U.S. patent application number 14/840024 was filed with the patent office on 2017-03-02 for self-tuning tunable mass dampers.
The applicant listed for this patent is The Boeing Company. Invention is credited to Steven F. Griffin, Daniel Niedermaier.
Application Number | 20170058984 14/840024 |
Document ID | / |
Family ID | 56134106 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170058984 |
Kind Code |
A1 |
Griffin; Steven F. ; et
al. |
March 2, 2017 |
SELF-TUNING TUNABLE MASS DAMPERS
Abstract
A tunable mass damper incorporates a frame and a voice coil
supported in the frame. A magnet concentric with the voice coil is
movable relative to the housing via the voice coil. A plurality of
flexures having a first end extending from the magnet and an arm
releasably coupled to the frame are adjustable to an effective
length for a desired frequency of reciprocation of the magnet.
Inventors: |
Griffin; Steven F.; (Kihei,
HI) ; Niedermaier; Daniel; (League City, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Boeing Company |
Chicago |
IL |
US |
|
|
Family ID: |
56134106 |
Appl. No.: |
14/840024 |
Filed: |
August 30, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16F 7/1011 20130101;
F16F 7/116 20130101; E04H 9/027 20130101; F16F 7/104 20130101; E04H
9/0215 20200501; B64C 7/00 20130101 |
International
Class: |
F16F 7/10 20060101
F16F007/10; E04B 1/98 20060101 E04B001/98; B64C 7/00 20060101
B64C007/00; E04H 9/02 20060101 E04H009/02; F16F 7/104 20060101
F16F007/104 |
Goverment Interests
REFERENCE TO GOVERNMENT FUNDING
[0001] This invention was made with Government support under
contract number ______ TBD ______ awarded by NASA. The government
has certain rights in this invention.
Claims
1. A tuned mass damper comprising: a frame, a voice coil supported
in the frame; a magnet concentric with the voice coil and movable
relative to the via the voice coil; and, a plurality of flexures
having a first end extending from the magnet and an arm releasably
coupled to the frame, each flexure incorporating a slot in the arm,
said slot receiving a pin supported from the frame said pin
positionable in the slot for adjustment of an effective length of
said flexure said flexures adjustable for a desired frequency of
reciprocation of the magnet.
2. (canceled)
3. The tuned mass damper as defined in claim 2 further comprising:
first ramps attached to the magnet which when moved in a first
direction engage first guide elements to cause the magnet and
flexural members to rotate in a clockwise direction; second ramps
attached to the magnet which when moved in a second direction
engage second guide elements to cause the magnet and flexural
members to rotate in a counter-clockwise direction.
4. The tuned mass damper as defined in claim 3 further comprising:
at least one clamp actuated by a solenoid on at least one flexural
member and configured to allow the magnet and flexural members to
rotate when the solenoid is in a first state, and to clamp the
flexural members in a fixed position when the solenoid is in a
second state, wherein rotation in the first direction lengthens the
effective length of the flexural members and rotation in the second
direction shortens the effective length of the flexural members,
such that the tuned mass damper frequency is adjustable by changing
the effective length of the flexure members.
5. The tuned mass damper as defined in claim 4 further comprising
at least one accelerometer disposed on the magnet.
6. The tuned mass damper as defined in claim 5 further comprising a
control system having encoded instructions therein for calculating
an optimum frequency range based on input from the at least one
accelerometer, the control system configured to activate the at
least one solenoid actuated clamp and control the voice coil to
rotate the magnet to adjust the flexural members to an effective
length corresponding to the calculated frequency.
7. The tuned mass damper as defined in claim 6, wherein the control
system is configured to analyze a frequency band that includes more
than one lightly damped resonance frequency and determine an
optimum frequency and damping to minimize the effect of
vibration.
8. The tuned mass damper of claim 7, further comprising a variable
resistance in series with the voice coil, said variable resistance
responsive to the control system to adjust the damping of the tuned
mass damper.
9. The tuned mass damper as defined in claim 6 further comprising a
tether removably connecting the control system to the voice coil
and the at least one accelerometer.
10. The tuned mass damper as defined in claim 4 wherein the
solenoid is powered for activation in the first state and
deactivated in the second state whereby the clamp is engaged in a
failure condition of the solenoid.
11. A method for operation of a tunable mass damper (TMD)
comprising: attaching at least one TMD to a structure, the TMD
having a voice coil and concentric magnet as a moving mass
supported by flexures to a host structure at a location with an
anticipated large dynamic response; releasing flexure clamps;
adjusting flexure length on the TMD by using the voice coil to urge
the magnet and associated ramps into contact with bearing guides to
rotate the magnet and flexures to obtain a desired frequency of the
TMD; reclamping the flexures for operation of the TMD.
12. The method as defined in claim 11 further comprising: adjusting
the flexure length by using the voice coil to urge the magnet and
ramps into contact with the bearing guides to adjust the frequency
of the TMD below the frequency band of interest; reclamping the
flexures; actuating the voice coil as a shaker; measuring the
resulting uncoupled host transfer function; and, employing the
uncoupled host transfer function and a predetermined tuning logic
to determine a preferred TMD frequency and damping.
13. The method as defined in claim 12 further comprising:
activating the voice coil as the shaker; measuring the resulting
coupled host transfer function with the accelerometers to compare
to the predicted transfer function; and repeating the steps of
adjusting flexure length, activating the voice coil as a shaker and
measuring the resulting coupled host transfer function to obtain a
desired frequency of the TMD until a convergence criteria is
satisfied.
14. The method as defined in claim 13 further comprising attaching
a tether to the TMD to provide power to the voice coil and
solenoids and to receive signals from accelerometers mounted on the
TMD frame, magnet and host structure.
15. The method as defined in claim 14 further comprising removing
the tether from the TMD for autonomous operation pf the TMD for
dynamically damping the host structure.
16. The method as defined in claim 14 further comprising altering
voltage on a digitally programmable analog resistor across the
voice coil to set a desired damping.
17. The method as defined in claim 12 wherein the at least one TMD
comprises a plurality of TMDs and the step of activating the voice
coil comprises activating the voice coil of a selected one of the
TMDs as a shaker, the step of measuring the resulting uncoupled
host transfer function comprises measuring the resulting uncoupled
host transfer function for each of the TMDs, the steps of releasing
the flexure clamps, adjusting the flexure length and reclamping the
flexure clamps are performed for each TMD.
18. A structural damping system comprising: a host structure having
a location with anticipated high dynamic response; at least oneTMD
having a frame mounted to the host structure at the location; a
voice coil supported in the frame; a magnet concentric with the
voice coil and movable relative to the frame via the voice coil; a
plurality of flexures having a first end coupled to the magnet and
an arm releasably coupled to the frame, said flexures adjustable
for a desired frequency of reciprocation of the magnet; at least
one accelerometer attached to the voice coil; a control system
having encoded instructions therein for calculating an optimum
frequency range based on input from the at least one accelerometer,
the control system configured to control the voice coil to rotate
the magnet to adjust the flexural members to an effective length
corresponding to the calculated frequency.
19. The structural damping system as defined in claim 18, wherein
the control system is configured to analyze a frequency band that
includes more than one lightly damped resonance frequency and
determine an optimum frequency and damping to minimize the effect
of vibration.
20. The structural damping system as defined in claim 18 wherein
each flexure incorporates a slot in the arm, said slot receiving a
pin supported from the frame said pin positionable in the slot for
adjustment of an effective length of said flexure further
comprising: first ramps attached to the magnet which when moved in
a first direction engage first guide elements to cause the magnet
and flexural members to rotate in a clockwise direction; second
ramps attached to the magnet which when moved in a second direction
engage second guide elements to cause the magnet and flexural
members to rotate in a counter-clockwise direction; at least one
clamp actuated by a solenoid on at least one flexural member and
configured to allow the magnet and flexural members to rotate when
the solenoid is in a first state, and to clamp the flexural members
in a fixed position when the solenoid is in a second state, wherein
rotation in the first direction lengthens the effective length of
the flexural members and rotation in the second direction shortens
the effective length of the flexural members, such that the tuned
mass damper frequency is adjustable by changing the effective
length of the flexure members.
21. The structural damping system as defined in claim 18 where in
the at least one TMD comprises a plurality of TMDs.
Description
BACKGROUND INFORMATION
[0002] Field
[0003] Embodiments of the disclosure relate generally to the field
of damping of dynamic resonance in aerospace structures and more
particularly to a tuned mass damper (TMD) employing a voice
coil/magnet combination as both an actuator and a lossy element for
measuring and adjusting the TMD and structural response in an
aerospace structure to which the TMD is attached and then adjusting
the lossy element to self-tune the TMD for maximum reduction in
dynamic response of the aerospace structure and TMD
combination.
[0004] Background
[0005] Tuned mass dampers (TMDs) are heavily damped resonant
devices which add damping to lightly damped vibrational modes of a
structure by dynamically coupling into the lightly damped modes. In
practice, a TMD is a damped spring/mass resonator that is tuned so
that its frequency is close to a lightly damped mode on the host
structure. The TMD is attached to the host structure at a location
of large amplitude motion for the mode in question and its motion
is coupled into the host structure's motion. If the TMD is tuned
correctly, two damped vibrational modes result, which take the
place of the original lightly damped mode of the host structure and
heavily damped mode of the TMD. Since aerospace structures tend to
respond unfavorably at lightly damped modes in the presence of a
dynamic disturbance environment, introduction of one or several
TMDs can greatly reduce the dynamic response of a structure by
damping problematic modes.
[0006] One of the challenges associated with installation of TMDs
is tuning. Tuning involves the determination of the correct values
of uncoupled natural frequency and damping for the device that
yields the best performance in the coupled device. Finite element
models are helpful in predicting the host structure dynamics, which
can then be used to determine the frequency, damping and mass of
the TMD that gives the best performance, but the finite element
model has to be very accurate to be useful. Measured mode shapes of
the structure without TMDs can also be used to determine the
frequency, damping and mass of the TMD that gives the best
performance. A typical installation involves using a finite element
model to determine the moving mass in the TMD and the range of
damping and frequencies required. Experimental data is then used to
"tune" the frequency, damping and mass to the values that cause the
biggest response reduction in host structure response. This process
is often tedious and requires several iterations.
[0007] It is therefore desirable to provide a self-tuning TMD to
eliminate the tuning step, save time and result in better overall
performance for damping to reduce the dynamic response of a
structure by damping problematic modes.
SUMMARY
[0008] Embodiments disclosed herein provide a tunable mass damper
having a frame and a voice coil supported in the frame. A magnet
concentric with the voice coil is movable relative to the housing
via the voice coil. A plurality of flexures having a first end
extending from the magnet and an arm releasably coupled to the
frame, said flexures adjustable for a desired frequency of
reciprocation of the magnet.
[0009] A method for operation of a tunable mass damper includes
attaching a TMD having a voice coil and concentric magnet as a
moving mass to a host structure at a location with an anticipated
large dynamic response. Flexure clamps are released and flexure
length is adjusted on the TMD by using the voice coil to urge the
magnet and associated ramps into contact with bearing guides to
rotate the magnet and flexures to obtain a desired frequency of the
TMD. The flexures are then reclamped for operation of the TMD.
[0010] The features, functions, and advantages that have been
discussed can be achieved independently in various embodiments of
the present disclosure or may be combined in yet other embodiments
further details of which can be seen with reference to the
following description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1A is a perspective illustration of an exemplary
embodiment of the TMD;
[0012] FIG. 1B is a side view of the embodiment of FIG. 1A;
[0013] FIG. 1C is a top partial cutaway view of the embodiment of
FIG. 1A;
[0014] FIG. 2A is a side view of the TMD with the voice coil
powered to engage the lower adjustment ramp for decreasing flexure
length;
[0015] FIG. 2B is a side view of the TMD with the voice coil
powered to engage the upper adjustment ramp for increasing flexure
length;
[0016] FIG. 3A is a top partial cutaway view of the TMD with the
flexures rotated to substantially a maximum length;
[0017] FIG. 3B is a top partial cutaway view of the TMD with the
flexures rotated to substantially a minimum length;
[0018] FIG. 4 is a block diagram of a control system for the TMD;
and,
[0019] FIG. 5 is a flow chart depicting an exemplary method for
adjustment and operation of the TMD.
DETAILED DESCRIPTION
[0020] Embodiments disclosed herein provide a TMD having a
resilient element such as a spring, a moving mass and a lossy
element to introduce damping. The spring is designed to guide the
motion of the TMD for reciprocation on a desired axis through the
TMD. If a shorted voice coil combined with a magnet is used as the
lossy element, an added benefit can be realized by changing the
resistance across the coil to change the damping. TMDs with voice
coil loss mechanisms are commercially available from CSA/Moog
(http://www.csaengineering.com/products-services/tuned-mass-dampers-absor-
bers/tmd-products/). The self-tuning TMD disclosed in the present
embodiment uses the voice coil/magnet combination as both an
actuator and a lossy element which enables an innovative stiffness
adjustment mechanism.
[0021] The basic components of the self-tuning TMD are shown in
FIGS. 1A-1C. A voice coil 10 with a core 12 is supported in a frame
14. For the embodiment shown, the frame employs a top flange 15a
and a bottom flange 15b spaced apart and connected by columns 15c.
While shown for the embodiment in the drawings as an open frame, a
closed housing may be employed in alternative embodiments. A magnet
16, supported by resilient elements formed by semi-helical flexures
18a and 18b, concentrically surrounds the coil 10 and is movable
relative to the housing via the voice coil 10. The magnet 16
provides the moving mass for the TMD that reciprocates
concentrically on an axis 20. The flexures 18a and 18b are
supported by pillars 20 extending from the frame 14. The plurality
of flexures have a first end extending from the magnet 16 and an
arm 19 releasably coupled to the frame 14. For the embodiment
shown, the flexures 18a and 18b each have three symmetrical arms
19. In alternative embodiments the flexures may be supported by
various attachments on the columns 15c replacing the pillars 20 and
alternative numbers of arms and associated pillars may be employed
for the flexures to support magnet 16.
[0022] The voice coil 10 can be actively powered and used to move
the magnet 16 up or down from the neutral position shown in FIG.
1B. A large voltage applied to the voice coil by a control system,
to be described in greater detail subsequently, pushes magnet 16
axially to engage bearing race ramps 22a or 22b, which are attached
to the magnet 16, against bearing guides 24a or 24b, which are
attached to the frame 14. Axial engagement of the ramps and guides
causes rotation of the magnet 16. Rotation of the magnet 16 causes
rotation of the attached flexures 18a and 18b. If the magnet 16 is
pushed downwardly in the depiction in the drawings as shown in FIG.
2A, contact between the bearing race ramps 22b and the bearing
guides 24b force the magnet to turn in a counter clockwise
direction. If the magnet 16 is pushed upwardly in the depiction in
the drawings as shown in FIG. 2B, contact between the bearing race
ramps 22a and bearing guides 24a force the magnet to turn in a
clockwise direction. The flexures 18a and 18b, which resiliently
support the magnet 16 with respect to the frame 14, incorporate
arcuate slots 26 which are substantially concentric around axis 20
and engage pins 28 extending from the pillars 20. The pins 28 are
received within the slots 26, and each pin is positionable in the
slot 26 for adjustment of an effective length of said flexure 18.
Normally closed solenoids 30 lock down clamps 31 to secure the
flexures when no voltage is applied and release the clamps when a
voltage is applied. When the solenoids are locked, the flexures 18a
and 18b are locked at a selected position along the slots 26 which
centers the magnet and allows it to vibrate relative to the voice
coil 10. The natural or resonant frequency of the vibration of the
magnet mass in the TMD can be changed through changing the
effective length of the flexures 18a and 18b by positioning the
pins 28 and clamps 31 with respect to the slots 26. A clockwise
motion of the magnet 16 lengthens the flexure along a range of the
slots 26 terminating at a distal end 32 as shown in FIG. 3A, where
a counter clockwise motion of the magnet 16 shortens the flexure
along the range of the slots terminating at a proximal end 34 as
shown in FIG. 3B. Clockwise rotation may be enabled via first ramps
22a attached to the magnet 16, which when moved in a first
direction engage first guide elements 24a to cause the magnet 16
and flexural members 18a, 18b to rotate in a clockwise direction.
Counterclockwise rotation may be enabled via second ramps 22b
attached to the magnet 16, which when moved in a second direction
engage second guide elements 24b to cause the magnet 16 and
flexural members 18a, 18b to rotate in a counter-clockwise
direction. A clamp 31 is actuated by a solenoid 30 to clamp on at
least one flexural member, and is configured to allow the magnet 16
and flexural members 18a, 18b to rotate when the solenoid is in a
first state, and to clamp the flexural members in a fixed position
when the solenoid is in a second state. The solenoid 30 may be
powered for activation in the first state, and deactivated in the
second state whereby the clamp is engaged in a failure condition of
the solenoid. Accordingly, rotation in the first direction
lengthens the effective length of the flexural members and rotation
in the second direction shortens the effective length of the
flexural members, such that the tuned mass damper frequency is
adjustable by changing the effective length of the flexure members.
The frequency is adjustable over a range based on the location of
the clamps 31 and pins 28 in the slots 26. When a large voltage is
applied to the actuator to clock the magnet 16, a voltage is also
applied by the control system to the solenoids 30 releasing the
clamps 31 to allow sliding of the flexures relative to the pins 28
supported by the pillars 20.
[0023] The damping of the TMD can be changed by varying resistance
across the voice coil 10 using, for example, a digitally
programmable analog resistor. Increasing the resistance makes the
inductive interaction between the voice coil 10 and magnet 16 more
lossy while decreasing the resistance makes the interaction less
lossy. A control system as shown in FIG. 4 may be employed to
actively control the voice coil 10 for clocking the magnet 16 to
alter the resonant frequency of the TMD or to cause excitation of
the magnet allowing the TMD to act like a shaker or a modal hammer.
A control computer 402 employs control algorithms to act on inputs
received through an control interface 403 which may include an
analog to digital (A/D) and digital to analog (D/A) interface 404
and provides control output through a voice coil amplifier 406 to
actively position or drive the voice coil 10 as previously
described. The control system may include encoded instructions
therein for calculating an optimum frequency range based on input
from the at least one accelerometer. The control system is
configured to activate the at least one solenoid actuated clamp 31
and control the voice coil 12 to rotate the magnet to adjust the
flexural members 18a, 18b to an effective length corresponding to
the calculated frequency. A solenoid amplifier 408 is connected to
the control computer 402 to controllably release the solenoids 30
an associated clamps 31 as previously described. Various signal
conditioning components 410 may also be employed. A removable
tether 412 couples the control system components to the TMD 400
with connections to the solenoids 30 and voice coil 10 and
additional connection to at least one accelerometer 414 on the host
structure 416, at least one accelerometer 418a associated with the
magnet 16 and at least one accelerometer 418b mounted to the frame
14. Data from the accelerometers is processed through the signal
conditioning elements 410 and A/D in the A/D & D/A interface
404. A control connection in the tether 412 to a variable resistor
420, which is connected across the voice coil 10, allows adjustment
of the lossy characteristics of the TMD under control of the
control computer 402 through the D/A in the A/D & D/A interface
404.
[0024] Given a frequency band of interest associated with the host
structure, the self-tuning TMD can be adjusted to a selected test
frequency well below the lowest frequency in the band and measure a
collocated transfer function between current into the voice coil
and acceleration of the base. A current mode amplifier as one of
the signal conditioning elements 410 would be required.
Alternatively, a transfer function between voltage into the voice
coil and the acceleration of the base could be used, however, this
transfer function will be affected by addition of some damping
through back EMF. The transfer function selected will give insight
into the uncoupled behavior of the host structure and may be used
as the starting point for an algorithm to tune the TMD. The
measured transfer function will show lightly damped modes that are
good candidates for damping to reduce the host structure response.
The control system is configured to analyze a frequency band that
includes more than one lightly damped resonance frequency and
determine an optimum frequency and damping to minimize the effect
of vibration. This technique may also be applied with multiple TMDs
(shown as elements 400 with associated interfaces 403 in FIG. 4)
mounted to the structure with at least one TMD connected for
driving the voice coil as an actuator. With all of the TMDs tuned
to the selected test frequency, the accelerometers in all TMDs
could then be sampled to collect response data and the
determination by the control system may be made for optimization of
all of the TMDs to reduce response to a disturbance at or near the
TMD which was driven as the actuator. Each TMD may then be adjusted
using the voice coil to clock the magnets in each TMD as described
above and the control computer may adjust the programmable
resistance for each TMD to provide the desired response.
[0025] As shown in FIG. 5, a self-tuning TMD having the structure
of the described embodiment is attached to a host structure at a
location with an anticipated large dynamic response, step 502. A
tether is then attached to at least one TMD to provide power to the
voice coil and solenoids and to receive signals from accelerometers
mounted on the TMD frame, magnet and host structure, step 504. A
control system is employed to release the flexure clamps and the
TMD is adjusted by using the voice coil to urge the magnet and
ramps into contact with the bearing guides to adjust the frequency
of the TMD below the frequency band of interest and reclamp the
flexures, step 506. The control system then actuates the voice coil
as a shaker and measures the resulting uncoupled host transfer
function, step 508. The uncoupled host transfer function and a
predetermined tuning logic are employed to determine a preferred
TMD frequency and damping, step 510. The control system is then
employed to again release the flexure clamps and the TMD is
adjusted by using the voice coil to urge the magnet and ramps into
contact with the bearing guides to adjust flexure length to obtain
the desired frequency of the TMD and reclamp the flexures, step
512. The control system them alters voltage on a digitally
programmable analog resistor across the voice coil to set the
desired damping, step 514. The control system may then again
activate the voice coil as a shaker and measure the resulting
coupled host transfer function with the accelerometers to compare
to the predicted transfer function, step 516. Steps 506 through 516
may then be repeated until a convergence criteria is satisfied,
step 518. The tether is then removed from the TMD, step 520 and the
TMD is ready for autonomous operation for dynamically damping the
host structure. While the steps herein are described with respect
to at least one TMD, a plurality of TMDs may be connected,
activated, measured and tuned as a group to be optimized for
desired damping of the structure to which the TMDs are attached as
previously described. A single TMD of the plurality may be
activated as the shaker while all TMDs in the plurality may be
measured and tuned.
[0026] Having now described various embodiments of the disclosure
in detail as required by the patent statutes, those skilled in the
art will recognize modifications and substitutions to the specific
embodiments disclosed herein. Such modifications are within the
scope and intent of the present disclosure as defined in the
following claims.
* * * * *
References