Re: [CAD_CAM_EDM_DRO] I'm curious

During this discussion someone asked for a closed loop definition
(I seem to have deleted it). I dug out my old lecturing notes (Robotics)
and hereby (changed to suit this forum) is my definition.

Position A (The required position) is compared with Position B (The current
position)
Any resulting discrepancy is applied to the current position B drive. This
process is
continuously repeated until such time as Position B is equal to Position A.

In a CNC content the permitted rate of change of position B will be
controlled by
the currently defined feed rate (variable for arc moves) and each driven
axis will have
it's own comparator circuit.

In a fully closed loop control system the actual current position must be
known in
relationship to a known reference start (datum) point. This will depend on
your
controller program being Abs or Rel where Abs references a fixed start point
and Rel references the position at the end of the last move command line.

Labouring the point. Move X 100, Move Y 100 is relative while
Move X100.Y0, Move X100.Y100 is the absolute to get to the same point
assuming
both start at X0,Y0.

Dave M.



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