CA2107198A1 - Method and apparatus for accurate acoustic distance measurement - Google Patents
Method and apparatus for accurate acoustic distance measurementInfo
- Publication number
- CA2107198A1 CA2107198A1 CA002107198A CA2107198A CA2107198A1 CA 2107198 A1 CA2107198 A1 CA 2107198A1 CA 002107198 A CA002107198 A CA 002107198A CA 2107198 A CA2107198 A CA 2107198A CA 2107198 A1 CA2107198 A1 CA 2107198A1
- Authority
- CA
- Canada
- Prior art keywords
- acoustic
- controller
- remote
- transceiver
- location
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
- G01S11/16—Systems for determining distance or velocity not using reflection or reradiation using difference in transit time between electrical and acoustic signals
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
- G01S5/30—Determining absolute distances from a plurality of spaced points of known location
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/003—Transmission of data between radar, sonar or lidar systems and remote stations
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus for accurate acoustic distance measurement is disclosed. A
transceiver pair comprising two acoustic transceiver units named 'controller' and 'remote' is employed to measure the distance between the transceivers simultaneously in both directions.
Thus, errors due to wind or fluid currents along the acoustic path are effectively cancelled.
Both units can instantaneously communicate with each other via wired or wireless means. The controller initiates measurement by sending an instantaneous trigger signal (a current pulse or electromagnetic pulse) synchronously with an acoustic pulse signal to the remote. At the same instant, a plurality of timers is started. Upon receipt of the instantaneous trigger, the remote sends its acoustic pulse signal to the controller. When the controller detects the acoustic signal from the remote a first timer is stopped, and when the remote detects the controller acoustic signal, an instantaneous trigger signal is sent from the remote to the controller to stop the second timer. Calculations within the controller determine the average distance measurement by using the ambient speed of sound and the timer data. Theapplication of this method and apparatus results in the following improvements over conventional methods of acoustic distance measurement: distance measurements with range expanded by a factor of 2 minimum over echo ranging; distance measurements with greater reliability, i.e. ambiguous measurement situations are resolved; distance measurements which are independent of target details; distance measurements with a higher measurement repeat rate than echo ranging or master-slave systems; distance measurements with ideal wind or fluid current compensation. In addition, the increased versatility of the system allows for uses such as small scale surveying and three-dimensional mapping realized by mounting the controller on a goniometer or transit and aiming at the remote, or by employing multiple remote transceivers with a single controller. Any application where motion of the medium of acoustic transport affects accuracy will benefit from the use of this invention.
A method and apparatus for accurate acoustic distance measurement is disclosed. A
transceiver pair comprising two acoustic transceiver units named 'controller' and 'remote' is employed to measure the distance between the transceivers simultaneously in both directions.
Thus, errors due to wind or fluid currents along the acoustic path are effectively cancelled.
Both units can instantaneously communicate with each other via wired or wireless means. The controller initiates measurement by sending an instantaneous trigger signal (a current pulse or electromagnetic pulse) synchronously with an acoustic pulse signal to the remote. At the same instant, a plurality of timers is started. Upon receipt of the instantaneous trigger, the remote sends its acoustic pulse signal to the controller. When the controller detects the acoustic signal from the remote a first timer is stopped, and when the remote detects the controller acoustic signal, an instantaneous trigger signal is sent from the remote to the controller to stop the second timer. Calculations within the controller determine the average distance measurement by using the ambient speed of sound and the timer data. Theapplication of this method and apparatus results in the following improvements over conventional methods of acoustic distance measurement: distance measurements with range expanded by a factor of 2 minimum over echo ranging; distance measurements with greater reliability, i.e. ambiguous measurement situations are resolved; distance measurements which are independent of target details; distance measurements with a higher measurement repeat rate than echo ranging or master-slave systems; distance measurements with ideal wind or fluid current compensation. In addition, the increased versatility of the system allows for uses such as small scale surveying and three-dimensional mapping realized by mounting the controller on a goniometer or transit and aiming at the remote, or by employing multiple remote transceivers with a single controller. Any application where motion of the medium of acoustic transport affects accuracy will benefit from the use of this invention.
Description
2:l~71~
METHOD AND APPARATUS FOR Ag::CURaTE ACOUSTIC DISTANCE MEASlJREMENT
This invention relates to acoustic distance measurement, more specifically, to a method and apparatus for impreving the accuracy of acoustic distance measurement, for extending the maximum range, increase versatility, increiase measurement repeat rate, and increase the reliability of acoustic distance measurement. Furthermore, this invention relates to a method of eliminating acoustic distance measurement errors due to air or fluid currents.
Commercially available acoustic distance measuring devices generally operate in a configuration similar to SONAR. The travel ~ime of an acoustic pulse propagating in some medium ( e.g. air, water ) from the device to a reflective target and back to the point of origin is measurad and the distance calculated ~rom the known ambient speed of sound. A necessary criterion for reliabla m~asurements with such devices is a well-defined target, (i.e. Iarge, flat, smooth, oriented perpendicular to the incidant beam), so as to reflect a siynificant portion of the incident signal back towards the source. Thus the use of such a distance mster is severely limited by th~ quality of the target. In addition, the presence of other reflective objects in the acoustic path can lead to misleading results.
Attempts to correct thes0 faults have resulted in acoustic distance measuremant sys-t0ms comprised of a transmitting unit and a receiving unit separated by the distance to bs measured. The acoustic pulse only travels in one direction along the acoustic path, i.e. from the transmitter unit to the receiver unit. Therefore, such a system is more severaly affected by motion of the medium of acoustic transport (e.g. wind, current), since Ihere i5 no cancellation of motion as in echo ranging. Some of the known three-dimensional digitizin~ systems (e.g.
U.S. patents: 5,043,950 and 5,142,506) operate on this principle, and are therefore limited to measurements in very still air. Alternatively, a master and slave transceiver pair can be employed to simulate the echo ranging apparatus. The acoustic pulse travels in both ~1~ 71~8 directions along the acoustic path, from a master transceiver unit to a slave transceiver unit which transmits a return pulse back to the master. However, many of the known acoustic distance measurement systems utilizing a master/slave transceiver pair (e.g. U.S. patents:
4,254,478, 4,894,810, and 5,175,695) employ an electronic delay at the master or slave transceiver to ensura that all spurious echoes have died out. Typical delay times can be of the order of 200ms, allowing for significant changes in the characteristics of air (e.g. wind, temperature) between the rnaster and slave, resulting in increased ranging errors. The rneasurernent repeat rate is also reduced by any electronic delay. A different master/slave system which does not employ any additional delays is described in U.S. patent: 3,076,519.
In that particular method, tha master and slave transceivers oparate with different transmitting frequencies to which only the opposite unit is responsive. This typically requires separate transmitter and receiver elements at both master and slave units. Furthermore, the performance is unpredictable for m0asurements of shorter distances where strong signals of the first frequency can erroneously trigg~r the receiver tuned ~o the second frequency.
A disadvantage of the master/slave systems comparod to the ~ransmitter/receiver sys-tems is a much lower measurement repcat rate. An advantage of the master/slave systems over the transmitter/receiver systems is its partial current compensation feature. An ideal acoustic ranging system would combine the fast measurement repeat rate of transmitter/re-ceiver systems with the wind/current compensation of the master/slave systems.
It is a principal object of the present invention to provide a method and apparatus for accurate acoustic distance measurement.
It is another object of the present invention to provide a distance measuring system which is operative for a distance far greater than scho-ranging systems.
It is another objsct of the presant invention ~o provide a distance measuring system with a measurement repeat rate far greater than known master/slave systems.
~? ~ ~ 7 ~
It is yet anoliher object of the present invention to provide a distance measuring system with wind or current-compensating features which are rnore accurate than any known system, allowing one to make distaince measurements in environments where the medium of acoustic transport is subject to currents and other movements which otherwise restrict the use of acoustic ranging devices.
The present invention operates with the provision of two transcaiver units named'controller' and 'remote' in which the remote is locat0d at a first location, and the controller is located at a second location. Each transceiver unit is operative to first generate and transmit an acoustic pulse signal and subsequently receive the acoustic signal from another transceiver. Timer means are provided by a plurality of timers situated within the controller or in a separate 'master commander', as are calculation means for computing distance from timer values and the ambient speed of sound. The measured times of flight between transceivers ara used along with the known ambient speed of sound to compulie the distance between the transc~ivers. In addition, each transceiver and master commander is equipped with an instantaneous trigger m~ans for synchronizing transmission of acoustic pulses from the controller and remote, and for sending starVstop commands to the timer means. This trigger mechanism can be one of a number of options such as radio wave, infrared light, a current pulse through a wire means, or other, provided that such trigger pulses are instantaneous with respect to th0 speed of sound. Any pulse travelling at the speed of light satisfies this requiremen~i.
The novel feature of the invention is the provision for transmitting acoustic pulses frorn the controller to a remote, and at the same instanli, transmitting acoustic pulses from the remote to the controller. Thus, each distance measurement comprises two simultaneous acoustic transmissions propagating in opposite directions along the acoustic path between the controller and ~mote. The resulting distance measurement effectively eliminates errors due to wind or fluid motion along the acoustic path. Measurement repeat rate is approximately 2:~7 ~ ~8 double that of echo-ranging systems, and at leas~ double that of systems such as US Patents:
5,175,695; 5,140,859; 4,894,810. Furthermore, the present invention will have improved accuracy over systems which measure distance in only one direction along the acoustic ,oath (e.g. US Patent: 5,043,950), with no loss in the high measurement repeat rates offered by such systems.
In drawings which illustrats the embodiments of the invention:
Fi~. 1 is an illustration describing the effact of air/fluid motion on acoustic distance measurements.
Fi~. 2 is a general arrangement diagram of the present invention showing the opera-tion sequences resulting in a one-dimensional distance measurement.
Fig. 3 is an alternate embodiment of the present invention ernploying a master commander.
Fig. 4 is a diagram showing tho time/signal characteristics for the preferrsd embodi ment of the present invention.
Fi~. 5 is a diagram showing the measurament protocol for the prsfefred embodiment of the present invention.
Fig. 6 is an illustration showing the application of the present invention to two-dimensional distance measurement.
Fig. 7 is an illus~ration showing the application of the prssent invention to three-dimensional distance measurement.
It is clear that the present inven~ion is operative in several media, e.g. air, other gases,and fluids, and that the instantaneous trigger signal can be realized by wired or wireless means. For simplicity and convenience, ~he preferred embodiment will be discussed with the assumption that the rnedium of acoustic transport is air, and the trigger signal is provided by wireless means. However, we make no restrictions on the other options available.Fig. 1 illustra~s the basic principle behind the present invention. A first acoustic trans-ceiver 1 and a second acoustic transceiYer 2 are separateci by some unknown dis~ance, and a wind 5 is blowing between the two transceivers at a given instant in ~ime. An acoustic wave (shock-wave, sonic, infrasonic or ultrasonic) 3 generated by acoustic transceiver ti is prop-agated through th~ air (or fluid) at a velocity equal to the spead of sound in still air plus the vector component of the wind velocity along the acoustic path in the direction of propagation of the acoustic pulse 3. This results in a faster time of flight for the acoustic pulse 3 which relates to a shorter perceived distance than is expected. In the case of acoustic transceiver 2 transmitting an acoustic wavc 4 in the opposite dir~ction, the wave 4 also propagates with velocity equal to the speed of sound in still air plus the vector cornponent of the wind velocity along ths acoustic path in the dir0ction of propagation of the acoustic pulse 4. This results in a longer time of flight for the acoustic puls9 4, hence a longer distance rneasurement is perceiv~d. Thus, if acoustic pulse 3 and acoustic pulse 4 are simultaneously transmitted from tranæceiver 1 to transceiver 2 and from transceiver 2 to transceiver 1 respectively, the error contriblution due to air or fiuid motion 5 can be eliminated by averaging the two rneasurements. It is this wind compensation which is the basis of the presellt inven~ion.
Accuracy irnprovements to distance, velocity, or acceleration measurements in other ~aseous or fluid media are possible with the application of the present invention.
7 ~ ~ ~
Fig. 2 shows a general arrangement of the present invention and its operation protocol.
The controlier transcaiver ~0 comprises acoustic transceiver circuitry ~1 and transducer means 12, an instantaneous trigger signal communications means 13, and a signal processing module 14 which contains a plurality of timer means, calculations means for computing distances, a means for storing results in a memory, and a display means for displaying the measured distance. The remote transceiver 20 comprises acoustic transceiver circuitry ~1 and transducer means 22, an instantaneous trigger signal communications means 23, and an indicator signal generating means 24 by which reception of acoustic pulses at the remote 20 are indicated to a user at a distant location away from the remote 20. The transducer means 12, 22 comprises a single acoustic transducer for both transmitting and receiving, or alternatively, separats transmitter and receiver elements.
In the alternate embodiment of the present invention shown in fig. 3, the signalprocessing module 14 may reside in a central master commander 30 removed from the controller as a separate unit 34 which interacts with tha controller and remote transceivers via instantaneous trigger signal communication means 31 to perform control, timing, calculating, storing, displaying, and other processing functions. The controller 10 still retains its own signal processing module 14 so that results can be communicated trom the mas~er commander 30 to the controllar 10 and displayad at the controller 10.
As illustrated in fig. 2, ~ig.4, and fig. 5, a typical measurement sequencs for a single controller/remote transceiver pair consists of the following steps. An acoustic pulse 15 and an instantaneous trigger signal 16 are sent synchronously from the controller 10 to the remote 20, and timers in tha signal processing module 14 at the controller 10 are started. The remote 20 r~ceives the instantaneous trigger signal 16 and immediately transmits its own acoustic pulse 25 to the controll2r 10. Since the trigger signal 16 propagatin~ at the speed of light is effectively instantaneous with respe~ to the acous~ic signal 15, there is no perceived delay ~etween the transmission of acoustic pulse 15 from ~he controller 10 and the transmission of ~1071~8 acoustic pulse 25 from remote 20, therefore the controller 10 and remote 2û generate their respective acoustic pulses at the same instant. After a time tll indicated in fig. 4, the remote 20 receives the controller's acoustic pulsa 15 and irnmediately sends an instantaneous trigger signal 26 to the controller 10 to halt a timer. At the same instant, the indicator signal generating maans 2~ in the remo~e 20 generates an indicator signal (e.g. audio signal or visible light strobe) to confirm detection of the acoustic puise 15. After a time t2 indicated in fig.4, controller 10 rec0ives the remote's acoustic pulse 25 and immediately stops a second timer in the signal processing module 14 inside the controller 10. The timer data is then used with ~he ambient speed of sound value to calculate the avera~e distance by means of the calculation capabilities of the signal processing module 14, thus giving a wind-compensated distance measurement. The result is displayed and optionally stored in a memory by means of the signal processing module 14 at the controller 10. It should be noted that any method can be used to determine the ambiant speed of sound, provided the method is accurate. If the speed of sound is measured by a separate acoustical determination, th~n the method of the present invention should be applied in order to eliminate wind or current errors and achicvs the most accurate value for the ambient speed of sound.
In the alternate embodiment of the present inven~ion shown in fig. 3, the measurement sequ~nce for a single controller/remote transceiver pair is initiated by an instantaneous trigger pulse 16 generated at the controller transceiver. The master commander 30 receives the instantaneous trigger pulse 16, sends an instantancous trigger pulse 32 to the controller 10 and remote 20, and starts a plurality of timers in the signal processing module 34. Upnn receipt o~ the instantaneous trigger pulse 32, the controller 10 and remote 20 triansrnit their respective ~coustic pulses synchronously; the controller 10 transmits its acoustie pulse 15 to the remote 20, and at the same instant, the rernote 20 transmits its iacoustic pulse 25 to the controller 10. At the instant the oontroller 10 recaivas the remote's acoustio pulse 25, the controller 10 transmits an instantaneous trigger pulse 17 to the master commander 30, ~071 9~(~
whareby a first ~imer is stopped. Upon receipt of the controller's acoustic puise 15, the remote 20 transmits an instantaneous trigger pulse 27 to the master commander 30, whereby a second timer is stapped. At the same instant, the indicator signal generating means 24 generates an indicator signal, e.g. an audio pulse or visible light strobe, so as to confirm detection of the controller's acoustic pulse 15 at the remote 20. The calculation means within the si~nal processing module 34 uses the timer data and the ambient speed of sound value to calculata the average distance between the controller 10 and remote 20. Results may be stored in a memory and displayed by means of the si~nal processing module 34 Also, the measurement is optionally sent to the controller 10 via coded instantaneous pulse signals so that measurements are processed and displayed at the controller 10.
As the attenuation of sound is frequency dependent, the frequency of the acoustic pulses 15, 25 will be chosen to give the desired maximum range of the system. Typical frequencies of interest could be 25 - 250 kHz for acoustic ranging in air, 150 kHz to 2 MHz for acoustic ranging in water. The preferred embodiment is able to discriminate against spurious echoes from nearby obstacles by means of peak detection or signal processing whereby only the strongest, unreflected signals are recognized. This technology is well known and is not claimed in this invention.
An additional capability of the invsntion resulting from the high measurement repeat rate is m~asurement of velocity or acceleration of a remote transceiver 20 with respact to the controller transceiver 10. A series of distance measurements together with the known elapsed time ~etween each mcasurement givss the instantaneous velocity and acc~leration of the remota 20 with respect to the controller 10. Also, the instantanaous velocity of the medium of acoustic transport can be easily calculated from the times of flight of the first acoustic pulse 15 and the second acoustic pulse 25. This wind or current velocity can then be displayed and stored along with the corresponding distance measurement.
~ ~7~
Position measurements in higher dimensiorls can be made by employing a plurality o~
remote transceivers placed at known locations. Figure 6 illustrates the application of the present invention to two-dimensional mapping. At least two remote transceivers 2Ua, 20b are placed a known distance apart such that Ihey define a coordinate sys~em. A first remote transceiver 20a reprasents the origin of th~ coordinate system, while a second remote transceiver 20b represents the y-axis as shown in figure 6. The location of the controll~r transceiver 10 is easily determined by measuring ~he distance between each controller/remote transceiver pair sequentially, (i.e. remote transceiver 20a and the controller 10, and remote transceiver 20b and controller 10), and then triangulating using the wind-compensated distances between transceiver pairs and the distance separating the remote transceivers 2Ua, 20b. Furthermore, tha high measurement repeat rate of the present invention allows for two-dimensional wind-compensated velocity and accelera~ion measurements.
Three-dimensional mapping is realized by employing at least thre~ remote transceivers placed at known locations defining a coordinate system as illustrated in figure 7. A first remote transceiver 20a represents the origin of the coordinate systern, a second remote transceivar 20b represents the y-axis, and a third remote transceivar 20c represents the x-axis. The location of the controller transceiver 10 in three-dimensions is easily determined by measuring the distance between each controller/remote transceiver pair sequentially, (i.e.
remote transceiver 2Qa and the controller 10, remote transceiver 20b and con~roller 10, and remote transceivor 20c and the controller 10), and then triangulating using the wind-compensated distances between transceiver pairs and the distances separa~ing the remote transceivers 20a, 20b, 20c. As previously statad, the high measurement repeat rate of the present invention allows for wind-compensated velocity and acceleration measurements in higher dimensions.
Alternatively, a single con~roll~r/remote transceiver pair may be employed for mapping in highar dimensions by mounting the controller transceiver 1G on a transit or goniometer and ~1 ~7~n~
aiming at the remote 2û. The resulting wind-compensated distance measurement and the measured angles on the transit or goniometer give the two or three-dimensional location of the remote 20 with respect to the controller 10~
While the invention has been described in what is pr~sently considered to be a preferred embodiment, many variations and modifications will be apparent to those skilled in the art. Therefore, it is intended that the invention not be limited to this embodiment but be interpreted within the spirit and scope of ~he appended claims.
METHOD AND APPARATUS FOR Ag::CURaTE ACOUSTIC DISTANCE MEASlJREMENT
This invention relates to acoustic distance measurement, more specifically, to a method and apparatus for impreving the accuracy of acoustic distance measurement, for extending the maximum range, increase versatility, increiase measurement repeat rate, and increase the reliability of acoustic distance measurement. Furthermore, this invention relates to a method of eliminating acoustic distance measurement errors due to air or fluid currents.
Commercially available acoustic distance measuring devices generally operate in a configuration similar to SONAR. The travel ~ime of an acoustic pulse propagating in some medium ( e.g. air, water ) from the device to a reflective target and back to the point of origin is measurad and the distance calculated ~rom the known ambient speed of sound. A necessary criterion for reliabla m~asurements with such devices is a well-defined target, (i.e. Iarge, flat, smooth, oriented perpendicular to the incidant beam), so as to reflect a siynificant portion of the incident signal back towards the source. Thus the use of such a distance mster is severely limited by th~ quality of the target. In addition, the presence of other reflective objects in the acoustic path can lead to misleading results.
Attempts to correct thes0 faults have resulted in acoustic distance measuremant sys-t0ms comprised of a transmitting unit and a receiving unit separated by the distance to bs measured. The acoustic pulse only travels in one direction along the acoustic path, i.e. from the transmitter unit to the receiver unit. Therefore, such a system is more severaly affected by motion of the medium of acoustic transport (e.g. wind, current), since Ihere i5 no cancellation of motion as in echo ranging. Some of the known three-dimensional digitizin~ systems (e.g.
U.S. patents: 5,043,950 and 5,142,506) operate on this principle, and are therefore limited to measurements in very still air. Alternatively, a master and slave transceiver pair can be employed to simulate the echo ranging apparatus. The acoustic pulse travels in both ~1~ 71~8 directions along the acoustic path, from a master transceiver unit to a slave transceiver unit which transmits a return pulse back to the master. However, many of the known acoustic distance measurement systems utilizing a master/slave transceiver pair (e.g. U.S. patents:
4,254,478, 4,894,810, and 5,175,695) employ an electronic delay at the master or slave transceiver to ensura that all spurious echoes have died out. Typical delay times can be of the order of 200ms, allowing for significant changes in the characteristics of air (e.g. wind, temperature) between the rnaster and slave, resulting in increased ranging errors. The rneasurernent repeat rate is also reduced by any electronic delay. A different master/slave system which does not employ any additional delays is described in U.S. patent: 3,076,519.
In that particular method, tha master and slave transceivers oparate with different transmitting frequencies to which only the opposite unit is responsive. This typically requires separate transmitter and receiver elements at both master and slave units. Furthermore, the performance is unpredictable for m0asurements of shorter distances where strong signals of the first frequency can erroneously trigg~r the receiver tuned ~o the second frequency.
A disadvantage of the master/slave systems comparod to the ~ransmitter/receiver sys-tems is a much lower measurement repcat rate. An advantage of the master/slave systems over the transmitter/receiver systems is its partial current compensation feature. An ideal acoustic ranging system would combine the fast measurement repeat rate of transmitter/re-ceiver systems with the wind/current compensation of the master/slave systems.
It is a principal object of the present invention to provide a method and apparatus for accurate acoustic distance measurement.
It is another object of the present invention to provide a distance measuring system which is operative for a distance far greater than scho-ranging systems.
It is another objsct of the presant invention ~o provide a distance measuring system with a measurement repeat rate far greater than known master/slave systems.
~? ~ ~ 7 ~
It is yet anoliher object of the present invention to provide a distance measuring system with wind or current-compensating features which are rnore accurate than any known system, allowing one to make distaince measurements in environments where the medium of acoustic transport is subject to currents and other movements which otherwise restrict the use of acoustic ranging devices.
The present invention operates with the provision of two transcaiver units named'controller' and 'remote' in which the remote is locat0d at a first location, and the controller is located at a second location. Each transceiver unit is operative to first generate and transmit an acoustic pulse signal and subsequently receive the acoustic signal from another transceiver. Timer means are provided by a plurality of timers situated within the controller or in a separate 'master commander', as are calculation means for computing distance from timer values and the ambient speed of sound. The measured times of flight between transceivers ara used along with the known ambient speed of sound to compulie the distance between the transc~ivers. In addition, each transceiver and master commander is equipped with an instantaneous trigger m~ans for synchronizing transmission of acoustic pulses from the controller and remote, and for sending starVstop commands to the timer means. This trigger mechanism can be one of a number of options such as radio wave, infrared light, a current pulse through a wire means, or other, provided that such trigger pulses are instantaneous with respect to th0 speed of sound. Any pulse travelling at the speed of light satisfies this requiremen~i.
The novel feature of the invention is the provision for transmitting acoustic pulses frorn the controller to a remote, and at the same instanli, transmitting acoustic pulses from the remote to the controller. Thus, each distance measurement comprises two simultaneous acoustic transmissions propagating in opposite directions along the acoustic path between the controller and ~mote. The resulting distance measurement effectively eliminates errors due to wind or fluid motion along the acoustic path. Measurement repeat rate is approximately 2:~7 ~ ~8 double that of echo-ranging systems, and at leas~ double that of systems such as US Patents:
5,175,695; 5,140,859; 4,894,810. Furthermore, the present invention will have improved accuracy over systems which measure distance in only one direction along the acoustic ,oath (e.g. US Patent: 5,043,950), with no loss in the high measurement repeat rates offered by such systems.
In drawings which illustrats the embodiments of the invention:
Fi~. 1 is an illustration describing the effact of air/fluid motion on acoustic distance measurements.
Fi~. 2 is a general arrangement diagram of the present invention showing the opera-tion sequences resulting in a one-dimensional distance measurement.
Fig. 3 is an alternate embodiment of the present invention ernploying a master commander.
Fig. 4 is a diagram showing tho time/signal characteristics for the preferrsd embodi ment of the present invention.
Fi~. 5 is a diagram showing the measurament protocol for the prsfefred embodiment of the present invention.
Fig. 6 is an illustration showing the application of the present invention to two-dimensional distance measurement.
Fig. 7 is an illus~ration showing the application of the prssent invention to three-dimensional distance measurement.
It is clear that the present inven~ion is operative in several media, e.g. air, other gases,and fluids, and that the instantaneous trigger signal can be realized by wired or wireless means. For simplicity and convenience, ~he preferred embodiment will be discussed with the assumption that the rnedium of acoustic transport is air, and the trigger signal is provided by wireless means. However, we make no restrictions on the other options available.Fig. 1 illustra~s the basic principle behind the present invention. A first acoustic trans-ceiver 1 and a second acoustic transceiYer 2 are separateci by some unknown dis~ance, and a wind 5 is blowing between the two transceivers at a given instant in ~ime. An acoustic wave (shock-wave, sonic, infrasonic or ultrasonic) 3 generated by acoustic transceiver ti is prop-agated through th~ air (or fluid) at a velocity equal to the spead of sound in still air plus the vector component of the wind velocity along the acoustic path in the direction of propagation of the acoustic pulse 3. This results in a faster time of flight for the acoustic pulse 3 which relates to a shorter perceived distance than is expected. In the case of acoustic transceiver 2 transmitting an acoustic wavc 4 in the opposite dir~ction, the wave 4 also propagates with velocity equal to the speed of sound in still air plus the vector cornponent of the wind velocity along ths acoustic path in the dir0ction of propagation of the acoustic pulse 4. This results in a longer time of flight for the acoustic puls9 4, hence a longer distance rneasurement is perceiv~d. Thus, if acoustic pulse 3 and acoustic pulse 4 are simultaneously transmitted from tranæceiver 1 to transceiver 2 and from transceiver 2 to transceiver 1 respectively, the error contriblution due to air or fiuid motion 5 can be eliminated by averaging the two rneasurements. It is this wind compensation which is the basis of the presellt inven~ion.
Accuracy irnprovements to distance, velocity, or acceleration measurements in other ~aseous or fluid media are possible with the application of the present invention.
7 ~ ~ ~
Fig. 2 shows a general arrangement of the present invention and its operation protocol.
The controlier transcaiver ~0 comprises acoustic transceiver circuitry ~1 and transducer means 12, an instantaneous trigger signal communications means 13, and a signal processing module 14 which contains a plurality of timer means, calculations means for computing distances, a means for storing results in a memory, and a display means for displaying the measured distance. The remote transceiver 20 comprises acoustic transceiver circuitry ~1 and transducer means 22, an instantaneous trigger signal communications means 23, and an indicator signal generating means 24 by which reception of acoustic pulses at the remote 20 are indicated to a user at a distant location away from the remote 20. The transducer means 12, 22 comprises a single acoustic transducer for both transmitting and receiving, or alternatively, separats transmitter and receiver elements.
In the alternate embodiment of the present invention shown in fig. 3, the signalprocessing module 14 may reside in a central master commander 30 removed from the controller as a separate unit 34 which interacts with tha controller and remote transceivers via instantaneous trigger signal communication means 31 to perform control, timing, calculating, storing, displaying, and other processing functions. The controller 10 still retains its own signal processing module 14 so that results can be communicated trom the mas~er commander 30 to the controllar 10 and displayad at the controller 10.
As illustrated in fig. 2, ~ig.4, and fig. 5, a typical measurement sequencs for a single controller/remote transceiver pair consists of the following steps. An acoustic pulse 15 and an instantaneous trigger signal 16 are sent synchronously from the controller 10 to the remote 20, and timers in tha signal processing module 14 at the controller 10 are started. The remote 20 r~ceives the instantaneous trigger signal 16 and immediately transmits its own acoustic pulse 25 to the controll2r 10. Since the trigger signal 16 propagatin~ at the speed of light is effectively instantaneous with respe~ to the acous~ic signal 15, there is no perceived delay ~etween the transmission of acoustic pulse 15 from ~he controller 10 and the transmission of ~1071~8 acoustic pulse 25 from remote 20, therefore the controller 10 and remote 2û generate their respective acoustic pulses at the same instant. After a time tll indicated in fig. 4, the remote 20 receives the controller's acoustic pulsa 15 and irnmediately sends an instantaneous trigger signal 26 to the controller 10 to halt a timer. At the same instant, the indicator signal generating maans 2~ in the remo~e 20 generates an indicator signal (e.g. audio signal or visible light strobe) to confirm detection of the acoustic puise 15. After a time t2 indicated in fig.4, controller 10 rec0ives the remote's acoustic pulse 25 and immediately stops a second timer in the signal processing module 14 inside the controller 10. The timer data is then used with ~he ambient speed of sound value to calculate the avera~e distance by means of the calculation capabilities of the signal processing module 14, thus giving a wind-compensated distance measurement. The result is displayed and optionally stored in a memory by means of the signal processing module 14 at the controller 10. It should be noted that any method can be used to determine the ambiant speed of sound, provided the method is accurate. If the speed of sound is measured by a separate acoustical determination, th~n the method of the present invention should be applied in order to eliminate wind or current errors and achicvs the most accurate value for the ambient speed of sound.
In the alternate embodiment of the present inven~ion shown in fig. 3, the measurement sequ~nce for a single controller/remote transceiver pair is initiated by an instantaneous trigger pulse 16 generated at the controller transceiver. The master commander 30 receives the instantaneous trigger pulse 16, sends an instantancous trigger pulse 32 to the controller 10 and remote 20, and starts a plurality of timers in the signal processing module 34. Upnn receipt o~ the instantaneous trigger pulse 32, the controller 10 and remote 20 triansrnit their respective ~coustic pulses synchronously; the controller 10 transmits its acoustie pulse 15 to the remote 20, and at the same instant, the rernote 20 transmits its iacoustic pulse 25 to the controller 10. At the instant the oontroller 10 recaivas the remote's acoustio pulse 25, the controller 10 transmits an instantaneous trigger pulse 17 to the master commander 30, ~071 9~(~
whareby a first ~imer is stopped. Upon receipt of the controller's acoustic puise 15, the remote 20 transmits an instantaneous trigger pulse 27 to the master commander 30, whereby a second timer is stapped. At the same instant, the indicator signal generating means 24 generates an indicator signal, e.g. an audio pulse or visible light strobe, so as to confirm detection of the controller's acoustic pulse 15 at the remote 20. The calculation means within the si~nal processing module 34 uses the timer data and the ambient speed of sound value to calculata the average distance between the controller 10 and remote 20. Results may be stored in a memory and displayed by means of the si~nal processing module 34 Also, the measurement is optionally sent to the controller 10 via coded instantaneous pulse signals so that measurements are processed and displayed at the controller 10.
As the attenuation of sound is frequency dependent, the frequency of the acoustic pulses 15, 25 will be chosen to give the desired maximum range of the system. Typical frequencies of interest could be 25 - 250 kHz for acoustic ranging in air, 150 kHz to 2 MHz for acoustic ranging in water. The preferred embodiment is able to discriminate against spurious echoes from nearby obstacles by means of peak detection or signal processing whereby only the strongest, unreflected signals are recognized. This technology is well known and is not claimed in this invention.
An additional capability of the invsntion resulting from the high measurement repeat rate is m~asurement of velocity or acceleration of a remote transceiver 20 with respact to the controller transceiver 10. A series of distance measurements together with the known elapsed time ~etween each mcasurement givss the instantaneous velocity and acc~leration of the remota 20 with respect to the controller 10. Also, the instantanaous velocity of the medium of acoustic transport can be easily calculated from the times of flight of the first acoustic pulse 15 and the second acoustic pulse 25. This wind or current velocity can then be displayed and stored along with the corresponding distance measurement.
~ ~7~
Position measurements in higher dimensiorls can be made by employing a plurality o~
remote transceivers placed at known locations. Figure 6 illustrates the application of the present invention to two-dimensional mapping. At least two remote transceivers 2Ua, 20b are placed a known distance apart such that Ihey define a coordinate sys~em. A first remote transceiver 20a reprasents the origin of th~ coordinate system, while a second remote transceiver 20b represents the y-axis as shown in figure 6. The location of the controll~r transceiver 10 is easily determined by measuring ~he distance between each controller/remote transceiver pair sequentially, (i.e. remote transceiver 20a and the controller 10, and remote transceiver 20b and controller 10), and then triangulating using the wind-compensated distances between transceiver pairs and the distance separating the remote transceivers 2Ua, 20b. Furthermore, tha high measurement repeat rate of the present invention allows for two-dimensional wind-compensated velocity and accelera~ion measurements.
Three-dimensional mapping is realized by employing at least thre~ remote transceivers placed at known locations defining a coordinate system as illustrated in figure 7. A first remote transceiver 20a represents the origin of the coordinate systern, a second remote transceivar 20b represents the y-axis, and a third remote transceivar 20c represents the x-axis. The location of the controller transceiver 10 in three-dimensions is easily determined by measuring the distance between each controller/remote transceiver pair sequentially, (i.e.
remote transceiver 2Qa and the controller 10, remote transceiver 20b and con~roller 10, and remote transceivor 20c and the controller 10), and then triangulating using the wind-compensated distances between transceiver pairs and the distances separa~ing the remote transceivers 20a, 20b, 20c. As previously statad, the high measurement repeat rate of the present invention allows for wind-compensated velocity and acceleration measurements in higher dimensions.
Alternatively, a single con~roll~r/remote transceiver pair may be employed for mapping in highar dimensions by mounting the controller transceiver 1G on a transit or goniometer and ~1 ~7~n~
aiming at the remote 2û. The resulting wind-compensated distance measurement and the measured angles on the transit or goniometer give the two or three-dimensional location of the remote 20 with respect to the controller 10~
While the invention has been described in what is pr~sently considered to be a preferred embodiment, many variations and modifications will be apparent to those skilled in the art. Therefore, it is intended that the invention not be limited to this embodiment but be interpreted within the spirit and scope of ~he appended claims.
Claims (10)
1. A method of measuring the distance between a first location and a second location comprising:
(a) positioning a controller transceiver means for transmitting and receiving acoustic pulse signals and for transmitting and receiving instantaneous trigger pulse signals at said first location, (b) positioning a remote transceiver means for transmitting and receiving acoustic pulse signals and for transmitting and receiving instantaneous trigger pulse signals at said second location, (c) generating a first instantaneous trigger pulse signal and a first acoustic pulse signal by means of said controller transceiver for transmitting said first instantaneous trigger pulse signal and said first acoustic pulse signal to said remote transceiver means, whereby a plurality of timer means is started, (d) generating a second acoustic pulse signal by means of said remote transceiver upon receipt of said first instantaneous trigger pulse signal at said remote transceiver, whereby said first acoustic pulse signal and said second acoustic pulse signal travel simultaneously in opposite directions along the acoustic path between said first location and said second location, (e) receiving said second acoustic pulse signal by said controller transceiver means, whereby a first timer means is stopped, (f) receiving said first acoustic pulse signal by said remote transceiver means, whereby a second instantaneous trigger pulse is transmitted to said controller transceiver means by means of said remote transceiver, (g) receiving said second instantaneous trigger pulse signal at said controller transceiver means, whereby a second timer means is stopped, (h) measuring the ambient speed of sound (i) calculating the distance between said first location and said second location from the measured times of flight of said first acoustic pulse signal and said second acoustic pulse signal and the ambient speed of sound, whereby random and systematic errors in said times of flight due to the motion of the medium of acoustic transport are cancelled upon averaging said times of flight of said first acoustic pulse signal and said second acoustic pulse signal, (j) displaying said distance measurements in at least the controller transceiver, whereby distance measurements for said first acoustic pulse signal and said second acoustic pulse signal and the calculated average distance measurement are displayed.
(a) positioning a controller transceiver means for transmitting and receiving acoustic pulse signals and for transmitting and receiving instantaneous trigger pulse signals at said first location, (b) positioning a remote transceiver means for transmitting and receiving acoustic pulse signals and for transmitting and receiving instantaneous trigger pulse signals at said second location, (c) generating a first instantaneous trigger pulse signal and a first acoustic pulse signal by means of said controller transceiver for transmitting said first instantaneous trigger pulse signal and said first acoustic pulse signal to said remote transceiver means, whereby a plurality of timer means is started, (d) generating a second acoustic pulse signal by means of said remote transceiver upon receipt of said first instantaneous trigger pulse signal at said remote transceiver, whereby said first acoustic pulse signal and said second acoustic pulse signal travel simultaneously in opposite directions along the acoustic path between said first location and said second location, (e) receiving said second acoustic pulse signal by said controller transceiver means, whereby a first timer means is stopped, (f) receiving said first acoustic pulse signal by said remote transceiver means, whereby a second instantaneous trigger pulse is transmitted to said controller transceiver means by means of said remote transceiver, (g) receiving said second instantaneous trigger pulse signal at said controller transceiver means, whereby a second timer means is stopped, (h) measuring the ambient speed of sound (i) calculating the distance between said first location and said second location from the measured times of flight of said first acoustic pulse signal and said second acoustic pulse signal and the ambient speed of sound, whereby random and systematic errors in said times of flight due to the motion of the medium of acoustic transport are cancelled upon averaging said times of flight of said first acoustic pulse signal and said second acoustic pulse signal, (j) displaying said distance measurements in at least the controller transceiver, whereby distance measurements for said first acoustic pulse signal and said second acoustic pulse signal and the calculated average distance measurement are displayed.
2. A method of measuring distance according to claim 1 wherein step (f) comprises the additional step of generating an indicator signal consisting of one of a general class of sensible signals, characterized by electronic signals, processed electromagnetic signals, visible signals, and audible signals, whereby the detection of said first acoustic pulse signal at said remote transceiver is signalled to an operator at a location removed from said remote transceiver by means of said indicator signal.
3. A method of measuring distance according to claim 1 wherein said first acoustic pulse signal and said second acoustic pulse signal consist of one of the general classes of acoustic waves characterized by sonic wave, infrasonic wave, ultrasonic wave, and shock-wave.
4. A method of measuring distance according to claim 1 wherein said first instantaneous trigger pulse signal and said second instantaneous trigger pulse signal consist of one of the general classes of signals which propagate at the speed of light characterized by a current pulse through a wire (wired means) and electromagnetic pulse (wireless means), whereby a means for instantaneous communication between said controller transceiver and said remote transceiver is provided.
5. A method of measuring distance according to claim 1 wherein the instantaneous veloc-ity of the medium of acoustic transport along the acoustic path between said first location and said second location is optionally displayed in addition to said distance measurements.
6. A method of measuring distance according to claim 5 wherein a plurality of said distance measurements and corresponding instantaneous velocities of the medium of acoustic transport along the acoustic path are stored in a memory for processing.
7. A device for measuring distance between a first location and a second location by means of acoustic pulse signals comprising:
(a) a controller transceiver means and remote transceiver means, each comprising a means for transmitting and receiving acoustic pulse signals, a means for transmitting and receiving instantaneous trigger pulse signals, whereby said controller transceiver and said remote transceiver are operative to simultaneously transmit acoustic pulses between said first location and said second location in opposite directions along the acoustic path, said remote transceiver comprising a means for communicating the receipt of an acoustic pulse at said remote transceiver means lo an operator at said controller transceiver, (b) a means for measuring the times of flight of said acoustic pulse signals travelling in opposite directions along the acoustic path between said first location and said second location, (c) a means for measuring the ambient speed of sound, (d) a means for calculating said distance between said first location and said second location from said times of flight and the ambient speed of sound, whereby random and systematic errors in said times of flight due to the motion of the medium of acoustic transport are cancelled by averaging the said pair of times of flight, (e) means for calculating instantaneous velocity of the medium of acoustic transport between said first location and said second location from said times of flight, a means for displaying said measurements of distance between said first location and said second location and instantaneous velocity of the medium of acoustic transport.
(a) a controller transceiver means and remote transceiver means, each comprising a means for transmitting and receiving acoustic pulse signals, a means for transmitting and receiving instantaneous trigger pulse signals, whereby said controller transceiver and said remote transceiver are operative to simultaneously transmit acoustic pulses between said first location and said second location in opposite directions along the acoustic path, said remote transceiver comprising a means for communicating the receipt of an acoustic pulse at said remote transceiver means lo an operator at said controller transceiver, (b) a means for measuring the times of flight of said acoustic pulse signals travelling in opposite directions along the acoustic path between said first location and said second location, (c) a means for measuring the ambient speed of sound, (d) a means for calculating said distance between said first location and said second location from said times of flight and the ambient speed of sound, whereby random and systematic errors in said times of flight due to the motion of the medium of acoustic transport are cancelled by averaging the said pair of times of flight, (e) means for calculating instantaneous velocity of the medium of acoustic transport between said first location and said second location from said times of flight, a means for displaying said measurements of distance between said first location and said second location and instantaneous velocity of the medium of acoustic transport.
8. A device for measuring distance according to claim 7 wherein a plurality of remote transceivers are positioned at locations defining a coordinate system, whereby the distance between said controller transceiver and each said remote transceiver is measured, whereby the position of said controller transceiver in two and three dimensions is calculated, and the errors due to the motion of the medium of acoustic transport are cancelled.
9. A device for measuring distance according to claim 8 wherein successive distance measurements are obtained at known time intervals, whereby the velocity and acceleration of said controller transceiver are calculated by said calculation means and displayed by said display means.
10. A device for measuring distance according to claim 7 wherein said timer means, said calculation means, said display means, and said memory means are optionally located in a master commander device, said master commander comprising:
(a) means for transmitting instantaneous trigger pulse signals to said controller trans-ceiver and a plurality of said remote transceivers, and means for receiving instantaneous trigger pulse signals from said controller transceiver and a plurality of said remote transceivers, whereby the measurement sequence is controlled by saidmaster commander, (b) timer means for timing the times of flight of the acoustic pulse signals propagating between said controller transceiver and said remote transceiver, said timer means being responsive to said instantaneous trigger pulse signals from said controller transceiver and said plurality of remote transceivers, (c) means for calculating said distances between said controller and each of said plurality of remote transceivers and means for calculating the instantaneous velocity of the medium of acoustic transport from said times of flight measurements, (d) means for storing in a memory a plurality of said distance measurements and corresponding instantaneous velocities of the medium of acoustic transport along the acoustic path.
(a) means for transmitting instantaneous trigger pulse signals to said controller trans-ceiver and a plurality of said remote transceivers, and means for receiving instantaneous trigger pulse signals from said controller transceiver and a plurality of said remote transceivers, whereby the measurement sequence is controlled by saidmaster commander, (b) timer means for timing the times of flight of the acoustic pulse signals propagating between said controller transceiver and said remote transceiver, said timer means being responsive to said instantaneous trigger pulse signals from said controller transceiver and said plurality of remote transceivers, (c) means for calculating said distances between said controller and each of said plurality of remote transceivers and means for calculating the instantaneous velocity of the medium of acoustic transport from said times of flight measurements, (d) means for storing in a memory a plurality of said distance measurements and corresponding instantaneous velocities of the medium of acoustic transport along the acoustic path.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002107198A CA2107198A1 (en) | 1993-09-28 | 1993-09-28 | Method and apparatus for accurate acoustic distance measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002107198A CA2107198A1 (en) | 1993-09-28 | 1993-09-28 | Method and apparatus for accurate acoustic distance measurement |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2107198A1 true CA2107198A1 (en) | 1995-03-29 |
Family
ID=4152374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002107198A Abandoned CA2107198A1 (en) | 1993-09-28 | 1993-09-28 | Method and apparatus for accurate acoustic distance measurement |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2107198A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7176647B2 (en) * | 2003-03-11 | 2007-02-13 | The Chamberlain Group, Inc. | Light-emitting device having a phosphor particle layer with specific thickness |
| WO2014078016A1 (en) * | 2012-11-15 | 2014-05-22 | Qualcomm Incorporated | Echo cancellation using ultrasound |
| IT202000017917A1 (en) * | 2020-07-23 | 2022-01-23 | Taua S R L | ELECTRONIC SYSTEM FOR INTERPERSONAL DISTANCE |
-
1993
- 1993-09-28 CA CA002107198A patent/CA2107198A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7176647B2 (en) * | 2003-03-11 | 2007-02-13 | The Chamberlain Group, Inc. | Light-emitting device having a phosphor particle layer with specific thickness |
| WO2014078016A1 (en) * | 2012-11-15 | 2014-05-22 | Qualcomm Incorporated | Echo cancellation using ultrasound |
| KR20150084814A (en) * | 2012-11-15 | 2015-07-22 | 퀄컴 인코포레이티드 | Echo cancellation using ultrasound |
| US9210270B2 (en) | 2012-11-15 | 2015-12-08 | Qualcomm Incorporated | Echo cancellation for ultrasound |
| KR101651794B1 (en) | 2012-11-15 | 2016-08-26 | 퀄컴 인코포레이티드 | Echo cancellation using ultrasound |
| IT202000017917A1 (en) * | 2020-07-23 | 2022-01-23 | Taua S R L | ELECTRONIC SYSTEM FOR INTERPERSONAL DISTANCE |
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