Bicycle Crank Strain Sensor for Power Direction Measurement
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Solution Overview
Problem
Existing measurement technologies for man-powered machines, such as bicycles, cannot accurately present the direction and strength of power applied according to the crank angle, limiting user efficiency and pedaling technique improvement.
Innovation Solution
A measurement apparatus and method that includes a strain detecting part, a sensor for detecting the crank passing through a predetermined position, and a control part to calculate the rotation angle and force distribution based on strain data, allowing for the display of power direction and strength at specific crank angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque is detected by a magnetostrictor and crank angle is detected by an optical sensor, then power and calories-out can be calculated and displayed, but it is not possible to present the direction and strength of power according to a crank angle
Solution Approach 1:
The patent segments the power measurement into two independent components: torque magnitude (detected by magnetostrictor) and power direction (detected by strain gauges on the crank). This segmentation allows each component to be measured separately and then combined, resolving the contradiction by preserving directional information that was previously lost in the integrated measurement approach
Solution Approach 2:
The patent introduces strain gauges as an intermediary measurement device on the crank to detect the direction of power application. This intermediary sensor captures the directional component (pedaling technique information) that bridges the gap between simple torque measurement and comprehensive power analysis, enabling presentation of power direction according to crank angle
2Loss of information
If strain detecting part and sensor are added to detect crank position and strain, then power direction and strength can be presented according to crank angle, but device complexity increases
Solution Approach 1:
The control part serves multiple functions: it processes data from both the magnetostrictor and strain gauges, calculates torque magnitude, determines power direction, and presents the combined information according to crank angle. This multi-functionality consolidates what would otherwise require separate processing systems, reducing overall device complexity while achieving comprehensive power measurement
Solution Approach 2:
The patent merges the torque detection system (magnetostrictor) with the directional detection system (strain gauges) into a unified measurement apparatus. By combining these detection methods and processing them together in the control part, the system achieves comprehensive power measurement without requiring entirely separate systems, thereby managing complexity
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
Enables users to visualize and improve their pedaling technique by providing detailed information on power direction and wasted force at each crank angle, enhancing pedaling efficiency.
Implementation Method 1
a strain detecting part that detects strain of a crank
Implementation Method 2
detecting torque by a magnetostrictor
Data Source
AI summary
A measurement module that measures force being applied to a man-powered machine includes: a strain sensor that detects strain of a crank of the bicycle configured to transmit force being applied from a user through the crank and one front gear selected among one or more front gears; an MM magnetic sensor that detects the crank passing through a predetermined position; and an MM control part. The MM control part calculates a rotation angle of the crank based on an elapsed time from a time the crank passes through the predetermined position that the sensor has detected, calculates force applied to the crank based on a strain amount of the crank that the strain sensor has detected, associates the rotation angle with the force applied to the crank to calculate distribution of the force applied from the user.