Subject:
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Re: Detecting tilt with an Accelerometer.
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 21 Oct 2002 19:07:48 GMT
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Viewed:
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1008 times
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In lugnet.robotics, Ralph Hempel writes:
> > A typical micromachined accelerometer WILL measure tilt of a platform that
> > is not otherwise accelerating. The value the sensor returns will be
> > g*sin(tilt angle) if the sensor is placed level on/in the platform.
>
> <sound of Ralph eating his poorly thought out words>
>
> John,
>
> You are, of course, correct. The beam is always under 1 G if it is parallel
> with the Earth's surface. In free-fall, the beam becomes "weightless" and
> the accelerometer returns 0.
>
> As you tilt the sensor, the beam deflects less and less and eventually
> there is no strain and it returns 0 as well.
Stop eating for just a sec, and help me understand this.
If a sensor (accelerometer) is parallel to the earth's surface, the reading
should be zero, right? (no acceleration due to gravity)
But, if the object holding the sensor begins to fall (ignoring the push to
start the fall), then an accelerometer placed at the center of the object's
mass will begin to rotate, and accelerate until the rotation is 90 degrees,
and the acceleration = 1g. At this point the sensor is in free fall, and
the reading would (still/again?) be zero.
Is that correct?
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Message has 2 Replies:
 | | RE: Detecting tilt with an Accelerometer.
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| (...) Steve, The accelerometer is actually a micromachined beam. Think of a miniature version of your arm holding a 5 lb brick. Your measurement axis is rotation about the shoulder joint. Whether or not you or the brick are moving, the brick is (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
| | | Re: Detecting tilt with an Accelerometer.
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| (...) No acceleration along the sensed axis, yes. (...) At this point, we need to know the type of sensor you're using (is it a pendulum type sensor, or a linear compression sensor, or gyroscopic precession sensor, or something even stranger?), and (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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Message is in Reply To:
| | RE: Detecting tilt with an Accelerometer.
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| (...) <sound of Ralph eating his poorly thought out words> John, You are, of course, correct. The beam is always under 1 G if it is parallel with the Earth's surface. In free-fall, the beam becomes "weightless" and the accelerometer returns 0. As (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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