Subject:
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Re: LONG!!! - RCX Radarbots and distance measurement
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 8 Feb 1999 16:07:36 GMT
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Original-From:
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John Cooper <robots@jpsc.AVOIDSPAMco.uk>
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Reply-To:
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robots@jpsc.coNOSPAM.uk
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Viewed:
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1276 times
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This is the best yet!
I have taken the liberty of converting it to NQC and removing the motor
control commands. This gives a task that publishes DEFCON and AVG_AMBIENT
that can be used in a monitor loop. This is so sensitive that DEFCON 1
is pretty much unusable as it may be triggered by tufts in the carpet.
I slow down on DEFCON 2, change direction slightly on DEFCON 3 and take major
avoiding action (back up) on DEFCON 4 and above.
/*
The basic strategy is to measure DEFCON. Converted from code by Mark R. David
(markdavid@mediaone.net)
The variables used are:
AVG_AMBIENT - Maintains the initial ambient light value, and a moving
average of same
DEFCON - The higher DEFCON gets, the closer we are to the object.
DiffRaw - The difference - a number that represents how much brighter
the raw reading has to be to raise DEFCON one level.
ThisRaw - the latest light sensor raw reading
MinRaw - The current effective minimum (brightest) raw reading
RisingMins - Flag that indicates that our most recent minimum was
actually higher (darker) than the currently effective minimum. We might
no longer be getting closer to the object, but we'll give it one more
chance.
LastRaw - the reading prior to ThisRaw, used to determine if things are
getting brighter or darker
DescendingRaw - a flag that readings are currently descending (getting
brighter)
*/
#define RAW_LIGHT IN_2
#define FALSE 0
#define TRUE 1
#define SAMPLE_COUNT 30
int AVG_AMBIENT,DiffRaw,ThisRaw,DEFCON,MinRaw,RisingMins,LastRaw,DescendingRaw;
int Temp; // temporary variable
task ProximityDriver
{
Sensor(RAW_LIGHT, IN_CFG(STYPE_LIGHT, SMODE_RAW));
IRMode(IR_HI);
Temp = 0;
repeat (SAMPLE_COUNT) {
ThisRaw = RAW_LIGHT;
Temp += ThisRaw;
}
Temp /= SAMPLE_COUNT;
AVG_AMBIENT = Temp; // average starting ambient light value
DEFCON = 0; // DEFCON - number of diffs the last min is below ambient
MinRaw = AVG_AMBIENT; // The current minimum flash read - init to ambient
RisingMins = FALSE; // Flag that the last min was higher than the one before
LastRaw = AVG_AMBIENT; // Previous raw reading
DescendingRaw = FALSE; // Flag that raw readings are descending
while (true) { // monitor forever
ThisRaw = RAW_LIGHT; // Take ambient reading ...
Temp = AVG_AMBIENT;
Temp *= 4;
Temp += ThisRaw;
Temp /= 5;
AVG_AMBIENT = Temp; // ... and keep a moving avg of it
DiffRaw = 615;
DiffRaw -= AVG_AMBIENT;
DiffRaw /= 6; // DiffRaw = The diff - a meaningful difference in light reading
if (DiffRaw > -6) { // Is negative and no greater than -5
DiffRaw = -6; // DiffRaw = Min(-6, (615 - AVG_AMBIENT) / 6)
}
SendMessage(255); // Flash
Sleep(3);
ThisRaw = RAW_LIGHT;
if (ThisRaw < MinRaw) { // New minimum!
MinRaw = ThisRaw; // Reset the effective min
RisingMins = FALSE; // Clear the rising mins flag
DescendingRaw = TRUE; // Set the descending flag
Temp = MinRaw;
Temp -= AVG_AMBIENT;
Temp /= DiffRaw; // Calculate DEFCON
DEFCON = Temp; // DEFCON = (MinRaw - AVG_AMBIENT) / DiffRaw
} else {
if (ThisRaw > LastRaw) { // Ascending
if (DescendingRaw==TRUE) { // Was descending must be a higher min
if (RisingMins==TRUE) { // It's the second one! Reset the effective min
MinRaw = LastRaw; // Reset the effective min
Temp = MinRaw;
Temp -= AVG_AMBIENT;
Temp /= DiffRaw; // Calculate DEFCON
DEFCON = Temp;
} else {
RisingMins = TRUE;
}
}
DescendingRaw = FALSE;
} else {
DescendingRaw = TRUE; // Descending
}
}
LastRaw = ThisRaw;
} //loop forever
}
--
John & James Cooper, Wallington, UK
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message is in Reply To:
 | | LONG!!! - RCX Radarbots and distance measurement
|
| RCX Radarbots and distance measurement While I like the idea of a radarbot, most of the algorithms I've seen for implementing it were basically "You're close when the return signal starts to get really noisy." I wanted to know more about what was (...) (26 years ago, 5-Feb-99, to lugnet.robotics)
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