U.S. patent application number 15/784345 was filed with the patent office on 2018-06-07 for reducing or eliminating transducer reverberation.
This patent application is currently assigned to SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. The applicant listed for this patent is SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC. Invention is credited to Marek HUSTAVA, Jiri KUTEJ, Michal NAVRATIL, Tomas SUCHY.
Application Number | 20180160226 15/784345 |
Document ID | / |
Family ID | 61525772 |
Filed Date | 2018-06-07 |
United States Patent
Application |
20180160226 |
Kind Code |
A1 |
HUSTAVA; Marek ; et
al. |
June 7, 2018 |
REDUCING OR ELIMINATING TRANSDUCER REVERBERATION
Abstract
An obstacle monitoring system includes a transducer that
receives an ultrasonic echo from an obstacle and generates a signal
based on the echo. The system further includes a controller coupled
to the transducer that is calibrated based on a frequency response
of the transducer and a coupling circuit. The system further
includes circuitry generating a damping current, controlled by the
controller, that reduces or eliminates reverberation of the
transducer.
Inventors: |
HUSTAVA; Marek; (Bratislava,
SK) ; SUCHY; Tomas; (Brno, CZ) ; NAVRATIL;
Michal; (Pustimer, CZ) ; KUTEJ; Jiri; (Brno,
CZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEMICONDUCTOR COMPONENTS INDUSTRIES, LLC |
Phoenix |
AZ |
US |
|
|
Assignee: |
SEMICONDUCTOR COMPONENTS
INDUSTRIES, LLC
Phoenix
AZ
|
Family ID: |
61525772 |
Appl. No.: |
15/784345 |
Filed: |
October 16, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62430171 |
Dec 5, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G10K 11/178 20130101;
H04R 3/002 20130101; G01S 7/523 20130101; G01S 2015/932 20130101;
G01S 7/52004 20130101; G01S 7/52 20130101; G01S 15/93 20130101;
G08G 1/165 20130101; G01S 15/931 20130101 |
International
Class: |
H04R 3/00 20060101
H04R003/00; G10K 11/178 20060101 G10K011/178; G01S 15/93 20060101
G01S015/93; G08G 1/16 20060101 G08G001/16 |
Claims
1. An obstacle monitoring system comprising: a transducer that
receives an ultrasonic echo from an obstacle and generates a signal
based on the echo; a controller coupled to the transducer that is
calibrated based on a response of the transducer and a coupling
circuit; and circuitry generating a damping current, controlled by
the controller, that reduces or eliminates reverberation of the
transducer.
2. The system of claim 1, wherein the controller is selected from
the group consisting of: damping digital filter, analog filter,
correlator, integrator, and derivator.
3. The system of claim 1, wherein the controller is recalibrated
upon ambient temperature changes.
4. The system of claim 1, wherein the controller is recalibrated
upon changes in the transducer or transducer characteristics.
5. The system of claim 1, wherein the obstacle is monitored up to
at least five centimeters from the transducer.
6. The system of claim 1, wherein the transducer comprises a
two-pin piezo when used with a transformer or without a
transformer.
7. The system of claim 1, further comprising an automobile on which
the transducer is located.
8. The system of claim 1, wherein the transducer is located on a
bumper of the automobile.
9. An obstacle monitoring method comprising: receiving an
ultrasonic echo from an obstacle; generating a signal based on the
echo; calibrating a circuit by selecting coefficients for a filter
based on a response to the signal; and reducing or eliminating
reverberation by introducing a damping current controlled by a
controller.
10. The method of claim 9, wherein the controller is selected from
the group consisting of: damping digital filter, analog filter,
correlator, integrator, and derivator.
11. The method of claim 9, wherein the filter is a digital damping
finite impulse response ("FIR") filter.
12. The method of claim 9, further comprising predicting a time
when the magnitude of reverberation falls under a threshold and
interpreting a signal, received after the predicted time with a
magnitude above the threshold, as another echo and not as a
continuation of reverberation.
13. The method of claim 9, wherein calibrating the circuit further
comprises measuring a resonance frequency and modifying the
coefficients for the filter based on the resonance frequency.
14. The method of claim 9, wherein calibrating the circuit further
comprises measuring a junction or sensor temperature and modifying
the coefficients for the filter based on the junction or sensor
temperature.
15. The method of claim 9, wherein calibrating the circuit further
comprises measuring transmission power of a transmission (piezo
voltage) that causes the echo and modifying the coefficients for
the filter based on the transmission power (piezo voltage).
16. The method of claim 9, further comprising determining a
distance from a transducer receiving the echo to the obstacle.
17. The method of claim 16, further comprising generating an alert
if the distance is below a threshold.
18. The method of claim 16, further comprising performing a
corrective action if the distance is below a threshold.
19. The method of claim 18, wherein the corrective action is
applying a braking force to an automobile on which the transducer
is located.
20. An obstacle monitoring system comprising: a transducer that
receives an ultrasonic echo from an obstacle and generates a signal
based on the echo; and a controller that drives the transducer in a
first mode or a second mode; wherein the first mode comprises
driving the transducer at a resonance frequency for relatively
longer distances between the transducer and the obstacle; and
wherein the second mode comprises driving the transducer at an
out-of-resonance frequency, lower or higher than the resonance
frequency, for relatively shorter distances between the transducer
and the obstacle to reduce or eliminate reverberation of the
transducer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/430,171, titled "Distance Measurement Using
Ultrasonic Park Assist Sensors" and filed Dec. 5, 2016.
BACKGROUND
[0002] The core concept of ultrasound distance detection is to
transmit an ultrasound pulse at an obstacle and measure how soon
echoes from the obstacle are received in order to determine the
distance to the obstacle. Specifically, the time between
transmission of the pulse and reception of the echo is linearly
proportional to the distance to the obstacle. However, ringing
prevents using the same transducer as both a transmitter and
receiver until the ringing has subsided to the point that the
received waves exceed the magnitude of the waves being emitted.
Such transducers effectively cannot sense a reflection from an
obstacle closer than some particular distance from the transducer
depending on the amount of ringing. Thus, when it is necessary to
sense the presence of an obstacle closer than the particular
distance, ultrasonic systems heretofore have required that pairs of
transducers be used, one transducer for sending and another for
receiving. The requirement to use pairs of transducers increases
the cost, complexity, and size of the system.
SUMMARY
[0003] Accordingly, systems and methods for reducing or eliminating
transducer reverberation are disclosed herein. An obstacle
monitoring system includes a transducer that receives an ultrasonic
echo from an obstacle and generates a signal based on the echo. The
system further includes a damping digital filter coupled to the
transducer that is calibrated based on a frequency response of the
transducer and a coupling circuit. The system further includes
circuitry generating a damping current, controlled by the damping
digital filter, that reduces or eliminates reverberation of the
transducer.
[0004] An obstacle monitoring method includes receiving an
ultrasonic echo from an obstacle, and generating a signal based on
the echo. The method further includes calibrating a circuit by
selecting coefficients for a digital damping finite impulse
response ("FIR") filter based on a frequency response to the
signal. The method further includes reducing or eliminating
reverberation by introducing the damping current controlled by
digital damping filter.
[0005] An obstacle monitoring system includes a transducer that
receives an ultrasonic echo from an obstacle and generates a signal
based on the echo. The system further includes a controller that
drives the transducer in a first mode or a second mode. The first
mode includes driving the transducer at a resonance frequency for
relatively longer distances between the transducer and the
obstacle. The second mode includes driving the transducer at an
out-of-resonance frequency, higher than the resonance frequency,
for relatively shorter distances between the transducer and the
obstacle to reduce or eliminate reverberation of the
transducer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Systems and methods for reducing or eliminating transducer
reverberation are disclosed herein. In the drawings:
[0007] FIG. 1 is a diagram illustrating a transducer sending a
pulse toward an obstacle and receiving an echo from the
obstacle;
[0008] FIG. 2 is a chart illustrating pulse transmission,
reverberation, and echo detection;
[0009] FIG. 3 is a circuit diagram illustrating damping
circuitry;
[0010] FIG. 4 is another circuit diagram illustrating damping
circuitry; and
[0011] FIG. 5 is a flow diagram illustrating a method for reducing
or eliminating transducer reverberation.
[0012] It should be understood, however, that the specific
embodiments given in the drawings and detailed description thereto
do not limit the disclosure. On the contrary, they provide the
foundation for one of ordinary skill to discern the alternative
forms, equivalents, and modifications that are encompassed together
with one or more of the given embodiments in the scope of the
appended claims.
NOTATION AND NOMENCLATURE
[0013] Certain terms are used throughout the following description
and claims to refer to particular system components and
configurations. As one of ordinary skill will appreciate, companies
may refer to a component by different names. This document does not
intend to distinguish between components that differ in name but
not function. In the following discussion and in the claims, the
terms "including" and "comprising" are used in an open-ended
fashion, and thus should be interpreted to mean "including, but not
limited to . . . ". Also, the term "couple" or "couples" is
intended to mean either an indirect or a direct electrical or
physical connection. Thus, if a first device couples to a second
device, that connection may be through a direct electrical
connection, through an indirect electrical connection via other
devices and connections, through a direct physical connection, or
through an indirect physical connection via other devices and
connections in various embodiments.
DETAILED DESCRIPTION
[0014] For clarity, the examples used herein discuss parking-assist
systems, however the concepts of this disclosure may be applied to
any type of obstacle monitoring that prioritizes rapid response.
Due to the resonant nature of transducers, reverberations of
transducer membranes occur during transmission and shortly
thereafter. The reverberations effectively result in a dead time
during which it is not possible to detect echoes, and hence detect
the obstacle. As such, the dead time is equivalent to a minimum
detection distance for the sensor. By reducing or eliminating the
reverberations and dead time, the minimum detection distance for
the sensor is also reduced or eliminated. Accordingly, close and/or
fast-moving obstacles, previously undetectable or detectable
without enough time to perform corrective actions or generate
alerts, may be detected with enough time to perform corrective
actions or generate alerts. Specifically, fast damping may be
performed using a digital filter to sense transducer voltage, apply
a finite impulse response ("FIR") filter, and control a damping
current that reduces or eliminates reverberations. For example,
frequency-dependent admittance may be placed in parallel with the
transducer, with a transformer present or not present, to create a
high damping resistance as illustrated in the Figures and described
below. A common obstacle-monitoring scenario is illustrated in FIG.
1.
[0015] FIG. 1 is a diagram of an illustrative obstacle monitoring
system 100 including a transducer 102 sending a pulse 108 toward an
obstacle 106 and receiving an echo 104. The distance between the
transducer 102 and the obstacle 106 is determined by measuring the
time between transmission of the pulse 108 and reception of the
echo 104 and multiplying that time by the speed of sound in air. In
various embodiments, the speed of sound in another material is
used.
[0016] The system 100 also includes a pulse generator 112 and
transmit driver 110 coupled to the transducer 102. The generator
112 may generate an up-chirp, a down-chirp, or a variable-chirp of
custom bandwidth, duration, and center frequency as desired. The
generator 112 may adjust the pulses 108 to be sent by the
transducer 102 based on feedback from previous measurements. For
example, the pulses 108 may be adjusted based on minimum detection
distance (with increased pulse duration, minimum distance is
decreased); signal-to-noise ratio and maximum detection distance
(with increased pulse duration, signal-to-noise ratio and maximum
detection distance are increased); reliability of channel
separation (with increased pulse duration, channel separation is
improved); time-of-flight accuracy and resolution (a wider
bandwidth results in improved accuracy and resolution); transducer
bandwidth; and the like. The generator 112 supplies the generated
pulse to the transmit driver 110, which transforms the pulse into
an appropriate signal for the transducer 102 to transmit.
Specifically, the transmit driver 110 embeds the pulse within an
appropriate carrier to transmit the pulse over the channel. The
transmit driver 110 supplies the signal to the transducer 102,
which transmits the pulse 108 toward the obstacle and receives the
echo 104.
[0017] The system 100 also includes an amplifier 114 and a
controller, which are configured to amplify useful signal
components from the echo 104 and control a damping current that
reduces or eliminates reverberation of the transducer 102,
respectively. The controller may be a damping digital filter,
analog filter, correlator, integrator, or derivator in various
embodiments. For clarity, the example of a digital damping filter
116 is used herein. The system 100 also includes a correlator 118.
The correlator 118 is configured to determine the time at which the
correlation between the pulse 108 and echo 104 is highest. By
designating such time as the reception time of the echo 104, the
time-of-flight of the pulse 108 and echo 104 may be determined by
differencing the transmit time and reception time. Accordingly, the
distance to the obstacle 106 may be determined by multiplying the
speed of sound and the time-of-flight. Data from the echo 104 is
provided as feedback to the frequency pulse generator 112, which
may make adjustments to future pulses based on the data. Without
the damping digital filer 116, reverberation interferes with echo
detection as illustrated in FIG. 2.
[0018] FIG. 2 is a chart 200 of an illustrative transmission (TX),
reverberation, and echo magnitude at the transducer as a function
of time. Starting from earliest time, the leftmost peak in
magnitude illustrates transmission of the pulse toward the
obstacle. The next peak illustrates the reverberation caused by the
pulse transmission. As can be seen, the reverberation has a higher
magnitude than an echo detection threshold, represented by the
horizontal line, for a substantial length of time (even longer than
the transmission). Echoes may be detected only when the
reverberation magnitude is under the echo detection threshold. The
third peak illustrates an echo received at the transducer. Should
such an echo be received during the time the reverberation exceeds
the threshold, then the echo would not be detected or correctly
interpreted as an echo. As such, in this example, the third peak
may be a second or third echo (the first or second echo being
obscured by the reverberation). By reducing or eliminating the
reverberation, for example by using the circuitry illustrated in
FIG. 3, such obscured echoes can be detected.
[0019] FIG. 3 illustrates a circuit 300 able to reduce and/or
eliminate reverberations in obstacle monitoring systems.
Specifically, damping circuitry 302 is coupled to transducer
circuitry 304 in order to reduce or eliminate reverberations on a
transducer, e.g. a piezo transducer. The transducer circuitry 304
includes a capacitor Cs, a resistor Rs, and an inductor Ls that
forms an equivalent resonance circuit for the transducer. The
damping circuitry 302 includes a capacitor Cp+C0, a resistor Rp,
and an inductor Lp that forms an equivalent tuned parallel resonant
circuit that dampens the transducer circuitry 302, where C0
represents a parasitic capacitance. The resonant frequency of the
transducer circuitry 304 is given by f=1/(2.pi.LsCs)). The damping
circuitry 302 is tuned to the same resonant frequency by adjusting
the values of one or more of Lp, Rp, and Cp. By maximizing the
resistance or impedance of the damping circuitry 302, without
creating circuit chattering, reduction in reverberation of the
transducer circuitry 304 may be maximized as well.
[0020] FIG. 4 illustrates system 400 for obstacle monitoring
including a circuit 401 coupled to a piezo transducer 402 and
optional transformer 404. The circuit 401 includes a receive
amplifier 406, an analog-to-digital converter ("ADC") 408, a
controller, a transmit driver 414, a digital-to-analog converter
("DAC") 416, a transmit amplifier 418. The controller may be a
damping digital filter, analog filter, correlator, integrator, or
derivator in various embodiments. For clarity, the example of a
digital damping filter 412 is used herein.
[0021] The transducer 402 transmits an ultrasonic pulse at an
obstacle and receives an ultrasonic echo from the obstacle. In at
least one embodiment, the obstacle may be monitored up to at least
five centimeters from the transducer 402, and the transducer 402
may include a two-pin piezo whether used with the transformer 404
or without the transformer 404. Next, the transducer 402 generates
a signal based on the echo and provides the signal to the circuit
401. The signal is processed by the receive amplifier 406 to remove
noise and/or increase desirable signal components. Next, the ADC
408 digitizes and/or samples the signal for input into the digital
damping filter 412.
[0022] The digital damping filter 412 is calibrated based on a
frequency response of the transducer 402 and the circuit 401. For
example, a square wave calibration pulse is transmitted, and the
impulse response to the pulse is captured by recording the
transducer voltage during the response. The digital damping filter
412 controls a damping current that reduces or eliminates
reverberation of the transducer 402. For example, the filter 412
controls a switch 420 that introduces circuitry 422 made up of any
number of circuit elements that provide the damping current.
Specifically, coefficients are selected for the digital damping
filter 412 based on a frequency response of the circuit 401 to the
signal. Specifically, the coefficients ensure wide band frequency
characteristics coexist with a high damping impedance. After the
signal is converted to an analog signal by the DAC 416 and
amplified for transmission by the transmit amplifier 418.
[0023] The digital damping filter 412 may be recalibrated upon
changes in the ambient temperature, the transducer 402, or the
transducer characteristics. In at least one embodiment, the
digitally created admittance may be calibrated in-field for current
temperature, piezo, external component, and other properties. This
calibration process may be automatic, i.e. may occur without human
input. Due to in-field calibration, damping time is independent of
temperature, production spread and aging. Accordingly, reduction or
elimination of reverberation can occur over a complete range of
temperatures (e.g. -40 to 85 degrees Celsius) and transducer
parameters. As such, the circuitry 401 is not finely tuned for one
transducer, but is able to be finely tuned for all transducers.
Accordingly, the circuity 401 has the flexibility to be used in
different environments and applications without modification.
[0024] FIG. 5 is a flow diagram of an illustrative method 500 for
obstacle monitoring. At 502, a wide band calibration pulse is
transmitted. For example, a wide band ultrasonic pulse is
transmitted at an obstacle to create an ultrasonic echo. The
ultrasonic echo is received from the obstacle, and at 504 the
impulse response to the echo is captured. For example, a signal
representing the impulse response is generated based on the
echo.
[0025] At 506, a damping finite impulse response ("FIR") filter is
calibrated by selecting coefficient values based on the frequency
response. In various embodiments, calibrating the filter is
accomplished in different ways. For example, calibrating the filter
may include measuring a resonance frequency and modifying the
coefficients for the filter based on the resonance frequency as
described above. As another example, calibrating the filter may
include measuring a junction or sensor temperature and modifying
the coefficients of the filter based on the junction or sensor
temperature. In another embodiment, calibrating the filter may
include measuring transmission power of a transmission that causes
the echo and modifying the coefficients for the digital damping
filter based on the transmission power.
[0026] At 508, reverberation is reduced or eliminated by
introducing the damping current controlled by digital damping
filter. As such, a time may be predicted at which the magnitude of
reverberation falls under a threshold. Accordingly, a signal,
received after the predicted time with a magnitude above the
threshold, may be interpreted as another echo and not as a
continuation of reverberation. The method 500 may also include
determining a distance from the transducer to an obstacle that
reflects the echo, and generating an alert if the distance is below
a threshold. Additionally, if the distance is below a threshold a
corrective action may be performed such as applying a braking force
to an automobile on which the transducer is located. Finally, the
method may include generating an audio, visual, or audiovisual
alert based on detected obstacles. Such alerts may be output
through displays, speakers, and the like.
[0027] In another embodiment of the present disclosure, damping may
be accomplished by driving the transducer out-of-resonance.
Specifically, an obstacle monitoring system includes a transducer
that receives an ultrasonic echo from an obstacle and generates a
signal based on the echo. The system further includes a controller
that drives the transducer in a first mode or a second mode. The
first mode includes driving the transducer at a resonance frequency
for relatively longer distances between the transducer and the
obstacle. The second mode includes driving the transducer at an
out-of-resonance frequency, higher than the resonance frequency,
for relatively shorter distances between the transducer and the
obstacle to reduce or eliminate reverberation of the
transducer.
[0028] In at least one embodiment, the systems or methods described
above are implemented in a parking assist system. For example, the
systems may include an automobile housing a computer-readable
medium coupled to one or more processors or controllers, which are
coupled to one or more transducers. The non-transitory
computer-readable medium may include instructions that, when
executed, cause the one or more processors to perform any
appropriate action described in this disclosure. The instructions
may, for example, be located on a module for implementing a driver
assistance system or a subsystem thereof in a vehicle, or an
application for driver assistance functions. The instructions may
be stored on a non-transitory machine-readable memory medium, for
example, on a permanent or rewritable memory medium or in
association with a computer device, for example, a removable
CD-ROM, DVD, or on a portable mobile memory medium, such as a
memory card or a USB stick. The transducers may be provided, for
example, in the front and/or rear bumper of the automobile for the
purpose of parking assistance and/or collision avoidance. Such a
system may, for example, be configured to detect partial
surroundings of the automobile. For example, transducers in the
front area for detecting surroundings ahead of the automobile,
transducers in the side area for detecting a side area of the motor
vehicle, and/or transducers in the rear area for detecting a rear
area of the automobile may each be included in the system. Such a
system may generate an audio, visual, or audiovisual alert based on
detected obstacles, and such alerts may be output through displays,
speakers, and the like.
[0029] In some aspects systems and method for obstacle monitoring
are provided according to one or more of the following
examples:
Example 1
[0030] An obstacle monitoring system includes a transducer that
receives an ultrasonic echo from an obstacle and generates a signal
based on the echo. The system further includes a controller coupled
to the transducer that is calibrated based on a frequency response
of the transducer and a coupling circuit. The system further
includes circuitry generating a damping current, controlled by the
controller, that reduces or eliminates reverberation of the
transducer.
Example 2
[0031] An obstacle monitoring method includes receiving an
ultrasonic echo from an obstacle, and generating a signal based on
the echo. The method further includes calibrating a circuit by
selecting coefficients for a filter based on a response to the
signal. The method further includes reducing or eliminating
reverberation by introducing a damping current controlled by a
controller.
Example 3
[0032] An obstacle monitoring system includes a transducer that
receives an ultrasonic echo from an obstacle and generates a signal
based on the echo. The system further includes a controller that
drives the transducer in a first mode or a second mode. The first
mode includes driving the transducer at a resonance frequency for
relatively longer distances between the transducer and the
obstacle. The second mode includes driving the transducer at an
out-of-resonance frequency, lower or higher than the resonance
frequency, for relatively shorter distances between the transducer
and the obstacle to reduce or eliminate reverberation of the
transducer.
[0033] The following features may be incorporated into the various
embodiments described above, such features incorporated either
individually in or conjunction with one or more of the other
features. The damping digital filter may be recalibrated upon
ambient temperature changes. The damping digital filter may be
recalibrated upon changes in the transducer or transducer
characteristics. The obstacle may be monitored up to at least five
centimeters from the transducer. The transducer may include a
two-pin piezo when used with a transformer or without a
transformer. The system may also include an automobile on which the
transducer is located. The transducer may be located on a bumper of
the automobile. The transducer may transmit an ultrasonic pulse at
the obstacle to create the echo. The method may also include
predicting a time when the magnitude of reverberation falls under a
threshold and interpreting a signal, received after the predicted
time with a magnitude above the threshold, as another echo and not
as a continuation of reverberation. Calibrating the circuit may
also include measuring a resonance frequency and modifying the
coefficients for the digital damping filter based on the resonance
frequency. Calibrating the circuit may also include measuring a
junction or sensor temperature and modifying the coefficients of
digital damping filter based on the junction or sensor temperature.
Calibrating the circuit may also include measuring transmission
power of a transmission (piezo voltage) that causes the echo and
modifying the coefficients for the digital damping filter based on
the transmission power (piezo voltage). The method may also include
transmitting an ultrasonic pulse at the obstacle to create the
echo. The method may also include determining a distance from the
transducer to the obstacle. The method may also include generating
an alert if the distance is below a threshold. The method may also
include performing a corrective action if the distance is below a
threshold. The corrective action may be applying a braking force to
an automobile on which the transducer is located.
[0034] Numerous other modifications, equivalents, and alternatives,
will become apparent to those skilled in the art once the above
disclosure is fully appreciated. It is intended that the following
claims be interpreted to embrace all such modifications,
equivalents, and alternatives where applicable.
* * * * *