Dry Adhesive Feet for QuadraRiSE

Active-control Actuation

Pull-pull actuation

• Mechanism allows toes to bend upwards (peeling) or downwards (pressing against surface).
• Benefits:
  • Pull-pull mechanism means more flexible cables can be used. This makes it easier to route cables along feet, through ankle, etc.
  • More force can be applied into actuation, as it does not depend on the stiffness of the cable - this is useful as robots increase in size, and cable stiffness cannot supply the necessary down force. Opens up possibilities for new ways of climbing (gripping with fingers?).
  • Individualized actuation for each toe segment, which makes it easier to reach around obstacles/bumps.
  • Only needs one servo to control.
• Things to think about
  • At any point, the foot has to have a height of 2 cm or so, or else the cables will bend too much and buckle. (Perhaps this can be fixed by using a more flexible cable.)
  • Toe segments have to be quite long - around 1.5 cm, for the same reason as above.
  • Range of motion in either direction is somewhat limited.
  • Two cable lines per foot and additional mechanisms increase overall size of toes.

-- RenFungYu? - 29 Jun 2006

Two-degree actuation toe, version 2.

• Changes/improvements over previous design.
  • Buckling tendency reduced.
  • Determined minimum diameter of cable turns to be around 0.7 cm.
  • Range of motion of peeling motion increased.
  • To minimize the number of cable turns, number of toe segments reduced to three, from previously planned six or seven. No significant decline in performance foreseen.
  • Maximum height of current design is around 2 cm.
  • Length of each toe is 9 cm. Width is 6 cm. Planning for three or four toes per foot.
• Hoping for design approval and to start production stage.
• See video here.

-- RenFungYu? - 06 Jul 2006

Non-rigid Frame

• Tested prototype foot using non-rigid frame. As normal and tangental (from load) forces act on the heel from the wall, the foot flexes outward, pushing it against the wall.

Non-rigid frame demonstration

Click here for video of mechanism.

• Need to build a stronger, more rigid model for testing QuadraRiSE-scale loads (1-2 kg).
• Height of foot needs to be reduced.
• SDM more reliable elastic joints or springs.

-- RenFungYu? - 26 Jun 2006