Motion sensor assembly for determining the angular velocity of a moving contrast in its field of view with a high accuracy

Patent metadata

Field	Value
Publication number	US-9797919-B2
Application number	US-201314438601-A
Country	US
Kind code	B2
Filing date	Oct 17, 2013
Priority date	Oct 26, 2012
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

A motion sensor assembly is adapted to determine an angular velocity of a moving contrast in its field of view. The motion sensor assembly includes: a motion sensor with a first and a second analog photoreceptor each adapted for observing the moving contrast, the first and the second photoreceptors being separated by a predetermined interreceptor angle; and an angular velocity calculating unit connected to the first and second photoreceptors for calculating the angular velocity of the moving contrast based on a first and a second analog signal delivered by the first and the second photoreceptors, respectively. The first and the second analog signals delivered by the first and the second photoreceptors at are sampled a given sampling frequency to obtain a first and a second digital signal, respectively. An interpolator is configured to interpolate the first and the second digital signals upon their crossing a predetermined threshold between successive samples.

First claim

The invention claimed is:

1. A motion sensor assembly adapted to determine an angular velocity of a moving contrast in a field of view of said motion sensor assembly, said motion sensor assembly comprising:
at least one motion sensor with a first and a second analog photoreceptors each adapted for observing said moving contrast, wherein said first and second photoreceptors are separated by a predetermined interreceptor angle; and
an angular velocity calculating unit connected to said first and second photoreceptors for calculating said angular velocity of said moving contrast based on a first and a second analog signal delivered by said first and second photoreceptors, respectively;
wherein said angular velocity calculating unit comprises a sampler configured to temporally sample said first and second analog signals delivered by said first and second photoreceptors at a given sampling frequency to obtain a first and a second digital signal respectively;
wherein said angular velocity calculating unit further comprises an interpolator configured to interpolate said first and second digital signals upon a crossing of a predetermined threshold by said first and second digital signals between successive samples; wherein said angular velocity calculating unit further comprises a filter configured to output a first and a second filtered digital signal from said first and second digital signals.

2. The motion sensor assembly of claim 1 , wherein said interpolator comprises:
a detector configured to detect said crossing, by said first and second digital signals, of said predetermined threshold;
the interpolator, which is configured to interpolate said first interpolated time of said crossing by said first digital signal and said second interpolated time of said crossing by said second digital signal; and
an estimator configured to estimate said delay in said crossing between said first and second digital signals based on said first and second interpolated times.

3. The motion sensor assembly of claim 1 , said interpolator comprises:
a detector configured to detect said crossing, by said first and second digital signals, of said predetermined threshold;
the interpolator, which is configured to interpolate:
a) a first interpolated time interval between said crossing by said first digital signal and said crossing by a next sample of said first digital signal; and
b) a second interpolated time interval between said crossing by said second digital signal and said crossing by a next sample of said second digital signal ; and

an estimator configured to estimate a delay in said crossing between said first and second digital signals based on said first and second interpolated time intervals;
and wherein said angular velocity calculating unit further comprises a calculator configured to calculate said angular velocity by dividing said predetermined interreceptor angle by said delay.

4. The motion sensor assembly of claim 1 , wherein said given sampling frequency is between 0.01 and 1000000 Hz.

5. The motion sensor assembly of claim 4 , wherein said given sampling frequency is equal to about 200 Hz.

6. The motion sensor assembly of claim 1 , wherein said motion sensor assembly comprises an array of photoreceptors.

7. The motion sensor assembly of claim 6 , wherein said array of photoreceptors is a 3×4 array.

8. The motion sensor assembly of claim 1 , wherein said angular velocity calculating unit comprises a microcontroller.

9. A vehicle equipped with said motion sensor assembly of claim 1 .

10. The vehicle of claim 9 , wherein said vehicle is a terrestrial, maritime or aerial vehicle, a Micro Aerial Vehicle, motor vehicle, drone or space vehicle.

11. The motion sensor assembly of claim 1 , wherein said filter is a low-pass filter.

12. The motion sensor assembly of claim 1 , wherein said interpolator comprises:
a detector configured to detect said crossing, by said first and second digital signals, of said predetermined threshold;
the interpolator, which is configured to interpolate:
a) a first interpolated time interval between said crossing by said first digital signal and said crossing by a next sample of said first digital signal; and
b) a second interpolated time interval between said crossing by said second digital signal and said crossing by a next sample of said second digital signal; and

an estimator configured to estimate a delay in said crossing between said first and second digital signals based on said first and second interpolated time intervals.

13. A method for determining an angular velocity of a moving contrast, said method comprising the steps of:
obtaining a first and a second analog signal by observing said moving contrast from a first and a second photoreceptors separated by a predetermined interreceptor angle; and
temporally sampling said first and second analog signals at a given sampling frequency to obtain a first and a second digital signal, and
interpolating said first and second digital signals upon a crossing of a predetermined threshold by said first and second digital signals between successive samples, wherein a filtering step is provided outputting a first and a second filtered digital signal from said first and second digital signals.

14. The method of claim 13 , wherein said interpolating comprises:
detecting said crossing, by said first and second digital signals, of said predetermined threshold;
interpolating said first interpolated time of said crossing by said first digital signal and said second interpolated time of said crossing by said second digital signal; and
estimating a delay in said crossing between said first and second digital signals based on said first and second interpolated times.

15. The method of claim 13 , wherein said interpolating comprises:
detecting said crossing, by said first and second digital signals, of said predetermined threshold;
interpolating:
a) said first interpolated time interval between said crossing by said first digital signal and a next sample of a first filtered digital signal; and
b) said second interpolated time interval between said crossing by said second digital signal and a next sample of a second filtered digital signal; and

estimating said delay in said crossing between said first and second digital signals based on said first and second interpolated time intervals,
and wherein the method further comprises calculating an angular velocity by dividing said predetermined interreceptor angle by said delay.

16. The method of claim 13 , wherein said given sampling frequency (f sample ) is between 100 and 500 Hz.

17. The method of claim 16 , wherein said given sampling frequency is equal to about 200 Hz.

18. The method of claim 13 , wherein said interpolating is a linear interpolating.

19. The method of claim 13 , wherein said interpolating comprises:
detecting said crossing, by said first and second digital signals, of said predetermined threshold;
interpolating:
a) said first interpolated time interval between said crossing by said first digital signal and a next sample of a first filtered digital signal; and
b) said second interpolated time interval between said crossing by said second digital signal and a next sample of a second filtered digital signal; and

estimating said delay in said crossing between said first and second digital signals based on said first and second interpolated time intervals.

Assignees

• Univ D'Aix—Marseille
• Centre Nat De La Rech Scient (C N R S)
• Univ Aix Marseille
• Centre Nat De La Rech Scient (C N R S )

Inventors

• Ruffier Franck
• Expert Fabien

Classifications

• G01P3/38 Primary

  using photographic means · CPC title

• G01S11/12

  using electromagnetic waves other than radio waves · CPC title

• G01P3/68

  using optical means, i.e. using infrared, visible, or ultraviolet light (G01P3/80 takes precedence {; by reflection of waves G01S17/58}) · CPC title