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EP-3859707-B1 - ROAD SIGN RECOGNITION DEVICE

EP3859707B1EP 3859707 B1EP3859707 B1EP 3859707B1EP-3859707-B1

Inventors

  • ENDO, TAKESHI
  • NAGASAKI, TAKESHI

Dates

Publication Date
20260506
Application Date
20190806

Claims (7)

  1. A road sign recognition device (10) comprising: an image acquisition unit (101) that acquires an image; a road sign recognition unit (102) that recognizes a road sign from the image acquired by the image acquisition unit (101), wherein the road sign recognition unit (102) performs a circle detection process to detect a circular area corresponding to a shape of a main sign in the image and set this area as a candidate area for the main sign, and a main sign recognition process on an image area including the candidate area for the main sign to detect the main sign and identify its type; a road sign data recording unit (103) that stores road sign information about a combination of a plurality of road signs; and a vehicle control information determination unit (104) that determines vehicle control information used for controlling a host vehicle, wherein the vehicle control information determination unit (104) determines the vehicle control information based on a road sign recognition result of the road sign recognition unit (102) and the road sign information stored in the road sign data recording unit (103), wherein the road sign information includes combination information about a combination of a main sign and an auxiliary sign, and wherein the combination information includes information about likelihood of attachment of an auxiliary sign for each main sign, and when a plurality of the main signs are recognized from the image, the road sign recognition unit (102) selects main signs within a predetermined upper limit number in order from one with the highest likelihood of auxiliary sign attachment among the plurality of main signs, and performs an auxiliary sign recognition process on a periphery of each of the selected main signs, wherein the road sign recognition unit (102) performs an auxiliary sign recognition process while prioritizing a periphery of a main sign to which an auxiliary sign is highly likely to be attached in the combination information among the plurality of main signs, wherein the vehicle control information determination unit (104) acquires the combination information corresponding to a main sign from the road sign data recording unit (103) based on a recognition result of the main sign of the road sign recognition unit (102), and identifies a type of an auxiliary sign used for determining the vehicle control information based on the acquired combination information and a recognition result of the auxiliary sign of the road sign recognition unit (102).
  2. The road sign recognition device (10) according to claim 1, wherein when recognition precision of an auxiliary sign of the road sign recognition unit (102) is equal to or higher than a predetermined value, the vehicle control information determination unit (104) identifies the type of the auxiliary sign used for determining the vehicle control information without using the combination information stored in the road sign data recording unit (103).
  3. The road sign recognition device (10) according to claim 1, wherein when recognition precision of an auxiliary sign of the road sign recognition unit (102) is lower than a predetermined value, the vehicle control information determination unit (104) identifies the type of the auxiliary sign used for determining the vehicle control information by using the combination information acquired from the road sign data recording unit (103) with a priority over the recognition result of the auxiliary sign of the road sign recognition unit (102).
  4. The road sign recognition device (10) according to claim 1, further comprising: a travel environment acquisition unit that acquires travel environment information around the host vehicle, wherein the road sign information includes information about a travel environment for each road sign, and the vehicle control information determination unit (104) determines the vehicle control information based on a road sign recognition result of the road sign recognition unit (102), the travel environment information acquired by the travel environment acquisition unit, and the road sign information stored in the road sign data recording unit (103).
  5. The road sign recognition device (10) according to claim 4, wherein the road sign information includes combination information about a combination of a main sign and an auxiliary sign for each road type, and the vehicle control information determination unit (104) acquires the combination information corresponding to a main sign from the road sign data recording unit (103) based on a recognition result of the main sign of the road sign recognition unit (102), and identifies a type of an auxiliary sign used for determining the vehicle control information based on the acquired combination information, a recognition result of the auxiliary sign of the road sign recognition unit (102), and a road type represented by the travel environment information acquired by the travel environment acquisition unit.
  6. The road sign recognition device (10) according to claim 4, wherein the road sign data recording unit (103) stores the road sign information for each of a plurality of countries or regions, and the vehicle control information determination unit (104) switches the road sign information used for determining the vehicle control information in accordance with a country or a region represented by the travel environment information acquired by the travel environment acquisition unit.
  7. The road sign recognition device (10) according to claim 1, further comprising: a road sign information rewriting unit that rewrites the road sign information stored in the road sign data recording unit (103) based on the road sign recognition result of the road sign recognition unit (102).

Description

Technical Field The present invention relates to a road sign recognition device. Background Art In order to realize automatic driving and prevent traffic accidents, there is a great deal of interest in road sign recognition techniques that recognize road signs in a traveling vehicle and uses recognition results to control the vehicle. Some road signs are combinations of main signs indicating various regulation contents on vehicles and auxiliary signs indicating supplementary information on the main signs, such as conditions under which the regulation contents of the main signs are applied. When a vehicle is controlled by recognizing such a road sign in which a main sign and an auxiliary sign are combined in this manner, it is important to determine the validity of a regulation content of the main sign for the vehicle based on the recognition result of the auxiliary sign. Regarding the recognition of the road sign in which the main sign and the auxiliary sign are combined, for example, PTL 1 discloses a sign recognition device that includes: a sign effective range data recording unit for prestoring effective range conditions shown by a main sign and an auxiliary sign; a sign recognition unit for recognizing a main sign and an auxiliary sign by using a captured image of a roadway in front of a vehicle; and a sign effective range determining unit for determining whether or not the vehicle is staying in an effective range specified with the main sign and the auxiliary sign which have been recognized by the sign recognition unit by using the effective range conditions stored in the sign effective range data recording unit, the vehicle information, and map information. Additionally, PTL 2 discloses a road sign recognition system that uses a combination of image recognition and probability-based analysis, utilizing a database storing main sign-auxiliary sign combination probabilities, another database storing word connection probabilities, and a third database storing word meanings. PTL 3 discloses an image processing system for recognizing traffic signs, particularly combinations of main signs and auxiliary signs. The system uses contrast correction and color analysis to detect circular main signs and rectangular auxiliary signs in vehicle camera images. Overall, PTL 3 determines relationships between detected signs based on their relative positions and validates sign orientations using width-to-height ratios. Citation List Patent Literature PTL 1: JP 2010-282278 APTL 2: JP 2018 116553 APTL 3: EP 3 208 740 A1 Summary of Invention Technical Problem In the sign recognition device of PTL 1, the road sign needs to be accurately recognized as the premise of correctly determining whether or not the vehicle is staying in the effective range of the road sign. However, the auxiliary sign usually has smaller characters or patterns than the main sign, and is likely to cause misrecognition. Therefore, when the sign recognition device of PTL 1 is used for controlling a vehicle, there is a problem that it is difficult to correctly determine the control content from the recognition result of the road sign. In view of such a problem, an object of the present invention is to provide a technique for correctly determining the control content of a vehicle from a recognition result of a road sign. Solution to Problem The invention is set out in the appended set of claims. Preferable embodiments are defined in the dependent claims. Advantageous Effects of Invention According to the present invention, the control content of the vehicle can be correctly determined from the recognition result of the road sign. Brief Description of Drawings [FIG. 1] FIG. 1 is a functional block diagram illustrating a configuration of a road sign recognition device according to a first embodiment of the present invention.[FIG. 2] FIG. 2 is a view illustrating a scene for describing an operation of the road sign recognition device according to the first embodiment of the present invention.[FIG. 3] FIG. 3 is a flowchart illustrating a processing flow of the road sign recognition device according to the first embodiment of the present invention.[FIG. 4] FIG. 4 is a view illustrating an example of road sign information according to the first embodiment of the present invention.[FIG. 5] FIG. 5 is a view illustrating an example of a recognition result of an auxiliary sign according to the first embodiment of the present invention.[FIG. 6] FIG. 6 is a view illustrating an example of road sign information according to a second embodiment of the present invention.[FIG. 7] FIG. 7 is a flowchart illustrating a processing flow of a road sign recognition device according to a third embodiment of the present invention.[FIG. 8] FIG. 8 is a flowchart illustrating a processing flow of a road sign recognition device according to a fourth embodiment of the present invention.[FIG. 9] FIG. 9 is a view illustrating a scene for describing an operation of a road sign recognition