SE1350226A1 - Propeller with adjustable for steering of vessels and control method for propeller with adjustable pitch - Google Patents

Abstract

32 ABSTRACT An object of the present invention is to improve thepropeiier efficiency as much as possibie, so as to enabie energysaving operation to be performed. A controiiabie pitch propeiiercontroi ship inciudes a controiiabie pitch propeiier, a hydrauiic unit13 provided in a boss of the controiiabie pitch propeiier incorrespondence with each vane 14 of the controiiabie pitchpropeiier, so as to independentiy change the vane angie of eachvane 14, a vane angie Command section 11 that obtains a vanaangie ciose to a cavitation occurrence iimit according to the waterdepth of the vane 14 and outputs the obtained vane angie as avane angie target vaiue "ao" of the vana 14, and a hydrauiic unitcontroi section 12 that receives the vane angie target vaiue "aa"from the vane angie Command section 11 and controis thehydrauiic unit 13 so that the vana angie of the vane 14 becomesthe vana angie target vaiue "ao".

Description

2G 1 CÛNTRGLLABLE PITCH PROPELLER CQNTROL SHIP ANDCGNTRCLLABLE PITCH PRÜPELLER CÛNTRCL METHOD BACKGRQUNB OF THE INVENTIQNFieid of the Invention[OOGI] The present invention reiates to a controiiabie pitchpropeiier controi ship and a controiiabie pitch propeiier controimethod. More particuiariy, the present invention reiates to acontroiiabie pitch propeiier controi ship provided with a controiiabiepitch propeiier in which the vane angie of each vane can beindependentiy controiied, and aiso reiates to a method forcontroiiing the controiiabie pitch propeiier.

Reiated Art[N62] Conventionaiiy, there has been known a ship provided with acontroiiabie pitch propeiier (CPP; hereinafter, aiso simpiy referredto as a propeiier) in which the attachment angie (hereinafter,referred to as the vane angie) of each vane can be changed byremote controi during operation of the propeiier (see PatentLiterature 1, for exampie). [ÛOÛB] In this conventionai controiiabie pitch propeiier, aii of thevane angies of the piuraiity of vanes are equaiiy changed.[0994] Usuaiiy, as the vane angie of a propeiier is increased, thedistance by which a ship proceeds per one rotation of the propeiieris increased, and hence a iarger thrust can be obtained. however,when the vane angie is too iarge, the cavitation phenomenonoccurs, causing probiems of vibration, noise, and corrosion by thecavitation-induced shock waves striking the surface of thepropeiier.

[C565] Therefore, in the conventionai controiiabie pitch propeiier, the vane angie is controiied to become as iarge as possibie within a 29 39 2 range in which the cavitation does not occur.

Citation ListPatent Literature[9996] _ Patent Literature 1: Nationai Publication of InternationaiPatent Appiication No. 2991-519289 SUMMARY OF THE ïNVENTIÛN[9997] Generaiiy, when the rotation speed and thrust of a propeiierare fixed, the cavitation is iess iikeiy to occur as the water depth isincreased and, on the contrary, the cavitation is more iiiceiy tooccur as the water depth is decreased.

[9998] In the case of a iarge ship, since the diameter of thepropeiier is iarge, the water depth at which the vane is present isgreatiy different between the time when the vane of the propeiierpasses through the area of the srnaiiest water depth and the timewhen the vane of the propeiier passes through the area of theiargest water depth, and hence the vane angie which is set as iargeas possibie within a range not causing cavitation aiso becomesdifferent greatiy according to the water depth of the vane.

[9999] iiowever, in the conventionai controiiabie pitch propeiier, thevane angie of each vane is uniforrniy controiied (totai minimizationcontroi), and hence the vane angie of each vane cannot becontroiied to the most efficient angie according to the water depth.Therefore, there is a probiem that the propeiier efficiency cannotbe sufficientiy improved as a whoie, that is, the conventionaicontroiiabie pitch propeiier must be used at the sacrifice ofpropeiier efficiency.

Accordingiy, an object of the present invention is to providea controiiabie pitch propeiier controi ship and a controiiabie pitchpropeiier controi method, each of which can improve propeiierefficiency as high as possibie.

[6010] According to an aspect of the present invention, there isprovided a controiiabie pitch propeiier controi ship inciuding: acontroiiahie pitch propeiier; a hydrauiic unit provided in a boss ofthe controiiapie pitch propeiier in correspondence with each of thevanes of the controiiahie pitch propeiier, so as to independentiychange the vane angie of each of the vanes; a vane angieCommand section that ohtains a vane angle ciose to a cavitationoccurrence iimit according to the water depth of the vane, andoutputs the obtained vane angie as a vane angie target vaiue ofthe vana; and a hydrauiic unit controi section that receives thevane angie target vaiue from the vane angie cornmand section andcontrols the hydrauiic unit so that the vane angie of the vanebecomes the vane angie target vaiue. [Ûoll] According to another aspect of the present invention, thereis provided a controiiabie pitch propeiier controi method inciuding:receiving a water depth (d) at which a predetermined vane of thecontroiiahie pitch propeiier is present, and then caicuiating forwardthrough-water speed (VA) of the vane at the water depth (d) fromwake distripution data and cruising speed (V) of a ship; caicuiatingan advance coefficient (J) of the vane at the water depth (d) fromthe number of revoiutions (n) and the diameter (D) of thecontroiiabie pitch propeiier, and the forward through-water speed(VA) of the vane; caicuiating a thrust coefficient (KW) at a pitch (P)seiected from a predetermined range, by using the advancecoefficient (J), and K-i--J data used for obtaining a thrust coefficient(KT) from the advance coefficient (J); caicuiating a thrust (TD) atthe water depth (d) and at the pitch (P) by using the thrustcoefficient (Kr-P), the water density (p), the number of revoiutions(n) and the diameter (D) of the controiiabie pitch propeiier;caicuiating a thrust ioad (T/Ap) of the vane from the projection area(AD) of the vane ai: the pitch (P), and the thrust (Tpfi caicuiatingcircumferentiai speed (nDN) of the vane; determining whether ornot the vana at the water depth (d) and at the pitch (P) causescavitation, by using the circumferentiai speed (i-ciïâhi), the thrust 1G 4 ioad (TIAP), and aiiowahie iimit data rapresenting, for each waterdapth, the iimit of thrust ioad with respect to tha circumferentiaispeed; and idantifying a pitch (P0) ciose to the aiiowabie limit hydetermining whether or not cavitation is caused hy the vana ateach of a piuraiity of pitchas in the predetarmined range, andconverting the pitch (P0) into a vana angie to obtain the vana angieas a vana angie target vaiua (an), and then adjusting the vanaangie of the vana to the vana angie target vaiua.

[0012] In the present invention, the hydrauiic unit thatindependentiy changes the vana angie of each of the vanes of thecontroiiabie pitch propeiier, the vana angie Command section thatoutputs, as a vana angia target vaiue, a vana angie ciose to acavitation occurranca iimit corresponding to the water depth atwhich the vana is present, and the hydrauiic unit controi sectionthat controis the hydrauiic unit so as to enabie the vana angia ofeach of the vanes to become the vana angie target vaiue, areprovided. Therapy, the vana angie of each of the vanes of thecontroiiabie pitch propeiier can be set to a vana angie ciose to thecavitation occurrence iimit corresponding to the water depth of thevana, and hence the propaiier efficiency can ha improved as muchas possihie.

BRIEF DESCRIPTION OF THE DRAWINGS[GG13] [Figure 1] Figure 1 is a view showing a schematicconfiguration of a controiiabie pitch propaiier controi ship accordingto an embodiment of the present invention.

[Figure 2] Figure 2 is a control biock diagram for one vanain the controiiaioie pitch propaiier controi ship according to the i amhodiment of the present invention.

[Figure 3] Figure 3 is a hiock diagram of a vana angiacommand section according to the embodiment of the presentinvention.

[Figure 4] Figure 4(a) is a view for expiaining a way ofohtaining the shaft depth I, and Figure 4(h) is a view for expiaining 3Û 5 a way of obtaining the water depth of the vane.

[Figure 5] Figure 5 is a view showing an exampie of wakedistribution data 31.

[Figure 6] Figure 6 is a view showing an exarnpie of KT-jidata 32.

[Figure 7] Figure 7 is a view showing an exampie ofaiiowabie iirnit data 33.

[Figure 8A] Figure 8A is a fiowchart showing a controiiabiepitch propeiier controi method according to an embodiment of thepresent invention.

[Figure 85] Figure 85 is a fiowchart foiiowing the fiowchartof Figure 8A and showing the controiiabie pitch propeiier controimethod according to the embodirnent of the present invention.

BETAïLED~ ÜESQRIFTIÛFN GF THE INVÉNTIÜN[Gold] in the foiiowing, embodiments according to the presentinvention wiii be described with reference to the accompanyingdrawings.

[0015] Figure 1 is a view showing a schernatic configuration of acontroiiabie pitch propeiier coritroi ship according to anembodiment of the present invention.

[N16] As shown in Figure 1, a controiiabie pitch propeiier 1 isconnected to a ship propuision engine 3 via a propeiier shaft 2 andis configured to be rotatabiy driven by the ship propuision engine3.

[0017] in the present embodiment, the controiiabie pitch propeiier1 has four vanes 14, and the pedestai of each of the vanes 14 isrotatabiv attached to a centrai boss 4 of the controiiabie pitchpropeiier 1 so that the vane angie of each of the vanes 14 can bechanged. Note that the number of vanes 14 is not iimited to four.In the inside of the boss 4, a hydrauiic unit 13 is provided for eachvane 14 so as to independentiy change the vane angie of each of 2G 6 the vanes 14. For exarnpie, as shown in Figure 1, it can beconfigured such that the proximai end of the vane 14 is attached tothe rotatabie pedestai, and such that the hydrauiic unit 13 drives avane angie centroi gear by a piston to thereby enabie the vane 14to be rotatabiy driven in the iiiustrated direction R.

[0918] The hydrauiic unit 13 is controiied by a hydrauiic unit controisection 12. [0O1Q] The hydrauiic unit contrei section 12 receives a vane angietarget vaiue as a controi target from a varie angie Commandsection 11, and eutputs, to the hydrauiic unit 13, the varse angietarget vaiue together with drive eiectric power. [ÛGZG] The eiectric power for driving the hydrauiic unit 13 istransmitted from a fixed terminai connected to a power source 5 toa rotating terminai via, for exampie, a siip ring ö, and is thentransmitted to each of the hydrauiic unit controi sections 12, so asto be suppiied to the hydrauiic unit 13. [0G21] Each of the vane angie cornmand section 11 and thehydrauiic unit controi section 12 is provided with a wireiess device,and the vane angie target vaiue can be wireiessiy transrnitted tothe hydrauiic unit controi section 12. Note that, of course, thevane angie Command section 11 and the hydrauiic unit centre!section 12 may be connected to each other by wire. [ÛQZZ] Figure 2 is a controi biock diagram for one vane in thecontroiiabie pitch propeiier controi ship according to theernbodiment of the present invention.

[N23] As shown in Figure 2, the contreiiabie pitch propeiier controiship according to the present embodiment inciudes the vane angiecommand section 11, the hydrauiic unit controi section 12, thehydrauiic unit 13, and the vane 14. The controiiabie pitchpropeiier 1 (not shown) has the vanes 14, and the hydrauiic unit 'ED 2G 3G 7 controi section 12 and the hydrauiic unit 13 are provided for eachvana 14.[DD24] The vana angie command section 11 is provided in acomputer (CPP controi computer) for controiiing the controiiabiepitch propeiier. According to the rotation angie (water depth) ofthe vana 14, the vana angie Command section 11 caicuiates, as wiiibe described in detaii beiovv, a iimit vana angie not causingcavitation, and outputs, as a vana angie target vaiue (ag), thecaicuiated iimit vana angie to the hydrauiic unit controi section 12.[DDZS] The hydrauiic unit controi section 12 inciudes a PID controisection 12a and a driver 12b, and controis the hydrauiic unit 13 sothat the vana angie of the vana 14 becomes the vana angie targetvaiue inputted by the vana angie command section 11. By use ofthe vana angie target vaiue (ag) caicuiated by the vana angiecommand section 11, and an actuaiiy measured vana angie (actuaivane angie vaiue ((1)) of the vana 14, the PID controi section 12aperforms controi (for exampie, PID controi) so that the actuai vanaangie vaiue (a) becomes eouai to the vana angie target vaiue (de).The driver 12b controis the hydrauiic unit 13 on the basis of a vanaangie controi signai outputted by the PID controi section 12a.[6626] The hydrauiic unit 13 is provided in the boss of thecontroiiabie pitch propeiier, and changes the vana angle of the vana14 by driving the vana angie controi gear of the vana 14. Thehydrauiic unit 13 is provided for each vana, and hence the vanaangie of each of the propeiier can be independentiy controiied. Asthe hydrauiic unit 13, for exampie, a DDVC (Direct Drive VoiumeControi) hydrauiic unit manufactured by Daiichi Denki Corporationcan be used. The DDVC hydrauiic unit is configured by integratinga gear pump (reversibie hydrauiic pump), a servo motor for drivingthe gear pump, a hydrauiic cyiinder directiy connected to the inietand outiet of the gear pump, and an oii tank for suppiying oii to thegear pump. The piston in the hydrauiic cyiinder is connected tothe vana angie controi gear of the vane, and is controiied to a 3G 8 desired position by rotation of the servo motor. The gear pumpneeds to be operated oniy when the piston needs to be operated,and hence the hydrauiic unit 13 has an advantage that powerconsumption is smaii and aiso the amount of heat generation issmaii.[6027] Further, the DDVC hydrauiic unit is smaii and space-saying,and hence can be incorporated in the boss of the propeiier. Forthis reason, it is not necessary to feed oii from the inside of theship to the inside of the boss through the propeiier shaft as in theconventionai case, and hence the structure of the propeiier shaftcan be simpiified. Further, the inside of the boss of the propeiiercan be fiiied with oii, and hence the pressure resistance of the bosscan aiso be increased. [ÛGZS] Note that, when the above-described BDVC hydrauiic unit isused as the hydrauiic unit 13, the actuai vane angie vaiue can beknown from the position of the piston of the hydrauiic cyiinder(incidentaiiy, a sensor for monitoring needs to be separated from asensor for controi according to the ruies and reguiation of NK(Nippon Kaiji Kyokaii).

[GÛZQ] Further, as described above, eiectric power can be suppiiedto the hydrauiic unit 13 via the siip ring provided at the propeiiershaft.

[9636] The vane 14 is one of the piuraiity of vanes provided at thecontroiiabie pitch propeiier. The rotation angie (o) of the vane 14means an angie at which the iongitudinai axis iine of the vane 14 isinciined from the verticai upward direction when seen from thefront of the controiiabie pitch propeiier 1. The rotation angie (e) ofthe vane 14 is measured by, for exampie, a magnetic sensor and istransmitted, as a vane position signai, to the vane angie commandsection 11 (CPP controi computer) by wire or wireiess. The vaneangie of the vane 14 is adjusted by the hydrauiic unit 13 drivingthe vane angle controi gear of the vane 14.

[0031] Next, the detaiis of the vane angie command section 11 wiiibe described. Figure 3 shows a biock diagram of the vane angiecommand section 11.

[0032] As shown in Figure 3, the vane angie Command section 11inciudes shaft depth input means 20, vane water-depth caicuiatingmeans 21, water-depth-reiated vane advance speed caicuiatingmeans 22, vane advance coefficient caicuiating means 23, thrustcoefficient caicuiating means 24, thrust caicuiating means 25, vaneprojection area input means 26, thrust ioad caicuiating means 27,circumferentiai speed caicuiating means 28, determining means 29,controi means 30, wake distribution data 31, KT-J data 32, andaiiowabie iimit data 33.

[0033] In the foiiowing, each of the components of the vane anglecommand section 11 wiii be described.[0034] The shaft depth input means 20 is means for inputting theshaft depth of the controiiabie pitch propeiier into the vanewater-depth caicuiating means 21. i-iere, the shaft depth is theiength from the water surface to the centrai axis of the boss of thecoritroiiabie pitch propeiier. As shown in Figure 4(a), the shaftdepth can be obtained by the foiiowing expression using the draftand the height from the keei bottom surface to the propeiier shaft.[Expression 1] .Mafa m Here, "t" represents the shaft depth, "da" represents thedraft, and "h" represents the height from the i

[0035] Note that the shaft depth input means 20 needs oniy toperform input of the shaft depth of the controiiabie pitch propeiier.Qf course, without performing the above-described caicuiation, theshaft depth input means 20 may read the shaft depth from a shaft 2G 3G ”ss 1G depth tahie storing each shaft depth in correspondence with eachdraft, and then perform input of the read shaft depth.[Üüšê] Since the water depth at which the vana 14 is present ischanged according to the rotation angie "e", the vana watar-depthcaicuiating means 21 is means to caicuiate the water depth atwhich the vane 14 of interest is present.

[C037] As can be seen from Figure 4(h), the vana water-depthcaicuiating means 21 caicuiates the water depth of the vana 14(controi target vana) by the foiiowing expression using the shaftdepth inputted from the shaft depth input means 20, and therotation angie and iength of the vana 14.

[Expression 2] áašeíâposå i -F V D! (2) i-iare, "d" represents the water depth of the vana, "t"represents the shaft depth, "L" represents the iength of the vana,and "e" represents the rotation angie of the vana. Note thatcavitation is generated from the vana tip, and hence the vanaiength "L" may he set as the iength (propeiier radius) from thecenter of the propaiier to the vana tip.

[0638] instead of caicuiating the water depth of the vana by usingthe above-described exprassion, the vana water-dapth caicuiatingmeans 21 may, of course, obtain the water depth at which the vanais present, from, for axampie, a tahie storing the water depth ofthe vana in corraspondence with the rotation angie of the vana.Note that it is assumed that the operation to obtain the water depth from the tabia is inciuded in "caicuiation" in a hroad meaning.

Aiso, this is simiiariv appiiad to the case of the other means of thepresent invention described beiow.[OGBQ] Tha water-depth-reiated vana advance speed caicuiatingmeans 22 is means to caicuiate forward through-water speed ofthe vana at the time when the vana is present at a specific water 19 2G 11 depth. The forward through-water speed of the vane is caicuiatedbecause wakes are present around the propeiier, and hence theactuai forward through-water speed of the vane is different fromthe cruising speed "v" of the ship in dependence upon the positionof the propeiier.

[GG4G] The water-depth-reiated vane advance speed caicuiatingmeans 22 first caicuiates a wake coefficient from the water depthof the vane 14 caicuiated by the vane water-depth caicuiatingmeans 21, and the wake distribution data 31. That is, thewater-depth-reiated vane advance speed caicuiating means 22obtains the wake coefficient "w" at the water depth "d" of the vane14 with reference to the wake distribution data 31 obtained in apreiiminary test. Figure 5 is a view showing an exampie of wakedistribution data 31 obtained by a test performed beforehand byusing an actuai ship. As can be seen from Figure S, the wakecoefficient "w" is 6.525 at the time when the water depth "d" of thevane corresponds to the iiiustrated position.

[QO41] Then, the water-depth-reiated vane advance speedcaicuiating means 22 caicuiates the advance speed of the vane 14at the water depth "d" by the foiiowing expression using the wakecoefficient of the vane 14 at the water depth "d", and the cruisingspeed of the controiiabie pitch propeiier ship.

[Expression 3] k; == (i «- WW t! G ß å (33 Here, "VA" represents the advance speed, "w" represents the wake coefficient, and "V" represents the cruising speed of the - ship.[QG42] Note that the wake distribution data 31 may aiso betabuiated so that a forward through-water speed of the vane canbe acquired for a predetermined rotation angie of the vane.

[N43]The vane advance coefficient caicuiating means 23 is means 1G 39 12 to caicuiate a vane advance coefficient representing a reiationshipbetween the forward through-water speed "VA" of the vana, thenumber of revoiutions "n" and the diameter "D" of the propeiier.[Does] The vahe advance coefficient caicuiating means 23caicuiates an advance coefficient "Ii" of the vane 14 at the waterdepth "d" by the foiiowing expression using the number ofrevoiutions "n", the diameter "D" of the controiiabie pitch propeiier,and the forward through-water speed "VA" of the vana, whichspeed "VA" is caicuiated by the watendepth-reiated vane advancespeed caicuiating means 22.

[Expression 4] i'*kl-få o x i: v: at?Here, "J" represents the advance constant (advance coefficient), "VA" represents the advance speed, "n" represents thenumber of revoiutions of the propeiier, and "D" represents thediameter of the propeiier. Note that "n" represents the number ofrevoiutions per second.

[OG4-5] The thrust coefficient caicuiating means 24 is means tocaicuiate a thrust coefficient "KT" which represents a relationshipbetween a thrust "T" of the propeiier, the water density "p", thenumber of revoiutions "n" and the diameter "D" of the propeiier.[9046] Since the thrust coefficient is changed according to the pitch"P" (vana angie) or the pitch ratio "p" (= P/D), the thrustcoefficient caicuiating means 24 refers to the KT-J data 32representing the reiationship between the advance coefficient "J"and the thrust coefficient "KT", by using the pitch "P" or the pitchratio "p" as a parameter, and thereby obtains a thrust coefficientfor a predetermined pitch "P", which coefficient corresponds to theadvance coefficient caicuiated by the vane advance coefficientcaicuiating means 23. 'iQ 3G 13

[0647] Note that a pitch in a predetermined range is seiected as thepredetermined pitch "P". This predetermined range is suitabiyseiected according to the type of ship. [0Ü48] Figure 6 shows an exampie of the KT-J data 32 ohtained in apreiiminary test. As can he seen from Figure 6, for exampie, whena vaiue of 1.6 is seiected as the pitch ratio "p", and when theadvance coefficient "J" caicuiated hy the vane advance coefficientcaicuiating means 23 is (Lä, the thrust coefficient "KW"corresponding to this advance coefficient is 9.4.

[S049] The thrust caicuiating means 25 is means to caicuiate athrust "T" of the vane.[QQSG] The thrust caicuiating means 25 caicuiates a thrust "TP" ofthe vane 14 at a predetermined pitch "P" hy the foiiowingexpression using the thrust coefficient "K-i-p", the water density "p", the number of revoiutions "n" and the diameter "S" of thecontroiiabie pitch propeiier.[Expression 5] Tpfiitwwiwifip* ~~ Here, "TP" represents the thrust of the vane 14 at thepredetermined pitch, "iii-fp" represents the thrust coefficient of thevane 14 at the predetermined pitch, "n" represents the number ofrevoiutions of the propeiier, and "D" represents the diameter of thepropeiier.

[S651] The vane projection area input means 25 is means tocaicuiate a projection area of the vane, which area is changedaccording to the vane angie.

[GGSE] The vane projection area input means 25 inputs a projectionarea (Ap) of the vane 14 at a predetermined pitch "P" into thethrust ioad caicuiating means 27. The vane projection area input 14 means 26 obtains a projection area of the vana at a pradetarminedpitch "P" by referring, for exampie, to data (tabie) obtained in apraiiminary test and representing the reiationship between thepitch and the projection area of the vana.

[0053] Tha thrust ioad caicuiating means 27 is means to obtain athrust per projection area of the vana.[0054] The thrust load caicuiating means 2? caicuiates a thrustioad of the vana 14 at a predetermined pitch "P" by the foiiowingaxprassion using the thrust at the predetermined pitch "P" of thevana 14, which thrust is caicuiated by the thrust caicuiating means25, and the projection area of the vana 14 at: the pradatarminedpitch "P", which area is inputted by the vana projection area inputmeans 26.

[Expression 5] Treaty/A, ~~ (a) Here, "TL" rapresents the thrust ioad at the pradetarminedpitch, "Ta" represants the thrust of the vana 14 at thepredeterrnined pitch, and "AD" represents the projection area of thevana 14 at the predetermined pitch.

[0055] The circurnferantiai speed caicuiating means 28 caicuiatas acircumferentiai speed of the vana 14 by the foiiowing expressionusing the number of ravoiutions and the diameter of thecontroiiabiepitch propeiiar.

[Exprassion 7] Vflfiazfiídfiñüstïfiïl (T) Hera, "VC" reprasents the circumferentiai speed, "D"represents the diameter of the propeiier, and "N" represents thenumber of revoiutions par minute (= 50n).

[0055] Of course, the circurnferentiai speed of the vana can aiso be tabuiated in correspondence with the number of revoiutions. [00573 The determining means 29 is means to determine whetheror not a predetermined vane angie causes cavitation at apredetermined water depth.

[0058] The determining means 20 determines whether or not thevane 14 at a predetermined pitch "P" causes cavitation at a waterdepth "d", by using the aiiowabie iimit data 33 representing, foreach Water depth, a thrust ioad iimit with respect to acircumferentiai speed, the thrust ioad at the predeterrnined pitch"P", which thrust ioad is caicuiated by the thrust ioad caicuiatingmeans 27, and the circurnferentiai speed of the vane 14, whichcircumferentiai speed is caicuiated by the circumferentiai speedcaicuiating means 28.

[0059] Figure 7 shows an exampie of the aiiowabie iimit data 33obtained in a preiiminary test. When the thrust ioadcorresponding to the circumferentiai speed is iarger than the iimitvaiue represented by the aiiowabie iimit data 33, cavitation iscaused. Therefore, as can be seen from Figure 7, for exampie,when the water depth of the vane 14 is 7 [m], and when thecircumferentiai speed is 3,000 [rn/minutei, the determining means29 determines that cavitation is caused when the thrust ioad(Tp/Ap) is iarger than 1.3.

[0060] The controi means 30 controis the thrust coefficientcaicuiating means 24, the thrust caicuiating means 25, the thrustioad caicuiating means 27,, and the determining means 29, andidentifies a pitch "P0" (pitch ciose to a cavitation occurrence iimit)ciose to the aiiowabie limit at the water depth "d" among a piuraiityof pitches in the predetermined range. Preferabiy, the controimeans 30 identifies a pitch ciosest to the cavitation occurrenceiimit. Then, the controi means 30 converts the identified pitch intoa vane angie, and outputs the vane angle as a vane angie targetvaiue (oo). Note that the controi means 30 converts the identifiedpitch into a vane angie by using the foiiowing expression. 16 [Expression 8] (8) i-iere, ”ag” represents the vane angie (vana angie targetvaiue), "P9" represents the identified pitch, and "r" represents thepropeiier radius.

[N61] In the above-described configuration, the vane angieCommand section 11 outputs, as a vane angie target vaiue, a vaneangie ciose to the cavitation occurrence iimit to the hydrauiic unitcontroi section 12 according to the water depth (position) of thevane 14, which is the vane to he controiied. Then, the vane angieof the vane 14 is adjusted to the vane angie target vaiue hy thehydrauiic unit controi section 12 and the hydrauiic unit 13. [(1062] The vane angie of each of the vanes of the controiiahie pitchpropeiier is independentiy controiied to the vane angie target vaiueobtained hy the vane angie Command section corresponding toeach of the vanes. Therapy, the controiiahie pitch propeiier controiship according to the present emhodin-*ient can improve thepropeiier efficiency and perform energy saying operation ascompared with the conventionai controiiahie pitch propeiier controiship.

[N63] Note that in the ahove description, the piuraiity of vaneangie cornmand sections provided for the respective vanes areoperated in paraiiei with each other, so as to output vane angietarget vaiues of the respective vanes, hut the present emhodimentis not iimited to this. That is, it rnay aiso he configured such thatoniy one vane angie comniand section is provided to ohtain vanaangie target vaiues for aii the vanes of the propeiier. In this case,the vane angie command section rnay sirnuitaneousiy ohtain thevana angie target vaiue of each of the vanes hy paraiiei processing,or rnay successiveiy ohtain the vane angie target vaiue of each ofthe vanes hy seriai processing. 17

[0064] Further, in the above-description, the vane angie commandsection 11. has the wake distribution data 31, the KT-J data 32, andthe aiiowabie iimit data 33, but the present embodiment is notiirnited to this. That is, it may aiso be configured such that thesekinds of data are stored in an externa! storage device (such as amemory) which can be accessed by the vane angie commandsection 11, and such that the vana angie Command section 11suitabiy refers to the data stored in the externai storage device.[0065] Further, the form of the above-described various data (thewake distribution data 31, the Kei data 32, the aiiowabie iimit data33) may be data point seguences or may be poiynorniaisrespectiveiy obtained by performing poiynomiai approximation ofthe data point sequences. In the former case, a desired vaiue isobtained by using a data reference method. in the iatter case, forexampie, when a thrust coefficient "KT" is obtained, a thrustcoefficient "KT" with respect to a predetermined pitch "P" and to anadvance coefficient "J" may be obtained by using, as the KT-J data32, a poiynomiai (for exampie, the foiiowing expression (9))obtained by the poiynomiai approximation.

[Expression 9] X, mer* mi* +a§+(o:isii,s)p . . . . (a) Here, "KT" represents the thrust coefficient, "a", "b" and "c"represent constants, "J" represents the advance coefficient, and "p"represents the pitch ratio.[0066] Next, a controiiabie pitch propeiier control method accordingto an embodiment of the present invention wiii be described withreference to a fiowchart shown in Figure 8A and Figure 85.

[0067] First, a water depth "d" of the vane is caicuiated by usingthe shaft depth "I" of the controiiabie pitch propeiier, the rotationangie "a" of the vana, and the iength "L" of the vane (step S101). 18

[0058] Specificaiiy, a water depth of the vane is caicuiated by usingthe above-described expression (2). As the rotation angie(position) of the vana, a vaiue measured by a magnetic sensor, orthe iike, is used. Further, as the depth "1", a vaiue caicuiated, forexampie, by using the above-described expression (1) is used.[0069] Next, a wake coefficient "w" at the water depth caicuiated instep S101 is obtained from the water depth of the vane and thewake distribution data (step S102).

[0070] Specificaiiy, a wake coefficient at the water depth caicuiatedin step S101 is obtained, for exampie, with reference to the wakedistribution data as shown in Figure 5.

[0071] Next, an advance speed "VA" of the vane at the water depthcaicuiated in step S101 is caicuiated from the wake coefficient "w"obtained in step S102 and the cruising speed "V" of the ship (stepS103).

[0072] Specificaiiy, an advance speed "VA" is caicuiated by usingthe above-described expression (3).

[0073] Next, an advance coefficient "J" at the water depthcaicuiated in step S101 is caicuiated from the number ofrevoiutions "n" and the diameter "D" of the controiiabie pitchpropeiier, and the advance speed "VA" caicuiated in step S103 (stepS104).

[0074] Specificaiiy, an advance coefficient "J" is caicuiated by usingthe above-described expression (4).

[0075] Next, a thrust coefficient "KW" at a pitch "P" seiected from apredetermined range is caicuiated from the data (KT-J data)representing the reiationship between the advance coefficient "J"and the thrust coefficient "KT" by using the pitch (pitch ratio) as a 1G 3G 19 pararneter, and frorn the advance coefficient "J" caicuiated in stepS104 (step SIQS).[GWS] Specificaiiy, as described with reference to Figure 6, apredetermined pitch "P" is seiected from the predetermined range,and a thrust coefficient for the pitch "P" is caicuiated by using thereiationship between the advance constant and the thrustcoefficient for the pitch "P". Note that the range (predeterminedrange) from which the pitch is seiected is suitabiy seiectedaccording to the type of ship. [ÛÛ77] Next, a thrust "TD" at the predetermined pitch "P" iscaicuiated by using the thrust coefficient "K-rp" caicuiated in stepS195, the water density "p", the nurnber of revoiutions "n" of thepropeiier, and the diameter "D" of the propeiier (step S106).

[GWS] Specificaiiy, a thrust "Tp" at the water depth "d" caicuiatedin step S191 and at the predeterrnined pitch "P" is caicuiated byusing the above-described expression (S).

[0079] Next, a thrust ioad "T/Ap" of the vane is caicuiated from the projection area "Ap" of the vane at the predeterrnined pitch "P", and the thrust "Tp" caicuiated in step Síüö (step S107).Specificaiiy, the thrust ioad "T/Ap" is caicuiated by theabove-described expression (6).[0980] Next, a circumferentiai speed "nDN" of the vane is caicuiated (step S198). Specificaiiy, a circumferentiai speed "riüN"of the vane is caicuiated by the above-described expression (7).[N81] Next, whether or not the vane at the water depth caicuiatedin step Sim and at the pitch "P" seiected in step S165 causescavitation is deterrnined by using the thrust ioad caicuiated in stepS107, the circumferentiai speed caicuiated in step S138, and theaiiowabie iiniit data representing, for each water depth, the iimit ofthrust ioad with respect to the circumferentiai speed (step Siba). '10

[0082] Specificaiiy, as described above with reference to Figure 7, aiimit vaiue (iimit thrust Head) of the thrust Head with respect to thecircumferentiai speed caicuiated in step S108 is obtained byreferring to the aiiewabie iimit data at the water depth caicuiated instep S101. Then, the iimit thrust ioad is compared with the thrustHead caicuiated in step S107. When the thrust ioad caicuiated instep S107 is iarger than the iimit thrust Head, it is determined thatcavitation is caused. On the other hand, when the thrust Head isthe iimit thrust Head or Hass, it is determined that cavitation is notcaused.

[0083] Next, it is checked whether or not a pitch "P0" ciose to theaiiowabie iimit has been identified among pitches within thepredetermined range. Preferabiy, it is checked whether or not apitch ciosest to the aiiowabie iimit has been identified amongpitches within the predetermined range. When the pitch "Pa" hasaiready been identified, the process proceeds to step S111. Gnthe other hand, when the pitch "PG" has not been identified, theprocess returns to step S105. Then, the other pitch within thepredetermined range is seiected, and the processing in step S105to step S109 is performed (step S110).

[0084] Next, the identified pitch "P0" is converted into a vana angie,so as to set the vane angie as a vane angie target vaiue "dQ", andthen, the vane angie of the vane is adjusted to the vane angietarget vaiue "do" (step S111). Note that the identified pitch "Pa" isconverted into a vana angie by the above-described expression (8).[0085] With the controiiabie pitch propeiier controi methoddescribed above, each vane angie of the vanes is controiied to avane angie ciosest to the cavitation occurrence iimit according tothe water depth (position) of the vane. When each of the vanes ofthe controiiabie pitch propeiier is controiied by the abovedescribedmethod, the propeiier efficiency can be improved, and hence theenergy saying operation can be performed as compared with the 16 26 36 21 conventionai method.[6686] For exampie, the difference between the vane angie at thetime when the vane is present at the position (e = 6°) ciosest tothe water surface, and the vane angie at the time when the vane ispresent at the position (6 == 186% farthest from the water surfaceis 3° to 8” (preferabiy 6°). When the vane angie difference is 5%the propeiier efficiency can be improved by about 16%.

[6687] Note that the foiiowing method may aiso be adopted inorder to more efficientiy perform the caicuiation of the optimumvane angie.

[6688] That is, a method may be adopted in which the vane angietarget vaiue is obtained by the above-described method for eachvane of the controiiabie pitch propeiier, or a method may aiso beadopted in which the vane angie target vaiue is obtained by theabove-described method oniy for a specific vane, and in which thevane angie target vaiue of each of the other vanes is obtained byusing the phase difference between the each of the other vanesand the specific vane. For exampie, when the propeiier has fourvanes (vane A, vane B, vane C, and vane D), a method may beadopted in which the vana angie target vaiue is obtained asdescribed above oniy for the vane A, and in which the vane angietarget vaiues for the other vanes are respectiveiy obtained by thefoiiowing expressions.

[Expression 16] ag (53 *då tfist-QÜÛ) (16) [Expression 11] et; (ål -fierå (åflt-ïâün) ~-=-«(11_}[Expression 12]abia) ma, (emerofl ma; 2G 22 Here, “oA", "ash "oc" and "os" represent vane angie targetvaiues of the vane A, the vane B, the vane C and the vane D,respectiveiy. [oooo] instead of caicuiating the pitch (vana angie) ciosest to theaiiowabie iimit for each of the rotation angies, a method may beadopted in which the pitch ciosest to the aiiowabie iimit iscaicuiated oniy for a precietermined rotation angie, and in whichthe pitch ciosest to the aiiowabie iimit for each of the other rotationangies is obtained from the pitch for the predetermined rotationangie. [(1090] For exarnpie, a method may he adopted in which, whenthe vane of the propeiier is present at the position ciosest to thewater surface (o = o°), and When the vane of the propeiier ispresent at the position farthest from the water surface (o =189%, the vane angie target vaiue is caicuiated by theabove-described method, and in which, when the vane ispresent at the other positions, the vane angie target vaiue iscaicuiated by using the foiiowing expression.[Expression 13] oioi)=e,egë-fvšå{i-oosë) ,. . _ (13) Here, "si" represents the vane angie target vaiue at "o" ==G2 and "oz" represents the vana angie target vaiue at "o" =180% [oool] Further, when the minimum vaiue of the vane angie can beknown beforehand from the specification of the controiiabie pitchpropeiier, the vaiue may he used as the vane angie target vaiue at"o" == of”. In this case, when the vane is present at positions otherthan "o" = of” and 1802 the vane angie target vaiue is caicuiated byusing the foiiowing expression.

'EQ 2G 23 [Expression 14] affwzaflf* (ï-oosåš , _ _ _ “íægaefl + i: 4) Here, "omm" represents the minimum vaiue of the vaneangie, and "ag" represents the vane angie target vaiue at ”e” =189% [OGQZ] As described above, with the present invention, each of thevanes of the controiiabie pitch propeiier is independentiy controiiedto a pitch ciosest to the aiiowabie iimit according to the waterdepth (position and rotation angie) of the vane. Therehv, theminirnization controi is performed for each vane, and hence it ispossihie to improve the propeiier efficiency and to perform energysaving operation as compared with the conventionai totaiminimization controi.

[0693] Those skiiied in the art may contempiate additionai effectsand various transformations of the present invention based on theabove description. Therefore, the aspects of the present inventionare not iirnited to the above-described embodirnents. Variousaddition, change, and partiai eiimination may be achieved within ascope of conceptuai idea and intention of the present inventionwhich are derived from the Substance specified in the ciaims and itseduivaients.

Reference Signs List[Gü94]1 Controiiabie pitch propeiier2 Propeiier shaft3 Ship propuision engine4 Boss5 Power source6 Siip ring11 Vane angie comrnand section12 Hydrauiic unit controi section 24 12a PïD controi section 12o Driver 13 i-iydrauiic unit 14 Vana 2G Snart depth input means 21 Vana water-depth caicuiating means 22 Wateaadepth-reiated vana advance speed caicuiating means 23 Vana advance coefiicient caicuiating means24 Thrust coefficient caicuiating means 25 Thrust caicuiating means 26 Vana projection area input means 27 Thrust ioad caicuiating means 28 Circumferentiai speed caicuiating means2% Determining means 30 Controi means 31 Wake distribution data 32 KT-J data 33 Aiiowaioie iimit data

Claims (14)

1. What is ciaimed is:l. A controiiabie pitch propeiier controi ship comprising: a controiiabie pitch propaiiar; a hydrauiic unit provided in a boss of the controiiabia pitchpropeiier in corraspondence of each vana of the controiiabia pitchpropaiiar, so as to indapendentiy change a vana angie of each ofthe vanes; a vana angia command section that obtains a vana angiaciose to a cavitation occurrance iimit according to a water depth ofthe vana, and outputs the obtained vana angie as a vana angietarget vaiue of the vana; and a hydrauiic unit controi section that receives the vane angiatarget vaiue from the vana angie command section and controisthe hvdrauiic unit so that tha vana angie of tha vana becomes thevana angie target vaiua.

2. Tha controiiabie pitch propaiier controi ship according tociaim i., wherein the vana angia command section inciudes: shaft depth input means that inputs a shaft depth "I" of thecontroiiabia pitch propaiier; vana water-depth caicuiating means that receives the shaftdapth "I" of the controiiabie pitch propeiier from the shaft dapthinput means, and racaives a rotation angia "a" and the iength "L" ofthe vana, so as to caicuiate a water depth "d" at which the vana ispresent; watar-dapth-reiated vana advance speed caicuiating meansthat recaivas the vana water dapth "d" caicuiated by the vanawatar-dapth caicuiating means, and a cruising speed "V" of the ship,and caicuiatas, with reference to wake distribution data, a forwardthrough~watar speed "VA" of the vana at the water dapth "d" atwhich the vana is present; vana advance coefficiant caicuiating means that raceivas thenumber of ravoiutions "n" and the diameter "D" of tha controiiabiepitch propeiier, and the forward through-water speed "VA" of thevana at the water dapth of the vana, the speed "VA" being 26 caicuiated by the water-depth-reiated vane advance speedcaicuiating means, and caicuiates an advance coefficient "J" of thevane at the water depth by the foiiowing expression (1),[Expression 1] g-å-và/np (ti here, "J" represents the advance coefficient, "VA" represents theadvance speed of the vane at the water depth of the vane, "n"represents the number of revoiutions of the controiiabie pitchpropeiier, and "D" represents the diameter of the controiiabie pitchpropeiier; thrust coefficient caicuiating means that receives theadvance coefficient "J" of the vana at the water depth of the vane,the coefficient "J" being caicuiated by the vane advance coefficientcaicuiating means, and obtains a thrust coefficient "KW" at a pitch"P" seiected form a predetermined range by referring to KT-J dataused for obtaining a thrust coefficient "KT" from the advancecoefiicient "J"; i thrust caicuiating means that receives the thrust coefficient"KW" at the pitch "P" from the thrust coefficient caicuiating means,and receives the water density "p", and the number of revoiutions"n" and the diameter "D" of the controiiabie pitch propeiier, andcaicuiates a thrust "TP" at the water depth of the vane and at thepitch "P" by the foiiowing expression (2),[Expression 21 TP==KTF.p.na.§4 ....{g) here, "TP" represents the thrust at the predetermined pitch of thevane, "Kv-p" represents the thrust coefficient at the predeterrninedpitch of the vane, "n" represents the number of revoiutions of thecontroiiabie pitch propeiier, and "D" represents the diameter of thecontroiiabie pitch propeiier; vana projection area input means that inputs a projectionarea "AP" of the vane at the pitch "P"; thrust ioad caicuiating means that receives the thrust "Tp" atthe water depth of the vane and at the pitch "P", the thrust "TP" 27 being caicuiated by the thrust caicuiating means, and theprejectien area "As" of the vane at the pitch, the projectien area"As" being inputted by the vane projectien area input means, andcaicuiates a thrust Head "T/Ap" at the water depth ef the vane andat the pitch "P"; circumferentiai speed caicuiating means that receives thenumber of reveiutions "n" and the diameter "D" of the centreiiabiepitch propeiier, and caicuiates a circumferentiai speed "aDN" of thevane; determining means that receives the thrust Head “T/Ap"caicuiated by the thrust ioad caicuiating means, and thecircumferentiai speed "nfihi" of the vane caicuiated by thecircumferentiai speed caicuiating means, and determines whetheror net the vane at the pitch "P" causes cavitation at the waterdepth "d" ef the vane, by referring to aiiowabie iirnit datarepresenting, for each water depth "d", a iimit of thrust Head withrespect to the circumferentiai speed; and centre! means that centreis the thrust coefficient caicuiatingmeans, the thrust caicuiating means, the thrust ioad caicuiatingmeans, and the determining means, and perferms operations ofidentifying a pitch "P0" ciese to the aiiowabie limit at the waterdepth "d" frem a piuraiity of pitches in the predeterrnined range,and then cenverting the pitch "P0" into a vane angie, to set thevane angie as a vane angie target vaiue "ag" at the water depth "d"of the vane.

3. The contreiiabie pitch prepeiier centre! ship according tociaim 2, wherein, when a vane of interest of the contreiiabie pitchpropeiier is present at the position ciosest to the water surface (a =Û°), and when the vane of interest is present at the positionfarthest from the water surface (e = 180%, the vana angieCommand section caicuiates the vane angie target vaiue by thecaicuiation according to ciaim 2, and when the vane is present atother positions, the vane angie comrnand section caicuiates thevane angie target vaiue by using the foiiowing expression (3), 28 [Expression 3]g{fi)agl+ il~fiüäfl) ° *i *i * here, "al" represents the vane angie target vaiue at "a" = G°, and"of" represents the vane angie target vaiue at "e" = 180%

4. The controiiabie pitch propeiier controi ship according tociairn 2, wherein, when a vane of interest of the controiiabie pitchpropeiier is present at the position ciosest to the Water surface (6 =0"), the vane angie command section uses, as the vane angietarget vaiue, a minimum vaiue of the vane angie determined by aspecification of the controiiabie pitch propeiier, and when the vaneof the controiiabie pitch propeiier is present at the position farthestfrom the water surface (a = 18Û°), the vane angie Commandsection caicuiates the vane angie target vaiue hy the caicuiationaccording to ciaim 2, and when the vane is at other positions, thevane angie Command section caicuiates the vane angie target vaiueby using the foiiowing expression (4), [Expression 4] aíæïam + í1mmsgš f. . _ . (å) here, "omm" represents the minimum vaiue of the vane angie, and"oz" represents the vane angie target vaiue at "a" = 180°.

5. S. The controiiabie pitch propeiier controi ship according to oneof ciaim 2 to ciaim 4, wherein the shaft depth input means ohtainsthe shaft depth hy the foiiowing expression (5), (Expression 5] .way-a ~-~-- (si here, "I" represents the shaft depth, "do" represents a draft, and"h" represents a height from a keei bottom surface to a propeiiershaft.

6. The controiiahie pitch propeiier controi ship according to oneof ciaim 2 to ciaim 5, wherein the vane water-death caicuiating 29 means caicuiates the water depth of the vane hy the foiiowingexpression (6),[Expression 6] aær-teaaa - - -1- (e) here, "d" represents the water depth of the vana, "I" representsthe shaft depth, "L" represents the iength of the vane, and "o"represents the rotation angie of the vane.

7. The controiiaoie pitch propeiier controi ship according to oneof ciaim 2 to ciaim 6, wherein the water-depth-reiated vaneadvance speed caicuiating means caicuiates the advance speed ofthe vane at the water depth of the vane hy using the foiiowingexpression (7),[Expression 7] rfio-wpr - - - ir) here, "VA" represents an advance speed, "w" represents a wakecoefficient, and "V" represents a cruising speed of the ship.

8. The controiiahie pitch propeiier controi ship according to oneof ciaim 2 to ciairn 7, wherein at ieast one of the wake distributiondata, the K-r-J data, and the aiiowabie iirnit data is expressed by apoiynomiai suojected to poiynomiai approximation.

9. The controiiabie pitch propeiier controi ship according to oneof ciairn 1 to ciairn 8, wherein the hydrauiic unit is a QDVChydrauiic unit. 1G.

10. The controiiabie pitch propelier controi ship according tociairn 9, wherein the inside of the boss of the controiiapie pitchpropeiier is fiiied with oii.

11. A controiiabie pitch propeiier controi rnethod comprising:receiving a water depth (d) at which a predetermined vaneof the* controiiabie pitch propeiier is present, and caicuiating 3G forward through-water speed (VA) of the vana at the water depth(d) from wake distribution data and a cruising speed (v) of a ship; caicuiating an advance coefficient (J) of the vane at thewater depth (d) from the number of revoiutions (n) and thediameter (D) of the controiiahie pitch propeiier and the forwardthrough-water speed (VA) of the vana; caicuiating a thrust coefficient (KW) at a pitch (P) seiected ina pradetermined range, hy using the advance coefficient (J) andKT-J data used for ohtaining a thrust coefficiant (KT) from theadvance coefficient (J); caicuiating a thrust (TD) at the water depth (d) and at thepitch (P) hy using the thrust coefficient (K-rp), the water density (p),the numher of revoiutions (n) and the diameter (D) of thecontroiiahie pitch propeiier; caicuiating a thrust ioad (T/Ap) of the vana from theprojection area (Ap) of the vane at the pitch (P), and the thrust(Twi caicuiating a circumfarentiai speed (i-rDN) of the vana; determining whether or not the vana at the water depth(d) and at the pitch (P) causes cavitation, hy using thecircumferentiai speed (fiDN), the thrust ioad (T/Ap), andaiiowahie iimit data represanting, for each water depth, the iirnitof thrust ioad with respect to the circumferentiai speed; and identifying a pitch (Pa) ciose to the aiiowahie iimit hydetermining whether or not the vana at each of a piuraiity ofpitches in the predetermined range causes cavitation, andconverting the pitch (P0) into a vana angie, to set the vanaangie as a vana angle target vaiue (oo), and then adjustingthavana angie of the vana to the vana angie target vaiua.

12. A controiiahie pitch propeiier controi method, comprising,when a vana of interest of the controiiahie pitch propeiier ispresent at a position ciosest to the water surface (G = u°), andwhen the vana is present at a position farthest from the watersurface (a = 186%, caicuiïating vana angie target vaiues hy usingthe controiiahie pitch propaiier controi method according to 31 clairn 11, and when the vana is present at other positions,calculating a vana angle target value hy using the followingexpresslon (8), [Expression 8] ataiaanfiišaiti-aatai - ~ ~ - (ai here, "al" represents the vana angle target value when "e" = G2and "ag" represents the vane angle target value when ”e” = 180%

13. A controllable pitch propeller control method, comprising,when a vana of interest of the controllable pitch propeller is presentat a position closest to the water surface (e = Git), using, as a vanaangle target value, a minimum value of the vana angle determlnedfrom a speciflcation of the controllable pitch propeller, and whenthe vana is present at a position farthest from the water surface (e== 18Û°), calculating a vana angle target value hy using thecontrollable pitch propeller control method according to claim 11,and when the vana is present at other positions, calculatlng a vaneangle target value by using the following expression (Q),[Expresslon å] grakamßfim-ri-aassi ~ - r - (s) here, "amln" represents the minimum vana angle, and 01.2"represents the vana angle target value when "a" = 180%

14. A controllable pitch propeller control method, comprisingadjusting the vana angle of a specific vana of the plurality of vanesprovided at the controllable pitch propeller to a vana angle targetvalue calculated by the controllabla pitch propeller control methodaccording to one of claim 11 to claim 13, and adjusting the vanaangle of each of the other vanes to a vana angle target valueobtained hy using a phase difference between the other vanes andthe specific vana.