Functional Design

Brainstorming

  • No bad ideas
  • Think outside the box
    • Read the rules carefully
    • Cantilevering, "squish the fish"
  • Mechanisms as well as overall designs
  • Keep the ideas!
  • Playing field model or mock-up very useful

Prototyping

  • Proof of concept
  • Size
  • Motor / piston capability
  • Shape
  • Motion
  • Try several ideas if possible
  • Focus prototyping on unknown areas

Final Design and Build

  • Design and build final mechanisms
  • Keep monitoring robot weight
  • Make sure to buy or order necessary parts before you need them
  • Check for interference between components
  • Form sub-groups
  • Miscellaneous tip: Don't get shavings in the speed controllers!

Testing and Practicing

  • Test beyond what the robot will likely experience
  • Test many times in different circumstances
  • Reinforce weak areas
  • Tweak components
  • Build spare parts for suspect components
  • Practice!
    • Different scenarios
    • Close to competition circumstances

Principles

  • Simplicity
    • Fewer things to fail
    • Easier and faster to build and repair
    • Lighter
    • More durable
    • More elegant
  • Design for assembly and disassembly
    • Leave bolts exposed
  • Durability
    • Simplest mechanisms often the most durable
    • Robot will likely go through much more stress than you expect
      • Different driving in a competition situation
      • Collisions with other robots
      • Unanticipated situations
    • Examples: twisted shaft, sheared pins, latch bracket, arm chain, steering mechanism
    • Careful with welding
  • Weight distribution
    • Keep as much weight as low as possible
    • Put weight over the drive wheels for most traction
    • Battery is a large component of the total weight (14 lbs) and can help move center of gravity
  • Vibration
    • Robots go through a lot of vibration, especially at competitions
    • Bumpy wheels increase vibration
    • Use Pozi-Lok or other lock nuts to avoid nuts falling off
    • Check bolted connections and shaft collars frequently
    • Check the antenna!
  • Multi-functionality
    • Cuts down on weight, complexity, building time etc.
    • Slight modification can often lead to a new, useful function
    • Be wary of conflicting requirements
    • Example: arm for ball manipulation and hanging
  • Consolidation
    • Multi-motor gearboxes
    • Common shafts
  • Theory
    • Classroom theory really can be useful
    • Eliminate infeasible ideas quickly
    • Free-body diagrams
    • Kinematics and dynamics
    • Gear calculations (torque and speed)
    • Electrical power consumption
    • Vector geometry
    • Trigonometry

Computer Aided Design (CAD)

  • Very useful in certain situations
    • Components needing high accuracy
    • Complex shapes and assemblies
  • Can be used for virtual prototyping
    • Useful for checking for interference
  • Often too slow for simple components

Useful Components

  • Bronze bushings
    • Cheaper, more rugged than bearings
    • More friction
  • Aluminum profile (e.g. Bosch)
    • Very fast, versatile frame construction
  • Aluminum angle / L-channel
    • Extremely versatile and useful
  • Delrin, HDPE, nylon, Lexan etc.
    • Sliders, rollers, spacers
    • Lighter, but weaker and less rigid than aluminum
    • Easy to cut, but can be difficult to machine

Basic Materials

  • Nuts (Pozi-Lok) and bolts
    • Standardize if possible
  • Steel shafts of different sizes
  • Shaft collars
  • 1/4" aluminum plate
    • Be careful about weight
  • Aluminum square tubing
  • Surgical (latex) tubing
  • PVC / ABS tubing
  • Cable ties (no tape allowed!)