U.S. patent application number 16/165069 was filed with the patent office on 2022-02-03 for method and apparatus for providing real time air measurement applications in wet concrete using dual frequency techniques.
The applicant listed for this patent is John Biesak, Michael A. Davis, Douglas H. Loose. Invention is credited to John Biesak, Michael A. Davis, Douglas H. Loose.
Application Number | 20220034844 16/165069 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-03 |
United States Patent
Application |
20220034844 |
Kind Code |
A9 |
Biesak; John ; et
al. |
February 3, 2022 |
METHOD AND APPARATUS FOR PROVIDING REAL TIME AIR MEASUREMENT
APPLICATIONS IN WET CONCRETE USING DUAL FREQUENCY TECHNIQUES
Abstract
Apparatus is provided having an acoustic-based air probe with an
acoustic source configured to provide an acoustic signal into a
mixture of concrete; and an acoustic receiver configured to be
substantially co-planar with the acoustic source, to respond to the
acoustic signal, and to provide signaling containing information
about the acoustic signal injected into the mixture of
concrete.
Inventors: |
Biesak; John; (Durham,
CT) ; Loose; Douglas H.; (Southington, CT) ;
Davis; Michael A.; (Glastonbury, CT) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Biesak; John
Loose; Douglas H.
Davis; Michael A. |
Durham
Southington
Glastonbury |
CT
CT
CT |
US
US
US |
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|
Prior
Publication: |
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Document Identifier |
Publication Date |
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US 20200124570 A1 |
April 23, 2020 |
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Appl. No.: |
16/165069 |
Filed: |
October 19, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14350711 |
Apr 9, 2014 |
10156547 |
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PCT/US12/60822 |
Oct 18, 2012 |
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16165069 |
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61548549 |
Oct 18, 2011 |
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61548563 |
Oct 18, 2011 |
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International
Class: |
G01N 29/024 20060101
G01N029/024; G01N 29/24 20060101 G01N029/24; G01N 29/42 20060101
G01N029/42; G01N 29/44 20060101 G01N029/44; G01N 29/50 20060101
G01N029/50; G01F 1/74 20060101 G01F001/74; G01N 33/38 20060101
G01N033/38; G01F 1/708 20060101 G01F001/708 |
Claims
1-42. (canceled)
43. Apparatus comprising: a signal processor configured to receive
signaling containing information about an acoustic signal injected
into a mixture of concrete; and determine a measurement of air
percentage in the mixture of concrete based at least partly on a
dual frequency technique that depends on a relationship between the
acoustic signal injected and the signaling received.
44. Apparatus according to claim 43, wherein the acoustic signal
injected is a reference signal; the signaling received is detected
signaling; and the signal processor configured to determine the
measurement of air percentage in the mixture of concrete based at
least partly on mixing the reference signal with the detected
signaling using a phase sensitive lock-in approach.
45. Apparatus according to claim 44, wherein the signal processor
is configured to determine a resulting signal based at least partly
on the mixing of the reference signal with the detected signaling;
filter the resulting signal, including with a low pass filter, to
get a DC component; and determine a value that is proportional to
amplitude and phase components of the detected signaling at the
frequency of the reference signal.
46. Apparatus according to claim 45, wherein the signal processor
is also configured to determine a corresponding value that is
proportional to corresponding amplitude and phase components of the
detected signaling with the frequency of reference signal shifted
by 90 deg.
47. Apparatus according to claim 46, wherein the signal processor
is configured to determine a signal phase difference based at
partly on the following: using .THETA.ref as a reference phase,
.THETA.det as a detected phase, Adet as a detected signal amplitude
at a frequency of interest; and determining a signal amplitude and
the signal phase difference using the following set of equations:
.THETA.=.THETA.det-.THETA.ref, X.about.Adet cos(.THETA.),
Y.about.Adet cos(.THETA.+90 deg) =Adet sin(.eta.), Signal
amplitude=Adet=(X.sup.2*Y.sup.2).sup.1/2, and Signal phase
difference=.THETA.=tan.sup.-1(Y/X).
48. (canceled)
49. Apparatus according to claim 47, wherein the signaling contains
information about two reference signals that are injected into the
mixture of concrete at different frequencies in order correct or
compensate for ambiguity that may otherwise exist once the detected
signaling has gone though a propagation time equal to 2*pi of a
single injected acoustic signal, including any multiple thereof;
and the signal processor is configured to determine a relative
phase between the two reference signals in order correct or
compensate for the ambiguity.
50. Apparatus according to claim 47, wherein the signal processor
is configured to determine a quality metric based at least partly
on the signal amplitude and signal phase difference determined.
51. Apparatus according to claim 50, wherein the signal processor
is configured to take the signal amplitude of a signal of interest
at Asig; take a sample of four other comparison signals spaced
adjacent thereto of A0, A1, A2 and A3; average four other
comparison signals to obtain an adjacent noise
Anoise=(A0+A1+A2+A3)/4; and take a difference over a sum
normalization to determine a quality signal, Q, that varies between
-1 to 1 based at least partly on using the following equation:
Q=(Asig-Anoise)/(Asig+Anoise), with a ratio of "1" representing a
good quality, a ratio of "0" indicating same signal strength at
frequency of interest as other frequencies, and a ratio of "-1" as
a very weak signal of interest.
52. Apparatus according to claim 43, wherein the signal processor
is configured to determine the measurement of air percentage in the
mixture of concrete based at least partly on correlating the
acoustic signal injected and the signaling received.
53. Apparatus according to claim 52, wherein the signal processor
is configured to determine a phase delay due to a transit of the
acoustic signal injected in the mixture of concrete based on the
correlating of the acoustic signal injected and the signaling
received.
54. Apparatus according to claim 53, wherein the signal processor
is configured to determine the speed of sound based on the phase
delay.
55. Apparatus according to claim 53, wherein the signaling
containing information about the acoustic signal injected into the
mixture of concrete is based at least partly on using a simple
sweep of an excitation frequency to an acoustic actuator, which
increases the sensitivity of a correlation process.
56. Apparatus according to claim 53, wherein the simple sweep is
the equation: ti Y(i)=A sin(a i.sup.2/2+b i).
57. Apparatus according to claim 53, wherein the signaling
containing information about the acoustic signal injected into the
mixture of concrete is based at least partly on one or more
techniques of encoded pulsing that are used to alternatively
enhance the signal-to-noise of a detected acoustic signal.
58. Apparatus according to claim 53, wherein the encoded pulsing is
based at least partly on a pseudo-random sequence (PRBS), where the
PRBS is defined as a sequence of N bits where an autocorrelation of
the sequence gives a number proportional to the number of "on" bits
times the sequence length when there is no misalignment and a low
number proportional to only the number of on bits when
misaligned.
59. Apparatus according to claim 58, wherein the PRBS in the case
of free-space acoustic measurements is based at least partly on
PRBS excitation that can be created by turning on and off an
excitation acoustic wave according to the PRBS sequence, or by
frequency modulating the acoustic signal by the PRBS sequence.
60. Apparatus according to claim 58, wherein the signaling
containing information about the acoustic signal injected into the
mixture of concrete is based at least partly on frequency encoding,
including m-sequence codes or frequency shift keying
approaches.
61. Apparatus according to claim 43, wherein the signal processor
is configured to provide corresponding signaling containing
information about the measurement of air percentage in the mixture
of concrete, including to control the amount of air in the mixture
of concrete by causing an addition or subtraction of some type or
kind of material or substance to modify the air percentage in the
mixture of concrete.
62. A method comprising: receiving in a signal processor signaling
containing information about an acoustic signal injected into a
mixture of concrete; and determining in the signal processor a
measurement of air percentage in the mixture of concrete based at
least partly on a dual frequency technique that depends on a
relationship between the acoustic signal injected and the signaling
received.
63. A method according to claim 62, wherein the acoustic signal
injected is a reference signal; the signaling received is detected
signaling; and the method comprises determining the measurement of
air percentage in the mixture of concrete based at least partly on
mixing the reference signal with the detected signaling using a
phase sensitive lock-in approach.
64. A method according to claim 62, wherein the method comprises
determining the measurement of air percentage in the mixture of
concrete based at least partly on correlating the acoustic signal
injected and the signaling received.
65. Apparatus comprising: means for receiving signaling containing
information about an acoustic signal injected into a mixture of
concrete; and means for determining a measurement of air percentage
in the mixture of concrete based at least partly on a dual
frequency technique that depends on a relationship between the
acoustic signal injected and the signaling received.
66. Apparatus according to claim 65, wherein the acoustic signal
injected is a reference signal; the signaling received is detected
signaling; and the apparatus comprises means for determining the
measurement of air percentage in the mixture of concrete based at
least partly on mixing the reference signal with the detected
signaling using a phase sensitive lock-in approach.
67. Apparatus according to claim 65, wherein the apparatus
comprises means for determining the measurement of air percentage
in the mixture of concrete based at least partly on correlating the
acoustic signal injected and the signaling received.
68. (canceled)
69. Apparatus according to claim 44, wherein the signal processor
is configured to provide corresponding signaling containing
information about the measurement of air percentage in the mixture
of concrete, including to control the amount of air in the mixture
of concrete by causing an addition or subtraction of some type or
kind of material or substance to modify the air percentage in the
mixture of concrete.
70. Apparatus according to claim 52, wherein the signal processor
is configured to provide corresponding signaling containing
information about the measurement of air percentage in the mixture
of concrete, including to control the amount of air in the mixture
of concrete by causing an addition or subtraction of some type or
kind of material or substance to modify the air percentage in the
mixture of concrete.
71. Apparatus according to claim 43, wherein the apparatus
comprises an acoustic source configured to injected the acoustic
signal into the mixture of concrete; and at least one acoustic
receiver configured to respond to the acoustic signal injected into
the mixture of concrete and provide the signaling received.
72. Apparatus according to claim 71, wherein the apparatus
comprises an acoustic-based air probe having acoustic source and
the at least one acoustic receiver.
73. Apparatus according to claim 72, wherein the at least one
acoustic receiver is configured substantially coplanar with the
acoustic source
74. Apparatus according to claim 73, wherein the acoustic-based air
probe comprises a planar probing surface having a first aperture
formed therein configured to receive part of the acoustic source;
and the planar probing surface has at least one second aperture
formed therein configured to receive part of the acoustic
receiver.
75. Apparatus according to claim 71, wherein the acoustic source
comprises a floating mass.
76. Apparatus according to claim 71, wherein the at least one
acoustic receiver comprises a pressure transducer.
77. Apparatus according to claim 71, wherein the at least one
acoustic receiver comprises two acoustic receivers, each acoustic
receiver configured to respond to the acoustic signal injected into
the mixture of concrete and provide respective signaling containing
respective information about the acoustic signal injected into the
mixture of concrete.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit to provisional patent
application Ser. No. 61/548,549, filed 18 Oct. 2011 (WFVA/CiDRA
file nos. 712-2.365/75); and Ser. No. 61/548,563, filed 18 Oct.
2011 (WFVA/CiDRA file nos. 712-2.366/67), which are both
incorporated by reference in their entirety.
[0002] This application also relates to U.S. patent application
Ser. No. 13/583,062, filed 12 Sep. 2012 (WFVA/CiDRA file nos.
712-2.338-1/CCS-0033, 35,40, and 45-49), which is a national stage
application corresponding to PCT/US1127731, which are both
incorporated in their entirety by reference, and assigned to the
assignee of the present application.
BACKGROUND OF THE INVENTION
1. Field of Invention
[0003] The present invention relates to a technique for real time
air measurement in wet concrete; more particularly related to a
technique for real time air measurement in wet concrete in order to
control the amount of air in a mixture of concrete.
2. Description of Related Art
[0004] In the prior art, the use of a method for the determination
of the flow rate of the medium through a measurement of the
velocity of convecting vortical pressure instabilities, and the
composition of a two-phase flow through the determination of the
speed of sound of the medium, are known. As the composition of the
flow varies between the two extremes of 100% of one fluid to 100%
of the other, the speed of sound varies in a deterministic way
between the values of sound speed in the two respective materials.
In the known techniques, the determination of the speed of sound
was made using `passive` listening of the sound propagating in the
flow stream.
[0005] In the prior art, a number of techniques have been developed
that rely on measuring the speed of sound through a material
flowing through a pipe. These techniques include using a known
SONAR-based GVF meter, density meter and potential mass fraction
meter. In these techniques, a passive array-based sensor system is
used to detect the presence and speed of acoustics traveling
through the materials contained within a pipe. These materials can
range from single phase homogeneous fluids to two or three phase
mixtures of gases, liquids and solids.
[0006] Since the measurements system is passive it relies on
acoustics produced externally for the measurement. These acoustics
can often times come from other equipment in or attached to the
pipe such as pumps or valves.
[0007] Moreover, in these known techniques many times chemical
additives may be added, including to a known flotation process in
mineral processing to aid in the separation of the ore. The
chemicals, known as frothers, control the efficiency of the
flotation process by enhancing the properties of the air bubbles.
An important parameter in flotation optimization is the gas volume
fraction within a flotation cell. U.S. Pat. No. 7,426,852 B1, which
is hereby incorporated by reference in its entirety, discloses
approaches to make this measurement, and discloses a technique
whereby the speed of sound in the aerated fluid is locally measured
using a waveguide (pipe) in conjunction with a SONAR-based array.
From the speed of sound measurement, the gas volume fraction can be
calculated.
[0008] By way of example, see other techniques related to the use
of such SONAR-based echnology disclosed, e.g., in whole or in part
in U.S. Pat. Nos. 7,165,464; 7,134,320; 7,363,800; 7,367,240; and
7,343,820, all of which are incorporated by reference in their
entirety.
[0009] Moreover, air is a very important component of many
materials, such as viscous liquids, slurries or solids, and
mixtures of concrete. In particular, air is a critical ingredient
when making concrete because it greatly improves the cured product
damage resistance to freeze/thaw cycles. Chemical admixtures are
typically added during mixing to create, entrain and stabilize
billions of small air bubbles within the concrete. However, the
entrained air in concrete has the disadvantage of reducing strength
so there is always a trade-off to determine the right amount of air
for a particular application. In order to optimize certain
properties of concrete, it is important to control the entrained
air present in the wet (pre-cured) concrete. Current methods for
measuring the entrained air can sometimes be slow and cumbersome
and additionally can be prone to errors. Moreover, the durability
of concrete may be enhanced by entraining air in the fresh mix.
This is typically accomplished through the addition of chemical
admixes. The amount of admix is usually determined through
empirical data by which a "recipe" is determined. Too little
entrained air reduces the durability of the concrete and too much
entrained air decreases the strength. Typically the nominal range
of entrained air is about 5-8% by volume, and can be between 4% and
6% entrained air by volume in many applications. After being mixed
in the mixer box, the concrete is then released to the truck. The
level of entrained air is then measured upon delivery of the mix to
the site. The draw back of the current method is that the mix is
committed to the truck without verification of that the air level
in the mix is within specification.
[0010] The aforementioned U.S. patent application Ser. No.
13/583,062 techniques for real time air measurement in wet concrete
in concrete a rotary drum mixer, including implementing sensing
technology in a hatch cover, as well as a stationary concrete mixer
using an integrated sound source and two receivers, using
SONAR-based technology developed and patented by the assignee of
the instant patent application as well as that application.
SUMMARY OF THE INVENTION
[0011] The present application provides new means, techniques or
ways of real time measurement of entrained air in wet concrete,
consistent with and further building on that set forth in the
aforementioned U.S. patent application Ser. No. 13/583,062, filed
12 Sep. 2012 (WFVA/CiDRA file nos. 712-2.338-1/CCS-0033, 35,40, and
45-49).
[0012] By way of example, the present invention provides new
measurement devices that may include, or take the form of,
acoustic-based air probes, e.g., that may be permanently installed
in a precut hole on the side or bottom of a stationary mixer, or
alternatively that may be handheld for taking the real time
measurement. The same or a substantially similar installation
technique of installing in the precut hole of the stationary mixer
may be used or applied for applications related to a rotating drum
style mixer, or other type or kind of mixer, consistent with that
disclosed herein. By way of example, these measurement devices
according to the present invention may be used for real time air
measurement on the stationary mixer (such as a twin shaft, counter
current, planetary, pan etc.) during the mixing process. With real
time air measurement, an operator will be able to improve the
quality control of all concrete produced. Entrained air level in
concrete may be controlled to a tighter tolerance. With tight air
control, the mix design can be optimized by reducing cement and
replacing it with sand, fly ash or another filler, while still
achieving the desired strength requirement.
[0013] This will reduce cost, improve workability and reduce
"bleeding "incidents. There are many types of concrete that are
made in stationary mixers, including precast, prestress,
architectural, paving, block, ready mix--central mixers primarily
in but limited to Europe, etc. All these types of concrete will
likely benefit from real time air control, according to the present
invention.
[0014] With real time air information the operator will now have
the ability to adjust the air levels (manually or automatically
(via a process control)) through chemical addition prior to dumping
the concrete from the mixer. An automatic closed loop system may be
used that includes these types of measurement devices with real
time air information output to the control room or to the dosing
pump, chemical dosing pumps, air related chemicals and the
engineering expertise to tie it all together.
The Acoustic-Based Air Probe
[0015] According to some embodiments, the present invention may
include, or take the form of, apparatus featuring an acoustic-based
air probe having an acoustic source configured to provide an
acoustic signal into a mixture of concrete; and an acoustic
receiver configured to be substantially co-planar with the acoustic
source, to respond to the acoustic signal, and to provide signaling
containing information about the acoustic signal injected into the
mixture of concrete.
[0016] The present invention may also include, or take the form of,
some combination of the following features:
[0017] The acoustic-based air probe may include a planar probing
surface having a first aperture formed therein configured to
receive part of the acoustic source, e.g., a rigid hardened steel
piston. The planar probing surface may include at least one second
aperture formed therein configured to receive part of the acoustic
receiver, e.g., a protective polyurethane rubber fill. The planar
probing surface may be configured as a hardened steel face
plate.
[0018] The acoustic-based air probe may include the protective
polyurethane rubber member arranged as the part in the at least one
second aperture.
[0019] The acoustic receiver may include a dynamic pressure
transducer. The acoustic receiver may be configured to receive
acoustic signals having a frequency in a range of about 100-500 Hz,
including 330 Hz.
[0020] The acoustic source may include, or be configured as, a
floating mass.
[0021] The acoustic source may include a piston module assembly
having the rigid hardened steel piston configured with a channel to
receive a piston shaft. The apparatus may include a vibration
isolated actuator block assembly having a stationary voice coil
actuator field assembly in combination with a voice coil actuator
field assembly having an accelerometer transducer, the vibration
isolated actuator block assembly being configured to drive the
piston shaft.
[0022] The acoustic-based air probe may include a fluid/media
temperature sensor.
[0023] The acoustic-based air probe may include a voice coil
temperature sensor.
[0024] The acoustic-based air probe may include two acoustic
receivers, including two dynamic pressure transducers.
[0025] The apparatus may include dosing apparatus configured to
respond to the signaling, and provide a control signal to control
the dosing of a chemical to be added or subtracted from the
mixture.
[0026] The present invention can also provide new techniques for
real time air measurement applications and techniques for wet
concrete, including techniques using, or based at least partly on
determining gas volume fraction (GVF) for a mixture of concrete
that is ready mixed in a stationary mixer, a rotating drum mixer, a
pump boom or truck chute, application forms made in a precast
facility, a handheld unit.
[0027] For example, the apparatus may include a stationary mixer
having a wall with the acoustic-based air probe arranged therein,
including where the stationary mixer is configured with a central
chemical dosing location to allow for more even distribution of
chemicals into the mixing.
[0028] The apparatus may include a concrete pump boom having a wall
with the acoustic-based air probe arranged therein.
[0029] The apparatus may include a precast form having a wall with
the acoustic-based air probe arranged therein.
[0030] The apparatus may include a ready mix truck rotating drum
mixer having a wall with the acoustic-based air probe arranged
therein.
[0031] The apparatus may include a ready mix truck chute having a
wall with the acoustic-based air probe arranged therein.
[0032] The acoustic-based air probe may be configured to work in
conjunction with a signal processor that is configured to perform
one or more of the signal processing functions disclosed
herein.
[0033] The real time air measurement applications and/or signal
processing may include, or take the form of, the following:
[0034] For example, the apparatus may include the signal processor
that may be configured to receive the signaling containing
information about the acoustic signal injected into the mixture of
concrete; and determine a gas volume fraction of the mixture of
concrete based at least partly on a speed of sound measurement of
the acoustic signal that travels through the mixture, using a
SONAR-based technique, consistent with that set forth in the
aforementioned U.S. patent application Ser. No. 13/583,062, filed
12 Sep. 2012 (WFVA/CiDRA file nos. 712-2.338-1/CCS-0033, 35,40, and
45-49).
[0035] Alternatively, the signal processor may be configured to
receive the signaling containing information about the acoustic
signal injected into the mixture of concrete; and determine the
measurement of air percentage in the mixture of concrete based at
least partly on the dual frequency technique that depends on the
relationship between the acoustic signal injected and the signaling
received.
[0036] The dual frequency technique may include, or take the form
of, the signal processor being configured to determine the
measurement of air percentage in the mixture of concrete based at
least partly on mixing a reference signal with a detected signaling
using a phase sensitive lock-in approach.
[0037] Alternatively, the dual frequency technique may include, or
take the form of, the signal processor being configured to
determine the measurement of air percentage in the mixture of
concrete based at least partly on correlating the acoustic signal
injected and the signaling received.
[0038] According to some embodiments of the present invention, the
apparatus may form part of a handheld device, including where the
aforementioned acoustic-based air probe is configured on one end of
the handheld device and a handle is configured on the other end of
the handheld device.
The Handheld Acoustic-Based Air Probe
[0039] According to some embodiments, the apparatus may also
include, or take the form of, a handheld acoustic-based air probe
featuring an acoustic source configured to provide an acoustic
signal injected into a mixture of concrete; and an acoustic
receiver configured to respond to the acoustic signal, and provide
signaling containing information about the acoustic signal injected
into the mixture of concrete.
[0040] The handheld acoustic-based air probe may include one or
more of the following features:
[0041] The handheld acoustic-based air probe may include at least
one spacer strut configured to connect the acoustic source and the
acoustic receiver so as to form a space for receiving a portion of
the mixture of the concrete when the handheld acoustic-based air
probe is dipped into the mixture of concrete and the acoustic
signal is transmitted through the mixture. The at least one spacer
strut may include, or take the form of, three spacer struts that
are triangularly arranged and equally-spaced to connect the
acoustic source and acoustic receiver so as to form the space
in-between. The at least one spacer strut may include a wiring
channel for providing a wire from the acoustic receiver.
[0042] The handheld acoustic-based air probe may include a sealed
end cap assembly configured to contain the acoustic receiver in a
sealing manner.
[0043] The handheld acoustic-based air probe may include a sealed
assembly configured to contain the acoustic source in a sealing
manner. The sealed assembly may include a vibration isolated
actuator block configured to actuate the piston source. The
vibration isolated actuator block may include a voice coil actuator
moving coil assembly with an accelerometer transducer and a
stationary voice coil actuator field assembly. The sealed assembly
may include hemisphere vibration mounts configured between an
alignment cap and the vibration isolated actuator block and also
configured between the vibration isolated actuator block and the
acoustic source. The sealed assembly may include a spring seal,
including a cast urethane spring seal, configured between the
acoustic source and an acoustic source retaining member, and a
photo-etched flexure configured between the acoustic source and the
acoustic source retaining member. The sealed assembly may include a
temperature sensor configured to respond to the temperature of the
mixture.
[0044] The handheld acoustic-based air probe may include a second
acoustic receiver configured to respond to the acoustic signal, and
provide further signaling containing information about the acoustic
signal injected into the mixture of concrete. The second acoustic
receiver may be configured on the sealed assembly so as to receive
the acoustic signal that is reflected from the mixture of
concrete.
[0045] The acoustic source and the acoustic receiver may be
configured on one end of the handheld acoustic-based air probe. The
handheld acoustic-based air probe may include another end
configured with some combination of device handles, a normal
pressure sensor connector, an accelerometer connector and a
temperature and drive connector.
[0046] According to some embodiments, the apparatus may also
include an acoustic probe apparatus having two acoustic sources
configured to provide two reference signals, consistent with that
set forth herein.
The Signal Processor of Dual Frequency Techniques
[0047] According to some embodiments of the present invention, the
apparatus may include, or take the form of, a signal processor
configured to receive signaling containing information about an
acoustic signal injected into a mixture of concrete; and determine
a measurement of air percentage in the mixture of concrete based at
least partly on a dual frequency technique that depends on a
relationship between the acoustic signal injected and the signaling
received.
CCS-0067: Phase Sensitive Dual Frequency Lock-In Measurement for
Concrete Air Content With Quality Factor
[0048] According to some embodiments of the present invention, the
dual frequency technique may include the acoustic signal injected
being a reference signal; the signaling received being detected
signaling; and the signal processor may be configured to determine
the measurement of air percentage in the mixture of concrete based
at least partly on mixing the reference signal with the detected
signaling using a phase sensitive lock-in approach.
[0049] According to some embodiment of the present invention, the
signal processor may be configured to determine a resulting signal
based at least partly on the mixing of the reference signal with
the detected signaling; filter the resulting signal, including with
a low pass filter, to get a DC component; and determine a value
that is proportional to amplitude and phase components of the
detected signaling at the frequency of the reference signal. The
signal processor may also be configured to determine a
corresponding value that is proportional to corresponding amplitude
and phase components of the detected signaling with the frequency
of reference signal shifted by 90 deg. The signal processor may
also be configured to determine a signal phase difference based at
partly on the following: using .THETA.ref as a reference phase,
edet as a detected phase, Adet as a detected signal amplitude at a
frequency of interest; and determining a signal amplitude and the
signal phase difference using the following set of equations:
.THETA.=.THETA. det-.THETA.ref,
X.about.Adet cos(.THETA.),
Y.about.Adet cos(.THETA.+90 deg)=Adet sin(.THETA.),
Signal amplitude=Adet=(X.sup.2*Y.sup.2).sup.1/2, and
Signal phase difference=.THETA.=tan.sup.-1(Y/X).
The signal processor may be configured to determine a time of
propagation of the reference signal in the mixture of concrete and
then a speed of sound measurement, based at least partly on the
signal phase difference determined along with the frequency.
[0050] According to some embodiment of the present invention, the
signaling may contain information about two reference signals that
are injected into the mixture of concrete at different frequencies
in order correct or compensate for ambiguity that may otherwise
exist once the detected signaling has gone though a propagation
time equal to 2*pi of a single injected acoustic signal, including
any multiple thereof; and the signal processor is configured to
determine a relative phase between the two reference signals in
order correct or compensate for the ambiguity.
[0051] According to some embodiments of the present invention, the
signal processor may be configured to determine a quality metric
based at least partly on the signal amplitude and signal phase
difference determined. For example, the signal processor may be
configured to take the signal amplitude of a signal of interest at
Asig; take a sample of four other comparison signals spaced
adjacent thereto of A0, A1, A2 and A3; average four other
comparison signals to obtain an adjacent noise
Anoise=(A0+A1+A2+A3)/4; and take a difference over a sum
normalization to determine a quality signal, Q, that varies between
-1 to 1 based at least partly on using the following equation:
Q=(Asig-Anoise)/(Asig+Anoise),
[0052] with a ratio of "1" representing a good quality, a ratio of
"0" indicating same signal strength at frequency of interest as
other frequencies, and a ratio of "-1" as a very weak signal of
interest.
CCS-0104
[0053] According to some embodiments of the present invention, the
dual frequency technique may include the signal processor being
configured to determine the measurement of air percentage in the
mixture of concrete based at least partly on correlating the
acoustic signal injected and the signaling received.
[0054] According to some embodiments of the present invention, the
signal processor may be configured to determine a phase delay due
to a transit of the acoustic signal injected in the mixture of
concrete based on the correlating of the acoustic signal injected
and the signaling received. The signal processor may be configured
to determine the speed of sound based on the phase delay. The
signaling containing information about the acoustic signal injected
into the mixture of concrete may be based at least partly on using
a simple sweep of an excitation frequency to an acoustic actuator,
which increases the sensitivity of a correlation process. The
simple sweep may be based on the equation:
Y(i)=A sin(a i.sup.2/2+b i).
[0055] According to some embodiments of the present invention, the
signaling containing information about the acoustic signal injected
into the mixture of concrete may be based at least partly on one or
more techniques of encoded pulsing that are used to alternatively
enhance the signal-to-noise of a detected acoustic signal. The
encoded pulsing may be based at least partly on a pseudo-random
sequence (PRBS), where the PRBS is defined as a sequence of N bits
where an autocorrelation of the sequence gives a number
proportional to the number of "on" bits times the sequence length
when there is no misalignment and a low number proportional to only
the number of on bits when misaligned. The PRBS in the case of
free-space acoustic measurements may be based at least partly on
PRBS excitation that can be created by turning on and off an
excitation acoustic wave according to the PRBS sequence, or by
frequency modulating the acoustic signal by the PRBS sequence. The
signaling containing information about the acoustic signal injected
into the mixture of concrete may be based at least partly on
frequency encoding, including m-sequence codes or frequency shift
keying approaches.
Methods
[0056] According to some embodiments of the present invention, the
present invention may take the form of a method that may include,
or take the form of, steps for receiving in a signal processor
signaling containing information about an acoustic signal injected
into a mixture of concrete; and determining in the signal processor
a measurement of air percentage in the mixture of concrete based at
least partly on a dual frequency technique that depends on a
relationship between the acoustic signal injected and the signaling
received. According to some embodiments of the present invention,
the method may include determining in the signal processor the
measurement of air percentage in the mixture of concrete based at
least partly on mixing a reference signal with a detected signaling
using a phase sensitive lock-in approach. According to some
embodiments of the present invention, the method may include
determining in the signal processor the measurement of air
percentage in the mixture of concrete based at least partly on
correlating the acoustic signal injected and the signaling
received. These methods may also include one or more of the
features set forth herein.
[0057] According to some embodiments of the present invention, the
method may include, or take the form of, steps for vibrating with
one part of a handheld vibration assembly a wet concrete medium;
and responding with another part of the handheld vibration assembly
to the wet concrete medium being vibrated in order to provide
signaling containing information about the wet concrete medium
being vibrated to be used to determine entrained air in the wet
concrete medium.
[0058] This method may also include some combination of the
following features:
[0059] The signaling may be provided as output signaling from on
the handheld vibration assembly to be received and used by a signal
processor to determine entrained air in the wet concrete
medium.
[0060] The step of vibrating may include actuating a vibration
isolated actuator block assembly that forms part of the handheld
vibration assembly.
[0061] The method may also include responding to the concrete
medium being vibrated with at least one pressure transducer that
forms part of the handheld vibration assembly, or providing from
the at least one pressure transducer the signaling, or responding
to the vibrating concrete medium with two pressure transducers that
forms part of the handheld vibration assembly, and/or providing the
signaling from the two pressure transducers.
[0062] The method may also include determining a measurement of the
entrained air in wet concrete, including using SONAR-based
technique to determine the measurement.
[0063] The method may include adding chemicals to control the
entrained air in wet concrete based at least partly on the
signaling.
[0064] The signaling may be wireless signaling.
[0065] The signaling may be displayed on the handheld vibration
assembly.
[0066] The signal processor may be configured with at least one
processor and at least one memory including computer program code,
the at least one memory and computer program code configured, with
the at least one processor, to cause the apparatus at least to
determine the entrained air in the wet concrete medium.
[0067] The method may include responding to a user command
containing information about vibrating with the handheld vibration
assembly the wet concrete medium.
[0068] The user command may include input signaling received by the
handheld vibration assembly.
[0069] The user command may be provided by pressing a button on the
handheld vibration assembly.
[0070] The method may include vibrating a floating mass that forms
part of a vibration isolated actuator assembly at a frequency in a
range of about 100-500 Hz.
[0071] The present invention makes important contributions to this
current state of the art for real time air measurement in wet
concrete, as well as techniques to control the amount of air in a
mixture of concrete.
BRIEF DESCRIPTION OF THE DRAWING
[0072] The drawing includes FIGS. 1-6c, which are not necessarily
drawn to scale, as follows:
[0073] FIG. 1a is a perspective view of an acoustic probe that may
implemented some embodiments of the present invention.
[0074] FIG. 1b is an axial view of one end the acoustic probe shown
in FIG. 1a.
[0075] FIG. 1c is an axial view of another end the acoustic probe
shown in FIG. 1a.
[0076] FIG. 1d is a sectional view of the end the acoustic probe
shown in FIG. 1c along section lines A-A.
[0077] FIG. 1e is a sectional view of the end the acoustic probe
shown in FIG. 1c along section lines B-B.
[0078] FIG. 2a is a diagram of a stationary mixer having a new
dosing location in the center of the mixer to allow for an even
distribution of chemicals during mixing, according to some
embodiment of the present invention.
[0079] FIG. 2b is a diagram of a GVF meter installed on a pump boom
for real time air information in concrete while it is being pumped,
according to some embodiments of the present invention.
[0080] FIG. 3a is a diagram of a handheld acoustic probe, according
to some embodiments of the present invention.
[0081] FIG. 3b is an axial view of the handheld acoustic probe
shown in FIG. 3a, according to some embodiments of the present
invention.
[0082] FIG. 3c is a cross-sectional view of the handheld acoustic
probe shown in FIG. 3b along section lines A-A, according to some
embodiments of the present invention.
[0083] FIG. 3d is an enlarged view of a part of the handheld
acoustic probe shown in FIG. 3c and labeled B, according to some
embodiments of the present invention.
[0084] FIG. 4 is a block diagram of apparatus having a signal
processor, according to some embodiment of the present
invention.
[0085] FIG. 5a is a graph of a single frequency being injected into
a mixture of concrete, according to some embodiment of the present
invention.
[0086] FIG. 5b is a graph of two frequencies having a frequency
difference being injected into a mixture of concrete, according to
some embodiment of the present invention.
[0087] FIG. 6a is a graph of an example of a correlation function
if there is strong system noise present and some of that noise
coincides with a frequency of actuation.
[0088] FIG. 6b is a graph of an example of a correlation function
if there is strong system noise present and a sweep of the
excitation frequency is provided to an actuator.
[0089] FIG. 6c is a graph of an example of a further correlation
function when a PRBS encoded oscillation is used in the presence of
a large noise system. provided to an actuator.
DETAILED DESCRIPTION OF BEST MODE OF THE INVENTION
CCS-0075: FIGS. 1a-2b, Real Time Air Measurement Applications in
Wet Concrete
[0090] FIGS. 1a to 1e show the present invention in the form of
apparatus generally indicated as 100 that may include an
acoustic-based air probe like element 101. The acoustic-based air
probe 101 may include an acoustic source generally indicated as 102
(see FIG. 1d) configured to provide an acoustic signal into a
mixture of concrete; and an acoustic receiver generally indicated
as 104 (see FIG. 1e) configured to be substantially co-planar with
the acoustic source 102, to respond to the acoustic signal, and to
provide signaling containing information about the acoustic signal
injected into the mixture of concrete. By way of example, the
acoustic source 102 may consist of an arrangement of parts and
components and is best shown in detail in FIG. 1d. By way of
example, the acoustic receiver 104 may consist of at least an
arrangement of one or more transducers and fills and is best shown
in FIG. 1e.
[0091] The acoustic-based air probe 101 may include a planar
probing surface 106 having a first aperture 106a formed therein
configured to receive part of the acoustic source 102, including a
hardened steel piston 122, as best shown in FIG. 1d. At the
interface with the planar probing surface 106, the hardened steel
piston 122 is surrounded by a circumferential channel 122a, so as
not to be in physical contact with the planar probing surface 106.
The planar probing surface 106 may include at least one second
aperture 106b, 106c formed therein configured to receive at least
one part 104', 104'' of the acoustic receiver 104. The part 104',
104'' are shown as a protective polyurethane rubber member in FIG.
1e. The planar probing surface 106 may be configured as a hardened
steel face plate, although the scope of the invention is intended
to include using other type or kinds of materials either now known
or later developed in the future. The acoustic receivers 104 are
configured in relation to the center of the hardened steel piston
122 of the acoustic source 102 and defined by a radius R, as best
shown in FIG. 1c, so that the acoustic receivers 104 are arranged
and configured substantially on the circumference of a circle
defined by the radius R from the center of the hardened steel
piston 122.
[0092] The acoustic receiver 104 may include, or take the form of,
a dynamic pressure transducer, as best shown in FIG. 1e.
[0093] In operation, and by way of example, the acoustic receiver
104 may be configured to receive acoustic signals, e.g., having a
frequency in a range of about 100-500 Hz, including 330 Hz,
although the scope of the invention is intended to include using
other frequencies and other ranges either now known or later
developed in the future.
[0094] By way of example, the acoustic source 102 may include, or
take the form of, or be configured as, a floating mass, consistent
with that shown in FIG. 1d. In FIG. 1d, the acoustic source 102 is
shown in the form of a piston module assembly 120 having the rigid
hardened steel piston 122 configured with a channel 124 to receive,
or be coupled to, a piston shaft 126. The acoustic-based air probe
101 has a base plate disk 125 that contains the piston module
assembly 120, as well as other components in FIG. 1d. The rigid
hardened steel piston 122 is enclosed, surrounded and configured to
move in relation to a low durometer cast silicone rubber 123 and
photo-etched flexures 127, so as to provide the floating mass
aspect of the acoustic source 102. The low durometer cast silcone
rubber 123 may also be configured to perform sealing functionality
in relation to the mixture of the concrete. The acoustic source 102
may also include a vibration isolated actuator block assembly 128,
best identified in FIG. 1b, having a stationary voice coil actuator
field assembly 130 in combination with a voice coil actuator field
assembly 132 having an accelerometer transducer configuration. The
vibration isolated actuator block assembly 128 may be configured to
drive and vibrate the piston shaft 126, consistent with that shown
in FIG. 1d, so as to provide the acoustic signal to the mixture of
the concrete when the acoustic-based air probe is inserted into the
mixture. The apparatus 100 may also be configured with signal
processing technology (not shown) for driving the acoustic source
102, as would be appreciated by a person skilled in the art.
[0095] The acoustic-based air probe 101 may include a fluid/media
temperature sensor 134, consistent with that shown in FIG. 1d,
configured to provide a temperature reading of the mixture.
[0096] The acoustic-based air probe 101 may include a voice coil
temperature sensor 136, consistent with that shown in FIG. 1d,
configured to provide a temperature reading of the stationary voice
coil actuator field assembly 130. The acoustic-based air probe 101
may include two acoustic receivers 104, 104', that may take the
form of the two dynamic pressure transducers, consistent with that
shown in FIG. 1e.
[0097] The acoustic-based air probe 101 may include some
combination of a connector/wiring cover plate 140, and various
connectors configured in relation to the same, including a pressure
sensor no. 1 connector 142 for providing the signaling in relation
to one pressure sensor, a pressure sensor no. 2 connector 144 for
providing the signaling in relation to the other pressure sensor, a
voice coil drive connector 146 for providing the signaling in
relation to the voice coil drive 130 (FIG. 1d), a temperature
sensor connector 148 for providing the signaling in relation to a
temperature, and an accelerometer connector 150 for providing the
signaling in relation to the voice coil actuator moving coil
assembly 132 (FIG. 1d), all shown in FIG. 1b.
Applications
[0098] The apparatus 100 may include, or take the form of, a
stationary mixer 20 having a wall 20a with the one or more
acoustic-based air probes 101 arranged therein, including where the
stationary mixer 20 is configured with a central chemical dosing
location 20b to allow for more even distribution of chemicals into
the mixing. In FIG. 2a, the acoustic-based air probe or measurement
device 101 according to the present invention, is shown arranged in
a precut hole 20c of the stationary mixer 20. Instrumenting the
stationary mixer 20 with more than one air meter or acoustic-based
air probe 101 (for example: one on the left side and one on the
right side) will help in understanding the mixing efficiency and
performance of a particular mixer. With this information different
techniques may be implemented to improve homogeneity of the entire
mixed batch. The addition of the admix chemicals made may need to
be spread (sprayed) more evenly throughout the mixing area rather
than streamed in one location. Or the more centralized dosing
location 20b may also be an improvement on current methodology.
[0099] The apparatus 100 may also include dosing apparatus (not
shown) configured to respond to the signaling, and provide a
control signal to control the dosing of a chemical to be added or
subtracted from the mixture, e.g., including to the dosing location
20a shown in FIG. 2a.
[0100] The apparatus 100 may include a concrete pump boom having a
wall with the acoustic-based air probe arranged therein, consistent
with that shown in FIG. 2b.
Precast Applications
[0101] Form Application--Forms used in a precast facility would
benefit from being instrumented with entrained air measurement
capability. This would enable a concrete producer to measure
entrained air levels in concrete as the form is being filled. This
will also give them an understanding of how much air is lost from
the concrete mixer to placement into the form and will enable
better planning to meet air specification. According to some
embodiments of the present invention, the apparatus 100 may
include, or take the form of, a precast form (not shown) having a
wall with the acoustic-based air probe 101 arranged therein.
Ready Mix Applications
[0102] Pumping Application--Ready Mix Boom Pump--This application
can utilize the known SONAR-based SOS GVF meter developed by the
assignee of the instant patent application may also be used for
real time entrained air information in the concrete as it is being
pumped in order to control and understand air levels in wet
concrete, which is very important. Too much air will effect
strength and too little air will effect the durability
(freeze/thaw) of the concrete. Since a great deal of ready mix
concrete is pumped into place at job sites every day, it is
important to know how the pumping of entrained air concrete can
effect the air content in concrete. Once the air level in the
concrete is understood at placement the appropriate adjustments can
be made further upstream to compensate for the air loss during
pumping. Theories concerning air losses within the concrete mix
during pumping include: the large drop within the boom, high
pressure within the pipes, pump configurations and attachments and
the materials used in the concrete mix.
[0103] Ready Mix Stationary Central Mixer: The known SONAR-based
SOS technology developed by the assignee of the instant patent
application may also be used for real time air information in ready
mix stationary central mixers. In many areas of the world
(especially Europe), the wet batching process utilizes stationary
mixers.
[0104] Ready Mix Truck Rotating Drum Mixer: The known SONAR-based
SOS technology developed by the assignee of the instant patent
application may also be used for ready mix truck rotating drum
mixer or stationary mixers. The primary difference will be that
this unit can be battery operated and will transmit the real time
air data wirelessly. This information will enable every batch of
ready mix concrete to arrive at the job site within air
specification. According to some embodiments of the present
invention , the apparatus 100 may include, or take the form of, a
ready mix truck rotating drum mixer (not shown) having a wall with
the acoustic-based air probe 101 arranged therein.
[0105] Air level will be monitored the entire travel time and can
be adjusted if necessary by chemical addition.
[0106] Ready Mix Rotating Drum Central Mixer: These central mixers
are very similar to the truck mixers, only usually a little larger.
The rotating drum central mixers are usually 10-12 yards in size.
Real time air information will allow for precise control of air
before the batch is dumped into the truck.
[0107] Ready Mix Truck Chute Application: Ready mix truck delivery
chute for real time air information. This would be mounted in such
a way that an air measurement would be made as the concrete passes
over it as it exits the truck. According to some embodiments of the
present invention, the apparatus 100 may include, or take the form
of, a ready mix truck chute (not shown) having a wall with the
acoustic-based air probe 101 arranged therein.
[0108] Form Application, including Ready Mix Forms: This
application may take the form of a disposable devise that could
make an air measurement of the wet concrete after the form is
filled.
FIGS. 3a to 3d: Handheld Unit or Acoustic-Based Air Probe
[0109] FIGS. 3a to 3d show the present invention as apparatus in
the form of a handheld unit or acoustic-based air probe 50,
according to some embodiments of the present invention. The
acoustic-based air probe 50 may be configured with a probe portion
52 and a handle portion 54. The handheld unit or acoustic probe 50
can be used both in precast and ready mix once concrete is poured
into any form. The probe portion 52 of the handheld unit 50 may be
submerged or dipped into the concrete, a noise source activated
therein and sound speed measurement made, consistent with that
disclosed herein. This technique may potentially take the place of,
or augment or compliment, a known Type B pressure pod currently
utilized in and by the industry.
[0110] The probe portion 52 may be configured with an acoustic
source 56 configured to provide an acoustic signal injected into a
mixture of concrete; and an acoustic receiver 58 configured to
respond to the acoustic signal, and provide signaling containing
information about the acoustic signal injected into the mixture of
concrete. In FIG. 3d, the acoustic source 56 is shown in the form
of a piston acoustic source, and the acoustic receiver 58 is shown
in the form of a dynamic pressure transducer, although the scope of
the invention is intended to include other types or kind of
acoustic sources and acoustic receivers either now known or later
developed in the future.
[0111] The probe portion 52 may also be configured with at least
one spacer strut 60 configured to connect one member 62 of the
probe portion 52 having the acoustic source 56 to the other member
64 of the probe portion 52 having the acoustic receiver, so as to
form a space in-between configured for receiving a portion of the
mixture of the concrete when first and second members 62, 64 of the
probe portion 52 are dipped into the mixture of concrete and the
acoustic signal is transmitted through the mixture. The at least
one spacer strut 60 may include three spacer struts that are
triangularly arranged and equally-spaced to connect the acoustic
source and acoustic receiver so as to form the space in-between, as
shown in FIGS. 3c and 3d, although the scope of the invention is
intended to include using one strut, two struts, four struts, etc.
The scope of the invention is not intended to be limited to the
number of strut(s) being used, or the physical arrangement of the
struts in relation to one another. The at least one spacer strut 60
may be configured with a wiring channel 60a for providing a wire
from the acoustic receiver 58, as best shown in FIG. 3c.
[0112] The member 64 of the probe portion 52 may include a sealed
end cap assembly 60a configured to contain the acoustic receiver in
a sealing manner. The member 62 of the probe portion 52 may include
a sealed assembly 62a configured to contain the acoustic source 56
in a sealing manner. The sealed assembly 62a may include a
vibration isolated actuator block 62b configured to actuate the
piston acoustic source 56. The vibration isolated actuator block
62b may include a voice coil actuator moving coil assembly 62c with
an accelerometer transducer and a stationary voice coil actuator
field assembly 62d. The sealed assembly 62a may include hemisphere
vibration mounts 60e configured between an alignment cap 60f and
the vibration isolated actuator block 62b and also configured
between the vibration isolated actuator block 62b and the acoustic
source 56, as best shown in FIG. 3d. The sealed assembly 62a may
include a spring seal 62g, including a cast urethane spring seal,
configured between the acoustic source 56 and an acoustic source
retaining member 62h, and a photo-etched flexure 62i configured
between the acoustic source 56 and the acoustic source retaining
member 62h.
[0113] The member 62 of the probe portion 52 may include a second
acoustic receiver 60j configured to respond to the acoustic signal,
and provide further signaling containing information about the
acoustic signal injected into the mixture of concrete. The second
acoustic receiver 60j may be configured on the sealed assembly 62a
so as to receive the acoustic signal that is reflected from the
mixture of concrete. In contrast, the acoustic receiver 58 may be
configured so as to receive the acoustic signal that is transmitted
directly through the mixture of concrete.
[0114] The sealed assembly may also include a temperature sensor
60k configured to respond to the temperature of the mixture.
[0115] The handle portion 54 on the other end of the handheld
acoustic-based air probe may be configured with some combination of
device handles 54a, a normal pressure sensor connector 54b, an
accelerometer connector 54c and a temperature and drive connector
54d, as best shown in FIGS. 3a and 3b.
[0116] According to some embodiments, the handheld acoustic-based
air probe 50 may include a signal processor configured to perform
the signal processing functionality consistent with that disclosed
herein.
[0117] By way of example, the signal processor may be configured to
determine the measurement of air percentage in the mixture of
concrete based at least partly on using other types or kinds of
SONAR-based techniques either now known or later developed in the
future, according to some embodiments of the present invention, and
consistent with that disclosed herein.
[0118] Alternatively, the signal processor may be configured to
receive signaling containing information about an acoustic signal
injected into a mixture of concrete, e.g., from the acoustic
receiver 58 (see FIG. 3c); and determine a measurement of air
percentage in the mixture of concrete based at least partly on a
dual frequency technique that depends on a relationship between the
acoustic signal injected, e.g., by the acoustic source 56, and the
signaling received, according to some embodiments of the present
invention, and consistent with that disclosed herein.
[0119] Alternatively, the acoustic signal injected may be a
reference signal; the signaling received may be detected signaling;
and the signal processor may be configured to determine the
measurement of air percentage in the mixture of concrete based at
least partly on mixing the reference signal with the detected
signaling using a phase sensitive lock-in approach, according to
some embodiments of the present invention, and consistent with that
disclosed herein.
[0120] Alternatively, the signal processor may be configured to
determine the measurement of air percentage in the mixture of
concrete based at least partly on correlating the acoustic signal
injected and the signaling received, according to some embodiments
of the present invention, and consistent with that disclosed
herein.
[0121] The scope of the invention is intended to be limited to the
way or technique that the signal processor in the handheld
acoustic-based air probe determines the measurement of air
percentage in the mixture of concrete. By way of example, the
signal processor may be configured or arranged in an intermediate
portion 55 of the handheld unit 50, although the scope of the
invention is intended to include configuring the signal processor
somewhere else in the probe 50.
[0122] According to some embodiments, the handheld acoustic-based
air probe 50 may provide the signaling containing information about
an acoustic signal injected into a mixture of concrete, e.g., from
the acoustic receiver 58, to a signal processor that is external
to, and does not form part of, the handheld acoustic-based air
probe 50, which determines the measurement of air percentage in the
mixture of concrete based at least partly on one or more of the
signal processing techniques disclosed herein.
[0123] So as not to clutter up FIGS. 3a to 3d, each Figures does
not include every reference numeral used to identify every elements
shown therein.
[0124] Moreover, according to some embodiments of the present
invention, the known type B canister in the art or another shaped
canister may be configured or instrumented with speed of sound
measurement capability. This would be a sampling method that would
enable an air measurement within seconds rather than minutes.
CCS-0067 and 0104, FIG. 4: The Signal Processor of Dual Frequency
Techniques
[0125] FIG. 4 shows apparatus generally indicated as 10 according
to some embodiments of the present invention. The apparatus 10 may
include a signal processor 10a that receives signaling containing
information about an acoustic signal injected into a mixture of
concrete; and determines a measurement of air percentage in the
mixture of concrete based at least partly on a dual frequency
technique that depends on a relationship between the acoustic
signal injected and the signaling received.
[0126] By way of example, and consistent with that described
herein, the functionality of the signal processor 10a may be
implemented using hardware, software, firmware, or a combination
thereof, although the scope of the invention is not intended to be
limited to any particular embodiment thereof. In a typical software
implementation, the signal processor would be one or more
microprocessor-based architectures having a microprocessor, a
random access memory (RAM), a read only memory (ROM), input/output
devices and control, data and address buses connecting the same. A
person skilled in the art would be able to program such a
microprocessor-based implementation to perform the functionality
set forth in the signal processing block 10a, such as determining
the gas volume fraction of the aerated fluid based at least partly
on the speed of sound measurement of the acoustic signal that
travels through the aerated fluid in the container, as well as
other functionality described herein without undue experimentation.
The scope of the invention is not intended to be limited to any
particular implementation using technology now known or later
developed in the future. Moreover, the scope of the invention is
intended to include the signal processor being a stand alone
module, as shown, or in the combination with other circuitry for
implementing another module.
[0127] It is also understood that the apparatus 10 may include one
or more other modules, components, circuits, or circuitry 10b for
implementing other functionality associated with the apparatus that
does not form part of the underlying invention, and thus is not
described in detail herein. By way of example, the one or more
other modules, components, circuits, or circuitry 10b may include
random access memory, read only memory, input/output circuitry and
data and address buses for use in relation to implementing the
signal processing functionality of the signal processor 10a, or
devices or components related to mixing or pouring concrete in a
ready-mix concrete truck or adding chemical additives, etc.
[0128] Consistent with that set forth in relation to FIGS. 5a-5b,
the acoustic signal injected may be a reference signal; the
signaling received may be detected signaling; and the signal
processor may be configured to determine the measurement of air
percentage in the mixture of concrete based at least partly on
mixing the reference signal with the detected signaling using a
phase sensitive lock-in approach.
[0129] Alternatively, consistent with that set forth in relation to
FIGS. 6a to 6c, the signal processor may be configured to determine
the measurement of air percentage in the mixture of concrete based
at least partly on correlating the acoustic signal injected and the
signaling received.
CCS-0067: FIGS. 5a-5b, Phase Sensitive Dual Frequency Lock-In
Measurement for Concrete Air Content With Quality Factor
[0130] One approach to the measurement of air percentage in
concrete is to measure the speed of sound (SOS) in the mixture and
then through the use of the Wood's equation to calculate the amount
of gas present. Various acoustic speed of sound measurements used
in relation to SONAR-based technology as well as other sound
receiving technology are set forth below with numerous patents
disclosing this technology. This measurement of air percentage in
concrete can be very difficult in materials like concrete where
acoustic waves will quickly die out in strength due to the
material's constituents along with other factors. This can be
overcome by injecting a strong acoustic signal into the mixture at
one point and then timing the signal propagation through a
representative section of the material. However, this approach
requires significant amounts of energy to produce a large
compression wave in the concrete.
[0131] According to some embodiments of the present invention, a
variation of this approach may be implemented that would require a
modest acoustic signal to be injected but a very sensitive
detection technique that can pull the injected signal out of the
other acoustic "noise" that is present in the system. One detection
technique that is well suited for this is a phase sensitive lock-in
approach.
[0132] In a lock-in approach, a reference signal may be injected
into the mixture and that same signal may be mixed with a resultant
detected signal from the mixture. After a low pass filter is used
to get the DC component of the result, a value may be obtained that
is proportional to the amplitude and phase of the detected signal
at the reference frequency. If the same calculation is made with
the reference shifted by 90 deg, the phase and amplitude components
can be separately determined. If one takes .THETA.ref as the
reference phase, .THETA.det as the detected phase, Adet as the
detected signal amplitude at the frequency of interest, then the
signal amplitude and the signal phase difference may be determined
using the following set of equations:
.theta.=.THETA.det-.THETA.ref,
X.about.Adet cos(.THETA.),
Y.about.Adet cos(.THETA.+90 deg)=Adet sin(.THETA.),
Signal amplitude=Adet=(X.sup.2*Y.sup.2).sup.1/2, and
Signal phase difference=.THETA.=tan.sup.-1(Y/X).
The signal phase difference calculated along with the frequency can
then be used to determine the time of propagation of the signal in
the material and then the SOS.
Ambiguity in the Detected Acoustic Signal
[0133] However, an ambiguity exists once the detected signal has
gone though a propagation time equal to 2*pi of the injected signal
(or any multiple). This can be somewhat prevented by assuring that
the frequency used for injection is low enough that the time delay
can not introduce the ambiguity, however this will severely
restrict the operational range of the measurement. Variations in
the air content along with the attenuation characteristic of the
materials may force the system to operate in a region where the
ambiguity will exist. This can be prevented by injecting two
slightly different frequencies into the material and then detecting
each to determine the relative phase between the two injected
signals, e.g., using the acoustic probe shown in FIGS. 1a to 1e
that include two dynamic transducers shown in FIG. 1e. An ambiguity
can still exist but it will be a function of the difference of the
two injected signals rather than just the single injected
frequency. This can be seen through the illustrations in FIGS. 5a
and 5b. In FIG. 5a, the period of the single frequency is seen to
be about 10 counts, this is the "distance" that can be measured
with this system without ambiguity. In FIG. 5b, where there are 2
signals at a 10% frequency difference, now the overriding "beat"
frequency determines the point at which the distance becomes
ambiguous. This can be seen at about 325 counts, a very large
extension of the range of the system.
[0134] An additional issue with a system such as this which
calculates a SOS is the reliability of the calculation. The lock-in
scheme above will always give a number for the phase delay and
therefore the SOS but an indication or quality factor is needed to
be able to gauge the reliability of that calculation. Since from
the phase calculation the amplitude of the signal may also be
obtained, this can be used for calculation of a quality metric. If
one takes the amplitude of the signal at the injected frequency and
compares that to several amplitudes of signals around that
frequency, then one can get an indication of how the signal of
interest is, or relates, to the surrounding "noise". If one takes
the amplitude of the signal of interest at Asig and also take a
sample of four other signals spaced adjacent to the original of A0,
A1, A2 and A3, then one can average the four comparison signals and
consider this the adjacent noise Anoise=(A0+A2+A2+A3)/4. A
difference over sum normalization will give one a quality signal,
Q, that varies between -1 to 1. With 1 representing a good quality,
a 0 indicating same signal strength at frequency of interest as
other frequencies and a -1 as a very weak signal of interest.
Q=(Asig-Anoise)/(Asig+Anoise).
CCS-104: FIGS. 6a-6c, Additional Concrete and Free Space Acoustic
Measurement Techniques to Improve Signal Range and Signal to
Noise
[0135] The present invention, according to some embodiments, also
provides further techniques that builds upon the aforementioned
disclosure describing the dual frequency method for extending the
unambiguous range as well as the sensitivity of the concrete
(free-space acoustics) signal detection. As mentioned, several
techniques in addition to the lock-in approach that can be utilized
for increasing the sensitivity and accuracy of the speed of sound
detection beyond the current single wave correlation
techniques.
[0136] If one takes a look at the basic technique, a single
frequency acoustic wave is introduced into the mixture to be
measured by way of an actuator. A detector is situated a known
distance away and it will detect the introduced acoustic wave along
with all the background acoustic noise in the system. In many
situations the background acoustic noise can be much larger than
the actuated signal making detection very difficult. However, by
correlating the detected signal with the actuated signal any phase
delay due to the transit time of the acoustic wave in the material
can be determined and the subsequent speed of sound can be
calculated. Using the correlation helps to detect only the signal
of interest and works well provided that the system noise is not
too overwhelmingly strong and does not have significant frequency
content at the actuation frequency. FIG. 6a shows what the
correlation function could look like if there is strong system
noise present and some of that noise coincides with the frequency
of the actuation. One way to mitigate the distortion and errors
associated with the system noise is to utilize several frequencies
in the excitation. The dual frequency lock-in technique provided
benefits related to dual frequency excitation, but this concept can
be extended even further to the use of a continuum of frequencies.
A simple sweep of the excitation frequency fed to the actuator can
greatly increase the sensitivity of the correlation process by
reducing the effects of the system noise and specifically reduce
the degradation caused by system acoustic tones that may be
present. Such a sweep can be described by:
Y(i)=A sin(a i.sup.2/2+b i).
[0137] The same correlation processing can be utilized with the
frequency sweep, FIG. 6b shows a correlation function obtained with
strong system noise present.
[0138] Additional techniques such as encoded pulsing can be used to
alternatively enhance the signal-to-noise of the detected acoustic
signal. One such encoding is through the use of a pseudo-random
sequence (PRBS). A PRBS is defined as a sequence of N bits where
the autocorrelation of the sequence gives a number proportional to
the number of on bits times the sequence length when there is 0
misalignment and a low number proportional to only the number of on
bits when misaligned. This property makes it particularly suitable
for use when a correlation is used to detect a low level signal.
Due to the random nature of the signal encoding the probability
that system acoustic noise will mimic the encoded signal is
practically nil and a very strong correlation will be seen. FIG. 6c
shows the further improved correlation function when a PRBS encoded
oscillation is used in the presence of large system noise.
[0139] As can be seen with the encoded techniques a very good
signal-to-noise can be achieved.
[0140] In the case of free-space acoustic measurements, the PRBS
excitation can be created in a variety of ways such as turning on
and off the excitation acoustic wave according to the PRBS
sequence, or by frequency modulating the acoustic signal by the
PRBS sequence. Other types of frequency encoding can be utilized
such as m-sequence codes or frequency shift keying approaches.
The SONAR-Based Technology
[0141] The new techniques for impact and coherent noise sources for
acoustic speed of sound measurements, including such acoustic speed
of sound measurements used in relation to SONAR-based technology as
well as other sound receiving technology as shown and described
herein. By way of example, the SONAR-based entrained air meter may
take the form of SONAR-based meter and metering technology
disclosed, e.g., in whole or in part, in U.S. Pat. Nos. 7,165,464;
7,134,320; 7,363,800; 7,367,240; and 7,343,820, all of which are
incorporated by reference in their entirety.
A. Introduction
[0142] The known SONAR-based technology includes a gas volume
fraction meter (known in the industry as a GVF-100 meter) that
directly measures the low-frequency sonic speed (SOS) of the liquid
or slurry flowing through a pipe. By way of example, the
SONAR-based entrained air meter may take the form of SONAR-based
meter and metering technology disclosed, e.g., in whole or in part,
in U.S. Pat. Nos. 7,165,464; 7,134,320; 7,363,800; 7,367,240; and
7,343,820, all of which are incorporated by reference in their
entirety. Using the Wood's equation, the volume percent of any gas
bubbles or the gas void fraction (GVF) is determined from the
measured SOS. The Wood's equation requires several other inputs in
addition to the measured SOS of liquid/gas mixture. One of the
additional inputs in particular, the static pressure of the
liquid/gas mixture, can be very important for an accurate
calculation of the GVF. To a first order, if the static pressure
used for the GVF calculation differs from the actual static
pressure of the liquid/gas mixture, then the calculated GVF may
typically differ from the actual GVF by 1% as well. For
example:
[0143] Static Pressure used for GVF calculation=20 psia
[0144] Calculated GVF=2%
[0145] Actual Static Pressure=22 psia
[0146] Static pressure error=22/20-1=0.1=10%
[0147] Actual GVF=2%.times.(1+0.1)=2.2% (10% error)
[0148] In many cases, the static pressure of the liquid/gas mixture
is available through existing process plant instrumentation. In
this case, the measured static pressure can be input directly to
the GVF calculation through, e.g., an analog 4-20 mA input in the
SONAR-based gas volume fraction transmitter (e.g. GVF-100 meter).
Alternatively, a correction to the calculated GVF can be made in
the customer DCS for any variation from the fixed pressure that was
used to originally calculate the GVF.
[0149] In other cases, a static pressure transmitter can be added
to the process plant specifically to measure the static pressure
used for the GVF calculation. The measured pressure can either be
input to the SONAR-based gas volume fraction transmitter (e.g.,
GVF-1200) or correction made in the DCS as described above.
Occasionally, a the SONAR-based gas volume fraction meter (e.g.,
GVF-100) may be installed at a location in the process that does
not already have a static pressure gauge installed and it is
impractical to add one. This could be a location where there is no
existing penetration of the pipe to sense the pressure and it would
be difficult or expensive to add one. In the case, where a
traditional pressure gauge is not available and it is desirable to
have a static pressure measurement the following description of a
non-intrusive (clamp on) static pressure measurement could be
used.
B. Description
[0150] For example, according to some embodiments of the present
invention, a non-intrusive static pressure measurement may be
sensed using traditional strain gauges integrated into the sensor
band of the SONAR-based gas volume fraction sensing technology
(e.g. the known GVF-100 meter). As the static pressure inside the
pipe changes, the static strain on the outside of the pipe also
changes. Using a thin-wall assumption for simplicity (t/R<10,
where t is the wall thickness and R is the radius) the tangential
strain due to internal static pressure is: .epsilon.=pR/Et, where
.epsilon. is the tangential strain (inch/inch), R is the radius
(inch), E is the modulus of elasticity (lb/in2) and t is the wall
thickness (inch). The radius, wall thickness and modulus is
generally known, or at least constant and so if the tangential
strain is measured the internal static pressure can be
determined.
[0151] By way of example, according to one embodiment of the
present invention, four strain gauges could be arranged on the
sensor band of the SONAR-based gas volume fraction sensing
technology (e.g. the known GVF-100 meter) in a Wheatstone bridge
configuration to maximize strain sensitivity and minimize
temperature effects. In this case, the sensitivity assuming a
strain gauge factor of 2, the sensitivity is approximately 13
.mu.V/.mu..epsilon., where V is volts. Assuming a 4-inch schedule
40 carbon steel pipe, a one psi change in pressure would cause a 4
.mu.V change in Wheatstone bridge output. This sensitivity would
increase for larger diameter pipes which generally have a smaller
t/R.
[0152] The integrated pressure gauge could be calibrated in-situ
for best accuracy, but it may be sufficient to normalize the
pressure output to a certain know state then use the tangential
strain formula above with know pipe parameters to calculate the
pressure from the measured strain.
[0153] The SONAR-based entrained air meter and metering technology
are known in the art and may take the form of a SONAR-based meter
disclosed, e.g., in whole or in part in U.S. Pat. Nos. 7,165,464;
7,134,320; 7,363,800; 7,367,240; and 7,343,820, all of which are
incorporated by reference in their entirety. The SONAR-based
entrained air meter and metering technology is capable of providing
a variety of information, including the pure phase density and pure
phase liquid sound speed is known, such that the GVF can be
determined by measuring the speed of sound and then applying the
Woods Equation.
[0154] Determining the GVF by measuring the speed of sound can
provide fast an accurate data. Also the SOS measurement system can
be very flexible and can easily be configured to work with
different concrete containers and sample particular volumes.
[0155] Consistent with that described above, the SONAR-based
entrained air meter and metering technology are known in the art
and may take the form of a SONAR-based meter disclosed, e.g., in
whole or in part in U.S. Pat. Nos. 7,165,464; 7,134,320; 7,363,800;
7,367,240; and 7,343,820.
Other Known Technology
[0156] The acoustic transmitter, the acoustic receiver or receiver
probe and/or transponders are devices that are known in the art,
and the scope of the invention is not intended to be limited to any
particular type or kind either now known or later developed in the
future.
The Scope of the Invention
[0157] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, may modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed herein as the best mode
contemplated for carrying out this invention.
* * * * *