VEX Robotics Curriculum

During the summer of 2018 we will be using the VEX Curriculum to model a summer mechanical engineering class.

To access the curriculum, visit https://curriculum.vexrobotics.com/home.html

 

Useful links for the class
Use for motor, gears and gear boxes, and wheel specs:
http://www.andymark.com/Default.asp
https://www.vexrobotics.com

 

 

Notes on the class can be found below.

Class #1:
July 9, 2018

  • The Engineering Design Process
    • Problem Statement
    • Brainstorming
    • Mockups and Prototypes
    • Testing
    • Did it work? If not, try again!
  • Intro to Engineering
    • Team dynamics
    • Write everything down!
      • This provides proof for later
    • Challenge ideas
    • Ranking system for engineers
      • W- Wish, not important but would be nice to include in machine
      • P- Prefer, important but would still work without it
      • D- Demand, must be included
    • Problem statements need to be clearly defined
      • Describe the action desired, not the potential machine
    • Design documentation
      • Troubleshooting, proof, info
      • Include failures and successes- this shows the results good and bad
  • Intro to Robotics
    • What is a robot?
      • Something that can be manufactured to do a job
    • Components:
      1. Body/frame
      2. Control system
      3. Manipulators
      4. Drive train
  • Speed, Power, Torque, and DC Motors
    • Classical mechanics
      • Speed- how fast, motion over time
      • Rotational speed- angular speed, angular distance over time
      • Acceleration- change in speed over time, rate of change of speed.
      • Force- accelerations cause forces which cause change in movement, direction, or shape
      • Torque- force directed in a circle
    • DC motors
      • Motor loading- motor can only apply torque in response to loading
        • The more torque, the slower the rotational speed
      • Current draw- load effects the current
        • More current means more power/speed

 

Class #2:
July 12, 2018

  • Mechanical advantage increases, speed decreases
    • More work, less speed
    • Keys contain the energy
  • Shafts
    • Points to points
    • Along the axis of motor
  • Spheres are keys (different shafts)
    • 3D
    • Most expensive
  • Bilateral tolerance
    • +0
    • -1
  • If gears have the same pitch, they can mesh
  • T=FD

 

Class #3
July 18, 2018

  • Went through pros and cons of different drive bases
  • Steps  of a drive base
    • Mechanical: voltage, current, speed, power
    • Mechanical advantage: friction, axel shaft, gear ratio
    • From friction: bushings and bearings
    • Sprockets (chain), pulleys (belts)
    • Wheels (translates everything to the ground)
  • Which direction should we go in?
    • Heavy design or kits?
    • Use Vex kits but design own base
    • What do we want to get out of the base?
      • Something new, not done before
      • Something to make and adjust later (modular design)
      • Something that will be challenging so we can learn more
      • Something with no limitations
      • A shifting transmission
    • Do we create our own problem to solve?
  • Solution
    • We need to think outside the box
    • Learn the basics first
    • Situationally adjust properties
  • Action Items
    • Understand CIM and 77Pro

 

Class #4
July 22,2018

  • Went over motor, gearboxes, and wheel specs from last class action items
    • Learned how to filter in excel
    • On some specs, power is N/A… Why?
      • Power is neither created or destroyed
      • Friction is limited
      • The power at the beginning is close to the same at the end
    • Forwards and backwards on wheels changes- motors set up with magnetic poles; North is stronger
  • Action Items
    • Figure out specs for what we want to build
      • Determine speed for a 24″x24″ base carrying ten lbs going a distance of 40ft. Then calculate and pick the best type of motor, gearbox and wheel diameter to go along with that

 

Class #5
July 24, 2018

  • Review calculations from last meetings action items
  • What are we going to do? We want to go 16ft/sec with a 24×24″ base carrying 10lbs by using…
    • Two Toughbox Mini’s gearboxes with a 8.45:1 ratio and flat plate
    • Six black Higrip 60A Wheels with a diameter of 6″ with a center drop
    • Two CIM 2.5″ Motors (am-0255)
  • Action Items
    • Create a bill of materials (BOM) with specs for the desired parts