A new portable High Density Surface EMG Multichannel Acquisition System

The research and development of biomedical instrumentation for the detection and measurement of the electrical activity generated by the human body is an innovative sector of engineering that is in continuous evolution. The biopotential measurement by non-invasive techniques is a currently booming area in research centers involved in the study of the neuromuscular system and its application fields, such as sports medicine, motor rehabilitation, development of active prostheses, occupational medicine and ergonomics. The growing need to carry out field observation and high accuracy measurements of the electrical activity generated by muscles requires the use of innovative technologies and solutions able to apply quantitative measurement techniques, developed in research laboratories, directly in the real context. In particular, the evolution of surface electromyography has developed noninvasive quantitative methods and techniques that are able to study and analyze functional aspects of muscle activity of an individual in real time. The imminent need to monitor large areas of the skin and perform real-time measurements of individuals outside research laboratories requires the development of high quality wearable instrumentation. The work described in this dissertation proposes the design of an innovative wearable solution for multi-channel acquisition of EMG signals. The main innovative aspects concern high safety, lightness, and wearability. The functional performance and design criteria have been defined in order to be able to simultaneously acquire a large number of channels (up to 400) with high accuracy, high resistance to interference of the electrical network and low noise in order to detect low levels of muscular activity (microvolts). Chapter 1 presents the results of the study of the state of the art concerning the circuit techniques and solutions for the detection of bio-potential by means of surface electrodes. The chapter also indicates and describes the electrochemical and mechanical problems related to the electrode-skin contact and conditioning techniques of the electromyographic signal. The following sections report the selection criteria and the high-performance electronic components identified to implement the proposed solution efficiently in accordance with the state of the art and currently available technologies. The study also analyses monitoring problems and real time data recording, identifying the best solution for the interconnection with a personal computer. As a result, the specific basis of the data acquisition software was defined identifying the main problems and critical aspects in running an application software in real-time. Chapter 2 introduces and describes the project in detail, indicating the circuit choices and design criteria for each section of the acquisition system. Design formulas and validation criteria of performance have been defined in order to analyze the critical aspects of operation of the equipment. The description of the project is concluded with the development of the digital section of the instrumentation. The final part of the chapter is devoted to acquisition software that deals with the reception, display and recording of the acquired data, with particular reference to the real-time libraries used. Chapter 3 shows the prototyping phase of the acquisition system with the characterization of the actual performance to carry out a comparative analysis with respect to the benefits provided. The measurement setup and data processing are described in detail displaying the algorithms used and the procedures adopted to estimate the operating parameters analyzed. Chapter 4 describes experimental measurement setup by way of applicative example of the prototype. In this context, an assessment was made of the quality of the EMG signal recorded in order to validate the expected performance. Discussion and Conclusion section reports the advantages of the innovating idea and a brief overview of field applications which could gain benefits by using the proposed solution.