US007080607B2
`
`(12) United States Patent
`Hillesund et a].
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 7,080,607 B2
`*Jul. 25, 2006
`
`(54) SEISMIC DATA ACQUISITON EQUIPMENT
`CONTROL SYSTEM
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`(75) I
`nventors:
`
`GB s'
`Oyv' d H'll
`d H'
`lIIlOIl
`;
`1ston
`1 esun ,
`1n
`Hastings Bittleston, Bury St Edmunds
`(GB)
`
`(73) Assignee: WesternGeco, L.L.C., Houston, TX
`(Us)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`This patent is subject to a terminal dis
`claimer.
`
`(21) Appl. N0.: 11/070,614
`
`(22) Filed:
`
`Mar. 2, 2005
`
`(65)
`
`Prior Publication Data
`
`US 2005/0188908 A1
`
`Sep. 1, 2005
`
`Related US. Application Data
`
`(63) Continuation of application No. 09/787,723, ?led as
`application No. PCT/lB99/01590 on Sep. 28, 1999,
`noW Pat. No. 6,932,017.
`
`(30)
`
`Foreign Application Priority Data
`
`Oct. 1, 1998
`
`(GB) ............................... .. 98212773
`
`(51) Int. C1.
`(2006.01)
`3633 21/66
`(2006.01)
`B63B 21/56
`(52) US. Cl. .................................................... .. 114/244
`(58) Field of Classi?cation Search .............. .. 114/162,
`114/163, 2424246, 253
`See application ?le for complete search history.
`
`4/1968 Cole et a1. ................ .. 114/235
`3,375,800 A
`3,412,705 A ll/l968 Nesson .... ..
`115/12
`3,434,446 A
`3/1969 Cole .... ..
`114/235
`3,440,992 A
`4/1969 Chance .... ..
`114/235
`3,560,912 A
`2/1971 Spink et a1.
`....... .. 340/3
`3,605,674 A
`9/1971 Weese ............ ..
`114/235 B
`3,648,642 A
`3/1972 FetroW et a1.
`.... .. 114/235
`3,774,570 A ll/l973 Pearson ................ .. 114/235 B
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`AU
`
`199853305
`12/1997
`(Continued)
`Primary Examinerilesus D. Sotelo
`
`(74) Attorney, Agent, or F irmiWesternGeco, L.L.C.
`
`(57)
`
`ABSTRACT
`
`A method of controlling a streamer positioning device
`con?gured to be attached to a marine seismic streamer and
`toWed by a seismic survey vessel and having a Wing and a
`Wing motor for changing the orientation of the Wing. The
`method includes the steps of: obtaining an estimated veloc
`ity of the streamer positioning device, calculating a desired
`change in the orientation of the Wing using the estimated
`velocity of the streamer positioning device, and actuating
`the Wing motor to produce the desired change in the orien
`tation of the Wing. The invention also involves an apparatus
`for controlling a streamer positioning device including
`means for obtaining an estimated velocity of the streamer
`positioning device, means for calculating a desired change
`in the orientation of the Wing using the estimated velocity of
`the streamer positioning device, and means for actuating the
`Wing motor to produce the desired change in the orientation
`of the Wing.
`
`25 Claims, 3 Drawing Sheets
`
`26..’
`
`28
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 1
`
`

`
`US 7,080,607 B2
`Page 2
`
`US. PATENT DOCUMENTS
`
`5,619,474 A
`
`4/1997 Kuche ....................... .. 367/17
`
`7/1975 Pearson 6161. ....... .. 114/235 B
`3 896 756 A
`1/1976 c616 ......................... .. 367/17
`3,931,608 A
`3/1976 s1r6rig6 .................. .. 340/7 PC
`3:943:483 A
`6,1976 Pal-won
`“ 367,17
`3,961,303 A
`7/1977 W616rs ..................... .. 114/245
`4,033,278 A
`4,063,213 A 12/1977 11ri66161. ................... .. 367/17
`4,087,780 A
`5/1978 Mia etal,
`367m
`4,222,340 A
`9/1980 c616 ........................ .. 114/245
`4,227,479 A 10/1980 G61116r6161. ............ .. 114/312
`4,290,124 A
`9/19g1
`__ 367/1g
`4,313,392 A
`2/1982 Gir6ri11r6r6161. ......... .. 114/244
`4,323,989 A
`4/1982 111161161566 6161. .......... .. 367/17
`
`
`
`Zachariadis . . . . . .. 8/1984 Pi1611<161161d61 Wii ....... .. 114/245 ..
`A 4,463,701 A
`
`
`4,484,534 A 11 1984 T i 6y6 uBOu 6y
`114 244
`4,676,183 A
`6/1987 Conboy ............. ..
`. 114/245
`4,694,435 A
`9/1987 M6gri6vi116 ................ .. 367/17
`4,709,355 A 11/1987 Woods 6161. ............... .. 367/16
`4,711,194 A 12/1987 F6w16r ........ ..
`114/245
`4,723,501 A
`2/1988 H6vd6ri 6161. ....... .. 114/144 B
`4,729,333 A
`3/1988 Kirby 6161. .............. .. 114/244
`4,745,583 A
`5/1988 M6161 ....... ..
`.. 367/18
`4,766,441 A
`8/1988 Phillips .................... .. 343/709
`4,767,183 A
`8/1988 M6r1iri .................. .. 350/9623
`4,843,996 A
`7/1989 13616116 ..... ..
`. 114/245
`4,890,568 A
`1/1990 DOleIlgOWSki ............ .. 114/246
`4,890,569 A
`1/1990 GiVeIlS ..................... .. 114/349
`4,912,684 A
`3/1990 Fowler ........ ..
`.. 367/76
`4,992,990 A
`2/1991 Langeland et a1. ......... .. 367/19
`5,042,413 A
`8/1991 Benoit ...................... .. 114/244
`5,052,814 A 10/1991 Stubble?eld
`.. 367/15
`5,402,745 A
`4/1995 Wood ....................... .. 114/244
`5,443,027 A
`8/1995 Owsley et a1. ............ .. 114/244
`5,507,243 A
`4/1996 Williams et a1.
`114/245
`5,517,202 A
`5/1996 Patel ........................ .. 343/709
`5,517,463 A
`5/1996 Hornbostel et a1. ......... .. 367/13
`5,529,011 A
`6/1996 Williams, Jr.
`. 114/245
`5,532,975 A
`7/1996 Elholm ...................... .. 367/16
`
`' 367ml
`6/1997 Santopietro '
`5’642’330 A
`" 367/19
`8/1998 Workman et a1‘
`5’790’472 A
`" 367/ 17
`V2000 Ambs et a1‘ '
`6911752 A
`1/2000 (3111611 ........................ .. 367/21
`6,011,753 A
`V2000 01m“ et al' ~~~~~~~~~~~~~~ ~- 367/ 17
`6,016,286 A
`6,144,342 A 11/2000 Bertheas eta1~ ~~~~~~~~~~ ~~ 343/709
`6,459,653 B1
`10/2002 @6116 ....................... .. 367/17
`6525992 B1
`2/2003 Olivier er a1-
`-- 367/17
`6,549,653 B1
`4/2003 OsaWa er a1 ------------- -- 382/162
`6,879,542 B1
`4/2005 Soreau et 61. ............... .. 367/17
`
`FOREIGN PATENT DOCUMENTS
`
`CA
`
`BE
`EP
`
`EP
`EP
`EP
`EP
`EP
`EP
`GB
`GB
`GB
`GB
`NO
`W0
`W0
`W0
`W0
`W0
`W0
`W0
`
`2270719
`
`B
`
`121997
`
`63335;? T
`0319716
`
`‘l‘?ggé
`6/1989
`
`6/1989
`0321705
`“993
`0525391
`12/1993
`0390987
`613025 A1 * 8/1994
`0581441
`8/1997
`0909701
`V2003
`2093610
`9/1982
`2122562
`1/1984
`2331971
`6/1999
`2342031
`4/2000
`992701
`6/1999
`WO95/31735
`11/1995
`WO96/21163
`7/1996
`WO97/11395
`3/1997
`WO97/3036l
`8/1997
`WO97/45006
`12/1997
`WO98/28636
`7/1998
`WO99/04293
`1/1999
`
`* cited by examiner
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 2
`
`

`
`U.S. Patent
`
`Jul. 25, 2006
`
`Sheet 1 of3
`
`US 7,080,607 B2
`
`Fig.1 .
`Prior Art
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 3
`
`

`
`U.S. Patent
`
`Jul. 25, 2006
`
`Sheet 2 0f 3
`
`US 7,080,607 B2
`
`Fig.2.
`
`26..’ (1 3r24
`
`/18
`
`28
`
`34
`
`>24
`
`28
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 4
`
`

`
`U.S. Patent
`
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`PGS v. WESTERNGECO (|PR20‘|4-00689)
`WESTERNGECO Exhibit 2043, pg. 5
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 5
`
`
`
`
`
`

`
`US 7,080,607 B2
`
`1
`SEISMIC DATA ACQUISITON EQUIPMENT
`CONTROL SYSTEM
`
`Applicant claims priority and continuation under 35
`U.S.C. § 120 from parent application Ser. No. 09/787,723,
`?led Jul. 2, 2001, now US. Pat. No. 6,932,017, Which Was
`a 35 U.S.C. § 371 national stage ?ling from Patent Coop
`eration Treaty application number PCT/IB99/01590, ?led
`Sep. 28, 1999, Which in turn claimed priority from Great
`Britain patent application number 98212773, ?led Oct. 1,
`1998, from Which Applicant has claimed foreign priority
`under 35 U.S.C. § 119.
`
`BACKGROUND OF THE INVENTION
`
`This invention relates generally to systems for controlling
`seismic data acquisition equipment and particularly to a
`system for controlling a marine seismic streamer positioning
`device.
`A marine seismic streamer is an elongate cable-like
`structure, typically up to several thousand meters long,
`Which contains arrays of seismic sensors, knoWn as hydro
`phones, and associated electronic equipment along its
`length, and Which is used in marine seismic surveying. In
`order to perform a 3D marine seismic survey, a plurality of
`such streamers are toWed at about 5 knots behind a seismic
`survey vessel, Which also toWs one or more seismic sources,
`typically air guns. Acoustic signals produced by the seismic
`sources are directed doWn through the Water into the earth
`beneath, Where they are re?ected from the various strata.
`The re?ected signals are received by the hydrophones, and
`then digitized and processed to build up a representation of
`the subsurface geology.
`The horizontal positions of the streamers are typically
`controlled by a de?ector, located at the front end or “head”
`of the streamer, and a tail buoy, located at the back end or
`“tail” of the streamer. These devices create tension forces on
`the streamer Which constrain the movement of the streamer
`and cause it to assume a roughly linear shape. Cross currents
`and transient forces cause the streamer to boW and undulate,
`thereby introducing deviations into this desired linear shape.
`The streamers are typically toWed at a constant depth of
`approximately ten meters, in order to facilitate the removal
`of undesired “ghost” re?ections from the surface of the
`Water. To keep the streamers at this constant depth, control
`devices knoWn as “birds”, are typically attached at various
`points along each streamer betWeen the de?ector and the tail
`buoy, With the spacing betWeen the birds generally varying
`betWeen 200 and 400 meters. The birds have hydrodynamic
`de?ecting surfaces, referred to as Wings, that alloW the
`position of the streamer to be controlled as it is toWed
`through the Water. When a bird is used for depth control
`purposes only, it is possible for the bird to regularly sense its
`depth using an integrated pressure sensor and for a local
`controller Within the bird to adjust the Wing angles to
`maintain the streamer near the desired depth using only a
`desired depth value received from a central control system.
`While the majority of birds used thus far have only
`controlled the depth of the streamers, additional bene?ts can
`be obtained by using properly controlled horizontally steer
`able birds, particularly by using the types of horizontally and
`vertically steerable birds disclosed in our published PCT
`International Application No. WO 98/28636. The bene?ts
`that can be obtained by using properly controlled horizon
`tally steerable birds can include reducing horizontal out-of
`position conditions that necessitate reacquiring seismic data
`in a particular area (i.e. in-?ll shooting), reducing the chance
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`of tangling adjacent streamers, and reducing the time
`required to turn the seismic acquisition vessel When ending
`one pass and beginning another pass during a 3D seismic
`survey.
`It is estimated that horizontal out-of-position conditions
`reduce the e?iciency of current 3D seismic survey opera
`tions by betWeen 5 and 10%, depending on Weather and
`current conditions. While incidents of tangling adjacent
`streamers are relatively rare, When they do occur they
`invariably result in prolonged vessel doWntime. The loss of
`e?iciency associated With turning the seismic survey vessel
`Will depend in large part on the seismic survey layout, but
`typical estimates range from 5 to 10%. Simulations have
`concluded that properly controlled horizontally steerable
`birds can be expected to reduce these types of costs by
`approximately 30%.
`One system for controlling a horizontally steerable bird,
`as disclosed in UK Patent GB 2093610 B, is to utilize a
`manually-operated central control system to transmit the
`magnitudes and directions of any required Wing angle
`changes to the birds. While this method greatly simpli?es
`the circuitry needed Within the bird itself, it is virtually
`impossible for this type of system to closely regulate the
`horizontal positions of the birds because it requires manual
`input and supervision. This becomes a particularly signi?
`cant issue When a substantial number of streamers are
`deployed simultaneously and the number of birds that must
`be controlled goes up accordingly.
`Another system for controlling a horizontally steerable
`bird is disclosed in our published PCT International Appli
`cation No. WO 98/28636. Using this type of control system,
`the desired horizontal positions and the actual horizontal
`positions are received from a remote control system and are
`then used by a local control system Within the birds to adjust
`the Wing angles. The actual horizontal positions of the birds
`may be determined every 5 to 10 seconds and there may be
`a 5 second delay betWeen the taking of measurements and
`the determination of actual streamer positions. While this
`type of system alloWs for more automatic adjustment of the
`bird Wing angles, the delay period and the relatively long
`cycle time betWeen position measurements prevents this
`type of control system from rapidly and e?iciently control
`ling the horizontal position of the bird. A more deterministic
`system for controlling this type of streamer positioning
`device is therefore desired.
`It is therefore an object of the present invention to provide
`for an improved method and apparatus for controlling a
`streamer positioning device.
`An advantage of the present invention is that the position
`of the streamer may be better controlled, thereby reducing
`the need for in-?ll shooting, reducing the chance of streamer
`tangling, and reducing the time needed to turn the seismic
`survey vessel.
`Another advantage of the present invention is that noise in
`marine seismic data associated With streamer position over
`correction and streamer positioning errors can be signi?
`cantly reduced.
`
`SUMMARY OF THE INVENTION
`
`The present invention involves a method of controlling a
`streamer positioning device con?gured to be attached to a
`marine seismic streamer and toWed by a seismic survey
`vessel and having a Wing and a Wing motor for changing the
`orientation of the Wing. The method includes the steps of:
`obtaining an estimated velocity of the streamer positioning
`device, calculating a desired change in the orientation of the
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 6
`
`

`
`US 7,080,607 B2
`
`3
`Wing using the estimated velocity of the streamer position
`ing device, and actuating the Wing motor to produce the
`desired change in the orientation of the Wing. The present
`invention also involves an apparatus for controlling a
`streamer positioning device. The apparatus includes means
`for obtaining an estimated velocity of the streamer position
`ing device, means for calculating a desired change in the
`orientation of the Wing using the estimated velocity of the
`streamer positioning device, and means for actuating the
`Wing motor to effectuate the desired change in the orienta
`tion of the Wing. The invention and its bene?ts Will be better
`understood With reference to the detailed description beloW
`and the accompanying ?gures.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic diagram of a seismic survey vessel
`and associated seismic data acquisition equipment,
`FIG. 2 is a schematic horiZontal cross-sectional vieW
`through a marine seismic streamer and an attached streamer
`positioning device;
`FIG. 3 is a schematic vertical cross-sectional vieW
`through the streamer positioning device from FIG. 2; and
`FIG. 4 is a schematic diagram of the local control system
`architecture of the streamer positioning device from FIG. 2.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`In FIG. 1, a seismic survey vessel 10 is shoWn toWing
`eight marine seismic streamers 12 that may, for instance,
`each be 3000 meters in length. The outermost streamers 12
`in the array could be 700 meters apart, resulting in a
`horizontal separation betWeen the streamers of 100 meters in
`the regular horiZontal spacing con?guration shoWn. A seis
`mic source 14, typically an airgun or an array of airguns, is
`also shoWn being toWed by the seismic survey vessel 10. At
`the front of each streamer 12 is shoWn a de?ector 16 and at
`the rear of every streamer is shoWn a tail buoy 20. The
`de?ector 16 is used to horiZontally position the end of the
`streamer nearest the seismic survey vessel 10 and the tail
`buoy 20 creates drag at the end of the streamer farthest from
`the seismic survey vessel 10. The tension created on the
`seismic streamer by the de?ector 16 and the tail buoy 20
`results in the roughly linear shape of the seismic streamer 12
`shoWn in FIG. 1.
`Located betWeen the de?ector 16 and the tail buoy 20 are
`a plurality of streamer positioning devices knoWn as birds
`18. Preferably the birds 18 are both vertically and horiZon
`tally steerable. These birds 18 may, for instance, be located
`at regular intervals along the steamer, such as every 200 to
`400 meters. The vertically and horizontally steerable birds
`18 can be used to constrain the shape of the seismic streamer
`12 betWeen the de?ector 16 and the tail buoy 20 in both the
`vertical (depth) and horiZontal directions.
`In the preferred embodiment of the present invention, the
`control system for the birds 18 is distributed betWeen a
`global control system 22 located on or near the seismic
`survey vessel 10 and a local control system located Within or
`near the birds 18. The global control system 22 is typically
`connected to the seismic survey vessel’s navigation system
`and obtains estimates of system Wide parameters, such as the
`vessel’s toWing direction and velocity and current direction
`and velocity, from the vessel’s navigation system.
`The most important requirement for the control system is
`to prevent the streamers 12 from tangling. This requirement
`becomes more and more important as the complexity and the
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`total value of the toWed equipment increases. The trend in
`the industry is to put more streamers 12 on each seismic
`survey vessel 10 and to decrease the horiZontal separation
`betWeen them. To get better control of the streamers 12,
`horiZontal steering becomes necessary. If the birds 18 are not
`properly controlled, horiZontal steering can increase, rather
`than decrease, the likelihood of tangling adjacent streamers.
`LocaliZed current ?uctuations can dramatically in?uence the
`magnitude of the side control required to properly position
`the streamers. To compensate for these localiZed current
`?uctuations, the inventive control system utiliZes a distrib
`uted processing control architecture and behavior-predictive
`model-based control logic to properly control the streamer
`positioning devices.
`In the preferred embodiment of the present invention, the
`global control system 22 monitors the actual positions of
`each of the birds 18 and is programmed With the desired
`positions of or the desired minimum separations betWeen the
`seismic steamers 12. The horiZontal positions of the birds 18
`can be derived, for instance, using the types of acoustic
`positioning systems described in our US. Pat. No. 4,992,990
`or in our PCT International Patent Application No. WO
`98/21163. Alternatively, or additionally, satellite-based glo
`bal positioning system equipment can be used to determine
`the positions of the equipment. The vertical positions of the
`birds 18 are typically monitored using pressure sensors
`attached to the birds, as discussed beloW.
`The global control system 22 preferably maintains a
`dynamic model of each of the seismic streamers 12 and
`utiliZes the desired and actual positions of the birds 18 to
`regularly calculate updated desired vertical and horiZontal
`forces the birds should impart on the seismic streamers 12 to
`move them from their actual positions to their desired
`positions. Because the movement of the seismic streamer 12
`causes acoustic noise (both from seaWater ?oW past the bird
`Wing structures as Well as cross current ?oW across the
`streamer skin itself), it is important that the streamer move
`ments be restrained and kept to the minimum correction
`required to properly position the streamers. Any streamer
`positioning device control system that consistently overes
`timates the type of correction required and causes the bird to
`overshoot its intended position introduces undesirable noise
`into the seismic data being acquired by the streamer. In
`current systems, this type of over-correction noise is often
`balanced against the “noise” or “smearing” caused When the
`seismic sensors in the streamers 12 are displaced from their
`desired positions.
`The global control system 22 preferably calculates the
`desired vertical and horiZontal forces based on the behavior
`of each streamer and also takes into account the behavior of
`the complete streamer array. Due to the relatively loW
`sample rate and time delay associated With the horiZontal
`position determination system, the global control system 22
`runs position predictor softWare to estimate the actual loca
`tions of each of the birds 18. The global control system 22
`also checks the data received from the vessel’s navigation
`system and the data Will be ?lled in if it is missing. The
`interface betWeen the global control system 22 and the local
`control system Will typically operate With a sampling fre
`quency of at least 0.1 HZ. The global control system 22 Will
`typically acquire the folloWing parameters from the vessel’s
`navigation system: vessel speed (m/s), vessel heading (de
`grees), current speed (m/ s), current heading (degrees), and
`the location of each of the birds in the horiZontal plane in a
`vessel ?xed coordinate system. Current speed and heading
`can also be estimated based on the average forces acting on
`the streamers 12 by the birds 18. The global control system
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 7
`
`

`
`US 7,080,607 B2
`
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`22 Will preferably send the following values to the local bird
`controller: demanded vertical force, demanded horizontal
`force, towing velocity, and crosscurrent velocity.
`The towing velocity and crosscurrent velocity are prefer
`ably “Water-referenced” values that are calculated from the
`vessel speed and heading values and the current speed and
`heading values, as Well as any relative movement betWeen
`the seismic survey vessel 10 and the bird 18 (such as While
`the vessel is turning), to produce relative velocities of the
`bird 18 With respect to the Water in both the “in-line” and the
`“cross-line” directions. Alternatively, the global control sys
`tem 22 could provide the local control system With the
`horizontal velocity and Water in-?oW angle. The force and
`velocity values are delivered by the global control system 22
`as separate values for each bird 18 on each streamer 12
`continuously during operation of the control system.
`The “Water-referenced” toWing velocity and crosscurrent
`velocity could alternatively be determined using ?oWmeters
`or other types of Water velocity sensors attached directly to
`the birds 18. Although these types of sensors are typically
`quite expensive, one advantage of this type of velocity
`determination system is that the sensed in-line and cross-line
`velocities Will be inherently compensated for the speed and
`heading of marine currents acting on said streamer position
`ing device and for relative movements betWeen vessel 10
`and the bird 18.
`FIG. 2 shoWs a type of bird 18 that is capable of
`controlling the position of seismic streamers 12 in both the
`vertical and horizontal directions. A bird 18 of this type is
`also disclosed in our PCT lntemational Application No. WO
`30
`98/28636. While a number of alternative designs for the
`vertically and horizontally steerable birds 18 are possible,
`including those utilizing one full-moving Wing With aile
`rons, three full-moving Wings, and four full-moving Wings,
`the independent tWo-Wing principal is, conceptually, the
`simplest and most robust design.
`In FIG. 2, a portion of the seismic streamer 12 is shoWn
`With an attached bird 18. A communication line 24, Which
`may consist of a bundle of ?ber optic data transmission
`cables and poWer transmission Wires, passes along the
`length of the seismic streamer 12 and is connected to the
`seismic sensors, hydrophones 26, that are distributed along
`the length of the streamer, and to the bird 18. The bird 18
`preferably has a pair of independently moveable Wings 28
`that are connected to rotatable shafts 32 that are rotated by
`Wing motors 34 and that alloW the orientation of the Wings
`28 With respect to the bird body 30 to be changed. When the
`shafts 32 of the bird 18 are not horizontal, this rotation
`causes the horizontal orientation of the Wings 28 to change
`and thereby changes the horizontal forces that are applied to
`the streamer 12 by the bird.
`The motors 34 can consist of any type of device that is
`capable of changing the orientation of the Wings 28, and they
`are preferably either electric motors or hydraulic actuators.
`The local control system 36 controls the movement of the
`Wings 28 by calculating a desired change in the angle of the
`Wings and then selectively driving the motors 34 to effec
`tuate this change. While the preferred embodiment depicted
`utilizes a separate motor 34 for each Wing 28, it Would be
`also be possible to independently move the Wings 28 using
`a single motor 34 and a selectively actuatable transmission
`mechanism.
`When the bird 18 uses tWo Wings 28 to produce the
`horizontal and vertical forces on the streamer 12, the
`required outputs of the local control system 36 are relatively
`simple, the directions and magnitudes of the Wing move
`ments required for each of the Wings 28, or equivalently the
`
`50
`
`40
`
`45
`
`55
`
`60
`
`65
`
`6
`magnitude and direction the motors 34 need to be driven to
`produce this Wing movement. While the required outputs of
`the local control system 36 for such a tWo full moving Wing
`design is quite simple, the structure and operation of the
`overall system required to coordinate control of the device
`is relatively complicated.
`FIG. 3 shoWs a schematic vertical cross-sectional vieW
`through the streamer positioning device shoWn in FIG. 2 that
`Will alloW the operation of the inventive control system to be
`described in more detail. The components of the bird 18
`shoWn in FIG. 3 include the Wings 28 and the body 30. Also
`shoWn in FIG. 3 are a horizontal coordinate axis 38 and a
`vertical coordinate axis 40. During operation of the streamer
`positioning control system, the global control system 22
`preferably transmits, at regular intervals (such as every ?ve
`seconds) a desired horizontal force 42 and a desired vertical
`force 44 to the local control system 36.
`The desired horizontal force 42 and the desired vertical
`force 44 are combined Within the local control system 36 to
`calculate the magnitude and direction of the desired total
`force 46 that the global control system 22 has instructed the
`local control system to apply to the streamer 12. The global
`control system 22 could alternatively provide the magnitude
`and direction of the desired total force 46 to the local control
`system 36 instead of the desired horizontal force 42 and the
`desired vertical force 44.
`While the desired horizontal force 42 and the desired
`vertical force 44 are preferably calculated by the global
`control system 22, it is also possible for the local control
`system 36 in the inventive control system to calculate one or
`both of these forces using a localized displacement/force
`conversion program. This type of localized conversion pro
`gram may, for instance, use a look-up table or conversion
`routine that associates certain magnitudes and directions of
`vertical or horizontal displacements With certain magnitudes
`and directions of changes in the vertical or horizontal forces
`required. Using this type of embodiment, the global control
`system 22 can transmit location information to the local
`control system 36 instead of force information. Instead of
`the desired vertical force 44, the global control system 22
`can transmit a desired vertical depth and the local control
`system 36 can calculate the magnitude and direction of the
`deviation betWeen the desired depth and the actual depth.
`Similarly, instead of transmitting a desired horizontal force
`42, the global control system 22 can transmit the magnitude
`and direction of the displacement betWeen the actual hori
`zontal position and the desired horizontal position of the bird
`18. One advantage to this alternative type of system is that
`the required vertical force can be rapidly updated as the local
`control system receives updated depth information from the
`integrated pressure sensor. Other advantages of this type of
`alternative system include reducing communication traf?c
`on the communication line 24 and simplifying the program
`ming needed to convert the measured vertical and/or hori
`zontal displacements into corresponding forces to be applied
`by the birds 18.
`When the local control system 36 has a neW desired
`horizontal force 42 and desired vertical force 44 to be
`applied, the Wings 28 Will typically not be in the proper
`orientation to provide the direction of the desired total force
`46 required. As can be seen in FIG. 3, the Wings 28 introduce
`a force into the streamer 12 along an axis perpendicular to
`the rotational axis of the Wings 28 and perpendicular to the
`streamer. This force axis 48 is typically not properly aligned
`With the desired total force 46 When neW desired horizontal
`and vertical force values are received from the global control
`system 22 or determined by the local control system 36 and
`
`PGS v. WESTERNGECO (IPR2014-00689)
`WESTERNGECO Exhibit 2043, pg. 8
`
`

`
`US 7,080,607 B2
`
`7
`some rotation of the bird 18 is required before the bird can
`produce this desired total force 46. As can be seen, the force
`axis 48 is directly related to the bird roll angle, designated
`in FIG. 3 as q).
`The local control system 36 optimizes the control process
`by projecting the desired total force 46 onto the force axis 48
`(i.e. multiplying the magnitude of the desired total force by
`the cosine of the deviation angle 50) to produce an inter
`mediate desired force 52 and then adjusting the Wing com
`mon angle ot (the angle of the Wings With respect to the bird
`body 30, or the average angle if there is a non-Zero splay
`angle) to produce this magnitude of force along the force
`axis. The calculated desired common Wing angle is com
`pared to the current common Wing angle to calculate a
`desired change in the common Wing angle and the Wing
`motors 34 are actuated to produce this desired change in the
`orientation of the Wings.
`A splay angle is then introduced into the Wings 28 to
`produce a rotational movement in the bird body 30 (i.e. to
`rotate the force axis 48 to be aligned With the desired total
`force 46). The splay angle is the difference betWeen the
`angles of the Wings 28 With respect to the bird body 30. As
`the bird body 30 rotates and the force axis 48 becomes more
`closely aligned With the desired total force 46, the bird roll
`angle and the bird roll angular velocity are monitored, the
`splay angle is incrementally reduced, and the common angle
`is incrementally increased until the intermediate desired
`force 52 is in the same direction and of the same magnitude
`as the desired total force. The local control system 36
`carefully regulates the splay angle to ensure that the
`streamer is stable in roll degree of freedom. The calculated
`common Wing angle and the splay angle are also regulated
`by the local control system 36 to prevent the Wings 28 from
`stalling and to ensure that the splay angle is prioritized.
`When using the type of birds described in our published
`PCT lntemational Application No. WO 98/28636, Where the
`bird 18 is rigidly attached, and cannot rotate With respect, to
`the streamer 12, it is important for the control system to take
`the streamer tWist into account. If this is not taken into
`account, the bird 18 can use all of its available splay angle
`to counter the tWist in the streamer 12. The bird 18 Will then
`be unable to reach the demanded roll angle and the generated
`force Will decrease. The inventive control system incorpo
`rates tWo functions for addressing this situation; the anti
`tWist function and the untWist function.
`In the anti-tWist function, the streamer tWist is estimated
`by Weightfunction ?ltering the splay angle measurements
`instead of simply averaging the splay angle measurements to
`improve the bandWidth of the estimation. The anti-tWist
`function enga