The aim of the control is to maintain the desired Speed regardless of the applied load to the shaft. When

a resistance torque is applied to the shaft, a reduction of the speed takes place. This implies an incre-

ment in the wave period of the Hall sensors signals and then a decrement of the sine frequency in the

phases, to follow sensors information.

In this case, the only way to lead the rotor at the previous speed is to increase the winding current in or-

der to balance the load torque. Fuzzy Controller, in fig. 6, performs this task. ST52x301 reads the speed

Figure 4. Phase voltage and current

Figure 5. Control topology

Speed_Ref

Error

FUZZY

CONTROLLER

PWM

MOTOR

DRIVER

Speed

®

AN1113 - APPLICATION NOTE

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