Subject:
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Motor power levels, floats and the LCD
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Newsgroups:
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lugnet.robotics.rcx.robolab
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Date:
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Sun, 3 Oct 2004 04:11:45 GMT
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Viewed:
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8839 times
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Hi
We just started using RCX and Robolab for a university course in cognitive
systems. Our first lab was to navigate a maze using no sensors (internal
representation only). The worst problem is inconsistent results given consistent
power to the motors. So I started looking in to why this might be. This led to a
couple of questions.
1. Using the View button it is possible to view the value of an output port as
well as the input ports. Unfortunately any documentation I can find only
explains values when viewing an input port. With our motor, the view value
fluctuated between 2 and 3, even though in our program power level was often 2
but never 3, instead dropping down to 0.65 for the straight-aways. What exactly
is being reported here? Why should it be fluctuating? I’m not positive but it
seems to occur most often just after a shift in levels. Does RCX do some sort of
adaptation/ramp-up to correct for a startup loss?
2. I read that the motors vary power level by using pulse-width modulation, and
that in the hardware only 8 power levels are available. Robolab let us get away
with hooking a numeric constant to the power level of a motor command, and even
inputting float values (the 0.65 I mention in question 1). What is the RCX
doing with a fractional value? Especially a value < 1 since, as listed in the
setting started guide a 1 in Robolab corresponds to the RCX’s 1 power level.
during testing 0.4 seemed to produce a value significantly different from 1.
Any help would be much appreciated.
Dave
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