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I've had discussions lately with a VERY large number of people about using an accelerometer to detect if an object (like a LegWay) is tilting. I'd like to continue the discussion here, with anyone willing to talk about it. Let me start by saying, (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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(...) It might work, but imho not the obvious way. How it won't work: Measure the acceleration sideways. You would measure an acceleration if you were holding the whole setup at a certain angle, but since the whole sensor including the mechanic (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | RE: Detecting tilt with an Accelerometer.
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(...) Let me chime in and say "It won't work" Tilt detection is almost always done using a simple inclinometer. This is just a weighted pendulum on a potentiometer or shaft encoder. Now, that being said, could figure out that an object is rotating (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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(...) Do you have some concrete reasons why it won't work, to go along with your assertion (for those of us just now joining the conversation)? I suspect that it could be made to work (in conjunction with other data like what the motor output is, (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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Hi again, (...) Ok, i have just discussed this with someone having a ph.d. in physics and that's what he told me: Think of the segway as some big chimney you want to blast. These things break into two pieces while falling sideways. This is because (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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(...) it. (...) Umm... that is a type of accelerometer, unless there's a terminology difference that I'm not aware of. (Consider what happens to the sensor when pushed sideways (not on axis) without rotation... you get transient swings representing (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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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. If the platform is accelerating, the (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | 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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| | Re: Detecting tilt with an Accelerometer.
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(...) I think I figured this out, right before I read this. I'm not sure if this is what you're saying, but if I put the sensor on the bottom, under the axle, then it will spin opposite the direction the LegWay is falling. So, it could actually (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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(...) 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 (...) (22 years ago, 21-Oct-02, to lugnet.robotics)
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| | 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)
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| | 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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| | Re: Detecting tilt with an Accelerometer.
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(...) Alex, I think that you would only require two accelerometers, one positioned low near the wheels, the other near the top. Both should be oriented to measure accelerations along the direction of travel. Using two accelerometers gives you a (...) (22 years ago, 22-Oct-02, to lugnet.robotics)
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| | Re: Detecting tilt with an Accelerometer.
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(...) Yes, this would be a simpler solution. Using the difference and the sum of the two accelerometers as two inputs would likely make the driver logic very neat and clean. In addition, it could be useful to have two (much more sensitive) (...) (22 years ago, 22-Oct-02, to lugnet.robotics)
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