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Design and Build of a Robotic Ping Pong Player. Team Members: Brett Morris, Jarrad Springett, Jamie Mackenzie, Ryan Harrison Supervisor: Frank Wornle. Introduction Presentation Jamie Background Project Outline Initial Research Project Goals Arm Design Frame Table Brett Modelling

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design and build of a robotic ping pong player

Design and Build of a Robotic Ping Pong Player

Team Members:

Brett Morris, Jarrad Springett, Jamie Mackenzie, Ryan Harrison

Supervisor:

Frank Wornle

seminar structure
Introduction

Presentation

Jamie

Background

Project Outline

Initial Research

Project Goals

Arm Design

Frame

Table

Brett

Modelling

Dynamics

Control

Jarrad

Vision System

Individual Camera Calibration

Combined Camera Calibration

Real-time Image Processing Engine

Ryan

System Overview

Hardware Overview

Microcontroller Overview

Summary

Conclusion and Future Work

Questions?

Seminar Structure
background
Background
  • Began in AT&T Bell Labs in the 1980’s
  • Constructed under ‘ROBAT’ rules
    • Slows game
    • Controls game
  • Not a purpose designed and built robot
  • Several other attempts
    • Types of robot (XY plotter, Japanese version)

Andersson (1988)

project outline
Project Outline
  • A robot that plays ping pong?
  • Totally independent of human interaction
  • Vision, brain and limb all in one package
  • Use the increase in technology to improve on the design from AT&T Bell Labs
  • Combining together all parts
  • Working in unison

Megaspin.net (2005)

initial research
Initial Research
  • Book by Russell L. Andersson
  • No specific information published
  • Each section treated separately
    • Mechanics
    • Vision
    • Control
  • Built up our own library of references

MIT Press (2005)

project goals
Project Goals
  • Vision System
    • Detect a ping pong ball and predict its trajectory (minus bounce) to within an area no larger than the robot bat with good repeatability.
  • Control System
    • Plan a collision free arm trajectory and generate suitable control signals for local position/velocity control using microprocessors.
  • Mechanical System
    • Design a robot arm which is capable of reaching all required positions and orientations within its workspace without undesired bending/flexing motion. Selection of motors with sufficient power to achieve this.
arm design
Arm Design
  • Starting from bat and finishing at the base
  • Loop which needs to be broken
  • Considerations:
    • Weight
    • Vibration
    • Workspace
    • Shot Angle
  • Based on other robot designs

Adept (2005)

final design
Final Design
  • Major Features:
    • Parallel
    • Light weight materials
    • Motor selection
    • Motor placement
    • Bearings
    • Face-on design
    • Couplings
    • Pulleys
  • Not a final design and should be remodelled next year
motors
Motors
  • MAXON MOTORS
    • Light weight
    • Powerful
    • Gearbox combination
    • Encoder combination
  • 1 x servo motor
  • 2 x 6.0W motor
  • 2 x 70W motor
  • 1 x 90W motor
pulleys
Pulleys
  • Allow the robot to remain parallel
  • Reduce the amount of inertia on later motors
parallel construction
Parallel Construction
  • Allows the robot to make symmetric movements
  • Shares the load between all motors
  • Simplifies kinematics
robot frame
Robot Frame
  • Will bear the weight of the robot
  • Independent of all other physical systems to isolate vibration
  • Damping system to reduce vibration
  • Cage to prevent accidental human contact
robot table
Robot Table
  • Complies to the rules of “ROBAT”
  • 0.5m squares to hit through
  • Slows down and controls match
  • Could possibly be built in two halves
modeling dynamics and control
Modeling, Dynamics and Control
  • Kinematic Design
  • Dynamic Modeling
  • Control System
  • Real-time Implementation
robot kinematics
Robot Kinematics
  • Finding and defining an arm design that is capable of playing the required shots
  • Generating trajectories that coordinate all six degrees of freedom to produce the desired motion at the end effecter
dynamics
Dynamics
  • Calculated using Newton-Euler Equations
  • Generates the torques acting on each link given each links state
  • Requires a detailed physical model of the robot
dynamics18
Torques required to perform the desired trajectory calculated for each robot iteration

The max torque from each joint was used for motor selection

Dynamics
real time implementation
Real Time Implementation

Check Cameras

Check for users

commands

Speed

300 cycles

per second

Convert torques

To current

Calculate

new trajectory

Evaluate desired

joint states

Evaluates joint

torques

Receives

actual joint states

Calculates new

set point

vision system
Vision System
  • Objective
    • Transmit ball location to control computer, quickly and accurately
  • Application
    • Real-time 3D sensing and prediction for robotic applications
  • Components
    • Individual camera calibration
    • Combined camera calibration
    • Real-time image processing engine
individual camera calibration
Individual Camera Calibration
  • Objective
    • Generate a vector associated with each camera pixel
  • Vector field generation technique
  • Accuracy
individual camera calibration28
Individual Camera Calibration

Primary screen

Multimonitor output

individual camera calibration29
Individual Camera Calibration

Multimonitor output

Primary screen

combined camera calibration
Combined Camera Calibration
  • Objective
    • Determine camera position and orientation transforms with respect to each other
  • Camera transform generation technique
  • Accuracy
real time image processing engine
Real-time Image Processing Engine
  • 2D image preprocessing
    • Blurring reduces high frequency image noise
    • Decontrasting reduces lighting effects
  • Centroid identification
  • Maps 3D points from multiple vectors
  • Serial or TCP/IP Output
real time image processing engine34
Real-time Image Processing Engine
  • 2D image preprocessing
    • Blurring reduces high frequency image noise
    • Decontrasting reduces lighting effects
    • Edge detection algorithms created for more detailed scene analysis
real time image processing engine36

Shortest Distance Between Correlated Skew Lines in 3D

Ping Pong Ball

Stereo-Derived Distance

Camera Axis

Camera Axis

Real-time Image Processing Engine
  • Mapping 3D points from multiple vectors
system overview

Vision System

Control System

Micro-

controller

System Overview

Vision System

Control System

Microcontroller

Business Link, (2005)

Electric Motor Warehouse, (2005)

Unibrain, (2005)

communication
Communication
  • Simple Serial Interface
    • Control system acts as “host”
    • One connection to microcontroller
    • One connection to vision system
  • Data from vision system sent at 30Hz
  • Data to microcontroller sent at 300Hz
hardware overview
Hardware Overview

Analog signal

8bit PWM

Microcontroller

Microcontroller

Low pass filter

Low pass filter

16bit PWM

Desired currents

Current control

Current control

10bit Input

Amplifier

Servo Motor

Encoders

DC Motors

5V Amp

240V AC

microcontroller overview
Microcontroller overview

[Return]

Main (idle)

Update display

Low priority

tasks

Comm processing

Receive/send data

Decode received data

Update required currents

[Data received or transmission ready]

[Return]

[Encoder movement]

[Return]

[Return]

Timer tick

Guaranteed tasks

Motors updated

Update soft. timers

Encoder interrupt

Process encoder state

Update joint positions

[Return]

[Timer

interrupt]

[Encoder movement]

[Return]

[Encoder movement]

low priority

medium priority

high priority

microcontroller overview41
Microcontroller overview
  • Processes encoder data rapidly, at a rate of order 10kHz per encoder.
  • Receives communication data at 5000Hz, and processes this data at 300Hz.
  • Updates the motor output at 600Hz.
summary
Summary
  • Control kinematics/dynamics and simulation
  • Robot design
  • Vision system
  • Control circuitry
conclusions and future work
Conclusions and Future Work
  • Feasible design
  • Requires more time to complete
  • Viable project for continuing work