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From: wiml@milton.u.washington.edu (William Lewis)
Newsgroups: comp.robotics
Subject: Re: ideas for inclination sensors
Message-ID: <9464@milton.u.washington.edu>
Date: 18 Oct 90 03:38:59 GMT
References: <3717@media-lab.MEDIA.MIT.EDU>
Organization: University of Washington, Seattle
Lines: 47

In article <3717@media-lab.MEDIA.MIT.EDU> fredm@media-lab.MEDIA.MIT.EDU (Fred Martin) writes:
>robots must do is climb an inclinated plane.  Thus, I'm soliciting
>all of you robot hackers for ideas on inclination sensors.

  Disclaimer: I've never built one of the following, so it may or may
not be feasible. But it's got to be easier than attaching IR rangefinders
to a pendulum bob =8)


  I have, several places, seen designs inclinometers (is that a word?) that 
work by having two C-shaped parallel plates in a thin container, partially
full with liquid. As the angle of the container changes, and therefore
the angle of the liquid's surface with the plates, the electrical
characteristics will change, depending on the liquid you use. You could use
a conductor and measure resistance, or a dielectric and measure capacitance
(say, an oscillator controlled by the cpacitance on the plates could
run a counter, which is cleared and read at timed intervals to make a
sort of frequency counter). The only problem I can think of offhand
is sloshing, but you'd get swinging effects in a pendulum, too. Choosing
the right liquid (whatever it may be) should reduce that.

   A diagram:

            _
           | |
           | |   <-- plates
          /  /
  . . .  /  / . .  <--liquid level
  _____/  / 
 |______/


>One obvious such thing is a mercury switch.  In fact, I plan on giving
>these to all of my student robot-builders.  But, mercury switches tend
>to give you only one bit of data, so either you need a lot of them
>poised at strange angles, or you only get crude inclination data.

  Or, one contact could be resistive (carbon rods?) and the mercury could
cover the contact to different heights depending on the angle, making
a measurable changing resistance. Same idea as above, except the contact
is being resistive instead of the liquid...

-- 
 wiml@milton.acs.washington.edu       Seattle, Washington   
     (William Lewis)   |  47 41' 15" N   122 42' 58" W  
"These 2 cents will cost the net thousands upon thousands of 
dollars to send everywhere. Are you sure you want to do this?"