Intersection collision avoidance with adaptable vehicle dimensions

Abstract

A method for avoiding a collision between a host vehicle (204) and a target vehicle (208), the method comprising: Locating current positions of the host vehicle (204) and the target vehicle (208) and defining a potential collision zone (200); Assuming the lengths of the target and host vehicles (204); Determine whether the assumed vehicle lengths are incorrect and, if incorrect, adjust the assumed lengths; Checking whether the target vehicle (208) is currently crossing the path of the host vehicle (204), taking into account the adjusted assumed lengths of the vehicles; Predicting the position of the host vehicle (204) at the time the target vehicle (208) is expected to reach the potential collision zone (200); Calculating a speed change value for the host vehicle (204) required for the host vehicle (204) to avoid a collision with the target vehicle (208) based on the adjusted assumed lengths; and Providing signals to the host vehicle (204) to perform the speed change for the host vehicle (204).

Description

GENERAL STATE OF THE ARTThe use of collision control / avoidance systems and methods to avoid collisions between two vehicles is widely used in the art. In particular, host vehicles are equipped with a number of sensors arranged at different locations, and these sensors generally determine the presence of vehicles in the vicinity of the host vehicle, and in particular those vehicles from which the risk of possible collisions may arise. Many collision control / avoidance systems rely on determining the precise relative positions of the host vehicle and the vehicle from which the collision risk is imminent and predicting their trajectories. The position coordinates of the host vehicle and the target vehicle are generally determined by vehicle-to-vehicle communication (V2V= Ve-to-Vehicle Communication) or radar or vision-based systems provided in the host vehicle. Then, signals for a predictive collision warning are provided to the occupant of the host vehicle.Many of these conventional systems use methods that sometimes do not take into account the length of the corresponding target vehicle in determining the probability of collision hazards and calculating the deceleration required for the host vehicle to avoid the collision. In some cases, for example, the vehicle from which a collision risk is imminent may drag another object or may be dragged by another vehicle. In such cases, the actual dimensions of the target vehicle used to assess the risk of collision may be invalid. In such judgments of the collision hazards, in projecting the trajectory of the host vehicle and the target vehicle, determining when the target vehicle would leave the potential collision zone is of particular importance and this determination is incorrect unless the actual dimensions for the host and target vehicles are used.Accordingly, there is a need for a method of judging the risk of collision that can function well with adaptive vehicle dimensions and particularly in cases where the vehicle from which a risk of collision is imminent pulls another vehicle.DE 10 2007 015 030 A1 describes a method and a device for predicting a driving behavior of an object located on a collision course with respect to the own vehicle. U.S. Pat. No. 6,650,984 B1 and U.S. Pat. No. 2004 / 0 019 420 A1 each disclose a pre-crash detection system for a source vehicle having a source vehicle length and a source vehicle width, which is coupled to a countermeasure system.SUMMARYThe present disclosure describes a method for assessing a risk of collision between a target vehicle and a host vehicle. The method is compatible with vehicle dimensions that are adaptive and uses the actual length of the target vehicle in calculations in assessing risk and takes into account cases where the target vehicle may drag an object.In one aspect, this disclosure provides a method of avoiding a collision between a host vehicle and a target vehicle. The method includes locating current positions of the host vehicle and the target vehicle and defining a potential collision zone by forward projecting their current trajectories and identifying the intersection of the trajectories. The method takes a value for the length of the target vehicle along its direction of travel and determines whether it is correct. If it is not correct, it adjusts the assumed length. Then, it is checked whether the target vehicle is currently crossing the path of the vehicle, and the position of the host vehicle at the time when the target vehicle is expected to reach the potential collision zone is calculated. The method then calculates, based on the adjusted assumed vehicle lengths, a speed change value required for the host vehicle to avoid a collision with the target vehicle. The method then provides signals to the host vehicle to perform the change in speed of the host vehicle.In one embodiment, the method further calculates the deceleration value required for the host vehicle to allow the target vehicle to safely pass and avoid the collision. A braking threat number is then calculated based on this deceleration value and signals are provided to the host vehicle based on the value of the braking threat number.Additional aspects, advantages, features and objects of the present disclosure will become apparent from the drawings and the detailed description of the illustrative embodiments, which are analyzed in connection with the following appended claims.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a flow chart showing the various steps involved in assessing the risk of collision and avoiding the collision between a host vehicle and a target vehicle, in accordance with the present disclosure. FIG. 2 illustrates the case where the target vehicle and the host vehicle are moving along oblique trajectory paths, and the various measurements and reference lines used by the collision risk assessment method of the present disclosure. FIG. 3 illustrates the case where the target vehicle and the host vehicle have mutually perpendicular trajectory.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTSThe following detailed description discusses aspects of the disclosure and the manner in which it may be practiced. However, the description is not a definition or limitation of the invention, as such definition or limitation is included only in the appended claims. While the best mode for carrying out the invention has been disclosed, those skilled in the art will recognize that other embodiments are possible for practicing or practicing the invention.The present disclosure relates to a pass-by-brake collision risk assessment algorithm that operates efficiently with adaptive vehicle dimensions. Similar methods may be used to extend a risk algorithm for accelerating to pass. For a better understanding of the disclosure, the following terms have the meanings / definitions given:Longitudinal direction: Denotes a direction which is substantially parallel to the direction of movement of a host vehicle.Transverse direction: Denotes a direction which is substantially perpendicular to the longitudinal direction.Target Vehicle: Any vehicle from which the risk of a potential collision with the host vehicle is imminent. In order for it to be at risk, the target vehicle must have at least one component of its speed along the transverse direction. Otherwise, no collision would occur.Potential Collision Zone: The area in which a collision would occur between the host vehicle and the target vehicle as the host vehicle and the target vehicle continue to move along their current trajectories.Further, the computations performed by the method of the present disclosure assume that the target vehicle and the host vehicle are moving at either constant speeds or constant accelerations.FIG. 1 shows the steps involved in the method 100 for estimating a potential collision risk between a host vehicle 204 and a target vehicle 208 and calculating a Break Three Number (BTN)) to allow the host vehicle to apply the brakes at a specific time to safely pass the target vehicle. FIG. 2 shows the projected trajectories of the host vehicle 204 and the target vehicle 208, the potential collision zone 200, and the various relevant measurements and reference lines used to perform the method disclosed in FIG. 1. For simplicity and brevity, the potential collision zone 200 as shown in FIG. 2 is referred to as "zone 200", the host vehicle 204 is referred to as "carrier 204", and the target vehicle 208 is referred to as "target 208", below.The method 100 of FIG. 1 will now be explained in conjunction with FIG. 2, wherein in step 102, the distance that the target 208 must travel from its current position in order to reach the zone 200 is calculated.This is represented by L TR. First, the potential collision zone 200 is defined between the host vehicle and the target vehicle. This is done by locating the current positions of the carrier 204 and the target 208 and projecting their trajectories forward along their directions of travel. The intersection of these projected trajectories defines the potential collision zone 200, as indicated in FIG. 2 by the shaded diamond. It is assumed that the host vehicle and the target vehicle continue to move along their current directions of movement before entering zone 200. Now, the distance L TR is mathematically calculated as follows:In the case where the target vehicle is moving perpendicular to the moving direction of the host vehicle (i.e., along the lateral direction), φ=0 as shown in FIG. 3, Equation (1) shortens: wherein: α=relative angle of movement of the target vehicle measured with respect to the path of the host vehicle, Φ=relative angle of movement of the target vehicle measured with respect to a line perpendicular to the path of the host vehicle, i.e. relative to the transverse direction L Long Rel= current relative longitudinal position of the front portion of the host vehicle relative to the proximal side of the target vehicle L LatRel= current relative transverse position of the center of the host vehicle relative to the center of the target vehicle x = additional distance beyond L Long Rel which the carrier must travel to enter the collision zone due to the inclination of the trajectory of the target vehicle relative to the trajectory of the host vehicle y = half of the lateral projection of the length of the target vehicle (T Length), measured on the plane perpendicular to the trajectory of the host vehicle, i.e. the side plane T Length= length of the target vehicle along its direction of movement H Width= width of the host vehicle perpendicular to its direction of movement L TR= The distance which the target must travel in order to reach the collision zoneIn step 104 of FIG. 1, the method 100 calculates the distance that the carrier 204 must travel to reach the potential collision zone (L HR). This is given by: For the case where the target 208 is moving perpendicular to the path of the carrier, φ = 0, andThe previously calculated value of 'x' is used in equation (2) to calculate L HRIn step 106, the method 100 calculates the time required for the target 208 to reach the zone 200. When the target 208 is moving at a constant speed V Target this time is given by using the first degree equation as follows:Otherwise, when the target 208 is moving at a constant acceleration, using the 2ndmooth equation: and therefore, where A Target= acceleration of the target vehicle and V Target= initial speed of the target vehicle at its current position and T TR= time required for the target vehicle to reach the potential collision zoneIn the case where Equation 3(a) or Equation 3(b) does not provide a positive result, depending on which is applicable, the paths of the target vehicle and the host vehicle would not cross and no collision would occur. This corresponds to the case where the host and target vehicles may move along parallel paths or when the target vehicle moves away from the host vehicle.In step 108, the method 100 determines whether the length of the target vehicle 208 (L TR), to be used for further computations, is correct. This check is made to take into account cases where the target 208 may, for example, drag another vehicle. This check may be done in any suitable manner, including using a vehicle-to-vehicle (V2V) communication system in which the target 208 is equipped with any on-board diagnostic to determine whether it is pulling something. This may be further due to the use of a smart traction system well known in the art that may generate signals when something is hung on the traction hitch of the target vehicle. Further, a vision-based system may cooperate with the V2V system and the case of drag may be determined by comparing the two estimates of the length of the target vehicle obtained from the V2V system and the vision-based system. In the case where the target 208 is not pulling an object, the method 100 uses the actual length of the target 208 (T Length) for further computations. Otherwise, in the case of towed, the method 100 uses an adjusted length for the target 208 given by the following equation: where: T Towed= towed object / vehicle lengthIn certain cases, based on knowledge of the dimensions of the most difficult object for which the target vehicle is designed to drag, an approximate value of T Towed may be used.In step 110, the method 100 calculates the distance that the target 208 must travel from its current position to clear the zone 200. As illustrated in FIG. 2, wherein:When the target vehicle is moving perpendicular to the path of the host vehicle, i.e., when φ=0, L TC= distance that the target 208 must travel to clear the zone 200.In the case where the target 208 is pulling an object 212, the length of the object 212 (T Towed) must be considered in the calculation of L TC. This is done using the adjusted value for the length of the target from equation (4). In this case:However, the values of L TR, Q & R would remain the same. L TR has already been calculated and its value can be used according to circumstances by Equation (1) or Equation 1(a), and substituted into either Equation (5), Equation 5(a), or Equation 5(b) to calculate L TC.In step 112, the method 100 calculates the time required for the target 208 from its current position to clear the zone 200. In the case where the target 208 is moving at a constant speed (i.e., there is no acceleration), the first degree equation is used to obtain this time as follows:Otherwise, when the target 208 is moving at the constant acceleration denoted by A target, the second equation of motion is used to calculate the time as follows:0,5 A Target T 2TC + V Target T TC+ L TC= 0; solving the quadratic equation;where time TC( T TC) = time required for the target 208 to clear the zone 200In step 114, the method 100 checks whether the destination 208 is currently crossing the path to the carrier 204. Specifically, the signs of L TR and L TC are compared by their values obtained from Equation (1) and Equation (5), and if these values have different signs, this means that the target 208 has reached but not cleared the zone 200. This concludes that the target 208 is currently crossing the path of the host vehicle.Next, in step 116, the method 100 predicts the position of the carrier 204 at the time the target 208 is expected to reach the zone 200. To do so, first the projected length of the target 208 along the path of the host vehicle is taken into account. As shown in Fig. 2, this projected length is given by u + v, where:Next, L LongRelMod= u+v+H Length+ L LongRel For the case where the target 208 is moving perpendicular to the path of the carrier 204, i.e., φ=0, where:L LongRelMod is the relative position of the rear portion of the carrier 204 longitudinally with respect to the distal side of the target 208, andL LongRel is the relative position of the forward portion of the carrier 204 longitudinally with respect to the proximal side of the target 208.Then, the relative position of the rear portion of the carrier 204 in the longitudinal direction with respect to the distal side of the target 208 is calculated for the time at which the target 208 is predicted to enter the zone 200. This is obtained using the second-degree equation of motion as follows: where V long Rel= current relative velocity of the carrier 204 along the longitudinal direction.If L Long Rel@TimeTR is negative, this means that the carrier 204 would traverse the zone 200 before the target 208 arrives there and no collision would occur. If L LongRel@TimeTR is positive, this means that the carrier 204 must apply the brakes to achieve deceleration to allow the target 208 to safely pass. This is referred to as a state of "braking to pass".In step 118, the method 100 calculates the deceleration required for the carrier 204 to allow the target 208 to safely pass in the pass braking state. This is done by first calculating the position of the forward portion of the carrier 204 relative to the proximal side of the target 208 for the time at which the target 208 is expected to clear the zone 200 (i.e., time TC). Using the second equation of motion: wherein: L Long Rel@TimeTC= Relative position of the forward portion of the carrier 204 in the longitudinal direction with respect to the proximal side of the target 208 at the time the target 208 is expected to clear the zone 200, and V long Rel= Current relative velocity of the carrier 204 along the longitudinal direction.Time TC has already been calculated beforehand and its value can be used either from Equation 8(a) or Equation 8(b) obtained previously and substituted into Equation (9) to obtain L Long Rel@TimeTC.Then, assuming that the carrier 204 immediately applies the brakes, the amount of deceleration required to avoid a collision and allow the target 208 to pass safely is given by the application of the second equation of motion as follows: wherein: ALongRequiredCrossingB2P= deceleration of the carrier 204 along the longitudinal direction required to allow the target 208 to pass safely in the state of braking to pass.In step 120, the method 100 checks whether the carrier 204 needs to accelerate to meet the target 208. This is done by checking the sign of the acceleration ALongRequiredCrossingB2P required for the state of braking to pass, as obtained in the above equation (10). If ALongRequiredCrossingB2P> 0, then the beam 204 will have to accelerate to collision in the longitudinal direction and therefore no collision will occur.In step 122, the method 100 checks whether the carrier 204 will reach a zero relative velocity component along the longitudinal direction before the target 208 is expected to clear the zone 200. In this case, no collision would occur. If the carrier 204 has a current deceleration value A Long Rel along the longitudinal direction and a current relative longitudinal speed of V Long Rel the time required for the carrier 204 to reach a longitudinal speed of zero with this acceleration value is given using the equation of first degree of motion: if T ToVLongRel=0 > Time TC, then the relative velocity component of the carrier 204 in the longitudinal direction becomes zero before the target 208 crosses the zone 200, and no collision would occur.In step 124, the method 100 calculates a brake threat number (BTN) for the state of the brake to pass. The brake risk number is given by: wherein:ALongRequiredCrossingBTP= The deceleration required by the brake pass state carrier 204AHostLongMax= maximum acceleration / deceleration that the host vehicle can reach, andBTN BTP= Brake Risk Number Required for Running By Braking.In step 126, an intervention decision is made based on the value of the brake danger number obtained from the above equation (12). The intervention decision corresponds to warning signals provided to the occupant of the host vehicle 204. For BTN=1, this means that at its current position, the carrier 204 must immediately apply the brakes to just allow the target 208 to safely traverse the zone 200. In practice, the driver has a certain reaction time when he receives these signals, and the delay in the immediate application of the brakes is taken into account in the calculation of the brake risk number. In one aspect, a certain threshold value of BTN BTP may be set, and when the actual value of BTN reaches this threshold value, a warning signal is provided to the occupant of the carrier 204 to immediately apply the brakes.The disclosed method 100 for calculating the brake threat number and avoiding collisions between the target vehicle and the host vehicle may be used with vehicles of any type and dimensions, including automobiles, trucks, trailers, etc. Further, the calculation of the brake threat number to provide warning signals to the target vehicle is mandatory for cases where the host and target vehicles have trajectories that cross when further projected and there is the specific possibility of an anticipated collision.Although the present invention has been described in considerable detail to cover the possible aspects and embodiments, those skilled in the art will recognize that other versions of the invention may be possible.

Claims

A method of avoiding a collision between a host vehicle (204) and a target vehicle (208), the method comprising: locating current positions of the host vehicle (204) and the target vehicle (208) and defining a potential collision zone (200); assuming the lengths of the target and host vehicles (204); determining if the assumed vehicle lengths are incorrect and, if incorrect, adjusting the assumed lengths; checking if the target vehicle (208) is currently crossing the path of the host vehicle (204) in consideration of the adjusted assumed lengths of the vehicles; predicting the position of the host vehicle (204) at the time the target vehicle (208) is expected to reach the potential collision zone (200); calculating a change in speed value for the host vehicle (204) required for the host vehicle (204) to avoid collision with the target vehicle (208) based on the adjusted assumed lengths; and providing signals to the host vehicle (204) to perform the change in speed for the host vehicle (204).The method of claim 1, wherein defining the potential collision zone (200) comprises forward projecting the current trajectories of the host vehicle (204) and the target vehicle (208) along their respective directions of motion and determining the intersection of the projected trajectories.The method of claim 1, further comprising calculating the distance to travel and the time required for the target vehicle (208) to reach the potential collision zone (200) from its current position.The method of claim 1, further comprising calculating the distance to be traveled by the host vehicle (204) from its current position to reach the potential collision zone (200).The method of claim 1, further comprising adjusting the assumed lengths by adding the actual length of the host vehicle (204) or the target vehicle (208) to the length of a towed object (212) when the host vehicle (204) or the target vehicle (208) pulls the object (212), respectively.The method of claim 3, further comprising calculating the distance to travel and the time required for the target vehicle (208) to clear the potential collision zone (200) from its current position.The method of claim 1, wherein checking whether the target vehicle (208) is currently crossing the path of the host vehicle (204) further comprises comparing, for the target vehicle (208), a value corresponding to the distance to travel from its current position to reach the potential collision zone (200) with a value corresponding to the distance to travel from its current position to clear the potential collision zone (200), and reporting the crossing if the two values have different signs.The method of claim 1, further comprising determining the position of the host vehicle (204) at the time when the target vehicle (208) is expected to enter the potential collision zone (200).The method of claim 8, further comprising determining a current position of the forward portion of the host vehicle (204) relative to a proximal side of the target vehicle (208), wherein the current position is determined along a longitudinal direction that is substantially parallel to the direction of travel of the host vehicle.The method of claim 9, further comprising determining a current position of the rear portion of the host vehicle (204) relative to a distal side of the target vehicle (208), the position being determined along the longitudinal direction.The method of claim 8, further comprising calculating the distance between the rear portion of the host vehicle and a distal side of the target vehicle (208) at a time when the target vehicle (208) is expected to reach the potential collision zone (200).The method of claim 1, wherein calculating the speed change value of the host vehicle (204) further comprises calculating the distance between a front portion of the host vehicle (204) and a proximal side of the target vehicle (208) at a time when the target vehicle (208) is expected to clear the potential collision zone (200).The method of claim 1, further comprising calculating a braking threat number value by dividing the change in speed value of the host vehicle (204) by a maximum deceleration value that the host vehicle (204) can reach.The method of claim 13, wherein the occupant of the host vehicle (204) is warned to immediately apply the brakes to achieve a maximum deceleration when the brake threat number value is 1.The method of claim 13, further comprising setting a threshold value corresponding to the brake threat number value and providing warning signals to the occupant of the host vehicle (204) when the calculated brake threat number value exceeds the threshold value.The method of claim 1, further comprising calculating a brake threat number value using the change in speed value required for the host vehicle (204), and providing signals to the host vehicle (204) based on the brake threat number value.

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