Collision avoidance system and method of detecting overpass locations using data fusion

A collision avoidance system adapted for use with a vehicle, and a method of modifying a first warning assessment algorithm of the system to reduce false alerts caused by overpasses, and maintain sufficient warning distances are presented, wherein the system includes at least one sensor operable to detect an object location, a locator device operable to determine the current position coordinates of the vehicle, a map database presenting a plurality of overpass locations ahead of the vehicle, and an electronic control unit operable to execute a second algorithm, if the detected object location generally matches an overpass location, and in a preferred embodiment, a third algorithm, if the detected location does not match an overpass location, such that the third algorithm is executable over a shorter period than the second, and the second algorithm is executable over a shorter period than the first.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to vehicular collision avoidance and mitigation systems, and more particularly, to a digital map and sensory based collision avoidance system that utilizes data fusion to identify overpasses and modify a threat assessment algorithm, so as to maintain sufficient warning distances, and reduce false alerts.

2. Background Art

A prevailing concern in current implementations of collision avoidance and warning systems in vehicles is that they typically present a significant number of false alerts (i.e. warnings of imminent collisions with objects that are not in fact within the vehicle path). This concern is especially perpetuated by the proximity of stationary objects, the current limitations in accurate prediction of forward path, and the inability of the radar to discriminate between objects present at different elevations. False alerts in conventional systems are often caused by overpasses, mailboxes on the roadside, staled vehicles, etc.

Overpasses are of particular concern for various reasons. First, they are present in great numbers on interstate highways and other thoroughfares. Second, they are typically found traversing the path of thoroughfares having a relatively high speed limit. Third, they are difficult to distinguish from in-path objects that present true potential collisions. Fourth, and perhaps most concerning, current overpass detection algorithms that analyze the signal-strength trend of the approaching object are generally unable to provide sufficient warning distances, when a true potential collision, and not an overpass, is determined.

With respect to the later, once an object is detected at an initial threshold distance, the trend in the radar return signal strength over a plurality of diminishing distances (see,FIGS. 1 through 3a) is assessed to determine the signature signal pattern. Due to the necessity to obtain trend data, however, overpass determination under this and similar methodology often results in the warning being issued at shorter “definite detection” distances, sometimes as short as 60 meters. It is appreciated that a vehicle traveling at the speed of 70 mph (31 meters/sec) requires a warning distance of 150 meters or more in order to allow the vehicle to be stopped before reaching the object (assuming a 1-sec reaction time, and a 0.4 g deceleration).

Thus, to be effective a collision avoidance system must provide reliable and efficient warning distances to the operator, and, therefore, be capable of timely distinguishing false concerns caused by overpasses from potential collisions caused by true in-path objects.

SUMMARY OF THE INVENTION

Responsive to these and other concerns caused by conventional collision avoidance and mitigation systems, the present invention presents an improved collision avoidance system that utilizes data fusion to more rapidly and accurately determine the presence of overpasses.

A first aspect of the present invention concerns a collision avoidance system adapted for use with a host vehicle, and by an operator. The system includes at least one sensor configured to detect an object located a minimum threshold distance from the vehicle, so as to determine a detected object location, and a map database including a plurality of intersecting links, and denoting overpass locations. The system further includes a locator device communicatively coupled to the map database, and configured to detect the current position coordinates of the vehicle within the map database. Finally, the system includes an electronic control unit communicatively coupled to the sensor, database, and device, and programmably configured to autonomously execute a warning assessment algorithm, compare the detected object location with the overpass locations, so as to determine whether the detected object location is generally at an overpass location, modify the warning assessment algorithm, when the detected object location is at a general overpass location, and cause a warning perceivable by the operator to be generated or a mitigating action to be initiated, when the execution of the algorithm detects a potential collision.

A second aspect of the present invention concerns a method of modifying a first warning assessment algorithm of the system, so as to reduce false alerts caused by overpasses, while maintaining sufficient warning distances. The method generally begins with the steps of autonomously determining the current position coordinates, and heading of the vehicle, and retrieving the position coordinates of at least one overpass location within a predetermined vicinity ahead of the vehicle from a database. Next, an approaching object at least a minimum threshold distance from the vehicle is detected, and the detected position coordinates of the object are determined. The detected position coordinates are compared to the position coordinates of said at least one overpass location from the database. Finally, a second algorithm is executed, if the detected coordinates generally match the position coordinates of a database overpass location, and a third algorithm is executed, if the detected coordinates do not match the position coordinates of a database overpass location, wherein said third algorithm is executable over a shorter period than the second, and the second algorithm is executable over a shorter period than the first.

It will be understood and appreciated that the present invention provides a number of advantages over the prior art, including, for example, further utilizing pre-existing in-vehicle navigation and map database systems, enabling more efficient, reliable, and accurate overpass determination, allowing the full radar range to be utilized for warning or mitigation, and adding redundancy where a plurality of overlapping sensors are utilized. Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment(s) and the accompanying drawing figures.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

As shown inFIGS. 4 and 5, the present invention concerns a collision avoidance system10adapted for use with a traveling host vehicle12and by an operator14. In general, the system10fuses sensory (typically a radar subsystem) and database data to determine the presence of an overpass16within the forward vehicle path. An electronic control unit (ECU)18is programmably equipped to perform the various algorithms and functions described herein, and may consist of a single unit or a plurality of communicatively coupled intermediate or component control units configured to manipulate the input data prior to delivery to a central unit. As such, it is appreciated that the host vehicle12includes sufficient electrical and software functionality to effect the intended benefits, wherein said capabilities are readily determinable by one of ordinary skill in the art, and therefore, will not be further discussed.

The system10includes an in-vehicle navigation system and updateable map database20that is communicatively coupled to the ECU18. As shown inFIG. 6, the preferred vehicle map database20comprises a plurality of interconnected links (i.e. groupings of three-dimensional map points that represent thoroughfares)22, and preferably denotes pre-determined above-grade or overpass locations24where two or more link22traverse each other at different grades. The area map, links22, and overpass location24are preferably shown on a map display20aperceivable by the operator14. More preferably, each link22further presents traffic condition data, such as a maximum speed limit, or wet pavement conditions that could be utilized to improve warning determination.

The system10also includes a locator device26configured to locate the absolute position (e.g., latitude, longitude, and height) and preferably the heading of the host vehicle12. As shown inFIGS. 4 and 5, the preferred locator device26includes a Global Positioning System (GPS) receiver28communicatively coupled to orbiting satellites, and a dead-reckoning system. Alternatively, the locator device26may utilize a network of cellular telephones, or a system using radio-frequency identification (RFID). The receiver28is communicatively coupled to the map database20and cooperatively configured to determine the current position coordinates, Cp, of the vehicle12on the map display20a, as shown inFIG. 6.

As previously mentioned, the system10further includes at least one sensor30configured to detect the in-path object or overpass16at a minimum threshold distance. The sensor30may employ any suitable technology, including vision/camera, infrared, radar, lidar, or laser technology. For example, a long-range radar detector capable of detecting a single lane overpass from a minimum threshold distance of at least 150 meters, and more preferably 250 meters, may be utilized.

As described inFIGS. 7 and 9, the map database20, locator device26, and sensor30are communicatively coupled and contribute input data to a data fusion module autonomously performed by the ECU18. The ECU18fuses the input data to determine whether an overpass location is cross-corroborated by the individual sensors30and map database20. If the data fusion module determines a corroborated overpass location, then the system10is further configured to cause to be generated a warning perceivable by the operator14, and/or initiate a mitigating maneuver, when the threat assessment algorithm is satisfied. The following first and second embodiments of the invention exemplarily present two sensor/map database configurations that may be utilized:

1. Radar and Map Based Determination

In a first embodiment, a preferably pre-existing in-vehicle navigation system map database20is combined with a conventional radar-based overpass detection system. Once an object16is detected by the sensor30, a sensor-detected range and relative object location are determined. The ECU18, locator device26, and map database20are cooperatively configured to search the forward map preview of the map database20for overpass locations24in the general vicinity (e.g., within 50 meters) of the detected object location. If a matching overpass location24is not found in the forward map preview, the preferred system10issues the warning immediately, so that sufficient distance separates the vehicle12from the object16.

If, however, a matching overpass location24is found in the forward map preview, then the radar signal trend analysis module uses a lower threshold to look for a signature trend of diminishing amplitude (i.e. decay) of the radar return signal. That is to say, the radar signal analysis in this configuration may be performed over a period shorter than conventional assessment periods (e.g., a sample of two return signal strengths versus a sampling of three), so that the warning is issued to the vehicle12at a greater distance from the object16. For example, if the trend presents a significant decay rate over a sample of Xo. . . Xnstrengths, wherein the rate is taken from the differences between progressively succeeding strengths (i.e. Xn-Xn-1, etc.), then the object16is deemed an overpass; but if a significant decay trend is absent (e.g., the differences are positive), the object is deemed in-path, and a warning is issued, and/or mitigation action, such as actuating the braking module32of the vehicle12, is initiated. It is appreciated that, despite a matching overpass location determination, radar-trend analysis is necessary to detect in-path objects that are located under the overpass.

As shown inFIG. 7, a preferred method of operation in the first embodiment includes a first step100, wherein a map database20including a plurality of links is presented at a host vehicle12. At a step102, the current vehicle position is determined using a GPS navigation subsystem, and links in the vicinity of the vehicle12are retrieved from the map database20. Next, at a step104, the forward travel direction of the vehicle12is determined, and links in the immediate forward travel path of the vehicle12are further derived from the map database20. At a step106, the geometry of the derived links is determined from their geographic points, and intersection points (based on x,y coordinate values) are identified. At a step108, intersection points are classified as either “at grade” or “overpass” based on the grade level (i.e., z coordinate value) provided at the points. Alternatively, it is appreciated that steps100,106and108may be combined at step100, in that the overpass locations24may be pre-identified and tabulated in the database.

At a step110, a radar subsystem detects an object, determines a detected object location, and communicates it to the data fusion module. At a step112, the module compares the detected object location to the overpass locations24, such that if the detected object location does not correspond to a map-identified overpass location24, then, at a step114a, the detected object16is deemed in-path without considering signal strength trend data, and the warning is caused to be generated or mitigation is initiated. If, however, the detected object location does correspond to an overpass location24, then, at step114b, the radar subsystem and ECU18proceed with the process of analyzing the signal strength trend data of the object16over a truncated period, to decide whether it is an overpass. At a step116, the trend is compared to a threshold to determine whether it presents a true in-path object. If the threshold is met, then the object16is deemed in-path, and a warning is caused to be generated, or a mitigating maneuver is caused to be initiated as per114a; else the method returns to step102.

In a second preferred embodiment, the ECU18fuses input from a plurality of different sensors30and the map database20during overpass determination, to add redundancy and capability. In the illustrated embodiment shown inFIG. 8, for example, a vision or camera based sensor30b, operable to detect the signature pattern of an approaching overpass, is utilized in addition to a radar subsystem30a. The radar subsystem30ais further configured to cooperatively determine track data for a plurality of objects and to analyze the data to determine whether a moving object16mhas passed through the location of a stationary object track. Similar to the first embodiment, the in-vehicle navigation system and map database20is utilized to determine whether an overpass location24exists that matches a sensory detected object location.

More particularly, the vision sensor30bis configured to determine whether an overpass signature pattern is present, wherein, for example, the pattern may include the detection of a wide object across the field of view, a horizontal object relative to the ground plane, higher light intensity above the object (during daytime), and/or lower light intensity below the object (during daytime). Alternatively, a reflective surface, or other indicia can be positioned on the overpass, so as to directly communicate its presence to the sensor30b. If an overpass signature pattern is determined, and/or the radar subsystem detects a moving object through a stationary track, then the map database20is consulted.

Referring toFIG. 9, a preferred method of performing the second embodiment of the invention starts at a first step200, where an object16is detected by a vision sensor30b, and its relative object location is determined. At a step202, the detected object is evaluated to determine whether an overpass signature pattern is present. If an overpass signature pattern is determined, correlated input data is communicated to a data fusion module, and the method proceeds to step204. If an overpass pattern is not determined, then the method returns to step200.

Concurrently, at a step200a, a radar subsystem30ais used to track a plurality of objects by determining their relative object locations over a period. At a step202a, the individual track data is examined to determine if there is a wide stationary object16that spans the width of the thoroughfare, and/or to detect the presence of a moving object16mthrough the stationary object location. If a moving object is found to have traversed the stationary object location, then the radar-detected stationary object16is deemed an overpass, and correlated input data is communicated to the data fusion module proceeding to step204; else, the radar subsystem returns to step200a.

At a step204, the data fusion module will combine overpass identified locations from each sensor30a,b, and more preferably, attribute a weighted factor to those overpass locations detected by both sensors. At a step206, the current position coordinates of the vehicle12are determined using a locator device26, and links in the vicinity of the vehicle12are retrieved from the map database20. From the current position coordinates, absolute position coordinates for the objects16,16mcan be determined from their relative positioning. Next, at a step208, the heading, and forward travel direction of the vehicle12are determined, and links in the vicinity of the forward travel path of the vehicle12are retrieved from the map database20. At a step210, the geometry of the retrieved roads is determined from their map points, and approaching intersection points therewith are identified. At a step212, intersection points are classified as either “at grade” or “overpass” based on the grade level indicia provided at the points. At step214, the overpass determined intersection points are communicated to the data fusion module, and at step216, compared to the sensor determined overpass locations.

Finally, at a step216a, if a sensor-detected overpass location does not correspond to a map-identified overpass location24, then the object16is deemed in-path and at-grade without considering signal strength trend data to eliminate the possibility that it is an overpass. In other words, where an detected overpass is not corroborated by the database20, the system10will immediately issue a warning, even if both sensors30a,bdetected an overpass location. If, however, a sensor-detected overpass location does correspond to a map database overpass location24, then the signal strength trend data is considered, at step216b, to determine whether the object is in-path at grade level, or out of the grade level path, or where detected by the vision sensor only, further analysis can be made to determine whether an in-path object pattern is also present.

The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments and methods of operation, as set forth herein, could be readily made by those skilled in the art without departing from the spirit of the present invention. The inventor hereby state his intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any system or method not materially departing from but outside the literal scope of the invention as set forth in the following claims.