APPARATUS AND METHOD FOR TRAFFIC LANE DETECTION

• US 20130214962A1
• Filed: 01/15/2013
• Published: 08/22/2013
• Est. Priority Date: 02/22/2012
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ochi, Mitsuru, Kajiki, Junko, Ikeya, Tomonori, Shite, Kazuhiko
• Granted Patent: US 9,134,408 B2
• Time in Patent Office: Days
• US Class Current: 342/109
• CPC Class Codes: G01S 13/58 Velocity or trajectory determination systems; Sense-of-movement determination 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

Two radar devices are installed for adjacent lanes. A memory sequentially stores a received power value at a time when the two radar devices receive the reflected wave from a vehicle at specified time intervals. A calculator calculates, when a vehicle moves in a direction approaching the two radar devices, as a representative value of the received power at a specified time, a weighted average value when weights, which become heavier as an acquisition time of the received power value becomes farther from the specified time, are assigned to a specified number of received power values, whose acquisition time is prior to a specified time, where a priority is given to the received power values whose acquisition time is close to the specified time. A discriminator determines a lane in which the vehicle is traveling according to a result of comparing the sizes of the calculated representative value.

Claims

1. An apparatus which detects a traffic lane, the apparatus comprising:

a plurality of radar devices provided for each lane, whose detection range includes an installed lane and an adjacent lane adjacent to the installed lane, the radar devices detecting a vehicle by emitting a radar wave to the vehicle traveling in the lane and by receiving a reflected wave from the vehicle;

a memory configured to sequentially store as a received power value an instantaneous value of a received power at a time when two radar devices installed for adjacent lanes out of the plurality of radar devices receive the reflected wave from a vehicle to be detected at specified time intervals;

a calculator configured to calculate, when the vehicle to be detected moves in a direction approaching the radar devices, as a representative value of a received power at a specified time in regard to each of the two radar devices, a weighted average value of the received power value when inverse weights, which become heavier as an acquisition time of the received power value becomes farther from the specified time, are assigned to a specified number of received power values stored in the memory according to a time at which the received power value is obtained, where an acquisition time of the received power values is prior to the specified time and a priority is given to the received power values whose acquisition time is close to the specified time; and

a discriminator configured to compare sizes of representative values of the received power calculated by the calculator between the two radar devices, and determine a lane in which the vehicle to be detected is traveling according to the comparison result.

2. The apparatus according to claim 1, wherein

when the vehicle to be detected is traveling in a direction moving away from the radar device, the calculator calculates, as a representative value of the received power at the specified time, a weighted average value of the received power value when normal weights, which become heavier as an acquisition time of the received power value becomes closer to the specified time, are assigned to a specified number of received power values stored in the memory according to a time at which the received power value is obtained, where an acquisition time of the received power values is prior to the specified time and a priority is given to the received power values whose acquisition time is close to the specified time.

3. The apparatus according to claim 2, wherein

the calculator uses identical weights to a specified number of weights assigned to a specified number of received power values in the normal weighting for a specified number of weights assigned to a specified number of received power values in the inverse weighting.

4. The apparatus according to claim 2, wherein

the radar devices output as a detection result moving direction information that indicates whether a moving direction of the detected vehicle is a direction approaching the radar devices or a direction moving away from the radar devices, and

the calculator determines whether the inverse weighting or the normal weighting should be used to calculate a representative value of the received power, according to the moving direction information.

5. The apparatus according to claim 1, wherein

the radar device outputs as a detection result a distance between the detected vehicle and the radar device, and

the apparatus further comprises a determiner configured to determine the specified number of received power values, which is used by the calculator to calculate a representative value of the received power at the specified time, according to a distance at the specified time between the vehicle to be detected and the radar device.

6. A method for detecting a traffic lane, the method comprising:

sequentially obtaining and storing in a memory as a received power value an instantaneous value of a received power at a time when two radar devices installed for adjacent lanes out of a plurality of radar devices, which are provided for each lane and whose detection range includes an installed lane and an adjacent lane adjacent to the installed lane, receive the reflected wave from a vehicle to be detected at specified time intervals, the radar devices detecting the vehicle by emitting a radar wave to the vehicle traveling in the lane and by receiving a reflected wave from the vehicle;

calculating, when the vehicle to be detected moves in a direction approaching the radar devices, as a representative value of a received power at a specified time in regard to each of the two radar devices, a weighted average value of the received power value when inverse weights, which become heavier as an acquisition time of the received power value becomes farther from the specified time, are assigned to a specified number of received power values stored in the memory according to a time at which the received power value is obtained, where an acquisition time of received power values is prior to the specified time and a priority is given to the received power values whose acquisition time is close to the specified time; and

comparing sizes of the calculated representative values of the received power between the two radar devices, and determining a lane in which the vehicle to be detected is traveling according to the comparison result.

7. The method according to claim 6, wherein

when the vehicle to be detected is traveling in a direction moving away from the radar device, as a representative value of the received power at the specified time, in calculation of a representative value of the received power at the specified time, a weighted average value of the received power value when normal weights, which become heavier as an acquisition time of the received power value becomes closer to the specified time, are assigned to a specified number of received power values stored in the memory according to a time at which the received power value is obtained, where an acquisition time of the received power values is prior to the specified time and a priority is given to the received power values whose acquisition time is close to the specified time, is calculated.

8. The method according to claim 7, wherein

in calculation of a representative value of the received power at the specified time, identical weights to a specified number of weights assigned to a specified number of received power values in the normal weighting are used for a specified number of weights assigned to a specified number of received power values in the inverse weighting.

9. The method according to claim 7, wherein:

the radar devices output as a detection result moving direction information that indicates whether a moving direction of the detected vehicle is a direction approaching the radar devices or a direction moving away from the radar devices, and

in calculation of a representative value of the received power at the specified time, whether the inverse weighting or the normal weighting should be used to calculate a representative value of the received power is determined according to the moving direction information.

10. The method according to claim 6, wherein:

the radar device outputs as a detection result a distance between the detected vehicle and the radar device, and

the method further comprises determining the specified number of received power values, which is used for calculating a representative value of the received power at the specified time, according to a distance at the specified time between the vehicle to be detected and the radar device.

11. A computer-readable recording medium having stored therein a program for causing a computer to execute a process for detecting a traffic lane, the process comprising:

sequentially obtaining and storing in a memory as a received power value an instantaneous value of a received power at a time when two radar devices installed for adjacent lanes out of a plurality of radar devices, which are provided for each lane and whose detection range includes an installed lane and an adjacent lane adjacent to the installed lane, receive the reflected wave from a vehicle to be detected at specified time intervals, the radar devices detecting the vehicle by emitting a radar wave to the vehicle traveling in the lane and by receiving a reflected wave from the vehicle;

calculating, when the vehicle to be detected moves in a direction approaching the radar devices, as a representative value of a received power at a specified time in regard to each of the two radar devices, a weighted average value of the received power value when inverse weights, which become heavier as an acquisition time of the received power value becomes farther from the specified time, are assigned to a specified number of received power values stored in the memory according to a time at which the received power value is obtained, where an acquisition time is prior to the specified time and a priority is given to the received power values whose acquisition time is close to the specified time; and

comparing sizes of the calculated representative values of the received power between the two radar devices, and determining a lane in which the vehicle to be detected is traveling according to the comparison result.

12. The recording medium according to claim 11, wherein

when the vehicle to be detected is traveling in a direction moving away from the radar device, as a representative value of the received power at the specified time, in calculation of a representative value of the received power at the specified time, a weighted average value of the received power value when normal weights, which become heavier as an acquisition time of the received power value becomes closer to the specified time, are assigned to a specified number of received power values stored in the memory according to a time at which the received power value is obtained, where an acquisition time of the received power values is prior to the specified time and a priority is given to the received power values whose acquisition time is close to the specified time, is calculated.

13. The recording medium according to claim 12, wherein

in calculation of a representative value of the received power at the specified time, identical weights to a specified number of weights assigned to a specified number of received power values in the normal weighting are used for a specified number of weights assigned to a specified number of received power values in the inverse weighting.

14. The recording medium according to claim 12, wherein

when the radar devices output as a detection result moving direction information that indicates whether a moving direction of the detected vehicle is a direction approaching the radar devices or a direction moving away from the radar devices, in calculation of a representative value of the received power at the specified time, whether the inverse weighting or the normal weighting should be used to calculate a representative value of the received power is determined according to the moving direction information.

15. The recording medium according to claim 11, the process further comprising:

when the radar device outputs as a detection result a distance between the detected vehicle and the radar device, determining the specified number of received power values, which is used for calculating a representative value of the received power at the specified time, according to a distance at the specified time between the vehicle to be detected and the radar device.