Optical sensor for odometry tracking to determine trajectory of a wheel

• US 10,643,335 B2
• Filed: 09/24/2018
• Issued: 05/05/2020
• Est. Priority Date: 11/03/2015
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Leong, Keen-Hun, Kok, Boon-How, Dominic Donald, Dennis
• Primary Examiner(s): Couso, Jose L
• Application Number:
  US16/140,444
• Publication Number:
  US 20190026903A1
• Time in Patent Office: 589 Days
• CPC Class Codes: B60W 30/00 Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
• CPC Class Codes: B62D 15/024 Other means for determination of steering angle without directly measuring it, e.g. deriving from wheel speeds on different sides of the car
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 22/00 Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G06F 3/0362 with detection of 1D translations or rotations of an operating part of the device, e.g. scroll wheels, sliders, knobs, rollers or belts
• CPC Class Codes: G06T 2207/30241 Trajectory
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51
• CPC Class Codes: H04N 23/90 Arrangement of cameras or camera modules, e.g. multiple cameras in TV studios or sports stadiums

Abstract

An optical sensor system for determining trajectory of a car, the optical sensor system being mounted in a wheel arch of the car, includes: a plurality of optical sensors mounted in the wheel arch above a wheel, the optical sensors being located behind a plurality of clear casings that do not touch the wheel, for performing a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to an outer surface of the wheel evenly covered with wheel treads. The captured images are compared with a reference image to determine a 2D displacement of the wheel from its original position. This measured 2D displacement is converted into a distance the wheel travels along a path, and the wheel trajectory is determined by calculating a turning degree of the wheel according to a trigonometric manipulation of the captured 2D displacement.

Claims

1. An optical sensor system for determining trajectory of a car, the optical sensor system being mounted in a wheel arch of the car, and comprising:

a first optical sensor mounted in the wheel arch above a wheel, an outer surface of the wheel being covered with evenly-spaced wheel treads, wherein the first optical sensor is located behind a first clear casing that does not touch the wheel, and the first optical sensor performs a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to the wheel treads;

a second optical sensor mounted in the wheel arch on one side of the wheel, wherein the second optical sensor is located behind a second clear casing that does not touch the wheel, and the second optical sensor performs a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to the wheel treads; and

a third optical sensor mounted in the wheel arch on the other side of the wheel, wherein the third optical sensor is located behind a third clear casing that does not touch the wheel, and the third optical sensor performs a plurality of counts corresponding to respectively capturing a plurality of images of the wheel according to the wheel treads;

wherein the captured images of at least one of the optical sensors is compared with a reference image to determine a 2D displacement of the wheel from its original position, this measured 2D displacement is converted into a distance the wheel travels along a path, and the trajectory of the car is determined by calculating a turning degree of the wheel according to a trigonometric manipulation of the measured 2D displacement.

2. The optical sensor system of claim 1, wherein the calculated turning degree and at least a distance between a front wheel axle and a rear wheel axle of the car are utilized to determine a turning curve along which the wheel moves, wherein the turning curve is centered on a point where an extended line from the rear wheel axle crosses a perpendicular line to the front wheel axle.

3. The optical sensor system of claim 1, wherein a calibration process is performed when the wheel rotates but does not turn, the calibration process comprising:

measuring a 2D displacement of the wheel corresponding to a single rotation of the wheel;

determining how many counts are performed according to this single rotation; and

utilizing a circumference of the wheel to determine a distance per count (dpc) value, wherein the dpc value is used to convert the measured 2D displacement into a distance the wheel travels along a path.

4. A method for using an optical sensor system mounted in a wheel arch of a car to determine trajectory of the car, the method comprising:

utilizing a first optical sensor mounted in the wheel arch above the wheel and behind a first clear casing which does not touch the wheel, a second optical sensor mounted in the wheel arch on one side of the wheel and behind a second clear casing which does not touch the wheel, and a third optical sensor mounted in the wheel arch on the other side of the wheel and behind a third clear casing which does not touch the wheel to perform the following steps;

capturing a plurality of images of the wheel according to evenly-spaced wheel treads on an outer surface of the wheel, to generate a plurality of counts, respectively;

comparing the captured images of at least one of the optical sensors with a reference image to determine a 2D displacement of the wheel; and

performing a calculation to convert the measured 2D displacement of the wheel from its original position into a distance the wheel travels along a path in order to determine the trajectory of the car, comprising;

calculating a turning degree of the wheel according to a trigonometric manipulation of the measured 2D displacement.

5. The method of claim 4, wherein the step of performing a calculation to determine the wheel trajectory further comprises:

utilizing the calculated turning degree and at least a distance between a front wheel axle and a rear wheel axle of the car to determine a turning curve along which the wheel moves, the turning curve being centered on a point where an extended line from the rear wheel axle crosses a perpendicular line to the front wheel axle.

6. The method of claim 4, wherein a calibration process is performed when the wheel rotates but does not turn, the calibration process comprising the following steps:

measuring a 2D displacement of the wheel corresponding to a single rotation of the wheel;

determining how many counts are performed according to this single rotation; and

utilizing a circumference of the wheel to determine a distance per count (dpc) value;

wherein the dpc value is used to convert the measured 2D displacement into a distance the wheel travels along a path.