"Propelling GCC towards greater achievements in the 21st century"

GCC Robotics Academy


2013 - 2014 Capstone Team

Outline

Vision
Mission
Goals
Approach
Organization
Results
Conclusion

Vision


Let's build something "legit"


Mission


Creating a team

Pursuing an opportunity

Goals

                    Specifics
                    Measurable
                    Achievable
                    Relevant
                    Timely

specifics
 3D Printer

Robotic Arm Prometheus

measurable


Producing tangible results periodically

Achievable


Time management

Reasonably challenging projects

Passion 

Mentor help

Relevant


Inter-disciplinary

Pertains to our studies at GCC

Enhancing our skill sets for internships/future jobs

Timely


  • Team Meetings: Every other Friday @ Noon
      • Progress report
      • Team coordination
      • Goal Setting

  • Sub-Teams had additional individual meetings
 


Approach


Active Learning by
Productive Struggle

  1. Research
  2. Reference Design: Bukobot
  3. Designing a New Printer
  4. Trial & Error
  5. Mentor/Team Support

Organization

PROCESSES


Self-Teaching 

Communication

Leadership

Engaging GCC

 Self-TEACHing


Experiencing New Tools

Experience by Trial & Error

Documentation

 

Communication

Engaging GCC


Engaging Faculty

Inspiring Students
 


Results

Values Learned:




Leadership 
Teamwork
Organization skill-set
Plan/Execute
Commitment
Time Management





Communication Platform/Skillset
Problem Solving 
Abstraction
Engineering Skills
Technical Documentation
Presentation Skills

 

Conclusion

Special Thanks:

Technology & Aviation Division

Physical Sciences Division

Purchasing Office

GCC U.S. Department of Education Grants Team

BREAK!



GCC ROBOTICS ACADEMY


2013 - 2014 Capstone Team

Project Overview


  • The robotic arm - "Prometheus"

  • Continued project from previous group
    • Non-functional state

  • All the code as well as electrical schematics and STLs for the 3D printed parts are available in the Github repository

    github.com/gcc-robotics/prometheus

Organization

No formal organization due to small team size

Assistance from previous group members
and Capstone Project Mentors


Requirements

  • 4 degrees of freedom

  • Student designed

  • Custom mechanics

  • Custom electronics

  • Custom software

    • Mechanical Overview


    Robotic Arm


    Robotic Arm

    -Designed in Solidworks and 3D printed in Ultem

    -Moving joints: Base, Shoulder, Elbow, Forearm, Claw

    -Joint mechanics include: Bevel Gears, Worm drives, Direct Shaft Drives and Servo's

    The process

    • Identifying existing problems
       
    • Designing solutions

    • Executing the solution













    Electrical overview

    Full schematic diagram


    Block diagram


    ARduino pro Mini


    • Breakout board of the Atmega 329
      • 5V 16MHz version
      • Atmega 329
      • Reset push-button
      • Indicator LED
    • Communication
      • I2C
      • SPI

    PWM generator


    • Adafruit breakout board - PCA9685PW
      • Communicates with Arduino via I2C communication port
      • 16 individual outputs which are ordered into triplets: 2 control signals, 1 PWM signal
        • Control signals govern motor direction and "braking"
      • All outputs are 5 V logical signals

    Motor drivers


    • Convert 5 V Logical signals to high current 12 V drive signals
      • Control signals are not amplified
    • VNH2SP30 - dual H-Bridge motor driver carrier
      • capable of supplying 30A of current to the motors
    • MC33926 - standard H-Bridge motor driver carrier
      • capable of supplying 3A (5A peak) of current to the motors

    Encoders




    • Absolute, Analog Voltage, Continuous Rotation
      • 0 V to 5 V
      • Voltage directly proportional to angular position of encoder shaft

    Multiplexer

    • CD74HC4067 - 4 bit, 16 input multiplexer
      • Multiplexes or "converges" 5 independent encoder signal inputs into one output pin
      • Reduces number of Analog pins required on the microcontroller
      • Each input from 0 to 15 corresponds to a 4 bit binary address

    the Claaaw

    • VEX Robotics kit component
    • Low voltage motor can be run on 5V signal
    • Run with half L298 H-Bridge

    Software overview


    software map

    prometheus-remote-control-diagram.png
    • The control software for Prometheus
      • 2 Microcontrollers
      • Arduino - low level controls for the arm
      • Raspberry Pi - higher level functions
      • Communicate over Serial



    Arduino software

    • SistineChapel - Arduino Software
      • motorController - lowest level of code and directly controls the in/out pins 
      • multiplexer - next level of code to control the multiplexer on the circuit board
      • robotArm - contains the basic functions to control the movements of the arm
      • PMotorSpeed - contains proportional calculations for the PID controller
      • PIMotorSpeed - inherits PMotorSpeed class and contains integration calculations for the PID controller
      • commandProcessor - communicates between the Arduino and Raspberry Pi
      • debugger -  test and debugging purposes


    Raspberry Pi Software


    • Narthex - Raspberry software

    • Composed of two main parts
      • Server side
      • Client side

    Narthex server side

    • Narthex server side uses Python

    • Bridges communication between the Arduino and the web interface

    • Arduino -> Serial over USB

    • Web Interface -> WebSocket

    • Designed to handle multiple remote control interfaces at the same time

    Narthex Client side

    • HTML5 browser based interface
      • 10.33.0.2

    • Javascript for communication and 3D rendering

    • Full 3D rendering

    • PID tuning

    • Debugging


    Systems Challenges


    • Communication 
      • even within smaller group difficulties were found communicating
    • Meeting Times 
      •  due to individual schedules being different, to accommodate time to meet was difficult
    • Bill of Materials
      • Inefficiency in placing orders
    • Documentation
      • Lack of documentation from previous group
      • Current documentation is on Google Drive and being updated

    Mechanical Design Challenges

    MECHANICAL DESIGN CHALLENGES

    -Broken parts

    -Unorganized drawing database

    -Modifications made to parts without documentation

    -Material costs

    -Keeping the project within a reasonable budget

    MECHANICAL DESIGN CHALLENGES

    - Running into two additional problems after solving one


    - Using as much of the existing structure as possible to keep costs reasonable


    - Collateral damage from failing parts

    Electrical DESIGN CHALLENGES

    position

    • Encoder readings inaccurate
      • Arduino appeared to never read the full range of the analog encoder
      • The incoming signal never reached 0V or 5V
    • Encoder value is measured by the Arduino with an Analog to Digital Converter (ADC)
      • ADC Type : Sample and Hold
        • Key Concept of ADC Type : Successive Approximation
          • Key Electrical Components : Input Capacitor and large series resistor
    • ADC Resolution is 10 bit
      • 1024 possibilities (5V/1024)
        • Resolution is 0.0048828 V / bit

    ADC input

    • Capacitor Charges to VIN
    • Capacitor Charge Time tau = R*C
      • Atmel datasheet reports input capacitor 14pF, and series resistor 100M Ohm
    • t = 0.0014 S
      • @ t, VC = 63.2% VIN
      • @ 5t, VC = 99.3% VIN, 5t = 7 mS
    • Capacitor cannot reach 100% VIN
      • Given ADC resolution of 0.0048828 V/bit , closest approximation of VC = 99.98% VIN = 1024



    ADC Input


    • Capacitor takes 7 mS to reach 99.3% VIN
      • Arduino frequency is 16MHz (62.5 nS / Ass'y Instruction)
      • 112,000 Assembly Instructions
    • Microcontroller checks input voltage too early
      • Capacitor does not have sufficient time to charge up to 99.98% capacity

    Software DESIGN CHALLENGES

    Arduino Challenges

    • Difficulty achieving precise movement

    • Vex Claw support is hacked together

    • Implementing the derivatives in PIDs

    • Choice of microcontroller

    Raspberry Pi Challenges

    • The web client is not fully tested and has several issues remaining

    • Features for multi-client syncing have been built but are not finished

    • Remote control interface does not take collision detection into account

    • Difficult to control for inexperienced 

    Results


    Working
    Robotic
    Arm

    Mentors

    Program Director: Voden, Tom

    Mechanical Mentor: Toorian, Armen 

    Electrical Mentor: Ohanian, Richard

    Software Mentor: Isayan, Sevada

    Student Mentor: Pailevanian, Torkom

    credit


    Mechanical:
     Zograbian, Roman

    Electrical:
     Hovhannisyan, Ernest
     
    Software:
     Kim, Sung Hoon
    Litomisky, Marek

    3D-Printer


    Mission


    Duplicate functionality of 3D printer used to construct arm parts


    Functional Block Diagram: Printer


    Mechanical
    Electrical
    Electrical and Mechanical
    Software

    Requirements

    • Visually appealing
    • Modular 
    • 24" x 24" x 20"
    • Print volume maximized 
    • Print various materials
    • Dual extruders, capable of independent motion  
    • Capable of cooling the bed

    Engineering Approaches

    • Mechanical Team 
        • Prototype and Revise
    • Electrical Team
        • Replicate Functionality and Improve
    • Software Team
        • Expand on Mature Codebase

    mechanical Overview




    Preparation

    Research

    Learning to Design

    Buying/Building a Printer Kit

    Testing the Printer

    Deciding Features to Improve

    purchasing


    • Finding necessary parts

    • Cost efficiency

    • Defining quantities

    • Compiling Bill of Materials

    • Placing orders in a timely maner

    Design


    • Using computer aided design tools

    • Dimensioning custom parts

    • Considering size expansion

    • Improving stability

     

    manufacturing

    Technical


    Structure


    Motion


    Heat Bed


    Extruders

    Structure

     

    Structure

     

    Components:
    • Single Beam
      • 1"x1"x18"
      • 1"x1"x22"
    • Double beam 
      • 2"x1"x24"
    • Corner Connectors

    Motion


    Motors


    Z-Axis


    Y-Axis


    X-Axis

    Motors

    Motors

    Axis Motors
    • Anaheim Automation
    • Nema 17
    • Length: 1.87 in
    • Lead wires: 4
    • Using: 8

    Extruder Motors
    • Kysan Electronics
    • Includes gear box
    • Length: 28+47mm
    • Lead wires: 4
    • Using: 2

    x-Axis

    Fastened to Y-axis
    Driven by rack and pinion system
    Two individual motors for each extruder



    y-Axis

    • Initial design: Belt drive system
    • Changed to same drive system as Z-axis
    • Driven by 2 motors
    • Zero-Backlash nut

    Z-Axis

    • Integrated into the structure.


    • Custom 3D printed linear guide.

    • Driven by lead screw/worm gear-nut system.

    • Driven  by 4 motors


    Custom Linear Guides









                           McMaster's                                        Custom Design

    Z-Axis

    Z-Axis

    Lead Screw/nut system

    • 1/4"-20 Lead screw
    • Coupled to motor using plastic hose
    • Nut: Printed and tapped

    Heat Bed

     

    heat bed

    Components:
    • Heat sensor
    • Glass w/ clamps
    • Heat bed
    • Aluminum plate
    • TEC
    • Heat sink
    • Fan
    Motion:
    • Z-axis

    Extruders


    extruders

    Components:
    • Extruder carriage
    • Lock Mechanism
    • Brass barrel
    • Resistor Block
    • Nozzle
    Motion:
    • X-axis
    • Feeds filament

    testing


    Trial & Error

    Challenges

    • Learning Essential Software

    • Time Constraints

    • Binding of Mounts

    • Accounting for Tolerances

    • Finding Specific Parts

    • Incorrect Parts Ordered

    • Manufacturing Defects


    Continuous progress

    Add linear bearings

     
    More efficient guide design

     
    Change Y-Axis motion system


    Complete bill of materials for future purchasing/building



    Electrical Overview


    Design


    -Old vs New Schematic Diagrams

    -Block Diagram

    Block Diagram




    the build


    -Microcontroller

    -Motor Drivers

    -Heaters & Fans




    temperature

    • Heater Bed

    • Peltier Plate (TEC)
      • Cools heat bed, requires 3 Amps

    • Heater and Thermistor Board
      • Heat up extruders, TEC place, & control the fans
      • Measure temperatures of 2 extruders & electronics area for safety 

    heater bed

    • Etched PCB Resistive heater
     

    • Calculated current of 45 A


    • Driven by MOSFET
      • Requires independent PCB with large surface area of copper to supply sufficient current
      • Requires larger flyback diode

    tec and block

    • TEC
      • 3 Amps max power
      • Engaged when print job is finished



    • Heater Block
      • Resistive heater
      • 3 Amps max power

    Temperature sensor



    • 10k Ohm Thermistor

    • NTC Type

    • Non-linear temperature vs. resistance curve

    • Requires 5 V Analog Voltage and GND



    TESTING

    • Testing was done in modules

    • Approach:

    1. Tested each component by itself to make sure it's working  properly
    2. Tested as an individual circuit 
    3. Tested as a system

    DOcumentation

    • Documented after every milestone





    • Recorded progress in Electronics Guide
      • most relevant/useful documentation transferred to Google Doc



    • Used Google Doc 
        • easy access and editing
        • team was already acquainted with it

     

    Software Overview

    Design Goals

    • Code was forked from ErikZalm/Marlin

    • Added functions
      • Dual independent extruder carriages

    • Main focus
      • Control movements in all axes with Repetier-Host software

      • Ability to find the start position (origin) with endstops

    Design Challenges

    • Understanding massive starting code base 
      • Dozens of classes
      • 30+ thousand lines of code

    • Dual extruder carriage with independent movements
      • Non-standard 3D printer feature

    • Time constraints

    Testing Procedures

    • Had difficulty testing as a system
      • Requires a whole functional unit

    • Began testing individually
      • Wrote simple code to test individual components 

    • Tested modules as they were completed

    Results

    Mentors


    Program Director: Voden, Tom

    Mechanical Mentor: Toorian, Armen 

    Electrical Mentor: Ohanian, Richard

    Software Mentor: Isayan, Sevada

    members

    Mechanical Team:
    Atkinson, John Paul
    Khajatourians, Rene
    Talverdian, Tamara 
    Electrical Team:
    Hovhannisyan, Ernest
    Kim, Sung Hoon
    Safarian, Vivian
    Software Team:
    Kim, Sung Hoon
    Litomisky, Marek 
    Systems:
    Saleebyan, Skyler

    question & answer

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