阅读说明：本技术 Emg肌电信号数字采集电路及系統 (EMG (electromagnetic EMG) electromyographic signal digital acquisition circuit and system ) 是由 彭丹 房金妮 曹蓉 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种EMG肌电信号数字采集电路及系統,该EMG肌电信号数字采集电路包括：信号采集端；信号放大电路,其输入端与信号采集端连接,用于对信号采集端采集到的肌电信号进行差分放大；滤波抬升电路,其输入端与信号放大电路的输出端连接,用于将经过差分放大后的肌电信号进行滤波和电压抬升,得到待处理肌电信号；控制芯片,控制芯片的采集端与滤波抬升电路的输出端连接,用于对待处理肌电信号进行运算,得到时域肌电信号和频域肌电信号。本发明通过各电路的配合设计,能够对微弱的肌电信号进行放大、信号过滤和积分转换,得到经过放大且干扰少的时域肌电信号和频域肌电信号。(The invention discloses an EMG electromyographic signal digital acquisition circuit and system, wherein the EMG electromyographic signal digital acquisition circuit comprises: a signal acquisition end; the input end of the signal amplification circuit is connected with the signal acquisition end and is used for carrying out differential amplification on the electromyographic signals acquired by the signal acquisition end; the input end of the filtering and lifting circuit is connected with the output end of the signal amplifying circuit and is used for filtering and lifting the electromyographic signals subjected to differential amplification to obtain electromyographic signals to be processed; and the acquisition end of the control chip is connected with the output end of the filtering and lifting circuit and is used for calculating the electromyographic signals to be processed to obtain time domain electromyographic signals and frequency domain electromyographic signals. Through the matching design of all circuits, the weak electromyographic signals can be amplified, filtered and subjected to integral conversion, so that time-domain electromyographic signals and frequency-domain electromyographic signals which are amplified and have less interference are obtained.)

1. An EMG electromyographic signal digital acquisition circuit, comprising:

a signal acquisition end;

the input end of the signal amplification circuit is connected with the signal acquisition end and is used for carrying out differential amplification on the electromyographic signals acquired by the signal acquisition end;

the input end of the filtering and lifting circuit is connected with the output end of the signal amplifying circuit and is used for filtering and voltage lifting the electromyographic signals subjected to differential amplification to obtain electromyographic signals to be processed;

and the acquisition end of the control chip is connected with the output end of the filtering and lifting circuit and is used for calculating the electromyographic signals to be processed to obtain time domain electromyographic signals and frequency domain electromyographic signals.

2. The digital EMG electromyographic signal acquisition circuit of claim 1 wherein the signal amplification circuit comprises an instrumentation amplifier, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor, a first transient diode, and a second transient diode;

the non-inverting input end of the instrumentation amplifier is connected with the forward acquisition end of the signal acquisition end through the first resistor, and the inverting input end of the instrumentation amplifier is connected with the inverting acquisition end of the signal acquisition end through the second resistor; the first gain access end of the instrumentation amplifier is connected with one end of the third resistor, and the second gain access end of the instrumentation amplifier is connected with the other end of the third resistor; the output end of the instrument amplifier is the output end of the signal amplification circuit; a first power supply input end of the instrumentation amplifier is connected with a first power supply, and a second power supply input end of the instrumentation amplifier is connected with a second power supply; one end of the first capacitor is grounded, the other end of the first capacitor is connected with one end of the first resistor and the non-inverting input end of the instrumentation amplifier, and the other end of the first resistor is grounded through the first transient diode; one end of the second capacitor is grounded, the other end of the second capacitor is connected with one end of the second resistor and the reverse input end of the instrumentation amplifier, and the other end of the second resistor is grounded through the second transient diode.

3. The digital EMG electromyographic signal acquisition circuit of claim 1 wherein the filter boost circuit comprises a high pass filter circuit, a low pass filter circuit, a level boost circuit, and a power frequency notch circuit; the input end of the high-pass filter circuit is the input end of the filter lifting circuit, the output end of the high-pass filter circuit is connected with the input end of the low-pass filter circuit, the output end of the low-pass filter circuit is connected with the input end of the level lifting circuit, the output end of the level lifting circuit is connected with the input end of the power frequency trap circuit, and the output end of the power frequency trap circuit is the output end of the filter lifting circuit.

4. The digital EMG electromyographic signal acquisition circuit of claim 3 wherein said high pass filter circuit comprises a third capacitor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first operational amplifier; the non-inverting input end of the first operational amplifier sequentially passes through a third capacitor and a fourth capacitor and is connected with the output end of the signal amplification circuit, the inverting input end of the first operational amplifier is grounded through a fourth resistor, the inverting input end of the operational amplifier is further connected with the output end of the first operational amplifier through a fifth resistor, a node where the third capacitor and the fourth capacitor are connected is further connected with the output end of the first operational amplifier through a sixth resistor, and the forward input end of the first operational amplifier is further grounded through a seventh resistor.

5. The EMG electromyographic signal digital acquisition circuit of claim 3 wherein said low pass filter circuit comprises a fifth capacitor, a sixth capacitor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor and a second operational amplifier; the non-inverting input end of the second operational amplifier is connected with the output end of the high-pass filter circuit through the eighth resistor and the ninth resistor in sequence, and the non-inverting input end of the second operational amplifier is grounded through a fifth capacitor; the inverting input end of the second operational amplifier is grounded through the tenth resistor, and is also connected with the output end of the second operational amplifier through the eleventh resistor; one end of the sixth capacitor is connected with the output end of the second operational amplifier, and the other end of the sixth capacitor is connected with a node where the eighth resistor and the ninth resistor are connected; the output end of the second operational amplifier is the output end of the low-pass filter circuit.

6. The digital EMG electromyographic signal acquisition circuit of claim 3 wherein said level-raising circuit comprises a twelfth resistor, a thirteenth resistor, a fourteenth resistor and a third operational amplifier; the first power supply access end of the third operational amplifier is connected with a third power supply, and the second power supply access end of the third operational amplifier is connected with a fourth power supply; the inverting input end of the third operational amplifier is grounded; the non-inverting input terminal of the third operational amplifier is connected with the output terminal of the low-pass filter circuit through the twelfth resistor, the non-inverting input terminal of the third operational amplifier is connected with the output terminal of the third operational amplifier through the thirteenth resistor, and the non-inverting input terminal of the third operational amplifier is further connected with the second power supply input terminal of the third operational amplifier through the fourteenth resistor; the output end of the third operational amplifier is the output end of the level lifting circuit.

7. The EMG electromyographic signal digital acquisition circuit of claim 3 wherein said power frequency notch circuit comprises a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a fourth operational amplifier and a fifth operational amplifier; the non-inverting input end of the fourth operational amplifier is connected with the output end of the level lifting circuit sequentially through the seventh capacitor and the eighth capacitor, and the non-inverting input end of the fourth operational amplifier is further connected with the output end of the level lifting circuit sequentially through the fifteenth resistor and the sixteenth resistor; the inverting input end of the fourth operational amplifier is connected with the non-inverting input end of the fifth operational amplifier through the seventeenth resistor, and the output end of the fourth operational amplifier is the output end of the power frequency trap circuit; the non-inverting input end of the fifth operational amplifier is grounded through the eighteenth resistor, the inverting input end of the fifth operational amplifier is connected with the output end of the fifth operational amplifier, the output end of the fifth operational amplifier is connected with one end of a ninth capacitor and one end of a nineteenth resistor, the other end of the ninth capacitor is connected with a node where the fifteenth resistor and the sixteenth resistor are connected, and the other end of the nineteenth resistor is connected with a node where the seventh capacitor and the eighth capacitor are connected.

8. The EMG electromyographic signal digital acquisition circuit of any one of claims 1-7 further comprising a shielding housing, wherein the signal amplification circuit, the filter boost circuit and the control chip are all disposed within the shielding housing.

9. The digital EMG electromyography signal acquisition circuit of claim 8, further comprising a power isolation circuit and a communication isolation circuit connected to the control chip.

10. The digital EMG electromyography signal acquisition system comprises an EMG electromyography signal digital acquisition circuit, and the digital EMG electromyography signal acquisition circuit is configured as the digital EMG electromyography signal acquisition circuit according to any one of claims 1-9.

Technical Field

The invention relates to the field of medical instruments, in particular to an EMG (electromagnetic EMG) electromyographic signal digital acquisition circuit and system.

Background

Electromyographic signals (EMG) are one-dimensional time-series electrical signals of bioelectrical changes of the neuromuscular system as the muscle is guided and recorded from the surface of the muscle by surface electrodes. The electromyographic signals reflect the functional states of nerves and muscles, and can be applied to the aspects of medical research, human engineering, neuromuscular disease diagnosis and the like. However, the electromyographic signals of the human body are very weak, and the signals acquired by the electrodes are mixed with a plurality of interference signals, such as electrode contact noise, power frequency interference, external electromagnetic field interference and the like.

Disclosure of Invention

The invention mainly aims to provide an EMG electromyographic signal digital acquisition circuit and system, and aims to solve the technical problems that the electromyographic signal is weak and interference signals are mixed.

In order to achieve the above object, the present invention provides an EMG electromyographic signal digital acquisition circuit, comprising:

a signal acquisition end;

the input end of the signal amplification circuit is connected with the signal acquisition end and is used for carrying out differential amplification on the electromyographic signals acquired by the signal acquisition end;

the input end of the filtering and lifting circuit is connected with the output end of the signal amplifying circuit and is used for filtering and voltage lifting the electromyographic signals subjected to differential amplification to obtain electromyographic signals to be processed;

and the acquisition end of the control chip is connected with the output end of the filtering and lifting circuit and is used for calculating the electromyographic signals to be processed to obtain time domain electromyographic signals and frequency domain electromyographic signals.

Optionally, the signal amplification circuit includes an instrumentation amplifier, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor, a first transient diode, and a second transient diode;

the non-inverting input end of the instrumentation amplifier is connected with the forward acquisition end of the signal acquisition end through the first resistor, and the inverting input end of the instrumentation amplifier is connected with the inverting acquisition end of the signal acquisition end through the second resistor; the first gain access end of the instrumentation amplifier is connected with one end of the third resistor, and the second gain access end of the instrumentation amplifier is connected with the other end of the third resistor; the output end of the instrument amplifier is the output end of the signal amplification circuit; a first power supply input end of the instrumentation amplifier is connected with a first power supply, and a second power supply input end of the instrumentation amplifier is connected with a second power supply; one end of the first capacitor is grounded, the other end of the first capacitor is connected with one end of the first resistor and the non-inverting input end of the instrumentation amplifier, and the other end of the first resistor is grounded through the first transient diode; one end of the second capacitor is grounded, the other end of the second capacitor is connected with one end of the second resistor and the reverse input end of the instrumentation amplifier, and the other end of the second resistor is grounded through the second transient diode.

Optionally, the filter lifting circuit includes a high-pass filter circuit, a low-pass filter circuit, a level lifting circuit, and a power frequency notch circuit; the input end of the high-pass filter circuit is the input end of the filter lifting circuit, the output end of the high-pass filter circuit is connected with the input end of the low-pass filter circuit, the output end of the low-pass filter circuit is connected with the input end of the level lifting circuit, the output end of the level lifting circuit is connected with the input end of the power frequency trap circuit, and the output end of the power frequency trap circuit is the output end of the filter lifting circuit.

Optionally, the high-pass filter circuit includes a third capacitor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and a first operational amplifier; the non-inverting input end of the first operational amplifier sequentially passes through a third capacitor and a fourth capacitor and is connected with the output end of the signal amplification circuit, the inverting input end of the first operational amplifier is grounded through a fourth resistor, the inverting input end of the operational amplifier is further connected with the output end of the first operational amplifier through a fifth resistor, a node where the third capacitor and the fourth capacitor are connected is further connected with the output end of the first operational amplifier through a sixth resistor, and the forward input end of the first operational amplifier is further grounded through a seventh resistor.

Optionally, the low-pass filter circuit includes a fifth capacitor, a sixth capacitor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, and a second operational amplifier; the non-inverting input end of the second operational amplifier is connected with the output end of the high-pass filter circuit through the eighth resistor and the ninth resistor in sequence, and the non-inverting input end of the second operational amplifier is grounded through a fifth capacitor; the inverting input end of the second operational amplifier is grounded through the tenth resistor, and is also connected with the output end of the second operational amplifier through the eleventh resistor; one end of the sixth capacitor is connected with the output end of the second operational amplifier, and the other end of the sixth capacitor is connected with a node where the eighth resistor and the ninth resistor are connected; the output end of the second operational amplifier is the output end of the low-pass filter circuit.

Optionally, the level-up circuit includes a twelfth resistor, a thirteenth resistor, a fourteenth resistor, and a third operational amplifier; the first power supply access end of the third operational amplifier is connected with a third power supply, and the second power supply access end of the third operational amplifier is connected with a fourth power supply; the inverting input end of the third operational amplifier is grounded; the non-inverting input terminal of the third operational amplifier is connected with the output terminal of the low-pass filter circuit through the twelfth resistor, the non-inverting input terminal of the third operational amplifier is connected with the output terminal of the third operational amplifier through the thirteenth resistor, and the non-inverting input terminal of the third operational amplifier is further connected with the second power supply input terminal of the third operational amplifier through the fourteenth resistor; the output end of the third operational amplifier is the output end of the level lifting circuit.

Optionally, the power frequency trap circuit includes a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a fourth operational amplifier, and a fifth operational amplifier; the non-inverting input end of the fourth operational amplifier is connected with the output end of the level lifting circuit sequentially through the seventh capacitor and the eighth capacitor, and the non-inverting input end of the fourth operational amplifier is further connected with the output end of the level lifting circuit sequentially through the fifteenth resistor and the sixteenth resistor; the inverting input end of the fourth operational amplifier is connected with the non-inverting input end of the fifth operational amplifier through the seventeenth resistor, and the output end of the fourth operational amplifier is the output end of the power frequency trap circuit; the non-inverting input end of the fifth operational amplifier is grounded through the eighteenth resistor, the inverting input end of the fifth operational amplifier is connected with the output end of the fifth operational amplifier, the output end of the fifth operational amplifier is connected with one end of a ninth capacitor and one end of a nineteenth resistor, the other end of the ninth capacitor is connected with a node where the fifteenth resistor and the sixteenth resistor are connected, and the other end of the nineteenth resistor is connected with a node where the seventh capacitor and the eighth capacitor are connected.

Optionally, the power amplifier further comprises a shielding shell, and the signal amplification circuit, the filtering and lifting circuit and the control chip are all arranged in the shielding shell.

Optionally, the EMG electromyographic signal digital acquisition circuit further includes a power isolation circuit and a communication isolation circuit connected to the control chip.

In addition, in order to achieve the aim, the invention also provides an EMG electric signal digital acquisition system which comprises an EMG electric signal digital acquisition circuit, wherein the EMG electric signal digital acquisition circuit is configured as the EMG electric signal digital acquisition circuit.

The signal acquisition end is arranged in the EMG electromyographic signal digital acquisition circuit; the input end of the signal amplification circuit is connected with the signal acquisition end and is used for carrying out differential amplification on the electromyographic signals acquired by the signal acquisition end; the input end of the filtering and lifting circuit is connected with the output end of the signal amplifying circuit and is used for filtering and voltage lifting the electromyographic signals subjected to differential amplification to obtain electromyographic signals to be processed; and the acquisition end of the control chip is connected with the output end of the filtering and lifting circuit and is used for calculating the electromyographic signals to be processed to obtain time domain electromyographic signals and frequency domain electromyographic signals. The system comprises a signal acquisition end, a control chip, a signal processing end and a signal processing end, wherein the signal processing end is connected with the signal processing end through the signal processing end, and the signal processing end is connected with the signal processing end through the signal processing end.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic block diagram of an EMG electromyographic signal digital acquisition circuit according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an alternative circuit configuration of the signal amplification circuit in the embodiment of FIG. 1;

FIG. 3 is a schematic diagram of an alternative circuit configuration of the high-pass filter circuit in the embodiment of FIG. 1;

FIG. 4 is a schematic diagram of an alternative circuit configuration of the low-pass filter circuit in the embodiment of FIG. 1;

FIG. 5 is a schematic diagram of an alternative circuit configuration of the level-up circuit of the embodiment of FIG. 1;

FIG. 6 is a schematic diagram of an alternative circuit configuration of the power frequency notch circuit in the embodiment of FIG. 1;

FIG. 7 is a schematic diagram of an alternative circuit configuration of the communication isolation circuit of the embodiment of FIG. 1;

fig. 8 is a schematic diagram of an alternative circuit structure of the power isolation circuit in the embodiment of fig. 1.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

The reference numbers illustrate:

Detailed Description

It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The invention provides an EMG electromyographic signal digital acquisition circuit, referring to fig. 1, in an embodiment, the EMG electromyographic signal digital acquisition circuit includes:

a signal acquisition terminal 10;

the input end of the signal amplifying circuit 20 is connected with the signal acquisition end 10, and is used for carrying out differential amplification on the electromyographic signals acquired by the signal acquisition end 10;

the input end of the filter lifting circuit 30 is connected with the output end of the signal amplifying circuit 20, and the filter lifting circuit 30 is used for filtering and voltage lifting the electromyographic signals subjected to differential amplification to obtain electromyographic signals to be processed;

and the acquisition end of the control chip 40 is connected with the output end of the filtering and lifting circuit 30 and is used for calculating the electromyographic signals to be processed to obtain time domain electromyographic signals and frequency domain electromyographic signals.

The EMG electromyographic signal digital acquisition circuit can be used for an EMG electromyographic signal digital acquisition system, and the system can be applied to monitoring equipment or rehabilitation physiotherapy equipment. The signal collecting terminal 10 may be a surface electrode, and the surface electrode may use a silver/silver chloride material as an inductive element. The surface electrode is attached to the skin of human body surface in the form of electrode sheet, and can be attached to arm or brain.

The surface electrode adopts a disposable electrocardio electrode to guide surface electromyogram signals and is connected to the preposed signal amplifying circuit 20 through a shielding wire, and the use of the shielding wire can reduce external interference. The number of the electrode plates can be three, one of the electrode plates is grounded GND, and the other two electrode plates input the myoelectric signals collected from the human body to the signal amplification circuit 20 for differential amplification, so that the signal amplitude of the weak myoelectric signals is improved. The muscle electric signals subjected to differential amplification are also lifted through filtering, signal interference is filtered, the amplitude of the voltage signals is further lifted, and identifiability is achieved. Furthermore, the electromyographic signals to be processed are operated through the control chip 40, and finally electromyographic signal data corresponding to a time domain and a frequency domain are obtained, so that the electromyographic signals can be conveniently subjected to data mining, and deeper biological characteristic research is realized.

Further, referring to fig. 1 and fig. 2 together, the signal amplifying circuit 20 includes an instrumentation amplifier U1, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a first transient diode TVS1, and a second transient diode TVS 2;

the non-inverting input end of the instrumentation amplifier U1 is connected with the forward acquisition end of the signal acquisition end 10 through a first resistor R1, and the inverting input end of the instrumentation amplifier U1 is connected with the inverting acquisition end of the signal acquisition end 10 through a second resistor R2; the first gain access end of the instrumentation amplifier U1 is connected with one end of a third resistor R3, and the second gain access end of the instrumentation amplifier U1 is connected with the other end of the third resistor R3; the output end of the instrument amplifier U1 is the output end of the signal amplifying circuit 20; the input end of a first power supply V1 of the instrumentation amplifier U1 is connected with a first power supply V1, and the input end of a second power supply V2 of the instrumentation amplifier U1 is connected with a second power supply V2; one end of the first capacitor C1 is grounded to GND, the other end of the first capacitor C1 is connected with one end of the first resistor R1 and the non-inverting input end of the instrumentation amplifier U1, and the other end of the first resistor R1 is grounded to GND through a first transient diode; one end of the second capacitor C2 is grounded GND, the other end of the second capacitor C2 is connected with one end of the second resistor R2 and the reverse input end of the instrumentation amplifier U1, and the other end of the second resistor R2 is grounded GND through the second transient diode.

The instrumentation amplifier U1 may be an AD8221 chip available from ADI, usa, and the AD8221 chip is a space-saving MSOP package with programmable gain, low bias current, and high common-mode rejection ratio. In this embodiment, the first electrode pad in the signal collecting terminal 10 is connected as a differential positive signal input terminal to the non-inverting input terminal of the instrumentation amplifier U1 through the first resistor R1, the second electrode pad is grounded GND, and the third electrode pad is connected as a differential negative signal input terminal to the inverting input terminal of the instrumentation amplifier U1 through the second resistor R2. The first resistor R1 and the second resistor R2 are used as voltage dividing resistors, so that the human body can be isolated, and the human body can be prevented from being injured by strong electricity. The first resistor R1 and the first capacitor C1, and the second resistor R2 and the second capacitor C2 respectively form a passive RC high-frequency filter for filtering various high-frequency pulses existing in the surrounding environment. The first transient diode and the second transient diode can correspondingly prevent the first electrode plate and the third electrode plate from damaging the instrumentation amplifier U1 due to the overhigh voltage of the input ends.

The first power supply V1 and the second power supply V2 can be correspondingly +5V and-5V, and the first power supply V1 and the second power supply V2 can be grounded GND through two parallel capacitors, so that filtering is realized, and the power supply quality is improved.

The third resistor R3 is designed to adjust the signal amplification factor, and when the AD8221 chip is used, the gain is G ═ 1+ (49.4k Ω/R3), for example, if the signal amplification factor is controlled to be 20 times, R3 may be set to 2.6k Ω. Through the design of the signal amplifying circuit 20, the weak electromyographic signals can be differentially amplified, so that the further processing of subsequent circuits and the readability of the signals are facilitated.

Referring to fig. 1, the filter-up circuit 30 includes a high-pass filter circuit 31, a low-pass filter circuit 32, a level-up circuit 33, and a power frequency notch circuit 34; the input end of the high-pass filter circuit 31 is the input end of the filter lifting circuit 30, the output end of the high-pass filter circuit 31 is connected with the input end of the low-pass filter circuit 32, the output end of the low-pass filter circuit 32 is connected with the input end of the level lifting circuit 33, the output end of the level lifting circuit 33 is connected with the input end of the power frequency notch circuit 34, and the output end of the power frequency notch circuit 34 is the output end of the filter lifting circuit 30.

The structures of the high-pass filter circuit 31, the low-pass filter circuit 32, the level boost circuit 33, and the power frequency notch circuit 34 may be set according to actual needs. In this embodiment, referring to fig. 1 to 3, the high pass filter circuit 31 may include a third capacitor C3, a fourth capacitor C4, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and a first operational amplifier U2; the non-inverting input end of the first operational amplifier U2 is connected to the output end of the signal amplifying circuit 20 through a third capacitor C3 and a fourth capacitor C4 in sequence, the inverting input end of the first operational amplifier U2 is connected to the GND through a fourth resistor R4, the inverting input end of the operational amplifier is further connected to the output end of the first operational amplifier U2 through a fifth resistor R5, a junction point where the third capacitor C3 and the fourth capacitor C4 are connected is further connected to the output end of the first operational amplifier U2 through a sixth resistor R6, and the forward input end of the first operational amplifier U2 is further connected to the GND through the seventh resistor R7.

The first operational amplifier U2 may adopt an AD8672 chip of the american ADI company, where the AD8672 chip has a high-precision low-noise characteristic, and forms a second-order high-pass voltage-controlled filter by combining with the third capacitor C3, the fourth capacitor C4, the sixth resistor R6, and the seventh resistor R7, and after the muscle electrical signal subjected to differential amplification is connected to the high-pass filter circuit 31, the low-frequency signal and the dc component superimposed on the muscle electrical signal can be filtered. For example, the cut-off frequency of the circuit may be designed to be 10Hz, i.e. low-frequency signals below 10Hz are filtered, the resistances of the corresponding sixth resistor R6 and the seventh resistor R7 may be set to 16k Ω, and the capacitance values of the third capacitor C3 and the fourth capacitor C4 may be set to 1 uF. When the gain is set to be 1.5 times, the resistances of the fourth resistor R4 and the fifth resistor R5 may be set to be 20K Ω and 10K Ω, respectively, i.e., the gain K is 1+10K Ω/20K Ω is 1.5 times. Through the design of the high-pass filter circuit 31, low-frequency signals and direct-current components superposed on the electromyographic signals can be filtered out, and interference is reduced.

Referring to fig. 1 to 4, the low pass filter circuit 32 may include a fifth capacitor C5, a sixth capacitor C6, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, and a second operational amplifier U3; the non-inverting input end of the second operational amplifier U3 is connected to the output end of the high-pass filter circuit 31 through the eighth resistor R8 and the ninth resistor R9 in sequence, and the non-inverting input end of the second operational amplifier U3 is further connected to the GND through a fifth capacitor C5; the inverting input terminal of the second operational amplifier U3 is connected to the ground GND through the tenth resistor R10, and the inverting input terminal of the second operational amplifier U3 is further connected to the output terminal of the second operational amplifier U3 through the eleventh resistor R11; one end of the sixth capacitor C6 is connected to the output end of the second operational amplifier U3, and the other end of the sixth capacitor C6 is connected to the junction of the eighth resistor R8 and the ninth resistor R9; the output terminal of the second operational amplifier U3 is the output terminal of the low pass filter circuit 32.

The second operational amplifier U3 may adopt an AD8672 chip of the american ADI company, where the AD8672 chip has a high-precision low-noise characteristic, and combines with a fifth capacitor C5, a sixth capacitor C6, an eighth resistor R8, and a ninth resistor R9 to form a second-order low-pass voltage-controlled filter, and after the electromyographic signals sequentially subjected to differential amplification and high-pass filtering are input to the input terminal of the low-pass filter circuit 32, the high-frequency pulse noise superimposed on the electromyographic signals may be filtered, and the high-frequency pulse noise may be caused by clothing discharge, a power supply, or external space interference. For example, the cut-off frequency of the low pass filter circuit 32 may be set to 513Hz, and the gain may be set to 1.5 times, that is, the resistances of the eighth resistor R8 and the ninth resistor R9 may be set to 3.1k Ω, and the capacitances of the fifth capacitor C5 and the sixth capacitor C6 may be 100 nF. By the design of the low-pass filter circuit 32, high-frequency clutter signals superimposed on the electromyographic signals can be filtered out, and interference is reduced.

Referring to fig. 1 to 5, the level-up circuit 33 includes a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14 and a third operational amplifier U4; the first power supply V1 access end of the third operational amplifier U4 is connected with a third power supply V3, and the second power supply V2 access end of the third operational amplifier U4 is connected with a fourth power supply V4; the inverting input end of the third operational amplifier U4 is grounded GND; a non-inverting input terminal of the third operational amplifier U4 is connected to an output terminal of the low pass filter circuit 32 through the twelfth resistor R12, a non-inverting input terminal of the third operational amplifier U4 is connected to an output terminal of the third operational amplifier U4 through the thirteenth resistor R13, and a non-inverting input terminal of the third operational amplifier U4 is further connected to the second power supply V2 input terminal of the third operational amplifier U4 through the fourteenth resistor R14; the output terminal of the third operational amplifier U4 is the output terminal of the level-up circuit 33.

The third operational amplifier U4 may be an AD8672 chip manufactured by ADI, usa, which has high precision and low noise. The third power source V3 and the first power source V1 may be a power source, i.e., a voltage of +5V, and the fourth power source V4 and the second power source V2 may be a power source, i.e., a voltage of-5V. The thirteenth resistor R13 is used for level shifting, and together with the fourteenth resistor R14, determines the amplification factor of the level-up circuit 33. It can be understood that, when the differential signal collection is performed through the surface electrode, the collected electromyographic signals have both positive voltage and negative voltage, and the same-phase adder can be formed by the third operational amplifier U4, so as to perform level lifting on the electromyographic signals after signal amplification and high-low pass filtering, so that the voltage amplitude is integrally improved, and the collection by a subsequent main control chip is facilitated.

Referring to fig. 1 to 6, the power frequency notch circuit 34 includes a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a fourth operational amplifier U5, and a fifth operational amplifier U6; a non-inverting input terminal of the fourth operational amplifier U5 is sequentially connected to the output terminal of the level-up circuit 33 through the seventh capacitor C7 and the eighth capacitor C8, and a non-inverting input terminal of the fourth operational amplifier U5 is further sequentially connected to the output terminal of the level-up circuit 33 through the fifteenth resistor R15 and the sixteenth resistor R16; the inverting input end of the fourth operational amplifier U5 is connected to the non-inverting input end of the fifth operational amplifier U6 through the seventeenth resistor R17, and the output end of the fourth operational amplifier U5 is the output end of the power frequency notch circuit 34; the non-inverting input terminal of the fifth operational amplifier U6 is further connected to GND through the eighteenth resistor R18, the inverting input terminal of the fifth operational amplifier U6 is connected to the output terminal of the fifth operational amplifier U6, the output terminal of the fifth operational amplifier U6 is further connected to one end of the ninth capacitor C9 and one end of the nineteenth resistor R19, the other end of the ninth capacitor C9 is connected to a node where the fifteenth resistor R15 and the sixteenth resistor R16 are connected, and the other end of the nineteenth resistor R19 is connected to a node where the seventh capacitor C7 and the eighth capacitor C8 are connected.

The fourth operational amplifier U5 and the fifth operational amplifier U6 may be AD8672 chips of the american ADI company, which have high precision and low noise characteristics, and constitute a double-T active trap as a main operating electronic component, and the level-lifted electromyographic signals are connected to the input end of the power frequency trap circuit 34, so that 50Hz power frequency interference superimposed on the electromyographic signals is filtered out, and the anti-interference performance of the digital EMG electromyographic signal acquisition circuit is enhanced.

Finally, the a/D (analog to digital) acquisition end of the control chip 40 is used as the acquisition end of the control chip 40 to acquire the electromyographic signals to be processed waiting for operation. The scheme can adopt a 32-bit singlechip STM32F373 of an ideographic semiconductor, the main frequency of the chip can be 72MHz, 16-bit A/D conversion is carried out, the electromyographic signals to be processed can be converted into digital signals from analog signals, the obtained digital signals are time-domain electromyographic signals, and then the electromyographic signals represented by the digital signals are subjected to rectification integration operation through an algorithm program to obtain the frequency-domain electromyographic signals.

Above-mentioned scheme carries out operational amplifier and instrument amplifier U1 configuration through integrated chip, and the integrated level is higher, can help EMG flesh electric signal digital acquisition circuit to realize the miniaturization, convenient research and use widely.

Further, referring to fig. 1, fig. 7 and fig. 8, the above-mentioned digital EMG electromyogram signal acquisition circuit may further include a shielding housing, and circuit modules such as the signal amplification circuit 20, the filter lifting circuit 30 and the control chip 40 except for the signal acquisition terminal 10 may be disposed in the shielding housing. This shielding shell can use all-metal detachable construction, makes things convenient for the maintenance in later stage when whole anti external disturbance.

The shielding shell can be reserved with a communication interface and a power input interface, wherein the communication interface can be an RS232 communication interface. A communication isolation circuit 50 may be further provided, the communication interface is connected to one end of the communication isolation circuit 50, and the other end of the communication isolation circuit 50 is connected to the control chip 40. The serial port of the control chip 40 can communicate with the outside through the communication isolation circuit 50, and the time domain electromyographic signal and the frequency domain electromyographic signal which are processed by the operation are sent to the outside. The communication isolation circuit 50 may be a digital isolator chip SI8642BD from the american core company, with an isolation voltage up to 5 kV.

An external power supply can be connected into the EMG electromyographic signal digital acquisition circuit through the power input interface and the power isolation circuit 60 to supply power for the internal circuit. Taking the working voltage of the power supply as +5V or-5V as an example, referring to fig. 8, the power supply isolation circuit 60 can be formed by an isolated voltage-stabilizing positive-negative dual-output module power supply IE0505KS of Jinshengyang company, the IE0505KS module power supply is packaged by a small SMD chip, and the isolation voltage is up to 3 kVDC. The power isolation circuit 60 can isolate the direct current input voltage, and the anti-interference capability is enhanced. In addition, a capacitor is connected between the input/output end of the power isolation circuit 60 and the ground GND for filtering and reducing interference.

The invention also provides an EMG electric signal digital acquisition system, which comprises an EMG electric signal digital acquisition circuit, and the structure of the EMG electric signal digital acquisition circuit can refer to the embodiment, and is not described herein again. Preferably, the digital EMG signal acquisition system of the embodiment adopts the technical scheme of the digital EMG signal acquisition circuit, so the digital EMG signal acquisition system has all the beneficial effects of the digital EMG signal acquisition circuit.

The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.