Has anybody done any hyraulic position control using plc's? I have a VIPA (like S7-300) plc with +-10V (+-27648 in PLC) outputs driving hydraulic proportional valves, (+10V give full speed extend, -10V full speed retract). Feedback is 0-10V over full cylinder stroke giving INT 0-27648 in the PLC. Control is very simple; output is 2*(Command-(Feedback-13824)). Command is plc generated ramp for test purposes.
This works OK, I think I will not need any I or D control, the cylinder goes where it's told to when it's told to.
Problem is vibrations at some parts of the stroke but only when moving. Any stationary position is fine so I don't think it's a noise problem. I put software filters on the inputs and it doesn't help.
Scan time of PLC is about 3-4 mSec, not sure if this is fast enough for hydr servo??
Any ideas?
This works OK, I think I will not need any I or D control, the cylinder goes where it's told to when it's told to.
Problem is vibrations at some parts of the stroke but only when moving. Any stationary position is fine so I don't think it's a noise problem. I put software filters on the inputs and it doesn't help.
Scan time of PLC is about 3-4 mSec, not sure if this is fast enough for hydr servo??
Any ideas?