Vehicle control device and speed limit signal generation method

Abstract

To provide a control system for generating a speed limit signal for controlling a vehicle, and a method for the control system.SOLUTION: A control system is configured to receive image data showing an environment of a vehicle from one or more imaging apparatuses related to the vehicle. The control system is configured to determine a speed limit shown by a traffic sign and a position of the traffic sign to road characteristics in the environment depending on the image data. Relevance of the speed limit to the vehicle is determined depending on the determined position of the traffic sign and the determined position of the vehicle. A speed limit signal showing the speed limit is selectively generated according to the determined relevance and output to at least one vehicle control system. A traffic sign which is not related to the vehicle thus can be effectively filtered in relation to a side road SR.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] TECHNICAL FIELD The present disclosure relates to generating a speed limit signal. Aspects of the present disclosure relate to a control system for generating a speed limit signal, a vehicle, and a computer-implemented method for generating a speed limit signal. [Background technology]

[0002] Traffic Sign Recognition (TSR) systems are designed to recognize approaching traffic signs and update or control vehicle systems accordingly. Traffic signs include speed limit signs. Speed ​​limit sign recognition can be used to update or overwrite speed limits extracted from map data, such as when a temporary speed limit exists. Speed ​​limit sign recognition can also be used to provide speed limit information when the speed limit is not available from the map data, for example because the vehicle is traveling on a road segment that does not exist in the map data.

[0003] TSR systems work by recognizing, to the greatest extent possible, all traffic signs in the imagery and / or video data showing the environment in front of the vehicle. However, some of the recognized traffic signs may not apply to the road the vehicle is traveling on. If an oncoming speed limit sign is not correctly identified, this can cause inconvenience to the driver of the vehicle.

[0004] It is an object of the present invention to address one or more of the shortcomings associated with the prior art. Summary of the Invention

[0005] Aspects and embodiments of the present invention provide a control system, a vehicle, and a computer-implemented method as set forth in the accompanying claims.

[0006] According to one aspect of the invention, there is provided a control system for generating a speed limit signal for controlling a vehicle, the control system including one or more controllers. The control system is configured to receive image data indicative of an environment of the vehicle from one or more imaging devices associated with the vehicle, determine a speed limit indicated by a traffic sign and a position of the traffic sign in dependence on the image data, determine a relevance of the speed limit to the vehicle in dependence on the determined positions of the traffic signs and the determined position of the vehicle, and selectively generate a signed speed limit signal indicative of the speed limit in dependence on the determined relevance. The control system may output the selectively generated signal to at least one vehicle control system.

[0007] According to a further aspect, a control system for generating a speed limit signal for controlling a vehicle is provided, the control system including one or more controllers. The control system receives image data indicative of the vehicle's environment from one or more imaging devices associated with the vehicle, determines in dependence on the image data a speed limit indicated by a traffic sign and a position of the traffic sign relative to an edge of a road on which the vehicle is located, determines a relevance of the speed limit to the vehicle in dependence on the determined position of the traffic sign relative to the edge of the road and the determined position of the vehicle, selectively generates a sign speed limit signal indicative of the speed limit in dependence on the determined relevance, and outputs the selectively generated signal to at least one vehicle control system. Advantageously, it is possible to determine whether a traffic sign applies to a road on which the vehicle is traveling depending on whether the sign is close to an edge of the road. Thus, irrelevant speed limit signs may be filtered out.

[0008] According to a further aspect, a control system for generating a speed limit signal for controlling a vehicle is provided, the control system including one or more controllers. The control system receives image data indicative of the vehicle's environment from one or more imaging devices associated with the vehicle, determines a speed limit indicated by a traffic sign and a position of the traffic sign relative to an entrance stub to a side road depending on the image data, determines a relevance of the speed limit to the vehicle depending on the determined position of the traffic sign relative to the entrance stub and the determined position of the vehicle, selectively generates a sign speed limit signal indicative of the speed limit depending on the determined relevance, and outputs the selectively generated signal to at least one vehicle control system. Advantageously, it can be determined whether a traffic sign applies to the road on which the vehicle is located depending on whether the traffic sign is close to a side road entrance to the road. Thus, irrelevant speed limit signs may be filtered out.

[0009] According to a further aspect, a control system for generating a speed limit signal for controlling a vehicle is provided, the control system including one or more controllers. The control system receives image data indicative of an environment of the vehicle from one or more imaging devices associated with the vehicle, determines a speed limit indicated by a traffic sign and a position of the traffic sign relative to a further traffic sign indicating the speed limit in dependence on the image data, determines a relevance of the speed limit to the vehicle in dependence on the determined position of the traffic sign relative to the further traffic sign and the determined position of the vehicle, selectively generates a speed limit signal indicative of the speed limit in dependence on the determined relevance, and outputs the selectively generated signal to at least one vehicle control system. Advantageously, the pairing of the traffic sign with another traffic sign and the position of the pair may be used to determine whether the traffic sign is applicable to the road on which the vehicle is located. Thus, irrelevant speed limit signs may be filtered out.

[0010] According to a further aspect, a control system for generating a speed limit signal for controlling a vehicle is provided, the control system including one or more controllers. The control system receives image data indicative of an environment of the vehicle from one or more imaging devices associated with the vehicle, determines a speed limit indicated by a traffic sign and a position of the traffic sign relative to road features in the environment in dependence on the image data, determines a relevance of the speed limit to the vehicle in dependence on the determined positions of the traffic signs and the determined position of the vehicle, selectively generates a sign speed limit signal indicative of the speed limit in dependence on the determined relevance, and outputs the selectively generated signal to at least one vehicle control system. Advantageously, the identified road features can be used to determine whether the traffic sign is applicable to the road on which the vehicle is located. Thus, irrelevant speed limit signs may be filtered out.

[0011] The selectively generated signal may be output for display to a user to inform the user of the associated speed limit. The selectively generated signal may be output to adjust a cruise control system of the vehicle. Additionally or alternatively, the selectively generated signal may be output to a warning system, for example to warn a driver that an associated speed limit is being exceeded.

[0012] Determining the relevance may include classifying the speed limit as relevant or not relevant to the vehicle. The determined relevance may be indicative of the likelihood that the traffic sign is relevant to the road segment on which the vehicle is located or the road segment on which the vehicle will be located based on the vehicle's predicted path. The speed limit may be classified as not relevant depending on the likelihood that the traffic sign applies to a side road on which the vehicle is not located. The speed limit signal may be selectively output depending on the speed limit being determined to be relevant. Optionally, the sign speed limit signal may be selectively output depending on the speed limit being determined to be relevant to a characteristic of the vehicle. For example, a traffic sign may be determined to apply to the road segment on which the vehicle is located but only relevant to vehicles having a particular characteristic, such as vehicles over a certain size.

[0013] Optionally, the control system is configured to receive digital map data including an indication of a speed limit on a map associated with the road segment on which the vehicle is located. Depending on the speed limit indicated by the traffic sign being determined to be not relevant, the control system may be configured to generate a map speed limit signal indicative of the map speed limit and output the map speed limit signal to the at least one vehicle control system. If the speed limit indicated by the traffic sign is determined to be relevant, the control system may be configured to preferentially output the sign speed limit signal. Advantageously, only the speed limit indicated by the associated road sign may take precedence over the speed limit indicated by the map data.

[0014] Optionally, determining the location of the traffic sign includes determining a distance from the traffic sign to the road feature. The relevance of the speed limit may be determined depending on whether the distance meets a predetermined criterion, such as a minimum distance or a maximum distance.

[0015] According to an embodiment, the road features include an edge of the road on which the vehicle is located. The road on which the vehicle is located and / or the road on which the vehicle is predicted to be located from its trajectory may hereinafter be referred to as a main road. Roads other than the main road may hereinafter be referred to as side roads. A side road may be a road on which the vehicle is not located. A side road may for example be a road that branches off from a main road, a road that crosses a main road, or a road that does not border a main road. For example, a side road may include a road that is substantially parallel to a main road. The control system may be configured to determine a distance from a traffic sign to an edge of the main road. Optionally, the distance is a lateral distance. A lateral distance may be defined as a distance taken substantially perpendicular to the road edge. Advantageously, the lateral distance at which a traffic sign is located from a road edge is approximately standardized for a given geographical area, for example a given country.

[0016] The control system may be configured to determine that the speed limit is not relevant for the vehicle if the determined distance to the edge of the road is greater than a predefined threshold, which may be set depending on the standardized distance of the geographical area in which the vehicle is located. Advantageously, filtering traffic signs whose lateral distance exceeds this threshold effectively filters traffic signs that are located too far from the edge of the road and therefore unlikely to apply to the road in which the vehicle is located.

[0017] According to an embodiment, the at least one road feature includes an entrance stub to a side road. An entrance stub can be defined as a point where a side road branches off or deviates from a main road. An entrance stub can be any branching point, such as a junction, a roundabout exit, or an intersection.

[0018] The control system may be configured to determine the location of the traffic sign by determining a stub distance from the traffic sign to an entrance stub of a side road. Advantageously, proximity to an entrance stub indicates the likelihood that the traffic sign applies to a side road and is therefore not associated with the vehicle.

[0019] Optionally, the control system is configured to receive digital map data indicating a mapped speed limit associated with a side road, and determine that a traffic sign is not relevant if the speed limit matches a mapped speed limit associated with the side road and the stub distance is less than a predetermined stub distance threshold. Beneficially, a traffic sign may be ignored as not relevant only if the speed limit matches one that is expected to apply to the side road based on the digital map data. In this way, a traffic sign that applies to a main road that happens to occur in the vicinity of an entrance stub of a side road will not be erroneously determined to be not relevant.

[0020] According to an embodiment, the road features include a further traffic sign indicating a speed limit. The control system may be configured to determine whether the traffic sign and the further traffic sign straddle a side road depending on the position of the traffic sign relative to the further traffic sign. Straddling a side road means that the traffic sign and the further traffic sign are located on either side of the side road at the predefined position, respectively. The control system may be configured to determine that the speed limit is not relevant if the traffic sign and the further traffic sign straddle a side road. Advantageously, the presence of a sign on both sides of a road indicates that the sign is associated with the road running between them. Thus, if the sign and the further sign straddle a side road, the sign may be effectively filtered as not associated with a main road.

[0021] Optionally, the traffic sign and the further traffic sign may be determined to straddle a side road if the traffic sign and the further traffic sign are each offset to a first side of the vehicle's path. Optionally, the traffic sign and the further traffic sign are determined to straddle a side road only if the distance between the traffic sign and the further traffic sign is greater than a predetermined minimum distance. Optionally, the traffic sign and the further traffic sign may be determined to straddle a side road only if the distance between the traffic sign and the further traffic sign is less than a predetermined maximum distance.

[0022] Optionally, the or each controller includes an electrical input for receiving an electrical signal indicative of image data, an electrical output for outputting an electrical signal indicative of the speed limit, and one or more electronic processors for operatively executing computer readable instructions for determining the relevance of the speed limit.

[0023] According to another aspect of the invention there is provided a vehicle including a control system as described above.

[0024] According to a further aspect, there is provided a computer-implemented method for generating a speed limit signal for control of a vehicle, the method comprising: receiving image data indicative of an environment of the vehicle from one or more imaging devices associated with the vehicle; determining in dependence on the image data a speed limit indicated by a traffic sign and a position of the traffic sign relative to road features in the environment; determining a relevance of the speed limit to the vehicle in dependence on the determined positions of the traffic signs and the determined position of the vehicle; selectively generating a speed limit signal indicative of the speed limit in dependence on the determined relevance; and outputting the selectively generated signal to at least one vehicle control system.

[0025] Optionally, the method comprises receiving digital map data including an indication of a map speed limit associated with a road segment on which the vehicle is located, and if the speed limit indicated by the traffic sign is determined to be not relevant, generating a map speed limit signal indicative of the map speed limit and outputting the map speed limit signal to the at least one vehicle control system. The method may include preferentially outputting the sign speed limit signal dependent on the traffic sign being determined to be relevant.

[0026] Optionally, determining the location of the traffic sign includes determining a distance from the traffic sign to the road feature.

[0027] The road features may include an edge of the road on which the vehicle is located, and locating the traffic sign includes determining a distance from the traffic sign to the edge of the road, and the method may include determining a speed limit not associated with the vehicle if the determined distance to the edge of the road is greater than a predetermined threshold.

[0028] Optionally, the at least one road feature may include a side road entrance stub, and determining the position of the traffic sign may include determining a stub distance from the traffic sign to the side road entrance stub, and determining the position of the traffic sign may include determining a distance to the side road entrance stub.

[0029] Optionally, the method may include receiving digital map data indicating an on-map speed limit associated with a side road, and determining that the speed limit is not relevant if the speed limit matches the on-map speed limit associated with the side road and the stub distance is less than a predetermined stub distance threshold.

[0030] Optionally, the road features may include a further traffic sign indicating a speed limit, and the method may include determining whether the traffic sign and the further traffic sign cross a side road depending on a position of the traffic sign relative to the further traffic sign.

[0031] Optionally, or each controller may be configured to determine that the speed limit is not relevant depending on whether the traffic sign and the further traffic sign straddle the side road.

[0032] According to a further aspect, there is provided a computer readable medium containing computer software which, when executed, causes the performance of the above method.

[0033] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives described in the preceding paragraphs, claims and / or the following description and drawings, in particular their individual features, can be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any manner and / or combination, except where such features are incompatible. The applicants have the right to modify the originally filed claims accordingly or to file new claims, including the right to amend the originally filed claims to rely on and / or incorporate features of other claims, even though not originally so claimed. [Brief description of the drawings]

[0034] One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0035] [Figure 1] FIG. 1 is a first schematic diagram of a control system according to an embodiment. [Diagram 2] FIG. 2 shows a vehicle according to an embodiment. [Diagram 3] Figure 3 shows a vehicle traveling along a major road. [Figure 4A] FIG. 4A shows a first type of side road adjacent to a main road. [Figure 4B] FIG. 4B shows a second type of side road that is not adjacent to a main road. [Diagram 5] FIG. 5 illustrates a method according to one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing the distance from a traffic sign to the road edge of a primary road. [Figure 7] FIG. 7 shows a traffic sign near an entrance stub to a side road. [Figure 8] FIG. 8 shows two traffic signs straddling a side road. [Figure 9] FIG. 9 is a diagram illustrating a method for determining relevance according to an embodiment of the present invention. [Figure 10] FIG. 10 is a second schematic diagram of the control system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] A control system 110 according to an embodiment of the present invention will now be described with reference to the accompanying drawings. The control system 110 according to the embodiment is a Traffic Sign Recognition (TSR) system. The traffic sign recognition system is a system for generating a speed limit signal for controlling a vehicle depending on the relevance of a recognized traffic sign, as will now be described. As shown in FIG. 2, the control system 110 is mounted on a vehicle 200. The vehicle 200 in this embodiment is a wheeled vehicle such as a car, but it will be understood that the control system 110 can be used for other types of land vehicles and water vehicles operating in speed limit controlled waterways.

[0037] Referring to FIG. 1 , the control system 110 is communicatively coupled to a sensor unit 120 associated with the vehicle 200. The sensor unit 120 in this embodiment has an optical camera with a field of view extending forward in front of the vehicle 200. The sensor unit 120 has one or more optical cameras, for example a stereo camera. Alternatively or additionally, the sensor unit 120 may be comprised of other types of sensors, such as a radar system or a LIDAR system, to capture a representation of the area in front of the vehicle 200. The sensor unit 120 in this embodiment is located behind a rearview mirror (not shown) provided on an upper portion of the front windshield of the vehicle 200. Other mounting locations are possible. For example, the sensor unit 120 may be provided behind or within a front grill of the vehicle 200. The control system 110 is configured to receive image data 125 from the sensor unit 120 indicative of at least the area in front of the vehicle 200.

[0038] The control system comprises a processing means 111 and a storage means 114. The processing means may be one or more electronic processing devices 111. The storage means 114 may be one or more storage devices 114. The memory means 114 is electrically coupled to the processing means 111. The memory means 114 is configured to store instructions and the processing means 111 is configured to access the memory means 114 and execute the instructions thereon.

[0039] As shown in Fig. 3, the vehicle 200 is positioned on a road, hereafter referred to as a main road PR. The control system 110 is configured to receive digital map data 140 indicative of the main road PR. The digital map data 140 may be stored in a memory 114 accessible to the control system 110 or may be transmitted to the control system 110, for example from a remote map server, as the vehicle 200 travels along the main road PR. The digital map data 140 comprises an indication of a speed limit on a map associated with a segment of the main road PR on which the vehicle is located. For example, the digital map data 140 may indicate that the vehicle 200 is located on a segment of the main road PR having a speed limit of 40 km per hour. The main road segment may be defined between a first node and a second node of the map data. The speed limit on the map may be utilised by one or more further vehicle control systems 130. The vehicle control system 130 may include a cruise control system 130 arranged to operatively regulate the speed of the vehicle 200. Alternatively or additionally, the further vehicle control system 130 may have a speed limit indication system or a driver warning system for alerting the driver of a speed limit, or for alerting the driver when the vehicle exceeds the speed limit.

[0040] In some examples, the digital map data 140 may be inaccurate. For example, the digital map data 140 may be out of date or may have temporary speed limit restrictions, for example due to road construction. Thus, the control system 110 is configured to identify a traffic sign 300 in the received image data 125 and determine a sign speed limit indicated by the traffic sign 300. The control system 110 may then output to one or more further vehicle control systems 130 a sign speed limit signal 135 indicating the sign speed limit, i.e. the speed limit of the road segment communicated or indicated by the road sign. In the embodiment shown in FIG. 3, the control system 110 may output a sign speed limit signal 135 indicating the determined 30 km / h speed limit. The sign speed limit signal may thus override or take precedence over the map speed limit in situations where the sign speed limit does not match the map speed limit. The further control system 130 may then utilize the updated example 30 km / h speed limit instead of the 40 km / h indicated by the digital map data.

[0041] In this manner, the sign speed limits indicated by the traffic signs 300 detected by the sensor unit 120 can override the map speed limits, and a vehicle control system 130, such as the cruise control system 130, may be able to take into account recently changed or temporary speed limits that are not yet reflected in the digital map data 140. Additionally, the sign speed limits indicated by the traffic signs 300 can provide speed limit information when map speed limit information is not available, for example when the vehicle is on a road segment that does not exist in the digital map data 140.

[0042] However, not all traffic signs detected by the sensor unit 120 are associated with the vehicle 200. A traffic sign 300 may be defined as associated with the vehicle 200 if it is associated with a main road PR, i.e., on the road, on which the vehicle is located.

[0043] 4A and 4B show two examples of a traffic sign 300 that is not associated with a vehicle 200. The traffic sign 300 may be associated with another road that is adjacent to the main road PR, so that the road sign associated with the other road is visible to the sensor unit 120. For example, the traffic sign 300 may be associated with a side road SR. Any road that is separate from the main road may hereafter be referred to as a side road SR. The side road SR may be any road on which no vehicle is located. In FIG. 4A, the side road SR is a road that branches off from the main road PR. The side road SR may be a road that intersects with the main road or branches off from the main road PR at a branch point such as a roundabout or rotary. In some examples, the side road SR may be a road that does not border the main road at all. In FIG. 4B, the side road SR is a separate road that is substantially parallel to the main road.

[0044] 4A and 4B, a traffic sign 300 may be detected by the control system 110 of the vehicle 200 traveling on the main road PR. However, each illustrated traffic sign 300 is associated with a side road SR, not the main road PR. Thus, if the control system 110 outputs a signed speed limit signal indicating a 30 km / h speed limit, this may erroneously override the correct 40 km / h speed limit for the main road PR as indicated by the digital map data, causing the vehicle system to unnecessarily adjust control of the vehicle 200.

[0045] An embodiment of the control system 110 is thus adapted to determine, at the time the traffic sign 300 is detected by the sensor unit 120, whether the traffic sign 300 is associated with the vehicle 200. By associated with the vehicle 200, we mean whether the traffic sign 300 is associated with a main road PR. If the traffic sign 300 is determined not to be associated with the vehicle 200, for example by being associated with a side road SR, the control system 110 may inhibit or refrain from generating the signed speed limit signal 135.

[0046] A method 500 of operation of the control system 110 according to an embodiment of the invention is shown in FIG.

[0047] The method 500 includes a block 510 for receiving image data indicative of an environment of the vehicle 200. The control system 110 may be configured to receive image data 125 from the sensor unit 120, as discussed. The image data 125 may be indicative of an area ahead of the vehicle 200 and may include a representation of one or more traffic signs 300 present in the image data.

[0048] The method 500 comprises a block 520 of identifying at least one traffic sign 300 in the image data 125. The traffic sign 300 may be identified by processing the image data 125 to search for a predefined shape, color and / or texture in the image that matches known traffic sign criteria, as will be appreciated by those skilled in the art. Block 520 further includes determining a sign speed limit indicated by the traffic sign 300. The speed limit may be determined using any known image processing technique, such as, for example, using the outline of a pictogram. For example, block 520 may include identifying one traffic sign 300 in the image data 125 that indicates a sign speed limit of 30 km / h.

[0049] The method 500 includes a block 530 of determining the relevance of the signed speed limit to the vehicle 200. Determining the relevance may include classifying the speed limit as one of relevant or not relevant to the vehicle 200. The determined relevance may be indicative of the likelihood that the traffic sign is relevant to a major road PR. The speed limit may be classified as not relevant if it is determined that the traffic sign is more likely to apply to a side road SR.

[0050] The signed speed limit may be determined as relevant or not relevant depending on the location of the traffic sign 300 relative to road features in the environment. In different embodiments, the road feature may be one or more of an edge of a main road, an entrance stub to a side road, or a further traffic sign, as described. The location of the traffic sign relative to the road features may indicate that the traffic sign may be associated with a side road SR.

[0051] 6, according to some embodiments, block 530 comprises identifying a road edge 600 of the main road PR. The road edge 600 may be identified in the image data 125, for example, by identifying a contrast and / or color change in the image data 125 that may be indicative of the road edge 600. For example, a transition or boundary between a road surface that may be relatively smooth (e.g., defined by asphalt, concrete or other surface treatment material) and an adjacent surface that is relatively rough (e.g., composed of one or more of grass, mud, gravel, sand and snow) may be identified. In other examples, the road edge 600 may be identified relying on road markings identified on the main road PR, or physical divisions or boundaries such as curbs.

[0052] The control system may then be configured to determine a distance 610 between the road edge 600 and the traffic sign 300. The distance may be a lateral distance 610, i.e. a distance substantially perpendicular to the road edge 600. The distance 610 may be determined from the image data 125 by determining a lateral distance 630 between the vehicle 200 and the road edge 600 and a lateral distance 620 between the vehicle 200 and the traffic sign 300. Each determined distance 620, 630 may be inferred from the size and / or position of the traffic sign 300 and the road edge 600 in the image data 125 using known image processing techniques.

[0053] In block 530, the control system 110 may determine that a speed limit is not associated with the vehicle if the determined lateral distance 610 between the road edge 600 and the traffic sign 300 meets a predefined criterion. The predefined criterion may be that the distance 610 is equal to or greater than a predefined threshold. The predefined threshold may be defined depending on where the vehicle 200 is geographically located, for example, depending on which country the vehicle 200 is located in. Local regulations may define a standardized range of distances between the traffic sign 300 and the road edge 600. If the distance 610 is greater than the upper limit of the standardized range, it may be determined that the traffic sign 300 is too far from the road edge 600 and is therefore not associated with the main road PR.

[0054] According to some embodiments, the road feature may constitute an entrance stub to a side road SR. With reference to FIG. 7, the entrance stub 700 may be an area where the side road SR merges with the main road PR. The entrance stub 700 may be a turn-off, an intersection, a slip lane, or any other junction. In some embodiments, block 530 may include identifying the entrance stub 700 in the image data 125. For example, the entrance stub 700 may be identified in the image data 125 by identifying a gap or a branch in the road edge 600. Alternatively, or additionally, the control system 110 may rely on the digital map data 140 to identify the location of the entrance stub 700 relative to the vehicle 200. The digital map data 140 may indicate the location of a node where a segment of the side road SR branches off from a segment of the main road PR on which the vehicle 200 is located.

[0055] In block 530, the control system 110 may determine a stub distance 710 from the traffic sign 300 to the entrance stub 700. The location of one or more boundaries 705, 706 that define the edges of the entrance stub 700 may be identified from the image data 125 or the digital map data 140. The stub distance 710 may then be determined as the distance between the traffic sign 300 and the boundary 705, 706 that is closest to the traffic sign. In the illustrated embodiment, the traffic sign 300 is located after the entrance stub 300 along the main road PR with respect to the direction of travel of the vehicle 200, and the closest boundary is the boundary 705. However, if the traffic sign 300 is located before the entrance stub 700, the closest boundary to the traffic sign 300 may be the boundary 706. According to some embodiments, the stub distance 710 may be defined as the distance from the traffic sign 300 to an alternative point on the entrance stub 700, for example, the midpoint of the entrance stub 700.

[0056] The digital map data 140 may indicate a map speed limit associated with the side road SR. In block 540, the control system 110 may determine whether the map speed limit associated with the side road matches the posted speed limit. If the map speed limit associated with the side road matches the posted speed limit, this may indicate that the traffic sign 300 is associated with the side road SR and therefore not associated with the vehicle 200.

[0057] To more accurately confirm that the traffic sign 300 is associated with the side road SR, the control system 110 may be configured to determine whether the stub distance 710 is less than a predetermined stub distance threshold, i.e., whether the traffic sign 300 is located sufficiently close to the entrance stub 700. If the stub distance 710 is less than the stub distance threshold and the map speed limit associated with the side road matches the sign speed limit, the control system 110 may determine that the traffic sign 300 is associated with the side road SR and therefore not associated with the vehicle 200.

[0058] 8 , according to some embodiments, the control system 110 may be configured to determine that a traffic sign 300 is not associated with the vehicle 200 depending on its position relative to a further traffic sign 800. If the first traffic sign 300 and the second traffic sign 800 are each identified by the control system 110, then in block 530 the control system 110 may determine whether the first traffic sign 300 and the second traffic sign 800 straddle a side road SR.

[0059] In FIG. 8, the first traffic sign 300 and the second traffic sign 800 are shown straddling the side road SR. By straddling the side road SR, it is meant that the first traffic sign 300 and the second traffic sign 800 are located on opposite sides of the side road SR and are generally aligned along an axis perpendicular to the side road SR. A pair of traffic signs 300, 800 as shown may be referred to as a gated sign. Such gated signs are often used to indicate speed limit changes, and by providing traffic signs on both sides of a road, drivers can easily infer which road the traffic signs relate to. By determining that the first and second traffic signs 300, 800 straddle the side road, it may be inferred that each of the first and second traffic signs 300, 800 is associated with the side road SR and therefore not associated with the vehicle 200.

[0060] The first traffic sign 300 and the second traffic sign 800 are determined to span the side road SR if one or more spanning criteria are met. The first spanning criterion may be that the first traffic sign 300 and the second traffic sign 800 indicate the same speed limit. The second spanning criterion may be that the first traffic sign 300 and the second traffic sign 800 are each located on the same side of the vehicle 200. The third spanning criterion may be that the distance between the first traffic sign 300 and the second traffic sign 800 is equal to or less than a threshold, i.e., the traffic signs 300, 800 are sufficiently close to each other.

[0061] The methods described above for determining the relevance of a traffic sign 300 to a vehicle 200 may be performed alone or in combination. An exemplary operation of the control system 110 during block 530 according to an embodiment is shown in Figure 9. In the illustrated embodiment, the control system 110 performs each of the methods described above in sequence to determine the relevance of a traffic sign 300 to a vehicle 200.

[0062] In step 531, it is determined whether the posted speed limit matches the speed limit on the map associated with the side road SR. If the posted speed limit matches the speed limit on the map, it is determined in step 532 whether the stub distance 710 to the entrance stub 700 of the side road SR is less than a threshold. If the stub distance 710 is less than the stub distance threshold, it is determined that the traffic sign 300 is associated with the side road SR at the stub entrance and therefore not associated with the vehicle. If it is not determined that the traffic sign 300 is associated with the stub entrance 700, the control system 110 proceeds to step 533. In step 533, it is determined whether the distance 610 between the traffic sign 300 and the road edge 600 of the main road is greater than a threshold. If the distance 610 is greater than the threshold, it may be determined that the traffic sign 300 is not associated with the vehicle 200. If the traffic sign is sufficiently close to the road edge 600, the control system 110 proceeds to step 534. In step 534, it is determined whether the traffic sign 300 straddles a side road SR which has a further traffic sign 800. If it is determined that the traffic sign 300 forms part of a side road straddling pair, then the traffic sign 300 is determined to not be associated with the vehicle 200. If it is determined in any of steps 531-534 that the traffic sign 300 is not associated with a side road SR or is not too far from the road edge 600, then it is determined that the traffic sign 300 is likely associated with a main road PR, and the traffic sign 300 may be determined to be associated with the vehicle 200. It will be appreciated that in some embodiments, steps 531 through 534 may be performed in an alternative order. Additionally, in some embodiments, one or more of steps 531 through 534 may be omitted. For example, in one embodiment, in block 530, the control system may perform only step 533, and the traffic sign 300 may be determined to be relevant if it is sufficiently close to the road edge 600.

[0063] The method 500 includes a block 540 for selectively generating a sign speed limit signal indicative of the speed limit of the traffic sign 300. The sign speed limit signal may be selectively generated depending on the traffic sign 300 determined to be associated with the vehicle 200 in block 530. If the traffic sign 300 is not associated with the vehicle, the control system 110 may decide not to generate a signal in block 540. Alternatively, the control system 110 may generate a map speed limit signal indicative of the map speed limit of the major road PR depicted in the digital map data 140. The method 500 includes a block 550 for outputting the generated signal to one or more further vehicle control systems 130. The one or more vehicle control systems 130 may comprise a cruise control system, a display or warning system for informing the driver of the speed limit.

[0064] Thus, by implementing method 500, the traffic sign recognition system can override the speed limit retrieved from the digital map data only if the identified traffic sign is determined to be associated with the vehicle. Traffic signs associated with side roads on which the vehicle 200 is not traveling are effectively filtered out, potentially mitigating erroneous adjustments in the speed limit input to further vehicle systems 130, such as the cruise control system 130.

[0065] Referring to Fig. 10, a simplified example of a control system 110 as may be adapted to perform the methods described herein is illustrated. The control system 110 comprises one or more controllers 1000 and is configured to generate a speed limit signal 135 for controlling the vehicle 200. The control system 110 is configured to receive image data 125 indicative of the vehicle's environment from one or more imaging devices 120 associated with the vehicle. The control system 110 is configured to determine, depending on the image data 125, a speed limit indicated by a traffic sign 300 and a position of the traffic sign relative to road features in the environment. The control system 110 is configured to determine, depending on the determined position of the traffic sign 300 and the determined position of the vehicle 200, a relevance of the speed limit to the vehicle, selectively generate a sign speed limit signal 135 indicative of the speed limit depending on the determined relevance, and output the selectively generated signal 135 to at least one vehicle control system 130.

[0066] Alternatively, each controller 1000 may constitute a control unit or computing device having one or more electronic processors (e.g., microprocessors, microcontrollers, application specific integrated circuits (ASICs), etc.), and may constitute a single control unit or computing device, or it is to be understood that alternatively, different functions of each controller 1000 may be embodied or hosted in different control units or computing devices. As used herein, the terms "controller", "control unit", or "computing device" are understood to include single controllers, control units, or computing devices, as well as multiple controllers, control units, or computing devices that collectively operate to provide the necessary control functions. A set of instructions may be provided that, when executed, causes the controller 1000 to perform the control techniques described herein, including some or all of the functions required for the methods described herein. The set of instructions may be embedded in said one or more electronic processors of the controller 1000, or alternatively, the set of instructions may be provided as software executed in the controller 1000. The first controller or control unit may be implemented in software executed on one or more processors. The one or more other controllers or control units may be implemented in software running on one or more processors, optionally the same processor or processors as the first controller or control unit. Other arrangements are also useful.

[0067] 10, the or each controller 1000 comprises at least one electronic processor 111 having one or more electrical input(s) 112 for receiving one or more input signals and one or more electrical output(s) 113 for outputting one or more output signals. The or each controller 1000 further comprises at least one memory device 114 electrically coupled to the at least one electronic processor 111 and having instructions 115 stored thereon. The at least one electronic processor 111 is configured to access the at least one memory device 114 and execute the instructions 115 thereon.

[0068] The, or each, electronic processor 111 may be comprised of any suitable electronic processor (e.g., microprocessor, microcontroller, ASIC, etc.) configured to execute electronic instructions. The, or each, electronic memory device 114 may be comprised of any suitable memory device and may store thereon or thereon various data, information, threshold(s), look-up tables or other data structures, and / or instructions. In one embodiment, the memory device 114 has information and instructions for software, firmware, programs, algorithms, scripts, applications, etc. stored thereon or thereon that may govern all or a portion of the methodologies described herein. The, or each, electronic processor 111 may access the memory device 114 and execute and / or use the or those instructions and information to perform or execute some or all of the functionality and methodologies described herein.

[0069] At least one memory device 114 may include a computer readable storage medium (e.g., non-transitory or non-transient storage medium), which may include any mechanism for storing information in a form readable by a mechanical or electronic processor / computer, including, but not limited to, magnetic storage media (e.g., magnetic storage media (e.g., floppy disks); optical storage media (e.g., CD-ROM); magneto-optical storage media; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM ad EEPROM); flash memory; or electrical or other types of media for storing such information / instructions.

[0070] The exemplary controller 1000 has been described as including at least one electronic processor 111 configured to execute electronic instructions stored in at least one memory device 114 that, when executed, cause the electronic processor(s) 111 to perform methods as described herein. However, the present invention is not limited to being implemented in the manner of programmable processing devices, and it is contemplated that at least some, and in some embodiments all, of the functionality and / or method steps of the present invention may likewise be implemented in the manner of non-programmable hardware, such as in the manner of non-programmable ASICs, Boolean logic circuits, and the like.

[0071] It will be understood that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. 1. A control system for generating a speed limit signal for a vehicle, the control system including one or more controllers, the one or more controllers comprising: receiving image data indicative of an environment of the vehicle from one or more imaging devices associated with the vehicle; determining speed limits indicated by traffic signs and positions of the traffic signs relative to road features in the environment in dependence on the image data; determining the relevance of the speed limit to the vehicle dependent on the determined location of the traffic sign and the determined location of the vehicle; generating a signed speed limit signal indicative of said speed limit in dependence on said determined association; A control system configured to output the generated posted speed limit signal to at least one of the vehicle control systems.

2. The one or more controllers: receiving digital map data including an indication of a speed limit on a map associated with a road segment on which the vehicle is located; 2. The control system of claim 1, configured to generate an on-map speed limit signal indicative of the on-map speed limit if it is determined that the speed limit indicated by the traffic sign is not relevant, and output the on-map speed limit signal to the at least one vehicle control system.

3. 3. The control system of claim 2, wherein if the speed limit indicated by the traffic sign is determined to be relevant, the one or more controllers are configured to preferentially output the posted speed limit signal.

4. The control system of any of claims 1-3, wherein determining the position of the traffic sign includes determining a distance from the traffic sign to the road feature.

5. The control system of claim 4 , wherein the one or more controllers are configured to determine the relevance of the speed limit depending on whether the distance meets a predetermined criterion.

6. the road features include an edge of a road on which the vehicle is located; 6. The control system of claim 4 or claim 5, wherein determining the location of the traffic sign comprises determining a distance from the traffic sign to an edge of the road.

7. 7. The control system of claim 6, wherein the one or more controllers are configured to determine that the speed limit is not relevant to the vehicle if the determined distance to the edge of the road is greater than a predetermined threshold.

8. the at least one road feature includes a side road entrance stub; The control system of any of claims 1-5, wherein the one or more controllers are configured to determine the position of the traffic sign by determining a stub distance from the traffic sign to an entrance stub of the side road.

9. The one or more controllers: receiving digital map data indicating speed limits on the map associated with the frontage road; 9. The control system of claim 8, configured to determine that the speed limit is irrelevant if the speed limit matches a speed limit on the map associated with the side road and the stub distance is less than a predetermined stub distance threshold.

10. A control system according to any preceding claim, wherein the road features include a further traffic sign indicating the speed limit.

11. 11. The control system of claim 10, wherein the one or more controllers are configured to determine whether the traffic sign and the further traffic sign straddle a side road depending on a position of the traffic sign relative to the further traffic sign.

12. 12. The control system of claim 11, wherein the one or more controllers are configured to determine that the speed limit is irrelevant if the traffic sign and the further traffic sign straddle a side road.

13. The one or more controllers: an electrical input for receiving an electrical signal indicative of the image data; an electrical output for outputting an electrical signal indicative of the speed limit; A control system as claimed in any preceding claim, comprising one or more electronic processors for operatively executing computer readable instructions for determining the relevance of said speed limits.

14. A vehicle including a control system according to any one of claims 1 to 13.

15. 1. A computer-implemented method for generating a speed limit signal for control of a vehicle, comprising: receiving image data indicative of an environment of the vehicle from one or more imaging devices associated with the vehicle; determining speed limits indicated by traffic signs and positions of the traffic signs relative to road features in an environment in dependence on the image data; determining the relevance of a speed limit to the vehicle depending on the determined position of the traffic sign and the determined position of the vehicle; selectively generating a signed speed limit signal indicative of said speed limit dependent on said determined association; and outputting the selectively generated posted speed limit signal to at least one vehicle control system.

16. A computer readable medium containing computer software that, when executed, causes the computer to perform the method of claim 15.

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