Abstract: This paper introduces a brushless DC motor control system based on the ST72141 dedicated motor control chip, briefly describing its own back EMF detection principle and the hardware and software design for implementing the system control.
Keywords: brushless DC motor; ST72141; control system
Brushless DC motors, due to the use of permanent magnet materials for rotor excitation, have no excitation losses and possess advantages such as small size, light weight, simple structure, convenient maintenance, reliable operation, high efficiency, energy saving, and easy control. At the same time, brushless DC motors use electronic commutators to replace mechanical brushes and mechanical commutators. Therefore, brushless DC motors retain the characteristics of ordinary DC electromechanical motors, and thus have been widely used in various military and civilian fields.
Brushless DC motors emerged and developed alongside digital control technology; therefore, single-digital control is one of the main control methods for brushless DC motors. This allows for precise control of sensorless brushless DC motors without the need for Hall effect sensors. The motor's three-phase windings are directly connected to the input interface of the ST7214 chip to obtain the motor rotor position. (System structure and control strategy are described below.)
Brushless DC motors require rotor position signals to control the synchronous operation of the stator magnetic field and rotor in the inverter during operation. Most brushless DC motors rely on position sensors to detect rotor position. These sensors not only increase cost and complicate system connections, but also...
The commonly used sensorless control strategy for insufficient speed is the traditional back EMF zero-crossing detection method (terminal voltage detection and phase voltage detection). However, this method requires voltage division and filtering. Voltage division reduces the sensitivity of signal detection at low speeds, especially during startup when the back EMF signal is weak; filtering causes a phase shift in the zero-crossing signal, which increases with speed. This phase shift increases the complexity of commutation control at high speeds.
Details: Brushless DC Motor Control System Based on ST72141 Chip
