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Originally Posted by Jeff G
I've seen many talking about using gyro's in the control system. Last year we only used banner sensors for counting distance and dead reckoning for autonomous. Some questions come to mind:
- Is there enough sensitivity to use these for drift? Can the signal be integrated to provide actual position.
- Which gyro's would be the best to use for this purpose?
- Can all this be done with just the FRC, or do some teams use auxiliary IC's?
We were happy last year just to get the new system going and would like to improve our controls.
TIA - Jeff
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As far as I know, the best/"only ones allowed" gyros are the Analog Devices ones, ADXRS150 and ADXRS300. (I just checked Analog's website and apparently they have a new 75°/sec model, let's see if any official supplier stocks them.)
As the model name implies, they are capable of 150°/sec and 300°/sec, and as some people found out by the datasheet, resolution can be improved by a factor of 4 with a simple resistor network.
So, to answer your first question, they're pretty sensitive - 150 and 300 degrees per second equals 25 and 50 RPM, respectively, and that's pretty fast for a 'bot to turn (check team 419's 2001 robot, that thing spun fast!). If your robot is hit, it may "turn" a bit faster than that, and you may lose track - take that into account.
It's accuracy is good enough for the 15 seconds of autonomous operation. A simple integration of the angular rate will give you angular position - we tried using rectangular infinitesimal elements and achieved moderately accurate results, some teams reported using trapezoidal integration with better accuracy. Also, don't forget to sample the signal at twice it's frequency to avoid aliasing.
The answer to your third question is yes and yes. Some teams used only the Robot Controller, others turned to a separate processor. It will depend on how much processing power you need, but if you're only integrating the gyros and calling relatively slow interrupts, you should be OK with the RC.
Whoah, long post... Hope I didn't sound too confuse.
