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Posted by Nate Smith.

Other on team #66, GM Powertrain/Willow Run HS, from Eastern Michigan University and GM Powertrain.

Posted on 2/22/2000 2:59 PM MST


In Reply to: Re: BACKDRIVE PLEASE HELP!!!!! posted by Patrick on 2/22/2000 1:22 PM MST:



: : It actually can be done without code if you are using the speed controllers to control the motors you want to keep from backdriving. Just set the jumper on the speed controller(right under where the PWM cable plugs in) so that it is on the left two pins. This will put the speed controllers into dynamic braking mode, which will keep the motors from backdriving under weights equal to that of a robot. We almost thought our winch lift was in trouble last night, until I remembered that you could do this...

: : Nate

: Nate, it turns out that our speed controllers had already been put into that mode and it sill backdrives. We have a 93 pound robot. CAN ANYONE PLEEEEASE HELP?

If it's the drill motors, it might be caused by the clutches in the gearboxes, and there's not much you can do about that...otherwise, put a routine in your control program similar to this(simulating the dynamic breaking, but at a slower cycle(roughly 40Hz v 60Hz on the speed controllers):
PS - I know my formatting isn't the best, and there's probably a better way to do this in PBASIC, but this should work...

if p1_x .gt..lt. 127 then skipbraking
if pwmout = 126 then go_high
pwmout=126
goto skipbraking
go_high:
pwmout=128

skipbraking:

--------
Notes:
.gt. = Greater Than Symbol
.lt. = Less than Symbol
pwmout = VAR byte output to the desired speed
controller
p1_x = Desired joystick axis to be monitored