METHOD AND APPARATUS FOR MEASURING DISTANCES, AND METHOD FOR DETERMINING POSITIONS

• US 20140057655A1
• Filed: 04/25/2012
• Published: 02/27/2014
• Est. Priority Date: 04/29/2011
• Status: Active Grant

• Current Assignee: Orthotron Company Limited
• Original Assignee: Orthotron Company Limited
• Inventors: Lee, Kyungkuk
• Granted Patent: US 9,201,140 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence

Abstract

The present disclosure provides a ranging method by using a first signal transmitted by a first device, and a second signal generated and transmitted by a target device in response to the first signal. The ranging method calculates the distance between the target device and a second device being in communication with the first and target devices, by using: a first time interval from a point in time of first device'"'"'s transmitting the first signal to a point of receiving first part of the second signal; a second time interval from a point of the second device'"'"'s receiving the first signal to a point receiving the first part of the second signal; and a delay time interval from a point of the target device'"'"'s receiving the first signal to a start time of the second signal and a duration of the first part of the second signal.

Claims

1. A ranging method by using a first signal transmitted by a first device and a second signal generated and transmitted by a target device in response to the first signal, the method calculating a distance between the target device and a second device being in communication with the first device and the target device, by using:

a first time interval from a time point of the first device'"'"'s transmitting the first signal to a time point of the first device'"'"'s receiving a first part of the second signal;

a second time interval from a time point of the second device'"'"'s receiving the first signal to a time point of the second device'"'"'s receiving the first part of the second signal; and

a delay time interval from a time point of the target device'"'"'s receiving the first signal to a start time of the second signal and a duration of the first part of the second signal.

2. The ranging method of claim 1, wherein a distance d0 from the first device to the target device is calculated using the first time interval, the delay time interval, and the duration of the first part of the second signal.

3. The ranging method of claim 2, wherein the distance d0 is calculated by equation

d0=D_CLK*(N0−

Mgap−

M0)/2

D_CLK=c*(T_CLK/M_INT)

based on the first time interval of counts N0 by the first device of a unit time generated by dividing the first device'"'"'s clock period by an interpolation division integer, where c denotes a signal transmission speed in a medium, T_CLK denotes a nominal clock period, M_INT denotes an interpolation division integer equal to or larger than 1, Mgap denotes a number of clocks used for generating a delay time interval corresponding to a known value, and M0 denotes a number of clocks used for generation of the first part of the second signal.

4. The ranging method of claim 3, wherein a distance d1 from the second device to the target device is calculated using the second time interval, the delay time interval, the duration of the first part of the second signal, and the distance d0.

5. The ranging method of claim 4, wherein the distance d1 is calculated by equation

d1=D_CLK*(N1−

Mgap−

M0)+D01−

d0

based on the second time interval of counts N1 by the second device of a unit time generated by dividing the second device'"'"'s clock period by an interpolation division integer, where D01 denotes a distance between the first device and the second device.

6. The ranging method of claim 1, wherein the calculation of the distance between the second device and the target device additionally uses:

a third time interval from a time point of the first device'"'"'s receiving the first part of the second signal to a time point of the first device'"'"'s receiving a second part of the second signal;

a fourth time interval from a time point of the second device'"'"'s receiving the first part of the second signal to a time point of the second device'"'"'s receiving the second part of the second signal; and

a duration of the second part of the second signal.

7. The ranging method of claim 6, wherein a distance d0 between the first device and the target device is calculated based on the first time interval of counts N01 by the first device of a unit time generated by dividing the first device'"'"'s clock period by an interpolation division integer and the third time interval of counts N02 by the first device of the unit time.

8. The ranging method of claim 7, wherein the distance d0 is calculated by equation

d0=D_CLK*(N01−

Kr*N02)/2

Kr=(Mgap+M1)/M2,D_CLK=c*(T_CLK/M_INT),

where c denotes a transmission speed of a signal in a medium, T_CLK denotes a nominal clock period, M_INT denotes an interpolation division integer equal to or larger than 1, Mgap denotes a number of clocks used for generating the delay time interval corresponding to a known value, M1 denotes a number of clocks used for generation of the first part of the second signal, and M2 denotes a number of clocks used for generation of the second part of the second signal.

9. The ranging method of claim 7, wherein a distance d1 between the second device and the target device is calculated based on the second time interval of counts N11 by the second device of a unit time generated by dividing the second device'"'"'s clock period by an interpolation division integer, the fourth time interval of counts N12 by the second device of the unit time, the delay time interval, the duration of the first part of the second signal, and the distance d0.

10. The ranging method of claim 9, wherein the distance d1 is calculated by equation

d0=D_CLK*(N11−

Kr*N12)+D01−

d0

Kr=(Mgap+M1)/M2,D_CLK=c*(T_CLK/M_INT),

where c denotes a transmission speed of a signal in a medium, T_CLK denotes a nominal clock period, M_INT denotes an in interpolation division integer equal to or larger than 1, Mgap denotes a number of clocks used for generating the delay time interval corresponding to a known value, M1 denotes a number of clocks used for generation of the first part of the second signal, M2 denotes a number of clocks used for generation of the second part of the second signal, and D01 denotes a distance between the first device and the second device corresponding to a known value.

11. A ranging apparatus using a first signal transmitted by a first device and a second signal generated and transmitted by a target device in response to the first device, the ranging apparatus calculating a distance between the target device and a second device being in communication with the first device and the target device, by using:

a first time interval from a time point of the first device'"'"'s transmitting the first signal to a time point of the first device'"'"'s receiving a first part of the second signal;

a second time interval from a time point of the second device'"'"'s receiving the first signal to a time point of the second device'"'"'s receiving the first part of the second signal; and

a delay time interval from a time point of the target device'"'"'s receiving the first signal to a start time point of the second signal and a duration of the first part of the second signal.

12. A positioning method performed by a positioning system including a target device, a master device and one or more slave devices, the positioning method comprising:

generating and transmitting a first signal by using the master device;

generating and transmitting, by using the target device, a second signal in response to the first signal after lapse of a predetermined delay time interval;

measuring a first time interval measured from a time point of the master device'"'"'s transmitting the first signal to a time point of the master device'"'"'s receiving a first part of the second signal;

measuring a second time interval measured from a time point of the slave device'"'"'s receiving the first signal to a time point of receiving the first part of the second signal; and

determining a position of the target device based on the first time interval, the second time interval, the delay time interval, and a duration of the first part of the second signal.

13. The positioning method of claim 12, wherein the determining of the position of the target device comprises:

calculating a distance d0 between the master device and the target device based on the first time interval, the delay time interval, and the duration of the first part of the second signal;

calculating a distance di (i is used as an index for distinguishing each of the slave devices) between the slave devices and the target device based on the second time interval, the delay time interval, the duration of the first part of the second signal, and the distance d0; and

determining the position of the target device by using the distance d0, the distance d1, and position information on each of the master device and each of the slave devices.

14. The positioning method of claim 12, further comprising:

calculating, by using the master device, the first time interval of counts N01 of a unit time generated by dividing the master device'"'"'s clock period by an interpolation division integer and counts N02 of the unit time during a time interval from a time point of the master device'"'"'s receiving the first part of the second signal to a time point of receiving the second part of the second signal; and

calculating, by using the slave unit, the second time interval of counts Ni1, in which i is used as an index for distinguishing each of the slave devices, of a unit time generated by dividing the slave device'"'"'s clock period by an interpolation division integer and counts Ni2 during a time interval from a time point of receiving the first part of the second signal to a time point of receiving the second part of the second signal.

15. The positioning method of claim 14, further comprising:

calculating a distance d0 between the master device and the target device based on the counts N01 and N02;

calculating a distance d1 between the slave devices and the target device based on the counts Ni1 and Ni2; and

determining a position of the target device by using the distance d0, the distance dl, and position information on each of the master device and each of the slave devices.

16. The positioning method of claim 15, wherein the distance d0 and the distance d1 are calculated by equation

d0=D_CLK*(N01−

Kr*N02)/2

di=D_CLK*(Ni1−

Kr*Ni2)+D0i−

d0

Kr=(Mgap+M1)/M2,D_CLK=c*(T_CLK/M_INT),

where c denotes a transmission speed of a signal in a medium, T_CLK denotes a nominal clock period, M_INT denotes an in interpolation division integer equal to or larger than 1, Mgap denotes a number of clocks used for generating the delay time interval corresponding to a known value, M1 denotes a number of clocks used for generation of the first part of the second signal, M2 denotes a number of clocks used for generation of the second part of the second signal, and D0i denotes a distance between the master device and the slave devices corresponding to a known value.

17. The positioning method of claim 12, wherein the positioning system includes a function of role exchanging between one of the slave devices and the master device.

18. The positioning method of claim 12, wherein the first signal includes at least one of master device identification information, target device identification information, sequence number for each target device identification information, current time information, and next wake-up time information allocated for each target device identification information, and the sequence number for each target device identification information is updated by a different value whenever the first signal is transmitted.

19. The positioning method of claim 18, wherein the target device generates and transmits the second signal only when pre-stored target device identification information and the target device identification information included in the first signal match each other.

20. The positioning method of claim 18, wherein the target device shifts between a sleep mode and an active mode by using the next wake-up time information included in the first signal.

21. The positioning method of claim 14, wherein a locating server included in the positioning system receives N01, N02, Ni1, and Ni2 together with the target device identification information and the sequence number for each target device identification information, and determines a position of the target device by managing and classifying N01, N02, Ni1, and Ni2 based on the target device identification information and the sequence number for each target device identification information.

22. The positioning method of claim 12, wherein the master device generates a time reference signal by using the master device'"'"'s current real time clock and transmits the generated time reference signal to the target device, and the target device controls the target device'"'"'s RTC by using the time reference signal.

23. The positioning method of claim 12, further comprising performing an initialization operation by using the target device for communication with the master device, wherein the initialization operation comprises:

transmitting, by using the target device, an access signal including the target device'"'"'s identification information;

waiting for a control signal from the master device for a preset time-out period after transmitting the access signal;

performing an initialization of the target device by using information included in the control signal, in response to the control signal within the time-out period; and

returning to the transmitting of the access signal after a preset recess time interval, in the absence of the control signal within the time-out period.

24. The positioning method of claim 17, further comprising performing an initialization operation by using the master device for communication with the target device, wherein the initialization operation comprises:

transmitting quality information on the access signal to a locating server by each of one or more master devices having received the access signal from the target device;

selecting, by using the locating server, an optimal master device suitable for communication with the target device from the one or more master devices by using the quality information on the access signal and informing the optimal master device of a result of the selection; and

transmitting a control signal to the target device in response to the access signal from the target device after the optimal master device is informed of the result of the selection.

25. The positioning method of claim 17, further comprising selecting an optimal master device to perform communication with the target device from a plurality of master devices, if present around the target device, wherein the selecting of the optimal master device comprises:

transmitting quality information on a received signal to a locating server when the plurality of master devices receive the second signal from the target device;

selecting the optimal master device suitable for the communication with the target device from the plurality of master devices by using the quality information on the received signal and informing the optimal master device of a result of the selection by the locating server; and

transmitting the first signal to the target device by the optimal master device having been informed of the result of the selection.

26. A ranging method using a first signal transmitted by a first device and a second signal transmitted by a second device in response to reception of the first signal, the method calculating a distance between the first device and the second device by using:

a first time interval from a time point of the first device'"'"'s transmitting the first signal to a time point of the first device'"'"'s receiving a first part of the second signal and a second time interval from a time point of the second device'"'"'s receiving the first part of the second signal to a time point of the second device'"'"'s receiving a second part of the second signal;

a delay time interval from a time point of the second device'"'"'s receiving the first signal to a start time point of the second signal; and

a duration of the first part of the second signal and a duration of the second part of the second signal.

27. The positioning method of claim 26, wherein a distance d0 between the first device and the second device is measured based on the first time interval of counts N01 by the first device of a unit time generated by dividing a first-device clock period by an interpolation division integer and the second time interval of counts N02 by the first device of the unit time.

28. The positioning method of claim 27, wherein the distance d0 is calculated by equation

d0=D_CLK*(N01−

Kr*N02)*2

Kr=(Mgap+M1)/M2,D_CLK=c*(T_CLK/M_INT),

where c denotes a transmission speed of a signal in a medium, T_CLK denotes a nominal clock period, M_INT denotes an in interpolation division integer equal to or larger than 1, Mgap denotes a number of clocks used for generating the delay time interval corresponding to a known value, M1 denotes a number of clocks used for generation of the first part of the second signal, and M2 denotes a number of clocks used for generation of the second part of the second signal.

29. The positioning method of claim 28, wherein a value generated by dividing T_CLK by M_INT is smaller than or equal to time resolution required for a positioning.

30. The positioning method of claim 26, wherein the first time interval, the second time interval, the delay time interval, and the duration of each of the first part and the second part of the second signal are values compensated for a time delay error due to an intrinsic time delay generated in the first device or the second device.

31. The positioning method of claim 30, wherein the first device or the second device uses a table for storing a variation in the intrinsic time delay according to one or more ambient environment changes of a change in ambient temperature, a change in an operation voltage, and an aging change, and controls the intrinsic delay time by using the table.