Conference Paper · October 013 doi: 10. 1109/cobep. 2013. 6785223 citations reads 2,638 authors


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DRIVES

A.
 Driving Schemas 
Besides the mechanical design, the final resolution of a 
stepper motor is also dependent on how the stepper motor is 
driven. These machines are digital like actuators, in a sense 
that only one of its windings is energized at a time. But, if 
one drives the motor with smoother signals, a smoother 
motion is yielded. So, instead of driving a winding at a time 
to its nominal current, a discretized sine-squared (sin²) wave 
can be applied in order to achieve smoother motion. 
Traditional driving schema is known as full step. If one 
breaks the transitions in 2, it is known as half step. For more 
fractional driving schema, it is named n-th micro step, were n 
is the number of subdivisions on the signal. The Tables 1, 2 
and 3 illustrates the three driving schemas, respectively. On 
those Tables, the symbols ½, ¼ and ¾ actually are shorted of 










Table 1 – Lookup table used for full step driving schema. 
   









0 1 0 











Table 2 – Lookup table used for half step driving schema. 
   









½ ½ 0 








½ 
½ 








0 ½ ½ 






½ 


½ 
Table 3 – Lookup table used for micro step 1/4 driving 
schema. 
   



   














¾ ¼ 0 

10 


¾ ¼

½ 
½ 


11 


½ 
½ 

¼ 
¾ 


12 


¼ 
¾ 





13 






¾ ¼ 0 
14 
¼ 0 

¾


½ 
½ 

15 
½ 


½ 


¼ 
¾ 

16 
¾ 


¼ 
Those tables are used as current reference for a controlled 
current source, which is better explained in the next subtopic. 
B.
 Controlled Current Source 
From Equation (1), the torque exerted by the motor is 
related by the displacement from the rest position and also to 
the current flowing on the winding. For a constant holding 
torque, a controllable constant current source must be 
implemented. 
In order to do so, H-Bridge circuit along with comparators 
and logic circuitry can be used. Such a circuit is depicted on 
Figure 3.Transistors Q1 through Q4 are power transistors and 


carry the load current. Diodes D1 through D4 are free-
wheeling diodes. 

!"#$.
is a low resistance resistor in series 
with load current, generating a small voltage signal, 
&('), 
which is filtered with a low pass filter, in order to remove 
high frequency noise, and compared to a current reference, 
finally switching on and off Q1 through Q4
The values applied to the inputs In1 and In2 are the values 
of the current index of the active index table, presented in 
last subsection. The active index table depends on which 
driving schema is being used. 
Figure 3 – Diagram illustrating a controllable current source. 
III.
IMPLEMENTATION OF THE SYSTEM 
The circuit presented by Figure 3 relies on analog devices, 
such as comparators, and sources, such as the adjustable 
current reference. Pure analog circuits usually are harder to 
implement and are more expensive. The developed system 
employs digital, analog and power circuits implement the 
functionalities of the blocks previously described. 

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