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How Do Electric Bike Torque Sensors Work?

An electric bike torque sensor, also known as a force sensor or rotational torque sensor, is a device that measures the magnitude of applied torque by detecting changes in physical torque and converting them into understandable output signals.

Primary Function

The primary function of an electric bike torque sensor is to control the electric assist system. When a rider pedals, the crank generates torque, causing deformation of the elastic element within the sensor. The deformation is proportional to the torque, and by measuring the deformation, the torque magnitude can be determined.

Types of Electric Bike Torque Sensors

There are three primary types of electric bike torque sensors:

Rear Axle Hook Sensor: Mounted on the rear axle hook, this sensor measures the torque on the rear axle to reflect the rider’s pedaling force. It offers a simple structure and low cost but has lower accuracy and is sensitive to road conditions.
Bottom Bracket Torque Sensor: Mounted on the bottom bracket, this sensor measures the torque on the bottom bracket to reflect the rider’s pedaling force. It offers higher accuracy and is unaffected by road conditions but has a more complex structure and higher cost.
Pedal Torque Sensor: Mounted on the pedals, this sensor measures the torque on the pedals to reflect the rider’s pedaling force. It offers the highest accuracy and is unaffected by road conditions but has the most complex structure and highest cost.

Structure of an Electric Bike Torque Sensor

The structure of an electric bike torque sensor consists of the following main components:

Housing: Protects the internal components of the sensor.
Elastic Element: Detects the deformation caused by torque. The elastic element can be a spring, diaphragm, strain gauge, or similar component.
Magnetoresistance Sensor: Measures the deformation of the elastic element. The magnetoresistance sensor can be a Hall effect sensor, magnetoimpedance sensor, or similar component.
Signal Processing Circuit: Converts the output signal from the magnetoresistance sensor into a standard output signal.

Working Principle

When a rider pedals, the crank generates torque, causing deformation of the elastic element within the sensor. The deformation of the elastic element is proportional to the torque. The magnetoresistance sensor outputs a corresponding electrical signal based on the deformation of the elastic element. The signal processing circuit converts the electrical signal from the magnetoresistance sensor into a standard output signal and sends it to the electric assist control system.

Electric Assist Control System

The electric assist control system adjusts the motor’s power based on the signal from the torque sensor, providing the rider with appropriate assistance.

Conclusion

Electric bike torque sensors play a crucial role in enhancing the riding experience by providing a natural and responsive pedal assist. The choice of torque sensor depends on factors such as accuracy, cost, and desired performance characteristics.