PITCH ANGLE ESTIMATION APPARATUS

• US 20170039433A1
• Filed: 08/05/2016
• Published: 02/09/2017
• Est. Priority Date: 08/06/2015
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kawano, Taiki, Nitanda, Naoki, Hoki, Kenta, Kawasaki, Naoki
• Granted Patent: US 10,037,470 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06V 10/462 Salient features, e.g. scale invariant feature transforms [SIFT]
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: H04N 23/60 Control of cameras or camera modules
• CPC Class Codes: H04N 23/80 Camera processing pipelines; Components thereof

Abstract

In a pitch angle estimation apparatus, an image acquirer sequentially acquires images in a forward or rearward direction of a vehicle. Each image is referred to as a frame. A movement amount calculator extracts a feature point from each of the images acquired by the image acquirer and calculates an amount of movement of the feature point in a vertical direction of the image. A pitch angle calculator calculates a pitch angle of the vehicle based on the amount of movement of the feature point. An output unit outputs the pitch angle calculated by the pitch angle calculator. A low frequency component calculator calculates a low frequency component of the pitch angle calculated by the pitch angle calculator. An output determiner determines whether to output the pitch angle based on the magnitude of the low frequency component calculated by the low frequency component calculator.

Claims

1. A pitch angle estimation apparatus comprising:

an image acquirer configured to sequentially acquire images in a forward or rearward direction of a vehicle, each image being referred to as a frame;

a movement amount calculator configured to extract a feature point from each of the images acquired by the image acquirer and calculate an amount of movement of the feature point in a vertical direction of the image;

a pitch angle calculator configured to calculate a pitch angle of the vehicle based on the amount of movement of the feature point calculated by the movement amount calculator;

an output unit configured to output the pitch angle calculated by the pitch angle calculator;

a low frequency component calculator configured to calculate a low frequency component of the pitch angle calculated by the pitch angle calculator; and

an output determiner configured to determine whether to output the pitch angle based on the magnitude of the low frequency component calculated by the low frequency component calculator.

2. The apparatus of claim 1, wherein the output determiner is configured to, during the output unit outputting the pitch angle, if the magnitude of the low frequency component continuously exceeds an upper limit over the last N1 (N1 being a positive integer) frames including the current frame, stop outputting the pitch angle, and during the output unit outputting no pitch angle, if the magnitude of the low frequency component continuously falls below a lower limit over the last N2 (N2 being a positive integer) frames including the current frame and if an amount of change in the magnitude of the low frequency component between the current frame and the N3-th previous frame (N3 being a positive integer) is below a predetermined threshold, resume outputting the pitch angle.

3. The apparatus of claim 1, further comprising a movement pattern determiner configured to acquire a movement pattern that is a pattern of movement of the feature point in the image extracted by the movement amount calculator, and determine whether or not the movement pattern corresponds to one of predetermined anomalous patterns,

wherein the output determiner is configured to, if it is determined by the movement pattern determiner that the movement pattern corresponds to one of the predetermined anomalous patterns, stop outputting the pitch angle.

4. The apparatus of claim 1, wherein the movement amount calculator is configured to, using optical flow of the feature point, calculate the amount of movement of the feature point.

5. The apparatus of claim 1, wherein the pitch angle calculator is configured to calculate the pitch angle of the vehicle by an integrator having a preset forgetting factor of greater than zero integrating the amount of movement of the feature point.

6. The apparatus of claim 1, wherein the low frequency component calculator includes at least one finite or infinite impulse response filter, and is configured to calculate the low frequency component by performing filtering on the pitch angle using the at least one finite or infinite impulse response filter.

7. The apparatus of claim 6, wherein the low frequency component calculator includes a plurality of finite or infinite impulse response filters having different time constants, and is configured to select one of the plurality of finite or infinite impulse response filters and calculate the low frequency component by performing filtering on the pitch angle using the selected one of the plurality of finite or infinite impulse response filters.

8. The apparatus of claim 7, further comprising a gradient change estimator configured to estimate a change in gradient of a road on which the vehicle is traveling,

wherein the low frequency component calculator is configured to select a filter having a smaller time constant for a larger change in gradient estimated by the gradient change estimator.

9. The apparatus of claim 8, wherein the gradient change estimator is configured to estimate the change in gradient of the road on which the vehicle is traveling based on the magnitude of vertical movement of another vehicle in the image or outlines of lane partition lines in the image.

10. The apparatus of claim 7, wherein the low frequency component calculator is configured to select, from the plurality of finite or infinite impulse response filters, a filter that can minimize a difference integration value which is an integration of differences between the pitch angle calculated by the pitch angle calculator and the low frequency component calculated by the low frequency component calculator over a predetermined number of successive frames.

11. A pitch angle estimation apparatus comprising:

an image acquirer configured to sequentially acquire images in a forward or rearward direction of a vehicle, each image being referred to as a frame;

a movement amount calculator configured to extract a feature point from each of the images acquired by the image acquirer and calculate an amount of movement of the feature point in a vertical direction of the image;

a pitch angle calculator configured to calculate a pitch angle of the vehicle based on the amount of movement of the feature point;

a low frequency component calculator configured to calculate a low frequency component of the pitch angle calculated by the pitch angle calculator;

a corrector configured to correct the pitch angle by reducing the low frequency component of the pitch angle calculated by the low frequency component calculator; and

an output unit configured to output the pitch angle calculated by the pitch angle calculator and then corrected by the corrector.

12. The apparatus of claim 11, wherein the corrector is configured to correct the pitch angle by subtracting, from the pitch angle calculated by the pitch angle calculator, the low frequency component calculated by the low frequency component calculator or the low frequency component calculated by the low frequency component calculator, scaled by a factor that is less or greater than one.

13. The apparatus of claim 11, wherein the movement amount calculator is configured to, using optical flow of the feature point, calculate the amount of movement of the feature point.

14. The apparatus of claim 11, wherein the pitch angle calculator is configured to calculate the pitch angle of the vehicle by an integrator having a preset forgetting factor of greater than zero integrating the amount of movement of the feature point.

15. The apparatus of claim 11, wherein the low frequency component calculator includes at least one finite or infinite impulse response filter, and is configured to calculate the low frequency component by performing filtering on the pitch angle using the at least one finite or infinite impulse response filter.

16. The apparatus of claim 15, wherein the low frequency component calculator includes a plurality of finite or infinite impulse response filters having different time constants, and is configured to select one of the plurality of finite or infinite impulse response filters and calculate the low frequency component by performing filtering on the pitch angle using the selected one of the plurality of finite or infinite impulse response filters.

17. The apparatus of claim 16, further comprising a gradient change estimator configured to estimate a change in gradient of a road on which the vehicle is traveling,

wherein the low frequency component calculator is configured to select a filter having a smaller time constant for a larger change in gradient estimated by the gradient change estimator.

18. The apparatus of claim 17, wherein the gradient change estimator is configured to estimate the change in gradient of the road on which the vehicle is traveling based on the magnitude of vertical movement of another vehicle in the image or outlines of lane partition lines in the image.

19. The apparatus of claim 16, wherein the low frequency component calculator is configured to select, from the plurality of finite or infinite impulse response filters, a filter that can minimize a difference integration value which is an integration of differences between the pitch angle calculated by the pitch angle calculator and the low frequency component calculated by the low frequency component calculator over a predetermined number of successive frames.