Pulley Stage Tests

Preliminary tests of flat and spherical urethane pads using weights and pulleys.

-- SalomonTrujillo - 05 Dec 2005

• Circuit for IR emitter detector to sense the onset of sliding motion IREmitter-DetectorPair.doc

08 Dec 2005

Sal and Dan began testing 1st adhesive pad - 90A(?) circular pad of urethane glued to hard urethane backing, diameter ~?? Ran the following procedure:

• Pre-load with given weight
• Wait ~2min
• Remove Pre-load
• Wait given "relax" time
• Pull-off and record max force

The following tests were performed:

Tria l #	Pre-Load	Relax Time
1	100 grams	0 min
2	10 grams	0 min
3	10 grams	0 min
4	10 grams	0 min
5	10 grams	1 min
6	10 grams	1 min
7	10 grams	1 min

The data was inconsistent and the biggest problem was that we observed a clear relationship between the pull-off force and the amount of time it took to pull-off. A smaller pull-off force over a long period of time achieves pull-off and so does a bigger pull-off force over a short period of time.

To try to get more consistent results, Sal and I decided to pull-off the adhesive pad using an "impulse". The "impulse" in this case was simply just a really big weight dropped to the floor. The next problem we ran into was the high amount of adhesion that we were getting with this pad (up to 14N). It required weights on the order of ~2kg dropped from desk height to the floor, otherwise, we saw that the weight would bottom out on the string and hold for a second or two, and then pull-off would happen. This started causing other issues related to dangerous testing and things flying around.

So, decided to start using a smaller adhesive patch to reduce the magnitude of adhesive forces...

10 Jan 2006 - Maximum Adhesion under Negative Normal Impulse given Positive Normal Pre-Load

Sample - Urethane Patch of ~1.2" diameter glued to hard urethane backing
Substrate - Clean acrylic plate
Sampling Rate - 1000 Hertz
Experimental Procedure:

• Clean sample using damp cloth (wipe off any dirt/lint)
• Allow sample to air dry approximately 30 to 60 seconds
• Place sample on substrate and apply pre-load for approximately 1 minute
• Begin recording data from 6-dof force plate
• Remove pre-load and quickly apply large negative normal impulse
• After "break-away" stop recording

Experimental Trials - 5 trials each with pre-loads of 10g, 20g, 54g, 100g, 200g, 500g, and 1000g

• Data-1-10-06.jpg:
  

11 Jan 2006 - Maximum Adhesion under Negative Normal Impulse given Postive Normal Pre-Load and Side-Load

Sample - Urethane Patch of ~1.2" diameter glued to hard urethane backing
Substrate - Clean acrylic plate
Sampling Rate - 1000 Hertz
Experimental Procedure:

• Clean sample using damp cloth (wipe off any dirt/lint)
• Allow sample to air dry approximately 30 to 60 seconds
• Place sample on substrate and apply normal pre-load and side-load for approximately 1 minute
• Begin recording data from 6-dof force plate
• Remove normal pre-load but keep side-load, and quickly apply large negative normal impulse
• After "break-away" stop recording

Experimental Trials - Fixed Normal Pre-Load of 200g; Side-Loads of 10g, 20g, 54g, 100g, 200g

• Note: At 200g Side-Load, sample slipped before Negative Normal Impulse could be applied

• Data-1-11-06.jpg:
  

12 Jan 2006 - Coulomb Friction with No Pre-Loads

Sample - Urethane Patch of ~1.2" diameter glued to hard urethane backing
Substrate - Clean acrylic plate
Sampling Rate - 1000 Hertz
Experimental Procedure:

• Clean sample using damp cloth (wipe off any dirt/lint)
• Allow sample to air dry approximately 30 to 60 seconds
• Place sample on substrate and apply normal load
• Begin recording data from 6-dof force plate
• Increase side-load until sample begins to slip
• Stop recording data

Experimental Trials - Normal Loads of 0g, 10g, 20g, 54g, 100g, 200g

• Data-1-12-06.jpg: