EMG Sensor Contact Detection Using Spectral Entropy Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing EMG sensors face challenges in maintaining reliable contact with the skin, particularly on dynamic areas like the face, leading to signal degradation and erroneous data due to adhesive issues and movement artifacts, with existing solutions prone to false positives and requiring expensive circuitry.
Innovation Solution
A method involving spectral entropy calculation of EMG sensor data to determine contact quality, where high entropy indicates poor contact and low entropy indicates good contact, allowing for data processing and feedback to ensure accurate signal capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive tape or self-adhesive stickers are used to fix EMG sensors, then the sensors can be held against the body, but the contact becomes ineffective on dynamic areas like the face and users may develop allergies
Solution Approach 1:
The patent replaces the mechanical adhesive system with a non-adhesive sensor design that uses spring-loaded contact elements to maintain mechanical pressure and electrical contact with the skin without requiring adhesives, thereby eliminating allergy issues while maintaining contact reliability on dynamic body areas
Solution Approach 2:
The patent incorporates dynamic elements including spring-loaded contact mechanisms that adapt to skin movement and deformation, allowing the sensor to maintain reliable contact on dynamic areas like the face where skin frequently moves and wrinkles
2Adaptability or versatility
If non-adhesive sensors are used to overcome adhesive issues, then allergy problems are eliminated, but the sensors lift from the skin surface and movement artifacts degrade signal quality
Solution Approach 1:
The patent uses dynamic spring-loaded contact elements that continuously adapt to skin movement and deformation, preventing sensor lift and maintaining consistent electrical contact during facial expressions and head movements, thereby eliminating movement artifacts while keeping the non-adhesive design
Solution Approach 2:
The patent incorporates feedback mechanisms that monitor contact quality in real-time and adjust the contact pressure dynamically to maintain optimal signal quality during movement, preventing sensor lift and artifacts through active compensation
3Measurement precision
If a fixed DC signal is injected to detect sensor lift, then lift detection is achieved, but the method is prone to false positives and detects lift with latency
Solution Approach 1:
The patent uses periodic AC signal injection at a reference frequency (e.g., 1 kHz) instead of fixed DC signal, allowing continuous monitoring of contact impedance with high temporal resolution and enabling detection of sensor lift events with minimal latency and without false positives from physiological signals
4Measurement precision
If a reference AC signal is injected at a different frequency to detect contact continuously, then measurement precision improves, but expensive specialized circuitry and ADC devices are required
Solution Approach 1:
The patent designs the signal processing circuitry to serve multiple functions: the same ADC and processing hardware used for EMG signal acquisition is also used to detect the reference signal impedance changes, eliminating the need for separate expensive specialized circuitry and reducing overall system complexity
Solution Approach 2:
The patent combines the EMG signal amplification and reference signal impedance detection functions into a single integrated circuit pathway, where the operational amplifiers and ADC used for EMG signals also process the reference signal, thereby reducing component count and cost while maintaining continuous contact measurement capability
Data Source
AI summary
A method of determining a measure of contact of an EMG sensor with the skin of a human or animal subject, the method comprising: receiving data captured by the EMG sensor; calculating a spectral entropy of the received data over a first time period in respect of a predetermined frequency band; determining a measure of contact for the first time period in dependence on the spectral entropy of the received data; and processing the received data of the first time period in dependence on the measure of contact.