Gear Tooth Sensor for Pedal Cycle Motor Control
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Solution Overview
Problem
Existing electrically assisted pedal cycle systems face challenges in accurately sensing pedaling speed and direction due to the need for specialized targets and sensors, which are difficult to fit and align on various pedal cycle configurations, leading to variable power assistance and non-compliance with international standards.
Innovation Solution
An electrically assisted cycle kit that uses a gear tooth sensor, comprising a magnetic sensor for sensing ferrous gear teeth of the rear sprocket, to provide a gear motion signal indicative of speed and acceleration, allowing the controller to regulate the electric motor's drive without the need for additional sensors, simplifying installation and improving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If specialized sensors and target devices are used to sense pedaling speed and direction, then measurement precision is improved, but device complexity and ease of operation deteriorate due to difficult fitting and alignment requirements
Solution Approach 1:
The existing rear sprocket of the pedal cycle serves as the sensing target itself, eliminating the need for separate target devices. The gear tooth sensor detects teeth and valleys on the sprocket, allowing the sprocket to 'serve itself' as both the mechanical transmission component and the sensing target, thereby reducing overall system complexity while maintaining measurement precision
Solution Approach 2:
The gear tooth sensor serves multiple functions: it detects pedaling speed, determines direction of rotation, and eliminates the need for separate brake sensors by detecting when the cyclist stops pedaling. This multi-functionality reduces the number of components needed while improving measurement capabilities
2Measurement precision
If torque sensors are used to provide accurate power assistance, then measurement precision is improved, but ease of manufacture and ease of operation worsen due to difficulty of retro-fitting
Solution Approach 1:
The system uses the existing rear sprocket as the sensing target, eliminating the need for specialized target devices that are difficult to fit. The gear tooth sensor works with the sprocket that is already part of the bike's drivetrain, making retro-fitting straightforward while providing accurate speed and direction sensing for power assistance control
Solution Approach 2:
The patent replaces complex torque sensors with a simpler gear tooth sensor system that uses magnetic sensing of gear teeth. This substitution maintains measurement precision for power assistance control while dramatically simplifying the retro-fitting process, as the sensor can be mounted near the existing sprocket without modifying the bike's mechanical structure
3Reliability
If multiple sensors and target devices are installed to comply with international standards, then reliability is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The gear tooth sensor provides multiple sensing functions in a single device: it detects pedaling speed for motor control, determines direction of rotation for safe operation, and detects when pedaling stops to trigger brake activation. This multi-functionality ensures compliance with international standards while simplifying installation to a single sensor rather than multiple separate sensors
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The gear tooth sensor enables precise detection of pedaling speed and direction, enhancing the responsiveness and reliability of motor assistance, reducing the number of components needed, and eliminating the requirement for separate brake sensors, thus simplifying the fitting process and improving compliance with international standards.
Implementation Method 1
the gear tooth sensor comprises a magnetic sensor for sensing ferrous gear teeth of the rear sprocket
Data Source
AI summary
An electrically assisted cycle kit (50) for fitting to a pedal cycle (2) comprises an electric motor (58) for assisting pedal cycle motion, a battery (52) for powering the motor (58), and a controller (60) for controlling the drive of the motor (58). A gear tooth sensor (65) provides a gear motion signal indicative of the speed/acceleration of motion of gear teeth (94) and valleys (95) of a gear sprocket (32) of the cycle. The controller controls the drive of the motor (58) in dependence on the gear motion signal.