What are the advantages of brushless DC motor control system

Brushless DC Motor Control System

Brushless DC motor (BLDC) is also known as electronic commutation motor. Compared with traditional brushed motor, its internal rotor is changed from wire winding to permanent magnet, carbon brush is replaced by electronic commutator, external DC generates AC through electronic commutator, and then drives the motor. With the development of mechanical and electronic technology, brushless DC motors have occupied an increasingly important position in social production and life. With the characteristics of wide plasticity and stable operation, the use of brushless DC motors is also growing. This design is based on a brushless DC motor control system with a bit sensor. Through the working principle of the brushless DC motor, a three-phase full-bridge drive circuit is used to design a closed-loop control system, which can realize adjustable motor speed and display speed. The entire design is realized through simulation software, and the speed, stator current, line voltage, etc. of the brushless DC motor are analyzed.

Brushless DC motors have simple structures, high output and high efficiency, and are widely used in robots, household appliances and other scenarios. For example, many humanoid robots, quadruped robots, robotic arms, drones and gimbals now use brushless motors.

Brushless DC motors (BLCD) and permanent magnet synchronous motors (PMSM) are common. Their structures are basically the same, but there are slight structural differences. Therefore, brushless DC motors often use trapezoidal waves or square waves to drive, while permanent magnet synchronous motors are more likely to use sinusoidal waves to drive.

In recent years, brushless DC motors have been increasingly used in many fields. In addition to maintaining the superior starting performance and speed regulation performance of brushed DC motors, their biggest feature is that they do not have a mechanical contact structure composed of a commutator and brushes, so they have a series of advantages such as long life, low noise, reliable operation, and easy maintenance. In addition, since their speed is not limited by mechanical commutation, they can be smoothly regulated in a wide range. Brushless DC motors are used in electric bicycles to replace the original brushed DC motors. Due to the use of electronic contactless commutation, it not only prolongs the service life of the motor, but also makes speed regulation convenient, easy to control, and runs smoothly.

This paper takes brushless DC motor as the research object, brushless DC motor control system as the control target, PWM as the control design technology, and PIC series microcontroller as the main control chip. The article mainly studies its voltage commutation, overcurrent protection, undervoltage protection, starting and speed regulation, and pure stall protection. The research of the article includes two aspects, hardware and software. The functions realized in the hardware aspect include: power supply design, handlebar input design, drive circuit design, overcurrent protection circuit design, undervoltage protection circuit design, and commutation circuit design.

Advantages of brushless operation

The brushes of a conventional motor transfer power to the rotor windings, which, when energized, enter a stationary magnetic field. Friction between the stationary brushes and the rotating metal contacts on the rotating rotor causes wear. In addition, power can be lost due to poor brush-to-metal contact and discharge of the wires.

Since BLDC motors do not use electrical vibrations, but use an "electronic commutator", the reliability and efficiency of the motor are improved by eliminating this wear and power loss. In addition, BLDC motors have many advantages over brushed DC motors and induction motors, including better speed and torque characteristics: faster dynamic response: silent operation, and a higher speed range.

Additionally, the higher torque ratio provided relative to motor size makes it ideal for applications such as washing machines and electric vehicles, where high power is required but compactness and lightness are key factors. (It should be noted, however, that brushed DC motors do have higher starting torque.)

Because the magnetic fields generated by the stator and rotor rotate at the same frequency, BLDC motors are called "synchronous" types. One benefit of this arrangement is that BLDC motors do not suffer from the "slip" phenomenon typical of induction motors.

Although motors can be single-phase, two-phase, or three-phase, the latter is the most common type and will be discussed here.

The stator of a BLDC motor consists of steel laminations that are slotted axially to accommodate an even number of windings along the inner circumference. Although the BLDC motor stator is similar to an induction motor, the windings are arranged differently.

The rotor consists of permanent magnets and 2 to 8 NS pole pairs, more magnets increase the torque and smooth out the so-called torque ripple, thus reducing the power output of the motor. The disadvantages are a more complex control system, increased cost and reduced maximum speed.

Traditionally, ferrite magnets have been used to make permanent magnets, but contemporary units tend to use rare earth magnets. While these magnets are more expensive, they produce a greater flux density, allowing the rotor to be smaller for a given torque. The use of these powerful magnets is a key reason why BLDC motors can deliver higher power than electric DC motors of the same size.