External Force Measurement Unit for Electric Bicycles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional external force measurement systems for electrically assisted bicycles primarily focus on measuring torque applied by the rider through pedal cranks, neglecting vertical forces and horizontal forces, such as those from the bicycle chain, which simplifies the measurement but reduces accuracy.
Innovation Solution
An external force measurement unit with a load cell featuring a support ring with radial flaps and strain gauges that measure vertical forces separately, using an evaluation unit to convert these forces into measurement values, and an angular encoder to determine the spindle's position, allowing for precise calculation of additional power or torque provided by the electric motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional torque measurement through pedal cranks is used, then device complexity is reduced, but measurement precision deteriorates due to neglecting vertical and horizontal forces
Solution Approach 1:
The measurement system is segmented into multiple independent measurement components: a load cell for vertical forces, strain gauges for additional measurements, and an angular encoder for position detection. Each component measures a specific aspect of the external force, and their results are combined to achieve comprehensive and precise measurement while keeping each individual component relatively simple.
2Measurement precision
If vertical forces are measured separately using strain gauges on flaps, then measurement precision improves, but device complexity increases due to additional sensors and evaluation requirements
Solution Approach 1:
The patent combines multiple measurement functions into a single integrated load cell structure. The load cell incorporates both the vertical force measurement capability and the strain gauge arrangement on radial flaps, merging what would otherwise be separate measurement devices into one unified component that reduces overall system complexity.
Solution Approach 2:
The load cell is designed as a multi-functional device that can simultaneously measure vertical forces through the main sensing element and additional forces through the strain gauges on the radial flaps. This universal measurement capability allows a single device to perform multiple measurement tasks, reducing the need for separate specialized sensors.
3Device complexity
If horizontal forces from the bicycle chain are excluded from measurement, then device complexity is reduced, but measurement precision deteriorates as external force measurement becomes incomplete
Solution Approach 1:
The patent introduces an intermediary measurement approach where the load cell and strain gauges indirectly capture horizontal forces from the bicycle chain through their mechanical coupling to the spindle. Rather than directly measuring chain forces, the system uses the load cell as an intermediary that translates various force components (including horizontal forces) into measurable vertical displacements and strain changes.
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 provides a more accurate measurement of external forces applied to the spindle, including vertical and horizontal components, enabling improved power assistance and enhanced precision in torque calculation, leading to better performance and control of electric bicycles.
Implementation Method 1
A first strain gauge is arranged on the first flap and a second strain gauge is arranged on the second flap. The first strain gauge and/or the second strain gauge will change their respective resistances, depending on a change of length of the first flap and/or the second flap when the flaps are compressed or expanded by forces on the spindle.
Implementation Method 2
The first strain gauge and/or the second strain gauge will change their respective resistances, depending on a change of length of the first flap and/or the second flap when the flaps are compressed or expanded by forces on the spindle.
Data Source
AI summary
The external force measurement unit comprises a load cell with a support ring, wherein a first flap and a second flap are arranged on the support ring, wherein the second flap is arranged opposite to the first flap on the support ring, wherein each flap is arranged in a radial direction to the outside of the outer ring, and a first flap end and a second flap end being arranged at respective ends of the first flap and the second flap. A second aspect concerns a measuring method for measuring an external force with an external force measurement unit comprising a load cell, which receives a spindle. A third aspect concerns an electrically assisted bicycle comprising an external force measurement unit.