Feedback
Introduction
Feedback drivers are responsible of providing information of the rotor position or speed. One of the core principles of FOC is the knowledge of the rotor position, therefore, it is one of the core devices of the system. To be precise, FOC depends on the knowledge of the electrical angle of the motor, which is directly related to the rotor position via the number of pair poles.
There is a wide variety of feedback sensors. Their choice depends on the end application or required control. For example, Halls may be a good choice for speed control as detailed above. However, for accurate position control digital encoders may be a better candidate.
Halls
Hall sensors are a common type of feedback based on the Hall effect. The sensor is actually composed by three individual hall sensors equally distributed in the distance of one electrical revolution. The combination of the three output signals using the XOR function results in a square wave that provides an electrical angle resolution of 60 degress (Fig. 15). Because of their low resolution Hall sensors are frequently used for speed control. An important characteristic of Hall sensors is that their position feedback is absolute.
Fig. 15 Hall sensors signals versus the motor electrical angle.
API
- group spinner_drivers_feedback