Blog

Home > Blog

Table of Contents

Servo Hub Motor VS. Brushless Hub Motor

Introduction

In the development of modern electric vehicles, hub motors are gaining widespread attention. Their unique integrated structure, distributed power output, and high-efficiency transmission make hub motors highly advantageous for electric bicycles, electric cars, and other urban transportation tools.

This article will provide a comprehensive introduction to the two most common types of hub motors on the market today: brushless hub motors and servo hub motors. By understanding the structure and features of these two types of motors, readers can make informed decisions when choosing the right motor for their devices.

Understanding Hub Motor

What is a hub Motor?

Hub motor is an innovative technology that integrates the motor into the wheel axle. There are three advantage of hub motor include:

Integrated Structure

Hub motors feature an integrated structure where the rotor, controller, and other components are compactly installed within the wheel. This design makes the motor and wheel a single unit, saving space and reducing the complexity of the transmission system.

Distributed Power Output

Each wheel equipped with an independent hub motor enables distributed power output. This means that each wheel can provide direct power, enhancing the vehicle’s handling, stability, and flexibility.

High-Efficiency Transmission

Since the motor is directly connected to the wheel, energy loss in the transmission system is minimized, improving energy efficiency. Additionally, the absence of traditional drive shafts and gear transmissions reduces mechanical friction losses, optimizing the overall vehicle design. The use of hub motors also saves space in the vehicle chassis, maximizing load space.

Servo Hub Motor vs Brushless Hub Motor

Servo hub motors and brushless hub motors are often difficult to distinguish by appearance alone. Unless you are a professional motor manufacturer, it can be challenging to tell these two types of motors apart just by looking at them.

Despite both being categorized as hub motors, there are significant differences in their structure, functionality, and applications. Below is a detailed comparison of these two types of motors: 

1.Structure and design

Servo hub motors integrate a brushless DC motor, encoder, Hall sensors, and the wheel into a single unit, serving as both a servo motor and a driving wheel. However, they typically lack an internal gearbox, limiting their load capacity to around 200KG.

The standout feature of servo hub motor is its built-in encoder and Hall sensors, which enhance motor control precision, enabling excellent synchronization and precise linear movement.

Brushless hub motors integrate a brushless DC motor, Hall sensors, and the wheel into the hub. Some models even include an internal planetary gearbox, typically with a 4:1 or 7:1 gear ratio. This integration eliminates the need for couplings, external gearboxes, and differentials in electric vehicle design.

Although BLDC hub motors only include Hall sensors and lack encoders, resulting in lower precision, their design significantly simplifies the structure of electric vehicles. The compact design saves space and reduces the overall weight of the vehicle, enhancing space utilization and efficiency.

For those who are not professional motor manufacturers or users, it is challenging to differentiate between servo hub motors and brushless hub motors based on their appearance alone, let alone understand the specific internal structural differences.

However, you can distinguish between these two types of motors by examining their output wires:

Brushless Hub Motors: Typically have 8 wires:

3 power wires (U, V, W)

5 Hall sensor wires

Servo Hub Motors: Typically have 13 wires:

3 power wires (U, V, W)

10 encoder signal wires

By counting and identifying the wires, you can determine the type of motor you are dealing with.

2.Control way

Servo Hub Motors come equipped with built-in encoders and are paired with DC servo drivers, offering several key advantages on the control side:

A.High Control Precision:

Enables excellent synchronization and linear movement capabilities.

B.Constant Torque Control:

Due to the servo drive’s characteristic of constant torque speed regulation, the motor maintains normal torque even at low speeds.

C.Communication Support:

Supports RS232/RS485/Can bus communication.

The specific communication protocols supported may vary between manufacturers, so it is essential to confirm details with the servo hub drive manufacturer in advance.

Brushless Hub Motors are equipped with Hall sensors and are paired with standard brushless drivers. The control side has the following characteristics:

A.Low Control Precision:

Synchronization and linear movement control are more challenging to achieve.

B.Torque Decay at Low Speeds:

Due to the nature of brushless motors, torque decreases as speed is reduced from the rated speed. This results in lower torque at low speeds, which may not be sufficient to drive the normal load.

C.Cost-Effective Drivers:

The drivers for these motors are typically very affordable and may lack communication functions.

These drivers can generally meet the basic needs of budget electric vehicles. It is advisable to confirm specific requirements with the hub motor supplier when selecting a model.

3.Application

Servo Hub Motor Application:

A.Intelligent robot

Due to their compact size and support for high precision and synchronized control, Servo Hub Motors are the ideal choice for various types of robots, including:

  • Food Delivery Robots
  • Hotel Service Robots
  • Unmanned Delivery Robots
  • Cleaning Robots
  • Disinfection Robots
  • Inspection Robots

Key Advantages:

High Precision Navigation:

Allows robots to navigate accurately according to predefined paths and maps, ensuring tasks such as cleaning, item transport, and information delivery are performed without deviating from the track.

Obstacle Avoidance:

Servo hub motors are excellent for implementing obstacle avoidance functions, ensuring the safety of surrounding people.

These features make servo hub motors a preferred choice in robotic applications where precision, safety, and reliability are paramount.

B.AGV(Automated Guided Vehicle)

Servo Hub Motors are widely used in commercial AGVs (Automated Guided Vehicles), industrial AGVs, and AMRs (Autonomous Mobile Robots). These devices typically employ various navigation technologies such as: QR Code Navigation, Laser Navigation, Visual Navigation, Inertial Navigation. And servo hub motors provide the necessary travel and power support.

Due to the absence of an internal reducer, the torque output of the wheels is limited. Consequently, these motors are suitable for light-duty AGVs with loads ranging from 200 to 300 kg.

However, some hub motor manufacturers are willing to customize servo hub motors with built-in reducers for users if the product quantity is sufficient.

To be summary, Servo hub motors are widely used in light-duty robots like food delivery robots, cleaning robots, and AGVs due to their high precision, large torque, high inertia, low noise, and smooth operation.

Compared to the traditional “servo motor + reducer + wheel + tire” setup, servo hub motors offer a higher cost-performance ratio. With the rapid growth of industrialization and automation, the application fields of servo hub motors are expected to expand further.

Brushless Hub Motor Application:

A.Electric Bicycles and Electric Motorcycles
Brushless hub motors are primarily used in electric bicycles and electric motorcycles. Their characteristics and advantages make them a key technology in these fields.

Key Advantages:

High efficiency and energy-saving

allow these electric vehicles to achieve longer range and better power performance.

Integration

brushless hub motors integrate power, transmission, and braking within the hub, the structure of electric bicycles and electric motorcycles becomes more compact and aesthetically pleasing.

B.Electric Balance Scooters and Electric Scooters
Brushless hub motors also play an important role in short-distance travel tools such as electric balance scooters and electric scooters. Their high-precision control and flexible driving characteristics enable these tools to achieve smoother and safer rides.

Overall, brushless hub motors, with their advantages of high efficiency, energy-saving, integration, lightweight, and flexible driving, are widely used in electric bicycles, electric motorcycles, electric balance scooters, and electric scooters. With continuous technological advancements and growing market demand, the application fields of BLDC hub motors will further expand.

4.Common Sizes

Servo Hub Motors: Common wheel diameters are 4.5″, 5.5″, 6.5″, 8″, 10″, 12″, without a gearbox. Other wheel sizes may require custom motors and wheels.

Brushless Hub Motors: Common wheel diameters are 6″, 8″, 9.5″, 10″, 12″, 13″, 14″, 16″, 18″, 20″, mostly with built-in gearboxes. More tire outer diameter sizes can be selected. 

If you have special wheel size requirements, you can try to confirm with the hub motor manufacturer if customization is possible.

5.Price

Due to the high precision and constant torque speed regulation performance of servo hub motors, their price is usually more than double that of brushless servo hub motors. The main price difference lies in the driver. You can choose the appropriate hub motor for your equipment based on your motor performance requirements and terminal product pricing.

New Favorite in the AGV Market: Built-in Planetary Drive Wheels

It is worth mentioning that to compensate for the lack of built-in gearboxes in DC servo hub motors, which makes them unsuitable for heavy-duty AGV equipment, there is now a type of drive wheel on the market that looks similar to a servo hub motor. It assembles a standard DC servo motor through a flange connection method into a hub with a built-in precision planetary gearbox.

This built-in precision planetary gearbox offers multiple reduction ratios and can withstand large torques, significantly increasing the load torque. However, its price is relatively higher than that of ordinary servo hubs without gearboxes. The application range is basically the same as that of servo hub motors. For AGVs and robots with high precision requirements and intelligent automatic control, it has a natural advantage.

Table 1. Comparison of Servo Hub Motor vs. Brushless Hub Motor

FeatureBrushless Hub MotorsServo Hub Motors
Feedback ComponentsNo feedback componentsEquipped with feedback components (e.g., encoders)
Design and StructureSimple, integrated designComplex design with high precision components
ApplicationElectric bikes, electric motorcycles, scooters, etc.Robots, AGVs, high-precision control applications
Control MethodsSimple control, less precision requiredAdvanced control, high precision required
PriceRelatively lowHigher due to precision and control capabilities
Common Sizes6″, 8″, 9.5″, 10″, 12″, 13″, 14″, 16″, 18″, 20″4.5″, 5.5″, 6.5″, 8″, 10″, 12″
Torque CapabilitySuitable for moderate torque applicationsSuitable for high torque applications

Conclusion

Brushless hub motor and servo hub motor are both advanced motor technologies with distinct differences in feedback components, design, application scenarios, and control methods.

Brushless Hub Motors: Known for their low cost, low noise, and high reliability. Ideal for applications requiring rapid acceleration and simple operation, such as electric bicycles and motorcycles.

Servo Hub Motors: Offer high precision, constant torque speed regulation, and reliable motion control. Essential for high-precision applications like food delivery robots, hotel service robots, and unmanned delivery robots.

As technology evolves, both motor types will see broader applications and further optimization. We anticipate their growing impact on industrial automation and intelligent manufacturing.

In summary, understanding the differences in structure, control methods, and application scenarios will help you choose the right motor for your needs. At the same time, we also look forward to continuous innovation and progress in these two motor technologies, bringing more convenience and benefits to society.

Latest Post
Hey,I‘m Jack.

Because of my work, my customers may know more about how to choose suitable motor power solution for their application. lf you have any questions about this, please feel free to contact with me!

Contact Us Anytime

Send Us Your Comment

Contact for Faster Size Drawing