Brushless motor + encoder: the key combination for high-precision closed-loop control

 

With the rapid development of technology, people's expectations for product performance are constantly increasing. Not only in traditional high-precision fields such as industrial automation, robotics, and medical equipment, but also in many emerging applications such as consumer electronics, smart homes, and unmanned equipment, higher control requirements for motors are beginning to be put forward - they must not only run quickly, but also be controlled accurately and respond sensitively.

 

In these scenarios, brushless DC motors (BLDC) have become the core drive choice due to their high efficiency, low noise and long life . However, the characteristics of the motor itself are far from enough. To achieve truly high-precision and high-stability control, a "closed-loop control" system must be introduced.

Open-loop control vs. closed-loop control: What is the difference

In an open-loop control system, the controller sends instructions to the motor (such as setting speed or voltage), and the motor runs according to the instructions, but the system does not monitor in real time whether the motor is performing as expected. This method has a simple structure and low cost, and is suitable for applications with small load changes and low accuracy requirements.

 

In contrast, closed-loop control continuously monitors the actual state of the motor (such as speed, angle or position) through sensors such as encoders, and transmits feedback signals back to the controller in real time. The system continuously adjusts the control instructions based on these feedbacks, thereby greatly improving control accuracy, stability and anti-interference ability.

 

Overview of open loop vs. closed loop:

Control method	Open loop control	Closed-loop control
Is there any feedback	no	yes
Control accuracy	Lower	high
Anti-interference ability	Poor (easily affected by load fluctuations)	Strong (correct running deviation in real time)
System Cost	Low (simple system structure)	Slightly higher (requires encoder and other sensor support)
Typical Applications	Fans, pumps, electric toys, etc.	Automation equipment, robots, precision medical instruments, high-end manufacturing systems, etc.

Therefore, in pursuit of high-precision and reliable control requirements, closed-loop control has become an important part of the brushless motor system. To build a high-performance closed-loop system, the encoder is the key component that connects "perception" and "control".

 

In a closed-loop control system, the encoder is one of the most critical feedback components. It can accurately detect the speed, position and direction of the motor and feed this information back to the controller to achieve precise control.

 

1. The basic function of the encoder

The encoder is directly mounted on the motor or integrated into the motor to measure the rotation state of the motor shaft. By outputting signals in real time, it helps the controller determine the current position change of the motor, thereby achieving closed-loop control of speed, position and angle.

 

2. Types of encoders

According to the output mode and structural principle, encoders are mainly divided into the following two categories:

Incremental Encoder

The incremental encoder outputs continuous pulse signals (such as A, B, Z signals), and the controller determines the speed and direction by counting these pulses. This encoder has a simple structure and low cost, and is suitable for low- and medium-precision motion control.

 

Absolute Encoder

Each position point has a unique code value output, and the current position information can be retained even after power failure. It is suitable for control scenarios that require high precision and high reliability, such as medical equipment, robots, automated production lines, etc.

3. Output signal mode

Different encoders have different output signal types and interface methods, common ones include:

· ABZ signal (incremental): A and B are orthogonal pulse signals used to determine the speed and direction, and Z is the zero position signal used for reset or synchronization.

· UVW signal: commonly used for brushless motor commutation synchronization signal, suitable for servo control system.

· Communication protocols such as SSI, RS-485, and CANopen: They are mostly used for absolute encoders, can accurately transmit position information in digital form, and have stronger anti-interference capabilities.

 

4. Installation structure and principle technology

According to the structure and detection principle, encoders can also be classified as follows:

Installation method:

· Shaft end type: The encoder is directly connected to the motor output shaft, with high adaptability and easy replacement.

· Hollow shaft type: The encoder is hollow and can be inserted into the motor shaft, saving space and compact installation.

· Integrated: The encoder and motor are directly integrated in one housing, which is fully debugged at the factory and suitable for system integration.

 

Induction principle:

· Photoelectric encoder: reads position signals through gratings and photoelectric sensors, with high resolution, suitable for high-precision applications.

· Magnetic encoder: uses magnetic field changes to sense position information. It has a more robust structure and better anti-pollution performance, making it suitable for industrial environments.

 

The encoder is not just a measuring tool, it is an indispensable part of the entire closed-loop control system. In practical applications, only the encoder, brushless motor and controller need to work closely together to achieve high-precision motion control.\

 

1. How does the controller read the encoder signal?

The controller determines the motion state of the motor shaft by receiving the signal (such as pulse, digital data or analog voltage) output by the encoder. The controller runs the control algorithm (such as PID algorithm) inside, compares the difference between the set target and the current state in real time, and outputs the corresponding voltage or current to drive the motor for adjustment.

 

For example:

· If the motor speed is set to 1000 RPM and the encoder feedback is 950 RPM, the controller will automatically increase the output power to make the speed closer to the target.

· If the motor position deviates from the predetermined trajectory, the controller immediately corrects the motion path based on the encoder signal.

 

2. Hall sensor + encoder joint control solution

In many brushless motor systems, Hall sensors and encoders are often used in combination, each playing a different role:

· Hall sensor: Usually used to detect the position of the motor rotor for correct commutation at startup or low speed. It has fast response and low cost, but has low resolution.

· Encoders: Provide high-resolution speed and position information for fine control.

 

When used together, the system can start quickly and achieve high-precision control during operation. This combination is widely used in automatic guided vehicles (AGVs), CNC equipment, industrial robots and other fields.

3. Analysis of actual application scenarios of closed-loop control

Closed-loop control is not only a technical term, it directly affects system performance in specific applications. Here are a few typical examples:

a. Speed closed loop control

In applications such as wind turbines or high-speed centrifuges, the motor needs to maintain a constant speed. By feeding back the speed signal from the encoder, the controller can adjust the output in real time to offset the impact of load fluctuations.

 

b. Position closed loop control

In automated slides, lifting platforms, and industrial robotic arms, the motor needs to be precisely controlled to reach a specified position. The encoder feeds back the current position information to the controller to ensure that the movement process is smooth and stops accurately at the target position.

 

c. Angle closed loop control

In camera pan/tilts, laser rangefinders, or optical tracking devices, motors need to achieve precise rotation of angles. Closed-loop systems use encoders' high-resolution angle feedback to achieve precise control of tiny angles.

 

In traditional closed-loop control systems, motors, encoders, and controllers often need to be selected, installed, and debugged separately, which not only increases the engineering workload, but also brings problems such as complex wiring, signal interference, and matching incompatibility.

 

To address these challenges, VSD has launched the "Integrated Motor Module" solution, which integrates a brushless motor, encoder, and controller in a compact structure for plug-and-play use.

 

1. Motor + encoder + controller integrated design

VSD's integrated modules pre-assemble and factory-debug the core components of the control system, saving customers from complex on-site integration work. Each module is a strictly tested closed-loop system to ensure signal matching, interface compatibility and stable performance.

Benefits include:

· Shorten project development cycle

· Reduce maintenance costs

· Reduce system failure rate

 

2. Simplify wiring and debugging process

Traditional systems usually require multiple interfaces, connection cables and adapters, while the VSD module only needs a main power supply and a communication interface to complete the deployment of the entire closed-loop control. Preset parameters eliminate the need for customers to perform complex parameter adjustments in most applications.

 

This simplified design is very friendly to automation integrators, equipment manufacturers and OEM customers, and is particularly suitable for multi-machine deployment scenarios.

 

3. Flexible encoder configuration and interface options

VSD supports various types of encoder configurations to adapt to different control accuracy and environmental requirements:

· Encoder type: Incremental, absolute, photoelectric or magnetic

· Signal interface: support ABZ, UVW, SSI, RS-485, CANopen, etc.

· Installation: shaft end, hollow shaft and integrated encoder solutions are available

Customers can make choices based on actual applications, and VSD also provides customized interface development and adaptation services.

 

4. Wide range of application scenarios, supporting high-standard requirements

VSD's integrated motor modules have been widely used in:

· Industrial robots and collaborative robotic arms

· Medical imaging equipment and precision diagnostic platforms

· Intelligent conveying system and logistics automation equipment

· Aviation, UAV, optoelectronic tracking system and other fields

Each type of product can be configured and optimized according to different loads, speeds, accuracies and interface protocols to ensure the stability and efficiency of closed-loop control.

 

Closed-loop control systems are becoming standard for modern high-performance motor applications. By introducing encoders, brushless motors can achieve more precise speed regulation, more stable operation, and smarter response capabilities. Whether in industrial automation, robotic control, or in medical equipment or aviation systems, closed-loop control significantly improves the overall reliability and performance of the system.

 

As a professional brushless motor manufacturer , VSD (VSD Motor) continues to invest in closed-loop control solutions. We not only provide high-performance brushless motors , but also modularize encoders and controllers to provide customers with ready-to-use integrated solutions.

 

Why choose VSD

· High compatibility design: supports multiple encoder types and mainstream communication protocols

· Complete customization capability: everything from motor size, speed to feedback accuracy and interface layout can be customized

· Strict quality control system: in compliance with ISO, CE and other international certification standards

· Full-process technical support: Provide professional technical assistance and after-sales service from selection to delivery

· Global delivery experience: Products are exported to Europe, America, Japan, South Korea, the Middle East and other regions, and are widely used in projects in multiple industries

If you are looking for a stable, flexible and easy-to-integrate brushless motor closed-loop solution, please contact the VSD team. We can provide sample testing, technical consultation and batch customization services for your project.