Six Wheel Tank Drive

Lower Centre Wheel

  • Add a set of wheels in the centre of the robot, slightly lower than the outer wheels
    • What does this do?
      • Divides the effective wheel base (L) in half
        • Turns the robot into two 4WD sections, depending which half the CoG is on, whether the robot is accelerating/decelerating, or pushing or pulling a game piece or opponent
      • Reduces FN on outer wheels
        • The closer the CoG is to the middle of the robot, the lower FN (and therefore FF) will be on the outer wheels
  • The result?
    • A very smooth turning robot

Example

  • Again we get
    • FN,1 / FN,2 = d2/d1
  • However, this time d2 should be much less than d1
    • Therefore F1 should be much less than FN,2

Recall from 4WD

  • With 4WD, the closer the CoG was to the middle the closer the robot rotated on its centre
  • However, the closer the CoG was to the middle, the more force was required to overcome friction from the wheels
  • d1/d2 = μ2 · FN,2 / μ1 · FN,1 = FF,2/FF,1
  • τdriven = 2 · FF,1 · d1
  • τdriven = 2 · FF,2 · d2

Centre of Gravity Position

  • The same equations apply to 6WD drive, BUT
    • The closer the CoG is to the middle the closer the robot rotates on its centre
    • AND, the closer the CoG is to the middle, the less force is required to overcome friction from the wheels