Control target surveillance system

• US 5,677,841 A
• Filed: 03/09/1995
• Issued: 10/14/1997
• Est. Priority Date: 03/11/1994
• Status: Expired due to Fees

• Current Assignee: Electronic Navigation Research Institute, Independent Administrative Institution, Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Director-General Ship Research Institute Ministry of Transport, Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Nagano, Suketoshi, Oka, Masataka, Shiomi, Kakuichi
• Primary Examiner(s): Trans, Vincent N.
• Application Number:
  US08/401,270
• Time in Patent Office: 950 Days
• Field of Search: 364/461, 364/439, 364/436, 364/443, 364/460, 364/449.1, 364/449.7
• US Class Current: 701/120
• CPC Class Codes: G01S 1/24 the synchronised signals being pulses or equivalent modulations on carrier waves and the transit times being compared by measuring the difference in arrival time of a significant part of the modulations , e.g. LORAN systems
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

A control target surveillance system capable of acquiring positional data of a control target in a control zone at high precision with fewer communications lines in a short period of time. A D. GPS ground station obtains differential data with respect to positional data based on a GPS signal from a GPS satellite, and sends this data to a control target to compensate the positional data obtained from the GPS signal. A surveillance cycle is time-divided by the number of SSR codes, individual time slots are associated with the SSR codes, and each control target is allowed.

Claims

1. A control target surveillance system for allowing a control equipment to monitor positions of a plurality of control targets in a control zone, said system comprising:

time adjusting means for making times, managed by said plurality of control targets and said control equipment, coincide with one another;

positional data obtaining means, installed on each of said control targets, for obtaining at least local positional data using a satellite navigation system;

positional data transmitting means, installed on each of said control targets and being managed with times adjusted by said time adjusting means, for transmitting said positional data, obtained by said positional data obtaining means, to said control equipment via a specific communications line within a period of a time slot corresponding to an identification code previously affixed;

positional data receiving means, provided at said control equipment, for receiving positional data sent from each control target via said communications line;

control target discriminating means, provided at said control equipment and being managed with times adjusted by said time adjusting means, for, with regard to each positional data received at said positional data receiving means, obtaining a corresponding identification code from a time slot of a reception time of said positional data to thereby discriminate the control target which has sent said positional data; and

display means, provided at said control equipment, for displaying positions based on said received data and a result of said control target discrimination every given surveillance cycle,

whereby said surveillance cycle is time-divided by at least a plurality of previously prepared identification codes to determine time slots corresponding to said identification codes, and said identification codes are previously given to said plurality of control targets in such a way as not to overlap one another to thereby assign said time slots to said control targets.

2. The control target surveillance system according to claim 1, wherein said time adjusting means performs time adjustment based on times managed by a navigation satellite used by said satellite navigation system.

3. The control target surveillance system according to claim 1, further comprising a ground station having differential data generating means for obtaining positional data at a known position in said control zone based on satellite information from a same navigation satellite as used by said satellite navigation system of said control target and comparing said positional data with known positional data to calculate differential data, and differential data transmitting means for transmitting said differential data obtained by said differential data generating means to said plurality of control targets;

and wherein

said plurality of control targets are each equipped with differential data receiving means for receiving said differential data; and

said position data obtaining means has a function for compensating positional data obtained using said satellite navigation system, based on said differential data.

4. The control target surveillance system according to claim 3, wherein said differential data transmitting means of said ground station transmits differential data via a line which permits said satellite navigation system installed in each of said plurality of control targets to receive data.

5. The control target surveillance system according to claim 3, wherein said differential data transmitting means time-divides said surveillance cycle by a number equal to or greater than a number of identification codes to secure a time slot for transmission of differential data and transmits differential data via a communications line for communication of said positional data in a period of said time slot.

6. The control target surveillance system according to claim 1, further comprising a ground station having differential data generating means for obtaining positional data at a known position in said control zone based on satellite information from a same navigation satellite as used by said satellite navigation system of said control target and comparing said positional data with known positional data to calculate differential data;

said control target discriminating means of said control equipment has a function for compensating positional data of a control target received by said position data receiving means, based on said differential data obtained by said differential data generating means.

7. A control target surveillance system for allowing a control equipment to monitor positions of a plurality of control targets in a control zone, said system comprising:

time adjusting means for making times, managed by said plurality of control targets and said control equipment, coincide with one another;

positional data obtaining means, installed on each of said control targets, for obtaining at least local positional data using a satellite navigation system;

time slot discriminating means which is given a grid data file showing a correlation between positions of grid points in a coordinate system, obtained by previously segmenting said control zone in a mesh form in an arbitrary pattern, and time slots, and refers to said grid data file to obtain a time slot of a grid point corresponding to said positional data;

identification code transmitting means, being managed with times adjusted by said time adjusting means, for transmitting previously given identification codes to said control equipment via a specific communications line within a period of said time slot obtained by said time slot discriminating means;

identification code receiving means, provided at said control equipment, for receiving an identification code sent from each control target via said communications line;

control target discriminating means, provided at said control equipment, for discriminating of a type of a sender control target;

positional data discriminating means for obtaining, from a time slot corresponding to a reception time of said received identification code, a position of an associated grid point in said coordinate system, and outputting said position as positional data of said control target whose type has been discriminated; and

display means, provided at said control equipment, for displaying positions based on said received data and a result of said control target discrimination every given surveillance cycle,

whereby each grid point in said coordinate system is expressed by a first axis and a second axis, said surveillance cycle is time-divided to at least first and second transmission stages, said first transmission stage is time-divided by a number of first axis grid points in said coordinate system so as to associate individual time slots with said first axis grid points, said second transmission stage is time-divided by a number of second axis grid points in said coordinate system so as to associate individual time slots with said second axis grid points, identification codes are given to said plurality of control targets in a non-overlapping manner, and each identification code is transmitted in a time slot corresponding to associated first axis and second axis grid points.

8. The control target surveillance system according to claim 7, wherein said time adjusting means performs time adjustment based on times managed by a navigation satellite used by said satellite navigation system.

9. The control target surveillance system according to claim 7, further comprising a ground station having differential data generating means for performing a positioning operation at a known position in said control zone based on satellite information from a same navigation satellite as used by said satellite navigation system of said control target and comparing said positional data with known positional data to calculate differential data, and differential data transmitting means for transmitting said differential data obtained by said differential data generating means to said plurality of control targets;

and wherein

said plurality of control targets are each equipped with differential data receiving means for receiving said differential data; and

said position data obtaining means has a function for compensating positional data based on said differential data.

10. The control target surveillance system according to claim 9, wherein said differential data transmitting means secures a time slot for transmission of differential data in said surveillance cycle and transmits differential data via a communications line for communication of said positional data in a period of said time slot.

11. The control target surveillance system according to claim 9, wherein said differential data transmitting means of said ground station transmits differential data via a line which permits said satellite navigation system installed in each of said plurality of control targets to receive data.

12. The control target surveillance system according to claim 7, wherein said grid points in said coordinate system are arranged densely in a portion where concentration of control targets is expected and are arranged sparsely in other portions.

13. The control target surveillance system according to claim 7, wherein SSR codes are used as said identification codes.

14. The control target surveillance system according to claim 7, wherein Mode-S addresses are used as said identification codes.

15. A control target surveillance system for allowing a control equipment to monitor positions of a plurality of control targets in a control zone, giving one of a plurality of previously prepared identification codes for all of said plurality of control targets, time-dividing a surveillance cycle by at least a number of said identification codes while managing said surveillance cycle with a reference time and assigning said plurality of identification codes to mutually different time slots, said system comprising:

on-target subsystems, installed on said control targets, and each having time managing means for acquiring information of said reference time to manage a time based on said reference time, and pulse signal transmitting means for discriminating a start timing of a time slot to which a local identification code is assigned, from said time managed based on said reference time, and sending a pulse signal of a predetermined frequency at said start timing;

a plurality of slave stations, located at different known positions in said control zone, and having pulse signal receiving means for receiving pulse signals sent from said plurality of control targets, time managing means for acquiring said information of said reference time to manage a time based on said reference time, time measuring means for measuring a time from said start timing of each time slot to a reception timing of said pulse signal and measured time outputting means for outputting a measured time, obtained by said time measuring means, to said control equipment;

a master station, located at a known position different from those of said plurality of slave stations in said control zone, and having pulse signal receiving means for receiving pulse signals sent from said plurality of control targets, time managing means for acquiring said information of said reference time to manage a time based on said reference time, time measuring means for measuring a time from said start timing of each time slot to a reception timing of said pulse signal and measured time inputting means for receiving measured time information from said plurality of slave stations, and position calculating means for obtaining a time difference between individual measured times from said plurality of slave stations and a local measured time, obtaining a hyperbolic function indicating a locus showing said time differences between said slave stations and calculating a position of an intersection of at least two hyperbolas; and

a surveillance subsystem, provided in said control equipment, for obtaining a position of an intersection of hyperbolas obtained by said master station as positional information of a control target as a sender every said surveillance cycle, detecting an identification code from a time slot for which a reception event has occurred to find a type of an associated control target, and performing a display process.

16. The control target surveillance system according to claim 15, wherein said time measuring means of said plurality of slave stations and said master station start counters at start timings of respective time slots and stopping said counters at a pulse signal reception timing to measure times.

17. The control target surveillance system according to claim 15, wherein said time managing means provided in said on-target subsystems, said plurality of slave stations and said master station perform time adjustment based on times managed by a navigation satellite used by said satellite navigation system.

21. The control target surveillance system according to claim 15 or 18, wherein said identification codes are SSR codes.

18. A control target surveillance system for allowing a control equipment to monitor positions of a plurality of control targets in a control zone, giving one of a plurality of previously prepared identification codes for all of said plurality of control targets, time-dividing a surveillance cycle by at least a number of said identification codes while managing said surveillance cycle with a reference time and assigning said plurality of identification codes to mutually different time slots, said system comprising:

on-target subsystems, installed on said control targets, and each having time managing means for acquiring information of said reference time to manage a time based on said reference time, and pulse signal transmitting means for discriminating a start timing of a time slot to which a local identification code is assigned, from said time managed based on said reference time, and sending a pulse signal of a predetermined frequency at said start timing;

a plurality of slave stations, located at different known positions in said control zone, and having pulse signal receiving means for receiving pulse signals sent from said plurality of control targets, and pulse signal transmitting means for immediately transmitting said pulse signal received by said pulse signal receiving means;

a master station, located at a known position different from those of said plurality of slave stations in said control zone, and having pulse signal receiving means for receiving pulse signals sent from said plurality of control targets, time managing means for acquiring said information of said reference time to manage a time based on said reference time, first time measuring means for measuring a time from said start timing of each time slot to a reception timing of said pulse signal, second time measuring means for measuring a time from said start timing of each time slot to an input timing of said pulse signal transferred from said plurality of slave stations, and calculating means for obtaining time differences between measured times obtained by said first time measuring means and measured times obtained by said second time measuring means for each slave station, obtaining a hyperbolic function indicating a locus showing said time differences between said slave stations and calculating a position of an intersection of at least two hyperbolas; and

a surveillance subsystem, provided in said control equipment, for obtaining a position of an intersection of hyperbolas obtained by said master station as positional information of a control target as a sender every said surveillance cycle, detecting an identification code from a time slot for which a reception event has occurred to find a type of an associated control target, and performing a display process.

19. The control target surveillance system according to claim 18, wherein said first and second time measuring means of said master station start counters at start timings of respective time slots and obtaining count values of said counters at a reception timing for a local pulse signal and a reception timing for pulse signals transferred from said slave station, to thereby measure times.

20. The control target surveillance system according to claim 18, wherein said time managing means provided in said on-target subsystems and said master station perform time adjustment based on times managed by a navigation satellite used by said satellite navigation system.

22. A control target surveillance system for allowing a control equipment to monitor positions of a plurality of control targets in a control zone,

individual control targets mutually using a specific communications line to transmit local positioning data, and receiving and resending positioning data sent from other control targets, whereby positioning data of a plurality of control targets reach said control equipment.

23. The control target surveillance system according to claim 22, wherein time-divided time slots of a surveillance cycle associated in a non-overlapping manner with identification codes, previously given to all control targets in operation, are assigned to data transmission period of control targets having associated identification codes;

said plurality of control targets each have a function to obtain local positioning data, receive positioning data sent for each time slot from other control targets via a specific communications line and transmitting each positioning data in an assigned time slot via said communications line; and

said control equipment has a function to receive positioning data for each time slot via said specific communications line, discriminate an identification code from said time slot and discriminate a control target having sent said received positioning data.

24. The control target surveillance system according to claim 22, wherein said plurality of control targets and said control equipment each have time adjusting means for matching times, managed by themselves, with one another.

25. The control target surveillance system according to claim 24, wherein said time adjusting means obtains managed time from a navigation satellite using a satellite navigation system and performs time adjustment based on said managed time.

26. The control target surveillance system according to claim 24, wherein said control target comprises:

time slot managing means for managing said time slots based on said time adjusted by said time adjusting means;

positioning data obtaining means for obtaining at lest local positioning data using said satellite navigation system;

positioning data receiving means for receiving positioning data for each time slot from other control targets via said communications line; and

positioning data transmitting means for transmitting local and other positioning data, obtained by said positioning data obtaining means and said positioning data receiving means, in periods of associated time slots via said communications line.

27. The control target surveillance system according to claim 26, wherein said control targets each have monitor means for monitoring whether local and positioning data and relayed positioning data are inserted in a time slot sent at a time of reception of said positioning data.

28. The control target surveillance system according to claim 26, wherein each of said control targets sequentially repeats reception of positioning data, transmission of positioning data and no transmission/reception every surveillance cycle.

29. The control target surveillance system according to claim 26, wherein said positioning data obtaining means inserting obtained time information in positioning data.

30. The control target surveillance system according to claim 26, wherein said positioning data transmitting means has a function of updating positioning data to be sent so as to have latest time information.

31. The control target surveillance system according to claim 23, wherein said control equipment comprises:

time slot managing means for managing said time slots based on said time adjusted by said time adjusting means;

positioning data receiving means for receiving positioning data sent for each time slot from said control target via said communications line every given surveillance cycles;

sender discriminating means for, upon reception of positioning data, discriminating an associated identification code from said time slot to grasp said control target having sent said received positioning data; and

display means for displaying a position of each control target based on said positioning data obtained every given surveillance cycles and said control target having sent said positioning data.

32. The control target surveillance system according to claim 31, wherein said control equipment has current position predicting means for, when acquired time information is included in said positioning data, said control equipment, predicting a current position of said control target having sent said positioning data by referring to a flight plan of said control target, and said display means display said predicted current position.