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Thread: PC based robot control?
11-20-2011, 08:36 AM #1
PC based robot control?
My company is getting rid of an older Fanuc welding robot. I operated it a little, a long time ago, and could teach points but that was the extent of my experience with it. The arm is sound, but the control "had smoke coming out of it the day they took it down and it would barely weld."
I could buy it for a price low enough to just play with, on my own, to learn more about robotics and test some automation ideas myself, but I'm curious if I can move to a newer/cheaper/easier/non-fanuc control? Am I right in my thinking that the robot is just servos and encoders, and telling it where to go and when to go there, should be relatively simple to retrofit?
11-20-2011, 09:11 AM #2
The question you have to answer is where the smoke came from. If the servo drives are toast then you could be looking at serious cash or lots of scrounging to get the motors turning again.
The control part is easy as there are several PC based CNC/robotics programs, many of which are free and open source. The best of these is emc2 but it runs under linux.
Implementing linux and emc2 depends on your aptitude for programming. The pre-configured setups are easy. None exist for a welding robot that I am aware of.
Mesa Electronics, Pico Systems, and others sell boards that should directly interface with the Fanuc servos and various control circuitry.
All the cheap or free windows/DOS software is intended for step motors. The workarounds for servos defeat the purpose of having servos and will cost more than the Mesa cards.
11-20-2011, 11:56 AM #3
of all industrial level machine tools, the multi-axis robot has the poorest resale/residual
value . i have owned a good dozen, made money on maybe two of these. parting them is usually what happens. now if you find the rare "P" series Fanuc, working, you've got something.
we have experience in retrofits up to 8 axis. but retrofit software for multi-axis robots is mostly high end european. or Fanuc. entry level $40K. add another $20K for install.
eventually game control software (x-box, playstation) will be adapted to robot retrofits. integrating encoder feedback, from 8 servos all in motion, will be a trick though. many US based robot retrofitters have folded.
11-20-2011, 04:31 PM #4
On an RJ2 control, the drivers do not have any commutation logic in them. They get six inputs for the three phase H-Bridges for each of the individual axes.
The computer boards have the encoder inputs, and do all the commutation calculations, along with motion and trajectory calculations.
If you are a super software guru, and dedicate yourself to software Development, not software re-purposing, then, just maybe you could do it, once you became a hardware guru, and designed the commutation circuitry, and encoder counters and interfaces.
Or you could cruise ebay, and find some new/used boards for the control, and THEN ASSUMING you could dig the software intact out of the dead control, you could boot it up.
Otherwise plan on spending MORE than the robot is worth, to "license" the software in the robot from Fanuc. You need to "license" the software before they will answer ANY questions about it. They will not even sell you parts, or look up part numbers, or verify any part numbers.. Nothing. Even if the previous owner was properly "Licensed", once the robot changes hands, you need to pay Fanuc again, every time the robot changes hands.
This is how it was explained to me, anyway, by Fanuc.
11-20-2011, 05:30 PM #5
You're not going to find a CHEAP PC based solution to running a Fanuc robot. It's not even worth trying, you can buy an ArcMate with a welding power supply delivered for under $7k if you watch Ebay. I've got 3 of them this way, and they all work just fine. You couldn't even to begin to interface 1 for that price. If I were you I'd fix the existing control, or part it out and go buy another used working system.
11-21-2011, 11:22 AM #6
11-21-2011, 05:47 PM #7
Actally - emc could do this also.. One of the developers has created a bldc component that will pretty much do anything... (right down to controlling h-bridges directly)
there have been a few people using them now..
As far as the arm itself. Emc2 does have serial kins that works with serial stacked arms. You give it arm lengths and offsets and it does the joint to world conversion. Not for the faint of heart but quite a few people have been using it.
11-21-2011, 07:20 PM #8
11-21-2011, 09:06 PM #9
11-21-2011, 11:04 PM #10
There is the Orocos project.
The Orocos Project | Smarter control in robotics & automation!
It would be a good starting off point for Post-Graduate research in Mecatronix.
Its built upon a hard-realtime kernel, a requirement for robotics that a PC does not fulfill.
11-22-2011, 10:30 AM #11
11-22-2011, 10:42 AM #12
11-22-2011, 10:51 AM #13
11-24-2011, 07:48 AM #14
The 'not-real-time' argument didn't exist prior to the widespread acceptance of NT and its descendants. Suddenly, the X86 interrupt architecture was found to be wholly inadequate for real time control applications.
Fortunately, nobody has informed the bumblebee that it is mathematically impossible for him to fly.