.
  • the means for providing hydraulic fluid to the active chambers preferably is 'as illustrated in FIG. 2 or as illustrated in FIG. 5. I
  • FIG. 10 illustrates still another embodiment of the improved motion compensation and/or weight control system according to this invention.
  • the manner of employing the expansible and contractible mechanism 22 within a derrick or otherwise is not shown.
  • Extending longitudinally within and depending from outer cylinder 43 is an inner cylinder 46.
  • Movable longitudinally within the annular chamber between theinner cylinder 46"and the outer cylinder 43 is a first piston 47.
  • Attached to the first piston 47 is a pistonrod 41 which slides along the outside of inner cylinder 46.
  • second piston 50 Secured to the lower end of piston rod 41.
  • Inner cylinder 46, first piston 47, piston rod41, and outer cylinder 43 are all secured in a slidable, sealing relationship whereby a primary chamber 51 and a secondary chamber 52 are formed similarly as described with respect to FIG. 2.
  • Hydraulic fluid is passively supconduit 151 connects between this second port 150 and a port 152 at the top of secondary chamber 52.
  • secondarychamber 5l' is iri fluid communication withp'rimary chamber 52.
  • piston rod 41 In operation, assume that piston rod 41 is supporting a 300,000 pound load.
  • the air in accumulator bank 36 is pressurized to .a magnitude sufficient to support such load and move piston rod 41 to the approximate midpoint of its movement range.
  • the pressure of the hydraulic fluid will be the same in the primary chamber 51 and the secondary chamber 52. Assuming that the ratio of the cross-sectional area of the primary chamber to the secondary chamber is precisely 4: l, the upward force of the hydraulic fluid against pi,ston.47 may be 400,000 pounds and the downward force of the hydraulic fluid against piston 50 may be 100,000 pounds.
  • the opposing downward force of the hydraulic fluid in the secondary chamber 52 is also increased somewhat due to the increasee of the pressure of the hydraulic fluid contained therein. This increase in the opposing force produced by the hydraulic fluid in the secondary c'hamber 52 decreases th'etotal error in the compensation or weight control.
  • FIG. 10 is a modified passive' system wherein the compensation losses inherent in the prior art purely passive systems are decreased.
  • a load-supporting assembly for supporting a load which is'movable' relative to the load-supporting assem- 'blyfian improved motion compensation and/or weight control system, comprising:
  • a cylindrical piston rod slidably disposed around the inner cylinder and extending through the second end plate of the outer cylinder for longitudinal movement relative thereto;
  • one of the outer cylinder or the piston rod being mounted for movement with the load-supporting assembly and the other of the outer cylinder or the piston rod being mounted for movement with the load;
  • variable volume chamber formed within the first end plate of the outer cylinder, the inner cylinder, the piston rod, and the second piston, being the secondary chamber;
  • an improved motion compensation and/or weight control system in a load-supporting assembly for supporting a load which is movable relative to the load-supporting assembly, an improved motion compensation and/or weight control system according to claim 1 wherein the means for passively supplying fluid under pressure to the primary chamber includes:
  • a pneumatic-hydraulic interface means in fluid communication with the pneumatic-accumulator interface means and the primary chamber.
  • an improved motion compensation and/or weight control system in a load supporting assembly for supporting a load which is movable relative to the load-supporting assembly, an improved motion compensation and/or weight control system according to claim 1, wherein the means for actively supplying fluid into and allowing thewithdrawal of fluid out of the secondary chamber includes:
  • variable volume, bi-directional pump in fluid communication with the source of hydraulic fluid and in fluid communication with the active chamber
  • control means for controlling the direction and the volume of the hydraulic fluid pumped by such pump.
  • an improved motion compensation and/or weight control system in a load-supporting assembly for supporting a load which is movable relative to the load-supporting assembly, an improved motion compensation and/or weight control system according to claim 1 wherein the means for actively supplying fluid into and allowing the withdrawal of fluid out of the secondary chamber includes:
  • the compensating chamber, the secondary chamber, and the interconnecting conduit being filled with hydraulic fluid.
  • an improved motion compensation and/or weight control system comprising:
  • one of the outer cylinder or the piston rod being mounted for movement with the load-supporting assembly and the other of the outer cylinder or the piston rod being mounted for movement with the load;
  • variable volume chamber formed within the first end plate of the outer cylinder, the inner cylinder, the piston rod, and the second piston, being the secondary chamber;
  • an improved motion compensation and/or weight control system comprising:

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US407051A 1973-10-17 1973-10-17 Motion compensation and/or weight control system Expired - Lifetime US3912227A (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
US407051A US3912227A (en) 1973-10-17 1973-10-17 Motion compensation and/or weight control system
GB5238675A GB1476672A (en) 1973-10-17 1974-08-28 Motion compensation and/or weight control system
GB5239775A GB1476673A (en) 1973-10-17 1974-08-28 Motion compensation and/or weight control system
GB3762874A GB1476671A (en) 1973-10-17 1974-08-28 Motion compensation and/or weight control system
AU73102/74A AU7310274A (en) 1973-10-17 1974-09-09 Motion compensating and/or weight control for drilling apparatus
JP49116802A JPS5067201A (ja) 1973-10-17 1974-10-09
DE19742448813 DE2448813A1 (de) 1973-10-17 1974-10-14 Verfahren und system zur bewegungskompensation und/oder gewichtssteuerung fuer eine lasttragende vorrichtung, insbesondere eine erdbohrvorrichtung
NL7413626A NL7413626A (nl) 1973-10-17 1974-10-16 Bewegingscompensatie-inrichting.
FR7434842A FR2248225A1 (ja) 1973-10-17 1974-10-16
NO800210A NO800210L (no) 1973-10-17 1980-01-29 Anordning for kompensering for bevegelse og/eller for regulering av vekt, hos en konstruksjon som baerer en last
NO800211A NO800211L (no) 1973-10-17 1980-01-29 Anordning for kompensering for bevegelse og/eller for regulering av vekt, hos en konstruksjon som baerer en last

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AU (1) AU7310274A (ja)
DE (1) DE2448813A1 (ja)
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US20140331908A1 (en) * 2013-05-09 2014-11-13 Icon Engineering Pty Ltd Heave compensation and tensioning apparatus, and method of use thereof
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US20160039643A1 (en) * 2014-08-08 2016-02-11 Ernst-B. Johansen AS Multi function heave compensator
US9718653B2 (en) * 2014-08-08 2017-08-01 Ernst-B. Johansen AS Multi function heave compensator
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NO800211L (no) 1975-04-18
NL7413626A (nl) 1975-04-21
NO800210L (no) 1975-04-18
GB1476671A (en) 1977-06-16
JPS5067201A (ja) 1975-06-05
GB1476673A (en) 1977-06-16
AU7310274A (en) 1976-03-11
FR2248225A1 (ja) 1975-05-16
DE2448813A1 (de) 1975-04-24
GB1476672A (en) 1977-06-16

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