Low Power Long Term sEMG Monitoring Modular System

The future of rehabilitation medicine will rely on technologies to monitor patients and implement rehabilitation interventions in their home. Technology that is wearable, low-cost, suitable for home use, and capable of operating for long periods of time will be of paramount importance in enabling interventions outside of the clinic. This thesis is part of SISTER, a project conceived by MITOR, a collaboration between Politecnico di Torino, Massachusetts Institute of Technology (MIT) and Harvard Medical School. The goal of the project is to design and manufacture a wearable device to acquire and elaborate surface ElectroMyoGraphy (sEMG) data to characterize aberrant muscle activity patterns that rehabilitation medicine specialist will be able to use to plan clinical interventions. The innovative approach of Average Threshold Crossing (ATC) technique is implemented to drastically reduce the power consumption due to the minimal amount of data to be processed. It is obtained by averaging the number of sEMG Threshold Crossing (TC) events in a fixed time window. Particularly the aim of this thesis project is to develop a modular board to meet the needs of the future testing phases. The developed system layout has been designed to be compatible with commercial mechanical characteristics that make it an open system which can be easily interfaced with additional analog and digital modules. The main board has an integrated antenna and the microcontroller supports different wireless communication protocols such as Bluetooth Low Energy and others. It features also a micro SD card slot, a micro USB interface and a power management unit. A programmable gain sEMG acquisition module has also been developed improving the precedent versions basic structure. The power consumption optimization of the acquisition channel has been optimized by selecting ultra low power components. A main board and an analog front end (4.4cm x 8.4cm each) have been thus designed and fabricated. The firmware has been developed and the validation of the final system has been performed. Preliminary experiments show that the EMG acquisition channel power consumption has been reduced by about 60% and its reliability increased. The system peak power consumption has been reduced by about 50%, relaxing the battery constraints. By using a 2.6Ah battery the system can last more than one week of continuous operation.