BLDC motor control using Brushless Motor Shield (TB6605FTG)


I am working on controlling a bldc motor using Brushless Motor Shield (TB6605FTG). Before controlling the motor, I wanted to operate the motor itself by changing the pwm width whether the open-loop control works for this motor. However, the motor operation was weird. When I assign 0~20 out of 255 into the pwm port in Arduino, the motor was operated with the maximum rotational speed. In fact, the motor speed is always same regardless of the value between 0 and 20. However, when I assign 21~255 into the pwm port in Arduino, the motor was not operated at all.

Also, when I use the example code provided by the company, the motor is only operated in this range (0~20). That is, the motor speed is changing like sinusoidal curve even though the code has pid control.

Is there anyone who has similar issues when operating the motor? How you can solve this problem?