Endless Axes

Infinite axes

endless axes

Axes that can theoretically move endlessly in ether direction are supported in AMCS system. The limits of such axes are actually the range of the double-floating point format (-1.79769e+308,1.79769e+308) which practically gives endless axes operation.

drive (SERCOS) limitations

However, the drive-controller communication uses much smaller range it's position data is transferred using 32-bits data so the limits of internal drive position units are:
[-2 ³¹ ,+2 ³¹ ]. This is visible on properties: CCFB, CCMD, and CEXT. They are all integer type, 32-bit variables and as such have limited values.

AMCS position variables

The system automatically extends range position variables (pcmd,pfb,pext) to [mindouble,maxdouble] by counting the number of cycles of 32-bit range. Each time the position feedback (or external) passes 31 bit limit internal counter of revolutions (count_rev) is increased (decreased). So the position property values: PFB, PCMD , PEXT do not exhibit any discontinuities.

How is it done?

Detecting of 32 bit limit-pass is done by checking the current and the previous value of the feedback position obtained from the drive.
If the XOR operation on the most-significant bit of the current and the previous feedback value is 1 we increase(decrease) the revolution counter by 1 and then compute the pfb according: pfb = pfac*(cfb + 2 ³² *count_rev)

the revolution counter (count_rev) can be reset by:

• accessing position factor i.e. "pfac = pfac" or any other assignment.
• calling user function: MOT_RESET_ROLLOVER or MOT_RESET_EXROLLOVER