So, I was studying a bit about driving current for Hybrid stepper motors and was faced with some ambiguity related to the Full Step excitation. In this reference, https://www.researchgate.net/publication/3219650_Mixed-Mode_PWM_for_High-Performance_Stepping_Motors, it is stated that the current shape to excite a stepper motor in Full Step must be like as follows:

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And measuring the phase current of my stepper motor, controlled by a drive in Full step mode, with my osciloscope, I got that image:

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So, all's well that ends well. However.... upon reading a datasheet related to a Toshiba stepper drive chip I've found this: enter image description here enter image description here


So, what am I missing here? Why Full Step phase currents differs from one reference to another?


Obs: It's a Hybrid Motor 1.8º per pulse (200 steps/per revolution)


1 Answer 1


A stepper motor has a fixed number of positions that it will "stick" to, it's steps. That number is related to it's physical construction (number of rotor poles, number of stator phases, number of coils per phase, unipolar or bipolar). In your case, that's 200 positions which makes the 360°/200=1.8° step angle.

Full stepping is when you cycle the phases in a way that turns the motor one step at each state change (which is the largest you can make - if you skip steps your motor will not progress). With a two phase bipolar motor, that's like a quadrature signal, with four different states. You just have to choose whether the pulses overlap or don't. Those modes are "One phase on" (sometimes called "Wave drive") or "Two phase on".

You will notice that, even though your first two graphs are different (one phase / two phase on), both take 4 clock cycles/steps to repeat the excitation waveforms, giving the same step angle at each clock cycle and the same number of steps to a full turn.


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