Projects:2015s1-22 Automatic Sorter using Computer Vision

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The aim of the project was to improve computer vision and robot arm control to accomplish a robust autonomous playing cards sorter. The project is primarily a demonstration tool for potential electronic engineering students to interactively show technology capabilities.It built on previous experiments in this area. The algorithm and hardware was built on and developed from other systems use for image processing. The resultant system was extremely robust, highly accurate, and a sound base for further refinement. The system can be modified by continual development into a versatile automatic sorter capable of use in other fields.

Completed Project.

Project information

The specific aims of the project this year are identified as:

  • To improve on the software subsystem of the last year’s project to ensure system reliability and performance by incorporating more sophisticated image processing techniques.
  • To ensure that most physical constraints will be overcome by the robustness of playing cards image processing algorithm, as an example, constraints on illumination.
  • To implement algorithms for recognising playing cards via suit, rank, and colour identifiers or different types of combination of these three.


The objectives of the project identified at the beginning are the following:-

  • Sort a full deck of standard playing cards
  • Use computer vision to differentiate between cards
  • Perform the following sorts:
    • Full Sort
    • Suit Sort
    • Colour Sort
    • Value Sort
  • Have a focus on electrical engineering, particularly image processing and reduce mechanical requirements


This project was tackled by breaking it into four subsections.

  • Computer Vision
  • Robotics
  • Card Sorting Algorithms
  • Graphical User Interface


Hardware overview.

The system consists of four hardware components:

  • Camera
  • Laptop PC
  • Microcontroller
  • Robotic Arm

Their individual functions are detailed in the image to the side.

Project Breakdown

Image Processing

The purpose of the image processing software of this project is to distinguish between different cards.

Image Processing Recoginition Stage Block Diagram.

This is done using a four step method:-

  • Find the outline of playing card on the black background
  • Crop and warp the playing card so that it is a perfect rectangle
  • Crop the suit and value images from the top left corner
  • Run Optical Character Recognition software on the suit and value images
Card Extraction Block Diagram.


The new recognition algorithm took in to consideration the following information:-

  • Top-left and bottom-right corners are the common information of these two types of playing cards.
  • Colour information of numeral card and face card are distinct.
  • Boundary information are different corresponding with different suit of playing cards.
  • In the central part of playing cards, the massive blobs (suits images) on numeral cards and two corners of face cards provide useful information.
  • In different face cards, different morphological feature provides one set of information to develop more robust decision making.
Playing Cards Feature Points.

Feature Matching(Face Card)

Blobs Counting (Numeral Card)

Template Matching Using Correlations

Colour Detection

Black Numeral Card Colour Detection Process.
Red Face Card Colour Detection Process.

Boundary Signature


The digital image techniques used in the above steps are as follows:-

(Refer links for further details)

Image Processing Steps Graphically Represented. (a) Original Image; (b) Outline of Card; (c) Corners of Card; (d)Suit and Value of Card Identified to be cropped

Results

The below table show the results of 6 full deck of cards testing.

Robotics and Kinematics

Inverse kinematic geometry of robotic arm

Arduino program

  • Connected with matlab via usb
  • The input from matlab is all the new angles for each servo
  • Output to matlab when robotic arm has finished moving

Matlab Program

  • Decide which set of movements to use depending on where a card is picked from and where it is placed
  • Use inverse kinematics to determine angles of the robotic arm depending on where the card is to be placed and how high the stack is
  • Forward Kinematic method
 x = l1(cos(θ1)) + l2(cos(θ1 – θ2)) + l3(cos(θ1 – θ2 – θ3)) 
 y = l1(sin(θ1)) + l2(sin(θ1 – θ2)) + l3(sin(θ1 – θ2 – θ3))
  • The inverse kinematic method used the geometrical features of the arm to find all the angles of the robotic arm describe in the diagram to the right
  • calibrations are made to correct the inverse kinematic method
  • Movements are included to ensure robotic arm doesn't bump in to anything
  • Movements are included to ensure robotic arm doesn't pick up two cards stuck together by the electrostatic force between them


Card Sorting Algorithms

Bucket sort.

The cards are sorted via one of the following methods chosen using the GUI:

  • Separate Colours
  • Separate Suits
  • Separate Values
  • Select-A-Card (pick cards you want the robot to find)
  • Full Sort (back to a brand new deck order)

The full sort algorithm is based on a bucket/postman and selection sort and occurs in three stages:

  • Cards are partitioned into buckets dependent on their value shown in the image to the right
  • Each bucket is emptied out progressively onto the board
  • Cards are selected from emptied out buckets in order and placed in sorted stacks dependent on their suit

Graphical User Interface (GUI)

Screenshot of the sorting GUI.

The GUI was implemented to enhance the projects interactiveness. The GUI aids in showing the viewer the image processing as it happens with live snapshots of images along with live decisions made by the computer vision on the value of the card. Similarly, due to the table showing the entire data structure of cards that have been scanned and sorted, the user can not only track the sorting process but ‘see’ what is below the top card in a given stack.

Project Significance

The final outcome of this project is a completely robust autonomous system. It is capable of using computer vision under various lighting conditions to sort playing cards. As a result of changes in processing, revisions were implemented for all three sub- systems for this continuing project.

By incorporating more sophisticated image processing techniques, the software subsystem has developed a reliable performance. Most physical constraints have been overcome by the various elements of the playing cards image processing algorithm. The algorithm is validated for recognising playing cards either via suit, rank, and colour identifiers or by a combination of these three.

This project acts as a proof of concept for the possible uses of combining computer vision and robotics. It proves that with more time and more advanced hardware the combination of the two could produce systems with great potential. Examples of industries which could benefit from these types of systems include; manufacturing, medical sciences, the military, artificial intelligence and the list goes on. The project also acts as a demonstration to entice future engineering students, and show off the possibilities of electrical engineering.

Team

Group members

  • Miss Yue Zhao
  • Mr Sijie Niu
  • Mr Jiahui Tang

Supervisors

  • Dr Brian Ng
  • Dr Danny Gibbins

Team Member Responsibilities

The project responsibilities are allocated as follows:

  • Miss Yue Zhao - Image Processing(Recognition)/Robotic Arm/Sorting Algorithms
  • Mr Sijie Niu - Image Processing(Recognition)/Image Processing(Extraction)
  • Mr Jiahui Tang - Image Processing(Recognition)/GUI


Resources

  • Bench 11 in Projects Lab
  • Lynxmotion AL5D Robotic Arm
  • Arduino Botboarduino Microcontroller
  • Microsoft Lifecam Camera
  • MATLAB
  • Laptop PC
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