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[DPRG] Processing unit for mobile robot
Subject: [DPRG] Processing unit for mobile robot
From: Randy M. Dumse
rmd at newmicros.com
Date: Fri Apr 25 10:05:21 CDT 2008
John Swindle said: Thursday, April 24, 2008 10:08 AM
> The notable exception is the LabVIEW FPGA that can be
> embedded in the backplane of industrial controllers to give
> microsecond resolution and loop rates that are closer to
> that. Way beyond hobbyist prices.
And yet I just heard on the Seattle list FIRST has chosen the
LabVIEW Compact RIO for their microcontroller for 2009. That has
a 400MHz processor and an FPGA in it. And I have to wonder how
the kid's teams will afford those things.
> When jitter seems to be a
> problem, is it possible to ask what time it is and write code
> that uses the actual delta time since the last iteration,
I wonder. I've been thinking on PID and what doubling or halving
the periods would do to the gains, and I can't see the answer is
linear. Roughly doubling the I term update rate would halve the
gain (to totalize the right number to get the same output ).
While the D-term gain would need to be doubled. But the P term
gain while somewhat near the same value, would need to be turned
down, but i would not at all be a linear change. So a PID
routine with an unstable update period is not something I could
say made obvious sense.
Randy
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