Shaft Twist Torque Sensing for High-Frequency Feedback
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Solution Overview
Problem
Existing torque sensors in force feedback systems for exercise apparatuses struggle to provide high signal-to-noise ratio and high-frequency feedback across a wide range of rotation speeds at an acceptable cost, failing to accurately simulate real-life experiences due to limitations in sensor data processing and measurement frequency.
Innovation Solution
A torque sensing system with a rotatable shaft having a spring structure and readout structures with position indicators, utilizing a detector system and processor to determine angular positions and twist angles based on passing times of indicators, enabling high-frequency feedback without requiring absolute angular encoders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior art torque sensors use encoder wheels with limited readout elements, then the device complexity is reduced, but the measurement precision and sampling frequency are insufficient for high-frequency feedback requirements
Solution Approach 1:
The patent replaces the mechanical encoder wheel system with a magnetic field-based sensing system. Magnets are arranged in a circular pattern on a rotor, and stationary magnetic sensors detect the magnetic field variations as the rotor turns. This substitution eliminates the need for complex mechanical encoder structures while enabling higher measurement precision and sampling frequencies suitable for real-time torque feedback applications.
2Productivity
If the number of readout elements is increased to achieve higher sampling frequency, then the measurement frequency improves, but the device complexity and manufacturing cost increase substantially
Solution Approach 1:
The magnetic sensors serve multiple functions: they detect both the position and speed of the rotor, and from these measurements, torque is calculated. This multi-functionality allows the system to achieve high sampling frequencies without proportionally increasing the number of sensors or readout elements, as each sensor provides rich information for multiple measurement purposes.
Solution Approach 2:
The patent changes the fundamental measurement parameter from optical reflection intensity (in encoder wheels) to magnetic field strength variations. This parameter change enables continuous high-frequency sampling because magnetic field detection is not limited by the discrete number of encoder marks, allowing the system to achieve high productivity without increasing structural complexity.
3Reliability
If optical sensors are used to detect position changes, then the measurement capability is provided, but the signal-to-noise ratio is poor due to sensitivity to noise and limited sample frequency
Solution Approach 1:
The patent substitutes optical sensing with magnetic sensing. Magnetic sensors detect variations in magnetic field strength caused by the rotating magnets, providing a signal that is inherently more robust to noise. The magnetic field variations directly correlate with rotor position and speed, enabling accurate torque calculation with high signal-to-noise ratio and without the limitations of optical signal reflection methods.
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
The system achieves accurate torque measurement and feedback across varying rotation speeds, enhancing the realism of exercise experiences by providing precise resistive forces in response to user input.
Implementation Method 1
the shaft comprising a spring structure between the first and second part
Data Source
AI summary
This disclosure relates to a torque sensing system. The torque sensing system comprises a rotatable shaft having a first part and a second part, the shaft comprising a spring structure between the first and second part; a first readout structure connected to the first part, the first readout structure comprising first position indicators, and a second readout structure connected to the second part, the second readout structure comprising second position indicators; a detector system for detecting the first and second position indicators and generating a first detection signal indicating respective passing times for the first position indicators and a second detection signal indicating respective passing times for the second position indicators; and a processor. The processor is configured for determining an angular position of the first readout structure occurring at a particular time instance based on a detected passing time of at least one first position indicator on the first readout structure and on a first relation between angular position of the first readout structure and time around said particular time instance; and determining an angular position of the second readout structure occurring at the particular time instance based on a detected passing time of at least one second position indicator on the second readout structure and optionally based on a second relation between angular position of the second readout structure and time around said particular time instance; and, determining an angle of twist at the particular time instance based on the angular position of the first readout structure and the angular position of the second readout structure, the angle of twist being associated with a torque applied to the first and/or second part of the rotatable shaft.