control system programming

[archiver]

Posted by Justin Stiltner.

Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.

Posted on 3/4/2000 9:15 PM MST


In Reply to: Works for us... posted by Nate Smith on 3/4/2000 8:25 PM MST:



we have the speed controller set to break but the motor still backdrives and I dont think that we will be able to tighten that screw enuff and then still raise our arm so we will still need to fabracate a breaking system for it.

Does anyone have a suggestion on how to stop a sproket?? ill give a dew to you if we use your idea and your at the mid atlantic regional..... were not attending the nationals unfortunally

also is anybody looking for extra drill,window,or seat motors and has fisher price or van door motors to trade then e-mail me!! jstiltner@buc.k12.va.us

Justin Stiltner
Team 388

[archiver]

Posted by Rick Berube.

Engineer on team #121, Rhode Warriors, from Middletown H.S..

Posted on 3/5/2000 4:33 PM MST


In Reply to: Re: Works for us... posted by Justin Stiltner on 3/4/2000 9:15 PM MST:



How about drilling a slot in your sprocket and using a servo to insert a pin. Spring load the pin so if it stikes the solid part of the sprocket, it will be a simple matter of turning the sprocket another turn or so (1/2, 1/4 turn depending upon how many slots you drill/cut) before the pin pops in. You'll need to drill/cut the slot(s) at radius along an arc to allow easy insertion of the pin (much like the main sprocket on a bicycle).
On either side of the sprocket, ensure the pin is up against an appropriate mechanical stop when the sprocket comes to rest on it. You'll need to make sure the servo is not the object handling the load and that the pin and stops are rugged enough to handle the load on them! I am also assuming that in your design you can afford a turn of your mechanism w/o it slipping too much, and that the sprocket will be slipping relatively slowly compared to the servos ability to insert the pin as teh sprocket back-turns.

My first thought was to use the solenoid from a pneumatic valve, but I don't think you are allowed to dismantle one to use it. Also I don't know what the throw on it would be, or the diameter of the pin itself. Probably too small judging by the size of the valves.

Hope this helps,

Rick

[archiver]

Posted by Joe Johnson.   [PICTURE: SAME | NEW | HELP]


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

Posted on 3/5/2000 8:16 AM MST


In Reply to: Works for us... posted by Nate Smith on 3/4/2000 8:25 PM MST:



Whether or not dynamic braking works or not is all determined by efficiency and ratio.

Unless the cable takes some goofy routings, I suppose we can say your cable is about 90% efficient.

The weight of your machine is 130 lbs. Using a 1/8 inch radius, this translates to 16 inch lbs of torque, but because of the 90% efficiency and the two motors, each motor see less than 7 inch lbs.

I can't recall the exact numbers but I have a vague recallection that it takes about 1 Newton-meter to backdrive those motors (without dynamic braking). 9 inch-lbs is about 1 Newton-meter.

SO... As you can see, your machine was right on the ragged edge of backdriving without dynamic braking. Dynamic braking provide extra bit you needed to keep from falling off the hill.

If on the other hand, your machine put 14 inch pounds of torque on those Delphi Power Sliding Door Mechanism, all the dynamic braking in the world was not going to keep you from falling.

Joe J.

P.S. I almost hate to share this with folks at this moment, but I was withing a eyelash of getting two electro-mechanical brakes donated to the kit in 2000 (at the time I had no indication that hanging would be part of the game, I just thought it would be a cool addition to the kit). Only a freakishly unluck chain of events managed to prevent it from happening. Ah well, better luck next year. I am also hoping to get some electro-mechanical clutches donated as well -- give me time....