1. Field of the Invention
This invention relates generally to a system and method for providing collision detection in a vehicle and, more particularly, to a system and method for providing collision detection in a vehicle that includes dynamically mapping the motion of objects around the vehicle in a defined area and determining whether the motion of the objects may cause a collision with the vehicle.
2. Discussion of the Related Art
Traffic accidents and roadway congestion are significant problems for vehicle travel. Current collision avoidance systems are typically based on radar/lidar technology where sensors on the vehicle detect moving objects around the vehicle and provide warning signals to the driver of a potential or impending collision, possibly even taking automatic evasive action.
Vehicular ad-hoc network based active safety and driver assistance systems allow a vehicle communications system to transmit messages to other vehicles in a particular area with warning messages about dangerous road conditions, driving events, accidents, etc. In these systems, multi-hop geocast routing protocols, known to those skilled in the art, are commonly used to extend the reachability of the warning messages, i.e., to deliver active messages to vehicles that may be a few kilometers away from the road condition, as a one-time multi-hop transmission process. In other words, an initial message advising drivers of a potential hazardous road condition is transferred from vehicle to vehicle using the geocast routing protocol so that vehicles at a significant distance away will receive the messages because one vehicle's transmission distance is typically relatively short.
Modern vehicles typically have GPS receivers that provide vehicle tracking and give the speed, direction and location of the vehicle. The above described vehicle communication systems can be combined with GPS location data to provide collision avoidance in vehicle systems in a simple manner. To enable such collision avoidance systems, vehicular ad hoc network based neighborhood awareness applications periodically transmit messages containing the kinematic state including position and velocity of the vehicle.
In accordance with the teachings of the present invention, a system and method are disclosed for dynamically mapping the position and speed of objects around a vehicle for collision avoidance purposes. The method determines the velocity of the vehicle in at least two orthogonal directions along with the position of the vehicle. From this information, a distance function map of the vehicle is created in a predefined area that includes a distance value at concentric locations from the vehicle. The distance function map is combined with distance function maps from all of the objects, including static objects located in terrain maps of the geographic area in which the vehicle is currently present, in the predefined area to determine whether a potential collision exists between the particular vehicle and any of the other objects.
Additional features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.
The following discussion of the embodiments of the invention directed to a system and method for determining the relative position and velocity of objects in a predefined region for collision avoidance purposes is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses.
As will be discussed in detail below, the present invention employs a process for dynamically identifying the relative position of vehicles in a predefined region based on their position and velocities for collision avoidance purposes, where the information is transmitted between the vehicles in the region so that appropriate action can be taken in the event of a potential collision.
As will be described in detail below, the present invention employs a level set algorithm (LSA) to identify the potential for a collision that uses a level set equation, namely:
Φt+u·∇Φ=0
where Φ is a distance value from an object, Φt is the rate of change of Φ with respect to time and u is the velocity of the object.
A predefined region is defined around a particular vehicle where each vehicle in the region uses the level set algorithm.
Using the LSA, each vehicle 12 generates an instantaneous distance function map based on a discrete finite volume grid in a given domain.
All of the distance function maps for all of the vehicles 12 in the defined region 10 are then combined into a composite map. Particularly, a composite distance function map is created using the LSA at each time iteration during the calculation with respect to the other vehicles 12 by minimization of the level set functions of all of the individual distance function maps.
At each sample time, the composite distance function map 28 will be updated as the vehicle 12 moves, and assuming that the vehicles 12 hold their current speed and direction, an estimate of the time for a potential collision between the vehicles 12 can be determined based on the dynamically changing distance contours provided by the composite distance function map 28 if such a potential for a collision exists. This information can then be used to provide warning signals or to take evasive action to prevent such a collision. For example, an optimization routine can be employed in conjunction with the LSA to suggest an optimal recovery path by analyzing the distance function contours of the neighboring vehicles 12.
Φini=√{square root over ((x−xini)2+(y−yini)2)}{square root over ((x−xini)2+(y−yini)2)}−ro
where xini and yini are the initial coordinates of the center of the object and ro is the radius defining the boundary of the object.
If the vehicle velocity has changed since the velocity has been assigned, then the new velocity is provided at box 54. The distance functions are then updated or calculated at box 56 to generate the distance function map, such as the one shown in
Φ(x, t+Δt)=Φ(x,t)+Δt*(u1∂Φ/∂x+v∂Φ/∂y)
As discussed above, each vehicle 12 determines its own distance function map using the level set algorithm. Once the distance function map for each vehicle 12 is provided at the box 56, then the algorithm constructs the composite distance function map 28 at box 58, such as shown in
Once the composite distance function map 12 is determined, then the minimum distance function value Φ from all of the distance function values Φ for each of the vehicles 12 is selected at each vehicle 12 and it is compared to a threshold distance function value Φcritical at decision diamond 60 to determine whether there is a potential for a collision for that particular vehicle 12 at box 62. If there is not a potential for a collision, then the algorithm returns to updating the distance function map by inputting a new velocity at the next sample time at the box 54. If the minimum distance function value Φ is less than the threshold distance function value Φcritical at the decision diamond 60 and there is a potential collision at the box 62, then the system will proceed to take some action to avoid the collision. The collision avoidance can be provided by any suitable collision avoidance system that may be applicable for the particular vehicle in response to the potential collision with whatever object is determined to being in the path of the particular vehicle.
The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.