Dynamic Gain Control for Bicycle Torque Measurement
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Solution Overview
Problem
Existing bicycle power meter control apparatuses require high-precision A/D converters to accurately measure pedal depression force, which increases manufacturing costs and is susceptible to signal noise due to high quantization bit rates.
Innovation Solution
A bicycle-use measuring apparatus with a sensor, signal amplifying section, and gain control section that adjusts the gain based on the rotational state of the bicycle, allowing for accurate measurement without a high-precision A/D converter by matching the amplified voltage range to the A/D converter's dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-precision A/D converter with large quantization bit rate is used, then measurement precision of the sensor output is improved, but the device becomes more susceptible to signal noise and manufacturing cost increases
Solution Approach 1:
The patent applies dynamic gain adjustment in the signal amplifying section based on detected signal levels. The gain is automatically increased when signal levels are low and decreased when signal levels are high, optimizing the signal-to-noise ratio across varying pedal depression forces without requiring a high-precision A/D converter
Solution Approach 2:
The patent changes the amplification parameter (gain) of the signal amplifying section based on the detected signal characteristics. By adjusting the gain parameter dynamically, the system achieves accurate measurement of both small and large sensor outputs while maintaining immunity to noise and reducing A/D converter precision requirements
2Measurement precision
If a high-precision A/D converter with large quantization bit rate is used, then measurement precision of the sensor output is improved, but manufacturing cost increases
Solution Approach 1:
The system uses dynamic gain adjustment to adapt to varying signal levels, allowing the use of a lower-precision, more cost-effective A/D converter while maintaining measurement accuracy across the full range of pedal depression forces
Solution Approach 2:
The patent replaces the expensive high-precision A/D converter with a combination of dynamic signal amplification and a standard-precision A/D converter, achieving the same measurement accuracy at lower cost
3Device complexity
If the gain of the signal amplifying section is fixed, then device complexity is reduced, but measurement accuracy deteriorates when pedal depression force is small
Solution Approach 1:
The patent introduces dynamic gain adjustment based on detected signal characteristics, allowing the system to automatically optimize amplification for both small and large pedal depression forces without significantly increasing device complexity
Solution Approach 2:
The system uses feedback from the detected signal level to automatically adjust the gain of the signal amplifying section, ensuring optimal measurement accuracy across varying operating conditions while maintaining a relatively simple overall device structure
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
Reduces the need for high-precision A/D converters, decreases noise effects, and lowers manufacturing costs while maintaining accurate torque measurement across varying cadences.
Implementation Method 1
The strain gauge 52 measures a strain of the crankshaft occurring when a rider depresses a pedal
Implementation Method 2
The amplifier 53 amplifies an analog electric signal outputted from the strain gauge 52
Data Source
AI summary
A bicycle-use measuring apparatus includes a sensor, a signal amplifying section and a gain control section. The sensor is configured to be installed on a bicycle having a rotating part. The signal amplifying section amplifies an output of the sensor. The gain control section adjusts a gain of the signal amplifying section in accordance with changes in a rotational state of the rotating part.