Training report on signal processing of surface EMG signal detection system
The application of EMG has been gradually popularized in recent years. However, the knowledge in the field of EMG signal detection system is still not enough, so we need more scientific researchers to make more literature on this. Today we will share a report on comprehensive training of EMG signal processing from Xi'an University of Science and Technology. Hope to help people who are interested in this to have a deeper understanding.
Delsys full wireless surface EMG test system
The EMG sensor is mixed with the 3D acceleration sensor on the same sensor. This revolutionary hybrid EMG / motion provides an unprecedented combination of data in a reliable way. Its new design has unmatched high-quality performance expected by the product, and it can also record noise sources freely in a software package.
1. The purpose and significance of the study
Purpose: The detection of surface EMG signals is mainly for clinical diagnosis and research and analysis in rehabilitation medicine, sports medicine and other fields.
Significance: surface electromyography (sEMG) signal is a one-dimensional voltage time series signal obtained by the surface electrode guiding, amplifying, displaying and recording the bioelectrical changes of the neuromuscular system during voluntary and involuntary activities The amplitude is about 0-5mV, the frequency is 0-500Hz, and the signal shape has strong randomness and instability. Compared with traditional needle electromyography, the spatial resolution of sEMG is relatively low, but the detection space is large and the repeatability is good.
Basic research shows that the sEMG signal originates from the bioelectrical activity of spinal α motor neurons under the control of the motor cortex of the brain. The amplitude and frequency characteristics of the signal depend on the synchronization of motor unit activity and muscle fibers under different muscle activity levels and functional states. Recruitment and other physiological factors, as well as the measurement of electrode position, signal crosstalk, skin temperature, muscle length and muscle contraction and other measuring factors.
Under well-controlled conditions, the above-mentioned changes in sEMG signal activity can largely reflect the local fatigue level, muscle strength level, muscle activation pattern, motor unit excitation conduction speed, coordination of multiple muscle groups and other muscle activities. The change law of central and central control characteristics has important academic value and application significance for sports scientific research, clinical rehabilitation and basic research.
With the deepening of people's research and understanding of EMG signals and the advancement of EMG detection technology, the development of EMG signal processing methods and the widespread application of EMG signal processing have become an outstanding feature of EMG signal research. EMG testing is not only a need for basic research, but also has profound significance for understanding human nervous system information and rehabilitation engineering.
2. Training content
Contents of this group: display and processing of time domain waveform and spectrum of EMG signal in the host computer
Software environment: LABVIEW
Specific work: the installation and configuration of LABVIEW and VISA, the design of the program and the later debugging, in order to realize the serial port communication with LABVIEW, convert the obtained data and display it as a waveform.
3. Scheme design and work flow
Design:
work process:
Week 1: Collect information, install and configure LABVIEW software
The second week: the overall design and optimization of the program
Week 3: Simulation of analog signals
Week 4: Connect the hardware circuit board for debugging
4. Experimental results
Waveform at crank
Light arm flexion effect (small interference, stable waveform)
V. Discussion and analysis of results
It can be seen from the waveforms in Figures 1 to 4 that the intensity of the arm movement is different, and the collected EMG signals are different, that is, the amplitude of the wave line changes, and the amplitude range is 0.1mV to 5mV, and the frequency range is 10Hz to 500Hz The main frequency component is 10 Hz to 300 Hz. As can be seen from Figures 5 to 6, the waveform of the collected EMG signal is clear, the noise component is small, and there is almost no obvious power frequency noise. The signal frequency is mainly distributed between 5 and 350 Hz, with an amplitude of about 5.5 mV, which is close to the EMG signal amplitude and frequency spectrum of the reference material. Basically in line with the expected results.
VI. Team collaboration
7. Summary
Our subject this time is the collection and display of surface EMG signals. The main task of our group is the display part, which is implemented using labview software. Since this is my first time using the software, most of the first week is spent on learning and learning labview. The following are some of my understanding and summary of labview:
Labview is a program development environment, developed by NI company in the United States. It is a graphical programming language-G graphics language that uses icons to replace text lines to create applications. Labview uses data flow programming, and between nodes in the program block diagram. The data flow determines the execution order of the program. Create a VI file in labview, the file contains three parts, namely the front panel, the block diagram and the icon / connection board, the operation of a VI file includes the use of the control panel, function panel, tool panel, debugging, etc.
Labview provides a large number of tools and functions for data collection, analysis, display and storage. Users can complete a complete set of automated test and measurement systems from instrument connection, data acquisition to analysis, display and storage in minutes. (Widely used in various fields such as automobile, communication, aviation, semiconductor, electronic design and production, process control and biomedicine).
For some problems and key points in the overall program view of the entire labview serial communication and waveform display, I have summarized the following points:
Key point: use VISA node for serial communication in labview
VISA is the virtual instrument software architecture, which is essentially a general term for an I / O port software library and its specifications. VISA is a standard I / 0 application program interface used in instrument programming. It uses object-oriented programming and has good compatibility, scalability, and independence. Use VISA node for serial communication programming. In order to facilitate users' use, labview combines these VISA nodes into a single sub-module, which contains a total of 8 nodes, which respectively realize the functions of initializing serial port, serial port writing, serial port reading, interrupting and closing the serial port.
Issues that should be noted in the configuration of the VISA serial port:
1. The stop bits are not constants 1, 1.5, 2, etc., but are actually 10, 15, 20 values.
2. Terminator, generally defaults to true, and terminator generally defaults to OA, which is the newline character.
3. To determine the number of bytes, use the number of bytes in a read buffer. When the number of bytes is read, the number of bytes in VISA reading is determined, and then read out by reading VISA.
Unresolved issues
The process of sending and receiving receipts is not synchronized, resulting in errors in the received data, which affects the final signal waveform and does not achieve the expected results.
Gains and deficiencies of this course: Through this course, we have a better understanding of signal processing. From the acquisition to the display of EMG signals, we need to amplify, voltage rise, filter, A / D conversion and other multi-step processing Among them, the EMG signal is a weak signal, there is obvious noise and power frequency interference, and the circuit is unstable. There is also an error between data transmission and transmission, which cannot guarantee complete error-free transmission. The most important reason for the problem is that the coordination between the groups is not good, the entire system is debugged too late, and it is regrettable that the waveform diagram is not perfectly displayed in the end. Although the course is over, I think our work is not over. , Should continue to improve between data transmission and reception. At the same time thank the team members and teachers for their guidance.
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