Systems and methods for braking a vehicle based on a detected object

1. An object detecting and braking system for a vehicle, comprising:

at least one image capture device configured to acquire a plurality of images of an area including an object in front of the vehicle;

a data interface; and

at least one processing device programmed to:

receive the plurality of images via the data interface;

perform a first image analysis based on at least a first image and a second image to determine a first estimated time-to-collision of the vehicle with the object;

perform a second image analysis based on at least a third image and a fourth image to determine a second estimated time-to-collision of the vehicle with the object, the second image analysis including:

determining a focus of expansion based on the third image and the fourth image, the focus of expansion being a converging point of vectors in a vector field determined from the third image and the fourth image; and

determining a rate of expansion associated with a point in the vector field relative to the focus of expansion by dividing a magnitude of a vector associated with the point by a distance from the point to the focus of expansion;

calculate a difference between the first estimated time-to-collision and the second estimated time-to-collision;

determine that the difference does not exceed a predetermined threshold; and

cause the vehicle to brake based on the determination that the difference does not exceed the predetermined threshold.

2. The object detecting and braking system of claim 1 , wherein the first image analysis includes:

determining a first size of the object appearing in the first image;

determining a second size of the object appearing in the second image;

determining a change in size of the object based on the first size and the second size; and

determining the first estimated time-to-collision based on the change in size of the object and a predetermined time interval between times of acquisition of the first image and the second image.

3. The object detecting and braking system of claim 1 ,

wherein each point in the vector field is represented by a vector indicating a magnitude and a direction of movement from a first point in the third image to a corresponding second point in the fourth image, and

wherein the second image analysis further includes:

determining the second estimated time-to-collision based on the rate of expansion and a time interval between times of acquisition of the third image and the fourth image.

4. The object detecting and braking system of claim 1 , wherein the second image analysis includes:

determining a relationship between magnitudes and distances for a plurality of points in the vector field; and

determining that the object represented by the plurality of points is a low time-to-collision upright object based on a determination that the relationship is a linear relationship.

5. The object detecting and braking system of claim 1 , wherein the second image analysis includes:

determining a relationship between magnitudes and distances for a plurality of points in the vector field; and

determining that at least a portion of the object is a road surface based on a determination that the relationship is a non-linear relationship.

6. The object detecting and braking system of claim 1 ,

wherein each point in the vector field is represented by a vector indicating a magnitude and a direction of movement from a first point in the third image to a corresponding second point in the fourth image, and

wherein the second image analysis further includes:

detecting a first focus of expansion that is a first converging point of a first plurality of vectors in the vector field;

detecting a second focus of expansion that is a second converging point of a second plurality of vectors in the vector field; and

determining that the third image and the fourth image include a moving object that moves in a direction that is not parallel to a travel direction of the vehicle.

7. The object detecting and braking system of claim 1 ,

wherein each point in the vector field is represented by a vector indicating a magnitude and a direction of movement from a first point in the third image to a corresponding second point in the fourth image, and

wherein the second image analysis further includes:

determining that the third image and the fourth image represent an environment that is static relative to a road surface on which the vehicle is traveling.

8. The object detecting and braking system of claim 1 , wherein the first image used for the first image analysis is different from the third image used for the second image analysis, and wherein the second image used for the first image analysis is different from the fourth image used for the second image analysis.

9. The object detecting and braking system of claim 1 , wherein the first image used for the first image analysis is the same as the third image used for the second image analysis, and wherein the second image used for the first image analysis is the same as the fourth image used for the second image analysis.

10. The object detecting and braking system of claim 1 , wherein the first image analysis and the second image analysis are independent of each other.

11. The object detecting and braking system of claim 1 , wherein the at least one image capture device includes:

a first image sensor configured to capture the first image and the second image to be used in the first image analysis; and

a second image sensor independent of the first image sensor and configured to capture the third image and the fourth image to be used in the second image analysis.

12. A vehicle, comprising:

a body;

at least one image capture device configured to acquire a plurality of images of an area including an object in front of the vehicle;

a data interface; and

at least one processing device programmed to:

receive the plurality of images via the data interface;

perform a first image analysis based on at least a first image and a second image to determine a first estimated time-to-collision of the vehicle with the object;

perform a second image analysis based on at least a third image and a fourth image to determine a second estimated time-to-collision of the vehicle with the object, the second image analysis including:

determining a focus of expansion based on the third image and the fourth image, the focus of expansion being a converging point of vectors in a vector field determined from the third image and the fourth image; and

determining a rate of expansion associated with a point in the vector field relative to the focus of expansion by dividing a magnitude of a vector associated with the point by a distance from the point to the focus of expansion;

calculate a difference between the first estimated time-to-collision and the second estimated time-to-collision;

determine that the difference does not exceed a predetermined threshold; and

cause the vehicle to brake based on the determination that the difference does not exceed the predetermined threshold.

13. The vehicle of claim 12 , wherein the first image analysis includes:

determining a first size of the object appearing in the first image;

determining a second size of the object appearing in the second image;

determining a change in size of the object based on the first size and the second size; and

determining the first estimated time-to-collision based on the change in size of the object and a predetermined time interval between times of acquisition of the first image and the second image.

14. The vehicle of claim 12 , wherein each point in the vector field is represented by a vector indicating a magnitude and a direction of movement from a first point in the third image to a corresponding second point in the fourth image, and

wherein the second image analysis further includes:

determining the second estimated time-to-collision based on the rate of expansion and a time interval between times of acquisition of the third image and the fourth image.

15. The vehicle of claim 14 , wherein the second image analysis includes:

determining a relationship between magnitudes and distances for a plurality of points in the vector field; and

determining that the object represented by the plurality of points is a low time-to-collision upright object based on a determination that the relationship is a linear relationship.

16. A method for detecting an object and braking a vehicle, comprising:

acquiring, via at least one image capture device, a plurality of images of an area including an object in front of the vehicle;

receiving, via a processing device, the plurality of images;

performing, via the processing device, a first image analysis based on at least a first image and a second image to determine a first estimated time-to-collision of the vehicle with the object;

performing, via the processing device, a second image analysis based on at least a third image and a fourth image to determine a second estimated time-to-collision of the vehicle with the object, the second image analysis including:

determining a focus of expansion based on the third image and the fourth image, the focus of expansion being a converging point of vectors in a vector field determined from the third image and the fourth image; and

determining a rate of expansion associated with a point in the vector field relative to the focus of expansion by dividing a magnitude of a vector associated with the point by a distance from the point to the focus of expansion;

calculating, via the processing device, a difference between the first estimated time-to-collision and the second estimated time-to-collision;

determining, via the processing device, that the difference does not exceed a predetermined threshold; and

causing, via the processing device, the vehicle to brake based on the determination that the difference does not exceed the predetermined threshold.

17. The method of claim 16 , wherein the first image analysis includes:

determining a first size of the object appearing in the first image;

determining a second size of the object appearing in the second image;

determining a change in size of the object based on the first size and the second size; and

determining the first estimated time-to-collision based on the change in size of the object and a predetermined time interval between times of acquisition of the first image and the second image.

18. The method of claim 16 ,

wherein each point in the vector field is represented by a vector indicating a magnitude and a direction of movement from a first point in the third image to a corresponding second point in the fourth image, and

wherein the second image analysis further includes:

determining the second estimated time-to-collision based on the rate of expansion and a time interval between times of acquisition of the third image and the fourth image.