AB Kinetix 6000 losing postion after power cycle

woodj313 · Jan 13, 2012

Last week I had to replace a Kinetix 6000 drive and motor.

Drive: 2094-BC01-MP5
Motor: MPL-B320-M
PLC: 1756-L61

Prior to the replacement the servo would retain its postion after the power was cycled. Now whenever the power is cycled the system comes up thinking that it is in some other position than when it was powered down.

Does anyone have any ideas as to what may be causing this, or if maybe I missed something when replacing everything?

Thanks

iant · Jan 13, 2012

just a thought
the PLC knew where the home position of the old drive was.
Have you 'Homed the drive'
both by the drive itself first and by then the PLC.
there may be the need to reset the PLC home to match the drive home positions.

MichaelG · Jan 13, 2012

This looks like an Absolute homing issue

Simply - I suspect that you are using MAH (Active or passive) or using MRP (Motion Redefine Position) to get the axis in the correct position.
This does not change the power cycle position.

DO the Following to set the power up position

Change the axis homing method MAH to Absolute (Axis Properties) - Temporary - change back previous setting when finished
Set the "Position" value to the current position the servo is located (I use Axis.Actualposition once I have set up the position correctly)
Use the following Motion Direct commands
- MAS - Motion Axis Stop - servo loop must be Open
- MAH Motion Axis Home

Details - In the Motor encoder a zero offset is stored, When the Servo Powers up it reads that value to work out the application zero position - The ONLY way to change that value is to use an absolute MAH with the servo loop open
Whenever the mechanical drive change is disconnected, this process may have to be performed (eg Gear box change or motor change)

Please tell us how this works for you

iant · Jan 13, 2012

thanks MichaelG - thought that was needed, but haven't set one up before.
- thats what I was hinting at

chavak · Jan 14, 2012

Thanks MichaelG for the info. I will try this out when I need to use it next time.

What I was doing until now was -

1. Move the .ActualPosition value to a Real Tag when ever the positioning is completed.
2. Upon power up and for the first scan of the ".DriveEnable Status" load this stored value to the Actual position of the servo, using MRP command.

And of course this was done on the servo axis which was not able move upon power down, due to brake or the gear box itself.

Regards
_______

woodj313 · Jan 16, 2012

Thanks guys, I will try to do this today when there is availabilty on the machine to do so.

woodj313 · Jan 17, 2012

MichaelG said:
This looks like an Absolute homing issue

Simply - I suspect that you are using MAH (Active or passive) or using MRP (Motion Redefine Position) to get the axis in the correct position.
This does not change the power cycle position.

DO the Following to set the power up position

Change the axis homing method MAH to Absolute (Axis Properties) - Temporary - change back previous setting when finished

Set the "Position" value to the current position the servo is located (I use Axis.Actualposition once I have set up the position correctly)

Use the following Motion Direct commands

MAS - Motion Axis Stop - servo loop must be Open

MAH Motion Axis Home

Details - In the Motor encoder a zero offset is stored, When the Servo Powers up it reads that value to work out the application zero position - The ONLY way to change that value is to use an absolute MAH with the servo loop open
Whenever the mechanical drive change is disconnected, this process may have to be performed (eg Gear box change or motor change)

Please tell us how this works for you

View attachment 20657

When you say with the 'servo loop open' what do you mean exactly?

woodj313 · Jan 17, 2012

Got it fixed. I manually positioned my axis at zero, and ran the MAH command. Now the position is retained after a power cycle.

Thanks a lot!

MichaelG · Jan 17, 2012

Glad to hear you have it sorted

- Thank you for posting your result

for anyone else reading later I used the wrong command
When you execute the MSO "Motion Servo On" command you are closing the loop
MSF "Motion Servo oFf" you are opening the loop servo loop open
This can be seen in servoTag.ServoActionStatus , Set when Closed, Reset when open

iant · Jan 17, 2012

Valuable information Thankyou

mohamedcito · Feb 3, 2012

Hello, It's very interesting because now I'm struggling with a new kinetix 6500 CIP drive, I lost the position of my absolute auxiliar encoder when I cycle the power, I don't know for what reason but When I started up again, I've the position value correct in the startactualposition and the incorrect position on the actual position, I want to know if somebody else has a issue of this kind,?,

and by the way how do I perform the first scan for .DriveEnableInput??

Thanks!!!!

chavak said:
Thanks MichaelG for the info. I will try this out when I need to use it next time.

What I was doing until now was -

1. Move the .ActualPosition value to a Real Tag when ever the positioning is completed.
2. Upon power up and for the first scan of the ".DriveEnable Status" load this stored value to the Actual position of the servo, using MRP command.

And of course this was done on the servo axis which was not able move upon power down, due to brake or the gear box itself.

Regards
_______

MichaelG · Feb 3, 2012

mohamedcito said:
I lost the position of my absolute auxiliar encoder when I cycle the power, I don't know for what reason but When I started up again, I've the position value correct in the startactualposition and the incorrect position on the actual position, I want to know if somebody else has a issue of this kind,?,

This is the normal and correct behavior.

StartActualPosition is the current position when a command was executed eg MAM

DO the Following to set the power up position

Change the axis homing method MAH to Absolute (Axis Properties) - Temporary - change back previous setting when finished
Set the "Position" value to the current position the servo is located (I use Axis.Actualposition once I have set up the position correctly)
Use the following Motion Direct commands
- MAS - Motion Axis Stop
- MSF - Motion Servo Off - servo loop must be Open
- MAH Motion Axis Home

mohamedcito · Feb 5, 2012

Unfortunately this didnt solved the problem I think is because it is an auxiliar encoder connected throught the servo drive kinetix 6500 and I don't know what else I can do I hope somebody that has have the same trouble could tell me how he solved

Thanks anyway Michael

MichaelG said:
This is the normal and correct behavior.

StartActualPosition is the current position when a command was executed eg MAM

DO the Following to set the power up position

Change the axis homing method MAH to Absolute (Axis Properties) - Temporary - change back previous setting when finished

Set the "Position" value to the current position the servo is located (I use Axis.Actualposition once I have set up the position correctly)

Use the following Motion Direct commands

MAS - Motion Axis Stop

MSF - Motion Servo Off - servo loop must be Open

MAH Motion Axis Home

MichaelG · Feb 5, 2012

mohamedcito said:
Unfortunately this didnt solved the problem I think is because it is an auxiliar encoder connected throught the servo drive kinetix 6500

That will do it - Any incremental encoder will always have a 0 position when you power up. This method only works for the servo motor internal encoder (or an absolute encoder eg SSI)

RedBagel · Aug 16, 2012

worked great, thanks

AB Kinetix 6000 losing postion after power cycle

woodj313

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