The application of myoelectricity has gradually become popular in recent years. However, the knowledge of the field of EMG signal detection systems is still not well understood, so more researchers need to do more literature on this. Today we will share a report on comprehensive training on EMG signal processing from Xi'an University of Science and Technology. I hope to help people who are interested in it have a deeper understanding.

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First, the purpose and significance of the research

OBJECTIVE: The detection of surface EMG signals is mainly for clinical diagnosis and research in the fields of rehabilitation medicine and sports medicine.

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 random 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 the 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 is derived from the bioelectrical activity of the α-motor neurons in the spinal cord under the control of the motor cortex. The amplitude and frequency characteristics of the signal vary depending on the activity of the motor unit under different muscle activity levels and functional status. Physiological factors such as recruitment, and the combined effects of measuring electrode position, signal crosstalk, skin temperature, muscle length, and muscle contraction.

Under well-controlled conditions, the above changes in sEMG signal activity can largely reflect the muscle activity of muscle activity, such as local fatigue, muscle strength, muscle activation pattern, motor unit excitation conduction velocity, and multi-muscle coordination. And the changes in the characteristics of central control, thus have important academic value and application significance for sports science research, rehabilitation medicine clinical and basic research.

With the deepening of 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 a prominent feature of EMG signal research. Electromyography is not only the need of basic research, but also has far-reaching significance for understanding human nervous system information and rehabilitation engineering.

Second, the training content

The content of this group: display and processing of time domain waveform and spectrum of myoelectric signal in the upper computer

Software environment: LABVIEW

Specific work: LABVIEW and VISA installation and configuration, program design and post-debugging, to achieve serial communication with LABVIEW, the resulting data is converted and displayed as a waveform.

Third, the program design, workflow

Design:

work process:

Week 1: Collecting information, installing and configuring LABVIEW software

Week 2: Overall design and optimization of the program

Week 3: Simulation of analog signals

Week 4: Connect the hardware board for debugging

Fourth, the experimental results

Waveform when the arm is bent

Light bending arm effect (small interference, stable waveform)

V. Analysis of the results

It can be seen from the waveforms of Figures 1 to 4 that the intensity of the movement of the arm is different, and the acquired EMG signals are different, that is, the amplitude of the wave has changed, and the amplitude ranges from 0.1 mV to 5 mV, and the frequency range is from 10 Hz to 500 Hz. The main frequency component is 10 Hz to 300 Hz. As can be seen from Figures 5 to 6, the waveform of the acquired 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, and the amplitude is about 5.5 mV, which is close to the amplitude and spectrum of the myoelectric signal of the reference data. Basically in line with the expected results.

Sixth, group cooperation

Seven, summary

This time our topic is the collection and display of surface EMG signals. The main task of our group is the display part, which is realized by labview software. Since I was using the software for the first time, most of the first week was spent learning about labview. Here are some of my own understanding and summary of labview:

Labview is a program development environment developed by NI Corporation of the United States. It is a graphical programming language for creating applications using icons instead of text lines. The G graphics language is used by Labview in data flow programming. The flow of data determines the order in which programs are executed. Create a VI file in the labview, which contains three parts, namely the front panel, the block diagram and the icon/wiring board. The operation of a VI file includes the control panel, the function panel, the use and operation of the tool panel, and debugging.

Labview provides a wide range of tools and functions for data acquisition, analysis, display and storage. Users can complete a complete automated test and measurement system from instrument connection, data acquisition to analysis, display and storage in minutes. (widely used in automotive, communications, aerospace, semiconductor, electronic design and production, process control and biomedical fields).

For the problems and key points in the overall program diagram of the entire labview serial communication and waveform display, I summarized the following points:

Key point: using VISA nodes 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/O application interface for instrument programming. It uses object-oriented programming and has good compatibility, scalability and independence. The VISA node is used for serial communication programming. In order to facilitate the user's use, LabVIEW separates these VISA nodes into a sub-module, which includes 8 nodes, which respectively implement functions such as initializing serial port, serial port writing, serial port reading, interrupting, and closing the serial port.

The issues that should be noted in the configuration of the VISA serial port:

1. The stop bit is not a constant 1, 1.5, 2, etc., and is actually a value of 10, 15, and 20.

2. Terminator, the default is true, the terminator is generally OA, which is a newline.

3. The number of bytes is determined by using a read buffer byte number and reading the number of bytes to determine the number of bytes in the VISA read, and then reading it by reading VISA.

Unresolved issue

The data is not synchronized during the receipt and reception of the receipt, resulting in errors in the received data, so that the final signal waveform does not achieve the expected results.

The harvest and shortcomings of this lesson: Through this lesson, we have a further understanding of signal processing. The EMG signal needs to be amplified, voltage boosted, filtered, A/D converted and other multi-step processing from acquisition to display. , wherein the myoelectric signal is a weak signal, with obvious noise and power frequency interference, and the circuit is unstable. There is also an error between data transmission and transmission, which does not guarantee complete error-free transmission. The most important reason for the problem is that there is no coordination between the group and the group. The whole system is debugging too late. Finally, it is very regrettable that the waveform is not displayed perfectly. Although the class is over, I think our work is not over yet. , should continue to improve between data transmission and reception. At the same time, I would like to thank the team members and the teachers for their guidance.

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