Bicycle Pedaling Torque Sensing via Bearing Support Beams
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Solution Overview
Problem
Electric bicycles in pedal assist mode require efficient sensing of rider pedaling torque to optimize motor control, as existing systems struggle to distinguish between pedaling force and other forces like motor torque and rider standing on the pedals, leading to inefficient motor activation and deactivation.
Innovation Solution
The implementation of a pedaling force sensing system using beams with strain gauges positioned around a bearing support member, which detects strain caused by rider pedaling torque, allowing the motor controller to determine the appropriate motor output based on sensed torque values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are positioned on beams supporting the bearing, then torque sensing accuracy is improved, but device complexity increases
Solution Approach 1:
The bearing support member is merged with the beam structure, integrating the support function and the strain sensing function into a single component. The beams that structurally support the bearing also serve as the mounting substrate for strain gauges, eliminating the need for separate sensing elements and reducing overall device complexity while maintaining measurement precision.
Solution Approach 2:
The beam structure serves multiple functions: it provides structural support for the bearing, acts as a strain transmission element from the pedal input, and serves as the mounting platform for strain gauges. This multi-functionality reduces the number of separate components needed in the system.
2Reliability
If multiple strain gauges are used on multiple beams, then torque sensing reliability is improved, but manufacturing cost increases
Solution Approach 1:
The torque sensing function is segmented across multiple beams and strain gauges distributed around the bearing perimeter. This segmentation provides redundancy and improves reliability through multiple measurement points, while each individual gauge remains a standard, easily manufactured component.
Solution Approach 2:
Multiple strain gauges provide feedback from different locations on the bearing support structure, allowing the controller to cross-validate measurements and improve torque sensing reliability. The controller can process signals from multiple gauges to compensate for individual gauge variations or failures.
3Use of energy by moving object
If the motor is activated and deactivated seamlessly based on pedaling torque, then energy efficiency is improved, but control system complexity increases
Solution Approach 1:
The strain gauges provide continuous feedback on pedaling torque to the motor controller, enabling seamless activation and deactivation of the motor based on actual rider input. The controller adjusts motor assistance in real-time based on the torque feedback, optimizing energy efficiency while maintaining smooth operation.
Solution Approach 2:
The motor control system dynamically adjusts its operation based on real-time torque sensing. The motor transitions smoothly between active and inactive states based on the pedaling torque threshold, creating a dynamic control system that adapts to rider needs while improving energy efficiency.
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
This solution enables seamless and efficient motor control in conjunction with rider pedaling, improving torque sensing accuracy, efficiency, and reducing weight and heat, while allowing for invisible activation and deactivation of the motor.
Implementation Method 1
one or more strain gauges can be coupled to one or more surfaces of the beams to detect such strain
Data Source
AI summary
A device for sensing a bicycle pedaling torque input includes: a housing; a bearing defining a rotational axis; a bearing support member that positions the bearing with respect to the housing, the bearing support member including one or more beams; an output member configured to be coupled to a chain ring, the output member being coupled to an inner race of the bearing to enable the output member to rotate with respect to the housing about the rotational axis; a spindle configured to be coupled to a bicycle pedal crank, the spindle functionally coupled to the output member to enable a rider pedaling force applied to the spindle to cause rotation of the output member; and one or more strain gauges, each of the one or more strain gauges being coupled a beam of the bearing support member.