Teach Position with SFD feedback - PLCopen Motion







For KAS applications:

-   using the  PLCopen Motion engine

-   with a total travel range  of 1 revolution

-   that use  a SFD single turn absolute position feedback device.

this note outlines how to teach a desired position to a specific physical position then have the offset applied on each project startup

Step 1: Read the absolute position from the drive. Note with SFD or resolver feedback the feedback value will be - 1/2 UU/rev to + 1/2 UU/rev. (UU= UserUnits). Example if UU  = 360 the range will be -180 to +180

                        

Step 2: Teach the Position. Below, the parameter b_SetupMotorPosition  and MC_SetPos function block are used to determine the PostionOffset between the present Absolute Position and the desired Teach Position. This code is only executed once (bSetupMotorPostion = 1) to define a new offset (not on every powerup).

                       

The Position Offset and Teach Position are saved through PxMM power cycling

                      

 

Step 3: On each powerup apply this offset  by calculating the present offset and using MC_SetPos to redefine the starting position

 

                   

 

The attached code has the following controls in the  Control Panel for helping to understand the operation