True indeed. I wasnt aware he was not "there" yet.
Gunner
One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch
Oh..Im only familiar with AMC drive models NC-4/NC-5/NC-7 and NC-9
They went to other drives later in production.
Ive got a stack of unknown condition drives, AMC, Copely and Glentek sitting out on the shelf..if anyone wants to putter around with SMD circuit boards....
Gunner
One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch
"Off" is a slippery concept. It sounds like you have a very slight leakage current somewhere. It could be anything; one never eliminates them all. I would short the input out and see what the creep rate becomes. It won't be zero unless you are under closed-loop control. Nor is 8"/hour all that bad for open loop.
Joe Gwinn
Normally I have my controller controlling before powering the servo drives. Sounds like your amps are normal but you probably need the control on before the amps and the amps off before turning the control off.
Rogern
this behavior would be typical of a servo system with rate feedback only and no position feedback
Creeps are sometimes hard to get rid of. I filter them out but they creep back in.
The creeping of your drive is normal. You could fine tune the offset control with the input ref. signal shorted out but I would not bother until you get the whole control set up.
A servo system is just like your own body which is a bunch of servo systems. For instance when you drive a car down the road you automatically steer the car in the right direction. You have in fact a closed servo system consisting of your eyes,your brain, your arms, the steering system of the car and the wheels. Your eyes are the position sensor just like an encoder. IF you shut your eyes the loop now become open you could go down the road for a while without getting too far off track (if your wife is in the car and starts screaming that is equivalent to an out of position error which shuts down everything with an e stop) but eventually you would drift or creep off the road either left or right. Closing your eyes is like having only the servo operating without having the control connected. When I was young and foolish I would drive for miles with my eyes shut and have my buddy tell me which way to turn, still a closed loop system but with two peoples brains.
John
On Jul 10, 10:45=A0am, Ignoramus30064
As other have said, don't sweat it. It sounds as if you have a PID servo loop. P stand for Proportional, I is for Integrating, and D is for Differential. You have a very small error likely caused by a little leakage. The integrating part of the look is integrating the very error small signal and causing the creep. With the servo loop closed, you could see some offset, but I expect it will be too small to measure.
Dan
You need the controller to feed correction signals as the encoder indicates the need. This means the "no input signal" situation should not in use exist.
What happens when you enable the "motion inhibit" inputs?
The will probably tell you that until you are connected to the controller, you can't get truly stationary behavior.
Good Luck, DoN.
Ayup.
Gunner
One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch
[ ... ]
I don't think so. The gain (and tach feedback gain) is used to set the max speed for 10V DC input to the amp'd control terminals. And some is used to control overshoot when getting step motion controls.
The input pins being open (switch off) can allow a bit of leakage in other parts of the amplifier circuit. Try setting the input shorted -- but I suspect that you won't be able to find a truly no creep position of the offset pot even with the input shorted. At least, not one which will remain so through changes in room temperature.
It really *needs* the computer monitoring the motion via the encoder, and outputting signals to move back to where it belongs at need. So once you have a complete system, this should not be a problem.
And when the computer is turned off -- you want the inhibit to be true, which *should* keep it from moving at all.
And of course, normally, when the computer is turned off for any length of time -- the power to the rest of the lathe should be turned off too.
Good Luck, DoN.
Don't bother, this is normal. It is an analog circuit, there are always slight offsets, and they change over time/temperature. If I cared, I'd have to retune my system when the seasons change, but it is of no consequence. Once the positioning loop is closed by the encoder/PPMC/ EMC2, it will not drift like this. (In EMC2, you can hit F1, but if you don't hit F2 to turn on the positioning loop, you get in this same mode. You can use it to set the velocity offset pot, but don't worry about getting it "just perfect".
Jon
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