EXACT POSITIONING OF SERVO MOTOR

[aakash 0]

HI I AM NEW TO MITSUBISHI PLC,I HAVE SYSTEM IN WHICH SERVO MOTOR( MR-J3 SERIES ) IS USED TO MOVE WORKPIECEFROM ONE PLACE TO OTHER BUT I CANNOT UNDERSTAND HOW SERVO IS TELLING ITS EXACT POSITION TO PLC (I KNOW THEY HAVE ENCODER TO GIVE FEEDBACK BUT HOW ENCODER IS TELLING ITS EXACT POSITION TO PLC)

[Luke.S 8]

There will be a Current Feed Value and Machine Feed Value in the axis monitor data of the motion controller (assuming you are using Q or iQ series here). These can be accessed via buffer memory - look up the address in the motion controller applied manual.

These values tell you how many degrees, mm etc. your axis has moved in the current positioning operation and overall respectively. How this is interpreted would depend on what control method you are using and whether it's absolute or incremental.

It may also be possible to get the cumulative feedback pulses data via buffer memory too if you look it up in the manual.

Or you could get the raw encoder pulses the old fashioned way from the LA, LAR, LB, LBR terminals of the servo drive. But that requires an expensive high speed counter card capable of receiving line driver output. You may also need to change some parameters in the drive to do this.

Btw, the servo motor does not communicate directly with the PLC. It feeds back to and is controlled by the drive/amp which is connected to the PLC. PLCs generally are not fast enough nor have the DSP capabilities to keep up with a high precision servo motor.

Edited 6 Jun 2016 by Luke.S

[aakash 0]

There is MOTION CONTROLLER ,to check all these CFV AND MFV do i need  any software .If not then can u tell me how to check the motion of my servos and the soft limits given to my servos

[Luke.S 8]

What model of PLC and motion controller are you using?

[aakash 0]

PLC NO. IS Q04UDEHCPU AND MOTION CPU Q173D CPU

[Luke.S 8]

The "feed current value," "real current value" and "deviation counter value" are probably stored in d0 to d5 + 20n. Where n is the number of the axis -1.

(3 32bit values in 6 registers)

But I don't know enough about the setup you are using. You need to read through the manuals for your motion controller and look at how it's been configured in the PLC program.

[aakash 0]

Thanks i will try tht