Altering motor resolution via MRES field

["Marco A. Barra Montevechi Filho via Tech-talk" <tech-talk at aps.anl.gov>]

Hello all,

We are using a micosIOC (https://github.com/epics-motor/motorMicos.git) to control an UPR-160 motor: https://www.pi-usa.us/fileadmin/user_upload/pi_us/files/product_datasheets/Air_Bearing_Rotation_Stages_UPR-Air_Family.pdf

According to the motor technical data, its resolution can go down to 0.00004 degrees. The current IOC has a motor with .MRES=0.04 deg, so we cant make movements smaller than this. When i caput MRES to 0.004, i can caput .VAL from 0.1 to 0.105, for example, and the motor will move.

However, although the .RBV shows the movement incrementing 0.005 degrees, the actual observed movement is of 0.05 degrees. In other words: changing the motor MRES to ten times lower makes the motor move ten times more than what is commanded.

We (me and Augusto Horita) also tried using the SMChydraChangeResolution("Hydra1", 1, 0.004) function and leaving MRES as 0.004 in substitutions, but the same behavior was found.

Am i doing something wrong? 

Thanks for any help,

Marco

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