What is a speed controller?

electronic speed controller for brushless motor

What is a Speed Controller?

A speed controller, also known as an ESC (Electronic Speed Controller), is essentially a driver used to operate brushless motors. Due to the internal structure, fixed windings, and specific design of brushless motors, they cannot be directly powered by DC voltage. Therefore, a speed controller is necessary to control their operation.

Brushless motors are widely used in applications like quadcopters, gimbals, boats, and other high-speed devices. Because these motors do not use brushes to transfer voltage, they have a longer lifespan, require less maintenance, and offer higher speeds.

A speed controller not only powers the brushless motor but also regulates its speed, direction, and braking based on the signals received from the control unit. Advanced ESCs can even provide feedback on motor performance and help optimize efficiency.

Applications of Brushless Motors and Speed Controllers:

• Drones and Quadcopters: For precise speed control and stability.
• Gimbals: To ensure smooth and accurate motion for cameras.
• RC Boats and Cars: For high-speed and reliable performance.
• Industrial Automation: In robotic arms and conveyors requiring high efficiency.
• Electric Vehicles: For effective speed regulation and power management.

By understanding how speed controllers work and their critical role in controlling brushless motors, you can effectively integrate them into your projects and applications. 🚀

How to Drive Brushless Motors and How ESCs Work

In this post, we will explore how to drive brushless motors and understand the operation of Electronic Speed Controllers (ESCs). As previously mentioned, an Electronic Speed Controller (ESC) is a driver used to power and control brushless motors, also known as BLDC motors (Brushless DC Motors).

Using an ESC to drive a brushless motor is not a simple task, as it requires a complex algorithm to synchronize the motor’s rotation. A typical sensorless brushless motor, often used in quadcopters, has three wires labeled A, B, and C.

Structure and Working Principle of Brushless Motors

A brushless motor has three wires, named A, B, and C. These wires are used to power the motor and determine the rotor’s position. To drive a brushless motor, the following steps are taken:

1. A and B are powered, C determines the rotor’s position.
2. A and C are powered, B determines the rotor’s position.
3. B and C are powered, A determines the rotor’s position.

This sequence of powering the wires generates a rotating magnetic field, causing the rotor to spin. The ESC uses Pulse Width Modulation (PWM) signals from the control unit to adjust the speed and direction of the motor. The absence of brushes reduces friction, resulting in higher speed, efficiency, and a longer lifespan.

Why is Driving a Brushless Motor Challenging?

Unlike brushed motors that can operate directly with DC voltage, brushless motors require precise control of their electromagnetic fields to function correctly. This is why an ESC is essential. The ESC continuously monitors the rotor’s position, adjusts the power delivered to each winding, and maintains synchronization.

Understanding how to drive brushless motors and the role of ESCs is essential for projects that require high-speed, precise control, and durability. If you plan to work with brushless motors, selecting the right ESC and understanding the control method is key to successful implementation. 🚀

Detailed Operation of Brushless Motors and ESCs

The explanations above provide a general overview of how to drive brushless motors. However, there are more specific cases and complexities to consider, such as polarity reversal and the accurate control of the motor’s rotation.

Advanced Control of Brushless Motors

When A and B are powered, wire C detects the rotor’s position. The microcontroller inside the ESC interprets the feedback from C to determine the rotor’s position, speed, and the timing for switching the phases. These switching moments are crucial for accurate control and efficient performance.

However, this is a simplified view of how a brushless motor works. To achieve proper rotation and acceleration, complex calculations are required, including monitoring the Back Electromotive Force (Back-EMF), managing phase shifts, and timing the switching sequences accurately. These calculations help maintain the synchronization of the rotor and stator fields.

ESC Drive Section — The Heart of Brushless Motor Control

The drive section of an ESC typically consists of 6 power MOSFETs organized in a three-phase H-bridge configuration. These MOSFETs handle the high-current switching required to control the motor’s speed and direction. A microcontroller processes the following tasks:

• Signal Processing: Analyzes the rotor’s position.
• PWM Generation: Controls the speed by adjusting pulse width.
• Timing Calculation: Determines the optimal timing for phase switching.
• Polarity Reversal: Ensures the correct rotation direction.

This combination of MOSFETs and a microcontroller allows the ESC to execute precise, high-speed switching, enabling the brushless motor to operate smoothly and efficiently.

Why Complex Calculations are Necessary

Unlike brushed motors that operate with a simple DC voltage, brushless motors require advanced algorithms to generate rotating magnetic fields. These calculations involve:

• Phase Shifting: Adjusting phase angles to maintain torque.
• Speed Feedback: Monitoring the motor’s speed for stable performance.
• Current Sensing: Ensuring safe operation and preventing overload.

Since these calculations are complex, ESCs are typically designed with dedicated microcontrollers optimized for real-time processing.

Understanding the complexities of ESC operation and brushless motor control can help you make informed choices for your projects and applications. If you’re interested in developing or modifying an ESC for a specific use case, you’ll need to dive deeper into motor control algorithms and hardware design.

How Does an ESC (Electronic Speed Controller) Work?

The drive section of an ESC consists of 6 power MOSFETs that perform the tasks described above. Additionally, a microcontroller is used for organization and complex calculations.

The Connection Method of MOSFETs

The MOSFETs are connected as shown below, and a microcontroller handles the control operations. It is crucial to select appropriate MOSFETs that can handle the required current.

The diagram below illustrates the structure of a brushless motor.