How important is OB95 and how to use it?

Technology Team

Hello,

 use MC_Stop for Alarm reaction.

When manipulating PositioningAxis_1_Actor_Interface_AddressOut.STW1

it is  necessary do it in MC-PostServo (OB95).

 How important is OB95 and how to use it? I'm working on servo motion.

------------------------------------------------------------------------------------------
Split from modify reaction of follwing error with TO.

PopiMatic1989

the ob post servo is important because it allows an overwrite of the structure of the technological object, which otherwise would have control over the control word

 I understand what you mean, but this might be misunderstanding to anyone who does not yet know the issue.

OB95 is OB MC-PostServo. This OB is executed right after OB MC-Servo has run.
The issue with manipulating the data in the telegram now is the following: The content of the telegram that is used by a technology object (TO) is written by this TO, and this happens in MC-Servo OB.

So if you manipulate the telegram data let's say in OB1, then with every call of OB MC-Servo the TO overwrites what you manipulated in OB1.

Therefor you should use OB MC-PostServo (OB95) for this. This way the TO writes the telegram data in MC-Servo OB, and every time right after this has happened, you will overwrite this data with what you want to manipulate.

How to use the OB? -> Add this to your program, from there on just work with it as you do with any other OB.

BUT: Be carefull not to put too much code into MC-PostServo OB (and if present the same applies to MC-PreServo and MC-PreInterpolator)! All Motion OBs need to be finished within the cycle time you have parametrized at MC-Servo OB's propierties. In case they take longer, you will have an overflow, which in worst case leads to PLC stop! Therefor make sure the code you can enter into OBs PreServo, PostServo and PreInterpolator is small and fast, so that all motion OBs still get finished in time. You might also consider to increase MC-Servo OB's cycle time, in case this is too small then.

Regards,
daviso