Digitally controlled feedback for DC offset cancellation in a wearable multichannel EMG platform

Area of Science:

• Biomedical Engineering
• Wearable Technology
• Signal Processing

Background:

• Wearable systems capture vital signs for medical applications, with surface electromyography (EMG) being key for prosthesis control.
• EMG signal acquisition faces challenges like high variability, ground loop issues, and significant DC offset due to motion and perspiration.
• Existing methods struggle with offsets orders of magnitude higher than the actual EMG signal.

Purpose of the Study:

• To develop a wearable device with a digitally controlled Analog Front End (AFE) for zero-offset biopotential acquisition.
• To address the limitations of high variability and DC offset in surface EMG signal measurement.
• To enable more reliable input for advanced medical applications, such as prosthetic limb control.

Main Methods:

• A wearable device featuring a digitally controlled Analog Front End (AFE) was designed for biopotential acquisition.
• The AFE incorporates an internal Digital to Analog Converter (DAC) for independent, per-channel DC offset removal.
• A microcontroller estimates offset and provides closed-loop feedback to the analog circuitry.

Main Results:

• The proposed AFE successfully eliminated DC offset in acquired signals.
• Surface EMG signals were tested on four subjects during various activities.
• The system demonstrated accurate acquisition of EMG signals without DC offset contamination.

Conclusions:

• The developed wearable system effectively acquires biopotentials, specifically EMG, with zero DC offset.
• This zero-offset capability enhances the reliability of EMG signals for prosthesis control and other medical applications.
• The closed-loop feedback system integrated with the AFE provides a robust solution for wearable biopotential monitoring.