Driver's pressure level detection device and detection method

Abstract

This disclosure provides a device and method for detecting a driver's stress level. The device includes: an electrocardiogram (ECG) sensor that uses electrodes disposed on the steering wheel of a vehicle to measure the driver's ECG; and a controller that monitors the driver's ECG, determines invalid regions in the ECG based on the shape of the ECG, and compensates for the ECG within the determined invalid regions.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0092458, filed on July 24, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a technique for detecting stress levels based on a vehicle driver's electrocardiogram (ECG). Background Technology

[0004] Typically, in detecting a driver's stress level, electrodes can be placed on the left and right sides of the steering wheel. Microcurrents flowing through the driver's body (e.g., action currents generated by heart contractions) can be obtained through these electrodes. The obtained microcurrents can be filtered to measure the driver's electrocardiogram (ECG). Based on the measured ECG, the standard deviation of the NN interval (SDNN), an analytical indicator that quantifies stress, can be calculated. It can be determined that the lower the calculated SDNN, the higher the stress level, and vice versa.

[0005] An electrocardiogram (ECG) that is measured normally within a reference time (e.g., between 30 seconds and 5 minutes) (hereinafter referred to as a valid ECG) is required to detect the stress level of a vehicle driver as described above. However, for example, during the ECG measurement, when the driver temporarily releases their hands from the electrodes, when noise is generated due to various electronic devices in the vehicle, or when noise is generated due to vehicle vibration, an ECG containing abnormal intervals (hereinafter referred to as invalid intervals) may be measured. Here, invalid intervals may include intervals where no ECG signal (action current) is input but only a noise signal is input, or intervals where an ECG signal is input but cannot be read due to the noise signal.

[0006] Traditional techniques for detecting stress levels in vehicle drivers either stop (or cannot) detecting stress levels when no valid electrocardiogram (ECG) is measured, or rely on ECGs containing invalid intervals to detect stress levels in vehicle drivers.

[0007] Therefore, when no valid electrocardiogram (ECG) is measured, conventional techniques cannot detect the driver's stress level, causing inconvenience. Furthermore, when detecting a driver's stress level based on an ECG containing invalid intervals, conventional techniques cannot accurately measure the driver's stress level.

[0008] The description in this background section is intended to facilitate an understanding of the background of the invention and may include content beyond the prior art known to those skilled in the art. Summary of the Invention

[0009] One aspect of this disclosure provides a driver stress level detection device and method. When detecting the driver's stress level based on the driver's electrocardiogram (ECG), the device monitors the driver's ECG, determines invalid regions in the ECG based on its shape, and compensates for the ECG within the determined invalid regions. This minimizes the number of failed driver stress level detections and improves the accuracy of driver stress level detection.

[0010] The technical problems to be solved by the present invention are not limited to those described above, and any other technical problems not mentioned herein will be clearly understood by those skilled in the art from the following description.

[0011] According to one aspect of this disclosure, a driver stress level detection device includes: an electrocardiogram (ECG) sensor that uses electrodes disposed on the steering wheel of a vehicle to measure the driver's ECG; and a controller that monitors the driver's ECG, determines invalid regions in the ECG based on the shape of the ECG, and compensates for the ECG within the determined invalid regions.

[0012] In one implementation, the controller may further measure the driver's electrocardiogram (ECG) during the time period corresponding to the invalid interval to compensate for the ECG within the invalid interval.

[0013] In one implementation, the controller can replace the ECG within the invalid interval with an ECG measured immediately preceding the invalid interval to compensate for the ECG within the invalid interval.

[0014] In one implementation, the controller can perform compensation when the time corresponding to the invalid interval is within the critical time.

[0015] In one implementation, the controller can terminate the detection of the driver's stress level when the time corresponding to the invalid interval is greater than the critical time.

[0016] In one implementation, the controller can reset the electrocardiogram measurement when the number of invalid intervals within the critical time exceeds the baseline number.

[0017] In one implementation, with the time corresponding to the invalid interval limited to a critical time, the controller can extend the critical time when no driver's electrocardiogram is measured or when the driver's hand is sensed to have left the area.

[0018] In one implementation, the controller may stop the electrocardiogram (ECG) measurement when the steering angle of the vehicle exceeds a reference angle, when the vehicle speed exceeds a reference speed, when the road surface of the vehicle is unpaved, or when the number of speed bumps continuously located in front of the vehicle on the road exceeds a reference number.

[0019] According to another aspect of this disclosure, a method for detecting a driver's stress level includes: an electrocardiogram (ECG) sensor using electrodes disposed on the steering wheel of a vehicle to measure the driver's ECG; a controller monitoring the driver's ECG; the controller determining invalid regions in the ECG based on the shape of the ECG; and the controller compensating for the ECG within the determined invalid regions.

[0020] In one implementation, compensating for the electrocardiogram within the determined invalid interval may include a first compensation operation, which further measures the driver's electrocardiogram within the time period corresponding to the invalid interval to compensate for the electrocardiogram within the invalid interval.

[0021] In one implementation, compensating for the ECG within the identified invalid interval may include a second compensation operation that replaces the ECG within the invalid interval with an ECG measured immediately preceding the invalid interval, thereby compensating for the ECG within the invalid interval.

[0022] In one implementation, the second compensation operation may include: performing compensation when the time corresponding to the invalid interval is within a critical time; terminating the detection of the driver's stress level when the time corresponding to the invalid interval is greater than the critical time; and resetting the electrocardiogram measurement when the number of invalid intervals occurring within the critical time exceeds a baseline number.

[0023] In one embodiment, the second compensation operation may further include: extending the critical time when driver vehicle manipulation is sensed; and stopping the electrocardiogram measurement when the steering angle of the vehicle's steering wheel exceeds a reference angle, when the vehicle's speed exceeds a reference speed, when the road surface of the vehicle's driving road is an unpaved road, or when the number of speed bumps continuously located in front of the vehicle on the vehicle's driving road exceeds a reference number. Attached Figure Description

[0024] To make this disclosure easier to understand, various forms of this disclosure will now be described with reference to the accompanying drawings and by way of example, wherein:

[0025] Figure 1 This is a configuration diagram of a driver's pressure level detection device of one form disclosed herein;

[0026] Figure 2AThis is an example diagram of a normal electrocardiogram measured by an electrocardiogram sensor installed in a driver stress level detection device of one form of this disclosure;

[0027] Figure 2B This is an example diagram of an electrocardiogram containing invalid intervals, measured by an electrocardiogram sensor installed in a driver stress level detection device of one form of this disclosure;

[0028] Figure 2C This is an example diagram showing the result of a controller in a driver stress level detection device of one form of this disclosure compensating for an invalid interval of the electrocardiogram.

[0029] Figure 2D This is another example diagram showing the result of a controller in a driver stress level detection device of one form of this disclosure compensating for an invalid interval of the electrocardiogram;

[0030] Figure 3 This is an example diagram showing the mounting position of the electrodes within an electrocardiogram sensor in one form of a driver stress level detection device disclosed herein.

[0031] Figure 4 This is a flowchart of a method for detecting driver stress levels according to one form of this disclosure; and

[0032] Figure 5 This is a block diagram illustrating a form of computational system for performing a driver's pressure level detection method according to the present disclosure. Detailed Implementation

[0033] In the following, some embodiments of the present disclosure will be described in detail with reference to the exemplary accompanying drawings. When adding reference numerals to components in each drawing, it should be noted that identical or equivalent components are denoted by the same reference numerals even if shown in different drawings. Furthermore, in describing embodiments of the present disclosure, detailed descriptions of such known configurations or functions will be omitted if it is determined that they impede understanding of the embodiments of the present disclosure.

[0034] In describing components according to embodiments of the present disclosure, terms such as first, second, A, B, (a), (b), etc., may be used. These terms are intended only to distinguish a component from other components, and they do not limit the nature, order, or sequence of the components. Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms defined, for example, in a general dictionary, shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and shall not be interpreted in an ideal or excessive form unless expressly defined herein.

[0035] Figure 1 This is a configuration diagram of a driver's pressure level detection device according to an embodiment of the present disclosure.

[0036] like Figure 1 As shown, the driver stress level detection device 100 according to an embodiment of the present disclosure may include a memory 10, a vehicle network access device 20, an electrocardiogram sensor 30, and a controller 40. Depending on the implementation of the driver stress level detection device 100 according to an embodiment of the present disclosure, the various components may be interconnected to form a single component, or some components may be omitted.

[0037] In the description of the various components, firstly, when detecting the driver's stress level based on the driver's electrocardiogram (ECG), memory 10 can store the ECG of the driver, determine invalid regions in the ECG based on its shape, and compensate for the ECG within the determined invalid regions. Here, invalid regions can include regions where no ECG signal (action current) is input but only a noise signal, or regions where an ECG signal is input but cannot be read due to noise (regions where the ECG shape is not displayed). For example, such invalid regions could be... Figure 2B The interval β is shown.

[0038] Memory 10 can store the measurement time (hereinafter referred to as the reference time) of a valid electrocardiogram used to detect the stress level of a vehicle driver. Here, a valid electrocardiogram refers to an electrocardiogram measured within the reference time without invalid intervals. For example, such a valid electrocardiogram is as follows: Figure 2A As shown. Additionally, for example, the reference time α can be a value between 30 seconds and 5 minutes.

[0039] The memory 10 can store a critical time (e.g., 5 seconds) for limiting the length of invalid intervals in an electrocardiogram.

[0040] During the detection of the driver's stress level, when the driver performs operations on various functions of the vehicle, the memory 10 can further store additional time (e.g., 2 seconds) to extend the critical time.

[0041] The memory 10 may include storage media of at least one type of memory, such as flash memory, hard disk, micro memory, and card type (e.g., secure digital card (SD card) or extreme digital card (XD card), as well as memory such as random access memory (RAM), static RAM (SRAM), read-only memory (ROM), programmable ROM (PROM), electrically erasable PROM (EEPROM), magnetic RAM (MRAM), disk and optical disk types.

[0042] The vehicle network access device 20 is a module that provides an interface for accessing the vehicle network. Under the control of the controller 40, it can obtain various vehicle information, driving information, operating information, etc. from the vehicle network.

[0043] As an example, the vehicle network access device 20 can acquire steering wheel remote controller (SWRC) switch control information (control signals), transmission control information, air conditioning switch control information, vehicle switch control information, etc., as vehicle control information. In this case, the vehicle switch control information may include window switch control information, sunroof switch control information, multi-function switch control information, light switch control information, seat adjustment switch control information, etc.

[0044] Such vehicle networks may include Controller Area Network (CAN), Controller Area Network with Flexible Data-rate (CAN FD), Local Interconnect Network (LIN), FlexRay, Media Oriented Systems Transport (MOST), Ethernet, etc.

[0045] like Figure 3 As shown, the electrocardiogram (ECG) sensor 30 may have electrodes 310 disposed on the left and right sides of the vehicle's steering wheel, respectively. The ECG sensor 30 can acquire microcurrents flowing through the driver's body (e.g., action currents generated due to heart contractions) via the electrodes 310, and measure the driver's electrocardiogram (ECG) based on the acquired microcurrents. For example, a normal ECG is as follows: Figure 2A As shown.

[0046] The controller 40 performs overall control, ensuring that each component can perform its function correctly. Such a controller 40 can be implemented in hardware, in software, or a combination of both. Preferably, the controller 40 can be implemented as a microprocessor, but it is not limited thereto.

[0047] In particular, when detecting the driver's stress level based on the driver's electrocardiogram, the controller 40 can perform various controls during the process of monitoring the driver's electrocardiogram, determining invalid intervals in the electrocardiogram based on its shape, and compensating for the electrocardiogram within the determined invalid intervals.

[0048] The controller 40 can read various information stored in the memory 10.

[0049] The controller 40 can access the vehicle network through the vehicle network access device 20 to obtain various information.

[0050] The controller 40 can control the electrocardiogram sensor 30 to measure the electrocardiogram of the vehicle driver.

[0051] The controller 40 can collect information about the road the vehicle is currently traveling on (e.g., road shape, road curvature, lanes, road type, etc.), route information (left turn, right turn, U-turn, etc.), road surface information (asphalt, unpaved, gravel road, etc.), speed bump information, accident information, speed information, etc. from the audio video navigation telematics (AVNT) system 200 set in the vehicle.

[0052] The controller 40 can acquire audio control information, video control information, navigation control information, and remote information processing control information of the vehicle driver by linking with the AVNT system 200 installed in the vehicle.

[0053] The controller 40 can obtain steering angle information of the steering wheel through the steering angle sensor 300 installed in the vehicle.

[0054] In the following text, reference will be made to Figures 2A to 2D Describe the operation of controller 40 in detail.

[0055] Figure 2A This is an example diagram of a normal electrocardiogram measured by an electrocardiogram sensor installed in a driver stress level detection device according to an embodiment of the present disclosure. Figure 2B This is an example diagram of an electrocardiogram containing invalid intervals, measured by an electrocardiogram sensor disposed in a driver stress level detection device according to an embodiment of the present disclosure. Figure 2C This is an example diagram illustrating the result of a controller installed in a driver stress level detection device according to an embodiment of the present disclosure compensating for an electrocardiogram within an invalid interval. Further, Figure 2D This is another example diagram illustrating the result of a controller in a driver stress level detection device according to an embodiment of the present disclosure compensating for an electrocardiogram in an invalid interval.

[0056] like Figure 2A As shown, the controller 40 can monitor whether a normal electrocardiogram (ECG) measured by the ECG sensor 30 has been taken within a reference time period. This is because a normal ECG measured within the reference time period is needed to determine the stress level of the vehicle driver.

[0057] The controller 40 can determine invalid regions based on the shape of the electrocardiogram (ECG) during monitoring of the ECG measured by the ECG sensor 30. As an example, such as... Figure 2BAs shown, the controller 40 can determine intervals (intervals β) that do not have the shape of an electrocardiogram as invalid intervals. Here, interval β is defined as follows: Figure 2B The time range that can be seen.

[0058] The controller 40 can compensate for the electrocardiogram within the determined invalid interval in the following two ways.

[0059] As the first method, such as Figure 2C As shown, the controller 40 can compensate for the ECG within the invalid interval β by extending the reference time α to perform additional ECG measurements.

[0060] As a second method, such as Figure 2D As shown, controller 40 can replace the ECG within the invalid interval β with the ECG measured immediately preceding the invalid interval β to compensate for the ECG within the invalid interval β. In other words, controller 40 can use the ECG measured immediately preceding the invalid interval β... p The ECG within the invalid interval β is replaced with the ECG within the invalid interval β. At this point, the length (time) of the invalid interval β and the immediately preceding interval β... p The length (time) is the same.

[0061] In one example, regarding the two compensation methods, the controller 40 can limit the time of the invalid interval β and determine whether to compensate for the invalid interval β based on the limited time.

[0062] As an example, when the duration of the invalid interval β is within a critical time (e.g., 5 seconds), the controller 40 can compensate for the electrocardiogram (ECG) in a first manner. In this case, during the ECG measurement within the reference time required to detect the driver's stress level, if the number of times the invalid interval β has occurred within the critical time exceeds a reference number (e.g., 2 times), the controller 40 can discard the previously measured ECG and remeasure it. That is, the controller 40 can reset the ECG measurement. Additionally, when the duration of the invalid interval β is greater than the critical time (e.g., 5 seconds), the controller 40 can terminate the detection of the driver's stress level.

[0063] As another example, when the invalid interval β is within a critical time (e.g., 5 seconds), the controller 40 can compensate for the electrocardiogram (ECG) in a second manner. In this case, during the ECG measurement within the reference time required to detect the driver's stress level, if the number of times the invalid interval β has occurred within the critical time exceeds a reference number (e.g., 2 times), the controller 40 can discard the previously measured ECG and remeasure it. That is, the controller 40 can reset the ECG measurement and begin a new ECG measurement. Additionally, when the invalid interval β is greater than the critical time (e.g., 5 seconds), the controller 40 can terminate the detection of the driver's stress level.

[0064] When the time limit of the invalid interval β is limited, the controller 40 can extend the critical time by an additional time (e.g., 2 seconds) when the vehicle driver has already performed operations on various functions of the vehicle.

[0065] When one of the following conditions is met: the steering angle of the vehicle's steering wheel exceeds the reference angle (e.g., 180°); the vehicle speed exceeds the reference speed (e.g., 150 km / h); the road surface condition of the road on which the vehicle is traveling is an unpaved road (dirt road, gravel road, etc.); or the number of speed bumps continuously located in front of the vehicle (e.g., within 10m) on the road on which the vehicle is traveling exceeds the reference number, the controller 40 may stop the electrocardiogram measurement or may not start the electrocardiogram measurement at all.

[0066] The controller 40 can determine the driver's stress level based on a compensated electrocardiogram. At this point, the technique of determining stress level based on electrocardiogram is a well-known and universal technique, so any technique can be used.

[0067] In one example, controller 40 can sense the vehicle driver's hands off in various ways.

[0068] As an example, the controller 40 can apply a test current (a current with a frequency of 500 Hz and equal to or less than 30 μA) to one of the two electrodes. When the same test current is sensed from the other electrode, it is determined that the vehicle driver is in a hands-on state, and when the same test current is not sensed from the other electrode, it is determined that the vehicle driver is in a hands-off state.

[0069] As another example, the controller 40 can determine whether the vehicle driver is in a hand-holding / hand-off state from an image of the vehicle driver captured by an infrared camera or a time-of-flight (ToF) camera located in the vehicle.

[0070] As another example, when the steering torque measured by the steering torque sensor located in the vehicle is irregular, the controller 40 can determine that the driver is holding the steering wheel, and when the steering torque sensor does not measure torque, it can determine that the driver is taking their hands off the steering wheel.

[0071] As another example, controller 40 can determine whether the vehicle driver is in a hands-on / hands-off state based on impedance changes measured by a capacitive sensor mounted on the steering wheel.

[0072] Figure 4 This is a flowchart of a driver stress level detection method according to an embodiment of the present disclosure.

[0073] First, the electrocardiogram sensor 30 uses electrodes set on the vehicle's steering wheel to measure the driver's electrocardiogram (401).

[0074] Subsequently, the controller 40 monitors the driver's electrocardiogram (402).

[0075] Subsequently, the controller 40 determines invalid regions in the electrocardiogram (403) based on the shape of the electrocardiogram.

[0076] Subsequently, the controller 40 compensates for the electrocardiogram within the determined invalid interval (404).

[0077] Figure 5 This is a block diagram illustrating a computational system for a driver's pressure level detection method according to an embodiment of the present disclosure.

[0078] Reference Figure 5 The driver stress level detection method according to embodiments of this disclosure can also be implemented by a computing system. The computing system 1000 may include at least one processor 1100, a memory 1300, a user interface input device 1400, a user interface output device 1500, a storage device 1600, and a network interface 1700 connected via a bus 1200.

[0079] Processor 1100 may be a central processing unit (CPU) or a semiconductor device that processes commands stored in memory 1300 and / or memory 1600. Memory 1300 and storage device 1600 may include various types of volatile or non-volatile storage media. For example, memory 1300 may include ROM (Read-Only Memory) 1310 and RAM (Random Access Memory) 1320.

[0080] Therefore, the operation of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware or software modules running on processor 1100, or through a combination thereof. The software modules can reside on storage media such as RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disks, solid-state drives (SSDs), removable disks, and CD-ROMs (i.e., memory 1300 and / or memory 1600). An exemplary storage medium is coupled to processor 1100, which can read information from and write information to the storage medium. In another approach, the storage medium can be integrated with processor 1100. The processor and storage medium can reside within an application-specific integrated circuit (ASIC). The ASIC can reside within a user terminal. In yet another approach, the processor and storage medium can reside as separate components in the user terminal.

[0081] The above description is merely an example of the technical concept of this disclosure, and various modifications and changes can be made by those skilled in the art without departing from the basic features of this disclosure.

[0082] Therefore, the embodiments disclosed herein are not intended to limit the technical concept of this disclosure, but are used to illustrate this disclosure, and the scope of the technical concept of this disclosure is not limited by the embodiments. The scope of this disclosure should be interpreted as being covered by the scope of the appended claims, and all technical concepts falling within the scope of the claims should be interpreted as being included within the scope of this disclosure.

[0083] According to the driver stress level detection device and method of the above-described embodiments of the present disclosure, when detecting the driver's stress level based on the driver's electrocardiogram, the device monitors the driver's electrocardiogram, determines invalid intervals in the electrocardiogram based on its shape, and compensates for the electrocardiogram within the determined invalid intervals, thereby minimizing the number of failed driver stress level detections and improving the accuracy of driver stress level detection.

[0084] In the foregoing, although the present disclosure has been described with reference to exemplary embodiments and accompanying drawings, the present disclosure is not limited thereto. Various modifications and changes can be made to the present disclosure by those skilled in the art without departing from the spirit and scope of the present disclosure as claimed in the appended claims.

Claims

1. A driver's stress level detection device, comprising: An electrocardiogram (ECG) sensor that uses electrodes positioned on the vehicle's steering wheel to measure the driver's ECG. as well as The controller is configured as follows: Monitor the driver's electrocardiogram; The time period is set based on the peak voltage that appears periodically in the electrocardiogram. The time period during which the peak voltage occurs periodically is defined as the effective time period; The time periods during which the peak voltage does not occur periodically are defined as invalid time periods; Compensate for electrocardiograms during invalid time periods. The controller is further configured to: Measure the driver's electrocardiogram during the valid time period; The electrocardiograms measured during the valid time period are compensated for during the invalid time period; The controller is further configured to perform the compensation when the time period corresponding to the invalid time period is within a critical time period.

2. The apparatus according to claim 1, wherein, The controller is configured to: When the time period corresponding to the invalid time period is longer than the critical time period, the detection of the driver's stress level is terminated.

3. The apparatus according to claim 1, wherein, The controller is configured to: When the number of invalid time periods within the critical time period exceeds the baseline number, the electrocardiogram measurement is reset.

4. The apparatus according to claim 1, wherein, The controller is configured to: When the time period corresponding to the invalid time period is limited to a critical time period, the critical time period is extended when no ECG of the driver is measured or when the driver's hand is sensed to have left the device.

5. The apparatus according to claim 1, wherein, The controller is configured to: The electrocardiogram (ECG) measurement shall be stopped when the steering angle of the vehicle exceeds the reference angle, when the speed of the vehicle exceeds the reference speed, when the road surface of the road on which the vehicle is traveling is an unpaved road, or when the number of speed bumps continuously located in front of the vehicle on the road exceeds the reference number.

6. A driver's stress level detection device, comprising: An electrocardiogram (ECG) sensor that uses electrodes positioned on the vehicle's steering wheel to measure the driver's ECG. as well as The controller is configured as follows: Monitor the driver's electrocardiogram; The time period is set based on the peak voltage that appears periodically in the electrocardiogram. The time period during which the peak voltage occurs periodically is defined as the effective time period; The time periods during which the peak voltage does not occur periodically are defined as invalid time periods; Compensate for electrocardiograms during invalid time periods. The controller is configured to replace the electrocardiogram (ECG) within the invalid time period with the ECG within the valid time period to compensate for the ECG within the invalid time period. The controller is further configured to perform the compensation when the time period corresponding to the invalid time period is within a critical time period.

7. The apparatus according to claim 6, wherein, The controller is configured to: When the time period corresponding to the invalid time period is longer than the critical time period, the detection of the driver's stress level is terminated.

8. The apparatus according to claim 6, wherein, The controller is configured to: When the number of invalid time periods within the critical time period exceeds the baseline number, the electrocardiogram measurement is reset.

9. The apparatus according to claim 6, wherein, The controller is configured to: When the time period corresponding to the invalid time period is limited to a critical time period, the critical time period is extended when no ECG of the driver is measured or when the driver's hand is sensed to have left the device.

10. The apparatus according to claim 6, wherein, The controller is configured to: The electrocardiogram (ECG) measurement shall be stopped when the steering angle of the vehicle exceeds the reference angle, when the speed of the vehicle exceeds the reference speed, when the road surface of the road on which the vehicle is traveling is an unpaved road, or when the number of speed bumps continuously located in front of the vehicle on the road exceeds the reference number.

11. A method for detecting a driver's stress level, comprising: The controller monitors the driver's electrocardiogram; The controller sets a time period based on the peak voltage that appears periodically in the electrocardiogram; The controller determines the effective time period as the time period during which the peak voltage occurs periodically; The controller defines the time periods during which the peak voltage does not occur periodically as invalid time periods; The controller compensates for electrocardiograms during invalid time periods. Compensation for electrocardiograms during invalid time periods includes: Measure the driver's electrocardiogram during the effective time period; ECGs measured during the valid time period are compensated for during the invalid time period by using ECGs measured during the valid time period. The measurement of the driver's electrocardiogram includes: The compensation is performed when the time period corresponding to the invalid time period is within the critical time period; When the time period corresponding to the invalid time period is longer than the critical time period, the detection of the driver's stress level is terminated; and When the number of invalid time periods within the critical time period exceeds the baseline number, the electrocardiogram measurement is reset.

12. The method according to claim 11, wherein, Measuring the driver's electrocardiogram further includes: When the driver's vehicle manipulation is sensed, the critical time period is extended; and The electrocardiogram (ECG) measurement shall be stopped when the steering angle of the vehicle exceeds the reference angle, when the speed of the vehicle exceeds the reference speed, when the road surface of the road on which the vehicle is traveling is an unpaved road, or when the number of speed bumps continuously located in front of the vehicle on the road exceeds the reference number.

13. A method for detecting a driver's stress level, comprising: The controller monitors the driver's electrocardiogram; The controller sets a time period based on the peak voltage that appears periodically in the electrocardiogram; The controller determines the effective time period as the time period during which the peak voltage occurs periodically; The controller defines the time periods during which the peak voltage does not occur periodically as invalid time periods; The controller compensates for the ECG within invalid intervals. The compensation for the electrocardiogram (ECG) during the invalid time period includes replacing the ECG during the invalid time period with an ECG during the valid time period, thereby compensating for the ECG during the invalid time period. The replacement of the electrocardiogram during the invalid time period includes: The compensation is performed when the time period corresponding to the invalid time period is within the critical time period; When the time period corresponding to the invalid time period is longer than the critical time period, the detection of the driver's stress level is terminated; and When the number of invalid time periods within a predetermined time exceeds a baseline number, the electrocardiogram measurement is reset.

14. The method according to claim 13, wherein, Replacing the electrocardiogram during the invalid time period further includes: When the driver's vehicle manipulation is sensed, the predetermined time period is extended; and The electrocardiogram (ECG) measurement shall be stopped when the steering angle of the vehicle exceeds the reference angle, when the speed of the vehicle exceeds the reference speed, when the road surface of the road on which the vehicle is traveling is an unpaved road, or when the number of speed bumps continuously located in front of the vehicle on the road exceeds the reference number.

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