Robot design 1 - Synchro Drive

Picture 1 Rendering of the prototype with POV-Ray Picture 2 Bottom view of the mockup Picture 3 Top view of the mockup

Features

  • One motor for steering and one for turning
  • Chassis remains in the same orientation while the robot turns
  • High-ish ground clearance
  • All-round bumper (not shown)

Pros

  • Accurate turning
  • Accurate moving straight
  • Motors do not need to synchronise, which would be more unreliable
  • No caster to drag and reduce reliability

Cons

  • Only one motor's power in both turns and movement
  • Lots of gears between which backlash occurs
  • Unstable

Robot design 2 - Omni-wheel caster

Picture 1 Top view Picture 2 Detail of wheel Picture 3 Light sensor arrangement

Features

  • Omni directional caster wheel
  • Large wheels
  • Low COG
  • 2 light sensors
  • Arm motor

Pros

  • Accurate moving straight
  • Caster designed to eliminate unwanted friction
  • Faster robot movement due to large wheels

Cons

  • Tests showed the turning was inaccurate, as the omni-wheel tried to move to one of 12 positions
  • Difficult to attach an arm of any kind
  • USB port obscured

Robot design 3 - Cube

Picture 1 Front view Picture 2 Side view Picture 3 Rear view

Features

  • Ball caster
  • Large wheels
  • Arm motor
  • Vertically mounted motors

Pros

  • Ball caster causes far less erratic behavior than a conventional caster
  • COG is over the wheels, so friction on the caster is further reduced
  • USB port accessible

Cons

  • Screen is at an inconvenient angle
  • The robot "rears" up as it accelerates

Robot design 4 - Forklift

Picture 1 Front view Picture 2 Details of arm Picture 3 Ball caster

Features

  • Ball caster
  • Large wheels
  • Arm akin to a forklift
  • Vertically mounted motors

Pros

  • Ball caster
  • COG is over the wheels again, but not so much that the robot tips over
  • More stable than design 3

Cons

  • Too long for reasonable manoeuvrability

Robot design 5 - Regional heat Final Design

Picture 1 Side view Picture 2 Details of the ball caster Picture 3 Top view

Features

  • Easily interchangeable attachments
  • 2 touch sensors
  • 2 light sensors

Pros

  • Ball caster
  • Stable
  • Weight over wheels

Cons

  • Insufficiently rigid - needed some work
  • Not as reliable when turning as it could have been
  • Moves counter-intuitively