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Motor Stepping And Advance Frequency Control

IP.com Disclosure Number: IPCOM000101663D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 99K

Publishing Venue

IBM

Related People

Sakmann, W: AUTHOR

Abstract

This article describes an X-Y control using a personal computer and stepping motors. It is suitable for all kinds of machining equipment and plotters and allows the processing of vector data generated by computer-aided design programs. It does not need a continuous feedback system. Synchronization and calibration are carried out by home position switches.

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Motor Stepping And Advance Frequency Control

       This article describes an X-Y control using a personal
computer and stepping motors.  It is suitable for all kinds of
machining equipment and plotters and allows the processing of vector
data generated by computer-aided design programs.  It does not need a
continuous feedback system. Synchronization and calibration are
carried out by home position switches.

      Profiles are approximated by polygons at very small step width
(see figure).  Nevertheless, a precalculated frequency and a
programmable frequency control must be provided to move along a
straight line from point A with vector elements dx and dy to point B.
The frequency control is designed such that frequency ramps may be
programmed and applied to the stepping motors for high-speed skips
from the home to the work position and vice versa.

      The resolution and accuracy of the coordinate position depends
on the pitch of the selected motor and the pitch of the screw
spindle.  A motor with 200 steps/revolution and a screw pitch of 4 mm
yields a resolution of 0.02 mm per motor step.  For one polygon step,
several motor steps are required.

      Data processing and uncritical timing operations are performed
by the computer, and critical timing is handled by the hardware
adapter.  The description shows a two-dimensional geometrical
function which can be readily extended by a third dimension.

      Principle of operation
      The position control and the stepping frequency control
comprise the following steps which are performed when moving from the
current to the next position.
      o    A personal computer which calculates the current
coordinates xc and yc and the next coordinates xn and yn of a step
from a table.  The PC then calculates the deltas dx and dy and the
current slope dy/dx.
      o    The PC searches for the index i in a frequency table with
the elements slope(i), fx(i), fy(i), with i = 1 to n, until the
current slope equals slope(i).  The table is built such that,
depending on the slope, the selected frequencies fx(i) and fy(i) are
proportional to the deltas dx and dy, i.e. both motors stop at the
same time.
      o    The PC sequentially loads the next coordinates xn, yn and
the next frequency values fx and fy into data buffers during the
execution of the previous step.  The X-Y motor run latches are
monitored and the buffered data is transferred to work registers when
both latches are off.
      o    With the leading edge xrun and yrun signals, frequency
counters are preloaded, and first X-Y motor advance pulses are
generated by single shots.  Any subsequent m...