Computer vision system and method for tank calibration using optical reference line method

Patent metadata

Field	Value
Publication number	US-10475203-B2
Application number	US-201815991507-A
Country	US
Kind code	B2
Filing date	May 29, 2018
Priority date	Feb 6, 2018
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

Systems and methods are disclosed for measuring the dimensions of storage tanks using Optical Reference Line Method calibration techniques. The system utilizes a camera mounted near the tank wall such that its optical axis defines a reference line extending parallel to the wall and a robotic vehicle for moving a target object along the surface of the tank. Specifically, the target includes a predefined measurement scale that can be imaged by the camera as it is moved along the wall. A computer implementing computer-vision algorithms analyzes images of the scale captured at respective elevations to determine the point on the scale intersected by the reference line and a corresponding offset distance between the wall and the reference line. Accordingly, the dimensions of the tank are calculated by the computer based on the offset distance calculated for respective elevations of the tank wall.

First claim

What is claimed is:

1. A system for measuring the volume of a tank, the system comprising:
a camera having an optical sensor, wherein the camera's optical axis is parallel to a surface of the tank and thereby defines an optical reference line extending parallel to the surface of the tank;
a robotic vehicle selectively moveable along the surface of the tank and configured to be remotely controlled by an operator, the robotic vehicle comprising:
a reference object having a standardized measurement scale provided on a surface of the reference object and facing the camera; and
a data processor that communicates with the camera and receives images of the measurement scale captured by the camera at respective elevations on the tank, the data processor comprising a processor and a computer readable non-transitory storage medium storing executable instructions in the form of one or more software modules that, when executed by the processor, configure the processor to:
determine, from the measurement scale depicted in the images, positions of the reference object relative to the optical reference line as the robotic vehicle moves along the surface of the tank, and
calculate the volume of at least a portion of the tank based at least partially on the determined positions.

2. The system of claim 1 , wherein the surface of the tank is a tank wall, and wherein the optical axis defining the optical reference line extends away from the camera in a vertical direction that is parallel to the tank wall and orthogonal to a normal direction of the tank wall.

3. The system of claim 1 , wherein the software modules configure the processor to determine the positions of the reference object by:
analyzing the images of the measurement scale captured by the camera using computer-vision algorithms; and
for each respective image, respectively,
determining a location on the measurement scale that intersects with the vertical reference line, and
calculating an offset distance in one or more directions between the location and a known reference location on the measurement scale.

4. The system of claim 3 , wherein the processor is further configured to calculate, for each respective image, a size parameter of the tank based on the calculated offset distance and a known geometry of the tank corresponding to the known reference location on the measurement scale, wherein the size parameter is one or more of a radius and a circumference.

5. The system of claim 4 , wherein the processor is further configured to calculate the volume of at least the portion of the tank, by the computing device based on the size parameters calculated from a plurality of the images.

6. The system of claim 3 , wherein the processor, using computer-vision algorithms, is further configured to calculate, for each respective image, the respective elevation of the reference object as a function of the camera's optical parameters and the measurement scale depicted in the respective image.

7. The system of claim 6 , the camera further comprising an adjustable optical zoom lens, wherein the data processor bases its calculations at least partially on a camera zoom parameter measured by the camera for the images, respectively.

8. The system of claim 7 , wherein the camera and the associated data processor using a computer vision algorithm are configured to adjust the camera's optical zoom lens to maintain at least a portion of the measurement scale at a suitable size in the images captured by the camera as the robotic vehicle moves along the surface of the tank and record the camera zoom parameter associated with the images, respectively; and
wherein the processor is configured to calculate the respective elevation of the reference object for the respective image based on the associated camera zoom parameter and a size of at least a portion of the measurement scale depicted in the respective image.

9. The system of claim 2 , wherein the robotic vehicle has an elevation sensor for measuring the elevation of the robotic vehicle, and wherein the elevation is relative to one or more of the bottom of the tank and the camera.

10. The system of claim 1 , wherein the surface of the tank is a tank bottom, and the camera is oriented such that the optical axis and optical reference line is parallel to the tank bottom.

11. The system of claim 1 , wherein the camera is mounted on a tripod to increase stability and is leveled on three axes to increase accuracy.

12. The system of claim 1 , wherein the measurement scale is a two-dimensional area having a length and width and comprises a pattern of marker objects provided at known positions within the two-dimensional area.

13. The system of claim 12 , wherein the processor is configured to determine the location on the measurement scale that intersects with the vertical reference line by measuring a relative position of one or more of the marker objects relative to the vertical reference line using a computer vision algorithm, and wherein the offset distance is calculated based on the measured relative position and the known respective position for the one or more marker objects.

14. The system of claim 12 , wherein the marker objects comprise one or more of distinguishable shapes and machine-readable codes.

15. The system of claim 12 , wherein the marker objects are arranged to define a pattern that extends in one or more of a lengthwise direction and a horizontal direction.

16. The system of claim 12 , wherein individual marker objects define a respective pattern that extends in one or more of a lengthwise direction and a horizontal direction.

17. A method for measuring the volume of a tank, comprising:
providing a camera, wherein the camera's optical axis is parallel to a surface of the tank and thereby defines an optical reference line extending parallel to the surface of the tank
urging a robotic vehicle along a surface of the tank, the robotic vehicle comprising a reference object having a standardized measurement scale provided on a surface of the reference object and facing the camera;
capturing, using the camera, images of the measurement scale as the robotic vehicle is moved along the surface of the tank;
monitoring, with a data processor that communicates with the camera and receives the images, changes of position of where the reference line intersects the standardized measurement scale, wherein the data processor comprises a computer readable non-transitory storage medium having executable instructions stored therein and a processor that is configured by executing the instructions;
estimating, with the data processor, a contour of the surface of the tank based on the step of monitoring; and
analyzing, with the data processor, the contour data to calculate a volume of the tank.

18. The method of claim 17 , further comprising:
determining, by the data processor from at least a first image, a reference location on the measurement scale that intersects with the vertical reference line, wherein the first image is captured at a given elevation of the reference object on the tank surface; and
wherein the step of monitoring changes of position of where the reference line intersects the standardized measurement scale comprises, for each of a plurality of images:
determining, with the data processor from a given image, a location on the scale that intersects with the vertical reference line, and
calculating, with the data processor, a difference between the determined location and the reference location.

19. The method of claim 18 , wherein the m

Assignees

• Saudi Arabian Oil Co

Inventors

• Parrott Brian
• Outa Ali
• Abdellatif Fadl

Classifications

• G01F17/00

  Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies (measuring linear dimensions to determine volume G01B) · CPC title

• G01C3/00

  Measuring distances in line of sight; Optical rangefinders (tapes, chains or wheels for measuring length G01B3/00; active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves, G01S17/48) · CPC title

• G01B11/00 Primary

  Measuring arrangements characterised by the use of optical techniques · CPC title

• G01C15/00

  Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00 · CPC title

• G01C25/00

  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 title