Slavko Kocjancic wrote:
2010/4/20 Cliff Blackburn <cblackb...@powertechrepairs.com
<mailto:cblackb...@powertechrepairs.com>>
The only thing this would really change is stopping the gantry
from skewing it's self any worse while homing. What would happen
with homing right now if one of your home switches wasn't working?
One joint would stop and the other would keep on going until you
jam it or break/bend something, neither of which are a good way to
fail.
Aeroplane ignition sistem has two magnetos. And have two spark plug in
cylinder. The pilot should test it before flight. IE starting engine
and engage just left magneto and listen if engine work right. Then
switch to the right magneto and again listen if engine sound right.
Then engage BOTH magnetos and do flight.
So if you afraid to have problem with home switch then instal another
one as a fail safe. aniway somewhere real close the limit switch is.
That big gantry I describe work more than 10 years and is placed
outside. (just roof above machine) and works near every day at least
few hour.
And YES I need to replace home switches twice as contact are coroded.
and nothing bad happens as limit switch is just two milimeters behind
home.
Btw steppers (in most cases) doesn't have enought power to destroy
gantry. So just proper design gantry to not derail in such condition.
Slavko.
p.s.
I talking to STEPPER system not SERVO.
I guess the point of doing this is a gantry has linked joints. Under no
circumstance should one joint do one thing while the other does
something else. Sure you can alleviate the issue with multiple homes,
close limit switches and motor overloads.. but should it even be
capable? Your right steppers would probably just sit there and not hurt
anything. But with big gantry's your going to use some nice size servos
which are more than capable of damage before overload.
I think your right.. there is no point adding this to the basic home
procedure it's just adding extra code most machines don't need.
I think a better approach to the problem would be to allow custom homing
procedures for every kinematics module. This is not the only style of
machine which might have a constraint.
Every kinematics module is going to know what it can and can't do with
it's joints while homing. If the module doesn't export one just use the
default and no one knows the better.
At least this is going to take into account any other robot styles as well.
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