Notes on Platform Integration

Tony Tetherless () key principles

• Maximize the points of engagement
  • Many toes / spines
  • Independent compliance of all spines
    • Normal-to-wall
    • Axial (parallel to wall - up-and-down)
    • Keep spines as close as possible to wall
  • Lower forces on engagement points allow greater probability of engagement
    • Allows for smaller tip radius w/o spine wear, can engage on smaller asperities
    • Reduces chance that substrate will break
• Distribute the force to contact points
  • Sprung toes / spines
    • Possible locking after appropriate contact
• Points of engagement consist of mechanical interlocking between spines and asperities
• Minimal pitch back moment
  • Body is close to wall
• Lightweight body
• Engagement strategy for hard surfaces is to scrape and search for a foothold
• Disengagement trajectory is the reversal of the engagement trajectory -- at the spine angle

Sticky Bot key principles

• PSA as substitute for dry adhesives
• Tripod for stability
• Front/rear leg differentiation
  • Front legs: primarily adhesion to prevent pitch-back
  • Rear legs: primarily forward thrusting (shear climbing force)
• Engagement/disengagment strategy for PSA
  • Engagement: small contact area between roller and wall leads to high local pressure that leads to good tape engagement
  • Disengagement: Peeling from top causes detachment force (in normal-to-wall direction) on the leading edge of the tape.
• Body compliance: minor adaptation to surface curvature

RiSE? platform v01 key principles

• Front/rear leg differentiation
  • Front legs: primarily provide adhesion through foot design and leg trajectory
  • Rear legs: primarily shear climbing force through foot design and leg trajectory
• Compliance
  • Lower leg spring flexures
    • Allows for early engagement, allows for build-up of inward shear force.
    • Provides roll compliance to conform foot to surface at different wing angles.
  • Yaw compliance in foot
    • Allows for fixed foot position during stance.
    • Dactyl foot: free to rotate in yaw due to point contact
    • SDM foot: torsional yaw flexure to return foot to nominal orientation during flight phase.
• Inward pulling force keeps claws engaged
• Basic difficulties with platform:
  • High weight and pitch-back moment
  • Operating at 50-70deg wing angles leads to:
    • strong coupling of lower leg spring flexures
    • pulling foot away from wall is coupled to moving foot laterally outwards

StanfordTestTrack? key principles

• Engagement
  • Trajectory aligned with claw angle
  • Engage early to load lower leg spring flexures during stance phase
• Disengement
  • Trajectory aligned with claw retraction angle
  • Disengage at point in trajectory where lower leg spring flexures are unloaded

Red ideas are things to include in the future path of the RiSE? platform
Blue ideas are things to maybe include

Ideas for Future RiSE? Platform

• Tony Tetherless spined feet -> incorporate into new foot design
  • many points of engagement
  • compliance - axial and in/out of wall
• Sensing to determine surface characteristics
• Feet possiblities:
  • Highly compliant spines, can move away from wall to engage PSA
  • active PSA engagment/unpeeling
  • actuation seems necessary
• Need very soft yaw compliance for foot to rotate easily during stance (for both spines & PSA to maintain consistent orientation to surface)
• Roll compliance to align foot to surface regardless of wing angle
• Long tail and/or long legs reaching forwards?
  • Both effectively reduce the amount of adhesion needed to counteract pitch-back by increasing the moment arm of the adhesive force
  • Long tail: All legs can/should? provide adhesion, resulting in lower adhesion force by each leg.
  • Long front legs: Front & mid legs now must provide all adhesion, thus requires larger adhesion force at each leg. Rear legs have normal force into the wall, which allows for more effective generation of shear force for upward motion.

-- AMcClung? - 27 Jul 2004