Signal Processing Device for Stretchable Sensor Lag Correction
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Solution Overview
Problem
Expansion/contraction sensors, such as CNT strain sensors and braid-based sensors, exhibit asymmetric output signals due to viscoelasticity, leading to differing response times during expansion and contraction, which affects their ability to accurately follow wearer movements.
Innovation Solution
A signal processing method and device that corrects signal lag by using a Kalman filter based on the standard linear solid model, specifically addressing the slowing down of the falling edge of the output signal to synchronize it with the rising edge, and an alternative embodiment that adjusts amplification factors based on signal envelope levels to improve dynamic range and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CNT strain sensor or braid-based sensor is used to detect expansion and contraction, then the sensor can measure stress and movement, but the output signal becomes asymmetric with different response times for expansion and contraction
Solution Approach 1:
The patent applies feedback by using the output signal itself to generate correction values that are fed back into the signal processing system. The signal processor continuously monitors the asymmetric output signal and generates correction values based on the degree of asymmetry, which are then applied to compensate for the time lag in the falling edge, creating a closed-loop correction system.
Solution Approach 2:
The patent changes the parameters of the output signal by generating correction values that modify the signal characteristics. Specifically, the system adjusts the falling edge of the output signal by applying correction values that compensate for the time lag, thereby changing the temporal parameters of the signal to achieve more symmetric rise and fall times.
2Adaptability or versatility
If the sensor uses viscoelastic materials like rubber fibers to achieve stretchability, then the sensor can be worn and flexible, but the viscoelasticity causes the falling edge of the output signal to slow down
Solution Approach 1:
The patent substitutes the mechanical response of the viscoelastic material with an electronic correction system. Instead of relying on the mechanical properties of the rubber fibers to provide fast response, the system uses a signal processor to electronically compensate for the slow falling edge caused by viscoelasticity, replacing the physical limitation with a digital correction mechanism.
Solution Approach 2:
The patent introduces a signal processor as an intermediary between the sensor and the final output. This intermediary component receives the asymmetric output signal from the viscoelastic sensor and processes it by generating and applying correction values, thereby mediating the effect of viscoelasticity and producing a corrected output signal with improved response characteristics.
3Device complexity
If the output signal is used directly for movement detection, then the system is simple, but the asymmetric signal causes inaccurate tracking during contraction
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values in a lookup table before actual movement detection occurs. The signal processor retrieves the appropriate correction values from the table based on the current signal state, allowing for rapid correction without complex real-time calculations, thus improving accuracy while keeping the system relatively simple.
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 solution effectively eliminates signal asymmetry, enabling accurate stress estimation and improved movement tracking during contraction, enhancing the sensor's ability to follow wearer movements compared to prior art.
Implementation Method 1
A CNT has the property that the electrical resistance will change with applied force to the CNT. Thus, by measuring the electrical resistance of the CNTs provided in the CNT strain sensor, the expansion and contraction of the CNT strain sensor itself or the stress that is applied to the CNT strain sensor can be detected.
Implementation Method 2
another example of the expansion/contraction sensor is a braid-based sensor that employs a braid that expands and contracts using conductive fibers and rubber fibers as the measurement object, and that detects the amount of expansion and contraction of the braid by measuring the electrical resistance of the braid
Implementation Method 3
correcting a signal lag as either a rising of a received signal that has been received from the sensor lags with respect to a falling of the received signal or the falling of the received signal lags with respect to the rising of the received signal
Data Source
AI summary
A signal processing method includes receiving a signal that rises in response to a physical change and falls in response to an opposite physical change that is opposite to the physical change from a sensor that is a stretchable sensor and outputs the signal, and correcting a signal lag as either a rising of a received signal that has been received from the sensor lags with respect to a falling of the received signal, or the falling of the received signal lags with respect to the rising of the received signal.