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macg

PF755 Cip Motion

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I have just been handed a horrible task. I am to program a control logix processor for 5 PF755's such that 5 hoists raise and lower together. The hook height can not vary more than 1" between all five as they are moving. For most lifts, all of the hooks are at the same level. For some lifts the hooks will be at different levels but must move maintaining the shape. Two types of motions are required. One motion is operator jog. The second is an automatic lift or lower to a predetermined location. Any suggestions other than just saying CIP motion????

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I don't know if you really need motion to implement this kind of application. Five identical hoists controlled by five identical and identically tuned PF755s controlling motors with highly accurate identical encoders could easily return results within the project's requirements; the "timing" of the hoists could be "supervised" by a quality CPU. Yes, you could implement a virtual motion axis and then "gear" the hoists' axii to the Master one, however, we are talking 1.000" movement precision; motion might be an "overkill" in my opinion when the tolerances are this large.

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My guess is that somebody specified the PowerFlex 755 for this application because of the Torque Proving feature; the 755 is what RA's internal crane and hoist systems group uses. If you're not familiar with torque proving or the 755 in general, I think a multi-axis synchronized crane system might be something you want help from experts on.

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+1 to Ken for suggesting a crane expert {which I am not}, but I can tell you if you do this yourself be sure and read OSHA 1910.179 - {Occupational Safety and Health Standards ; Materials Handling and Storage ; Overhead and gantry cranes.} and ANSI B30 - {Construction package} as relates to hoists and cranes. The regs on these have changed a lot from the days when you just hung block and tackle and went to work.

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