Percutaneous spinal nerve electrical stimulation system and method

Abstract

The invention relates to the technical field of exercise rehabilitation, and discloses a percutaneous spinal nerve electrical stimulation system and method, and the system comprises a power module which is used for converting an external alternating current into a stabilized power supply; the MCU module controls the pulse signal generation module; the pulse signal generation module is used for generating an electrical stimulation waveform; the DAC module receives the digital signal; the modulation module is used for receiving analog signals; the amplification module is used for receiving modulation waveforms; the multi-channel gating module is used for distributing stimulation current to a plurality of channels; the current detection module monitors the magnitude of current output by each channel in real time; and the ADC module performs digital conversion on the current analog signal output by the electrical stimulator. According to the invention, multi-channel and real-time modulation electrical stimulation signals can be output through modulation of two paths of stimulation signals, spinal cord sensory nerves are activated through the non-invasive epidermal electrode, amputation hand feeling is induced, the defect that electromyographic signals are interfered by the tail end of a stump in the prior art is improved, and the accuracy of an electromyographic signal decoding algorithm is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sports rehabilitation, and in particular to a transcutaneous spinal cord electrical stimulation system and method. Background Art

[0002] Myoelectric prosthetic hands are a representative innovative method for the application of neuroengineering technology in the field of amputee motor rehabilitation, which can reconstruct some hand motor functions for amputees. However, due to the lack of effective sensory feedback in prosthetic hands on the market, some amputees rarely or refuse to use myoelectric prosthetic hands. Therefore, it is very necessary to provide sensory feedback for myoelectric prosthetic hands.

[0003] Currently, the main way to induce artificial sensation is neuromuscular electrical stimulation (NMES), which applies electrical stimulation to the skin or muscles at the end of the residual limb to induce sensation, and has been applied to sensory feedback of prosthetic hands.

[0004] However, electrical stimulation causes the control signal of the prosthetic hand - the electromyographic signal to be mixed with interference artifacts, affecting the accuracy of electromyographic decoding. At the same time, patients with complete upper limb amputation do not have a suitable electrical stimulation position and cannot implement electrical stimulation to induce sensation, which has become a key technical link that needs to be solved in the current field of prosthetic hand research. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a transcutaneous spinal cord electrical stimulation system and method to solve the above technical problems.

[0006] In a first aspect, a transcutaneous spinal cord electrical nerve stimulation system and method are provided, including: a power supply module, an MCU module, a pulse signal generation module, a DAC module, a modulation module, an amplification module, a multi-channel gating module, a current detection module and an ADC module;

[0007] The power supply module is used to convert external alternating current into a regulated power supply to supply power to other modules in the system;

[0008] The MCU module controls the pulse signal generating module by sending a logic control signal;

[0009] The pulse signal generating module is used to generate an electrical stimulation waveform and send it to the DAC module;

[0010] The DAC module receives the digital signal from the pulse signal generating module and converts it into an analog signal;

[0011] The modulation module is used to receive the analog signal output by the DAC module, modulate it, and input the modulated waveform into the amplification module;

[0012] The amplification module is used to receive the modulation waveform output by the modulation module, and amplify it by a threshold amplitude to form a final current signal;

[0013] The multi-channel gating module is used to distribute the amplified stimulation current to multiple channels;

[0014] The current detection module monitors the current output by each channel in real time and inputs it to the ADC module;

[0015] The ADC module performs digital conversion on the analog signal of the electric stimulator output current detected by the current detection module, and the converted digital signal is input into the MCU module.

[0016] Furthermore, the main control chip of the MCU module is STM32F103, which controls the generation of subsequent electrical stimulation waveforms by controlling the pulse signal generation module, and at the same time receives the output stimulation current detected by the current detection module fed back by the ADC module.

[0017] Furthermore, the pulse signal generating module adopts an AD9954 chip and utilizes direct digital frequency synthesis to generate a multi-channel analog sine wave signal or converts the sine wave signal into a square wave signal through an internal high-speed comparator.

[0018] Furthermore, the two channels of the DAC module can respectively output stimulation signals with independent frequency, phase and amplitude, and the MCU module can store the corresponding data in real time through the I / O parallel port.

[0019] Furthermore, the modulation module utilizes the AD633 four-image multiplier to modulate the carrier signal and the modulation signal, and outputs a final stimulation signal waveform.

[0020] Furthermore, the current detection circuit is connected in series with a load resistor, and the two ends of the resistor are output to the two input ends of the ADC module.

[0021] Furthermore, the ADC module uses the built-in ADC function of the MCU main control chip to convert the analog signal output by the current detection module into a digital signal.

[0022] Furthermore, it also includes a wireless communication module for realizing wireless data communication between the system and external devices.

[0023] In a second aspect, a method for transcutaneous spinal cord electrical stimulation is provided, based on the transcutaneous spinal cord electrical stimulation system described in any one of the above, comprising the following steps:

[0024] Initialize the circuit system and the myoelectric prosthetic hand, and set the default stimulation parameters and waveforms;

[0025] The user generates movement intention and controls the contraction of the muscles at the end of the residual limb. The myoelectric prosthetic hand collects the myoelectric signals and decodes them into control commands.

[0026] The pressure sensors on the fingers of the myoelectric prosthetic hand collect fingertip pressure signals and process them;

[0027] Design transcutaneous spinal cord stimulation signals based on the discharge characteristics of real hand sensory afferent fibers;

[0028] The contact force signal is converted into a control signal to control different channels to be in a gated state and update the electrical stimulation parameters;

[0029] The output electrical stimulation mode stimulates the sensory afferent nerves of the cervical spinal cord, induces touch and pressure sensations, and uploads them to the somatosensory cortex to form sensory feedback.

[0030] The invention adopting the above technical solution has the following advantages:

[0031] The present invention outputs multi-channel, real-time modulated electrical stimulation signals through the modulation of two-way stimulation signals, activates the spinal sensory nerves through non-invasive epidermal electrodes, and induces sensation in the amputated hand, thereby improving the deficiency of previous electrical stimulation of the residual limb end interfering with the electromyographic signal, and also improving the accuracy of the electromyographic signal decoding algorithm, and providing a suitable stimulation position and a feasible method for sensory feedback of the prosthetic hand of patients with complete upper limb amputation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation of the present invention, the following will briefly introduce the drawings required for use in the specific implementation. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0033] Figure 1 It is a schematic structural diagram of a transcutaneous spinal cord electrical stimulation system of the present invention;

[0034] Figure 2 A flow chart of a method for transcutaneous spinal cord electrical stimulation according to the present invention;

[0035] Figure 3 A characteristic diagram of sensory afferent fiber discharge in a transcutaneous spinal nerve electrical stimulation method of the present invention;

[0036] Figure 4 It is an electrical stimulation waveform diagram of transcutaneous spinal cord electrical stimulation in a transcutaneous spinal cord electrical stimulation method of the present invention;

[0037] Figure 5 This is a mathematical model diagram of the S function in a transcutaneous spinal cord electrical nerve stimulation method of the present invention. DETAILED DESCRIPTION

[0038] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0039] like Figure 1 to Figure 5 As shown, a transcutaneous spinal cord electrical stimulation system of the present invention includes: a power supply module, an MCU module, a pulse signal generation module, a DAC module, a modulation module, an amplification module, a multi-channel gating module, a current detection module and an ADC module;

[0040] The power module is used to convert external AC power into a regulated power supply to supply power to other modules in the system;

[0041] The MCU module controls the pulse signal generation module by sending logic control signals;

[0042] The pulse signal generation module is used to generate an electrical stimulation waveform and send it to the DAC module;

[0043] The DAC module receives the digital signal from the pulse signal generating module and converts it into an analog signal;

[0044] The modulation module is used to receive the analog signal output by the DAC module, modulate it, and input the modulated waveform into the amplification module;

[0045] The amplification module is used to receive the modulation waveform output by the modulation module and amplify it by a threshold value to form a final current signal;

[0046] The multi-channel gating module is used to distribute the amplified stimulation current to multiple channels;

[0047] The current detection module monitors the current output of each channel in real time and inputs it to the ADC module;

[0048] The ADC module performs digital conversion on the analog signal of the output current of the electric stimulator detected by the current detection module, and the converted digital signal is input to the MCU module.

[0049] Specifically, the power module contains a voltage stabilizing circuit, which converts the external AC power into a regulated power supply to supply the required power for other modules. The MCU module is the main control chip, which controls the pulse signal generation module through a logic control signal. The pulse signal generation module is controlled by the main control chip, generates an electrical stimulation waveform with independent frequency and voltage intensity, and sends it to the DAC module. The DAC module contains a voltage follower to improve the load capacity. One port of the DAC outputs the modulation waveform, and the other port outputs the carrier waveform. Before the output, the waveforms received by DAC1 and DAC2 are conditioned to 0~1V and -1~1V respectively, and then the two are synchronously input into the modulation module. The modulation module uses a multiplier to modulate the final stimulation waveform and input it to the amplifier module. The amplifier module includes a constant current source and a proportional amplifier. The constant current source uses a high-precision sampling resistor device to convert the voltage into a constant current and input it to the proportional amplifier module. The proportional amplifier module uses differential amplification to amplify the modulated stimulation signal to form a final modulated current signal. The multi-channel gating module uses time-division multiplexing to evenly distribute the stimulation current to multiple channels, so that users can select stimulation current output signals of multiple channels as needed. At the same time, the current detection circuit uses a high-precision small resistor in series to monitor the output current in real time and input it to the ADC module. The ADC module converts the analog signal of the output current of the electric stimulator detected by the current detection module into a digital signal, and the converted digital signal is input to the MCU module.

[0050] In some embodiments, the main control chip of the MCU module is STM32F103, which controls the generation of subsequent electrical stimulation waveforms by controlling the pulse signal generation module, and at the same time receives the output stimulation current detected by the current detection module fed back by the ADC module.

[0051] Specifically, the main control chip of the MCU module is STM32F103, which supplies 3.3V power through the power module, controls the subsequent electrical stimulation waveform generation by controlling the pulse signal generation module, and at the same time receives the output stimulation current detected by the current detection module fed back by the ADC module, thereby ensuring the stability and safety of the stimulation current.

[0052] In some embodiments, the pulse signal generation module uses an AD9954 chip to generate a multi-channel analog sine wave signal using direct digital frequency synthesis or converts the sine wave signal into a square wave signal through an internal high-speed comparator.

[0053] Specifically, the signal generation module adopts the AD9954 chip, and uses direct digital frequency synthesis to generate multi-channel analog sine wave signals or converts sine wave signals into square wave signals through internal high-speed comparators. The modulation frequency can be as high as 160MHz and the voltage amplitude is 1.8V.

[0054] In some embodiments, the amplifier module is divided into a constant current source and a proportional amplifier. The constant current source utilizes the "virtual short" principle of the operational amplifier, combines the NPN transistor and the high-precision sampling resistor device to form a voltage series negative feedback circuit, and uses the operational amplifier LM358 as a voltage follower, with an output current range of 0-10mA. The proportional amplifier module uses the LM4562 operational amplifier chip with excellent medium and low frequency performance to differentially amplify the modulated stimulation signal, amplify the stimulation current amplitude to ±90mA, and form the final modulated current signal.

[0055] In some embodiments, the multi-channel gating module uses switch gating to time-share the stimulation current, evenly distributes the output stimulation current to 2 to 4 channels, and finally selects a new output multi-channel electrical stimulation signal.

[0056] In some embodiments, the two channels of the DAC module can respectively output stimulation signals with independent frequency, phase and amplitude, and the MCU module can store the corresponding data in real time through the I / O parallel port.

[0057] Specifically, the two channels of the DAC module can output stimulation signals with independent frequency, phase and amplitude respectively, and the MCU module can store the corresponding data in real time through the I / O parallel port.

[0058] In some embodiments, the modulation module uses an AD633 four-image multiplier to modulate the carrier signal and the modulation signal, and outputs a final stimulation signal waveform.

[0059] Specifically, the modulation module uses the AD633 four-image multiplier to modulate the carrier signal and the modulation signal, and outputs the final stimulation signal waveform. The circuit of the modulation module is provided with a voltage follower to ensure that the stimulation signal is stably input to the amplifier module.

[0060] In some embodiments, the current detection circuit is connected to a load series resistor, and the output of the two ends of the resistor is connected to the two input ends of the ADC module.

[0061] Specifically, the current detection circuit connects a high-precision small resistor in series before the load, and the output of both ends of the resistor is sent to the two input ends of the operational amplifier AD629, thereby monitoring the current output size of the stimulator in real time.

[0062] In some embodiments, the ADC module uses the built-in ADC function of the MCU main control chip to convert the analog signal output by the current detection module into a digital signal.

[0063] Specifically, the ADC module is the ADC current of the MCU main control chip, which can sample the current output by the current amplifier module, and calculate the current value output by the current stimulator based on the sampled voltage, and then input it into the MCU comparison control circuit, thereby achieving safe control of the output current.

[0064] In some embodiments, a wireless communication module is also included to implement wireless data communication between the system and an external device (such as a mobile phone).

[0065] In some other embodiments, a method for transcutaneous spinal cord electrical stimulation is provided, based on any one of the transcutaneous spinal cord electrical stimulation systems described above, comprising the following steps:

[0066] Initialize the circuit system and the myoelectric prosthetic hand, and set the default stimulation parameters and waveforms;

[0067] The user generates movement intention and controls the contraction of the muscles at the end of the residual limb. The myoelectric prosthetic hand collects the myoelectric signals and decodes them into control commands.

[0068] The pressure sensors on the fingers of the myoelectric prosthetic hand collect fingertip pressure signals and process them;

[0069] Design transcutaneous spinal cord stimulation signals based on the discharge characteristics of real hand sensory afferent fibers;

[0070] The contact force signal is converted into a control signal to control different channels to be in a gated state and update the electrical stimulation parameters;

[0071] The output electrical stimulation mode stimulates the sensory afferent nerves of the cervical spinal cord, induces touch and pressure sensations, and uploads them to the somatosensory cortex to form sensory feedback.

[0072] Specifically, by selecting the multi-channel stimulation channel of the transcutaneous spinal cord stimulation system, the sensory afferent nerves of the cervical spinal cord are stimulated through the skin surface, different hand sensations of the upper limbs are induced, and the coded feedback of the contact force or grip force state of the myoelectric prosthetic hand is realized, and finally the user can perceive the state of the prosthetic hand in real time without visual assistance. The specific implementation process is as follows:

[0073] Step S01, the entire circuit system is powered on, the myoelectric prosthetic hand is initialized, each module of the transcutaneous spinal cord electrical stimulation system is initialized, and the stimulation parameters and stimulation waveform are in the default parameter state;

[0074] Step S02: The user generates a movement intention to control the contraction of the distal muscles of the residual limb. The myoelectric acquisition electrodes of the myoelectric prosthetic hand collect the myoelectric signals generated by the muscle contraction, decode the user's movement intention, convert it into a control command, and control the movement of the myoelectric prosthetic hand.

[0075] Step S03: The pressure sensors on the five fingers of the myoelectric prosthetic hand start to work, and the pressure signals of the fingertips of the myoelectric prosthetic hand are collected by the pressure signal collection system, and the pressure signals are analyzed and processed.

[0076] In order to make the sensation induced by electrical stimulation more similar to that of a real hand, a transcutaneous spinal cord stimulation signal was designed based on the discharge characteristics of the sensory afferent fibers connected to the tactile receptors when a real hand touches and grasps an object, that is, the relationship between the change in finger pressure and the discharge pattern of the sensory afferent fibers (FA sensory afferent fibers and SA sensory afferent fibers).

[0077] Among them, according to the changing relationship between the sensory afferent fiber firing rate Rate and the finger pressure F, the corresponding mathematical model formula is established as follows:

[0078] When the force of the finger contact changes, the change in the firing rate of FA-type sensory afferent fibers (dynamic force) is the main factor, and the change in the firing rate of SA-type sensory afferent fibers (static force) is the secondary factor. FA The relationship between the change of and the finger pressure F is:

[0079]

[0080] In the formula, is the contact force change rate weight (dynamic weight), k FA is the coefficient of different change modes (increase / decrease) of finger contact force, is the rate of change of finger contact force over time.

[0081] When the finger contact force remains unchanged, the change in the firing rate of SA-type sensory afferent fibers (static force) is the main factor, and the change in the firing rate of FA-type sensory afferent fibers (dynamic force) is the secondary factor. SA The relationship between the change of and the finger pressure F is:

[0082]

[0083] In the formula, is the weight of the finger contact force level, F c is the current strength level, The weight of the rate of change of finger contact force, is the rate of change of finger contact force over time.

[0084] Step S04, the contact force signal is converted into a control signal through the MCU main control chip, which controls the channels in different spatial positions to be in the selected state, and updates the amplitude, frequency, pulse width and other parameters of the electrical stimulation sequence of the transcutaneous spinal cord stimulation system. Then, the electrical stimulation pattern is output, and the sensory afferent nerves of the cervical spinal cord are stimulated through the array stimulation electrodes to induce touch and pressure sensations, which are uploaded to the somatic sensory cortex to form sensory feedback.

[0085] Taking into account the changes in the discharge patterns of sensory afferent fibers corresponding to the actual hand contact force and pressure sensation, and ensuring that the stimulation signal can penetrate the skin, spinal cord and other tissues to activate the spinal sensory afferent nerves.

[0086] Among them, the coding of the stimulation current of the transcutaneous spinal cord electrical nerve stimulation system on the contact force of the myoelectric prosthetic hand is established using the S-function mathematical model.

[0087] The specific formula of the S-function of electrical stimulation encoding the contact force of the prosthetic hand is as follows:

[0088]

[0089] Q=A 0 *f*PW*N

[0090] Among them, Q thr The minimum charge required to induce tactile perception corresponds to the minimum contact pressure F of the finger. min , Q 50 The charge required to induce the maximum tactile intensity corresponds to the maximum finger contact pressure F max , Q 50 The corresponding finger contact pressure F is half of the charge required to induce a large tactile intensity. 50 It is not necessarily half of the maximum finger contact pressure. 0 is the stimulation current intensity coefficient, f is the stimulation current modulation frequency, PW is the carrier pulse width, and N is the number of carriers in a single stimulation. At this point, the firing rate of sensory afferent fibers and the electrical stimulation frequency have established a corresponding connection, providing a more natural contact pressure feedback for the myoelectric prosthetic hand.

[0091] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. 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 included in the scope of the claims and specification of the present invention.

Claims

1. A transcutaneous spinal cord electrical stimulation system, characterized in that: include: Power module, MCU module, pulse signal generation module, DAC module, modulation module, amplification module, multi-channel gating module, current detection module and ADC module; The power supply module is used to convert external alternating current into a regulated power supply to supply power to other modules in the system; The MCU module controls the pulse signal generating module by sending a logic control signal; The pulse signal generating module is used to generate an electrical stimulation waveform and send it to the DAC module; The DAC module receives the digital signal from the pulse signal generating module and converts it into an analog signal; The modulation module is used to receive the analog signal output by the DAC module, modulate it, and input the modulated waveform into the amplification module; The amplification module is used to receive the modulation waveform output by the modulation module, and amplify it to a threshold amplitude to form a final current signal; The multi-channel gating module is used to distribute the amplified stimulation current to multiple channels; The current detection module monitors the current output by each channel in real time and inputs it to the ADC module; The ADC module performs digital conversion on the analog signal of the electric stimulator output current detected by the current detection module, and the converted digital signal is input into the MCU module.

2. A transcutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: The main control chip of the MCU module is STM32F103, which controls the generation of subsequent electrical stimulation waveforms by controlling the pulse signal generation module, and at the same time receives the output stimulation current detected by the current detection module fed back by the ADC module.

3. The transcutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: The pulse signal generation module adopts the AD9954 chip and generates a multi-channel analog sine wave signal by direct digital frequency synthesis or converts the sine wave signal into a square wave signal through an internal high-speed comparator.

4. The transcutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: The two channels of the DAC module can respectively output stimulation signals with independent frequency, phase and amplitude, and the MCU module can store corresponding data in real time through the I / O parallel port.

5. The transcutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: The modulation module utilizes the AD633 four-image multiplier to modulate the carrier signal and the modulation signal, and outputs the final stimulation signal waveform.

6. The transcutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: The current detection circuit is connected in series with a load resistor, and the two ends of the resistor are output to the two input ends of the ADC module.

7. The transcutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: The ADC module uses the built-in ADC function of the MCU main control chip to convert the analog signal output by the current detection module into a digital signal.

8. The percutaneous spinal cord electrical stimulation system according to claim 1, characterized in that: It also includes a wireless communication module for realizing wireless data communication between the system and external devices.

9. A method for percutaneous electrical stimulation of the spinal cord, characterized in that: The transcutaneous spinal cord electrical stimulation system according to any one of claims 1 to 8 comprises the following steps: Initialize the circuit system and the myoelectric prosthetic hand, and set the default stimulation parameters and waveforms; The user generates movement intention and controls the contraction of the muscles at the end of the residual limb. The myoelectric prosthetic hand collects the myoelectric signals and decodes them into control commands. The pressure sensors on the fingers of the myoelectric prosthetic hand collect fingertip pressure signals and process them; Design transcutaneous spinal cord stimulation signals based on the discharge characteristics of real hand sensory afferent fibers; The contact force signal is converted into a control signal to control different channels to be in a gated state and update the electrical stimulation parameters; The output electrical stimulation mode stimulates the sensory afferent nerves of the cervical spinal cord, induces touch and pressure sensations, and uploads them to the somatic sensory cortex to form sensory feedback.

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