Explanation of Sensors for Controlling Brushless Motors

In feedback control of brushless motors, sensors are used to detect the angle of rotation (rotational position). There are several types of sensors, each with different characteristics, so it’s important to choose the appropriate sensor to make full use of the motor's performance, depending on the application.
 
This article therefore describes the features of Hall ICs, resolvers and rotary encoders as typical sensors used to control brushless motors.

Sensors for Controlling Motors

1. Hall ICs

Hall ICs are magnetic sensors that incorporate a switching circuit for signal conversion in a Hall element, a semiconductor element that uses the galvanomagnetic effect known as the Hall effect. Since semiconductors are used, Hall ICs do not have high resistance to heat or vibration, but their advantage is that they are relatively inexpensive.

Mabuchi Motor products with Hall ICs include the ‘IS Series’ and ‘MS series.’

2. Resolver

Resolvers are sensors that use two coils to detect the angle of rotation of the rotor. They have a simple, robust construction with only an iron core and coils, making them resistant to heat, oil and vibration, and less susceptible to electrical noise. Although more expensive than Hall ICs, they have a higher angular resolution and enable precise speed control with less rotational irregularities.

Mabuchi Motor offers the ‘IR /MR Series’, which is equipped with a resolver with a resolution equivalent to 15 bits.

3. Rotary Encoder

There are three main types of rotary encoder used to control brushless motors: optical, magnetic and capacitive, each with different characteristics.

The optical type has a complex internal board structure and is vulnerable to harsh operating environments such as high temperatures and vibrations, but it is capable of highly accurate angle detection.
The magnetic type has a lower resolution than the optical type and cannot be used in strong magnetic fields, but is less expensive and more resistant to high temperatures and vibrations.
Capacitive systems are more expensive than the other two types but have very high resolution and are more resistant to use in harsh environments such as strong magnetic fields.

*Resistance to vibration, shock, moisture, oil, dirt and other harsh environmental conditions.

As each has different areas of expertise, which sensor is appropriate depends on the situation in which it is used.

About the Sensors in Mabuchi Motor's Brushless Motors for Mobility Applications

Mabuchi Motor's brushless motors for mobile vehicles feature the‘ IS Series ‘ and ‘ MS Series’, which are equipped with Hall ICs, and the‘ IR/MR Series ’with high-resolution resolvers.
 
Recently, AGVs and AMRs have been introduced in factories and other production sites, and electric wheelchairs and automated guided vehicles are increasingly used outdoors, so the requirements of motors are increasing with the evolution of mobility applications.
 
Resolvers have a higher angular resolution than Hall ICs and can achieve precise speed control from zero rotation, preventing the motor from going off course, for example. In addition, the motor itself is waterproof and resistant to heat, oil, dust and vibration, making it an ideal choice for mobility applications where both precise control and environmental resistance are required.
 
If the application is used in a harsh environment or does not require precise control and the required functions can be fulfilled by Hall ICs, we recommend the IS/MS series, which are more affordable than the IR/MR series.
 
Please feel free to contact us for the most suitable product for your application.

Summary

This article has described the following sensors used to control brushless motors.

•  Types of Sensors for Controlling Motors and their Features
• About the Sensors used in Mabuchi Motor's Brushless Motors for Mobility Applications

In the feedback control of brushless motors, sensors are used to detect the angle of rotation (rotational position), and there are several types of sensors for this purpose. Each has different features, and it is important to select the appropriate sensor to make full use of the motor's performance according to the application.
 
Mabuchi Motor offers the ‘ IS Series ‘ and 'MS Series ’ with Hall ICs and the ‘IR/MR Series ’ with high-resolution resolvers.
 
 
If you are interested in our products, please feel free to contact us.

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