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Claims  |
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What is claimed:
1. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function; and
display means for displaying more than one of the following: said input
vibration signals, said transfer function and said output vibration
signals.
2. Vibration cancellation and monitoring system according to claim 1,
wherein:
said input means includes first means for generating an input signal
waveform from said sensed vibration signals and second means for
generating an input spectral waveform from said input signal waveform;
said transfer means derives a transfer function from said input spectral
waveform and generates an output spectral waveform;
said output means generates a vibration cancellation actuator signal from
said output spectral waveform; and
said display means displays at least one of the following: said input
signal waveform, said input spectral waveform, said transfer function,
said vibration cancellation actuator signal and said output spectral
waveform.
3. Vibration cancellation and monitoring system according to claim 2,
wherein said input and output means each include a peak detector means for
determining a peak of a respective input and output vibration signal and
said display means displays input and output peaks.
4. Vibration cancellation and monitoring system according to claim 3,
wherein said input means includes self-adjusting input gain means and said
display means displays input gain.
5. Vibration cancellation and monitoring system according to claim 2,
wherein said transfer means includes means for generating a transfer
function spectral waveform and means for determining average magnitude of
said transfer function, and said display means displays said transfer
function spectral waveform and said average magnitude.
6. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
input peak detector means for determining a peak of said input vibration
signal;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
output peak detector means for determining a peak of said output vibration
signal;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function; and
display means for displaying more than one of the following: said input
vibration signals, said input peak, said transfer function, said output
vibration signals and said output peak.
7. Vibration cancellation and monitoring system according to claim 6,
wherein said input means includes self-adjusting input gain means and said
display means displays input gain.
8. Vibration cancellation and monitoring system according to claim 6,
wherein said transfer means includes means for setting maximum output
signal and minimum input signal, and said display means displays said set
maximum output signal and set minimum input signal.
9. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function;
means for generating a transfer function spectral waveform;
means for determining average magnitude of said transfer function; and
display means for displaying more than one of the following: said input
vibration signals, said transfer function, said transfer function spectral
waveform, said transfer function average magnitude, and said output
vibration signals.
10. Vibration cancellation and monitoring system according to claim 9,
wherein said transfer means includes means for setting highest and lowest
frequencies of input signals to be processed, and said display means
displays said set highest and lowest frequencies.
11. Vibration cancellation and monitoring system according to claim 9,
wherein said display means includes means for setting the zero reference
level for spectral waveform display and displays said zero reference
level.
12. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function;
sync means for receiving a synchronization signal;
rate detector means for detecting a sample rate from said synchronization
signal;
period detector means for detecting a sample period from said
synchronization signal; and
display means for displaying more than one of the following: said input
vibration signals, said transfer function, said output vibration signals,
said sample rate and said sample period.
13. Vibration cancellation and monitoring system according to claim 12,
including means for determining the revolutions per minute of said
synchronization signal and said display means displays revolution per
minute of said synchronization signal.
14. Vibration cancellation and monitoring system according to claim 13,
wherein said transfer means includes enabling means for enabling said
transfer means at synchronization signals above a minimum revolutions per
minute, means for selecting said minimum revolutions per minute and said
display means displays said selected minimum revolutions per minute.
15. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function;
conversion means for converting input vibration signals, transfer function
and output vibration signals from vibration cancellation format to display
format; and
display means for displaying more than one of the following: said input
vibration signals, said transfer function and said output vibration
signals.
16. Vibration cancellation and monitoring system according to claim 15,
wherein said display means is in a common housing with said input means,
output means and transfer means.
17. Vibration cancellation and monitoring system according to claim 15,
wherein said display means is separate from a housing common to said input
means, output means and transfer means and is connected thereto by a
communication link.
18. Vibration cancellation and monitoring system according to claim 1,
wherein said transfer means includes parameter means for defining
operating parameters of said transfer means, and keyboard means for
entering operating parameters into said parameter means and said display
means displaying said operating parameters.
19. Vibration cancellation and monitoring system according to claim 18,
including test means for generating a test signal to test response of said
vibration cancellation system.
20. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function;
display means for displaying at least one of the following: said input
vibration signals, said transfer function and said output vibration
signals; and
test means for producing an output pulse, determining the frequency at
which maximum input occurs in response to said output pulse and providing
a single tone output pulse at said frequency.
21. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function;
display means for displaying at least one of the following: said input
vibration signals, said transfer function and said output vibration
signals;
means for setting the lowest frequency of input signals to be processed by
said transfer means; and
test means for producing a single tone output signal at said set lowest
frequency.
22. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibration
signals from said input means and generating output vibration signals for
said output means as a function of said transfer function;
display means for displaying at least one of the following: said input
vibration signals, said transfer function and said output vibration
signals; and
test means for producing a variable harmonic pulsating output signal.
23. Vibration cancellation and monitoring system comprising:
input means for receiving sensed vibration signals from vibration sensors
and generating input vibration signals;
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator;
transfer means for deriving a transfer function from said input vibrations
signals from said input means and generating output vibrations signals for
said output means as a function of said transfer function;
display means for displaying at least one of the following: said input
vibration signals, said transfer function and said output vibration
signals; and
test means for providing said input vibration signals to said output means
bypassing said transfer means.
24. Vibration cancellation and monitoring system according to claim 1,
including test means for disabling said output means.
25. Monitoring and testing system for a separate vibration cancellation
system having first input means for receiving sensed vibration signals
from vibration sensors and generating input vibration signals; first
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator; and
transfer means for generating output vibration signals for said output
means as a function of a transfer function; said monitoring and testing
system includes:
second input means to be connected to said first input means;
second output means to be connected to said first output means;
testing means for providing a test actuator signal to said second output
means; and
display means for displaying input vibration signals from said second input
means.
26. A monitoring and testing system according to claim 25, wherein said
testing means includes first testing means for producing an output pulse,
determining the frequency at which maximum input occurs in response to
said output pulse and providing a single tone output pulse at said
frequency.
27. A monitoring, and testing system according to claim 25, including means
for setting the lowest frequency of input signals to be processed by said
transfer means and said testing means includes second test means for
producing a single tone output signal at said set lowest frequency.
28. A monitoring, and testing system according to claim 25, wherein said
testing means includes a third test means for producing a variable
harmonic pulsating output signal.
29. A monitoring, and testing system according to claim 25, wherein said
testing means includes a fourth test means for providing said input
vibration signals to said second output means.
30. A monitoring, and testing system according to claim 25, wherein said
testing means includes fifth test means for disabling said second output
means.
31. A monitoring, and testing system according to claim 25, including first
spectral means for generating an input spectral waveform from signals at
said second input means; and wherein said display means displays said
input spectral waveform.
32. A monitoring, and testing system according to claim 31, including
output spectral means for generating spectral waveforms from signals of
said second output means; and wherein said display means displays
vibration cancellation actuator signals and output spectral waveforms.
33. A monitoring, and testing system according to claim 32, including means
for determining a transfer function from signals at said second input and
output means; and wherein said display means displays said transfer
function.
34. A vibration cancellation monitoring system for a vibration cancellation
system having first input means for receiving sensed vibration signals
from vibration sensors and generating input vibration signals; first
output means for receiving output vibration signals and generating a
vibration cancellation actuator signal for a vibration actuator; and
transfer means for generating output vibration signals for said first
output means as a function of a transfer function; said monitoring system
comprising:
second input means to be connected to said first input means;
third input means to be connected to said first output means;
first spectral means for generating an input spectral waveform from signals
at said second input means;
second spectral means for generating an output spectral waveform from
signals at said third input means; and
display means for displaying signals at said second and third input means
and input and output spectral waveforms.
35. A vibration cancellation monitoring system according to claim 34,
including means for determining a transfer function from signals at said
second and third input means; and wherein said display means displays said
transfer function. |
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Claims |
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Description |
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BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates generally to vibration cancellation and more
specifically to monitoring and testing and operator controlling of
vibration cancellation systems.
Primary vibrations in gas liquid or solids have been cancelled or
nullified, at least in part, with specially generated cancelling or
secondary vibrations. For example, the prior art device shown U.S. Pat.
No. 4,490,841 to Chaplin et al., specifically shows a method and apparatus
for cancelling vibrations wherein a vibration sensor is connected through
an input circuit and fourier transformer to a processor which produces an
output through a fourier transformer and output circuit to a vibration
actuator. A synchronous input is also provided to the processor from the
vibration source. Although no adjustment, testing or monitoring is
described in the aforementioned patent, a minimum amount of adjustment is
available and includes generally the frequency bandwidth of the
frequencies which the system is capable of handling, the gain of the
amplifiers, and other types of adjustments. The only measure of the
inability of the system to handle the particular environment is that the
vibrations have not been effectively cancelled.
An automatic digital audio processor (ADAP) has been produced by Rockwell
International, and is specifically described in an article by James E.
Paul, "Adaptive Digital Techniques for Audio and Noise Cancellation", IEEE
Circuits and Systems Magazine, Volume 1, No. 4, pp. 2-7. The ADAP
specifically displays the convergence time, the sample time, the filter
order and the input delay. These parameters, as well as bandwidth may be
adjusted on this system. Neither an integral testor nor the display of
many of the signals within the circuitry are provided in this article.
The prior art has failed to take advantage of the signals available within
the electronics to provide monitoring of the operation of the circuitry as
well as an indication of the operation of system in which the vibrations
are being cancelled. If one can monitor these signals, they can determine
whether the vibrations produced are normal, or if the vibrations indicate
a serious failure of the system.
Thus, it is an object of the present invention to provide a monitoring
system for a vibration cancellation system.
Another object of the present invention is to provide the capability to
determine whether the systems whose vibrations are to be cancelled is
operating in a safe range.
A further object of the present invention is to provide a monitoring system
and display which may be integral with or separate from a vibration
cancellation system.
A still further object of the present invention is to provide a display and
input device for varying the operating parameters of the vibration
cancellation system.
A still even further object of the present invention is to provide an
integral testor for vibration cancellation systems which test the
individual elements of the circuitry as well as their response.
These and other objects are obtained by providing a display for displaying
one or more of the following: the input vibration signal received from the
vibration system; the transfer function of the cancellation system; and
the output vibration cancellation signal. The input circuit generates an
input waveform from the input signals and provides an input spectral
waveform to the transfer function generator. The transfer function
generator provides an output spectral waveform which is converted by the
output circuitry to a vibration cancellation actuator signal. The display
displays the input signal waveform, the input spectral waveform, the
transfer function, the output spectral waveform and the vibration
cancellation actuator signal. The input and output circuits each include a
peak detector and the display displays the peak of the respective input
and output signals. The gain of the input circuit is self-adjusting and
the display also displays the input gain. The average magnitude of the
transfer function and the spectral waveform of the transfer function are
also displayed.
Circuitry is also provided for the synchronization signal received by the
vibration cancellation system to determine certain parameters and display
them. A rate detector and period detector respectively detect a sample
rate and sample period from the synchronization signal. The display
displays the detected sample rate and sample period.
In the embodiment wherein the monitoring and display system is separate and
distinct from the vibration cancellation system, the monitoring and
display system receives the input and output vibration signals and the
synchronization signals from the vibration cancellation system. In
addition to displaying the input vibration signal and the output vibration
cancellation signal, the monitoring and display system would also
calculate the transfer function of the cancellation system as well as
deriving the appropriate input and output spectral displays. Similarly,
the synchronization data would also be determined within the monitoring
and display system. It should also be noted that the operator control of
the parameters of the vibration cancellation system and the test would not
be included in the monitoring display system which is not integral with
the vibration control system. In the case of the stand-alone monitor it
should be noted that the tester may be part of the stand-alone monitor and
the only element not provided is the display of operator controllable
inputs and parameters.
An input device is provided for setting a maximum output signal level and
minimum input signal thresholds and the display displays these values. The
input device may also input the highest and lowest frequency or bandwidth
of the signals to be processed and the display displays these two values.
The zero reference value for the spectral waveform for the display may
also be set and displayed. The system receives synchronization signals and
displays a sample rate and revolutions per minute of the synchronization
signal. The input device may provide input for the minimum revolutions per
minute for which the transfer function will operate which is also
displayed. Circuitry is provided to convert the input vibration signal,
transfer function and output vibration signals from vibration cancellation
format to display format. The display may be in a common housing with the
input, output and transfer circuitry or may be separate therefrom and
connected by a communication link.
The testing circuitry integral with the vibration cancellation and monitor
system includes five testing modes. The first testing mode produces an
output pulse and determines the frequency at which the maximum input
occurs in response to the output pulse and then provides a single tone
output pulse at that frequency. The second mode produces a single tone
output signal at the frequency of the lowest frequency of the input signal
which is preset. The third mode produces a variable harmonic pulsating
output signal. The fourth mode delivers the input signal to the output
circuitry bypassing the transfer circuit. The fifth testing mode disables
the output circuitry. During all the test modes, the input signals and
spectrum are displayed.
It should be noted that throughout the specification and claims the use of
the word "circuitry" is considered generic, and are defined so as to
include not only electronic elements to perform the functions described,
but also processors with software capable of performing these functions.
For example, the functions of the input, transfer and output circuitry
could all be performed in software. Thus, the term "circuitry" is not to
be considered limiting.
Other objects, advantages and novel features of the present invention will
become apparent from the following detailed description of the invention
when considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of a vibration cancellation system of
the prior art.
FIG. 2 is a schematic block diagram of a vibration cancellation and
monitoring system according to the principles of the present invention.
FIG. 3 is an illustration of a display of input and output information.
FIG. 4 is an illustration of a display of group information.
FIG. 5 is an illustration of a display of channel parameters.
FIG. 6 is an illustration of a display of spectral information.
FIG. 7 is a flow diagram of the test modes to be used with the vibration
cancellation and monitoring system of FIG. 2.
FIG. 8 is a schematic block diagram showing a vibration cancellation
monitoring system not integral with vibration cancellation system
constructed according to a preferred embodiment of the principal present
invention.
DETAILED DESCRIPTION OF THE DRAWINGS
A vibration cancellation system 25 is illustrated in FIG. 1 including a
microphone or vibration sensor 11 to sense the primary vibration P from
vibration source 10 and a speaker or vibration actuator 12 which is
actuated by the vibration cancellation system 25 to produce a secondary
vibration S which interacts with the primary vibration P in the location
of the vibration sensor 11.
The vibration cancellation system 25 includes an input circuit 13 connected
to the vibration sensor 11 to receive signals therefrom and produce on
line 14 an analog input waveform. A fourier transformer 15 receives the
analog input signals 14 and provides a spectral waveform of the input
sensed vibration on a plurality of outputs 16 to a processor 17. The
processor 17, besides receiving the spectral vibration input signals on
line 16, also receives a synchronization input from a synchronization
source 18 which monitors the cycle of the vibration source 10. The
processor 17, being a transfer means having a transfer function, receives
a frequency domain components with respect to time from the fourier
transformer 15, multiplies it by a multiplying coefficient, and produces a
frequency domain coefficient on outputs 19.
The fourier transformer 20, being part of the output circuitry, receives
the spectral waveform over outputs 19 from the processor 17 and produces
an analog output signal 21 to the output drive circuit 22 which provides a
cancellation signal to the actuator 12.
The details of the circuitry, their operations and examples of the transfer
functions are described in the previously mentioned U.S. Pat. No.
4,490,841. To this extent, this patent is incorporated herein by
reference. Although this patent is the vibration cancellation system used
in the present example, the monitoring and testing system of the present
application may be used with other vibration cancellation systems. For
example, it may be used with other Chaplin et al. systems described in
U.S. Pat. Nos. 4,153,815; 4,417,098; and 4,566,118, as well as systems
described in U.S. Pat. Nos.4,677,676 and 4,627,677.
The modification of the circuit of FIG. 1 to provide the appropriate
monitoring of the vibration cancellation system is illustrated in FIG. 2.
The vibration cancellation system 25 is shown having the sensors 11 and
actuator 12 and the synchronization source 18 connected thereto. The
vibration cancellation data is illustrated in the first column as
including input waveform which are available on lines 14 or 9 of FIG. 1,
the input spectral waveform available on line 16, the transfer function
available from processor 17 and given the number 17a, the output spectrum
or spectral waveform available on line 19, and the output waveform
available on lines 21 or 23 at the input or output of the output circuit.
Thus, the information is available in the prior art vibration cancellation
system and need only to be processed further to provide an appropriate
display. Where the monitoring and display system are not to be integral
with the vibration cancellation system illustrated in FIG. 8, as well as
in cases in which the vibration cancellation system does not calculate or
provide the appropriate information, the monitoring and display system
would have the ability to calculate and determine the appropriate
information displayed. For example, the monitoring and display system
would be connected to lines 9, 23 and the output from the synchronous
input 18 so as to receive the same input and output signals of the
vibration cancellation system. It would include the capability of taking
these input and output signals and deriving the signal level data as well
as converting both to spectral display information. From the input and
output spectral display, the system could calculate the transfer function
and appropriately display it. Thus, the same information can be provided
as if the monitoring and display system were part of the vibration
cancellation system, but would require additional circuitry or software.
Information with respect to the synchronization signal to be described
hereafter are also determined and provided in the display of the separate
monitoring and display system. Also appropriate test signals can be
provided by the stand-alone system.
The second column represents the vibration cancellation monitoring
processors 30. This includes a level detector 31 and 35 for receiving the
analog input waveforms on 14/9 and the output waveform on 21/23. A
spectrum processor 32, 33 and 34 are for receiving respectively the input
spectrum on 16, the transfer function on 17a and the output spectrum on 19
to provide an appropriate component of display. The vibration cancellation
monitoring processors 30 produce the vibration cancellation monitor data
40 represented by the third column. This monitor data includes an input
level display data 41 connected to level detector 31, an input spectrum
display data 42 connected to the spectrum processor 32, a transfer
function spectrum display data 43a and transfer function spectrum average
magnitude display data 43b connected to spectrum processor 33, output
spectrum display data 44 connected to spectrum display 34, and output
level display data 45 connected to level detector 35. The output of the
vibration cancellation monitored data are all connected to one or more
display devices 50.
When a synchronous source 18 is used with vibration cancellation system 25,
additional vibration cancellation monitor processors 30 and vibration
cancellation monitor data 40 are provided. A rate detector 36 receives a
synchronization signal and provides a sample rate display data 46. A
period detector 37 also receives synchronization signal and provides as
monitored data, the sample period display data 47a, the frequency unit
display data 47b and the RPM display data 47c.
A group of control parameters 28 for the vibration cancellation system 25
may be controlled or selected by an operator input device 27. The control
parameters which are provided to the vibration cancellation system 25
include the number of samples to be averaged 28a, the RPM multiplier 28b,
the frequency limits 28c, the maximum output level 28d, the minimum input
level 28e and the start RPM value 28f. A control parameter is provided to
the display to control the display and includes a reference level 28g.
The number of samples to be averaged 28a is the number of cycles being
averaged per sample. Although preferably, the system is designed to
average two cycles per sample, this can be doubled up to 128 cycles per
sample. The figure should be kept lower for maximum sensitivity. Each
doubling will reduce the unsynchronized background noise by an additional
six dB and will also increase the system's reaction time to changes in
noise levels.
The RPM multiplier 28b, is the number of cycles of revolution that
represents a single noise cycle. For example, in a four cycle engine, the
noise cycle is every two cycles of revolution. The frequency limit 28c is
the bandwidth. This sets an f-high and an f-low representing the highest
and lowest frequencies which the system will process. Maximum output 28d
and minimum input 28e set the levels of the input and output circuitry.
The start RPM 28f is the lowest RPM rate at which the vibration
cancellation system 25 will operate. No cancellation will begin until the
RPM increases above the start RPM rate and cancellation will stop when the
RPM falls below this rate. This feature eliminates cancellation during
unwanted start-up and shut-down periods.
The reference level 28g is the zero dB reference level for the noise
spectrum graph. If the noise level causes the graph to go off the scale,
the setting should be increased. It should be noted that this affects the
display only and not the processing of the signals.
A typical example of the input and output information display is
illustrated in FIG. 3. This provides a summary of the operation of each
channel. The gain of the input channel is indicated in dBs and is set
automatically by the vibration system 25. The input peak is the peak input
level in dBs and the peak output is the peak output level produced by the
vibration control system 25. The response ratio is the voltage change in
the residual noise corresponding to one volt change by the vibration
control system. This measures how well the environment is responding to
changes made by the vibration control system. If the response ratio
displayed is less than 0.5, there is amplification missing somewhere in
the system and if this displayed ratio is over 15.0, there is
overamplification in the system. The letter by the channel number could
indicate the mode in which the system is operating, for example, normal,
manual or test. The "L" indicates the input signal is too low for
processing. This is normal when full quiet or cancellation has been
achieved. If an H appears to the right of the peak number, it would
indicate that the input signal is too high and is also not being
processed.
Another display is illustrated in FIG. 4 is group information display. The
input or output channels may be provided in appropriate groups including
one or two channels and each group reflects the effects of the
synchronization signal on the related group. As illustrated, the group
display of FIG. 4 includes sample time, sample rate, frequency unit, RPM
multiplier, RPM, and start RPM. All these are defined above.
The channel parameter display is illustrated in FIG. 5. This includes the
channel number, mode of operation illustrated as "manual", number of
cycles being averaged each cycle, high and low frequency to be processed,
maximum output and minimum input, test type and display reference level.
It should be noted that test type will be discussed more fully below.
An example of a spectrum display of a spectorial waveform is illustrated in
FIG. 3. The selected frequencies of the display are listed in the first
column on the left with the center frequency being listed in the last
column on the right. For each frequency, the amplitude of that frequency
within the input and output signals are listed. In the next three columns
the magnitude, phase and coherence of the transfer function is provided.
Preferably, the vibration cancellation monitor processors 30, vibration
cancellation monitoring data 40 and display devices 50 are integral with
and contained in a single housing with the vibration cancellation system
25. Alternatively, the vibration cancellation monitor processors 30,
vibration cancellation monitor data 40 and display device 50 may be
connected to the vibration cancellation data and the vibration
cancellation system 25 by communication link which may be hardwire or by a
non-hardwire communication link. Similarly, the connection between the
vibration cancellation monitor processor/vibration cancellation monitor
data and the display devices 50 may be by communication link.
The vibration cancellation system testing circuit is illustrated in FIG. 7
by a software flow diagram performed by processor 17.
The five tests to be performed are as follows. Test 1 produces a pulse
through the actuators 12 and the vibration cancellation system 25
determines the frequency at which the maximum input occurs. The vibration
cancellation system 25 then produces a single tone at that frequency. If a
tone is not heard using a speaker, or a vibration not felt when using a
mechanical actuator, the gain setting of the power amplifiers in the
output circuit 22 are adjusted. The input levels and spectrum are
displayed.
The second test tests the output circuitry and produces an output signal of
a single tone at the displayed low frequency. The input levels and
spectrum are displayed. This second test tests for harmonic distortion.
When the single tone is produced, a single tone should be detected by the
input circuit. Thus, a plurality of output tones indicates the presence of
harmonic distortion, generally in the speakers, or the vibration actuator.
A third test produces a variable harmonic pulsating output signal similar,
for example, to the noise produced by a helicopter. This tests the system
for a high noise environment with multiple harmonics. The input levels and
spectrum are displayed.
The fourth test is a loop-back test wherein the signal applied to the
channel input is bypassed unprocessed to the channel output. This bypasses
the processor 17 by interconnecting fourier transformers 15 and 20. The
input level and spectrum are displayed.
The fifth test produces no output and merely provides a display of the
values of the signal present at the input sensor, which is an indication
of the noisy environment before cancellation.
Whereas tests 1-4 are performed without a noisy environment, and thus are a
test of the system, the fifth test is usually performed in the noisy
environment.
The present system provides a way of monitoring failure of the system which
produces the vibration. For example, the fifth test will allow monitoring
of the input signal to determine whether it has increased abnormally when
cancellation is not in effect. Also, the cancellation output signal can be
monitored to determine whether it has increased abnormally. A further
indication of failure would be an abnormal change in the RPMs received
from the synchronization signal source. Abnormal change in the input and
output spectrums, as well as the transfer function, are indications of a
defective system. The determination of abnormality can be from historical
records of the environment or system to be monitored, or from knowledge of
the proper functioning of the equipment being monitored. Similarly, the
processor 17 can be provided with a sufficient memory storage to provide
its own historical data with certain limi | | |
