Thursday, November 18, 2010

PLC Hybrids in Motion





Motion control coupled with analog and/or discrete control is one of the main applications for hybrid controllers. Two primary types of products compete in this market space: PLCs with motion capabilities and discrete and analog I/O and logic.

PLCs with motion control plug in or add on board would be seem to be the best of both worlds, but this is not always the case. For instance that is PVA which makes multi axis robotic dispensing equipment. Before settling on the hybrid control, they relied on a combination of motion controllers and PLC to accomplish machine functionality. The PLC worked well for I/O control, but PVA ran into problem trying to integrate motion with the PLC. Open loop motion was easy when accuracy was not important. Close loop motion was much more headache. PVA also tried using motion modules attached to the PLC and modules of stand alone. With modules attached to the PLC, trying to debug and determine why the motors weren’t moving or why errors lights up were not as easy or apparent as it should have been. Trying to troubleshot problems in the shop or out in the field was difficult.

Some modules that were not PLC based had communication problems with PLC compounding PVA’s control issues. Proprietary communication protocols were an obvious problem, and standard protocols always seemed to have some kind of twist. Often, there was a communication problem, either written into the software or with keeping the motion controller or PLC synched together. To eliminate this problem, PVA selected a hybrid controller from Galil that features up to eight axes of motion control, eight analog inputs and 64 points of digital I/O.

PVA’s 5000 line of machine offer customers a wide functional range and can manage a dispense variety and apply operations/motion control, material curing via a control heat process (analog control) and circuit board trafficking through the work area (discrete control).


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