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Pressure Sensor Findings and Thoughts on Future Work

Pressure Sensor Findings and Thoughts on Future Work. Miguel Piedrahita BDML 5/13/04. Pressure Sensor Motivation. Normal force information will be useful for climbing May be able to get dynamic signals related to slipping Pressure approach could integrate nicely with dry adhesive pads.

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Pressure Sensor Findings and Thoughts on Future Work

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  1. Pressure Sensor Findings and Thoughts on Future Work Miguel Piedrahita BDML 5/13/04

  2. Pressure Sensor Motivation • Normal force information will be useful for climbing • May be able to get dynamic signals related to slipping • Pressure approach could integrate nicely with dry adhesive pads

  3. Chamber Fabrication Mold #1: Mold for Cavity Insert Cavity Insert placed in Mold #2, leaving gap for membrane Completed Cavity Insert (wax or hard urethane) Mold #2: Mold for Membrane Exterior Membrane sealed with layer of hard urethane Membrane cast from soft urethane Mold #3: Mold for sealing off membrane Finished Chamber

  4. Testing Mass • Applied normal force from 0g to 1000g back down to 0g, in 50g increments. • Several trials conducted on two different days.

  5. Results Day 2 Day 1

  6. Sensor Performance (Day 2) Sensitivity: 1.06 kPa/N, (1.06 V/N) Accuracy: +- 0.33 N, or +- 0.35 kPa

  7. Observations • Drawbacks to practical implementation • Difficult to fully bleed air from system – affects repeatability • Size of system limited by rather large sensor • Likely not effective for adhesion forces (front feet) • Other technologies may be better for normal force measurement • Strain gage • Piezoelectric

  8. Thoughts on Future Work:What do we want from RiSE sensors? • Climbing-related information: • Foot impact events • Slip events • Tangential & normal forces on each foot • Measure of penetration of claws/engagement of dry adhesives (i.e. a way to predict likelihood of slip) • Surface-related information: Information about climbing surface would be useful! We could then tailor aggressiveness and climbing strategy (claws vs. dry adhesives) accordingly • Inclination • Surface hardness • Roughness

  9. Array of Instrumented “Lamellar Fingers” Embedded PVDF or strain gage • Force distribution throughout foot – in tension & compression. Useful for evaluating foot design & performance. • Surface roughness by comparing deflections

  10. Why Lamellar Fingers? Good Question! • Examine advantage of lamellar structures • Work on optimizing geometry for front feet and rear feet • Front feet: Maximize surface contact, minimize stress at edges & Poisson shrinkage • Rear feet: Maximize shear force • Solid mechanics, FEA, experiments (RoboToe)

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