Quote:
Originally Posted by Trevor_Decker
So if I wanted to use an accelerometer to tell how fast a robot is moving (constantly adding/ subtracting the acceleration from the speed) , I would want a 2g accelerometer since the field is 54 feet in length, which divided by 32.174(earths gravity) = 1.678 which rounds up to 2.
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Time for some dimensional analysis: 54 ft ÷ 32.174 ft/s
2 = 1.678 s
2. Since
g is not given in s
2 (seconds squared), you probably shouldn't rely on that calculation.
Constant acceleration of 2
g means that for every second the robot moves, its velocity increases by 2 × 9.81 m/s = 19.62 m/s = 64.35 ft/s. I can't think of any FIRST robot that can sustain that sort of acceleration for any meaningful length of time. (So it turns out that that might be sufficient for measuring your robot's acceleration due to its own drivetrain, but for different reasons than you suggested.)
How fast is your robot, and approximately how long does it take before it reaches its top speed? That will help you find your
average acceleration. You'll want a sensor that can handle that range for sure, but like Chris said, if you're depending on this sensor to measure anything but the idealized performance of your drivetrain—for instance, stopping due to hitting things on the field—you'll need to expand the range by some unknown amount.
Quote:
Originally Posted by Trevor_Decker
How accurate is a 2g accelerometer?
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The accuracy of the device itself will be published on its datasheet, provided by the manufacturer (or sometimes the distributor of the part). It's usually a function of the device's temperature, so many incorporate a temperature sensor.