U.S. patent application number 13/511909 was filed with the patent office on 2012-10-25 for flap control for wind turbine blades.
This patent application is currently assigned to VESTAS WIND SYSTEMS A/S. Invention is credited to Carsten Hein Westergaard.
Application Number | 20120269632 13/511909 |
Document ID | / |
Family ID | 41572690 |
Filed Date | 2012-10-25 |
United States Patent
Application |
20120269632 |
Kind Code |
A1 |
Westergaard; Carsten Hein |
October 25, 2012 |
FLAP CONTROL FOR WIND TURBINE BLADES
Abstract
A wind turbine blade has one or more trailing edge flaps. An
actuator mechanism for the flaps comprises a shaft extending along
the blade length driven by a motor arrangement toward the blade
root. The flap is connected to the shaft through a linkage so that
rotation of the shaft pivots the flap about a hinge line. The
linkage may be non-rigid and coupled to the shaft through a roller,
or rigid and coupled to the shaft through a crank arm mounted on
the shaft. An offset actuation mechanism is provided for imparting
movement to the linkage in addition to movement due to rotation of
the shaft.
Inventors: |
Westergaard; Carsten Hein;
(Houston, TX) |
Assignee: |
VESTAS WIND SYSTEMS A/S
Aarhus N
DK
|
Family ID: |
41572690 |
Appl. No.: |
13/511909 |
Filed: |
November 23, 2010 |
PCT Filed: |
November 23, 2010 |
PCT NO: |
PCT/EP2010/068042 |
371 Date: |
June 29, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61264463 |
Nov 25, 2009 |
|
|
|
Current U.S.
Class: |
416/159 |
Current CPC
Class: |
F05B 2260/70 20130101;
F05B 2240/3052 20200801; F03D 1/0641 20130101; F03D 7/0232
20130101; Y02E 10/72 20130101 |
Class at
Publication: |
416/159 |
International
Class: |
F04D 29/36 20060101
F04D029/36 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2009 |
GB |
0920681.4 |
Claims
1. A wind turbine blade comprising at least one control flap on an
edge of the blade, and an actuation mechanism for controlling
movement of the flap, the actuation mechanism comprising an
actuator shaft extending along at least a portion of the length of
the blade, an actuator coupled to the shaft to rotate the shaft,
the actuator being arranged towards the root end of the blade, a
linkage coupled between the flap and the actuator shaft, whereby
rotary movement of the shaft moves the flap, and an offset
actuation mechanism for imparting movement to the linkage in
addition to movement due to rotation of the shaft.
2. The wind turbine blade according to claim 1, wherein the linkage
comprises a rigid rod coupled at one end thereof to a first end of
an L-shaped crank mounted for rotation about the shaft, the
L-shaped crank being coupled to a crank arm mounted on the shaft
for rotation therewith through an offset actuator, whereby
actuation of the offset actuator moves the L-shaped crank with
respect to the shaft to provide an offset movement to the flap.
3. The wind turbine blade according to claim 2, wherein the offset
actuator is a piezo-electric stack and excitation of the
piezo-electric stack moves the L-shaped crank with respect to the
shaft to provide an offset movement to the shaft.
4. The wind turbine blade according to claim 1, wherein the linkage
comprises a control wire coupled to the shaft through a roller, and
the offset movement mechanism comprises a motor and gear mechanism
for rotating the roller with respect to the shaft.
5. The wind turbine blade according to claim 1, wherein the flap is
pivotable about a hinge line and wherein rotary movement of the
shaft causes the linkage to pivot the flap about the hinge
line.
6. The wind turbine blade according to claim 2, wherein the rigid
rod is attached to the rotatable shaft through a crank arm mounted
on the shaft for rotation therewith.
7. The wind turbine blade according to claim 4, wherein the control
wire is coupled to the actuator shaft through a roller fixed to the
shaft for rotation therewith.
8. The wind turbine blade according to claim 1 wherein the linkage
comprises a first linkage and a second linkage and the flap is
pivotable about a mid-point, wherein the first linkage is attached
to the flap at a point above the midpoint and the second linkage is
attached to the flap at a point below the midpoint, and wherein the
first and second linkages are coupled to the shaft through a double
arm crank fixed to the shaft for rotation therewith.
9. The wind turbine blade according to claim 1 comprising a spring
arranged between the flap and the blade, the spring biasing the
flap towards an extended position.
10. The wind turbine blade according to claim 1, comprising a
plurality of control flaps, each control flap being movable by
rotation of the shaft through a respective linkage.
11. The wind turbine blade according to claim 1, wherein the
actuator shaft extends substantially along a structural member of
the blade.
12. wind turbine blade according to claim 1, wherein the actuation
mechanism and the flap are formed as a unit detachable from the
blade.
13. A wind turbine having a rotor comprising a plurality of rotor
blades, each rotor blade comprising at least one control flap on an
edge of the blade, and an actuation mechanism for controlling
movement of the flap, the actuation mechanism comprising an
actuator shaft extending along at least a portion of the length of
the blade, an actuator coupled to the shaft to rotate the shaft,
the actuator being arranged towards the root end of the blade, a
linkage coupled between the flap and the actuator shaft, whereby
rotary movement of the shaft moves the flap, and an offset
actuation mechanism for imparting movement to the linkage in
addition to movement due to rotation of the shaft.
Description
[0001] This invention relates to wind turbines, and in particular,
to the control of flaps on wind turbine blades.
[0002] It is known to incorporate control surfaces into wind
turbine blades, and a number of proposals have been made for
actuating those control surfaces in response to various
conditions.
[0003] US-A-2003/0123973 (Murakami) discloses a rotor for a wind
turbine, the blades of which have extendible auxiliary blades at
the blade tips, together with a plurality of extendible vanes on
the leading and trailing blade edges. The leading and trailing edge
vanes are controlled by hydraulic or electric actuators arranged
along the length of the blade.
[0004] DE-A-2922885 (Rath) discloses a trailing edge flap
arrangement for a wind turbine blade in which the flap is actuated
either by hydraulic cylinders or by a connecting rod actuated by an
electric motor. The flaps are at the blade tips and the actuators
are arranged proximate the flaps.
[0005] These actuating arrangements are unsatisfactory as they
require a large number of moving parts to be arranged within the
wind turbine blade away from the nacelle. Wind turbines are often
located in remote and inaccessible locations, for example,
offshore, and it is desirable that maintenance is as limited and as
straightforward as possible. The arrangements of US 2003/0123973
and DE-A-2922885 do not meet with these requirements. In each case,
complex actuators are arranged along the blade at positions remote
from blade access points at the root of the blade. This makes
access difficult and time consuming and may even require removal of
the blade which is impractical. Wind turbine blades may be over 40
m in length and taper towards the tip. It is highly undesirable to
have to access components in the interior of the blade towards the
tip.
[0006] The invention aims to address the disadvantages of the prior
art discussed above.
[0007] According to the invention, there is provided a wind turbine
blade comprising at least one control flap on an edge of the blade,
and an actuation mechanism for controlling movement of the flap,
the actuation mechanism comprising an actuator shaft extending
along at least a portion of the length of the blade, an actuator
coupled to the shaft to rotate the shaft, the actuator being
arranged towards the root end of the blade, a linkage coupled
between the flap and the actuator shaft, whereby rotary movement of
the shaft moves the flap, and an offset actuation mechanism for
imparting movement to the linkage in addition to movement due to
rotation of the shaft.
[0008] Embodiments of the invention have the advantage that the
actuator, which may be an electric, an hydraulic motor or similar,
is arranged towards the root of the blade where it is easily
accessible and may be serviced as part of a scheduled maintenance
visit. Moreover, the actuation mechanism may be very simple
reducing the need for maintenance and increasing reliability. The
offset mechanism has the advantage of imparting a high frequency
movement to one or more flaps in addition to a lower frequency
movement imparted by rotation of the shaft.
[0009] In a preferred embodiment, the linkage may be a rigid rod
which may be attached to the rotatable shaft through a crank arm
mounted on the shaft for rotation therewith.
[0010] The offset mechanism may comprise an L-shaped crank mounted
for rotation about the shaft and to which the rigid rod linkage is
attached, wherein the linkage comprises a rigid rod coupled at one
end thereof to a first end of an L-shaped crank mounted for
rotation about the shaft, the L-shaped crank being coupled to a
crank arm mounted on the shaft for rotation therewith through an
offset actuator, whereby actuation of the offset actuator moves the
L-shaped crank with respect to the shaft to provide an offset
movement to the flap.
[0011] Preferably the offset actuator is a piezo-electric stack and
excitation of the piezo-electric stack moves the L-shaped crank
with respect to the shaft to provide an offset movement to the
shaft.
[0012] In a preferred embodiment the linkage is a control wire. The
control wire may be coupled to the actuator shaft through a roller
fixed to the shaft for rotation therewith. A plurality of rollers
may be arranged on the shaft, each receiving a control wire for a
flap. This has the advantage that the diameter of each roller may
be chosen so that rotation of the shaft causes the correct amount
of movement of the flap.
[0013] Where the linkage is a control wire, the offset mechanism
may comprise a control wire coupled to the shaft through a roller,
and the offset movement mechanism comprises a motor and gear
mechanism for rotating the roller with respect to the shaft.
[0014] Preferably, the flap is pivotable about a hinge line wherein
rotary movement of the shaft causes the linkage to pivot the flap
about the hinge line.
[0015] Preferably, a spring is arranged between the flap and the
wind turbine blade whereby the flap is biased towards an extended
position. This has the advantage that the flap is biased towards a
failsafe position.
[0016] Preferably, the blade comprises a plurality of flaps, for
example, along the trailing edge of the blade, wherein each flap is
pivotable by rotation of the shaft through a respective
linkage.
[0017] Preferably, the linkage comprises a first linkage and a
second linkage and the flap is pivotable about a mid-point, wherein
the first linkage is attached to the flap at a point above the
midpoint and the second linkage is attached to the flap at a point
below the midpoint, and wherein the first and second linkages are
coupled to the shaft through a double arm crank fixed to the shaft
for rotation therewith.
[0018] This arrangement is advantageous as it enables the flap to
be controlled when it is pivoted about a hinge line at the
mid-point of the flap enabling the flap to move towards both the
suction and pressure sides of the blade.
[0019] Preferably, the actuator shaft extends substantially along a
structural member of the blade such as a spar or beam.
Alternatively, the actuator mechanism and the shaft may be formed
as a unit detachable from the blade. This arrangement has the
advantage that the whole actuator mechanism may be detached from
the blade so facilitating maintenance.
[0020] The invention also resides in a wind turbine having a
plurality of blades each having an actuation mechanism as described
above.
[0021] Embodiments of the invention will now be described by way of
example only, and with reference to the accompanying drawings, in
which:
[0022] FIG. 1 is a cross-section through a wind turbine blade
having a trailing edge flap;
[0023] FIG. 2 is a schematic plan of a wind turbine blade having a
pair of trailing edge flaps;
[0024] FIG. 3 is a similar view to FIG. 2 showing an alternative
flap control arrangement;
[0025] FIG. 4 shows an enhancement to the embodiment of FIG. 1;
[0026] FIG. 5 shows an alternative arrangement to the embodiment of
FIG. 4;
[0027] FIG. 6 shows a further embodiment;
[0028] FIG. 7 shows a further embodiment in which the trailing edge
flap is mounted as a detachable unit;
[0029] FIG. 8 is a graph of actuation frequency against flap
amplitude showing optimal flap performance;
[0030] FIG. 9 shows an embodiment of the invention permitting fast
offset movement of the flap; and
[0031] FIG. 10 is an alternative arrangement to that of FIG. 9.
[0032] The following description relates to control of one or more
trailing edge flaps on a wind turbine blade. The term "flap" refers
to a movable surface of the wind turbine blade which will modify
the aerodynamic profile of the wind turbine blade. However, the
invention is not limited to trailing edge flaps but is also
applicable to the actuation of leading edge devices (typically
slots or slats) and other control surfaces arranged along the blade
edges as opposed to the tip only. The following description is
limited to trailing edge flaps for simplicity. Moreover, the
embodiments to be described are not limited to any particular
number of flaps, wherever located, and may be used to actuate a
single flap or two or more flaps arranged along the leading or
trailing edge of a blade.
[0033] When designing a flap system for a wind turbine it is highly
desirable to move the vulnerable parts, such as the actuators, from
the outer parts of the blades to the roots so that they can be
serviced as part of the normal service visits and accessed through
the hub. Components located towards the blade tips are hard to
access in situ and may require the blades to be removed.
[0034] FIG. 1 shows a cross-section of a wind turbine blade. The
present invention is applicable to any wind turbine, for example a
horizontal axis turbine having a rotor within three blades.
[0035] The blade 10 comprises an upper surface 12 and a lower
surface 14, commonly referred to as the suction surface and the
pressure surface, each made from a lightweight composite material
by well known techniques. A strengthening spar 16 or beam extends
along the length of the blade, as can be seen from FIGS. 2 and 3,
from the root end 18 of the blade towards the tip end 20. The blade
has a leading edge 22 and a trailing edge 24. The trailing edge has
at least one moveable flap 26 arranged along a part of its length.
As can be seen from FIG. 1, this flap is moveable by an actuation
mechanism between an extended position 28 in which the flap extends
on the suction side of the blade, and a retracted position 30, in
which the flap is flush with the blade. These two positions are
shown in FIG. 1 and the flap may adopt any intermediate position.
The extent of movement of the flap is a matter of design choice and
the flap may be configured to extend on the pressure side of the
blade if desired.
[0036] As shown in FIG. 1, the flap is hinged for rotation about a
hinge line that forms part of the suction surface of the blade. The
hinge may be the actual material of the upper shell of the blade,
suitably strengthened if necessary, or may be a mechanical hinge
arranged, for example, under the surface. As will become clear from
further embodiments described below, the hinge position may
change.
[0037] In the embodiment of FIGS. 1 to 3, the flap is spring biased
towards the extended position shown on the suction side. Thus, the
flap will adopt the extended position if no force is applied
against the bias of the spring. The fail-safe position is therefore
in the extended or deployed position on the suction side of the
blade as this provides the lowest possible lift coefficient. This
is desirable, for example, in the parked condition where a loss of
power may cause the flaps to be un-deployable. In these conditions
it is desirable that the loading on the blade is as low as
possible.
[0038] As can best be seen from FIG. 2, the actuation mechanism
includes an actuator shaft 32 arranged to extend along at least a
portion of the length of the blade. In this embodiment, the shaft
is a torsion shaft and is arranged alongside the beam, generally
following the neutral line of the blade. As will become clear from
later embodiments, this is desirable but not essential. The
actuator shaft 32 is mounted for rotation with respect to a
plurality of supports 34 which may be roller bearings or bushings,
for example, and which are fixed to the beam at points along its
length. At the root end of the blade, the free end of the shaft is
attached to an actuator 36 which is arranged towards the root end
of the blade and which serves to actuate the shaft. It is presently
considered that the shaft should be arranged close to the pressure
side 14 of the blade to maintain the optimum angle between the wire
and the perpendicular to the hinge line to give maximum torque on
the hinge. However, this may not be practical in some blade designs
which have a high degree of curvature along their length. In such
blades, the shaft may be mounted closer to the suction side or the
wire 38 may be permitted to penetrate the pressure side 14 of the
blade shell. It is generally considered better for the suction side
to be smooth and so the hinge is located on the suction side. By
placing the rod or wire at the pressure side the stress in the
system is reduced and a greater linear actuation is ensured as the
angle between the arm 48 and the rod 44 can be close to 90
degrees.
[0039] A control linkage comprising a control wire 38 is attached
to the shaft at one end and to the flap 26 at its other end. As
shown in FIG. 1, the wire is attached to the rear wall of the flap
towards the flap edge opposite the hinged edge. Thus, in FIG. 1,
where the hinge is on the suction side of the flap, the control
wire is attached to a back wall of the flap near the pressure side
of the flap. Although the control wire may be attached directly to
the shaft, it is preferred, as shown in FIG. 1, that it is attached
to a roller or drum 40 which is mounted on the shaft for rotation
of the shaft. The diameter of the roller will determine the amount
of movement of the control wire for a given degree of movement of
the shaft. Thus, by selecting different roller diameters, differing
amounts of movement may be obtained for a plurality of control
wires. The amount of movement required will depend on the flap size
and the profile size at that region of the blade. As shown in FIG.
2 the roller associated with the tipwards flap 26t has a smaller
diameter than the roller associated with the hubwards flap 26r as
the amount of movement required is lower.
[0040] The actuator may, for example, be a hydraulic or electric
motor.
[0041] FIG. 3 shows an alternative arrangement in which the shaft
is split into first and second shafts each actuated by a respective
motor and each moving a respective one of the two flaps. In FIG. 3,
the motors, shafts, support, rollers and wires have the same
references as in FIG. 2 with the addition of the suffix `r` or `t`
to denote whether they are the tip (t) or root (r) and assembly.
Further shafts and motors could be added to control additional
flaps (not shown). From a maintenance perspective, this arrangement
is less preferred than that of FIG. 2 as the location of the motor
for the tipwards flap is inconvenient and inaccessible for
servicing. The embodiment of FIG. 2 has the advantage that the
single motor is easily accessible at the root end of the block
making access for service and maintenance straightforward.
[0042] In order to deploy the flaps, the actuator(s) may only need
to rotate the torsion shaft through a portion of a rotation, for
example, 1/3 of a turn.
[0043] The actuator shaft 32 is preferably torsionally stiff but
otherwise non-stiff enabling it to follow blade movement over the
lifetime of the blade which may be 20 years or more. The shaft is
preferably made from a composite material.
[0044] Thus, in the embodiment described, rotary movement of the
shaft by the actuator causes movement of the flap. In particular,
shaft rotation causes the flap to pivot about the hinge line.
[0045] As mentioned previously, in the embodiment of FIGS. 1 to 3,
the flap or flaps are biased towards the extended position. It will
now be appreciated that this is necessary for the control wire
arrangement to work. FIG. 4 shows one possible spring arrangement
in which a block of shaped compressible rubber 42 or other suitable
material is arranged beneath the hinge line between a rear wall of
the blade and the rear wall of the flap. The block may be a rubber
foam element. The compressed rubber 42 acts to bias the flap
towards the extended position. Any other suitable spring could be
used, such as a leaf spring or a compression spring.
[0046] FIG. 5 shows an alternative arrangement for the control
linkage which connects the shaft to the flap. In this embodiment,
the flap is still biased outwards by a spring, but this is no
longer essential as the link between the shaft and the flap is
rigid. A spring is still preferred to eliminate flutter and to
ensure a low lift coefficient fail safe position. A push rod 44 is
connected at the bottom of the rear wall 46 of the flap at
essentially the same location as the control wire of FIG. 1.
However, as the control linkage is rigid, the roller 40 is replaced
by a crank arm 48 which is mounted at one end for rotation on the
shaft and at another end is coupled to the rigid linkage 44 such
that rotation of the shaft translates to reciprocal movement of the
push rod or rigid linkage.
[0047] In the preceding embodiments, the flaps have been hinged
about a hinge line on the suction surface of the blade and flap.
FIG. 6 shows an alternative arrangement in which the hinge line 50
is along a midpoint of the height of the flap such that the flap is
free to move towards both the pressure and suction sides of the
blades. In view of this movement, the rear wall 46 of the flap 26
has an upper section 52 that slopes from the hinge line away from
the blade towards the trailing edge and a similar lower section 54.
The flap is actuated by a double crank arm 56 which is coupled at
its centre to the shaft for rotation with the shaft 32. Each of the
ends of the double crank arm 56 are connected to a control linkage,
here shown as a control wire 38, the other end of which is
connected to the upper and lower rear wall sections of the flap
respectively. Thus, rotation of the actuator shaft in a clockwise
direction will cause the flap to move towards the pressure side,
whereas counter clockwise rotation of the shaft will cause the flap
to move towards the suction side. As the control members are
non-rigid wires, a spring (not shown) such as the shaped compressed
rubber foam block of previous embodiments is required to bias at
least one of the two flap connections. The spring may be arranged
between the rear wall section of the flap or between the blade rear
wall and the upper rear wall section of the flap, or between both
rear wall sections.
[0048] Alternatively, the coupling wires of FIG. 6 could be
replaced by rigid linkages as used in FIG. 5 removing the need for
biasing springs although these may be desirable.
[0049] This embodiment has the advantage of reduced slack in the
system, but the torsion arm, being the distance between the pull
point on the flap and the hinge is halved.
[0050] In the embodiments of FIGS. 1 to 6, the actuator shaft is
arranged along the length of the spar or beam 16, essentially along
the neutral line of the blade as this position is the least likely
to give rise to fatigue problems caused by constant rotation of the
blade over years of operation. While this is desirable, it is also
highly desirable to be able to gain access to moving parts of the
blade easily for repair and maintenance.
[0051] In the embodiment of FIG. 7, the shaft is located in a
separate detachable unit or section 60 which includes the flap 26
or flaps. Where the blade has multiple flaps, a separate shaft
arrangement may be provided for each flap such that each flap forms
a separate detachable section to reduce the size of the detachable
sections. In the Figure, the arrangement shown is that of the
control wire and roller described with respect to FIG. 1. However,
any of the other arrangements described above could be used. In the
arrangement shown in FIG. 7, the shaft supports 34 are mounted on a
wall 62 of the detachable section that abuts the blade when the
section is in place. The actuators 36 which drive the flap
actuating shaft or shafts may be controlled by a separate
controller, or more preferably by the main wind turbine controller
which controls various turbine parameters such as rotor speed and
blade pitch angle. A main control parameter for the flaps is to
reduce loading on the blade and the flap system as it rotates to an
optimal condition. FIG. 8 shows a plot of actuation frequency
against flap amplitude for two different load cases identified as
70 and 72. Both cases have a component of the 1P actuation
frequency (around 0.2 Hz) but are different in the higher response
rates due to their operational conditions. The actuation frequency
1P corresponding to one flap movement per rotor rotation is
predominant and is caused by issues such as wind gradient, yaw
error and other variables which depend on blade position. It can be
seen from the figure that a very substantial part of the optimal
control of the flap system can be achieved by adjusting the flaps
one per revolution of the blade. This frequency, which is roughly
0.2 Hz makes the arrangements of the embodiments described
extremely practical and can easily provide the desired frequency of
movement of the flaps. However, although this arrangement may
achieve the majority of the benefit available, for example, up to
70% of a maximum achievable, there are still large and significant
gains which can be obtained by actuation the flaps much more
frequently, for example, 10 times faster. The arrangements of FIGS.
1 to 7 are not necessarily optimised for a frequency of actuation
that is that high, while maintaining 20 years service free life
time. Moreover, at faster actuation speeds, it may be desirable to
actuate flaps individually and it may also be easier to actuate
flaps individually in view of their large size. FIGS. 9 and 10
illustrate modifications of the embodiments of FIGS. 1 to 7 which
enable faster movements of the flaps. In each of the embodiments
the low frequency movement of the flaps, once per revolution, is
maintained and a higher frequency offset component added.
[0052] FIG. 9 is an enlarged view of the shaft and linkage
arrangement shown in FIGS. 1 to 7. The blade shell and the flap
have been removed for simplicity and ease of understanding. The
shaft 32 is shown supported on beam 16 by supports 34 with crank
arm 48 arranged to rotate with the shaft. An L-shaped crank 74 is
arranged to rotate freely about the shaft and is connected at one
end 76 to the linkage, here shown as push rod 44 but alternatively
a control wire as in earlier embodiments. The other end 78 of the
L-shaped crank is coupled to the free end of the crank arm 48 by a
fast actuator 80. This actuator can impart movement to the L-shaped
crank relative to the crank arm 48 and may be, for example, a
piezo-electric stack. Higher frequency signals may be sent to the
piezo-electric stack from the turbine controller or a dedicated
flap controller to excite the stack and thus move the L-shaped
crank, relative to the crank arm 48 and the shaft, so imparting
additional movement to the linkage 44 and through it to the flap
(not shown).
[0053] In FIG. 9, the leftmost straight double headed arrow 82
indicates that the majority of movement of the linkage is slow
movement (once per revolution) from rotation of the shaft whereas
the right hand double headed arrow 84 indicates a smaller component
of addition fast movement from the offset actuator comprising the
L-shaped crank and the piezo-electric stack.
[0054] Thus, this embodiment provides an offset to the movement
provided by rotation of the shaft and the crank arm (or roller). It
will be appreciated that separate L-shaped cranks and
piezo-electric stacks may be provided for each flap and, as the
stacks are controlled individually, the fast moving offset movement
may be applied separately to each flap.
[0055] The arrangement of FIG. 9 is preferred for a rigid control
linkage and crank arm arrangement. An alternative arrangement is
shown in FIG. 10 which is presently preferred for the roller and
wire linkage of FIG. 1. In this embodiment, the roller 40 can be
driven by rotation of the shaft 32 and additionally by a fast
movement motor 86 that imparts movement to the roller through an
offset gear 88. This gear may mesh with a splined inner surface of
the roller (not shown) to impart movement. The motor 86 is fixed to
the rod 32 and drives the gear 88. The gear in turn drives the
roller or drum 40 to provide fast, but small movements of the wire
38.
[0056] As with the previous embodiment, the fast movement motor may
be individual to each flap enabling the offset movement to be
applied to each flap individually. The extent of movement provided
by the shaft rotation is indicated by double headed arrow 90 and
that provided by the offset motor and gear is indicated by double
headed arrow 92. The speed of actuation may be increased by using
spiral splines on the shaft combined with axial movement of the
shaft.
[0057] Embodiments of the invention have the advantage of providing
a simple control mechanism for the flap or flaps on a wind turbine
blade, for example, on the trailing edge. The use of a motor
actuated shaft enables the motor to be located towards the root of
the blade making inspection and maintenance easy and locates the
motor relatively close to the turbine controller in the turbine
nacelle which is desirable. Moreover, some embodiments of the
invention enable movement to be imparted to multiple flaps through
a single motor and also additional offset movements to be imparted
to individual flaps to provide higher frequency movement.
* * * * *