GB2186367A

GB2186367A - Ultrasonic position location

Info

Publication number: GB2186367A
Application number: GB08603526A
Authority: GB
Inventors: Eliahu Igal Zeevi
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-12-31
Filing date: 1986-02-13
Publication date: 1987-08-12
Anticipated expiration: 2006-02-13
Also published as: GB2228324A; GB2228324B; GB2186367B; GB8923826D0; GB8603526D0; GB8531952D0

Abstract

Distance measuring apparatus comprising ultrasonic transmission means 4, (5), for transmitting an ultrasonic first signal; transponder means 6 for receiving said signal from said transmission means and for transmitting a further signal in response thereto; receiving means 4, (5), for receiving said further signal; and timing means 3 coupled to said transmission means and to said receiving means and arranged to time the time interval between transmission of said first signal by said transmission means and receipt of said further signal by said receiving means. Hence the distance and/or location of the transponder is derived. The invention is applicable to adjusting the stereo balance of a stereo reproduction system, as a listener 6 changes his position in relation to loudspeakers 1 and 2, in order to maintain the stereo effect. Alternatively to positioning a robot arm relative to a workpiece. <IMAGE>

Description

SPECIFICATION Distance measuring apparatus The present invention relates to distance measuring apparatus and is particularly, but not exclusively, applicable to position location apparatus and it is envisaged that such apparatus may be applied for adjusting the subjective balance, for a listener, between the channels of a stereophonic sound reproduction facility to maintain the desired stereophonic effect as the listener moves aboutthe room or other space served by the facility.

Itisalso envisaged thatthe distance measuring apparatus according tothe invention may be applied to the problem of locating the position of a robot arm in relation to a workpiece or other structural member.

It is well known thatthe spacial illusion created by stereophonic sound reproduction is, for a given balance setting between the channels, effective only over a relatively small zone within the space served bythesystem. For example, wherethe volume settings of two channels of a stereophonic system are equal, the stereophonic effect is obtained only at points equally distance from the speakers.

Consequently, ifthe listener is moving aboutthe room attending to other matters whilst listening to sound reproduced by the system, the stereo effect will be intermittently lost. One object ofthe present invention is to provide means whereby the above mentioned defects may be avoided.

Another object ofthe invention is to provide a simple and acurate means for locating the position of one object with respect to a reference position, for example the position of a robot arm relative to other mechanical components.

According to one aspect ofthe invention, there is provided distance measuring apparatus characterised by: ultrasonic transmission means for transmitting an ultrasonic first signal; transponder means for receiving said signal from said transmission means and fortransmitting afurther signal in response thereto; receiving means for receiving saidfurthersignal; and timing means coupled to said transmission means and to said receiving means and arranged to timethetime interval between transmission of said first signal by said transmission means and receipt of said further signal by said receiving means.

Preferably, the transponder means is arranged to transmit an ultrasonic signal as said further signal.

Such ultrasonic signal is preferably of a different frequencyfromtheultrasonicfirstsignal. It is also conceivable however that the transponder means could transmit an infra-red or radio signal as said further signal, or anothertype of electrical signal, e.g. on a wire.

Preferably, the receiving means is positioned at the same location as said transmission means. It is also conceivable howeverthatthe receiving means may be positioned elsewhere, for example at a central control unit.

In one embodiment, the ultrasonictransmission means includesfirstand second transmitters arranged at spaced reference locations to transmit respective ultrasonic signals, said transponder means being atan unknown location and responsive to both of the ultrasonic signals, and said timing means being arranged to measure respective timingsforsaid ultrasonic signals.

Preferably, the first and second transmitters are arranged to transmit at mutually differing frequencies. This permits the first and second transmitters to transmit simultaneously without mutual interference.

In an alternative embodiment, the first and second transmitters are arranged to transmit at mutually differing times. This embodimentenablesthefirst and second transmitters to utilize the same frequency without mutual interference.

Thus, time division multiplex of frequency division multiplex systems may be employed.

In an alternative embodiment, said transponder rneansincludesfirstandsecondtranspondersat spaced reference locations which are arranged to transmit respective further signals in response to respective transmissions from said transmission means at an unknown location, said timing means being arranged to measure respective time intervals for said further signals.

The transmission means may be arranged to transmit at mutually different frequencies for respective transponders, or may be arranged to transmit at mutually differing times four respective transponders. In either case, interference between the transmissions for respective transponders is avoided in a simple manner.

The first and second transponders may be arranged to transmit respective further signals at mutually different frequencies.

In order to obtain positional data in respect ofthe unknown location from said time intervals, computing means may be coupled to said timing means.

The space reference locations may be fixed relative to a pair of loud speakers, and said computing means may be arranged tofurther compute a control signal based on said positional data, control means being provided for controlling the power supply to said speakers in responseto said control signal in a manner such asto equalise the audio intensity from respective loud speakers at said unknown location.

Expediently, the reference locations are within respective housings of said loud speakers.

According to a further aspect of the invention, there is provided position location apparatus for determining the position of an object, characterised by: first and second ultrasonictransmission means at respective spaced reference locations; transponder means for mounting on said objectfor receiving first and second signals from respective transmission means and fortransmitting respective first and second further signals in responsethereto; receiving means for receiving said further signal; timing means coupled to said first and second transmission means and to said receiving means and arranged to time a first interval between transmission of said first signal and receipt of said firstfurthersignal and a second time interval between transmission of said second signal and receipt of said second further signal; and computing means coupled to said timing means and arranged to compute positional data of said object from said time intervals.

According to another aspect of the invention there is provided means whereby the subjective balance, for a listener, between the channels of a stereophonic sound reproduction facility, or among the channels of a multi-phonic, e.g. guadraphonic sound reproduction facility may be maintained as the listener moves around a space in which the loud speakers ofthefacility are disposed, said means comprising a device adapted to be carried by the listener and capable of transmitting signalsto receiving means fixed with respect to said speakers, said receiving means being arranged to determine, from the signal received, the position of the device, and thus of a listenercarrying the device, in said space and to vary the respective volumes of sound reproduction from said channels accordingly.

Alternatively, the receiving means is arranged to compute onlythe relative distances ofthe device from respective loud speakers, their being provided a respective receiving means for each loud speaker.

In a preferred embodiment ofthe invention,the device adopted to be carried by the listenertakesthe form of a small unitwhich may be carried inthe listener's pocket or strapped to his wrist afterthe fashion of a wrist watch, or clipped to his clothing.

The device may be arranged,for example, to emit, at short intervals, low-intensity, radio signals which are picked up by receivers mounted close to the respective loud speakers for the respective channels.

A central control facility may then process the signals received by the respective receivers to determine, on the basis, for example, of the relative intensities of radio signals received, and/orthetime lapse between the receipt of any signal by the two receivers or by a corresponding phase difference or the like, the relative distance from the transmitting device to the two receivers, the control facility being arranged, on this basis, to adjustthe balance between the channels to maintain the subjective balance as judged by the listener.

In another arrangement, the speakers of the two channels may have respective transmitters associated therewith, arranged to transmit signals to the device carried by the listener, and the latter device may bearranged to comparethesignals received from the two transmitters and to transmit corresponding data to the central control facility which on the basis determines the position or relative distances of the listener and adjuststha balance accordingly.

Instead ofthe signals utilized being radio signals, the signals used may be infa-red or ultra-sonic signals (subject, or course, to the respective ultra-sonic frequency being chosen so as to avoid interference bythe reproduced sound material).

Preferably, the ultra-sonicfrequency is in the range of 50-100 kHz.

While certain aspects of the invention have been described by reference to a stereophonic system, it will be appreciated that the balance adjusting system described may be used in conjunction with a system utilizing more than two channels, for example in relation to a quadrophonic system which utilizes for separatechannelsforsound reproduction.

Four a better understanding of the invention, and to show howthe same may be carried into effect, reference will now be made by way of example to the accompanying drawing, in which: Figure lisa schematic block diagram of position locating apparatus according to one embodiment of the present invention; Figure 2 is a block circuit diagram of a transponder; and Figure 3 is a block circuit diagram of a transmitting and receiving circuit with associated control circuitry.

Referring first of all to Figure 1, there are illustrated schematically first and second loud speakers 1 and 2 coupled to a central control unit3 of a stereophonic reproduction system. Associated with the respective loud speakers, are distance measuring devices 4 and 5. The devices 4 and 5 may be located within the respective speaker housings, or may be mounted in separate units attached to respective speakers. A transponder unit 6 is adapted to be carried by a listener and takes the form of a small unitwhich may be carried in the listener's pocket or strapped to his wrist after the fashion of a wrist watch, or clipped to his clothing.

Within the control unit 3, is provided processing and control circuitry for deriving control signals from the outputs of respective units 4 and 5 for controlling the powersupplied buy a stereo amplifier also contained within the unit 3 to respective speakers 1 and 2.

In outline, the measuring and adjusting process takes place inthree stages. First of ali, the distance of the unit6fromthe stationary units4 and 5 is measured, secondly the effect of these distances on the stereo balance is computed, and thirdly the balance is adjusted in accordance with the computed result.

The transmitters and receivers of the system illustrated in Figure 1 operate using ultrasonic frequencies, preferably in the range of 50 - kHz.

To avoid environmental problems, it is preferably thatthefrequency is above the audible range of any pets likely to be in the vicinity, such as dogs. The system works most effectively when the walls of the room in which it is contained are reasonably non-reflecting. Most domestic living rooms containing curtains, carpets etc. will satisfactorily meet this requirement.

It is preferred that the transmitters associated with units 4 and Shave a directional characteristic such thattheytransmitovera rangeofanglelessthan 180 . On the other hand, the transmitter and receiver contained in unit6should beomni-directional.

Referring now to Figure 2, block7 represents an ultrasonic receiver, block 8 a control unit, and block9 a transmitter, which may be an ultrasonic transmitter. The system operates such that when an ultrasonic signal is received by receiver7 it is detected by control circuit8 and in response to this detection the transmitter 9 is operated to transmit an acknowledgement signal. This signal may either be an ultrasonic signal or a radio signal or an infra-red signal, or any electrical signal. If it is an ultrasonic signal, it is preferably intended for receipt by the units 4 and 5. On the other hand, if it is a radio or infa-red signal, it may be transmitted directly to the main control units 3 which will then be provided with suitable receiving means.The signal may also be transmitted via a wire to the central control unit, although the use of a wire is obstructive and should be avoided if possible.

Figure 3 is a block schematic diagram ofthe circuitry contained within unit 4 or 5. The illustrated embodiment is for use when the transmitterS ofthe transponder transmits ultrasonic signals.

Figure 3 illustrates an ultrasonictransmitter 10, a frequencytransmittercontrol circuit 12, a receiver 11, a receiver interface 13, a timer circuit 14, a distance computing circuit 15, and a power compensation circuit 16 which provides an output signal at a terminal 17.

It will be apparent that the frequency transmitter control circuit 12 operates to cause the transmitter 10 to transmit an ultrasonic signal and simultaneously starts timing by the timer circuit 14. The transmitted signal is received by the receiver7 of the transponder illustrated in Figure 2 and in response to this signal the transponder causes the transpondertransmitter 9 to transmit a response signal. This response signal is received by the receiver 11 and decoded by the receiver interface 13 to produce a timer stopping signal. Data representing the resulting the timed interval is supplied to the distance computing circuit 15from the timer 14.On the basis ofthetimed interval andthe known velocity ofsound in air(331.7 metres per second) the computing circuit 15 derives a measure of the distance travelled by the two ultrasonicsignals. This distance is ofcoursetwice the distance between the loud speaker unit 4 or 5 and thetransponder unit 6. From this distancevalue,the powercompensation circuit 16 is ableto compute a measure ofthe sound intensityatthe position ofthe transponder 6 caused by the loud speaker associated with the relevant unit4or5. Similar measurement and computation process may be effected for each loud speaker 1 and 2 and associated unit 4 and 5.

From the resulting information, bearing in mind that received sound intensity fal Is off as the cu be of the distance, an appropriate adjustment may be made by a control device contained within the unit3tothe stereo balance to ensure that substantially equal sound intensities are present at the unit 6 from respective speakers 1 and 2. This ensures that the stereo effect is maintained irrespective ofthe position of the unit 6. It will be noted that the position ofthe unit 6 may also be determined from the distance information, since it is located atthe intersection of two circular arcs centred at respective units 4 and 5 of radius equal to the computed distance.It is true that this information gives two possible positionsforthe unit 6, but one ofthese positions is excluded in the normal case since the loud speakers are usually mounted adjacent a wall.

However, it is not actually necessary to compute the coordinates ofthe unit 6 in orderto correctly adjust the stereo balance.

In the preferred embodiment discussed above, it has been mentioned thatthe response signal transmitted by transmitter 9 could also be an infa-red or radio signal. In this case, the time interval timed by the timer 14would only be a "one way" traverse from unit4to unit6 bythe ultrasonic signal. This thus somewhat reduces the measurement accuracy.

Since there are two separate loud speakers, it is clearly necessary to provide some means for distinguishing the signalsfrom unjt Sfrom those from unit 4. This may be achieved in one of at least two ways. In a first method, unit4 and unit 5 operate in differing frequency ranges. In this case, the transponder in unit 6 must be capable of receiving and transmitting in two separate frequency bands. In a second method, signals from units4and 5 are time multiplexed underthe control of unit 3 and in this case the transponder need only receive and transmit on a single frequency or in a single frequency band.

This reduces the complexity ofthe transponder, but of course correspondingly increase the complexity ofthecontrol unit 3.

It is in any case preferred that the transponder transmitter 9 transmits on a different frequency from thatofthetransmitter10in ordertoavoid ambiguous readings possibly caused bywall reflections.

As an alternative embodiment, it is possible to placethetransponderin each ofthe units 4 and 5 and to replacethetransponderin unit 6 by a transmitter and receiver. This system however would require some means oftransmitting data indicating instance of transmission and reception from the unit 6 to the main control unit 3. This could be achieved by means of a wire or by means of a wireless link. However,the added complexity makes this alternative less attractive.

Another alternative wou Id be to provide a simple transmitter in unit 6 and transponders in units 4and 5. Whilst the time of receipt could readily be transmitted to unit3 in such an embodiment,the difficulty is again presented that a wire orwireless link is required to transmit data indicating the instant of transmission from unit 6to main control unit3.

It remains to be described howthe adjustment of the stereo balance is effected in response to the output signal 17. This may be achieved either by direct electronic control using, for example a variable resistor connected in the loud speaker volume control circuitry, or alternatively by using a mechanical system which mechanically rotates a balance control spindle whose rotation effects a necessary change in the stereo balance.

Itwill be appreciated that when units 4 and 5 are built into the housings of respective speakers 1 and 4 all necessary control and data lines may be conducted within a common speaker cable, preferably the same cable utilized for supplying the audio signalstothe speaker.

Control ofthe system may be effected either by dedicated electronic control logic circuits, or by means of a micro processor in conjunction with an appropriate program stored in a ready only memory.

Many modifications will occur two those skilled in the art and it is intended that all such modifications are included within the scope of the present invention as defined by the appended claims.

For example, one position of a robot arm may be determined by using similar techniques. The transponder 6 can be carried by the arm and positionally located relative to respective transmitter/receiver units 4 and 5 fixed relative to a workpiece or structural member of the robot.

Claims

1. Distance measuring apparatus characterised by ultrasonic transmission means fortransmitting an ultrasonicfirst signal; transponder means for receiving said signal from said transmission means and for transmitting a further signal in response thereto; receiving means for receiving said further signal; and timing means coupled to said transmission means and to said receiving means and arranged to time the time interval between transmission of said first signal by said transmission means and receiptofsaidfurthersignal bysaid receiving means.

2. Apparatus according to Claim 1 wherein said transponder means is arranged to transmit an ultrasonic signal as said furthersignal.

3. Apparatus according to Claim 2 wherein said transponder means is arranged to transmit said further signal at a frequency differing from that of said first signal.

4. Apparatus according to Claim 1,2 or 3 wherein said receiving means is positioned atthe same location as said transmission means.

5. Apparatus according to any one of Claims 1 to 4wherein said ultrasonic transmission means includes first and second transmitters at spaced reference locations and arranged to transmit respective ultrasonic signals, said transponder means being atan unknown location and responsive to both ultrasonicsignals, andsaidtiming means being arranged to measure respective time intervals for said ultrasonic signals.

6. Apparatus according to Claim 5 wherein said first and second transmitters are arranged to transmit at mutually differing frequencies.

7. Apparatus according to Claim 5 wherein said first and second transmitters are arranged to transmit at mutually different times.

8. Apparatus according to any one of Claims 1 to 4wherein said transponder means includes first and second transponders at spaced reference locations and arranged to transmit respective further signals in response to respective transmissions from said transmission means at an unknown location, said timing means being arranged to measure respective time intervals for said further signals.

9. Apparatus according to Claim 8 wherein said transmission means is arranged to transmit at mutually differentfrequenciesfor respective transponders.

10. Apparatus according to Claim 8 wherein said transmission means is arranged to transmit at mutually differing times for respective transponders.

11. Apparatus according to Claim 8when dependent on Claim 2 or3wherein said transponders are arranged to transmit respective further signals at mutually different frequencies.

12. Apparatus according to any one of Claims 5 toll wherein computing means is coupled to said timing means and is arranged to compute position data respecting said unknown location from said time intervals.

13. Apparatus according to Claim 12wherein said spaced reference locations are fixed relative to a pair of loud speakers, said computing means being arranged to further compute a control signal based on said positional data, and control means being provided for controlling the power supplied to said speakers in response to said control signal in a manner such asto equalize the audio intensities from respective loud speakers at said unknown location.

14. Apparatus according to Claim 13wherein said reference locations are within respective housings of said loudspeakers.

15. Position location apparatus for determining the position of an object characterised by: first and second ultrasonic transmission means at respective spaced reference locations; transponder means on said object for receiving first and second signals from respective transmission means and for transmitting respective first and second further signals in response thereto; receiving means for receiving said further signals; timing means coupled to said first and second transmission means and to said receiving means and arranged to time a first interval between transmission of said first signal and receipt of said first further signal and a second time interval between transmission of said second signal and receipt of said second further signal; and computing means coupled to said timing means and arranged to compute positional data of said object from said time intervals.

16. Distance measuring apparatus substantially as hereinbefore described with reference to the accompanying drawing.

17. Position location apparatus substantially as hereinbefore described with reference to the accompanying drawing.

18. Means whereby the subjective balance, for a listener, between the channels of a stereophonic sound reproduction facility, or among the channels of a multi-phonic, e.g. quadrophonicsound reproduction facility, may be maintained as the listener moves around a space in which the loud speakers of the facility are disposed, said means comprising a device adapted to be carried by the listener and capable of transmitting signals to receiving means fixed with respect to said speakers, said receiving means being arranged to determine, from the signals received, the position of the device, and thus of the listener carrying the device, in said space and to vary the respective volumes of sound reproduction from said channels accordingly.

19. Means according to Claim 18 wherein said device is arranged to receive signals from transmitters associated with the respective loud speakers and to relay corresponding signals to said receiving means.

20. Means according to Claim 18 or Claim 19 wherein said signals are ultrasonic signals.

21. Means according to Claim 18 or Claim 19 wherein said signals are light signals or infa-red signals.

22. Means according to Claim 180rClaim 19 wherein said signals are radio signals.

23. Any novel feature or combination offeatures of the distance measuring or position location apparatusorstereo-balancing means hereinbefore described.

24. Stereo balance adjusting means substantially as hereinbefore described with reference to the accompanying drawing.