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BLDC DC Brushless Motor FOC Control Technology Solution

by AOMag | post a comment

From an energy point of view, the transition from traditional AC motors to smaller, more efficient BLDC motors is significant, but the complexity of designing BLDC control algorithms prevents engineers from doing this. The enthusiasm for the transition.

From small vibration motors in mobile phones to more complex motors used in domestic washing machines and air conditioners, motors have become everyday devices in the consumer sector. The motor is also an important part of the industrial field and is widely used in many applications, such as driving fans, pumps and other mechanical equipment. The energy consumption of these motors is very large: research shows that in China alone, motors consume 60% to 70% of the total industrial energy consumption, of which fans and pumps consume nearly four percent of China's overall power consumption. One of the points. Although this number may not be as high in other countries, reducing the energy consumption of motors in electronic systems has become a priority in the world.

Traditional alternating current (AC) motors have been widely used for more than a century. AC motors are the simplest induction motors, but they waste a lot of energy. This is because the AC motor only outputs a constant speed and cannot be adapted to changes in operating conditions. There are now some simple ways to adjust the speed of an AC motor (for example, a standard home fan that offers three speed options), but these methods have a limited range of applications and are difficult to transfer to more complex systems.

But for direct current (DC) motors, you can change and control the speed by changing the voltage to speed up or slow down the work depending on the application. This saves a lot of energy because the motor can be operated according to the required conditions. In general, DC motors are more efficient than AC motors.

Replacing a traditional AC motor with a smaller, more efficient BLDC motor saves energy and reduces costs, but the algorithms required for BLDC control are so complex that many designers are reluctant to convert. A dedicated IC specifically designed for BLDC motor control makes this job easier.

The DC motor can be designed as a brush motor or a brushless motor. Brushless DC (BLDC) motors are often the best choice for most applications. Such motors are more reliable and quieter, produce less electromagnetic radiation, and are safer because they eliminate sparks caused by brushes and commutators. BLDC motors are smaller and more efficient, which means they need less energy.

The BLDC motor operates at a lower temperature than the AC motor, and its more efficient design results in less heat generated by its internal components. This not only increases the service life of the bearing system, but also increases the reliability of the electrical system and the fan.

In addition, the BLDC motor has a higher power density than the AC motor. For the same energy output, the DC motor is smaller in size and weight than the AC motor. This makes the transport and installation of BLDC motors easier and less expensive.

However, the trouble with using a BLDC motor is that the system requires more sophisticated electronics to manage the motor. Motor control has always been a focus area for electronics engineers, and many developers cannot easily design the necessary control circuits due to lack of experience or expertise. The development of BLDC motors requires additional time and technical support, which means longer development cycles and higher system costs, making it more difficult for system manufacturers to transition from familiar AC motors to BLDC motors.

However, for more and more manufacturers, the complexity of using BLDC motors will not be offset by the increased demand for more energy efficient appliances. According to the 2011 IMS survey, approximately 40% of air conditioners in China use variable frequency control BLDC motors. This situation is on the rise and, to a certain extent, thanks to dedicated circuits designed for BLDC motor control.

The conventional method for controlling the BLDC motor employs a six-step process of driving the stator, thereby generating pulsations in the generated torque. The so-called "six-step square wave" process uses a Hall effect sensor to detect the permanent magnet position in the BLDC motor.

The six-step process is relatively simple, but is prone to noise, and is less responsive for more advanced applications that need to quickly change motor speed based on changes in conditions. In the case of a washing machine, the load varies depending on the selected washing cycle and also varies throughout the cycle. In drum type washing machines, this situation is more complicated, and gravity affects the motor when the clothes are rotated to the top of the drum.

In these cases, a more advanced algorithm is needed. Magnetic Field Oriented Control (FOC), which provides the response time required for fast speed changes, has become the motor of choice for today's more advanced energy-efficient appliances.

There are many ways to implement FOC. One method is to use a sensor (similar to the six-step square wave process method), but the sensor is more difficult to install and maintain, especially if the application involves complex harnesses or when the motor is exposed to water. A simpler, more cost-effective way to achieve FOC is to cancel the sensor. Sensorless FOC involves a constant rotor magnetic field generated by a permanent magnet on the rotor and is a very effective control method.

The FOC method allows the motor to run smoothly over the full speed range, produces maximum torque at zero speed, and is capable of rapid acceleration and deceleration. In fact, due to the small size, cost and power consumption of the motor, the many advantages of the sensorless FOC make it a popular choice in applications where performance is low.

Even so, implementing a sensorless FOC requires complex mathematical algorithms that may not be familiar to the average designer. In the past, designers often relied on complex digital signal processing (DSP) chips to implement sensorless FOC. Taking Infineon's FCM8531 as an example, it provides engineers with a specialized solution that makes it easier to develop sensorless FOC applications.

For systems using sensorless field-oriented control (FOC), Fast Semiconductor offers a specific application control unit, the FCM8531, with a parallel core processor. As shown in Figure 1, the FCM8531 consists of an Advanced Motor Controller (AMC) processor and an 8-bit 80C51-compatible MCU processor.

AMC is a core processor designed for motor control. It integrates a configurable processing core processor and peripheral circuitry to perform sensorless FOC motor control. System control, user interface, communication interface and input/output interface can be programmed for different motor applications via the embedded 80C51 MCU.

The advantage of the FCM8531's parallel core processor is that the two processors can work independently and complement each other. AMC handles tasks specifically for motor control such as motor control algorithms, PWM control, current sensing, real-time overcurrent protection, and motor angle calculations. The embedded MCU provides motor control commands to the AMC via the communication interface to perform motor control activities. Complex motor control algorithms are implemented in the AMC, so this approach reduces the software burden and simplifies the control system program.

We provide our users with the Motor Control Development System (MCDS) IDE and MCDS programming tools for developing software, compiling programs and real-time debugging. Designers can select the appropriate function from the library, quickly compile the program control functions and communication protocols, thus achieving the effects that were previously only possible on high-level DSPs.

From an energy point of view, the transition from traditional AC motors to smaller, more efficient BLDC motors is significant, but the complexity of designing BLDC control algorithms prevents engineers from doing this. The enthusiasm for the transition. Dedicated ICs specifically designed for BLDC motor control, such as Fast Semiconductor's FCM8531, make it easier for developers to use BLDC motors, helping to accelerate transitions and transitions to more efficient modes.

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