Item 0575

 OTHER: Rotor Concept - Flight Control - Torque/Pitch Collective Rotor Hub

 

Overview:

A rotor hub for a small rotorcraft that allows the craft to operate similar to a gyrocopter, except that it has VTOL capability.

The craft might be configured with two bilateral rotors or two coaxial rotors. A total collective mechanism is contained within each of the hubs. The flight controls consist of cyclic, throttle and pedals; similar to those of the gyrocopter. There is no pusher prop and all thrust is from the two counterrotating rotors.

This hub provides:

    1. Thrust control by throttle alone. There is no collective lever. (same as constant speed propeller)
    2. Maintains rotor RPM within maximum and minimum limits. (same as constant speed propeller)
    3. Automatic entry into autorotation.

For other information on Torque~Pitch coupling, see; OTHER: Flight Dynamics - General - Cross-Coupling ~ Torque~Pitch

The database that is under development is [Torque-Pitch Coupling]. The objective is to see if this is possible to do.

Concerns:

This idea may not work for teetering hub.

This idea may work for ARR w/ weight-shift.

Perturbations:

This idea of a Torque-Pitch coupling may be flawed. This is because if the blade experiences a downdraft, the induced drag will decrease and this will cause the blade to advance (lead) and this will cause the blade's pitch to be decreased. The good news? ~ This action also has an out-of-plane component in that the downdraft will reduce the coning, which in turn may reduce the lead of the blade somewhat. Conversely, and updraft would have the same effect but in reverse, in that the blade's pitch will be increased. Could this be a serious flaw. Any damping (delaying) of the pitch response will slow down the cyclic change speed.

This may be OK since, with the craft's center of gravity ahead of the rotor, an upward gust will want to pitch the craft nose down and thereby counter the lift of the gust.

Potential Solutions:

      1. The torque producer is an electrical motor therefore an electronic accelerometer should be able to provide an instant adjustment of the motor's power.
      2. A modified control circuitry should be able to detect a sharp non-pilot induced change in the torque and instantly adjust the motor's power.
      1. Rotating weights at the end of moment arms and located on the mast could react to sudden vertical motion and thereby adjust the collective pitch of the blades.
      2. Consider some type of cone (flap) / pitch coupling.
        1. Build it into the composite blade's skin by using a cloth that has carbon in one direction an glass in the other direction. Then lay the cloth diagonally.
        2. Build it in to a composite hub-bar, possibly as a diagonal overwrap.

This may also be advantageous for RRPM at entry and in autorotation.

      1. Would it be helpfull and possible to increase the weight in the blades leading edge, thereby causing the higher inertia of this weight to pitch the blade toward the direction of the perturbation?

General Notes:

Re: Bilateral Main Rotor Synchronization:

What assures that the torque-pitch couplings of the two rotors are always providing equal outputs; and is this particularly critical since the rotors are held in rotational synchronization. Ground adjustment; or temporary cyclical control allowances during flight.

The collective pitch [θ0] is a summation of the torque's contribution [θ0Q] and the coning angle's contribution [θ0a0].

This method should result in fast response to pilot inputs and to aerodynamic conditions. The maintaining of rotor speed [Ω] with in predetermined boundaries is the responsibility of these two inputs. The rotor speed is not directly governed.

The power [P] is varied by the pilot's throttle control. An elastomeric device is located in the rotor hub. Torque [Q] applied to the mast will cause the azimuth [ψ] of the mast and that of the hub to differ. The greater the torque the greater the offset (difference) [ψoff]. This relationship between change in torque [ΔQ] and change in azimuths [Δψ] will be exponential not linear (see sketch A). This way the pitch change is large at low torque level changes and small at high torque levels. The collective pitch is partially dependent on this azimuth offset. A damper may be interfaced with this device to eliminate any tendency to oscillate.

A ball screw could be used to change the axial position of the pitch link, as one component experiences angular displacement about the other, Alternatively, just a linkage from the rotation.

The coning angle [a0] is varied by a change of the loading on the rotor disks or by a change in the rotor speed. The collective pitch is coupled to the coning angle (see sketch B). A possible means of achieving this might be for the hub to have a teetering hinge and a pair of coning hinges, similar to the Robinson's Hub. A difference would be that the two coning hinges are mechanically linked together so that their coning angles are always identical. This would eliminate any chance for them to act as flapping hinges.

The pitch links, which on the Robinson R-22 are horizontally inline with the coning hinges, would be moved slightly further outward. This will result in pitch being pulled from the blades as they cone up. The bottom of these pitch links will be out further as well and this may result in no change the delta-3 action of the teetering hinge. An ideal pitch to cone ratio might be 1:1, as is the Groen.

The delta-3 on the teetering hinge might be by flap hinge geometry and the delta-3 on the coning hinges might be by control system geometry.

For additional information on pitch-cone coupling see Chuck Beaty's notes on Groen

Sketch A

Sketch B

This could be similar to that of the gyrocopter.

Power would be transmitted to the rotor head via a constant velocity joint, which will be concentric with the Hooke's joint (cyclic pivot mechanism). The Hookes joint obviously has an open center, to locate the CVJ.

Consider eliminating the CVJ and have the engine move with the tilting of the rotor disk. See; Electro - Simplex

The minimum allowable pitch is that for ideal autorotation.

The maximum allowable pitch is that for ideal full power. May require more in "emergency" situations.

Minimum allowable pitch is at zero torque and pre-cone angle.

Maximum allowable pitch is at maximum torque plus some cver-coning. May require more in "emergency" situations.

Torque Calculations:

General Thought: The rotor and engine are always turning at the optimum (maximum?) RPM, because of the pitch-cone coupling. Therefore, when additional torque is required the engine does not have to increase the RPM of the system to deliver it. It is instantly available.

Electric Motor Drive: An electric motor will respond faster than an engine to a pilot instigated request for more power. An electric motor can produce higher short-term power increase than an engine can.

____________________________________

Consider maximum collective (maximum torque) as 20º.

Initially, consider the maximum offset in azimuth as 20º.

Drag:

The torque will equal the drag, plus the acceleration. The drag will consist of profile drag and induced drag.

Concern re Auto Individual Blade Pitch: This auto collective may very well work for collective, however, it appears highly unlikely that it will work for individual (independent) blade pitch: This is because, during forward flight, the advancing blade will be experiencing more drag than the retreating blade is experiencing. WHY? Therefor the strong implication is that independent blade torque, as envisioned for an electric drive, will not work for cyclic control. THIS MAY NOT BE TRUE.

Power/thrust change:

Horsepower [HP] = Torque [Q] x RPM [RPM] / 5250

Power [P] = Torque [Q] x Rotational speed [Ω]

A change to the power setting [ΔP] will change the torque [ΔQ], which in turn will change the blade pitch [Δθ] (greatly at low torque levels & slightly at high torque levels. This change in the torque will attempt to change the rotor speed [ΔΩ], but the change in the pitch and the subsequent change in induced drag, will oppose this attempted change in RPM. The rotor speed [Ω] will then slowly adjust to the new power setting and the torque [Q] and pitch [θO] will slowly return part way toward the settings they were at before the change in power.

The Torque [lb-ft] equals the sum Profile Drag [lb.] and the Induced Drag [lb.] times the length from the mast to 0.75% (approx.) of radius [ft]; Q = (DO + DI) * 0.75R. For more information on drag see: B319.html

Azimuth Offset:

= sin((actual torque / maximum torque) * 90) * maximum azimuth offset Is this accurate?

ψoff = sin(Q/QMax)* 90) * ψoffMax [in degrees] Is this accurate?

Contribution to collective:

= Azimuth offset

θ0 Q = ψoff [in degrees]

Coning Angle Calculations:

For coning angle use FORM: Rotor - Disk - Coining in Hover SynchroLite w' 1lb tip weight is 1.62º

Consider cone-pitch coupling as 1:1.

Consider lowest collective setting (for autorotation) as +1º

_______________________

a0 = ((2/3) * γ * (( CT/σ) / α)) - (((3/2)* Acceleration) * R / ΩR 2)

CToverSigma = rst.Fields!CT / Sigma

a0 = ((2 / 3) * (Gamma) * (CToverSigma / rst.Fields!aa)) - (((3 / 2) * Acceleration * R) / ((Omega_R) ^ 2))

The above is from Access & the below is from logic??

Centripetal Force:

F = (M * Ω2 * R) / 2 [radius will be 75% of span]

Thrust:

T = 2 * ρ * V2 * A

Coning Angle:

a0 = sin(T/F) [in degrees]

Contribution to collective:

= hover coning angle - coning angle

θ0 a0 = a0hov - a0 [in degrees]

Collective Pitch:

= torque contribution plus coning angle contribution.

θ0 = θ0Q + θ0 a0

Autorotation:

The change in pitch to the minimum allowable pitch will be automatic and relatively instantaneous on loss of power. The optimal setting may be that for greatest range.

There is no current means of using the energy in the rotor at flare but this is no different from an engine-out flare in a gyrocopter. The low dissent rate, ground effect and a proper undercarriage should minimize this problem.

Flare and other requirements for consuming the dynamic energy stored in the rotor disk:

There must be a means of overriding the above and utilizing this energy; during autorotation flare etc. Perhaps this can be done by having advances of the throttle increase torque up to maximum torque, then any further advances of the throttle increase blade pitch. This might work; the pilot is calling for torque, not collective. When the power train is delivering torque, the system will deliver the energy that is called for, up to the limits of the power trains' ability. A call for torque above this can AND MUST be delivered by the rotor. When the power train is not delivering torque (i.e. engine(s) out) the system deliver the energy from the rotating rotor, again, up to the limits of its ability. This sounds a lot like a governor!

Alternatively: There may not be any need for tip weights, if the blades and yoke are rigid. Therefore, the weight saved could be used in a cushioning device for landing. This 'cushioning device' could be air bags, rockets or even something that applied torque to the rotor hubs, for a short period of time. Another idea would be a pinwheel on the rotors, which would provide torque for a few seconds between flare and landing. If this was to be incorporated into a FAA ultralight craft [SynchroLite] then the rate of descent in autorotation is relatively slow to begin with. If used on an ultralight craft, the weight of any device will probably not have to be included in the 254-lb. limit.

Electric Motor Drive: A large capacitor might be satisfactory if the reason for the autorotation is loss of battery power.

See [MDD p.112] for similar idea. Using Rotor Governor.

FORM: Auto-Collective:

In Access [Helicopter] database. (incomplete)

Note that there is also the database [Torque-Pitch Coupling]

Variables:

Applications:

Sport Pilot/Aircraft:

If there is an intent to incorporate this in a simple helicopter for potential inclusion in Sport Pilot/Aircraft then perhaps this device could be a certified one that can only be inspected and replaced by the owner/operator/repairman. It then becomes component in an otherwise uncertified rotorcraft.

Adjustments & Settings:

Settings are done at the factory or by a certified mechanic. They are done to suit the requirements of the specific craft in which the hub will be installed. The craft are single seat so the gross weight will not vary much and a mean value may be used.

Does polyurethane "stiffness" change much with temperature change. This temperature change will come from the ambient air temperature, change in elevation and heat generated by the adjacent gears.

Power Train Design:

Consider having the rotor, mast, reducer and engine as one rigid assembly. This compete assembly will roll and pitch in the Hooke's joint.

Cyclic:

Consider using Bowden cables for simplicity.

Pitch Link Location:

If the pitch link was located on the leading edge of the blade perhaps both the coning hinge and the length of the pitch arm can be increase. This may give faster response and less load on the pitch arm.

Throttle:

Settings are done at the factory or by a certified mechanic. They are done to suit the requirements of the specific craft in.

Consider have springs on both sides of the engine's throttle lever. The springs will position the throttle at a RPM that will give a slow rate of descent. The helicopter will there by come to a safe landing should the throttle linkage between the operator and engine break.

Potential Problems:

    1. The firing of the one or two cylinder engines will result in large changes in torque. This may be destructive to the damper and other components, plus it may result in an oscillation of the collective pitch. Can this rotational vibration be removed by a larger flywheel or preferably a spring-type shock absorption device?
    2. The rotor RPM varies therefor there is a possibility that at one or more RPMs their may be harmonic resonance.
    3. If the profile drag is greater when the blades are at azimuth 90-270º then when they are at 0-180º, will this cause an increase in thrust, which with two rotors will cause a rolling oscillation? Might the pitch-cone coupling reduce it?
    4. It will probably be impossible to get a clean 'jump' takeoff.
    5. Will the two units always work in unison?

Drawing:

Notes:

The pitch link is on the trailing edge side of the blade.

Notes Related Specifically to Craft with Twin Rotors:

Matching Rotor Speeds:

Concern?

Outside Helicopter

Ivo said that he had incorporated a type of torque or RRPM (rotor governor) in his intermeshing helicopter.

William Hunt's, of Sikorsky, idea for an autocollective; [Source ~ HP p.194-196]

o   These three pages are viewable at;

§  http://www.UniCopter.com/WilliamHunt194.jpg

§  http://www.UniCopter.com/WilliamHunt195.jpg

§  http://www.UniCopter.com/WilliamHunt196.jpg

o   Could the offset between the pitch axis and the mast axis necessitate strong pitch control forces or does inplane bending of the blades place the blade's CG normal to the flapping axis?

o   The hub tilts about a simple universal joint. This means that when the mast axis and the hub axis are not aligned there will be a 2P rotational oscillation.

o   In addition, the blades individually flap.

o   For additional notes see comments on sidebar of fig. 132 A.

o   It is interesting to compare Hunt's overall hub layout to that of Breguet's G-11E [Source ~ MDD p.152]. Without considering Hunt's Automatic Pitch Control, they have the same general arraignment. However, Breguet's pitch axes intersect the mast axis whereas Hunt's pitch axes lead the mast axis. Note that Breguet's hub does not appear to tilt. It only has the flap hinges for out-of-plane motion; see note on fig. 132 A

Related Patents:

Propeller hub with self-adjusting pitch mechanism

6,158,960

Have hard copy.

This will probably be of relevance to the UniCopter; but not to the AeroVantage due to its unique dual function operation.

 

Searches of US Patents and Applications:

 

Search Terms:

Patents:

Applications:

 

torque AND pitch AND (blade OR airfoil) AND (rotorcraft OR helicopter OR gyrocopter)

744

447

 

torque AND pitch AND (blade OR airfoil) AND (rotorcraft OR helicopter OR gyrocopter) AND (thrust OR lift)

593

394

 

torque AND pitch AND (blade OR airfoil) AND (rotorcraft OR helicopter OR gyrocopter) AND (thrust OR lift) AND rotor

555

360

 

torque AND pitch AND (blade OR airfoil) AND (rotorcraft OR helicopter OR gyrocopter) AND (thrust OR lift) AND rotor AND coupling

215

129

 

("torque pitch coupling") OR ("torque-pitch coupling") OR ("torque to pitch coupling")

0

0

Related Pages:

Constant Rotor RPM

0786

DESIGN: SynchroLite ~ Rotor - Hub - w/ Coning Hinges

0813

SynchroLite ~ Control - Flight - Governor

UniCopter ~ Control - Flight - Governor

Dragonfly ~ Control - Flight - Governor

DESIGN: AeroVantage ~ PropRotor - Hub - Thrust Related Considerations

1679

Electrotor-SloMo - Rotorhub - Torque-Pitch-RRPM

DESIGN: ~ Electrotor - Control (flight & power)

A125

Electrotor-Simplex ~ Rotor - Hub (Head)

Possible Rotorcraft Layouts:

OTHER: Helicopter - Inside - Intermeshing - Dragonfly

Dragonfly

OTHER: Helicopter - Inside - Intermeshing - SynchroLite w/ Changes

0870

OTHER: Helicopter - Inside - Interleaf - Ultralight and UAV

0035

OTHER: Helicopter - Inside - Side-by-Side - Ultralight and UAV

0578

Auto-Collective

A couple of Potential Applications:

DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque/Pitch Collective & Teetering Drive:

AeroVantage ~ PropRotor - Adjustable Pitch (Adjustable Thrust?)

This might be applicable to; a gyrocopter with powered rotor assist (a level of power assist that is just below that which can be countered by the props thrust against a hard-over rudder),

Database ~ Forms & Procedures:

This program can be cross-checked with the Helicopter database using [Side-by-Side Ultralight and UAV]

Note that there is a Form [Auto-Collective (governor)] in the Helicopter database

Flow Chart for Computer Program Auto-Collective Database - Electrotor-Simplex Form:

Objective is that a torque increase and/or a speed increase (ie. power increase) will each increase the angle of attack, with the torque increase obviously causing the fastest response and the speed acting on a semi 'rotor governor'.

To see if system has static and dynamic stability

The 'caused' items in Code 5 do not appear to be correct.

The intent is to use the change in the coning angle to act as a rotor governor. It may not (safely) give enough change in the angle of attack and this may require the inclusion, or substitution, of the use of the centrifugal force for angle of attack and speed control.

Flow Chart: This may not work since the program will probably have to be a reiterative one that settles out.

Notes Regarding the Database:

Initially all routine flags are 'True'

Only enter a routine if its flag is 'True'

If after the calculations in that routine for that variable is within the tolerance for that routine, then set that routines flag to 'False' when leaving it.

The tolerance for angles is 0.25%

The tolerance for distance and speed etc. is 1%

When all flags are 'False', leave the loop and go to the next power setting.. 

Code:

Symbols:

Description:

Initial state

 

Power, Torque, RRPM, Pitch, AoA, Induced drag, Profile drag, Angular momentum, Inflow angle, Centrifugal force and Conning angle are all constant.

Rotational Acceleration is zero

1

ΔP↑ ► ΔQ↑

Power increase causes Torque increase: (Note that a motor will react faster than an engine).

2a

ΔQ↑ ► Δθ↑

Torque increase causes Pitch increase.

2b

ΔQ↑ ►G ΔαA↑

Torque increase causes gradual Rotational Acceleration

3

ΔαA↑ ► ΔΩ↑

Acceleration increase causes Speed increase.

4

ΔΩ↑ ► ΔDO↑

Speed increase causes Profile-Drag increase

 

ΔΩ↑ ► ΔDI ↑

Speed increase causes Induced-Drag increase

 

ΔΩ↑ ► ΔQ↓

Speed increase causes Torque decrease

 

ΔΩ↑ ►

Speed increase causes NO

 

ΔΩ↑ ► Δα↓

Speed increase causes Angle-of-Attack decrease

 

ΔΩ↑ ► ΔΦ↑

Speed increase causes Inflow Angle increase

 

ΔΩ↑ ► ΔL↑

Speed increase causes Angular Momentum increase

 

ΔΩ↑ ► ΔCF↑

Speed increase causes Centrifugal-Force increase

 

ΔΩ↑ ► ΔaO↓

Speed increase causes Coning decreases.

5

Δθ↑ ► Δα↑

Pitch increase causes Angle-of-Attack increase.

6

Δα↑ ► ΔDI↑

Angle-of-Attack increase causes Induced-Drag increase

7

ΔDI↑ ► Δθ↓

Induced-Drag increase causes Pitch decrease.

8

ΔDO↑ ► Δθ↓

Profile-Drag increase causes Pitch decrease.

9

ΔL↑ ► ????

Angular Momentum increase causes ????.Anything?

10

ΔΦ↑ ► Δα↓

Inflow angle increase causes small Angle of Attack decrease

 

ΔΦ↑ ► ΔVI↑

Inflow angle increase causes Induced-Velocity increase.

11

ΔCF↑ ► Δθ↑

Centrifugal-Force increase causes small Pitch increase. (Rotor governor)

12

Δ aO ↑ ► Δθ↓

Coning increase causes Pitch decrease. (1)

Δ = Change.| Δ = Small change.| ► = Causes.| G = Gradually causes

 (1) If coning angle were to be used it must be used carefully. In other words it must be exponential that only pulls meaningful pitch at very high coning angles.

Average coning angle = β0 = tan-1 (L / (b * CF)) = tan-1 (275 / (2 * 3949)) = 1.99 [degrees].

 

Torque-Pitch Coupling Database ~ Code [Support Routines]:

A flow diagram would be nice but very complex.

Notes:

A change in the gross weight [+] will change the coning angle [+] which will change the pitch [-] which will cause the pilot to use a changed power [+], which will cause a change in the torque [+], which will cause a change in the pitch [+]. Is there a need for a ground-based change to be made to the mechanism before flight to take into account the varying pilot weights?

Last posting on Rotorhead?: Vibration, Stability & Controllability. This device is intended for the Electrotor - Simplex.

Delta3:

Automatic Pitch-Changing Propellers in Aircraft Propellers and Controls - Chapter VII, page 42 ~ by Jeppesen:

 

Power: increase

P ↑

►

Ω↑

Speed: increase

 

Speed: increase

Ω↑

►

CF↑

Centrifugal twisting moment: increase

 

Centrifugal twisting moment: increase

CF↑

►

θ↓

Pitch: decrease

 

Speed: increase

Ω↑

►

T↑

Thrust: increase

 

Thrust: increase

T↑

►

Δ3↑

Delta3; increase

 

Delta3; increase

Δ3↑

►

θ↓

Pitch: decrease

 

Speed: increase

Ω↑

►

α↑

Angle-of-Attack: increase

 

Angle-of-Attack: increase

α↑

►

aO ↑

Coning angle: increase

 

Coning angle: increase

aO ↑

►

θ↓

Pitch: decrease

 

Other Web Page at this Site on Auto-Collective ~ Torque Pitch

Note: The total weight, which varies according to the weight of the pilot, will probable effect the RRPM-Pitch-Torque balance. Can it be pre-flight adjustable to suit each flight?

OTHER: Miscellaneous - Thoughtless Idea - Constant Speed Rotor

OTHER: Flight Dynamics - General - Cross-Coupling # Torque-Pitch

OTHER: Flight Dynamics - General - Lead-Flap Coupling, for Intermeshing Rotors & Pitch-Lag Coupling

OTHER: Flight Dynamics - General - Pitch-Lag Coupling

Electrotor-SloMo - Control - Flight - Auto-Collective by T-P - Calculations

DESIGN: Single-Bladed All Electric Rotor- Rotor Hub - Pitch-Torque Coupling

DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque Collective B

DESIGN: Electrotor-Simplex ~ Rotor - Hub - Overview of Gimbaled w/ Torque/Pitch Collective & Teetering Drive:

Electrotor-SloMo - Rotor - Hub - Torque-Pitch-RRPM

Introduction Page | SynchroLite Home Page | Electrotor Home Page | UniCopter Home Page | Nemesis Home Page | AeroVantage Home Page:

Initially displayed: October 5, 2002 ~ Last Revised: November 22, 2012

The above utility invention is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.