CN101496748A - Functional electric stimulation FES walking-assisting artificial nerve prosthesis device - Google Patents

Abstract

The invention belongs to medical and rehabilitation appliances, in particular to a functional electric stimulation FES walking artificial neural prosthesis device. In order to provide the functional electric stimulation FES walking artificial neural prosthesis device, and help patients suffering from spinal cord injury and paralysis of lower limbs with certain condition realize short-distance autonomous walking or rehabilitation training, the device adopts a technical proposal that the functional electric stimulation FES walking artificial neural prosthesis device comprises a singlechip, a D/A converter, a constant current source, a wave form turning unit, a stimulation electrode which are connected in sequence, and also comprises a functional key connected with the singlechip and a display unit; the singlechip is connected with the wave form turning unit; and the constant current source is connected with a power supply module which provides electricity for the constant current source. The functional electric stimulation FES walking artificial neural prosthesis device is mainly used for rehabilitation treatment of spinal cord injury and paralysis of lower limbs.

Description

Functional Electrical Stimulation FES Walking Aid Artificial Nerve Prosthesis Device

technical field

The invention belongs to medical treatment and rehabilitation equipment, and in particular relates to a functional electric stimulation FES walking aid artificial nerve prosthesis device.

Background technique

In 2007, relevant departments estimated that there were more than 250,000 patients with spinal cord injuries in the United States, and there were about 12,000 new cases every year. According to incomplete statistics, the number of patients with various types of spinal cord injuries in mainland China has reached 1 million, and is increasing at a rate of more than 100,000 per year. After spinal cord injury, nerve transmission is blocked, and sensory and motor functions below the level of injury will attenuate or even disappear, which can easily cause paralysis. For a large number of paralyzed patients, their physical activities are inconvenient and difficult to take care of themselves, which has brought a great burden to the family and society. It can be said that paralyzed patients have become a special social group living around us that urgently needs attention and care.

Artificial neural prosthesis (Neuroprosthesis) is a kind of electronic device that helps restore function after nerve injury. It is usually based on functional electrical stimulation (Functional Electrical Stimulation, abbreviated as FES) technology to construct prostheses and orthotics, instead of the brain to send nerve impulses, so as to achieve the purpose of controlling limb muscle activity. FES is generally considered to be an effective clinical aid in the functional rehabilitation of paralyzed patients. In addition, a lot of evidence shows that the use of FES also has good effects in improving the physical fitness and promoting health of paraplegic patients, such as the improvement of cardiopulmonary function, the impact of bone density and the soundness of metabolism. Assisting paralyzed patients to walk with electrical stimulation is an important aspect of the application of FES neuroprostheses. The reason is that after a paralyzed patient is paralyzed, the peroneal nerve and the muscles it controls can still function normally for quite a long time. If the nerve is stimulated with electricity when walking, it is possible to restore the lost function of the patient.

Contents of the invention

In order to overcome the deficiencies of the existing technology, a functional electrical stimulation FES walk-assisted artificial neural prosthesis device is provided to help patients with spinal cord injury and paralysis of the lower limbs to achieve short-distance autonomous walking or rehabilitation training.

The technical solution adopted by the present invention is a functional electric stimulation FES walking aid artificial neural prosthesis device, including a single-chip microcomputer connected in sequence, a D/A converter, a constant current source, a waveform reversal unit, and a stimulating electrode, and also includes a single-chip microcomputer connected function keys and a display unit, the single-chip microcomputer is connected to the waveform inversion unit, and the constant current source is connected to a power supply module for powering it.

The D/A converter is 4 pieces of 8-bit resolution D/A conversion integrated chips. The single-chip microcomputer is connected to 4 pieces of D/A chips through a piece of 74 series decoder, and the 4 pieces of D/A chips are respectively output to the constant current connected to each other. The source, the waveform flipping unit, and the stimulating electrodes form 4 independent channels corresponding to the left thigh, right thigh, left calf, and right calf.

The constant current source uses a constant current source with high voltage matching as the stimulus level, and also uses Wilson constant current source for secondary constant current. The relationship between the output current and the input voltage is:

I _O =V _I /R _S , wherein R _S is a sampling resistor, and V _I is a voltage converted by a D/A converter.

The waveform inversion unit includes: the control terminal is connected to the thyristor optocoupler of the microcontroller, and the two output terminals of the thyristor optocoupler are connected in series with an aluminum electrolytic capacitor with a withstand voltage of 630V and a resistor, and the output terminal of the connected capacitor is connected to Stimulating electrodes, and the other output terminal is connected to a constant current source.

Microcontrollers include:

Main module for initialization and waiting for interrupt;

Timing interrupt module for selecting stimulation channel and outputting stimulation intensity, cycle and pulse width;

An external interrupt module for judging whether the button increases or decreases the stimulation level of the corresponding channel and displays the stimulation intensity level;

An external interrupt response submodule used to increase or decrease the stimulus level of the corresponding channel by 1 or 1 according to the input signal of the button;

A sub-module used to control the D/A converter according to the corresponding relationship between the stimulus level and the current magnitude;

By outputting high and low levels, it is used to control the sub-module of the waveform inversion unit;

Submodule for controlling the display unit.

The present invention can bring following technical effect:

A functional electrical stimulation walking aid artificial neural prosthesis device that uses a single-chip microcomputer to modulate and control waveforms, and outputs an improved and adjustable Lilly stimulation wave sequence to achieve the purpose of helping paralyzed patients walk autonomously;

The operation is simple, the controllability is good, the control precision and sensitivity are high, and it is equipped with an LCD screen to display the stimulation intensity of 4 independent channels, so that non-professionals can also operate very conveniently, which greatly reduces the burden on patients and family members. burden;

The effect of stimulating the calf was tested, mainly including: first, the minimum step threshold, the optimal step threshold and the change value of the step current were given; second, the basic kinematic parameters (step length, step time) were used to The stimulation effect was evaluated; finally, the knee joint angle curve and angular velocity curve were measured at the optimal step threshold and normal state, and the results showed that the motor nerve prosthesis system can achieve better results;

It can provide help for better realization of lower limb motor nerve reconstruction in the future, and obtain considerable economic benefits.

Description of drawings

Figure 1 is the overall framework diagram of the system.

Figure 2 is a schematic diagram of the Lilly waveform.

Fig. 3 is a circuit diagram of a waveform inversion unit.

Figure 4 is the output of one flip unit.

Fig. 5 is a flowchart of the system software, wherein (a) is a flowchart of the main program, (b) is a flowchart of an external interrupt program, and (c) is a flowchart of a timer interrupt.

Figure 6 is a software flow chart of the function keys.

Figure 7 The software flow chart of the D/A module.

Figure 8 software flow chart of waveform flipping.

Figure 9 shows the unit software flow chart.

Detailed ways

The present invention provides a functional electrical stimulation walking aid artificial nerve prosthesis device with single-chip microcomputer control and liquid crystal display, which stimulates the muscles that lose their voluntary control by generating a series of specific pulse currents to make them contract, replace and correct Loss of function in organs and limbs, mainly the lower limbs, to help patients with spinal cord injury and paralysis of the lower limbs who have certain conditions to achieve short-distance autonomous walking or rehabilitation training.

The device is composed of four basic parts: command generator, controller, stimulator and electrodes. There are 4 independent channels, and the control button is manually adjusted by the patient. The parameters of the stimulation waveform are adjusted through processes such as digital-to-analog conversion and waveform inversion, and are displayed on the LCD screen for patient reference.

The present invention will be further described below in conjunction with the accompanying drawings and examples.

The overall block diagram of the functional electrical stimulation FES walking aid artificial neural prosthesis device of the present invention is shown in Figure 1. Considering the safety of the system to the human body, the output waveform of the system of the present invention adopts a Lilly wave with equal positive and negative charges, such as As shown in Figure 2, it is the improved stimulation waveform of the prototype. In order to make the system easy to operate, the pulse amplitude adjustment method commonly used in clinical practice is used to meet the needs of different paralyzed patients. The specific parameters of the system are selected as frequency 25Hz, pulse width 150μs, current 0-128mA adjustable, and the output mode of constant current stimulation is adopted.

According to the action characteristics of the lower limbs of the human body, the present invention is designed as 4 independent channels (left thigh, right thigh, left calf, right calf), mainly including control, D/A conversion, constant current source, waveform flip, function keys, liquid crystal display , stimulating electrodes and power supply eight parts.

The function keys adopt the manual control method. The present invention has 12 function keys in total, 2 thigh opening keys, 2 calf opening keys and 8 increase and decrease function keys for 4 channels, but only 10 function keys need to be controlled, excluding 2 Thigh key. The present invention adopts the hardware application software query method to carry out the external interrupt expansion. This query method can deal with any number of external interrupt sources in principle, and each function key is connected to the I/O port pin of the single-chip microcomputer. The single-chip microcomputer used in the present invention is a low-power consumption, high-performance CMOS 8-bit single-chip microcomputer, which contains ISP (In-system programmable, online programmable) flash read-only program memory that can be repeatedly erased and written. The device adopts high-density, non-volatile Manufactured with volatile memory technology, compatible with standard MCS-51 command system and 80C51 pin structure. The control signal provided by the single-chip microcomputer needs to go through digital-to-analog conversion to control the constant current source. Here, 4 pieces of 8-bit resolution D/A conversion integrated chips are used for digital-to-analog conversion, and a piece of 74 series decoder is used to convert 4 pieces of D/A The chip provides chip select signal and data transmission control signal. It is followed by dual operational amplifiers powered by dual power supplies to amplify the output current and convert it into a voltage value. The D/A output signal provides the input signal for the lower constant current source. Requirements for the constant current source: Since the electrical impedance of the human body is about 1K and the maximum stimulating current is 128mA, the constant current source used must be able to withstand a high voltage. The constant current source in this article is the secondary constant current circuit of the Wilson constant current source, and its current output is more stable. The load is connected to the ground, which improves the safety. The relationship between the output current of this current source and the input voltage is:

I _O =V _I /R _S (1)

Among them, R _S is the sampling resistance, and V _I is the voltage converted by DAC.

The waveform inversion is realized by controlling the opening and closing of the electronic switch by the single-chip microcomputer to charge and discharge the capacitor. The electronic switch uses 4 thyristor optocouplers. The resulting stimulation signals are connected to the patient's lower limbs via electrodes. The embodiment of the present invention uses a wire electrode, which is a self-adhesive reusable electrode. It has low contact resistance (150Ω), good viscosity, can be placed on different parts of the human body, and can be reused more than 20 times. The electrode size for the calf is 45 mm x 45 mm, and the electrode size for the thigh is 45 mm x 90 mm.

The power supply module adopts an isolated DC/DC module with a maximum output voltage of 150V and a maximum output current of 300mA. Input voltage DC24V±2V. The voltage and current of the power module are linearly adjustable throughout the whole process. The voltage stability is in the range of 0.1%, and the stability is good, which can meet the requirements of the system.

The gist of the present invention is that a constant current source with high voltage matching is used as the stimulus level, and the Wilson constant current source is used to carry out two-level constant current, which improves the constant current effect; because the voltage is very high during charging and discharging, high The voltage-resistant electronic switch controls the charge and discharge of the capacitor, and obtains a biphasic pulse current waveform with equal charges; the system of the present invention uses a single-chip microcomputer chip as the core control chip, which makes the system have high control precision, good sensitivity and high reliability.

The present invention will be further described in detail in several points below.

1 Secondary constant current circuit with Wilson constant current source:

Requirements for the constant current source: Since the electrical impedance of the human body is about 1K and the maximum stimulating current is 128mA, the constant current source used must be able to withstand a high voltage. The output current of the constant current source has nothing to do with the load _RL ; in addition, when V _CC is large enough, the output current can be changed to any value by changing the value of the potentiometer. Considering that the load is directly connected to the power supply, it is unsafe for the human body, so it has been improved.

The improved constant current source is a secondary constant current circuit with Wilson constant current source. Its characteristics are: the current output is more stable after the secondary constant current; the load is connected to the ground, and the safety is improved. The relationship between the output current of this current source and the input voltage is:

I _O =V _I /R _S (2)

Among them, R _S is the sampling resistance, and V _I is the voltage converted by DAC.

This design V _CC is -150V. Therefore, it is necessary to choose a high-voltage triode. The triode selected here has a withstand voltage of 350V and a maximum collector current of 500mA, which can meet the requirements of system design; in order to reduce temperature drift, a negative feedback circuit is added; the amplifier is Dual operational amplifiers powered by dual power supplies; select the size of the sampling resistor according to the actual stimulation current value required. Moreover, considering system security and portability, an isolated DC/DC module is used to supply power to the constant current source.

2 high withstand voltage bidirectional pulse electronic switch:

Waveform inversion is realized by controlling the opening and closing of the electronic switch by the single-chip microcomputer to charge and discharge the capacitor. The electronic switch uses 4 thyristor optocouplers.

The circuit connection diagram of the waveform flip unit is shown in Figure 3.

Capacitor selection 1μF. In the process of charging and discharging, the voltage at both ends of the capacitor is very high, so an aluminum electrolytic capacitor with a withstand voltage of 630V is selected.

Figure 4 shows the flip waveform all the way.

The waveform inversion unit can also control the 555 timer by using the voltage signal, and the 555 timer controls the inversion of the state of the circuit.

3 Open-loop control system with single-chip microcomputer as the core:

3.1 The overall process of the system:

For the whole system, the software includes two parts, the main program and the interrupt program, and the interrupt program includes timing interrupt and external interrupt. The software flowchart of these three parts is shown in Figure 5.

The following introduces the definition and initialization of variables. stimLD, stimRD, stimLX and stimRX are defined as stimulus level variables for the left thigh, right thigh, left calf and right calf, respectively. All 4 variables are initialized to 5; LX (RX) is used to judge whether the left calf (right calf) is stimulated, that is, when no calf switch is pressed, LX=0, RX=0, when the left (right) calf switch is pressed LX=1 (RX=1); stimX_num is defined as the number of stimulation pulses of the calf every time the calf button is pressed, and stimX_num=10 in this design.

3.2 Design of function keys:

Since the single-chip external interrupt sources used in the present invention cannot directly meet the requirements, this paper adopts the hardware application software query method to expand the external interrupt sources. After the expansion, the number of external interrupt sources is 10.

When a function key is pressed, one of its I/O ports becomes low level, responds to an external interrupt, and executes the function of the corresponding key. Its software flowchart is shown in Figure 6.

3.3 Software design of D/A conversion module:

The output of the artificial neural prosthesis system of the present invention has 14 current levels, and the interval between each level is 10mA (except the last level), and the maximum is 128mA. The corresponding relationship between the output current level and the current size is shown in Table 1.

Table 1 Correspondence between output current level and current magnitude

current level 1 2 3 4 5 6 7 Current size (mA) 0 10 20 30 40 50 60 current level 8 9 10 11 12 13 14 Current size (mA) 70 80 90 100 110 120 128

From the constant current source input and output formula I _O ＝V _I / _RS ; the output voltage V _I of the DAC can be calculated, and then the output voltage of the DAC can be obtained by the formula V _OUT ＝-V _REF ×(digital code/256) The output digital code value. Calculated as follows:

In the system, D/A adopts double-buffering working mode, that is, both registers of D/A chip work in controlled latch state. The lower four bits of the 74 decoder respectively control the chip selection terminals of the four D/As, and the upper four bits respectively control the data transmission control signal terminals of the four D/As. When the program is executed, first select 4 pieces of D/A CS to transfer the stimulation value to the D/A input register for registration; after selecting the stimulation channel, enable the XEFR controlling the corresponding channel D/A, and transfer the stimulation value to the DA for conversion device, output at the output of the D/A. Its software flowchart is shown in Figure 7.

3.4 Software design of waveform flipping:

The unit is controlled by some I/O ports of the microcontroller. When there is square wave output, these I/O ports are at high level, the electronic switch is turned off, the capacitor is charged, and a square wave is output; when discharging, these I/O ports are correspondingly at low level, the electronic switch is closed, and the capacitor is discharged. Its software flowchart is shown in Figure 8.

3.5 Displayed software design:

The present invention sends data or control commands bit by bit into the 16-bit shift register inside the MAX7219 in the form of 16-bit data packets, and drives 8 LEDs for display, as shown in FIG. 9 .

In order to examine the reliability and feasibility of the present invention, relevant experiments have been carried out, including stimulating the thigh and knee joint extension experiment and stimulating the calf stepping experiment.

1. Stimulate the thigh to test whether the system can make the subject stand up, and give the minimum action threshold, maximum action threshold and action current change value. The result is satisfactory.

2. The effect of stimulating the calf was tested. It mainly includes: first, the minimum step threshold, the optimal step threshold and the change value of the step current are given; second, the stimulation effect is evaluated by using the basic kinematic parameters (step length, step time); finally, the Knee joint angle curve and angular velocity curve at the optimal step threshold and normal state. The results show that the motor nerve prosthesis system can achieve better results.

The invention provides a functional electric stimulation (FES) walking aid artificial neural prosthesis device which uses a single-chip microcomputer to modulate and control waveforms, and outputs specific stimulation wave sequences to achieve the purpose of helping paralyzed patients walk autonomously. The operation is simple, the controllability is good, the control precision and sensitivity are high, and it is equipped with an LCD screen to display the stimulation intensity of 4 independent channels, which is convenient for control. It can provide help for better realization of lower limb motor nerve reconstruction in the future, and obtain considerable social and economic benefits. The best implementation plan is to use patent transfer and technical cooperation.

Claims (5)

1. A functional electrical stimulation FES walking aid artificial neural prosthesis device is characterized in that it comprises a sequentially connected single-chip microcomputer, a D/A converter, a constant current source, a waveform reversal unit, and stimulating electrodes, and also includes a single-chip microcomputer connected to each other. function keys and a display unit, the single-chip microcomputer is connected to the waveform inversion unit, and the constant current source is connected to a power supply module for powering it. 2. A kind of functional electrical stimulation FES walk-assisted artificial nerve prosthesis device according to claim 1, is characterized in that, D/A converter is 4 slices of 8-bit resolution D/A conversion integrated chips, single-chip microcomputer passes through a slice The 74 series decoder is connected to 4 pieces of D/A chips, and the 4 pieces of D/A chips are respectively output to the constant current source, waveform inversion unit, and stimulating electrodes connected to each other, forming 4 corresponding to the left thigh, right thigh, and left calf , the independent channel of the right calf. 3. A kind of functional electrical stimulation FES walk-assisted artificial neural prosthesis device according to claim 1, characterized in that, the constant current source adopts a constant current source with high voltage matching as the stimulation level, and also adopts Wilson The Wilson constant current source performs two-level constant current, and the relationship between the output current and the input voltage is: I _O =V _I /R _S , wherein R _S is a sampling resistor, and V _I is a voltage converted by a D/A converter. 4. A functional electrical stimulation FES walking aid artificial nerve prosthesis device according to claim 1, characterized in that, the waveform inversion unit comprises: a control terminal connected to a thyristor optocoupler of a single chip microcomputer, a thyristor optocoupler An aluminum electrolytic capacitor with a withstand voltage of 630V and a resistor are connected in series between the two output terminals. The output terminal connected to the capacitor is connected to the stimulation electrode, and the other output terminal is connected to a constant current source. 5. A kind of functional electric stimulation FES walk-assisted artificial nerve prosthesis device according to claim 1, is characterized in that, single-chip microcomputer comprises: Main module for initialization and waiting for interrupt; Timing interrupt module for selecting stimulation channel and outputting stimulation intensity, cycle and pulse width; An external interrupt module for judging whether the button increases or decreases the stimulation level of the corresponding channel and displays the stimulation intensity level; An external interrupt response submodule used to increase or decrease the stimulus level of the corresponding channel by 1 or 1 according to the input signal of the button; A sub-module used to control the D/A converter according to the corresponding relationship between the stimulus level and the current magnitude; By outputting high and low levels, it is used to control the sub-module of the waveform inversion unit; Submodule for controlling the display unit.

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