VEHICLE LOCATION MONITORING SYSTEM

• US 3,789,198 A
• Filed: 04/10/1972
• Issued: 01/29/1974
• Est. Priority Date: 04/10/1972
• Status: Expired due to Term

• Current Assignee: Alfred J. Henson, Richard W. Lewis
• Original Assignee: Alfred J. Henson, Richard W. Lewis
• Inventors: Henson, Alfred J., Lewis, Richard W.
• Primary Examiner(s): Gruber, Felix D.
• Assistant Examiner(s): Dildine, Jr., R. Stephen
• Application Number:
  US05/242,349
• Time in Patent Office: 659 Days
• Field of Search: 73/178R,490,505,509,510 116/35R,37,124R 235/61NN,61S,61V,61.5S,150.2,150.27 340/24 444/1
• US Class Current: 701/446
• CPC Class Codes: G01C 21/30 Map- or contour-matching
• CPC Class Codes: G08G 1/13 the indicator being in the form of a map

Abstract

After a discussion of prior systems for indicating at a central location the instantaneous location of one or more vehicles, such as police cars or taxi cabs, an improved system of this type is described which uses the principles of dead reckoning. The improved system includes a distance sensor, such as a counter storing revolutions of the vehicle'"'"''"'"'s odometer, and a heading sensor, such as a magnetic compass, which are located in a vehicle. A time-multiplex communications system provides for transmission of changes in distance and heading to a central location at periodic intervals. The location of each vehicle is stored in a computer, starting with an initial known position, and periodically updated thereby using the transmitted distance change and heading change information. If desired, the stored vehicle locations may be transmitted to a display unit. To compensate for accumulated errors customary in dead reckoning systems, the computer also periodically compares the stored location of each vehicle against an internally stored matrix corresponding to the known streets, roadways and alleyway of the area. If the vehicle location and road location do not match, the vehicle location is updated to correspond to the nearest street.

Claims

1. An apparatus for continuously monitoring the location of a vehicle within a predetermined area, including:

a. a distance sensor providing an output signal for every predetermined increment of vehicle travel, b. a heading sensor providing an output signal proportional to vehicle heading, c. a first storage means containing the coordinates of the vehicle'"'"''"'"'s last-known location in the area, d. means for periodically computing new vehicle location coordinates from the output signals of said distance and heading sensors and the last-known location coordinate contained in said first storage means and means for replacing the last-known coordinates in said first storage means with said new vehicle location coordinates, e. a second storage means containing the coordinates of drivable surfaces in the area, f. comparator means connected to said first and second storage means for comparing the coordinates contained in said first and second storage means and for providing an output signal if the coordinates in said first storage means do not correspond to any in said second storage means, and g. an update means responsive to the output signal of said comparator means to change the coordinates in said first storage means to correspond with those in said second storage means of the nearest drivable surface.

2. An apparatus as recited in claim 1, further including a display means for displaying the vehicle location coordinates in said first storage means.

3. An apparatus as recited in claim 1, wherein the vehicle includes a rotational mechanism which rotates in response to vehicle travel, and wherein said distance sensor further comprises a revolution detector providing an output pulse for every predetermined increment rotation of said rotational mechanism and means converting said output pulses into said output signal.

4. An apparatus as recited in claim 1, wherein said heading sensor includes a magnetic compass located in said vehicle.

5. An apparatus as recited in claim 1, wherein said distance and said heading sensors are located within said vehicle, and wherein said first and second storage means, said computing means, said comparator means, and said update means are located at a central station, further including a communications means for transmitting the output signals from said distance and heading sensors to said central station.

6. An apparatus as recited in claim 5, further including a digital computer located at said central station which is controlled by a stored program to provide the operations of said first and second storage means, said computing means, said comparator means, and said update means.

7. An apparatus as recited in claim 5, further including a display means located at said central station for displaying the vehicle location coordinates in said first storage means.

8. A method for continuously monitoring the location of a drivable vehicle within a predetermined geographical area, comprising the steps of:

a. storing a last-known location for the vehicle in terms of coordinates Xold, Yold, b. measuring an incremental distance Delta D travelled by the vehicle from the last-known location, c. measuring the heading angle of the vehicle as it travels the distance Delta D, d. periodically computing a new location for the vehicle in terms of coordinates Xnew, Ynew according to the relations Xnew Xold + Delta D(cos(heading)) and Ynew Yold + Delta D(sin(heading)), and storing coordinates Xnew, Ynew as coordinates Xold, Yold, e. comparing the coordinates Xold, Yold with a table of coordinates Xst, Yst corresponding to the drivable surfaces in the area, f. if Xold, Yold do not correspond to any coordinates Xst, Yst in the table, searching the table to find the coordinates Xst , Yst which are nearest to Xold, Yold, and g. storing coordinates Xst , Yst as coordinates Xold, Yold.

9. A method as recited in claim 8, wherein said table is searched in a direction perpendicular to the last-measured vehicle heading.

10. A method as recited in claim 8, wherein steps (e)-(g) are repeated at periodic intervals.

11. A vehicle location monitoring system for determining at a central station the locations of a plurality of vehicles within a predetermined area, comprising:

a. a plurality of mobile units, each mobile unit being contained in one of the vehicles and each including a distance sensor providing an output signal for every predetermined increment of vehicle travel, and a heading sensor providing an output signal proportional to vehicle heading, b. a multiplexed communications system providing transmission of the distance sensor and heading sensor output signals from each of said mobile units to the central station, c. at the central station, means temporarily storing said distance and heading sensor output signals from said plurality of mobile units, a first means for storing a last-known location for each of said vehicles, means periodically computing a new location for each of said vehicles and storing the new locations in said first storage means, said computing means utilizing the locations previously stored in said first storage means and said distance and heading sensor output signals, second means for storing the locations of drivable surfaces in the area, means for comparing the location of each vehicle in said first storage means with the locations of drivable surfaces in said second storage means, and providing an output when the location of any vehicle does not correspond to a location in said second storage means, and updating means responsive to said output for changing the vehicle in said first storage means to the location of the nearest drivable surface in said second storage means.

12. A vehicle location monitoring as recited in claim 11, further including a display means at the central station which is interconnected with said first storage means for selectively displaying the locations of said plurality of vehicles.

13. A vehicle location monitoring system as recited in claim 11, wherein said multiplexed communications system includes, at the central station, a master clock providing a plurality of clock pulses, means coupled to said master clock for periodically providing a synchronization pulse to establish a reporting cycle, means transmitting said synchronization pulse to said plurality of mobile units and a demultiplexing means having said clock pulses and synchronization pulses applied thereto for establishing a plurality of successive reporting intervals during each reporting cycle to recognize the distance and heading output signals of each of said mobile units;

at each of said mobile units, a multiplexing means responsive to said synchronization pulse for transmitting said distance and heading output signals to the cental station during a reporting interval assigned to the mobile unit.

14. A vehicle location monitoring system as recited in claim 13, wherein said clock pulses are supplied to said computing means so that a new location is computed for each of said vehicles once each reporting cycle.

15. A vehicle location monitoring system as recited in claim 11, further including a digital computer operating under control of a stored program to provide the operation of said first and second storage means, said computing means, said comparing means and said updating means.

16. A vehicle location monitoring system as recited in claim 15, wherein said digital computer includes a memory array functioning as said second storage means, said memory array having a plurality of positions, each position being assigned a coordinate location referenced to said area, and a plurality of data bits stored in said memory array, a data bit being contained in one of said positions only if said assigned coordinate location of said position coincides with the coordinate location of a drivable surface in the area.

17. A vehicle location monitoring system as recited in claim 16, wherein said updating means includes means searching the positions of said memory array adjacent a position having an assigned coordinate location corresponding to said last-known location stored in said first storage means for each of said vehicles, and means responsive to the detection of a data bit in one of said adjacent positions to change said last-known location in said first storage means to correspond with said coordinate location adjacent said position in said memory array.

18. A vehicle location monitoring system as recited in claim 17, wherein said searching means searches the positions in said memory array which are located perpendicular to tHe vehicle'"'"''"'"'s heading stored in said temporary storage means.