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Andrea Ascani

Axis with inverter and encoder

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Hi, I have to implement an axis control in a NX1P2 PLC using an inverter (3G3MX2) and an encoder cabled on a EC0122 board. I found something similar implemented  on a CJ2M PLC, but I have no idea how to set up the axis in the configuration of sysmac studio and how to implement the control.

Can someone help me? Some sample to catch out the configuration?

 

Thanks a lot

Andrea

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I don't think the NX1P2 has that capability. You would need a PLC with full motion control functionality. I could be mistaken though. Someone smarter than me might know of a way to pull that off.

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A VFD does not get set up as a motion axis, so you don't need a full motion controller.  Only servos and steppers are motion output axes.  You would not be able to use any of the motion control function blocks to control a VFD, at least not that I am aware of. 

What exactly are you trying to do?  Control speed and verify position with an encoder?  How is the VFD being controlled?  You should be able to do some calculations with the encoder speed to determine how fast and how far the motor is moving.

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Yes, the idea is to adjust frequency output of the VFD according to the position of the encoder. The axis I would like to control in this way is just a positioning Axis, with not high requests on precision. 

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VFDs are good and speed control but not positioning. for position control (servo like) control feedback loop need to be closed at some device that can act fast. if the positional accuracy is not that important you can use programmable controller to make own code to run it at desired speed, decelerate before target position then creep slowly until at position or reasonably close. Also the whole idea of position control is to be able to maintain the reached position. and without feedback loop closed at the drive itself or at least brake, this is not likely to produce satisfactory results. When VFDs use encoder it is usually to maintain speed or to track another drive - not to do positioning. Some VFDs (for example from Eurodrive) have option to wire encoder directly to the VFDs, use internal loop control. They can be programmed to move among few predefined positions which is handy for applications like turn table etc. but this is rare. really this is domain of servos.

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4 hours ago, panic mode said:

They can be programmed to move among few predefined positions which is handy for applications like turn table etc. but this is rare.

Not really that rare any more.  Rockwell's mid-range PF525 has low-bandwidth positioning built in, with a variety of operations possible.  With a network connection, presets can be rewritten on the fly for unlimited unique steps.  It can even drive permanent magnet motors.

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