Subject:
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Encoder Implemenation questions
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 11 Jan 2001 15:43:41 GMT
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Viewed:
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1066 times
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I have contructed a robot that I want to be able to move and position itself
accurately.
I have encoders (the Hamamatsu P5587) attached to analog inputs 4 & 5
using sencdr4 & 5. I have 24 segment encoders that should give me a
resolution of about .33". Not super accurate probably but close enough
for my purposes.
I am using 2 standard servos that have been gutted into simple gear motors.
With this configuration I am able to accurately count ticks from the wheels.
My question is: how can I accurately get a wheel to stop after any number of
ticks? I coded a routine to count up to 24 and stop. Its obvious from watching
the wheel that once it turns off it continues to rotate about 3 to 5 more ticks
which is over 1"! Not good.
I have been able to get it to stop exactly at 24 ticks by turning off the motor
and reversing it for 50 Msecs which has worked for me but seems like a kludge
solution to the problem. Is there any way to short the motor or do something to
get a precision stop? Something more elegant than my method :)
Thanks in advance for any help on the matter.
-Jim Munro
<jimmn@xnet.com>
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Message has 2 Replies:
 | | Re: Encoder Implemenation questions
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| You step into the morass that separates reality from theory :-) The "right" way to do this is to measure the current on the servos, ramp their accelleration up and then down again as you approach your final endpoint. Read up on feedback systems and (...) (24 years ago, 11-Jan-01, to lugnet.robotics.handyboard)
| | | Re: Encoder Implemenation questions
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| (...) I would suggest shutting it down early (say 5 ticks early) and using a "jog" mode whereby brief pulses are sent to the motor to move it the remaining distance. Lets say you shut it off at 19 (targeting 24) and the motor/load's momentum carries (...) (24 years ago, 12-Jan-01, to lugnet.robotics.handyboard)
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