Crank Spindle Torque Sensing With Left-Right Pedal Differentiation
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Solution Overview
Problem
Existing torque sensors in vehicles propelled by muscle and motor power, such as e-bikes, fail to distinguish between torques generated by the left and right foot due to mechanical superposition, losing information about the source of the torque.
Innovation Solution
A crank spindle set-up with magnetic regions on the crank spindle and output shaft, generating and outputting magnetic fields based on mechanical stress, allowing a sensor to detect and differentiate between left and right torques through magnetic field superposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque sensor is used to measure torque transmitted to the output shaft, then torque detection is enabled, but information about the source of torque (left or right foot) is lost due to mechanical superposition
Solution Approach 1:
The patent divides the torque measurement function into two separate measurement paths: one for left foot torque and one for right foot torque. Each crank arm has its own magnetic region and the sensor setup can distinguish between torques from different sides, preventing information loss through segmentation of the measurement function.
Solution Approach 2:
The patent introduces magnetic fields as an intermediary medium between the mechanical torque and the sensor detection. Magnetic regions are generated on the crank spindle and output shaft, creating magnetic field superposition that the sensor can detect and evaluate to determine the source of torque, thus preserving left/right information.
2Loss of information
If magnetic regions are added to both the crank spindle and output shaft, then left/right torque information can be detected, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the magnetic field system: the same magnetic regions serve both for torque transmission indication and for left/right differentiation. The magnetic field superposition principle allows one sensor setup to extract multiple pieces of information (total torque and directional torque) from the same magnetic field interactions, reducing overall system complexity.
Solution Approach 2:
The magnetic regions on the crank spindle and output shaft serve multiple purposes: they transmit torque information, generate detectable magnetic fields, and enable directional differentiation. This multi-functionality reduces the need for separate components for each function, thereby managing device complexity while achieving information preservation.
3Loss of information
If the second magnetic region is positioned at an axial spatial distance from the tap, then left/right torque differentiation is enabled, but mechanical coupling efficiency may be affected
Solution Approach 1:
The patent applies magnetic regions at specific local positions: the first magnetic region is on the output shaft near the mechanical coupling tap, while the second magnetic region is on the crank spindle at an axial distance from the tap. This local differentiation in positioning allows the magnetic fields to interact in a way that preserves left/right information while maintaining mechanical coupling integrity through the tap.
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 reliable detection of left and right torques, facilitating improved control and training adjustments, such as differentiated motor assistance, by using a sensor system that superposes magnetic fields to determine the source of torque.
Implementation Method 1
with a first magnetic region on and/or in the output shaft for generating and outputting a first magnetic field that is a function of the state of mechanical stress of the output shaft
Implementation Method 2
with a second magnetic region on and/or in the crank spindle at an axial spatial distance from the tap of the mechanical coupling, for generating and outputting a second magnetic field that is a function of the state of mechanical stress of the crank spindle
Implementation Method 3
with a sensor set-up for detecting a magnetic field outputted by the crank spindle set-up
Data Source
AI summary
A crank spindle set-up for a vehicle. The set-up includes a crank spindle for receiving a force/torque from pedaling using crank arms attached to ends of the crank spindle; an output shaft for receiving a force and/or a torque from the crank spindle; a mechanical coupling having a tap between the ends of the crank spindle, for transmitting force/torque from the crank spindle to the output shaft; a first magnetic region on/in the output shaft for generating and outputting a first magnetic field that is a function of the state of mechanical stress of the output shaft; a second magnetic region on/in the crank spindle at an axial distance from the tap, for generating and outputting a second magnetic field that is a function of the state of mechanical stress of the crank spindle; and a sensor set-up for detecting a magnetic field outputted by the crank spindle set-up.