Method and system for collision course prediction and collision avoidance and mitigation

• US 8,762,043 B2
• Filed: 01/27/2009
• Issued: 06/24/2014
• Est. Priority Date: 01/29/2008
• Status: Active Grant

• Current Assignee: Volvo Car Corporation (AB Volvo)
• Original Assignee: Volvo Car Corporation (AB Volvo)
• Inventors: Olsson, Claes, Eidehall, Andreas, Pohl, Jochen
• Primary Examiner(s): Lubin, Valerie
• Assistant Examiner(s): Reyes, Reginald R
• Application Number:
  US12/360,618
• Publication Number:
  US 20090192710A1
• Time in Patent Office: 1,974 Days
• Field of Search: 701/200
• US Class Current: 701/301
• CPC Class Codes: B60W 2554/4041 Position
• CPC Class Codes: B60W 2554/4042 Longitudinal speed
• CPC Class Codes: B60W 2554/4043 Lateral speed
• CPC Class Codes: B60W 2554/801 Lateral distance
• CPC Class Codes: B60W 2554/803 Relative lateral speed
• CPC Class Codes: B60W 2554/804 Relative longitudinal speed
• CPC Class Codes: B60W 30/08 Active safety systems predicting or avoiding probable or impending collision or attempting to minimise its consequences
• CPC Class Codes: B60W 50/0097 Predicting future conditions
• CPC Class Codes: B62D 15/0265 Automatic obstacle avoidance by steering

Abstract

A system for collision course prediction includes a host vehicle sensor system detecting information relating to a target object including a position and a velocity relative to the host vehicle; a time-to-collision estimator control block calculating an estimated time-to-collision based on a longitudinal distance, longitudinal velocity and longitudinal acceleration of the target object relative to the host vehicle; a lateral distance estimator control block, which estimates the lateral distance between the centers of the host vehicle and target object at the estimated time-to-collision; and a collision course condition determination unit determining, at a determination instant prior to the estimated time-to-collision, a probability that the host vehicle will collide with the target object dependent at least in part upon whether the lateral distance is within a first interval, the first interval based on at least a lateral width of the host vehicle and a lateral width of the target object.

Claims

1. A collision course prediction system comprising:

a sensor system installable in a host vehicle and transmitting at an operating frequency, the sensor system detecting a target object external to the host vehicle and determining at least an object position (x, y) and an object velocity ({dot over (x)},{dot over (y)})of the target object relative to the host vehicle;

a time-to-collision estimator control block calculating an estimated time-to-collision T.sub.ttc based on a longitudinal distance (x), a longitudinal velocity ({dot over (x)}) and a longitudinal acceleration ({umlaut over (x)}) of the target object relative to the host vehicle;

a lateral distance estimator control block estimating a lateral distance (y) between respective centers of the host vehicle and the target object at the estimated time-to-collision T.sub.ttc, the estimation based upon a distance r to the target object from the host vehicle and a target angle (alpha) between the heading direction of the host vehicle and the position of the target vehicle determined by the sensor system; and

a collision course condition determination unit determining, at a determination instant t prior to the estimated time-to-collision T.sub.ttc, a probability that the host vehicle will collide with the target object dependent at least in part upon whether the lateral distance is within a first interval, the first interval based on at least a lateral width of the host vehicle, a lateral width of the target object, and a target angle measurement error correction term Z2, the target angle measurement error correction term Z2 dependent on the distance r at the determination instant t and including a factor k* dependent upon a noise distribution of the sensor system in sensing the target angle (alpha) when transmitting at the operating frequency, wherein the correction term Z2 is determined as Z2=Z0+k*r, where Z0 is a constant.

2. A system according to claim 1, wherein the collision course condition determination unit further determines the probability that the host vehicle will collide with the target object dependent at least in part upon whether the estimated time-to-collision T_ttc is within a time interval T_LC1<

T_ttc<

T_LC2, where T_LC1 is an estimated time for the host vehicle to enter a neighboring lane occupied by the target object and T_LC2 is an estimated time for the host vehicle to leave the neighboring lane.

3. A system according to claim 1, wherein the lateral distance estimator control block estimates the lateral distance (y(T_ttc)) between respective centers of the host vehicle and target object at the estimated time-to-collision T_ttc as y(T_ttc)=y(t)+{dot over (y)}(t)·

T_ttc+(ÿ

(t)·

T_ttc²)/2, where {dot over (y)}(t) is a lateral velocity at the determination instant t and ÿ

(t) is a lateral acceleration at the determination instant t.

4. A system according to claim 1, further comprising a collision avoidance/mitigation system comprising:

a steering torque condition function block assessing whether a required steering torque applied to a steering arrangement of the host vehicle in order to avoid collision with the target object in a neighboring lane is within a steering torque range;

a host lane threat condition functional block assessing whether a required braking force applied to a braking arrangement of the host vehicle to avoid an obstacle in a current lane occupied by the target vehicle is below a threshold braking force value;

a timing condition functional block determining whether the estimated time-to-collision T_ttc is below a threshold time value; and

a data processing unit generating at least one of a steering intervention and a braking intervention if each of the following conditions are satisfied;

a) the probability of collision determined by the collision course condition determination unit is sufficiently high, and b) the required steering torque is within the steering torque range, and c) the required braking force is below the threshold braking force value, and d) the estimated time-to-collision T_ttc s below the threshold time value.

5. A method of predicting a probability that a host vehicle will collide with a target object comprising:

operating a sensor system of the host vehicle to transmit at an operating frequency to detect the target object and determine at least a position (x, y) and a velocity ({dot over (x)},{dot over (y)}) of the target object relative to the host vehicle;

calculating an estimated time-to-collision T.sub.ttc based on a longitudinal distance (x), a longitudinal velocity ({dot over (x)}) and a longitudinal acceleration ({umlaut over (x)}) of the target object relative to the host vehicle;

estimating a lateral distance (y) between respective centers of the host vehicle and the target object at the estimated time-to-collision T.sub.ttc, the estimation based upon a distance r to the target object from the host vehicle and a target angle (alpha) between the heading direction of the host vehicle and the position of the target vehicle determined by the sensor system; and

determining, using a determination unit, at a determination instant t prior to the estimated time-to-collision T.sub.ttc, the probability that the host vehicle will collide with the target object dependent at least in part upon whether the lateral distance is within a first interval, the first interval based on at least a lateral width of the host vehicle, a lateral width of the target object, and a target angle measurement error correction term Z2, the target angle measurement error correction term Z2 dependent on a distance r to the target object from the host vehicle at the determination instant t and including a factor k* dependent upon a noise distribution of the sensor system in sensing the target angle (alpha) when transmitting at the operating frequency, wherein the correction term Z2 is determined as Z2=Z0+k*r, where Z0 is a constant.

6. A method according to claim 5 wherein the step of determining the probability that the host vehicle will collide with the target object is further dependent at least in part upon whether the estimated time-to-collision T_ttc is within a time interval T_LC1<

T_ttc<

T_LC2, where T_LC1 is an estimated time for the host vehicle to enter a neighboring lane occupied by the target object and T_LC2 is an estimated time for the host vehicle to leave the neighboring lane.

7. A method according to claim 5 wherein the step of estimating the lateral distance (y) comprises estimating a lateral distance (y(T_ttc)) between respective centers of the host vehicle and target object at the estimated time-to-collision T_ttc as y(T_ttc)=y(t)+{dot over (y)}(t)·

T_ttc+(ÿ

(t)·

T_ttc²)/2, where {dot over (y)}(t) is a lateral velocity at the determination instant t and ÿ

(t) is a lateral acceleration at the determination instant t.

8. A collision avoidance/mitigation system assessing a risk that a host vehicle will collide with a threat object and generating an intervention in operation of the host vehicle if the risk is sufficiently high, the system comprising:

a sensor system installable in a host vehicle, the sensor system detecting a target object external to the host vehicle by transmitting at an operating frequency and determining at least an object position (x, y) and an object velocity ({dot over (x)},{dot over (y)}) of the target object relative to the host vehicle;

a time-to-collision estimator control block calculating an estimated time-to-collision T.sub.ttc based on a longitudinal distance (x), a longitudinal velocity ({dot over (x)}) and a longitudinal acceleration ({umlaut over (x)}) of the target object relative to the host vehicle;

a lateral distance estimator control block estimating a lateral distance (y) between respective centers of the host vehicle and the target object at the estimated time-to-collision T.sub.ttc;

a collision course condition determination unit determining, at a determination instant t prior to the estimated time-to-collision T.sub.ttc, a probability that the host vehicle will collide with the target object dependent at least in part upon whether the lateral distance is within a first interval, the first interval based on at least a lateral width of the host vehicle and a lateral width of the target object and a target angle measurement error correction term Z2, the target angle measurement error correction term Z2 dependent on a distance r to the target object from the host vehicle at the determination instant t and including a factor k* dependent upon a noise distribution of the sensor system in sensing the target angle (alpha) when transmitting at the operating frequency, wherein the correction term Z2 is determined as Z2=Z0+k*r, where Z0 is a constant;

a steering torque condition function block assessing whether a required steering torque applied to a steering arrangement of the host vehicle in order to avoid collision with the target object in a neighboring lane is within a steering torque range;

a host lane threat condition functional block assessing whether a required braking force applied to a braking arrangement of the host vehicle to avoid an obstacle in a current lane occupied by the target vehicle is below a threshold braking force value;

a timing condition functional block determining whether the estimated time-to-collision T.sub.ttc is below a threshold time value; and

a data processing unit generating at least one of a steering intervention and a braking intervention if each of the following conditions are satisfied;

a) the probability of collision determined by the collision course condition determination unit is sufficiently high, and b) the required steering torque is within the steering torque range, and c) the required braking force is below the threshold braking force value, and d) the estimated time-to-collision T.sub.ttc is below the threshold time value.