G-LOC warning method and system using G-LOC warning algorithm

Abstract

The present invention relates generally to a method for preventing gravity-induced loss of consciousness (G-LOC), which arises from increased acceleration during flight, and more particularly, to a G-LOC warning method and system using a G-LOC warning algorithm, which detects, in advance, risk factors that cause a G-LOC state by monitoring a change in the electromyogram (EMG) signal in real time. According to the G-LOC warning method and system using the G-LOC warning algorithm of the present invention, because information about the EMG signal is measured and collected in real time, changes in the EMG signal of a pilot who is exposed to high levels of acceleration during a flight maneuver are measured and checked on the spot.

Claims

1. A gravity-induced loss of consciousness (G-LOC) warning method, comprising: measuring an electromyogram (EMG) signal of a muscle using an EMG sensor and storing the EMG signal; setting reference values to an initial reaction value of an integrated absolute value (IAV) and an initial reaction value of a waveform length (WL), calculated based on an initial EMG signal, which is measured for a certain time period from a start of measurement of the EMG signal, and storing the reference values; monitoring the EMG signal in real time using the EMG sensor, calculating the IAV, the WL, a change in a slope of the IAV, and a change in a slope of the WL from the monitored EMG signal, as indication values, and storing the indication values; and comparing the reference values with the indication values determining that the slope of the IAV and the slope of the WL, calculated in real time, decrease N successive times and that each of a measured IAV and WL is equal to or less than a certain percentage of the reference value thereof, and ascertaining based on the determining that a risk of G-LOC exists, wherein a warning signal is generated based on the ascertaining.

2. The G-LOC warning method of claim 1, wherein determining includes determining that each of the IAV and the WL, measured in real time, is equal to or less than the certain percentage of the reference value thereof N successive times.

3. The G-LOC warning method of claim 2, wherein N is 3.

4. The G-LOC warning method of claim 1, wherein the measuring starts at 5G or higher acceleration.

5. The G-LOC warning method of claim 1, wherein the setting the reference values comprises: calculating the initial reaction value of the IAV and the initial reaction value of the WL based on the initial EMG signal, measured for the certain time period from the start of the measurement of the EMG signal; and calculating and recording an average of the initial reaction value of the IAV and an average of the initial reaction value of the WL.

6. A gravity-induced loss of consciousness (G-LOC) warning method, comprising: measuring an electromyogram (EMG) signal of a muscle using an EMG sensor and storing the EMG signal; setting reference values to an initial reaction value of an integrated absolute value (IAV) and an initial reaction value of a waveform length (WL), calculated based on an initial EMG signal, measured for a certain time period from a start of measurement of the EMG signal, and storing the reference values; monitoring the EMG signal in real time using the EMG sensor, calculating the IAV, the WL, and changes in slopes of the IAV and WL from the monitored EMG signal, as indication values, and storing the indication values; and comparing the reference values with the indication values, determining that each of the IAV and the WL, measured in real time, is equal to or less than a certain percentage of the reference value thereof N successive times, and ascertaining based on the determining that a risk of G-LOC exists, wherein a warning signal is generated based on the ascertaining.

7. The G-LOC warning method of claim 6, wherein the determining includes determining that a slope of the IAV and a slope of the WL, calculated in real time, decrease N successive times and that each of the measured IAV and WL is equal to or less than the certain percentage of the reference value thereof.

8. The G-LOC warning method of claim 7, wherein N is 3.

9. The G-LOC warning method of claim 6, wherein the measuring starts at 5G or higher acceleration.

10. The G-LOC warning method of claim 6, wherein the setting the reference values comprises: calculating the initial reaction value of the IAV and the initial reaction value of the WL based on the initial EMG signal, measured for the certain time period from the start of the measurement of the EMG signal; and calculating and recording an average of the initial reaction value of the IAV and an average of the initial reaction value of the WL.

11. A gravity-induced loss of consciousness (G-LOC) warning system, comprising: a sensor unit, including an EMG sensor, for measuring an EMG signal by being affixed on a part of a body of a user; a control unit for setting reference values using an initial reaction value of an integrated absolute value (IAV) and an initial reaction value of a waveform length (WL) based on the measured EMG signal, for calculating the IAV, the WL, a change in a slope of the IAV, and a change in a slope of the WL as indication values by monitoring the EMG signal in real time using the EMG sensor, and for determining whether a risk of G-LOC exists through a series of determination processes using the reference values and the indication values; a display unit for receiving the EMG signal and displaying an action potential of the EMG signal; and a warning unit for receiving a warning signal.

12. The G-LOC warning system of claim 11, wherein when the slope of the IAV and the slope of the WL, calculated in real time, decrease N successive times and when each of a measured IAV and WL is equal to or less than a certain percentage of the reference value thereof, the control unit determines that the risk of G-LOC exists and outputs the warning signal to the warning unit.

13. The G-LOC warning system of claim 12, wherein if each of the IAV and the WL, measured in real time, is equal to or less than the certain percentage of the reference value thereof N successive times, the control unit determines that the risk of G-LOC exists and outputs the warning signal to the warning unit.

14. The G-LOC warning system of claim 11, wherein when each of the IAV and the WL, measured in real time, is equal to or less than the certain percentage of the reference value thereof N successive times, the control unit determines that the risk of G-LOC exists and outputs the warning signal to the warning unit.

15. The G-LOC warning system of claim 14, wherein if the slope of the IAV and the slope of the WL, calculated in real time, decrease N successive times and if each of the measured IAV and WL is equal to or less than the certain percentage of the reference value thereof, the control unit determines that the risk of G-LOC exists and outputs the warning signal to the warning unit.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a graph illustrating the G-tolerance of an average person over time;

(2) FIGS. 2A, 2B, 3A, and 3B show a G-LOC warning method using a G-LOC warning algorithm according to an embodiment of the present invention;

(3) FIG. 4 is a block diagram of a G-LOC warning system according to an embodiment of the present invention;

(4) FIGS. 5A, 5B, and 5C are graphs illustrating a change in an EMG signal when a G-LOC situation occurs;

(5) FIG. 6 is a graph illustrating a change in a calculated indication value according to an embodiment of the present invention;

(6) FIG. 7 is a graph illustrating a change in an integrated absolute value (IAV) and a change in a waveform length (WL), calculated according to an embodiment of the present invention; and

(7) FIGS. 8A, 8B, 8C, 8D, 8E, and 8F are graphs illustrating a change in a measured EMG signal according to an embodiment of the present invention.

BEST MODE

(8) Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings, but this embodiment is merely an example. Accordingly, the present invention is not limited to the embodiment, and may be implemented in various forms by those skilled in the art to which the present invention pertains.

(9) Also, in the following description, it should be apparent to those skilled in the art that the present invention may be embodied without specific details such as detailed configurations or components.

(10) In a G-LOC warning algorithm of the present invention, an electromyogram (EMG) signal, which is a signal generated when muscles contract, is measured using an EMG sensor. Specifically, a surface EMG signal, generated in muscles near electrodes placed on the skin of a subject, is measured.

(11) The regions in which the EMG is to be measured according to an embodiment may be the back of a pilot's neck, the abdomen and the legs, and may be a part in which an EMG signal, which changes in response to the increased acceleration, can be measured. Desirably, the EMG signal from the calf muscles may be measured, and more desirably, the EMG signal from the gastrocnemius muscle may be measured, whereby the force of skeletal muscle contraction may be measured upon exposure to high levels of acceleration.

(12) In the G-LOC warning algorithm, when acceleration becomes equal to or greater than 5 G, the EMG signal from a muscle is measured using an EMG sensor and is then stored, and an indication value is calculated using a certain equation based on the measured EMG signal.

(13) As an indication value with which G-LOC may be predicted, there are the root mean square (RMS) of the amplitude of an EMG signal, the integrated absolute value (IAV), the mean absolute value (MAV), the slope sign change (SSC), the waveform length (WL), the zero crossing (ZC), the median frequency, and the like.

(14) Here, the RMS, the IAV, and the MAV are indication values for evaluating the force of muscle contraction, and the SSC, the WL, the ZC, and the median frequency may be used as indication values for evaluating both the force of muscle contraction and muscle fatigue. Among these indication values, an indication value that meaningfully changes before and after G-LOC may be analyzed.

(15) Each of these indication values may be calculated using the following equations from Equation (1) to Equation (6) based on the measured EMG signal.

(16) The root mean square (RMS) is calculated using the following Equation (1):

(17) $\begin{array}{cc}\mathrm{RMS}=\sqrt{\frac{1}{N}\underset{n=1}{\overset{N}{.Math.}}{x}_n^2}& \left(1\right)\end{array}$

(18) The integrated absolute value (IAV) may be calculated using the following Equation (2):

(19) $\begin{array}{cc}IAV=\underset{n=1}{\overset{N}{.Math.}}.Math.x_n.Math.& \left(2\right)\end{array}$

(20) Also, the mean absolute value (MAV), which is acquired by averaging the IAV, may be calculated using the following Equation (3):

(21) $\begin{array}{cc}MAV=\frac{1}{N}\underset{n=1}{\overset{N}{.Math.}}.Math.x_n.Math.& \left(3\right)\end{array}$

(22) The waveform length (WL) may be calculated using the following Equation (4):

(23) $\begin{array}{cc}WL=\underset{n=1}{\overset{N-1}{.Math.}}.Math.x_{n+1}-x_n.Math.& \left(4\right)\end{array}$

(24) The slope sign change (SSC) may be calculated using the following Equation (5):

(25) $\begin{array}{cc}SSC=\underset{n=2}{\overset{N-1}{.Math.}}\left[f\left\{x_n-x_{n-1}\right\}\left\{x_n-x_{n-1}\right\}\right]\mathrm{where}f\left(x\right)=\left\{\begin{array}{cc}1,& \mathrm{if}x\mathrm{threshold}\\ 0,& \mathrm{otherwise}\end{array}\right\}& \left(5\right)\end{array}$

(26) The zero crossing (ZC) may be calculated using the following Equation (6):

(27) $\begin{array}{cc}ZC=\underset{n=1}{\overset{N-1}{.Math.}}\left[\mathrm{sgn}\left(x_n{x}_{n-1}\right).Math..Math.x_n-x_{n+1}.Math.\mathrm{threshold}\right]\mathrm{where}\mathrm{sgn}\left(x\right)=\left\{\begin{array}{cc}1,& \mathrm{if}x\mathrm{threshold}\\ 0,& \mathrm{otherwise}\end{array}\right\}& \left(6\right)\end{array}$

(28) Hereinafter, first, the G-LOC warning algorithm of the present invention will be described in detail.

(29) The G-LOC warning algorithm starts when the acceleration becomes equal to or greater than 5 G, and an EMG signal measured using an EMG sensor is stored. Here, as the initial reaction values in the measured EMG signal, indication values are calculated using the above-described equations based on the EMG signal, which is measured for 3 seconds. Then, a reference value is set to a value that is acquired by averaging the calculated indication values. Here, it is desirable for the reference value to be a value acquired by averaging the IAV or a value acquired by averaging the WL.

(30) Meanwhile, the indication values, calculated based on the EMG signal, which is measured in real time, and the slope of the indication values are detected. Here, each of the indication values may be monitored, and monitoring may be performed using 3-second windows with an overlap of 0.5 seconds, which are set in consideration of the wavelength of the EMG signal. After monitoring of the EMG signal is performed, the results, processed in real-time, may be displayed and checked.

(31) Subsequently, whether a risk of G-LOC exists is determined based on the reference value, the indication values, and the changes in the slopes of the indication values, which are calculated in real time. When a signal, generated depending on the determination, is received, if the signal corresponds to a critical condition in which a person may enter a G-LOC state, a warning signal is generated, whereby a warning may be given through various senses, including the sense of hearing and the sense of sight.

(32) Also, when it is determined that there is no risk of G-LOC, or after the warning signal is generated, the measurement of an EMG signal and evaluation of the risk of G-LOC may be continuously performed by monitoring the EMG signal in real time.

(33) In connection with the above description, a G-LOC warning method of the present invention will be described in detail. The method may be implemented as a first embodiment and a second embodiment depending on the method for determining whether G-LOC is to occur based on the IAV and WL, selected from among the indication values.

(34) As illustrated in FIGS. 2A, and 2B, in a step of measuring an EMG signal in the first embodiment, when acceleration equal to or greater than 5 G is applied, an EMG signal is measured using an EMG sensor, and is then stored at step S110. In a step of setting a reference value for an EMG signal, the initial reaction values of the IAV and the initial reaction values of the WL are calculated at step S120 using the initial EMG signal, which is measured for 3 seconds from the start of measurement, and the reference values are set by averaging the initial reaction values of the IAV and by averaging the initial reaction values of the WL at step S130.

(35) Here, the measured EMG signal is the initial reaction value, and may be measured using 1-second windows with an overlap of 0.5 seconds, which are set in consideration of the wavelength of the EMG signal.

(36) Meanwhile, in a step of monitoring an EMG signal, the EMG signal may be monitored in real time using the EMG sensor, and the IAV, the WL, and changes in the slopes of the IAV and the WL are calculated at step S140. Monitoring may be performed in real time using 3-second windows with an overlap of 0.5 seconds in consideration of the wavelength of the EMG signal.

(37) Then, in a step of determining whether a risk of G-LOC exists, whether the current state satisfies the conditions for G-LOC is determined by comparing each of the reference values calculated in the step of setting the reference value for the EMG signal with each of the indication values calculated in the step of monitoring the EMG signal. More specifically, in the result of the monitoring, when the slopes of the IAV and the WL, which are measured in real time, decrease n times in a row, and when each of the n-th measured values is equal to or less than 70% of the reference value thereof, it is determined that the risk of G-LOC exists, and a warning may be given at step S151. If it is determined from the criteria that there is no risk of G-LOC, whether the IAV and the WL, measured in real time, are equal to or less than 70% of the reference values thereof n times in a row is checked, and if so, it is determined that there is the risk of G-LOC, and thus a warning is given at step S161, as shown in FIG. 2B. Here, it is desirable to set n to 3.

(38) In the second embodiment, the same processes are performed as in the first embodiment. However, the step of determining whether the risk of G-LOC exists is performed in a way other than that in the first embodiment, as shown in FIG. 3B. Specifically, when the IAV and the WL, measured in real time, are equal to or less than 70% of the reference values thereof n times in a row, it is determined that the risk of G-LOC exists, and thus a warning is given at step S152.

(39) Also, when it is determined from the above criterion that there is no risk of G-LOC, when the slopes of the IAV and the WL, measured in real time, decrease n times in a row and when each of the n-th measured values is equal to or less than 70% of the reference value thereof, it is determined that the risk of G-LOC exists, thus a warning is given at step S162. Here, desirably, n may be 3.

(40) As illustrated in FIG. 4, a G-LOC warning system according to the present invention may include a sensor unit 110, a control unit 120, a display unit 130, a warning unit 140, and a storage unit 150.

(41) The sensor unit 110 includes an EMG sensor 111 and a gravitational acceleration sensor 112. The EMG sensor 111 measures an EMG signal by being affixed on a part of the body of a user, and the part of the body may be the back of a pilot's neck, the abdomen, or the calves. More desirably, the EMG signal from a calf muscle may be measured. Particularly, if the force of skeletal muscle contraction in response to exposure to acceleration is evaluated from the EMG signal measured from the gastrocnemius muscle, the accuracy of the evaluation may be improved.

(42) The gravitational acceleration sensor 112 is a sensor that is capable of measuring the gravitational acceleration applied to a user in real time.

(43) The control unit 120 receives the EMG signal and processes the signal according to the above-mentioned G-LOC warning method. More specifically, the G-LOC warning method is the method illustrated in FIGS. 2A and 2B, and may be configured such that, based on the EMG signal measured by the sensor unit 110, the initial reaction values of the IAV and the initial reaction values of the WL are calculated at step S120; the average of the calculated initial reaction values of the IAV and the average of the calculated initial reaction values of the WL are calculated and set as reference values at step S130; the IAV, the WL, and changes in the slopes of the IAV and the WL are calculated as indication values at step S140 by monitoring the EMG signal in real time using the EMG sensor; a series of determination processes is performed using the reference values and the indication values (steps S151 and S161); and a G-LOC warning signal is output depending on the determination. Also, as shown in FIG. 3B, the determination processes for outputting a G-LOC warning signal in the signal processing method may be performed in the opposite order (steps S152 and S162) of the determination processes illustrated in FIG. 2B. Here, the control unit may be a device that is capable of information processing, such as a computer, a laptop, or the like.

(44) Because the G-LOC warning method performed by the control unit 120 of the G-LOC warning system is the same as the above-described G-LOC warning method using the G-LOC warning algorithm according to an embodiment of the present invention, the description thereof will be omitted.

(45) The display unit 130 includes a display means for receiving the EMG signal measured by the sensor unit and displaying the EMG signal outside, and may display the measured EMG signal as a waveform.

(46) The warning unit 140 receives a warning signal output from the control unit and warns a user using a visual means and an audible means. The warning unit 140 may warn a user whether there is a risk using an audio device 141, which generates an alarm, a visual device 142, which flickers warning light, and devices using the other senses 143, and effectively reminds a user, who is at risk of losing consciousness, whether a risk exists by being arranged in a place that may be easily noticed by the user.

(47) Meanwhile, the storage unit 150 may store information associated with G-LOC, such as the EMG signal, which is measured by the sensor unit and input to the control unit 120, the set reference values, the calculated indication values, and the like, therein.

(48) The embodiment of the present invention is accomplished targeting 47 Korean air force pilots whose age ranges from 27 to 40, and the EMG signal is measured using circular electrodes placed at intervals of 5 cm on the gastrocnemius muscle and the soleus muscle.

(49) When G-LOC occurs due to the exposure to high levels of acceleration, the peak of the EMG signal tends to decrease over time, as illustrated in FIG. 5A, and this tendency may be confirmed from the moving average of the EMG signal, as shown in FIG. 5B. It is confirmed that G-LOC occurs if the EMG signal is equal to or less than 0.5 uV on average.

(50) FIG. 6 and FIG. 7 are graphs in which an EMG signal measured from the calf muscle of a subject is analyzed according to an embodiment of the present invention.

(51) FIG. 6 shows certain reference values calculated based on the measured EMG signal and changes in the RMS, the IAV, the MAV, the SSC, the WL, the ZC, and the MF, which are measured at intervals of 0.5 seconds. Particularly, it is confirmed that the IAV and the WL noticeably decrease in the alarm phase, which corresponds to 3 seconds before the subject enters a G-LOC state.

(52) Also, FIG. 7 shows the result of the consecutive measurement of only the IAV and the WL based on the same data as in FIG. 6. As illustrated, when a subject is exposed to acceleration of 6 G, the IAV and the WL decrease in the alarm phase before the subject enters a G-LOC state.

(53) FIGS. 8A to 8F are graphs illustrating the change in the EMG signal measured in each of the subjects according to an embodiment of the present invention. As shown in FIGS. 8A to 8F, it is confirmed that, according to the G-LOC warning algorithm, a G-LOC warning signal sounds 0.5 to 3.5 seconds before the occurrence of G-LOC depending on the EMG signal measured from each of the subjects when they are exposed to acceleration of 6 G.

(54) Among these examples, FIG. 8C shows the case in which the subject spontaneously recovers (by self-recovery) after the first warning signal is generated, and does not enter a G-LOC state, but the risk of G-LOC is determined again through continuous monitoring and the G-LOC warning signal sounds again 3.5 seconds before entering a G-LOC state.

(55) As described above, the present invention provides the method for preventing accidents attributable to G-LOC through the analysis of an EMG signal. According to the method, because a G-LOC state may be continuously predicted in real time using the G-LOC warning algorithm, and because the G-LOC may be quickly detected in early stages, an aircraft may be induced to fly safely before crashing, whereby the incidence of aircraft accidents may be reduced and the lives of aircraft pilots may be saved.