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R01AN0168ED0101 Rev. 01.01 37
Application Note
Chapter 7 Performing Zero Point Detection
7.1 Zero Point Detection (ZPD) Theory
In order to define the ZPD table entries, base knowledge about zero point
detection is required. Let’s have a look into a simplified stepper motor. In the
following figure, four steps of movement are shown, one for each quadrant of
the motor’s anchor.
Within each quadrant, it is possible to detect, whether the motor could move,
or whether it had hit its mechanical stop, and therefore, it could not move.
The detection of the mechanical stop is performed by measuring inductive
pulses one one coil set, while the other coil set is powered for a movement of
the anchor.
Figure 7-1 Four Quadrant Zero Point Detection
1
Surely, it is not required to perform the measurement for all four quadrants.
Alternatively, it’s also possible to move the motor a full turn, and perform a
measurement only in one of the four steps above.
Regarding the ZPD algorithms, there is some trade-off between quality
(smoothness of movement, noise on hitting the stop) and the capabilities of the
motor and the stepper motor driver hardware. From 1 to 4, the quality of ZPD
increases:
1. Single-Quadrant ZPD

One full turn of the motor in 90° steps, one measurement at 0°.
2. Single-Quadrant ZPD with PWM movement
One full turn of the motor in fine PWM microsteps, accelerating sequence,
one measurement at 0°.
3. Four-Quadrant ZPD
Quarter-turn of the motor, measurement after each quarter-turn.
4. Four-Quadrant ZPD with PWM movement
Quarter-turn of the motor by fine PWM microsteps, accelerating sequence,
measurement after each quarter-turn.
ISM supports all four approaches.
1)
Figure by “Lessons In Electric Circuits copyright (C) 2000-2012 Tony R. Kuphaldt”
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