I'm NOT denying or disputing your comments. Your analysis may well be more accurate than mine. As an electronics engineer who "cut his teeth" designing high power (1 KW >< 10 KW) / high frequency amplifiers (2.0 MHz >< 400 MHz) for radio communications applications many decades ago, I VERY WELL understand proper grounding, spurious radiation, random noise, etc. Considering that the subject was a "K-car", built in the early 1980s, the level of sophistication of control of robotic devices was at the same level as today's technology. At this point, it doesn't make a lick what the cause was, since it is ancient history. It remains a story for entertainment at most.
I had several instances where the robot was accused of incorrect or random wrong positioning. The root causes were bad parts, inconsistent presentation tooling, human (loading) error, or a damaged end-effector / end-of-arm tooling. The robot controller and mechanical arm ALWAYS went to the correct position.
All of the servo systems that I have seen rectify the AC source to DC, and then chop it to high frequency AC. The AC supply would have to be so bad as to cause the robot controller to shut down to cause a problem. Yes, then you would have a problem; a dead robot, not a random misplaced weld.
How about one of the parts in the assembly was in error and that a chain of construction caused a weld flange to be in the wrong position? To quote an earlier post, a human welder would have just adjusted his bead.
While many of the comments are interesting & pertinent to the probable cause of this manufacturing error, COULD IT BE, given the era of robotic manufacturing, that there was a power glitch in the power line feeding the robot which caused it to make an errant motion along one of its axes? Considering the overall environment of a major assembly line, it is highly likely that the A.C. power lines were highly toxic w/ noise from multiple sources.
Many of us have experienced non-reproducible glitches occurring in systems design during our careers, I suspect this incident may be classified into this category also.
Andrew; I worked in the General Motors Scarborough Van Plant, and the Oshawa Truck Plant, and at a couple of suppliers, and I have seen some robot applications.
The Van Plant had ABB IRB 2000's using 'seam finders' to find the overlap of the metal pieces to lay the MIG weld. One of the problems was some of the parts were designed for right-side-up manual welding. The robots were trying to weld the same fit-up upside-down, which caused major problems.
Quality improves with robotic applications, because robots don't work with 'junk' parts - the parts and the fixtures must be right. Humans can (and do) compensate for poor fit-up.
It was always a problem, as a 'robot programmer', to try to educate engineers as to the correct application of robots. And many times, I had to 'defend' the robot, and prove the problem root cause was bad parts or poor fixturing.
Yes, Chuck, it was Iacocca. He first proposed the concept when he was at Ford. They said no. When he was at Chrysler, he implemented the K Cars successfully. It could have been the timing, since it was an American response to the booming Japanese cars. Iacocca's bigger success, though, came with the Caravan and Voyager minivans.
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