Electromyographic signal acquisition circuit
By designing an electromyography signal acquisition circuit including acquisition channel, common mode elimination circuit and digital-to-analog conversion circuit, the problem of low signal-to-noise ratio and difficulty in collecting weak electromyography signals in the prior art is solved, and high-precision muscles are achieved Electric signal acquisition and feature extraction.
Patent Information
- Application Number
- CN202411427778.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-02-18
AI Technical Summary
The prior art is difficult to effectively collect weak EMF signals, especially when collecting slight wrist movement EMF signals in wearable devices, the signal-to-noise is relatively low and it is difficult to extract EMF features.
An electromyography signal acquisition circuit is designed, including a acquisition channel, a common mode cancellation circuit and a digital-to-analog conversion circuit. The acquisition channel filters and amplifies the electromyography signal through a primary amplification circuit, a direct-interrupted high-pass filter circuit and a low-pass filter circuit. The common-mode cancellation circuit is used to eliminate industrial frequency noise and improve signal-to-noise ratio.
This circuit can effectively filter out low-frequency signals of 0 to 5hz and high-frequency noise above 500hz, improve the signal-to-noise ratio, and collect high-precision electromyography signals. It is suitable for the acquisition of slight wrist movement electromyography signals in wearable devices.
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Figure CN119454043A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of biological signal acquisition, and in particular to an electromyographic signal acquisition circuit. Background Art
[0002] After being stimulated, nerves, muscles and other tissues can quickly produce conductive motion positioning, and corresponding potential changes occur during the conduction process. This potential change is called electromyography. As the source of electrical signals that produce muscle activity, electromyographic signals essentially reflect the state of movement of the nerve, skeleton and muscle system. Since the first observation of muscle potential diagrams in 1922, the research and application of electromyographic signals has a history of exactly 100 years. Due to the close correlation between electromyographic signals and muscles and human movement, it has great application potential in sports, sports and rehabilitation medicine, neurorehabilitation engineering, and human-computer interaction. Electromyographic engineering technology is an engineering technology for solving electromyographic application technology problems in different fields, including electromyographic signal acquisition, processing, analysis and application. Today's academic community generally believes that electromyographic engineering will become a scientific and industrial technology field that is as important as EEG and ECG applications. Summary of the invention
[0003] In view of this, the present application provides an electromyographic signal acquisition circuit to acquire weak electromyographic primitive signals.
[0004] According to one aspect of the present invention, there is provided an electromyographic signal acquisition circuit, comprising: one or more acquisition channels, for acquiring electromyographic signals and filtering and amplifying the electromyographic signals; and a common-mode elimination circuit, connected to each of the one or more acquisition channels, for acquiring common-mode signals in the electromyographic signals and amplifying them; and a digital-to-analog conversion circuit, to which each of the one or more acquisition channels is connected.
[0005] Optionally, each of the one or more acquisition channels includes: a first electrode and a second electrode, used to acquire electromyographic signals; a first-stage amplifier circuit, used to amplify the electromyographic signals; a DC-isolating high-pass filter circuit, used to isolate the electromyographic signals; and a low-pass filter and amplifier circuit, used to low-pass filter and amplify the electromyographic signals.
[0006] Optionally, the first-stage amplification circuit includes: a first differential amplifier, the positive input terminal of the first differential amplifier is connected to the first electrode, the negative input terminal of the first differential amplifier is connected to the second electrode, and the output terminal of the first differential amplifier is connected to a DC isolation high-pass filter circuit; a filter circuit, connected between the first electrode and the positive input terminal of the first differential amplifier and between the second electrode and the negative input terminal of the first differential amplifier.
[0007] Optionally, the DC blocking high-pass filter circuit is an RC filter circuit, which includes: a first capacitor, a first end of which is connected to the first-stage amplifier circuit, and a second end of which is connected to the low-pass filter circuit; and a first resistor, which is connected between the second end of the first capacitor and the ground terminal.
[0008] Optionally, the DC-isolating high-pass filter circuit filters out low-frequency signals of 0 to 5 Hz in the electromyographic signal.
[0009] Optionally, the low-pass filtering and amplifying circuit includes: a second operational amplifier, a DC-isolating high-pass filtering circuit connected to the negative input terminal of the second operational amplifier, and the output terminal of the second operational amplifier connected to the digital-to-analog conversion circuit; a third resistor and a second capacitor connected in parallel between the negative input terminal and the output terminal of the second operational amplifier; and a fifth resistor connected between the positive input terminal and the ground terminal of the second operational amplifier.
[0010] Optionally, the low-pass filter and amplification circuit 150 filters out high-frequency noise above 500 Hz in the electromyographic signal.
[0011] Optionally, the common-mode elimination circuit includes a third operational amplifier, a negative input terminal of the third operational amplifier is respectively connected to the positive input terminal and the negative input terminal of the first-stage amplifier circuit in the acquisition channel, the positive input terminal of the third operational amplifier is connected to the ground terminal, and the output terminal of the third operational amplifier is connected to the third electrode.
[0012] Optionally, the digital-to-analog conversion circuit adopts, for example, a multi-channel digital-to-analog conversion circuit.
[0013] The advantages and positive effects of the present invention are as follows: the first electrode and the second electrode of the present embodiment collect the electromyographic signal of the human body, and the electromyographic signal is amplified by the first-stage amplifier circuit, and then is isolated by the high-pass filter circuit to filter out the 0-5 Hz low-frequency signal that is irrelevant to the electromyographic signal. Then, the low-pass filter and the amplifier circuit filter out the high-frequency noise above 500 Hz in the signal, and perform a second amplification of the signal. The circuit of the present application is simple, low in power consumption, and the signal-to-noise ratio is improved by filtering and suppressing noise. It can collect weak electromyographic primitive signals, which is beneficial for application in the wearable field, and collects electromyographic signals of slight wrist movements. Using high-precision AD sampling, more electromyographic features can be extracted.
[0014] In order to eliminate the industrial frequency noise introduced into the circuit by the skin and the air, the present application adds a common-mode elimination circuit. The common-mode elimination circuit extracts the common-mode voltage, amplifies it in reverse, and then feeds it back to the human body. The common-mode signal of the human body will be suppressed after being superimposed on the reverse-amplified common-mode signal, thereby improving the signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 The electromyographic signal acquisition circuit of the first embodiment of the present application is shown;
[0016] Figure 2 A circuit schematic diagram of a first-stage amplifier circuit of the first embodiment of the present application is shown;
[0017] Figure 3 A circuit schematic diagram of a DC blocking high-pass filter circuit according to a first embodiment of the present application is shown;
[0018] Figure 4 The circuit schematic diagram of the low-pass filter and amplifier circuit of the first embodiment of the present application is shown;
[0019] Figure 5 A circuit schematic diagram of a common mode elimination circuit according to a first embodiment of the present application is shown;
[0020] Figure 6 The electromyographic signal acquisition circuit of the second embodiment of the present application is shown. DETAILED DESCRIPTION
[0021] In order to better understand the present invention, the present invention is further described below in conjunction with specific embodiments and drawings.
[0022] Figure 1 The acquisition circuit of the electromyographic signal of the first embodiment of the present application is shown, and the acquisition circuit includes an acquisition channel 10, a common mode elimination circuit 20 connected to the acquisition channel 10, and a digital-to-analog conversion circuit 30 connected to the acquisition channel 10. The acquisition channel 10 is used to acquire electromyographic signals and filter and amplify the electromyographic signals, and the common mode elimination circuit 20 is used to acquire common mode signals in the electromyographic signals and amplify them. Among them, the acquisition channel 10 includes a first electrode 110, a second electrode 120, a primary amplifier circuit 130, a DC isolation high-pass filter circuit 140, a low-pass filter and an amplifier circuit 150.
[0023] Figure 2 FIG. 1 shows a circuit schematic diagram of a first-stage amplifier circuit 130 according to a first embodiment of the present application. Figure 2As shown, the first-stage amplifier circuit 130 includes a differential amplifier U1, the positive input terminal of the differential amplifier U1 is connected to the first electrode 110, the negative input terminal of the differential amplifier U1 is connected to the second electrode 120, and the output terminal of the differential amplifier U1 is connected to the DC isolation high-pass filter circuit 140. Further, the first-stage amplifier circuit 130 also includes a filter circuit, and the filter circuit is composed of a resistor R6, a capacitor C3, a resistor R7 and a capacitor C5. Among them, the resistor R6 is connected between the first electrode 110 and the positive input terminal of the differential amplifier U1, one end of the capacitor C3 is connected to the intersection between the resistor R6 and the positive input terminal of the differential amplifier U1, and the other end is grounded. The resistor R7 is connected between the second electrode 120 and the negative input terminal of the differential amplifier U1, one end of the capacitor C5 is connected to the intersection between the resistor R7 and the negative input terminal of the differential amplifier U1, and the other end is grounded. This embodiment uses a micro-power consumption, high-impedance differential amplifier to ensure that the signal is completely extracted and runs at a lower power consumption.
[0024] Figure 3 FIG. 4 shows a circuit schematic diagram of a DC blocking high-pass filter circuit 140 according to a first embodiment of the present application. Figure 3 As shown, the DC-blocking high-pass filter circuit 140 is, for example, an RC filter circuit, which includes a capacitor C1 and a resistor R11, wherein the first end of the capacitor C1 is connected to the primary amplifier circuit 130, and the second end is connected to the low-pass filter circuit 150, and the resistor R11 is connected between the second end of the capacitor C11 and the ground terminal. After the electromyographic signal is amplified by the primary amplifier circuit 130, it is subjected to DC-blocking processing by the DC-blocking high-pass filter circuit 140 to filter out the 0-5 Hz low-frequency signal that is irrelevant to the electromyographic signal.
[0025] Figure 4 FIG. 4 shows a circuit schematic diagram of a low-pass filter and amplifier circuit 150 according to a first embodiment of the present application. Figure 4 As shown, the low-pass filtering and amplifying circuit 150 includes an operational amplifier U7, the second end of the capacitor C1 is connected to the negative input terminal of the operational amplifier U7 via the resistor R2, and the output terminal of the operational amplifier U7 is connected to the digital-to-analog conversion circuit 30. The low-pass filtering and amplifying circuit 150 also includes a resistor R3 and a capacitor C2 connected in parallel between the negative input terminal and the output terminal of the operational amplifier U7, a resistor R5 connected between the positive input terminal and the ground terminal of the operational amplifier U7, and a resistor R4 connected between the positive input terminal and the power supply of the operational amplifier U7. The power supply is, for example, a 3.3V power supply. The low-pass filtering and amplifying circuit 150 filters out high-frequency noise above 500 Hz in the signal and performs secondary amplification of the signal.
[0026] Figure 5 FIG. 4 shows a circuit schematic diagram of a common mode elimination circuit 20 according to a first embodiment of the present application. Figure 5As shown, the common mode elimination circuit 20 is connected to the acquisition channel 10, specifically connected to the gain pin in the acquisition channel 10. The common mode elimination circuit 20 includes an operational amplifier U3, a negative input terminal of the operational amplifier U3 is connected to the gain pin of the differential amplifier U1 in the acquisition channel 10 via resistors R19, R22 and R23 respectively, a positive input terminal of the operational amplifier U3 is connected to the ground terminal, and an output terminal of the operational amplifier U3 is connected to the third electrode 210.
[0027] The first electrode 110 and the second electrode 120 of the acquisition circuit of this embodiment are respectively attached to the two arms of the human body, and the third electrode 210 is attached to the right leg of the human body. The first electrode 110 and the second electrode 120 collect the electromyographic signal of the human body. After the electromyographic signal is amplified by the first-stage amplifier circuit 130, it is isolated by the high-pass filter circuit 140 to filter out the 0-5 Hz low-frequency signal that is irrelevant to the electromyographic signal. Then, the low-pass filter and amplifier circuit 150 filters out the high-frequency noise above 500 Hz in the signal, and performs secondary amplification of the signal.
[0028] In order to eliminate the industrial frequency noise introduced into the circuit by the skin and the air, the present application adds a common-mode elimination circuit 20. The common-mode elimination circuit 20 extracts the common-mode voltage, amplifies it in reverse, and then feeds it back to the human body. The common-mode signal of the human body will be suppressed after being superimposed on the reverse-amplified common-mode signal, thereby improving the signal-to-noise ratio.
[0029] Figure 6 The acquisition circuit of the electromyographic signal of the second embodiment of the present application is shown, and the acquisition circuit includes multiple acquisition channels 10, a common mode elimination circuit 20 connected to each of the multiple acquisition channels, and a digital-to-analog conversion circuit 30 connected to each of the multiple acquisition channels. Among them, the acquisition channel 10 includes a first electrode 110, a second electrode 120, a primary amplifier circuit 130, a direct-blocking high-pass filter circuit 140, and a low-pass filter and amplifier circuit 150. Among them, the structures of the first electrode 110, the second electrode 120, the primary amplifier circuit 130, the direct-blocking high-pass filter circuit 140, the low-pass filter and the amplifier circuit 150 of each acquisition channel 10 are the same as those of the first embodiment, and this embodiment will not be repeated here.
[0030] In this embodiment, the common mode elimination circuit 20 is connected to the first-stage amplifier circuit 130 of each acquisition channel, specifically connected to the gain pin of the differential amplifier U1 in each acquisition channel 10. The low-pass filter and amplifier circuit 150 of multiple acquisition channels 10 are connected to the digital-to-analog conversion circuit 30. In this embodiment, the digital-to-analog conversion circuit 30 adopts, for example, a multi-channel 16-bit high-precision digital-to-analog conversion circuit.
[0031] Furthermore, in this embodiment, multiple groups of first electrodes 110 and second electrodes 120 and a third electrode 210 are provided. The multiple groups of first electrodes 110 and second electrodes 120 are used to collect multiple groups of electromyographic signals at different positions. The third electrode 210 is attached to the right leg of the human body.
[0032] The first electrode and the second electrode of this embodiment collect the electromyographic signal of the human body. After the electromyographic signal is amplified by the first-stage amplifier circuit, it is isolated by the DC isolation high-pass filter circuit to filter out the 0-5 Hz low-frequency signal that is irrelevant to the electromyographic signal. Then, the low-pass filter and the amplifier circuit filter out the high-frequency noise above 500 Hz in the signal, and perform a second amplification of the signal. The circuit of the present application is simple, low in power consumption, and improves the signal-to-noise ratio by filtering and suppressing noise. It can collect weak electromyographic primitive signals, which is beneficial for application in the wearable field. It can collect electromyographic signals of slight wrist movements, and use high-precision AD sampling to extract more electromyographic features.
[0033] In order to eliminate the industrial frequency noise introduced into the circuit by the skin and the air, the present application adds a common-mode elimination circuit. The common-mode elimination circuit extracts the common-mode voltage, amplifies it in reverse, and then feeds it back to the human body. The common-mode signal of the human body will be suppressed after being superimposed on the reverse-amplified common-mode signal, thereby improving the signal-to-noise ratio.
[0034] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of this patent.
Claims
1. A myoelectric signal acquisition circuit, comprising: One or more acquisition channels, used to collect electromyographic signals and filter and amplify the electromyographic signals; as well as A common mode elimination circuit is connected to each of the one or more acquisition channels and is used to acquire a common mode signal in the electromyographic signal and amplify it; as well as A digital-to-analog conversion circuit, each of the one or more acquisition channels is connected to the digital-to-analog conversion circuit.
2. The myoelectric signal acquisition circuit according to claim 1, wherein: Each of the one or more acquisition channels includes: The first electrode and the second electrode are used to collect electromyographic signals; A first-stage amplifier circuit is used to amplify the electromyographic signal; A DC-isolating high-pass filter circuit is used to perform DC-isolating processing on the electromyographic signal; and The low-pass filtering and amplifying circuit is used for low-pass filtering and amplifying the electromyographic signal.
3. The myoelectric signal acquisition circuit according to claim 2, wherein: The first stage amplifier circuit includes: A first differential amplifier, wherein a positive input terminal of the first differential amplifier is connected to the first electrode, a negative input terminal of the first differential amplifier is connected to the second electrode, and an output terminal of the first differential amplifier is connected to a DC-isolating high-pass filter circuit; The filter circuit is connected between the first electrode and the positive input terminal of the first differential amplifier and between the second electrode and the negative input terminal of the first differential amplifier.
4. The myoelectric signal acquisition circuit according to claim 2, wherein: The DC blocking high-pass filter circuit is an RC filter circuit, which includes: A first capacitor, wherein a first end of the first capacitor is connected to the first-stage amplification circuit, and a second end of the first capacitor is connected to the low-pass filter circuit; and The first resistor is connected between the second end of the first capacitor and the ground end.
5. The myoelectric signal acquisition circuit according to claim 4, wherein: The DC-isolating high-pass filter circuit filters out the 0-5 Hz low-frequency signal in the electromyographic signal.
6. The myoelectric signal acquisition circuit according to claim 2, wherein: The low-pass filter and amplifier circuit includes: A second operational amplifier, a DC-isolating high-pass filter circuit is connected to a negative input terminal of the second operational amplifier, and an output terminal of the second operational amplifier is connected to a digital-to-analog conversion circuit; a third resistor and a second capacitor connected in parallel between the negative input terminal and the output terminal of the second operational amplifier; and A fifth resistor is connected between the positive input terminal of the second operational amplifier and the ground terminal.
7. The myoelectric signal acquisition circuit according to claim 6, wherein: The low-pass filter and amplifier circuit 150 filters out high-frequency noise above 500 Hz in the electromyographic signal.
8. The myoelectric signal acquisition circuit according to claim 2, wherein: The common-mode elimination circuit includes a third operational amplifier, a negative input terminal of the third operational amplifier is respectively connected to the positive input terminal and the negative input terminal of the first-stage amplifier circuit in the acquisition channel, the positive input terminal of the third operational amplifier is connected to the ground terminal, and the output terminal of the third operational amplifier is connected to the third electrode.
9. The myoelectric signal acquisition circuit according to claim 1, wherein: The digital-to-analog conversion circuit adopts, for example, a multi-channel digital-to-analog conversion circuit.