U.S. patent application number 11/520496 was filed with the patent office on 2007-04-19 for method to sense airflow by measuring torque on the damper shaft.
Invention is credited to Dean B. Anderson, Matthew D. Cook.
Application Number | 20070087681 11/520496 |
Document ID | / |
Family ID | 37948724 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070087681 |
Kind Code |
A1 |
Cook; Matthew D. ; et
al. |
April 19, 2007 |
Method to sense airflow by measuring torque on the damper shaft
Abstract
A damper assembly includes a damper frame, at least one damper
blade, an actuator and a sensor module coupled to a first rotatable
damper element. The one or more damper blades are movably attached
to the damper frame to at least partially regulate air flow
proximate the damper frame. The actuator is configured to control a
position of the damper blade. The rotatable damper element is
operably coupled between the actuator and the damper blade. The
sensor module includes a sensor device operable to determine an
air-flow induced force on the rotatable damper element.
Inventors: |
Cook; Matthew D.; (Antioch,
IL) ; Anderson; Dean B.; (Wonder Lake, IL) |
Correspondence
Address: |
SIEMENS CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
170 WOOD AVENUE SOUTH
ISELIN
NJ
08830
US
|
Family ID: |
37948724 |
Appl. No.: |
11/520496 |
Filed: |
September 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60716876 |
Sep 13, 2005 |
|
|
|
Current U.S.
Class: |
454/256 |
Current CPC
Class: |
F24F 11/30 20180101;
F24F 2110/00 20180101; F24F 2110/30 20180101; F24F 11/74
20180101 |
Class at
Publication: |
454/256 |
International
Class: |
F24F 11/00 20060101
F24F011/00 |
Claims
1. A damper assembly comprising: a damper frame; at least one
damper blade movably attached to the damper frame to at least
partially regulate air flow proximate the damper frame; an actuator
configured to control a position of the at least one damper blade;
at least one rotatable damper element operably coupled between the
actuator and the at least one damper blade; and a sensor module
coupled to a first of the at least one rotatable damper element,
the sensor module including a sensor device operable to determine
an air-flow induced force on the first rotatable damper
element.
2. The damper assembly of claim 1, wherein the sensor module
further includes a first wireless communication circuit operable to
communicate air-flow induced force information to a second wireless
communication circuit disposed off of the first damper element.
3. The damper assembly of claim 2, wherein the first wireless
communication circuit includes an RF communication device.
4. The damper assembly of claim 1, wherein the sensor device
comprises a strain gauge.
5. The damper assembly of claim 4, wherein the sensor device
comprises a microelectromechanical systems strain gauge.
6. The damper assembly of claim 1, wherein the sensor device
comprises a microelectromechanical systems sensor.
7. The damper assembly of claim 2, wherein the air-flow induced
force information comprises air flow information derived from force
measurements.
8. The damper assembly of claim 7, wherein the actuator is
configured to control a position of the at least one damper blade
based at least in part on the air flow information.
9. The damper assembly of claim 2, wherein the actuator is
configured to control a position of the at least one damper blade
based at least in part on the air-flow induced force
information.
10. The damper assembly of claim 1, wherein the sensor module
further comprises a processing circuit operable to generate air
flow information based on the air flow induced force
information.
11. The damper assembly of claim 10, wherein the sensor module
further comprises a processing circuit operable to generate air
flow information further based on damper position information.
12. A sensor module, comprising: a MEMs sensor device operable to
determine an air-flow induced mechanical force on a first damper
element; and a processing circuit operably coupled to receive
air-flow induced mechanical force information based on the
determined air-flow induced mechanical force, the processing
circuit operable to generate an air flow measurement value based on
the air-flow induced mechanical force information and position
information representative of a position of a damper coupled to the
first damper element.
13. The sensor module of claim 12, wherein the processing circuit
is operable to generate the air flow measurement value based on the
air-flow induced mechanical force information and the position
information representative of the position of the damper, the
damper being mechanically coupled to the first damper element.
14. The sensor module of claim 12, further comprising a first
wireless communication circuit operable to communicate information
representative of the air flow measurement to a second wireless
communication circuit.
15. The sensor module of claim 14, wherein the first wireless
communication circuit includes an RF communication device.
16. The sensor module of claim 12, wherein the sensor device
comprises a strain gauge.
17. A sensor module, comprising: a MEMs sensor device operable to
determine an air-flow induced mechanical force on a first damper
element; a processing circuit operably coupled to receive air-flow
induced mechanical force information based on the determined
air-flow induced mechanical force, the processing circuit operable
to generate an air flow measurement value based on the air-flow
induced mechanical force information; and a first wireless
communication circuit operable to communicate information
representative of the air flow measurement to a second wireless
communication circuit.
18. The sensor module of claim 17, wherein the processing circuit
is operable to generate the air flow measurement value based on the
air-flow induced mechanical force information and position
information representative of a position of a damper, the damper
being mechanically coupled to the first damper element.
19. The sensor module of claim 17, wherein the first wireless
communication circuit includes an RF communication device.
20. The sensor module of claim 17, wherein the sensor device
comprises a strain gauge.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/716,876, filed Sep. 13, 2005, and
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to damper blades used for
controlling air flow.
BACKGROUND OF THE INVENTION
[0003] Ventilation dampers are devices that are used to control the
flow of air into ventilation ducts, rooms, or other spaces of a
building or facility. For example, a ventilation damper may control
the flow of cool air in to a room. In other examples, a ventilation
damper may control the amount of exhaust air from a room, and/or
the amount of recirculated and fresh air that is provided
throughout a building. Ventilation dampers are movable such that
they may be further opened or closed in order to increase or
decrease, respectively, the flow of air through the damper assembly
device. In building control systems, damper assembly devices are
also known as variable-air-volume (VAV) diffusers or VAV units.
[0004] One example of a VAV unit and its operation is set forth in
U.S. Pat. No. 6,581,847, which is incorporated herein by reference.
The VAV unit of U.S. Pat. No. 6,581,847 teaches the control of room
temperature using a VAV unit to vary the volume of supply air
discharged into a room. The supply air is heated when the VAV unit
is in a heating mode and is cooled when the system is in cooling
mode. The supply air is usually provided at substantially a
constant temperature in each mode. A VAV unit regulates the volume
of heated or cooled supply air in order to achieve and maintain a
desired room air temperature. To this end, a controlled actuator
device operates to open or close a set of louvers or ventilation
dampers to increase or decrease to flow of supplied air.
[0005] Typical controlled actuator devices include
thermally-powered actuators, pneumatically-powered actuators, and
electrically powered actuators. All three types of actuators are
coupled to the ventilation dampers by a mechanical linkage, gear
assembly levers and/or combinations of these and other mechanical
couplings. The actuator performs controlled movements which are
translated by the mechanical couplings to changes in the positions
of the dampers.
[0006] Control units for VAV units preferably maintain accurate
information regarding the current position of the dampers. Accurate
position information is useful for various reasons, including
effective control and reliability. Inaccurate position information
can even result in damage to a VAV unit. In one example, if a
damper is fully open, and the position information indicates that
the damper is not fully open, then the control mechanism may
attempt to further open the damper. The attempt to further open the
damper that is already fully open is both inefficient and
potentially harmful to the equipment.
[0007] In addition, damper blades often have associated flow
sensors to determine the actual flow of air through the damper.
Ultimately, it is the flow of air that is to be controlled, and
thus information regarding the flow of air through the damper
provides feedback which may be used to determine whether the
dampers should be further opened, or further closed. However, air
flow sensors, typically require several parts including
differential pressure sensor elements, tubing and pickups. These
elements contributed to the cost of both the damper itself, and to
the cost of installation as several parts must be added and then
wired.
[0008] Accordingly, there is a need for damper or louver
arrangements with improvements in air flow sensing technology.
SUMMARY
[0009] The present invention addresses the above-described needs,
as well as others, by providing a torque sensor module coupled
directly to a rotating shaft of the damper assembly. Preferably,
the sensor module includes wireless communication capabilities. The
torque sensor measures torque in the rotating shaft of the damper
assembly to measure air flow. Air flow through damper blades causes
a rotational force on the damper blades, usually tending toward
opening the blades further. The rotational force is translated to a
rotating shaft directly or indirectly coupled to an actuator motor
for the VAV device. The torque sensor on the shaft senses the air
flow-induced rotational force, and generates an air flow
measurement based thereon.
[0010] A first embodiment of the invention is a damper assembly
that includes a damper frame, at least one damper blade, an
actuator, a linkage assembly including a rotating shaft coupled
between the actuator and the at least one damper blade, and a
sensor module affixed to the rotating shaft. The damper blade(s)
is/are movably attached to the damper frame to at least partially
regulate air flow proximate the damper frame. The actuator is
configured to control a position of the at least one damper blade.
The sensor module is coupled to rotating shaft and includes a
sensor device operable to determine torque force on the rotating
shaft.
[0011] In some embodiments, the sensor module preferably further
includes a wireless communication circuit that is operable to
communicate the position information to a second wireless
communication circuit disposed off of or away from the damper
blade.
[0012] A second embodiment is an arrangement for use in a damper
assembly, the damper assembly configured to measure the flow of air
in the vicinity of the damper assembly. The arrangement includes a
sensor module having a strain gauge sensor device and preferably a
wireless communication circuit. The sensor module is coupled a
first movable shaft of the damper assembly. The sensor device is
operable to determine flow-related information based on strain
gauge measurements regarding the strain on the movable shaft. The
wireless communication circuit is operable to communicate the
position information to a second wireless communication circuit
disposed off of the damper blade.
[0013] The above described features and advantages, as well as
others, will become more readily apparent to those of ordinary
skill in the art by reference to the following detailed description
and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a perspective view of an exemplary damper
assembly according to the present invention;
[0015] FIG. 2 shows a schematic block diagram of pertinent
electrical components of the damper assembly of FIG. 1;
[0016] FIG. 3 shows a schematic block diagram of the sensor module
of the damper assembly of FIGS. 1 and 2;
[0017] FIG. 4 shows a functional block diagram of a motor control
circuit of the damper assembly of FIGS. 1 and 2; and
[0018] FIG. 5 shows a representative side view of an exemplary
embodiment of a sensor module integrated onto a single
semiconductor substrate;
[0019] FIG. 6 shows a graph of torque v. flow for a plurality of
damper positions for an exemplary sensor device;
[0020] FIG. 7 shows a flow diagram of an exemplary set of
operations performed by a processing circuit to generate flow
information based on damper position and torque measurements;
[0021] FIG. 8 shows an exemplary set of operations that may be
performed to obtain a relationship between air flow through a
damper and torque measurements.
DETAILED DESCRIPTION
[0022] FIG. 1 shows a perspective view of an exemplary damper
assembly 10 according to the present invention. The electrical
components of the damper assembly 10 are illustrated in FIG. 2.
Reference is made simultaneously to FIGS. 1 and 2 in the ensuing
description. The damper assembly 10 may be employed as a VAV unit.
However, the damper assembly 10 may be used in other applications
in which flow may be controlled.
[0023] The damper assembly includes a damper frame 12, a plurality
of damper blades 14a, 14b, 14c, and 14d, an actuator module 16, a
linkage assembly 18, and a sensor module 20. The damper frame 12 is
a housing for a ventilation damper, which may suitably take the
form of any housing for an HVAC ventilation damper or variable air
volume ("VAV") unit. The plurality of damper blades 14a, 14b, 14c
and 14d are movably attached to the damper frame 12 to at least
partially regulate air flow proximate the damper frame 12. To this
end, each of the damper blades 14a, 14b, 14c and 14d may rotate
about its own longitudinal axis between a closed or nearly closed
position and various degrees of open positions. It is noted that
while four damper blades 14a, 14b, 14c and 14d are shown in the
example of FIG. 1, other embodiments may employ as few as one
damper blade and as many damper blades as is practicable. The
blades 14a, 14b, 14c and 14d are shown in parallel format, wherein
the blades open in the same direction. In alternative embodiments,
the blades 14a, 14b, 14c and 14d (or a different number of blades)
may be in an opposing configuration, wherein adjacent blades open
in opposing directions. The blades 14a, 14b, 14c and 14d may have
any shape normally associated with ventilation dampers. In this
embodiment, the blades 14a, 14b, 14c and 14d have a generally
retangular, planar shape.
[0024] The actuator module 16 is an assembly that operates to cause
movement of the damper blades 14a, 14b, 14c and 14d. More
specifically, the actuator module 16 has a mechanical output
operably connected to the linkage assembly 18 to cause controlled
movement thereof. The actuator 16 is preferably affixed to a
portion of the damper frame 12.
[0025] The linkage assembly 18 is configured to, when moved by the
actuator module 16, rotate the damper blades 14a, 14b, 14c and 14d.
Various types of linkage assemblies that translate actuator
movement to rotational movement of damper blades are known and may
suitably be used. In the exemplary embodiment described herein, the
linkage assembly 18 includes a drive rod 22 and a plurality of
linking members 24a, 24b, 24c and 24d. As shown in FIG. 2, the
drive rod 22 is coupled via a rack and pinion gear to a rotating
output shaft 36 of the actuator 16. Each of the linking members
24a, 24b, 24c and 24d are rotatably attached to the damper frame 12
and further fixedly coupled to a corresponding one of the damper
blades 14a, 14b, 14c and 14d. Because the damper blades 14a, 14b,
14c and 14d are fixedly coupled to corresponding linking members
24a, 24b, 24c and 24d, rotational movement of the linking members
24a, 24b, 24c and 24d results in rotational movement of the damper
blades 14a, 14b, 14c and 14d.
[0026] Referring again to the actuator module 16, the actuator
module 16 in the exemplary embodiment described herein includes a
housing 26 (FIG. 1) in which are contained a motor 28, a motor
control circuit 30, a gear assembly 32, a sensor communication
circuit 34, and an output shaft 36. (See FIG. 2) The housing 26 may
suitably comprise an enclosure, or a container that is partially
enclosed, which may take a variety of shapes.
[0027] Referring to FIG. 2, the motor control circuit 30 is a
circuit that is operable to control the operation of the motor 28.
The gear assembly 32 is coupled to the output of the motor 28 and
further is coupled to the output shaft 36. The gear assembly 32
converts the output rotations of the motor 38 to the output
rotations of the output shaft 36. Typically, the gear assembly 32
generates an output rotational speed that is lower than that of the
motor 38 in order to provide slow, controlled movement of the
output shaft 36. The output shaft 36 is operably connected to the
linkage assembly 18, and more specifically, the drive rod 22. As
the output shaft 36 rotates, the drive rod 22 translates in one of
directions 80, 82, depending on the direction of rotation.
[0028] The actuator motor 38, gear assembly 32 and output shaft 36
may take the form of any suitable actuator motor and mechanical
output design. Other embodiments may employ other prime movers,
such as linear displacement devices, pneumatically-powered devices,
thermally-powered devices, or the like, instead of a rotating
motor. Still other embodiments may use return springs that bias the
output shaft 36 such that the ventilation dampers are fully open or
closed in the absence of electrical power to the motor 28.
Moreover, the linkage assembly 18 may take any number of other
forms. However, the linkage assembly 18 and/or the mechanical parts
of the actuator 16 (which may be considered part of the linkage
assembly 18), preferably includes at least one rotating shaft.
[0029] Regardless of the embodiment, however, the actuator module
16 is operable to cause rotation of at least one shaft to cause
movement of the blades 14a, 14b, 14c, and 14d to approximately a
predetermined position based on an input voltage received at the
motor control circuit 30. Similarly, as a result of air flow
through the spaces around the blades 14a, 14b, 14c and 14d, air
pressure tends to cause the blades 14a, 14b, 14c and 14d to attempt
to rotate. As the rotational force is translate toward the actuator
16, the actuator 16 resists the rotation. This force attempting
rotation of the blades and stopped by the actuator 16 causes a
torque pressure in any rotating shaft in the linkage assembly 18,
including the shaft 36. The sensor assembly 20 is operable to
detect that torque, and preferably identify the flow associated
with the detected torque value. Air flow in a VAV damper assembly
has a direct relationship to the torque seen by the damper
shaft.
[0030] The sensor communication circuit 34 is operable to
communicate wireless communication signals at least over the short
range. For example, the sensor communication circuit 34 is operable
to communicate using the Bluetooth communication standard. As used
herein, wireless communication signals are considered to include
the broader definition of electrical signals radiated through the
air (i.e. without the benefit of an artificial communication medium
such as a transmission line), regardless of frequency or modulation
type.
[0031] The sensor communication circuit 34 is operably connected to
provide air flow information to the motor control circuit 30, or to
another control device in the building control system to which the
VAV assembly 10 belongs. In particular, as will be discussed
further below, the sensor communication circuit 34 is operable to
provide air flow information regarding the VAV assembly 10 to the
control device that regulates air flow. In one example, the motor
control circuit 30 uses the air flow measurements as a feedback
measurement and then controls the motor 28 to change the damper
blade position to increase or decrease the flow as needed to
achieve a desired flow.
[0032] As discussed above, the sensor module 20 is a device that
detects and communicates air flow information regarding the VAV
assembly 10. To this end, the sensor module 20 is in a fixed
relationship with the rotatable shaft 36 to sense twisting or
torque pressure on the shaft 36. As discussed above, the sensor
module 20 may be affixed to other rotating shafts in this or other
VAV linkage assembly designs.
[0033] FIG. 3 shows a schematic block diagram of an exemplary
embodiment of the sensor module 20. In order to detect or obtain
torque information regarding the shaft 36, the sensor module 20
includes a sensor device 40 that operates as a strain gauge
operable to determine torque or strain along the shaft 36. (See.
FIG. 2) The sensor module 20 further includes a wireless
communication circuit 42 operable to communicate the torque
information to a wireless communication circuit disposed off of the
damper blade 14b. In the embodiment described herein, the wireless
communication circuit 42 is operable to communicate position
information at least to the sensor communication circuit 34 of the
actuator module 16.
[0034] In the embodiment described herein, the sensor device 40 is
preferably a microelectromechanical system sensor or MEMS sensor.
MEMS sensors have the advantage of requiring relatively little
space and electrical power, and have relatively little mass. A MEMS
strain gauge sensor can readily fit onto a small enough footprint
to allow the sensor module 20 to fit onto the damper blade 14b.
MEMS sensors capable of measuring torque of a shaft, and various
methods of attaching sensors to the shaft, are known in the
art.
[0035] Referring again generally to FIGS. 1 and 2, it is preferable
if the communication circuit 42 and the processing circuit 44 are
incorporated onto the same substrate as the sensor device 40. To
this end, on-chip Bluetooth communication circuits are known. In
addition, methods of attaching MEMS devices to semiconductor
substrates is known, such as is taught in connection with FIG. 8 of
U.S. patent application Ser. No. 10/951,450 filed Sep. 27, 2004 and
which is incorporated herein by reference. FIG. 4 shows a side view
of an exemplary sensor module 20 wherein the various components are
incorporated into one chip.
[0036] The processing circuit 44 is operable to generate air flow
information from the torque information. For example, the
processing circuit 44 may use a look-up table to associate torque
measurements with actual air flow. The relationship between air
flow and shaft torque may be determined in a calibration operation.
An exemplary calibration information is discussed below in
connection with FIG. 8.
[0037] It will be appreciated that some or all of the processing of
the torque information may be carried out elsewhere, such as in the
motor control circuit 30, in order to conserve power. However, it
is useful to at least include filtering in the processing circuit
44 in order to reduce the amount of data transmitted and thereby
conserve power.
[0038] Referring to FIG. 5, a preferred embodiment of the sensor
module 20 is a semiconductor substrate 46 having the processing
circuit 44 and the communication circuit 42 formed thereon, and a
MEMS sensor device 40 attached thereto, such as by flip-chip
bonding. In addition, it would be advantageous to attach a power
source such as a battery to the substrate 46. The battery may
suitably be a lithium ion coin cell type structure 49 affixed to
the side of the semiconductor substrate 46 opposite the processing
circuit 44 and communication circuit 42. It will be appreciated
that if a suitable communication circuit cannot be formed in the
semiconductor substrate 46, it too may be separately formed and
then attached via flip-chip or similar type of bonding.
[0039] Referring again to FIGS. 1 and 2, the damper assembly 10 is
intended to provide a desired air flow by adjusting the positioning
of the damper blades 14a, 14b, 14c and 14d. In the exemplary
embodiment described herein, the desired air flow is provided as an
input voltage or signal w by the motor control circuit 30 of the
actuator module 16. The input signal w is a set point provided by
an HVAC controller or the like, not shown, which determines the
amount of air flow, which in turn determines the degree to which
the damper blades 14a, 14b, 14c and 14d should be opened. The
damper blades 14a, 14b, 14c and 14d are opened or closed in order
to increase or decrease, respectively, the flow of heated or
chilled air into an area of a building or ventilation shaft.
[0040] Ideally, the actuator module 16 and the linkage assembly 18
cooperate to position the damper blades 14a, 14b, 14c and 14d in
the position that corresponds to the input signal w. However, due
to errors and/or tolerances in the elements of the linkage assembly
18 and motor amplifiers and the like, accurate positioning is not
practicable without at least some feedback regarding the position
of the damper blades 14a, 14b, 14c and 14d. In accordance with the
present invention, the position feedback is provided from by any
known method, such as that described in U.S. patent application
Ser. No. 11/192,587, filed Jul. 29, 2005, which is incorporated
herein by reference. With accurate feedback, damage from trying to
open or close the damper blades 14a-d out of allowed ranges may be
avoided.
[0041] In general, however, the motor control circuit 30 uses the
actual air flow measurements provided by the sensor 20, and the
desired air flow w, to adjust the position of the damper blades
14a, 14b, 14c and 14d. The feedback positioning control operation
discussed above is carried out by the motor control circuit 30 in
the embodiment described herein. A functional block diagram of the
motor control circuit 30 is shown in FIG. 4. Referring to FIG. 3,
the motor control circuit 30 includes a set point input 48, a motor
control signal output 50, an air flow information input 52, a
conversion/scaling unit 54, a filter 58, a summation device 60, and
an amplifying and conditioning circuit 62.
[0042] As illustrated by FIG. 2, the set point input 48 is coupled
to receive the input signal (representative of desired air flow
rate) w, and the motor signal output 50 is operably coupled to the
motor 28. In addition, the air flow information input 52 is
connected to the communication circuit 34. Referring again to FIG.
4, the set point input 48 is operably coupled to a positive
summation input of the summation device 60. A negative summation
input of the summation device 60 is operably connected to receive a
current flow signal x' from the flow information input 52 via the
conversion/scaling unit 54.
[0043] The conversion/scaling unit 54 provides any conversion
necessary between the units of the feedback flow information x from
the input 52 and units of the desired air flow information employed
by the input signal w. The conversion/scaling unit 54 may suitably
include logic for unit conversion and conversion circuitry between
analog and digital signals. The exact construction of the
conversion/scaling unit 54 will depend on the formats of the flow
information at the two inputs 48 and 52. Those of ordinary skill in
the art may readily devise a suitably conversion circuit once the
format of the air flow information at the two inputs 48 and 52 are
known. In some embodiments, the input signal w will be converted to
units of the air flow input signal x in the motor control circuit
30 prior to being forwarded to the summation device 60. In such a
case, the conversion/scaling unit 54 would be coupled between the
input 48 and the summation device 60.
[0044] In any event, the output of the summation device 60 is an
error signal e that represents the difference between the desired
air flow w and the current air flow x'. The summation device 60 is
operably connected to provide the error signal to the filter 58,
which is in turn coupled to the amplifying and conditioning circuit
62. The filter 58 is a control filtering device that provides a
controlled loop delay and/or dampening function using proportional,
proportion integrational derivative ("PID"), or other known control
signal conditioning techniques. The filter 58 provides a desired
transition profile (speed and dampening) between the current
position of the damper blades, and the position of the damper
blades 14a, 14b, 14c and 14d necessary to achieve the desired air
flow. Fine position control may be carried out downstream of the
filter 58, using the position feedback system taught by U.S. patent
application Ser. No. 11/192,587, discussed above, or any other
position feedback device. While such a feedback control is not
shown in detail here, it may be provide as part of the filter 58.
In either event, the output y of the filter 58 is based on the
error signal e and the control function.
[0045] The output y of the filter 58 is connected to the amplifying
and conditioning circuit 62. The amplifying and conditioning
circuit 62 has the analog circuitry that converts a communicated
control signal y (from the filter 58) into a motor control signal.
The communicated control signal may suitably be a digital value, or
an analog voltage signal, depending on the design of the control
filter 58 and the format of the input signal w. In either case, the
control output signal y typically is not specifically designed to
control the motor 28 directly, but rather requires amplification,
conditioning, and often conversion into another form. Suitable
amplification and conditioning circuits are known and will vary
depending on the design of the motor 28, the gear assembly 32 and
linkage assembly 18. The output of the amplifying and conditioning
circuit 62 is operably coupled to the motor signal output 50.
[0046] Operation of the damper assembly 10 is described in
reference to FIGS. 1, 2, 3 and 4 simultaneously. Initially, a set
point signal w is provided to the actuator module 16, and in
particular, to the set point input 48 of the communication circuit
42. The set point signal w in this embodiment is representative of
a desired air flow through the assembly 10. By way of example, the
desired air flow through the assembly may be derived by another
control device, not shown. That control device may determine the
desired air flow through the assembly 10 into the adjacent space
based on: the temperature of the supply air; the desired
temperature of the space; and any requirements for fresh air
circulation in the space.
[0047] The motor control circuit 30 receives the input signal w and
generates appropriate motor control signals to place the damper
blades 14a, 14b, 14c and 14d.
[0048] To this end, referring to FIG. 4, the motor control circuit
30 receives the input signal w at the summation device 60. The
negative input of the summation device 60 receives the value x',
which is representative of the current air flow through the damper
assembly 10. The current damper flow value x' is obtained from flow
information generated by the sensor module 20. Obtaining that
damper flow value x' is described in particular reference to FIG.
3.
[0049] Referring to FIG. 3, the sensor 40 of the sensor module 20
generates a signal representative of the torque on the shaft 36.
The processing circuit 44 receives the torque signal and generates
a refined value that constitutes the air flow information x. To
generate the air flow value x, the processing circuit 44 may
suitably employ analog to digital conversion, low pass filtering,
and a look-up table or linear relationship on the torque
signal.
[0050] More specifically, it has been determined experimentally
that the measured torque value of the shaft 36 varies as a function
of air flow and damper position. The phrase "damper position"
describes the amount that the damper is opened or closed. In this
embodiment, the damper position may be a number of values from
0.degree. (fully closed) to 90.degree. (fully open). In general,
however, dampers tend not be fully closed when used for room
ventilation.
[0051] Thus, the processing circuit 44 of FIG. 3 generates flow
information in the form of a flow value x based on both torque
measurements and the position of the damper. FIG. 6 shows an
exemplary set of curves of torque versus air flow for a plurality
of damper positions.
[0052] Because the processing circuit 44 uses both the torque of
the shaft 36 and the damper position to determine, information
regarding the damper position must be provided to the processing
circuit 44. To this end, the processing circuit 44 may obtain
damper position information from the motor control circuit 30 via
the wireless link between the sensor communication circuit 34 and
the wireless circuit 42. However, in other embodiments, the sensor
module 20 merely provides the torque measurement information to the
motor control circuit 30, which in turn generates the flow value x
using the received torque information and the otherwise available
damper position information.
[0053] In this embodiment, it is assumed that the processing
circuit 44 of the sensor module 20 obtains the damper position
information and generates the flow information x as a function of
the measured torque and the damper position. In such a case, the
processing circuit 44 provides the flow information x to the
wireless communication circuit 42.
[0054] The wireless communication circuit 42 of the sensor module
20 performs modulation, conditioning and amplification to generate
a wireless air flow signal which is transmitted to the sensor
communication circuit 34 of the actuator module 16. The sensor
communication circuit 34 then provides the flow information x to
the flow information input 52 of the motor control circuit 30.
[0055] Referring to FIG. 4, the conversion/scaling unit 54
performs, if necessary, conversion of the position information x to
generate the flow information x' in appropriate units.
[0056] Thus, the summation device 60 receives the value w
representative of the new desired flow value at its positive
summation input and the value x' representative of the current flow
value x' at its negative summation input. The output of the
summation device 60, the error signal e, is a signed value
representative of the amount that the damper flow has to be
adjusted to achieve the desired air flow w.
[0057] The filter 58 receives the error signal e and generates a
process signal y based thereon. The process signal y constitutes
the output of the control algorithm. The filter 58 provides the
process signal y to the amplifying and conditioning circuit 62. As
discussed above, the filter 58 may incorporate a position feedback
system that generates position information, based on the desired
flow information. Such devices are well known. However, the flow
information may be used for direct control without position
feedback in some cases, provided there are safeguards from over
positioning the damper blades. In any event, the amplifying and
conditioning circuit 62 generates the motor control signals to
change the damper position from the present position by an amount
(and direction) indicated in the process signal y. These motor
control signals are provided to the motor control output 50.
[0058] Referring again generally to FIGS. 1 and 2, the motor 28
receives the motor control signals from the motor control output 50
and generates an amount of rotation, as well as direction of
rotation, corresponding to the motor control signals. The gear
assembly 32 converts the motor rotation to a suitable movement of
the output shaft 36, which in turn, drives the drive rod 22. The
movement of the drive rod 22 rotates the linking members 24a, 24b,
24c and 24d by an amount and direction corresponding to the output
signal y. The linking members 24a, 24b, 24c and 24d rotate the
damper blades 14a, 14b, 14c and 14d accordingly.
[0059] When the damper blades 14a-d are at rest, air flow will
impinge upon the blades and attempt to cause them to rotate.
[0060] As the blades 14a, 14b, 14c and 14d experience the
rotational force due to the impingement of the air flow, the force
is translated by the linking members 24a, 24b, 24c and 24d to the
drive rod 22, which in turn translates the air flow induced
mechanical/rotational force on the output shaft 36. Because the
output shaft 36 cannot rotate due to holding forces of the actuator
16, the output shaft 36 experiences torque or twisting force that
may be translated from end to end. The sensor 40 of the sensor
module 20 detects the torque force and generates a new signal. The
processing circuit 44 (in this embodiment) converst the new torque
information to a flow value x, and causes the wireless circuit 42
to transmit the new flow information x (or torque information in
other embodiments) to the communication circuit 34 of the actuator
module 16. The communication circuit 34 provides the new flow
information x to the air flow information input 52 of the motor
control circuit 30.
[0061] The above described process repeats iteratively, so that the
actual measured air flow matches, or at least falls within a
predetermined error window of, the desired air flow w.
[0062] It will be appreciated that the flow information x need not
be communicated to the actuator module 16 directly. Another
wireless communication device may receive the transmitted position
information from the sensor module 20, and then forward the sensor
information to the actuator module 16 or any other control device
by other means. In fact, a wireless circuit may not be necessary.
In addition, other elements of the actuator module 16 may suitably
be located in separate housings as opposed to within a single
housing as described above. However, the embodiment of FIG. 2
provides the added advantage of providing a compact and easy to
install configuration.
[0063] FIGS. 6, 7 and 8 illustrate in further detail how, in the
exemplary embodiment described herein, the processing circuit 44
may generate flow information based on damper position information
.phi. and measured torque value .tau.. FIG. 7 shows a series of
steps that may be carried out to this end. In the embodiment
described herein, the steps of FIG. 7 are carried out by suitable
programming of the processing circuit 44. However, in other
embodiments, processing circuits of other devices, such as the
motor control circuit 30 of FIG. 2, for example, may carry out the
steps of FIG. 7.
[0064] In step 702, the processing circuit obtains a torque
measurement from the sensor 40. To this end, the processing circuit
may include A/ID conversion circuitry and/or other conditioning
circuitry known in the art that can convert a MEMS strain sensor
output to an input for a processing device.
[0065] In step 704, the processing circuit obtains the damper
position. In the embodiment described herein, the processing
circuit 44 obtains the damper position from the motor control
circuit 30, which will typically retain such information to allow
for closed loop control of damper movement and/or for other
reasons, as is known in the art. The motor control circuit 30 may
provide the information to the processing circuit 44 via the
wireless communication circuits 34 and 42. Such damper position
information may be included in a request for flow information
issued by the motor control circuit 30.
[0066] In step 706, the processing circuit determines a flow value
x based on the damper position information .phi. and the torque
measurement .tau. obtained from the sensor 40. In other words, the
processing circuit solves the equation: x=F{.phi., .tau.}
[0067] where F{.phi., .tau.} describes a function or series of
functions that generate a flow measurement value x as a function of
damper position and damper shaft torque. In one embodiment, the
function F{.phi., .tau.} includes a separate x=F.sup..phi.{.tau.}
for each damper position value .phi.. By way of example, FIG. 6
shows a series of curves 602, 604, 606, 608, 610, 612, 614 and 616,
each representing a torque versus flow curve, x=F.sup..phi.{.tau.}
for one particular damper position .phi.. By way of example, the
curve 602 shows the torque versus flow curve for a damper position
of 20.degree. open (.phi.=20). When a damper is said to be at the
20.degree. position, it means that each damper blade is
approximately 20.degree. from a position at which the damper blades
as a group would completely close. Thus, when a damper is said to
be at 90.degree. position, it means that the damper is 90.degree.
from being fully closed, which means that the damper is fully
open.
[0068] The series of curves 602-616 of FIG. 6 may be represented in
a memory (i.e. the memory 45 of FIG. 2) as a series of piecewise
linear functions x=F.sup..phi.{.tau.} indexed by damper position
.phi.. In particular, for each damper position, the curve may
suitably be a piecewise linear function derived from a series of
calibration points of torque versus flow. FIG. 8, discussed further
below, describes a calibration function in which a particular
sensor module 20 may be calibrated to generate the relationships
between flow, damper position and torque.
[0069] Referring again to step 706, the processing circuit thus
obtains the flow value x based on torque and damper position and
proceeds to step 708. In step 708, the processing circuit 708
causes the information to be communicated wirelessly to the motor
control circuit 30, as described more generally above. In other
embodiments, the processing circuit 708 can cause the information
to be communicated wirelessly to another device, such as a data
collector, or a network interface device.
[0070] FIG. 8 describes a calibration operation in which
information regarding the torque/flow correspondence is obtained.
The result of the operations of FIG. 8 may suitably be a table of
torque values corresponding to flow values for each of a set of
damper positions. This table may be used to generate piecewise
linear functions of sensor torque versus flow for each damper
position, such as those illustrated in FIG. 6. The calibration
operation is performed by placing the damper assembly 10 with the
sensor module 20 in a test chamber in which air flow may be
controllable passed through the damper assembly 10. In addition,
one or more high accuracy flow sensors should also be attached at a
position in the opening of the damper to measure the actual test
flow. Such calibration set-ups for providing controlled flow
through a damper and measuring the flow are known in the art.
[0071] The calibration operation may be automated by a calibration
control processing circuit or device, not shown. It is also
possible to include the calibration program of FIG. 8 in the
processing circuit 44 of the sensor module 20, or the motor control
circuit 30 of the actuator module 16.
[0072] In any event, in step 802, the processing circuit causes the
damper position to be moved to the 10.degree. symbol and sets an
internal variable DP=10.
[0073] Thereafter, in steps 804, the processing circuit causes the
calibration air flow to be set to a first value, which may suitably
be 1/N.sup.th of a maximum test air flow value, where N is the
number of sample points to be taken for each damper position. For
example, if the maximum test air flow value is 2500 cubic feet per
minute, and there are to be five sample points taken, then the
first value would be 2500/5 or 500 cubic feet per minute. The
processing circuit also sets an internal value of FL=1/N (Max
Flow). The processing circuit then proceeds to step 806.
[0074] In step 806, the processing circuit obtains a torque
measurement from the sensor 40 of the sensor module 20. This value
represents the torque that is measured when the damper position is
equal to DP (in degrees) and the flow is equal to FL.
[0075] In step 808, the processing circuit stored the torque
measurement in a table or as an array value TCAL (DP, FL). This
point may be graphed to a point on a graph similar to that of FIG.
6.
[0076] In step 810, the processing circuit determines whether FL
=Max Flow. If so, then all N data points of torque versus flow have
been obtained for the current damper position, and the processing
circuit proceeds to step 814. If not, however, then additional data
points should be taken for the current damper position, and the
processing circuit proceeds to step 812.
[0077] In step 812, the processing circuit causes the calibration
air flow value to be increased by 1/N.sup.th of the maximum flow
value, and changes the internal variable FL to FL=FL+(1/N) Max
Flow. The processing circuit then returns to step 806 and proceeds
accordingly.
[0078] In step 814, the processing circuit determines whether the
current damper position is 90.degree., or in other words, if DP=90.
If so, then the calibration operation is complete and the
processing circuit proceeds to step 818, discussed further
below.
[0079] If not, however, then the processing circuit proceeds to
step 816 to change the damper position for the purpose of obtaining
a new set of torque versus flow calibration table measurements.
Accordingly, in step 816, the processing circuit causes the damper
position to be increased by 10.degree. and increments the internal
value DP to DP=DP+10. The processing circuit then returns to step
804 in order to reset the air flow to FL=(1/N)(Flow Max) and to
proceed accordingly.
[0080] In step 818, the gathering of calibration points is
complete. These calibration points associate a torque measurement
with an actual measured flow for each of a plurality of damper
positions. It is noted that if verification is desired, then the
entire process of FIG. 8 may be repeated for the same sensor.
[0081] Because sufficient data points have been gathered, a
function x=F.sup..phi.(.tau.) may be generated for each damper
position .phi.. For example, a piecewise linear function
F.sup..phi.(.tau.) for each damper position .phi. may be created by
interpolating between adjacent data points on the table created by
the operations of FIG. 8. Alternatively, each function
F.sup..phi.(.tau.) may be generated using a best fit curve of the
data points on the table created by the operations of FIG. 8. Still
other methods of using the calibration points to create a function
or series of functions F (.phi., .tau.) for use in generating a
flow value x based on damper position .phi. and a measured torque
value .tau. may be used.
[0082] It will further be appreciated that the above described
embodiments are merely exemplary, and that those of ordinary skill
in the art may devise their own modifications and implementations
that incorporate the principles of the present invention and fall
within the spirit and scope thereof.
* * * * *