Any simple collision detection ideas?

hello people
I am trying to build a foot touch sensor mechanism for my hexapod walking robot using force sense resistors. The plan so far is to make
something simple like this:
http://mikael.geekland.org/foot_idea.png As you can (hopefully) see, it has only downward force detection..
But i would like bump sensing as well (for stair climbing etc)... I only need a simple bump/no bump signal but it has to be detectable from any angle and at least be near the foot/base of the leg (though preferably apply to a fair length of the leg).
I've come up with a number of ideas involving such things as using the aluminum leg's conductivity as part of a switch OR even moulding the foot in such a way, producing a twist force on the FSR's upon object collision BUT I can't seem to come up with anything practical (easy to make and wont break) and cheap enough!
So I was just wondering if anyone here had any general thoughts or ideas or has done something similar in the past. Any ideas would be appreciated!
Mikael
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Just brainstorming here...
What if each leg were dressed in a conductive (e.g. thin aluminum or copper) "sleeve", attached at the top via a short cylinder of foam, so that under normal circumstances it doesn't contact the leg. But when you bump into something, contact is made with the leg, closing a circuit. It's the same idea as a bumper skirt, but applied to each leg.
Another idea, if you have force feedback on your servos (e.g. you happen to be using Robotis Bioloid servos), is to just detect when the knee servo is registering unusual force. That probably means the leg is running into something.
HTH, - Joe
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I don't know anything about that "force sense resistor" you are using, but maybe you can just put the resistor at the top of the leg and attach the lower leg to the resistor. Any bump or force on the lower leg should then cause a detectable change in the resistor.
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Mikael,
Have you considered a pneumatic approach? You'd need an air-pressure sensor, some tubing, and an air-filled ball, tube, or even an irregular shape (e.g. an inflated dishwashing glove <grin!>).
As long as the air-filled "cushion" gets deformed far enough before your robot damages itself (or the wall, or the furniture, or a small pet or three) this should give you a remarkably flexible (in several senses) and omnidirectional "bump sensor".
This would probably be difficult to use on a really light robot, but I'd think anything that carried a reasonably hefty 12V battery would have enough mass to make this work.
Frank McKenney, McKenney Associates Richmond, Virginia / (804) 320-4887 Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all) -- "He can compress the most words into the smallest idea of any man I ever met." -- Abraham Lincoln --
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mikael wrote:

Just brainstorming ....
You have to ways to detect a colision: a) sensor on your skin feel the presure from the object b) your muscles get suddenly and increase in tension while not advancing
For a) you can go with various solution, others already gave you some ideas.
For b) however, you can figure it out from 2 hints: - the position (angle) transducer stop advancing - a sudden increase into the power ( amperage) consumed by motor
This 2 facts simultaneously tells you that it bumped into something, so your software can figure that out without need for "skin".
Just a thought...
MTM
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