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
  • 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
  • G01S5/16—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using electromagnetic waves other than radio waves
• • 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
  • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
  • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
  • G01S3/782—Systems for determining direction or deviation from predetermined direction
  • G01S3/783—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived from static detectors or detector systems
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
  • G05D1/02—Control of position or course in two dimensions
  • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
  • G05D1/0231—Control of position or course in two dimensions specially adapted to land vehicles using optical position detecting means
  • G05D1/0234—Control of position or course in two dimensions specially adapted to land vehicles using optical position detecting means using optical markers or beacons
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
  • G05D1/02—Control of position or course in two dimensions
  • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
  • G05D1/0268—Control of position or course in two dimensions specially adapted to land vehicles using internal positioning means
  • G05D1/027—Control of position or course in two dimensions specially adapted to land vehicles using internal positioning means comprising intertial navigation means, e.g. azimuth detector
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
  • G05D1/02—Control of position or course in two dimensions
  • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
  • G05D1/0231—Control of position or course in two dimensions specially adapted to land vehicles using optical position detecting means
  • G05D1/0242—Control of position or course in two dimensions specially adapted to land vehicles using optical position detecting means using non-visible light signals, e.g. IR or UV signals

Definitions

• the present invention relates to automatic vehicle guidance systems.
• Patent GB 2129161B There is a requirement for more flexible systems, and one such system is described in Patent GB 2129161B.
• This Patent describes a flexible system whereby vehicles travel freely under the control of signals generated by computers in response to the detection by one or more fixed cameras of vehicle position, the vehicles being equipped with devices, henceforth referred to as beacons, which transmit a frequency, such as. an infra-red frequency., to which the camera or cameras respond.
• GB Patent -2129161B gives no description of the type of camera involved.
• a co-pending application in the name ofthepresent Applicant describes a camera in the form of a bearing sensing device which provides a large field of view - almost 360° in azimuth and 70° or.more laterally - which is particularly useful for this type of guidance system.
• the bearing sensing device forcusses light from a beacon on to a substantially annular photo detector which has an electrode deposited at each end.
• the photo detector is made from a continuous P-N junction together with a highly uniform resistive sheet.
• a ratiometric converter by which the bearing of a beacon relative to an axis can be determined from the photo detector currents is the subject of another co-pending Application in the name of the present Applicant.
• the ratiometric converter includes means for receiving signals from electrodes at extremities of the annular photo detector, means for processing the signals to separate therefrom components caused by a flash of light focussed on a position of the photo detector, means for distinguishing whether the sum of the components falls within a predetermined range, and, if the sum does fall within the predetermined range, means for processing the components in order to identify the position of the photo detector on which the flash of light is focussed.
• GB Patent 2129161B the control system requires a processing unit to signal a vehicle when it requires knowledge of the vehicle's position.
• a beacon on the vehicle is activated, the activation is detected by the processing unit, and the t rocessing unit calculates the vehicle's position and (with reference to stored information) velocity and signals a vehicle control unit accordingly.
• This system requires very complex equipment if it is to control more than a very small number of vehicles, and is also limited to situations where beacons will always remain within camera view.
• the present invention provides a method and apparatus for using a beacon array in a manner which simplifies control equipment and which allows for non-detection (through beacon failure or from masking of a beacon by, for example, interference between one vehicle and another) of an ' individual beacon.
• T e beacons preferably emit signals in the form of either visible or infrared light and the receivers are preferably cameras.
• the beacons may be at fixed, positions with receivers mounted on vehicles. or vice versa. When the beacons are mounted on the vehicles there are preferably 2 beacons on each vehicle. The difference, between the first and second integrals is preferably one.
• an automatic vehicle guidance system includes a plurality of first devices in the form of signalling units and at lease one second device in the form of a receiving unit, one device or devices being at fixed positions and the other device or devices being mounted on one or more vehicles, the system including means for causing the signal units to sequentially emit signals, intervals between consecutive signals being equal until all signal units have been caused to signal, then after a first pause time of a first integral number of intervals causing the signal units to emit signals in reverse order, and after all the signal units have been caused to signal, after a second pause time of a second number of intervals, repeating the steps, the first and second integrals differing by an odd number.
• the first devices preferably .emit signals "in the form of eithervisible or infrared light and the receivers are preferablycameras.
• the beacons may be at fixedpositions with receivers mounted on vehicles, or vice versa. When the beacons are mounted on the vehicles there are preferably 2 beacons on each vehicle. The differences between the first and second integrals is preferably one.
• Figure 1 shows a vehicle of the type with which the method may be used
• Figure 2(a) and (b) show 2 environments in which the vehicle of Figure 1 can operate;
• Figure 3 and Figure 4 are block diagrams of guidance systems for vehicles operating in the environments of Figure 2(a), Figure 2(b) respectivelyj
• Figure 5(a) is detail of one type of a bearing -sensing device;
• Figure 5(b) is a section through a field of view of the device illustrated in Figure 5(a);
• Figure 6(a) is a detail of a second type of bearing sensing device
• Figure 6(b) is a section through a field of view of the device of Figure 6(a) ;
• Figure 7(a) is a plan view of a photo detector as used in the bearing sensing devices;
• Figure 7(b) shows a potentiometric equivalent circuit for the photo detector of Figure 7(a);
• Figure 8 shows a block diagram of a ratiometric converter for use with the photo detector of Figure 7(a);
• Figure 9 shows an example of beacon timing according to the invention.
• FiguresITUa-) to (d) shows examples of beacon timing which do not identify failed beacons.
• a vehicle with which the invention can be used (Figure 1) has a body 10 mounted on wheels 11 driven and steered according to commands from a control box 12.
• the vehicle 10 can operate in an environment 2(a) in which a bearing sensing device 13, mounted on the vehicle receives signals from a plurality of fixed beacons 14; or in an environment (2(b)) in which beacons 24 (shown indottedlines i Figure1) mounted as far apart as possible on vehicle 10 send signals to fixed bearing sensing- devices 23.
• the control unit 12 When operating in the environment illustrated in 2(a) the control unit 12 will typically contain ( Figure 3) the bearing sensing device 13 which sends signals to transmitter 45 in a control unit 41 and which controls sequential flashing of beacons 24 and operation of a pilot unit 34.
• the ground control units. contain a series of bearing sensing devices 23 each of which sends signals to an associated beacon check 30 and ratiometric converter 31.
• a signal rom the beacon check 30 passes to a master timer 42 which sends signals to each ratiometric converter 31, to a master computer 43 and to a flash timer 44.
• the master computer 43 receives signals from each ratiometric converter 31 and sends command signals to a transmitter 45 which also receives signals from the flash timer 44, and which sends command signals to the receiver 40.
• an ••ultra-wide angle (fish eye) lens 50 directs a beam of light 51 from a beacon 14, 24 through a field stop 52 to a lens 53 which focusses the beam on to an annular photo detector 54.
• a bearing sensing device of this type has a field view ( Figure 5(b)) 55 extending from horizontal to within about 20° of the vertical.
• a beam of light 61 from a beacon 14, 24 passes through a cylindrical window 62 and is reflected by a spherical mirror 60 through a field stop 52 to be focussed by a lens 53 on to an annular photo detector 54.
• the cylindrical window 62 must be robust as well as of good optical quality and it must support the field stop 52, lens 53, and photo detector 54 and associated structure (not shown in this figure) which must be situated above the spherical mirror 60.
• the field of view of this type. of bearing sensing device ( Figure 6(b)) extends from slightly below the horizontal to slightly less than vertical.
• the annular photo detector 54 ( Figure 7(a)) is in the form of an annulus extending over almost 360° and is formed from a continuous P-N junction together with a highly uniform resistance sheet.
• Electrodes 70, 71 are deposited on the ends of the annulus.
• current passes to both electrodes 70 and 71, and by comparing these currents, in a manner analagous to that illustrated in 7(b), the position 72 - - along the annulus can be identified as follows:
• the ratiometric converter 31 ( Figure 8) has a transconductance amplifier 80 with an input from electrode 70 of the photo detector 54 and an output to a differentiating amplifier 81 which has an output to a track and hold amplifer 82. Similarly an output from electrode 71 of photo detector 54 passes through a transducer amplifier 83 and a 0 differentiating amplifier 84 to a track and hold amplifier 85.
• the track and hold amplifiers 82, 85 receive inputs from the timer controller 32 or master timer 42 as well as from the differen ⁇ tiating amplifiers 81, 84, and have outputs to a subtractor 86 and an adder 87. 5
• the adder has an output to an amplitude check 88 which has out ⁇ puts to the timer controller 32 or master timer 42 and to a beacon check 30.
• the adder also has an output to a variable gain amplifier 89 through a first pole 90 of an analogue switch 92, a second pole 91 of which has an input from the subtractor 86.
• the variable gain 89 through a first pole 90 of an analogue switch 92, a second pole 91 of which has an input from the subtractor 86.
• amplifier 89 also receives a signal from a successive approximation register 93 which receives signals from the timer controller 32 or master controller 42 and from a dital comparator 94.
• variable gain amplifier 89 has an output to a 12-BIT fast analogue to digital computer (ADC) 95 which also receives inputs from
• the ADC 95 has outputs to a computer 33 or 43 (not shown) and 98 to the digital comparator 94 which also has a preset binary input 99.
• the beacons 14 sequentially emit flashes of light under the control of the flash timer 15. Each flash has a duration of the order of 10 microseconds ( ⁇ S) .
• the beacons ( Figure 9 shows an example where there are 6 beacons) 14 flash with an identical interval (t ⁇ _) between each pair of
• next beacon is number [N - p/2] If p is odd then next beacon is number [h (p+1)] 10 Note that the details are integer multiples of the delay time between individual flashes.
• This method of timing allows synchronisation between the on ⁇ board timer and the land-based flash timer.
• Figures 10(a) to 10(d) illustrates the inadequacies of other ⁇ -5 timing systems.
• the on-board timer can keep trctck of the beacons by measuring the time at which a flash occurs, but it is essential that it is kept in synchronisation.
• the bearing sensing device 13 on the vehicle 10 senses the f-lash which is focussed onto a point 72 on the annular photo detector 53.
• Electrical currents flowing between the point 72 and electrodes 70, 71 will now be a combination of photo-generated current due to the beacon light, photogenerated current due to background radiation, and thermally generated current.
• the currents due to the beacon light are separated and compared by the ratiometric converter 31, which also rejects light which is, by predetermined criteria, either too intense or too weak.
• the weak criterion may be based, for example, on the expected level of thermally generated current in the photo detector 53 as this is the factor which ultimately limits the minimum signal intensity for acceptable results.
• a typical range in terms of sighting distance is 20:1 corresponding to a range in incident intensity of 400:1 or 52 dB.
• the current pulses from the electrodes 70, 71 are fed into the transductance amplifiers 82, 85 respectively.
• These amplifiers 82, 85 load the contact with a virtual short circuit to ground to provide maximum linearity of response, and also convert the current pulses into proportional voltage pulses.
• These pulses are fed to the differen ⁇ tiating amplifiers 81, 84 respectively.
• the differentiating amplifiers 81, 84 feed signals corresponding to rapidly varying voltage changes (from which current due to background radiation has been filtered) to • the track and hold amplifiers 82, 85 respectively and the signals are held there in response to a signal from the timer controller 32, which has been forewarned by a signal from the bearing sensing device 13 via the beacon check 30, when the voltage pulses are in the peak regions.
• the amplifiers 80, 83; 81, 84 and 82, 85 must be; precisely matched in static and dynamic characteristics.
• the stored voltages from the track and hold amplifiers 82, 85 are fed to the adder 87 and subtractor 86.
• the adder 87 provides a sum signal proportional to the total photoelectric current generated by the beacon 14 flash which is fed to the amplitude check 88. If the amplitude check 88 recognises that the signal from the adder 87 is outside the predetermined maximum and minimum limits it signals the timer controller 32 to discard the beacon 14 flash.
• the sum signal from the adder 64 is also fed to the variable gain amplifier 89 through pole 90 of the analogue switch 92.
• a signal e- j - from the variable gain amplifier 89 is fed to the 12-BIT ADC 95 together with a stable bias signal e B generated by the stable bias generator 96 in response to a signal e from the ADC 95.
• the number. No, which is the binary output 97 of the ADC 95 is:
• This gain adjustment is performed as a 16 step successive approximation .sequence under control of the timer/controller 32, the successive approximation register 93 and the digital comparator 94.
• the comparator 94 compares the output at the ADC with a preset word equal to binary 3600 and provides a keep/reject signal to the success ⁇ ive approximation register 93 indicating whether the ADC 95 output is too high or too_ low.
• the total time required to adjust the gain is approximately sixteen times the conversion time of the ADC. Additional time is allowed for settling of the variable gain amplifier.
• variable gain amplifier 89 The gain of the variable gain amplifier 89 is thus held constant and the analogue switch 92 is changed over so that the difference signal, e D , from the subtractor 86 is fed through pole91 to the amplifier 89.
• binary output number from the ADC 95 is given by:
• the desired current ratio has been evaluated and correctly scaled.
• the correct operation of the ratiometric converter 31 depends on the ability of the variable gain amplifier 89 to adjust its output signal e j to within 0.028% of e B whilst accommodating the 52 dB dynamic range of the sum signal, e s , from the adder 87.
• a two-stage digitally programmable logarithmic amplifier arrangement is used to give the required gain characteristic.
• the timer/controller 32 flags the computer 33 so that the azimuth angle may be stored.
• a beacon identification code is also provided from the beacon check 30 via the timer/controller 32.
• the beacon check 30 operates, for example, in response to a radio or other signal sent by each beacon 14 simultaneously with each flash of light, or, preferably, by the method described in our co-pending Application.
• beacon bearings When 2, or more usually more than 2, beacon bearings are being stored by the computer it calculates the position of the vehicle 10 and signals the pilot unit 34 to make any necessary adjustments to the steering and speed of the vehicle 10. It will be realised that light must not be allowed to fall on the electrodes 70, 71 of the photo detector 53, hence there is a blind spot of, typically 3° in the bearing sensing device 13 and hence there will usually need to be more than 2 beacons 14 taken into consideration when calculating the position of the vehicle 10.
• the lens 50 might be expected to be more accurate than the spherical lens 60, but does tend to be much 20 more expensive.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• General Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Aviation & Aerospace Engineering (AREA)
• Automation & Control Theory (AREA)
• Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)
• Traffic Control Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 1987
  • 1987-09-23 GB GB878722405A patent/GB8722405D0/en active Pending
• 1988
  • 1988-09-19 EP EP88908280A patent/EP0380535A1/en not_active Withdrawn
  • 1988-09-19 AU AU24285/88A patent/AU2428588A/en not_active Abandoned
  • 1988-09-19 WO PCT/GB1988/000769 patent/WO1989003075A1/en not_active Application Discontinuation
  • 1988-09-19 KR KR1019890700896A patent/KR890702098A/ko not_active Application Discontinuation
  • 1988-09-22 PT PT88574A patent/PT88574A/pt not_active Application Discontinuation
  • 1988-09-22 ES ES8802886A patent/ES2012850A6/es not_active Expired - Lifetime
• 1990
  • 1990-03-07 GB GB9005254A patent/GB2234131B/en not_active Expired - Lifetime

Non-Patent Citations (1)

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