BLDC Motor Controller Design Principles and Applications

11 min readMar 14, 2023

Brushless DC (BLDC) motors are gaining popularity in a wide range of applications due to their many advantages over traditional DC motors. However, controlling the speed, torque, and position of a BLDC motor requires an efficient and reliable motor controller. The design principles of a BLDC motor controller involve a complex interplay of power electronics, control algorithms, sensor feedback, thermal management, protection features, and EMI/EMC compliance

Apart from that, control algorithms are essential for achieving accurate speed and position control of the motor. These algorithms are typically implemented on a microcontroller, which communicates with various sensors, such as encoders or Hall-effect sensors, to measure the motor’s position and speed.

Table of Contents

This blog post will go through each form of BLDC motor controller in more detail, as well as the difficulties in developing a BLDC motor speed controller. Moreover, brushless DC motor applications will also be covered. Stay tuned as we will also explore how Kemsys can assist you in getting a unique BLDC Controller design.

What is a Brushless DC motor controller?

A Brushless DC (BLDC) motor controller is an electronic device that regulates the operation of a BLDC motor. A BLDC motor, as the name suggests, does not use brushes to transmit electrical power to the rotating motor shaft. Instead, it uses a set of permanent magnets on the rotor and fixed coils, called stator windings, to produce motion. Due to their high efficiency, low noise, and long lifespan, BLDC motors are applicable in various applications, such as robotics, electric vehicles, industrial automation, and consumer electronics.

A BLDC motor controller performs several functions to ensure efficient and smooth motor operation. Firstly, it converts the DC voltage from a power supply to a three-phase AC voltage used to energize the stator windings. Next, the controller controls this AC voltage to create a rotating magnetic field that interacts with the permanent magnets on the rotor, producing torque and rotational motion.

Secondly, the controller monitors the position of the rotor to determine when to energize each stator winding using either a sensor or a sensorless method. Sensored controllers use Hall effect sensors or other position-sensing devices to determine the position of the rotor. In contrast, sensorless controllers use mathematical algorithms to estimate the rotor position based on the back-EMF voltage generated by the motor.

Thirdly, the controller regulates the current flowing through each stator winding to ensure the motor operates within its rated specifications and prevents overheating and damage using Pulse Width Modulation (PWM) to control the duty cycle of the AC voltage applied to the stator windings.

Finally, the controller can also provide feedback signals, such as motor speed and temperature, to the system control unit for monitoring and control purposes.

Types of BLDC Motor Controllers

Several types of BLDC motor controllers are available, each with advantages and disadvantages. Let’s have a look on the most common ones-

Sensored BLDC Motor Controllers

Sensored BLDC motor controllers are the most common type of motor controller used in BLDC motors. They rely on feedback from sensors that sense the position of the rotor. Typically, the rotor’s magnetic field is detected using Hall effect sensors. Then, the controller uses the information from the sensors to determine the correct timing for the electronic switches that control the motor.

One advantage of using sensored BLDC motor controllers is that they provide accurate position information, which can control the motor’s speed and torque more precisely. They also offer better performance at low speeds and smoother operation at all speeds. However, they are more expensive than sensorless controllers and require additional wiring and components.

Sensorless BLDC Motor Controllers

Sensorless BLDC motor controllers aim to operate without feedback from sensors. Instead, they use a technique called back-EMF sensing to detect the position of the rotor. Back-EMF is the voltage generated when the rotor moves through the stator’s magnetic field. The voltage is related to how fast the motor goes, so it can use to determine where the rotor is.

These controllers are less expensive than sensored controllers and require fewer components. They are also more effortless to install and demand less wiring. However, there are chances that they may not provide as precise speed and torque control as sensored controllers. They also have lower performance at low speeds and may experience more vibration and noise.

Field-Oriented Control (FOC) BLDC Motor Controllers

Field-oriented control (FOC) BLDC motor controllers are sensored controllers that use a mathematical model to control the motor’s speed and torque.

First, FOC controllers use information from the sensors to determine the status of the rotor.

Then they use a mathematical model to calculate the appropriate voltage and current to apply to the motor.

As a result, FOC controllers perform better than others and get used in high-performance applications such as electric vehicles.

FOC controllers have several advantages over other types of controllers. They provide accurate speed and torque control, remarkable efficiency, and reduced vibration and noise levels. They can also control the motor in both directions and be programmed to provide different performance profiles. However, FOC controllers are more complex than others and require more advanced programming and tuning.

Sinusoidal BLDC Motor Controllers

Sinusoidal BLDC motor controllers are FOC controllers that use sinusoidal waveforms to control the motor’s speed and torque. Sinusoidal controllers use a sinusoidal waveform to maintain the current and voltage applied to the motor. The waveform is synchronized with the rotor’s position and provides smooth, efficient operation.

Sinusoidal controllers provide several advantages over other types of controllers. They provide accurate speed and torque control, excellent efficiency, and reduced vibration and noise levels. They also provide smoother operation than other controllers and are commonly used in high-performance applications such as electric vehicles and robotics.

Trapezoidal BLDC Motor Controllers

Trapezoidal BLDC motor controllers are sensorless controllers that use a trapezoidal waveform to control the motor’s speed and torque. Trapezoidal controllers use a waveform synchronized with the rotor’s position, providing smooth and efficient operation.

Trapezoidal controllers are less expensive than other controllers and require fewer components. They are also more effortless to install and demand less wiring. However, they may not provide as precise speed and torque control as sensored controllers. Issues related to lower performance at low speeds can also be faced.

Hybrid BLDC Motor Controllers

Hybrid BLDC motor controllers are a type of controller that combines the features of sensored and sensor-less controllers. Hybrid controllers use sensors to detect the position of the rotor at low speeds and then switch to sensorless operation at higher speeds. It allows the controller to provide accurate position information at low speeds and high efficiency at high speeds.

Hybrid controllers provide several advantages over other types of controllers. They provide accurate speed and torque control, excellent efficiency, and reduced vibration and noise levels. They also provide better performance at low speeds than sensorless controllers and are less expensive than full-featured sensored controllers.

Selecting the appropriate type of BLDC motor controller is crucial to achieving optimal motor performance for a specific application. While each controller type offers advantages and disadvantages. Understanding the application’s specific needs is vital to making an informed decision. For instance, sensored controllers may be better for applications that need precise control of position, while sensorless controllers may be better for applications that need to save money. FOC and sinusoidal controllers offer superior performance but require more advanced programming and may be better suited for high-performance applications. Trapezoidal controllers are an economical choice, while hybrid controllers provide a balance between accuracy and cost. By evaluating the application’s requirements, selecting the appropriate BLDC motor controller can improve motor efficiency, reduce vibration and noise, and optimize overall system performance.

Challenges of Making a BLDC Motor Speed Controller

Not many difficulties arise at the time of operating the BLDC Motors but when it comes to designing and building the BLDC Motor speed controller, it can be a challenging task. There are several key points that you have to keep in mind while designing. Here are some of the challenges that you might face –

Control Algorithm

As far as the challenges are concerned, controlling algorithms are the most challenging part that as to be done accurately because they directly regulate the motor speed, maintain stability, and minimizes noise. To manage the motor’s speed and torque output, the controller must properly perceive the motor’s location otherwise you won’t be able to have full control over the speed.

Power Electronics

Another challenge is designing and building the power electronics which are important to drive the motor. It includes the gate drivers, power switches, and other valid components that are crucial to generate high-frequency AC signals which have a direct impact on deriving the motor.

Heat Management

Effective heat management is crucial in the design of BLDC motor speed controllers, as these motors can generate a substantial amount of heat. If the controller becomes too hot, it can lead to damage to the system components, reducing the lifespan of the controller and the motor. Therefore, it is essential to incorporate proper cooling and thermal management measures to prevent overheating of the controller.

Noise and Interference

Electrical noise and interference can create problems in the motor’s operation, which can ultimately affect the accuracy of the speed control. Therefore, to ensure accurate and responsive control of the BLDC motor, it is crucial to design the controller in a way that minimizes the effects of electrical noise and interference. For this, you have to design the controller carefully as it plays a crucial role in maintaining the speed.

System Integration

The integration of BLDC motor speed controllers with additional control elements and systems, including sensors, microcontrollers, and power sources, is common but it can be difficult to make sure that these systems operate together without a hitch. The whole process can be hectic and time-consuming.

Extra Cost

Every company prefers cost-effective solutions as compared to the ones which require high funding. Here building a BLDC motor speed controller can be expensive, as it requires high-quality components and careful design and testing. Because of this, making a cost-effective controller can be challenging.

Overall, building a BLDC motor speed controller requires a solid understanding of motor control theory, power electronics, and control system design. By carefully considering these challenges and developing a well-designed controller, it is possible to build a reliable and effective system for controlling the speed of a BLDC motor.

Application Area of Brushless DC Motors

Brushless DC (BLDC) motor controllers are used in a wide range of applications that require high efficiency, precision, and reliability. In below mentioned areas, BLDC Motor controllers performs a major role in enhancing the functionality of the device.

Industrial Automation:

In industrial automation, the use of BLDC motor controllers has become increasingly common due to their efficiency, reliability, and precise control over motor speed and torque. Below mentioned are some of the benefits which BLDC provides in Industrial automation.

Robotics
Conveyors
Pumps and Fans
CNC Machines
Material handling equipment’s

Electric Vehicles

The use of BLDC motor controller in electric vehicles is essential to ensure the vehicle’s efficient and reliable operation. They are used in electric vehicles such as electric cars, electric bikes, and electric scooters. The controllers regulate the motor’s speed and torque to ensure efficient power consumption and smooth operation. BLDC motors controller is preferred in EVs due to –

Propulsion
Regenerative Braking
Power Steering
Motor protection
Batter management

The controller helps to enhance the vehicle’s performance, expand its range, and prolong its life by being able to precisely control the motor’s speed and torque, enable regenerative braking, manage the battery’s performance, and protect the motor.

Robotics

BLDC motor controllers are widely used in robotics applications. Here the BLDC motor controller plays a crucial role because it provides precise and accurate control over the motor speed and torque. It is essential as it ensures efficient power consumption, smooth operation, and precise motion control which is the base of its functionality. Below mentioned are the major functionalities of the BLDC motor controller used in Robotics –

Motor Control
Motion control
Battery Management
Motor Protection
Sensor Integration

Overall, it is important to use the controller in Robotics as they are responsible for the Robot’s efficient and reliable performance.

HVAC Systems

In HVAC (Heating, Ventilation, and Air Conditioning) systems, BLDC Motor controllers play a major role when it comes to controlling the speed of the motor that drives the air handler or the fan. It is also essential to reduce energy consumption and increase the system’s efficiency. Below mentioned are the key parts of HVAC Systems where the BLDC motor controller is used.

Variable Speed Control:
Energy Savings
Noise Reduction
Motor Protection
Easy Integration

Overall, the use of BLDC motor controllers in HVAC systems is essential to reduce energy consumption, increase system efficiency, and improve the comfort level of the building occupants.

Medical Devices

BLDC motor controllers are used in a number of medical devices like surgical tools, medical pumps, and medical imaging systems due to their high efficiency, reliability, and accuracy. They are responsible for providing precise and controlled motion for devices that require high accuracy, speed, and safety. Let’s check out some of the key offerings of BLDC motor controllers that are being used in medical devices:

Motion Control
Energy Efficiency
Compact Design
Safety
Easy Integration

Medical device manufacturers consider the controller an ideal choice because it allows precise control of the motor’s speed and torque, as well as safety features and easy integration.

Consumer Electronics

BLDC motor controllers are used in various types of consumer electronics applications like power tools, electric shavers, and cooling fans. They are highly preferred in consumer electronic businesses due to their high efficiency, low noise, and long lifespan. It is important to have reliable and efficient control over the motor speed to operate these applications. Here are few of the benefits provided by BLDC motor controller to consumer electronics –

Motion Control
Energy Efficiency
Low Noise
Long Lifespan
Easy Integration

Manufacturers of consumer electronics choose the controller because of its exact control over the motor’s speed and torque, quiet operation, extended lifespan, and simplicity of integration.

Custom BLDC Controller Design by Kemsys

We have extensive experience and expertise concerning the design and manufacturing of Electric Motor Controllers. Our innovative hardware solutions can be deployed to overcome difficult spatial restrictions and comply with stringent environmental requirements.

We create and produce controllers for DC motors (BLDC). The various BLDC motor types are ideal for a variety of applications, and we have experts who better understands their applicability. We provide brushless motor controls with high-performance, high-tech characteristics that are sensor-less and sensor-controlled.

Providing customized hardware modifications and IoT hardware, software, and smart product development services help your clients tailor their products to their specific business requirements, which gives them a competitive edge in their respective industries.

Conclusion

In conclusion, due to their numerous advantages over conventional DC motors, including improved efficiency, a longer lifespan, and less costly maintenance. Brushless DC (BLDC) motors are becoming more and more well-liked in a variety of applications. However, controlling the speed of a BLDC motor can be a challenging task due to its complex electrical and mechanical characteristics. This has led to the development of various types of BLDC motor controllers, each with its own advantages and limitations.

Kemsys provides custom BLDC motor controller design services that aid in overcoming these difficulties and provide tailored solutions to satisfy certain application needs. In the end, it is predicted that the widespread use of BLDC motors and controllers will continue as the industry looks to increase productivity and save costs.

Looking for a reliable partner for your brushless DC motor controller needs? Contact us today to learn more and take the first step towards optimized efficiency and reduced costs for your business!

Originally published at: https://kemsys.com/blog/bldc-motor-controller/