pressure sensor findings and thoughts on future work
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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. - PowerPoint PPT PresentationTRANSCRIPT
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Pressure Sensor Findings and Thoughts on Future Work
Miguel PiedrahitaBDML5/13/04
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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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Chamber FabricationMold #1: Mold for Cavity Insert
Completed Cavity Insert (wax or hard urethane)
Mold #2: Mold for Membrane Exterior
Cavity Insert placed in Mold #2, leaving gap for membrane
Membrane cast from soft urethane
Mold #3: Mold for sealing off membrane
Membrane sealed with layer of hard urethane
Finished Chamber
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Testing
• Applied normal force from 0g to 1000g back down to 0g, in 50g increments.
• Several trials conducted on two different days.
Mass
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Results
Day 1
Day 2
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Sensor Performance (Day 2)
Sensitivity: 1.06 kPa/N, (1.06 V/N)
Accuracy: +- 0.33 N, or +- 0.35 kPa
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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
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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
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Array of Instrumented “Lamellar Fingers”
• Force distribution throughout foot – in tension & compression. Useful for evaluating foot design & performance.
• Surface roughness by comparing deflections
Embedded PVDF or
strain gage
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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)