Subject:
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Re: Servo control using Miniboard slaved
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 21 Jul 1997 22:06:00 GMT
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Original-From:
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Lipsett, Mike <lipsett.mike@syncrude=nospam=.com>
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Viewed:
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1165 times
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Chuck:
I agree with you; what I've done with the MiniSSC is to break the path into
a set of linear segments with via points in joint space. The lynxmotion arm
ends up needing a lot of points (therefore moving pretty slowly) to avoid
jerkiness, but since I'm emulating a big hydraulic excavator in a 1:50 scale
diorama, the effect hasn't been a problem.
Tom Dickens wrote a really good article on SPI comm for slaving HC11s. Some
folks on the list might want to check it out at
http://home1.gte.net/tdickens/68HC11/robocat/robotcat.html
Cheers,
- Mike
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From: cmcmanis
To: Duncan Orthner
Cc: John Hatton; 'Handyboard Mailing List'
Subject: Re: Servo control using Miniboard slaved
Date: Monday, July 21, 1997 2:14PM
Using the Miniboard as a servo slave is a good idea, perhaps
even easier is to use a BOTBoard since the BOTBoard doesn't
have any motor drivers hooked up to it (no PCB modification
required.)
Using the MiniSSC is "ok" but for controlling multiple,
co-ordinated servos it sucks. The problem is that for
things like arms (I've got a Lynxmotion arm) where there
are 6 servos, it takes on the order of 120 mS to send a
positioning command to all six servos (12 characters at
9600 baud) If you want to do path planning (that is moving
the servos synchronously to cause the end effector to traverse
a certain path) it is impossible to do at a reasonable speed.
(you can break the path into line segments, but the servos
all slew at their highest rate so you end up with really
short segments, and thus it can take you 15 - 20 seconds to
traverse a path that the servos are capable of traversing
in just a few seconds.)
That being said, you can compensate for such things on the
Miniboard/BOTBoard by programming the 68HC11 to take them
into account. (and you do have the built in SPI-port of
course.)
--Chuck McManis
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