USA57 Revision
1.2
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Appendix E
Position Correction Mode and Overload Report Mode
Position Correction Mode (Software version 6.7 or higher)
Position correction mode, when enabled, will move until the encoder reads the correct number.
Once enabled, positions are given in quadrature encoder counts of the encoder (not in
microsteps). If the motor stalls during a move, the mode will re-attempt the move until the
encoder reads the correct number. This algorithm runs while the stepper is in motion and will
detect a stalled motor during a move.
There are two main types of feedback methods:
1. The first method is to place the encoder on the motor shaft.
2. The second method is to place the encoder on the component that is closest to the
actual item being positioned, and may be only be loosely coupled to the motor due to
backlash etc.
The Accuriss will work with either feedback method.
Setting Up Encoder Feedback
1. Set the encoder ratio “aE”.
NOTE: the encoder ratio should be changed when at the zero position for best performance.
Encoder Ratio = (microsteps/rev divided by quadrature encoder counts/rev) x 1000.
The encoder ratio must preferably be a whole number after the multiply by 1000. (If this is not a
whole number, see discussion further down).
The motor must be left in 256th microstep mode for correct operation of feedback mode.
For example, a 1.8-degree stepper (running in 1/256th step mode), which has 200x256
microsteps /rev, is hooked up to a 400-line encoder that has 1570 quadrature encoder counts.
aE
= ((200x256)/(400x4)) x1000=32000
Issue the command
/1aE32000R
to set this encoder ratio.
NOTE: If the encoder ratio is unknown, do the following:
1. Leave the encoder ratio at its power-up default of 1000.
2. Ensure that the encoder increases its count when the motor moves in the positive
direction. If not, switch the A & B output lines of the encoder, which will reverse the count