Functional electrical stimulation method and electrical stimulation system based on fuzzy control

Abstract

The invention provides a functional electrical stimulation method and system based on fuzzy control, and the method comprises the steps: applying an electrical stimulation signal with an initial electrical stimulation parameter to the muscle of a to-be-stimulated point of a patient, and obtaining an electromyographic signal in the process of applying the electrical stimulation to the muscle of the to-be-stimulated point; performing data processing on the acquired electromyographic signals to extract time-frequency domain features corresponding to the electromyographic signals, and analyzing to obtain root-mean-square values of the electromyographic signals and median frequencies of electromyographic signal power spectrums to represent the strength and fatigue degree of the electromyographic signals; and obtaining real-time electrical stimulation time according to the intensity of the electromyographic signals and the fatigue degree and based on a preset fuzzy control strategy, and performing electrical stimulation rehabilitation on the muscles of the patient according to the electrical stimulation time. The purpose of automatically controlling the electrical stimulation time can be achieved, the control efficiency is improved, the intelligent rehabilitation training of a patient can be assisted, and then the good rehabilitation effect is achieved.

Description

Technical Field

[0001] This application belongs to the technical field of rehabilitation medical equipment, and particularly relates to a functional electrical stimulation method and an electrical stimulation system based on fuzzy control. Background Art

[0002] In recent years, the fast-paced lifestyle and the trend of the aging national population have led to a continuous increase in the number of stroke patients and the number of patients suffering from lower limb motor dysfunction after stroke, which not only reduces the quality of life of patients but also brings a heavy economic burden. Stroke and the resulting upper limb motor dysfunction have become important factors affecting national health since the new century.

[0003] Functional electrical stimulation is a rehabilitation technique that stimulates nerves or muscles through electric current to assist or restore the motor function of patients, and is widely used in the rehabilitation treatment of stroke patients. Traditional functional electrical stimulation systems usually use fixed parameters for control, and their treatment plans are formulated based on the initial assessment results of patients, lacking the ability of dynamic adjustment.

[0004] To improve the adaptability of functional electrical stimulation systems, some feedback control mechanisms such as triggering stimulation through the amplitude threshold of electromyogram (EMG) signals can only achieve simple on-off control and cannot optimize the stimulation time; using proportional-integral-derivative algorithms to adjust the stimulation intensity has limited response effects on the non-linear human physiological system and is prone to overshoot or oscillation.

[0005] Although the above methods have improved the flexibility of functional electrical stimulation systems to a certain extent, problems such as multi-parameter coupling optimization and fuzzy decision-making still exist. Factors such as muscle fatigue, movement intention, and environmental interference affect each other and are difficult to describe through precise mathematical models. Summary of the Invention

[0006] In view of this, this application aims to propose a functional electrical stimulation method and an electrical stimulation system based on fuzzy control to solve at least one of the above problems.

[0007] To achieve the above object, the technical solution of this application is realized as follows: In a first aspect, this application provides a functional electrical stimulation method based on fuzzy control, including: Applying an electrical stimulation signal with initial electrical stimulation parameters to the muscle at the point to be stimulated of the patient, and obtaining the electromyogram signal during the process of applying electrical stimulation to the muscle at the point to be stimulated; Performing data processing on the obtained electromyogram signal to extract the time-frequency domain characteristics corresponding to the electromyogram signal, and analyzing to obtain the root mean square value of the electromyogram signal and the median frequency of the power spectrum of the electromyogram signal to characterize the intensity and fatigue degree of the electromyogram signal; According to the myoelectric signal intensity and the degree of fatigue, and based on a preset fuzzy control strategy, a real-time electrical stimulation time is obtained, and electrical stimulation rehabilitation is performed on the patient's muscles according to the electrical stimulation time.

[0008] Further, a constant current electrical stimulation with adjustable frequency, pulse width, and amplitude is applied to the patient's muscles, where the current does not exceed 20% of the human safe current.

[0009] Further, an input fuzzy set is constructed according to the myoelectric signal intensity and the degree of fatigue, an output fuzzy set is constructed according to the electrical stimulation time, and a fuzzy control strategy is established, where the fuzzy control strategy is to divide the myoelectric signal intensity and the fatigue intensity into multiple levels to obtain a fuzzy quantity of the electrical stimulation time with different durations; The defuzzification process is performed on the fuzzy quantity of the electrical stimulation time by using the membership function to obtain a real-time electrical stimulation time.

[0010] Further, the membership function formula is: ; In the formula, is the output electrical stimulation time, is the membership function of the electrical stimulation time.

[0011] In a second aspect, based on the same inventive concept, the present application further provides an electrical stimulation system for implementing a functional electrical stimulation method based on fuzzy control as described in the first aspect. The system includes two parts: a host computer and a slave computer. The slave computer includes a power supply module, an electromyogram acquisition module, a constant current electrical stimulation module, and a communication module. The host computer includes an image display module, a signal processing module, a parameter setting module, and a fuzzy control module; Among them, the power supply module is used to provide power supply for each module of the system. The electromyogram acquisition module is used to acquire the electromyogram signal at the muscle of the patient being stimulated. The constant current electrical stimulation module is used to provide a stimulation current with adjustable current frequency, pulse width, and amplitude. One electromyogram acquisition channel corresponds to one electrical stimulation channel. The communication module is communicatively connected to the host computer through a communication interface; The image display module is used to display the waveform of the acquired electromyogram signal. The parameter setting module is used to adjust the output parameters of the constant current electrical stimulation module and the serial communication parameters, and transmit them to the constant current electrical stimulation module and the electromyogram acquisition module through the communication interface. The data processing module is used to process the acquired electromyogram signal to obtain the root mean square value of the electromyogram signal and the median frequency of the electromyogram signal power spectrum to characterize the electromyogram signal intensity and the degree of fatigue. The fuzzy control module is used to receive the electromyogram signal intensity and the degree of fatigue to dynamically adjust the electrical stimulation time.

[0012] Further, the constant current electrical stimulation module includes a constant current circuit, which is composed of a programmable digital potentiometer and a constant current source chip connected in series. The programmable digital potentiometer is connected to the single-chip microcomputer, and the constant current source chip is connected to the human body resistance through an electrode sheet to provide a constant current.

[0013] Further, the constant current electrical stimulation module further includes an adjustment circuit, which is composed of two switching tubes, including a first switching tube and a second switching tube. The source electrode of the first switching tube is connected to the power supply terminal. The gate electrode of the first switching tube is connected to its source electrode through a first resistor and to the drain electrode of the second switching tube through a second resistor. The drain electrode of the first switching tube serves as the output terminal and is connected to the human body resistance through an electrode sheet. The gate electrode of the second switching tube is connected to the single-chip microcomputer through a third resistor to receive a PWM signal. A fourth resistor is connected between the gate electrode and the source electrode of the second switching tube, and the gate electrode of the second switching tube is grounded.

[0014] Further, the first switching tube is a P-type MOS tube, and the second switching tube is an N-type MOS tube.

[0015] Compared with the prior art, the functional electrical stimulation method and electrical stimulation system based on fuzzy control according to the present application have the following beneficial effects: The functional electrical stimulation method and electrical stimulation system based on fuzzy control according to the present application collect surface electromyogram signals of the upper limb and analyze the time-frequency domain characteristics of the electromyogram signals under electrical stimulation conditions, and use fuzzy control to dynamically output the electrical stimulation time, so as to achieve the purpose of automatically controlling the electrical stimulation time, improve the control efficiency, assist patients to achieve intelligent rehabilitation training, and thus achieve good rehabilitation effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings: Figure 1 is a flowchart of a functional electrical stimulation method based on fuzzy control according to an embodiment of this application; Figure 2 is a simplified schematic diagram of a constant current electrical stimulation circuit according to an embodiment of this application; Figure 3 is a constant current output circuit diagram according to an embodiment of this application; Figure 4 is a circuit diagram for adjusting the current frequency and pulse width according to an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions, and advantages of this application more clear and understandable, the following further elaborates on this application in detail with reference to specific embodiments and the accompanying drawings.

[0018] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the embodiments of this application should have the ordinary meanings understood by those with ordinary skills in the field to which this application belongs. The "first", "second", and similar terms used in the embodiments of this application do not denote any order, quantity, or importance, but are only used to distinguish different components. The terms such as "include" or "comprise" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms such as "connect" or "couple" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0019] Please refer to Figure 1 As shown, this embodiment provides a functional electrical stimulation method based on fuzzy control, which specifically includes the following steps: Step S101: Apply an electrical stimulation signal with initial electrical stimulation parameters to the muscle at the point to be stimulated of the patient, and acquire the electromyogram signal during the process of applying electrical stimulation to the muscle at the point to be stimulated.

[0020] Specifically, in this embodiment, appropriate stimulation sites of the upper limb muscles of the patient are selected, and a constant current electrical stimulation with adjustable frequency, pulse width, and amplitude is applied. Among them, the current shall not exceed 20% of the human safety current.

[0021] This embodiment uses four-channel electromyogram acquisition and four-channel constant current electrical stimulation. One acquisition channel corresponds to one stimulation channel. Among them, the performance indicators of electromyogram acquisition are: sampling rate 1000Hz, amplification factor 1000 times, signal-to-noise ratio 60dB; the performance indicators of constant current electrical stimulation are: frequency 0 - 200Hz, resolution 1Hz; amplitude 0 - 50mA, resolution 1mA; pulse width 0 - 1000 , resolution 10 , the pulse waveform is a unipolar PWM wave, and the current amplitude, pulse width, and frequency of each channel can be independently adjusted.

[0022] Compared with single-channel electrical stimulation, during compound movement training, multi-channels can simultaneously activate and monitor the activities of multiple muscle groups, improving the efficiency and effectiveness of rehabilitation training. At the same time, the constant-current electrical stimulation adopted can independently adjust the electrical stimulation parameters of each channel, which enables personalized adjustment according to the characteristics and needs of each muscle group during training or rehabilitation, and customize personalized treatment plans.

[0023] Step S102: Process the acquired myoelectric signals to extract the time-frequency domain features corresponding to the myoelectric signals, and analyze to obtain the root mean square value of the myoelectric signals and the median frequency of the myoelectric signal power spectrum, so as to characterize the myoelectric signal intensity and fatigue degree.

[0024] Specifically, in this embodiment, the acquired myoelectric signals are processed by denoising, extracting time-frequency domain features, and analyzing to obtain the root mean square value and the median frequency of the myoelectric signal power spectrum, which are used to characterize the myoelectric signal intensity and fatigue degree, and the two are used as the inputs of the fuzzy controller.

[0025] Step S103: According to the myoelectric signal intensity and fatigue degree, and based on a preset fuzzy control strategy, obtain the real-time electrical stimulation time, and perform electrical stimulation rehabilitation on the patient's muscles according to the electrical stimulation time.

[0026] In some embodiments, an input fuzzy set is constructed according to the myoelectric signal intensity and fatigue degree, an output fuzzy set is constructed according to the electrical stimulation time, and a fuzzy control strategy is established. Among them, the fuzzy control strategy is to divide the myoelectric signal intensity and fatigue intensity into multiple levels to obtain fuzzy quantities of electrical stimulation time with different durations; The fuzzy quantity of the electrical stimulation time is defuzzified by using the membership function to obtain the real-time electrical stimulation time.

[0027] Specifically, in this embodiment, the input fuzzy set includes: weak myoelectric signal intensity (NE), moderate myoelectric signal intensity (ME), strong myoelectric signal intensity (PE), weak fatigue degree (NF), moderate fatigue degree (MF), and strong fatigue degree (PF).

[0028] The output fuzzy set includes: very short electrical stimulation time (VS), short electrical stimulation time (S), moderate electrical stimulation time (M), long electrical stimulation time (L), and very long electrical stimulation time (VL).

[0029] The established fuzzy control strategy is as follows: If the myoelectric signal intensity is weak and the fatigue degree is weak, then the electrical stimulation time is very long; If the myoelectric signal intensity is moderate and the fatigue degree is moderate, then the electrical stimulation time is moderate; If the myoelectric signal intensity is strong and the fatigue degree is strong, then the electrical stimulation time is very short; If the EMG signal intensity is weak and the fatigue level is moderate, the electrical stimulation time is moderate; If the EMG signal intensity is strong and the fatigue level is weak, the electrical stimulation time is moderate; If the EMG signal intensity is moderate and the fatigue level is weak, the electrical stimulation time is short; If the EMG signal intensity is weak and the fatigue level is strong, the electrical stimulation time is long; If the EMG signal intensity is moderate and the fatigue level is strong, the electrical stimulation time is long; If the EMG signal intensity is strong and the fatigue level is moderate, the electrical stimulation time is long.

[0030] According to the fuzzy control rules, a fuzzy control table is established as follows: In addition, the input and output membership functions set are both triangular membership functions. Specifically, the triangular membership function has a peak within its domain, and on both sides of the peak, the membership degree gradually decreases until it reaches zero. The advantage of the triangular membership function is that it is computationally simple, easy to understand, and can effectively represent the fuzziness of input and output variables. In the design of a fuzzy controller, using the triangular membership function can ensure that the system can smoothly perform reasoning and decision-making when dealing with uncertainty and fuzziness. At the same time, the use of the triangular membership function also makes the controller have strong robustness and stability, and can adapt to changes in different environments.

[0031] Since both the input and output of the fuzzy reasoning process are fuzzy variables, the obtained electrical stimulation time is a fuzzy quantity. In order to convert this fuzzy quantity into an actual available precise value, defuzzification processing must be carried out. The method adopted in the present invention is to obtain the precise electrical stimulation time by the centroid method, that is, taking the centroid of the area enclosed by the membership function curve and the abscissa as the output value of the fuzzy reasoning. The specific formula is as follows: In the formula, is the output electrical stimulation time, is the membership function of the electrical stimulation time.

[0032] A functional electrical stimulation method based on fuzzy control described in this embodiment collects the surface EMG signals of the upper limb and analyzes the time-frequency domain characteristics of the EMG signals under electrical stimulation conditions, dynamically outputs the electrical stimulation time by using fuzzy control, realizes the purpose of automatically controlling the electrical stimulation time, improves the control efficiency, can assist patients to achieve intelligent rehabilitation training, and thus achieves good rehabilitation effects.

[0033] Based on the same inventive concept, corresponding to the method of any of the above embodiments, an embodiment of the present application also provides a functional electrical stimulation system based on fuzzy control.

[0034] The electrostimulation system is divided into two parts: the upper computer and the lower computer. The lower computer includes a power supply module, an electromyogram (EMG) acquisition module, a constant-current electrostimulation module, and a communication module. The upper computer includes an image display module, a signal processing module, a parameter setting module, and a fuzzy control module.

[0035] Among them, the power supply module is used to supply power to each module of the system. The EMG acquisition module is used to acquire the EMG signals at the muscles of the subject patient being stimulated. The functional electrostimulation module can provide a stimulation current with variable current amplitude, pulse width, and frequency. One EMG acquisition channel corresponds to one electrostimulation channel. The communication module is connected to the upper computer through a communication interface (in this embodiment, a USB communication interface is used). The image display module of the upper computer is used to display the waveform of the acquired EMG signals. The parameter setting module can adjust the three output parameters of the constant-current electrostimulation module and the serial communication parameters, and transmit them to the constant-current electrostimulation module and the EMG acquisition module of the lower computer through the USB communication interface. The signal processing module can filter and extract features from the acquired EMG signals. The fuzzy control module is a single-variable two-dimensional fuzzy controller that receives the EMG signal intensity and fatigue degree and dynamically adjusts the electrostimulation time to achieve personalized rehabilitation treatment.

[0036] The EMG acquisition module is used to obtain the EMG signals when the muscles are electrostimulated. The real-time captured EMG signals will be displayed on the image display module of the upper computer so that the subject and the staff can understand the state of the stimulated muscles. When designing the EMG acquisition module, a bipolar amplifier circuit, a second-order Butterworth filter circuit, a signal conditioning circuit, and a 50Hz power frequency notch filter circuit are considered to obtain pure EMG signals.

[0037] The power supply module uses a 12V power supply. The microcontroller uses an STM32 single-chip microcomputer. According to the power supply requirements of other circuits and the main control chip, a voltage regulator is used to stably output 3.3V voltage to supply power to the single-chip microcomputer, and 40V voltage is used to supply power to the constant-current circuit.

[0038] The communication module enables the system to communicate serially between the upper computer and the lower computer through the Universal Serial Bus (USB), so that the upper computer can transmit data and interact with commands with the lower computer through the USB interface. This communication process uses a USB-to-serial adapter to enable the upper computer to establish a connection with the serial device of the lower computer for data reading, command sending, and real-time feedback.

[0039] The constant-current electrostimulation module is used to provide an accurate control current. Figure 2It is a simple schematic diagram of a constant-current electrical stimulation circuit. The PWM wave with adjustable frequency and pulse width output by the STM32 single-chip microcomputer controls the turn-off of the MOS transistor. A 40V voltage input, MOS transistor, human body resistance, constant-current circuit, and GND form a loop. Due to the existence of the constant-current source chip, the current on this loop is equal everywhere. The constant-current circuit of this system is as shown in Figure 3 shown. U1 is a programmable digital potentiometer, and its output resistance can be changed through programming. The output resistance of the potentiometer is connected to pin 1 of U2. U2 is a constant-current source chip used to output the constant current of this system. The constant-current output formula is: In the formula, I is the output current, is the output resistance of the programmable digital potentiometer.

[0040] The frequency and pulse width adjustment circuit is as shown in Figure 4 shown. For the pulse modulation part, two field-effect transistors, VN2222LL (N-channel MOSFET) and SI2309 (P-channel MOSFET), are used to implement it. The specific connection relationship is as follows: The source of the first switching transistor Q1 is connected to the power supply terminal. The gate of the first switching transistor Q1 is connected to its source through the first resistor R1 and to the drain of the second switching transistor Q2 through the second resistor R2. The drain of the first switching transistor Q1 is used as the output terminal and is connected to the human body resistance through the electrode patch. The gate of the second switching transistor Q2 is connected to the single-chip microcomputer through the third resistor R3 to receive the PWM signal. A fourth resistor R4 is connected between the gate and the source of the second switching transistor Q2, and the gate of the second switching transistor Q2 is grounded.

[0041] Specifically, the PWM signal generated by the single-chip microcomputer is generated by the TIME timer module of the single-chip microcomputer and indirectly regulates the state of SI2309 by controlling the gate (G pole) of VN2222LL, thereby realizing the precise adjustment of the output pulse width and frequency.

[0042] Among them, the drain of the MOS transistor Q1 is connected to the connected human body resistance, and the constant-current source is connected below. The constant-current source outputs current for electrical stimulation. When the Q1 device is connected, the entire circuit is turned on (as shown in Figure 2 ), under the action of the constant-current source, the current of the entire circuit is the specified constant-current value. When the Q1 device is disconnected, the entire circuit is disconnected and no current passes through. The frequency and pulse width are controlled by controlling the on-off of the Q1 device.

[0043] The host computer part includes an image display module, a signal processing module, a parameter setting module, and a fuzzy control module. In the parameter setting module, the electrostimulation parameters can be controlled. In the image display module, the system can display the collected waveforms of the current subject in real time, helping the subject and the staff to visually observe the real-time state of the signal. This module supports multiple waveform display formats, including time-domain waveforms and frequency-domain waveforms. The signal processing module undertakes the further processing task of the collected signal. First, the original signal is denoised to remove unnecessary components introduced by environmental interference or equipment noise. Then, the signal processing module extracts the time-frequency domain features of the signal, including the integral electromyogram value, root mean square, and zero-crossing points in the time domain, and indicators such as average power, median frequency, and power spectral density in the frequency domain. The electromyogram signal intensity and fatigue degree characterized by the root mean square value and median frequency are used as the input of the fuzzy control module, and the output of the fuzzy controller is the electrostimulation time, achieving the purpose of dynamically adjusting the electrostimulation time.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

[0045] The embodiments of the present application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the embodiments of the present application shall be included in the protection scope of the present application.

Claims

1. A functional electrical stimulation method based on fuzzy control, characterized in that: include: Applying an electrical stimulation signal with initial electrical stimulation parameters to the muscles at the patient's stimulation points, and obtaining myoelectric signals during the electrical stimulation process of the muscles at the stimulation points; Performing data processing on the acquired electromyographic signal to extract the time-frequency domain features corresponding to the electromyographic signal, and analyzing to obtain the root mean square value of the electromyographic signal and the median frequency of the electromyographic signal power spectrum to characterize the electromyographic signal strength and fatigue degree; According to the intensity of the electromyographic signal and the degree of fatigue, and based on a preset fuzzy control strategy, a real-time electrical stimulation time is obtained, and electrical stimulation rehabilitation is performed on the patient's muscles according to the electrical stimulation time.

2. The method according to claim 1, characterized in that: Apply constant current electrical stimulation with adjustable frequency, pulse width and amplitude to the patient's muscles, where the current does not exceed 20% of the safe current for the human body.

3. The method according to claim 1, characterized in that: An input fuzzy set is constructed according to the strength of the electromyographic signal and the degree of fatigue, an output fuzzy set is constructed according to the electrical stimulation time, and a fuzzy control strategy is established, wherein the fuzzy control strategy is to divide the strength of the electromyographic signal and the fatigue intensity into multiple levels to obtain fuzzy quantities of the electrical stimulation time with different durations; The membership function is used to perform defuzzification processing on the fuzzy quantity of the electrical stimulation time to obtain the real-time electrical stimulation time.

4. The method according to claim 3, characterized in that The membership function formula is: ； In the formula, is the output electrical stimulation time, is the membership function of the electrical stimulation time.

5. An electrical stimulation system for implementing a functional electrical stimulation method based on fuzzy control as claimed in any one of claims 1 to 4, characterized in that: The system includes a host computer and a slave computer. The slave computer includes a power module, an electromyography acquisition module, a constant current electrical stimulation module and a communication module. The host computer includes an image display module, a signal processing module, a parameter setting module and a fuzzy control module. Among them, the power supply module is used to provide power supply to each module of the system, the electromyography acquisition module is used to collect electromyography signals of the stimulated muscles of the patient, the constant current electrical stimulation module is used to provide a stimulation current with adjustable current frequency, pulse width and amplitude, one electromyography acquisition channel corresponds to one electrical stimulation channel, and the communication module is connected to the host computer through a communication interface; The image display module is used to display the collected electromyographic signal waveform, the parameter setting module is used to adjust the output parameters and serial port communication parameters of the constant current electrical stimulation module, and transmit them to the constant current electrical stimulation module and the electromyographic acquisition module through the communication interface, the data processing module is used to process the collected electromyographic signal to obtain the root mean square value of the electromyographic signal and the median frequency of the electromyographic signal power spectrum to characterize the electromyographic signal strength and fatigue degree, and the fuzzy control module is used to receive the electromyographic signal strength and fatigue degree to dynamically adjust the electrical stimulation time.

6. The system according to claim 5, characterized in that: The constant current electrical stimulation module includes a constant current circuit, and the constant current is composed of a programmable digital potentiometer and a constant current source chip connected to each other. The programmable digital potentiometer is connected to a single-chip microcomputer, and the constant current source chip is connected to a human body resistor through an electrode sheet to provide a constant current.

7. The system according to claim 5, characterized in that: The constant current electrical stimulation module also includes a regulating circuit, which is composed of two switch tubes, including a first switch tube and a second switch tube, the source of the first switch tube is connected to the power supply end, the gate of the first switch tube is connected to its source through a first resistor and to the drain of the second switch tube through a second resistor, the drain of the first switch tube is used as an output end, and is connected to the human body resistor through an electrode sheet; The gate of the second switch tube is connected to the single chip microcomputer via a third resistor to receive a PWM signal. A fourth resistor is connected between the gate of the second switch tube and its source. The gate of the second switch tube is grounded.

8. The system according to claim 7, characterized in that: The first switch tube is a P-type MOS tube, and the second switch tube is an N-type MOS tube.

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