DOOSING WARNING DEVICE

Abstract

Drowsing warning device (1) mounted on a vehicle for preventing a driver from falling asleep, comprising: a drowsiness level determining unit (9) configured to determine a drowsiness level of the driver, a preliminary warning unit configured to perform a preliminary warning in response to the drowsiness level being higher than a warning threshold based on a comparison of the drowsiness level determined by the drowsiness level determining unit (9) with a warning threshold, a warning unit configured to issue a main warning prompting the driver to wake up from drowsiness, if necessary, after the preliminary warning provided by the preliminary warning unit, a response detection unit configured to detect that the driver has performed a predetermined response action within a specified time after the preliminary warning is performed by the preliminary warning unit, and a threshold changing unit configured to change the warning threshold to a higher value in response to the predetermined response action being detected by the response detecting unit, characterized in that the dozing warning device (1) further comprises: a random preliminary warning unit configured to randomly perform the preliminary warning in a state where the drowsiness level determined by the drowsiness level determining unit (9) is equal to or less than the warning threshold, where: the threshold changing unit is configured to set the warning threshold to a smaller value in response to the predetermined response action by the driver not being detected by the response detecting unit within a specified time after the preliminary warning is randomly performed.

Description

Technical field

[0001] The present invention relates to a doze warning device mounted on a vehicle such as a car, a truck, a bus, for preventing a driver from falling asleep. background

[0002] JP 2008 - 206 688 A describes a doze warning device for preventing a driver from falling asleep as follows. That is, a driver's face is photographed by a camera, and the driver's drowsiness level is estimated from a change in the degree of the driver's eyelid opening and / or a change in the blinking pattern through image processing. If the drowsiness level then exceeds a threshold, a preliminary warning is issued. This preliminary warning is output by outputting white noise from a speaker. In response to generating the white noise as a preliminary warning, the device is configured to determine the driver's response to the white noise or the driver's response from a change in the driver's facial expression or line of sight. If the driver's response is detected within the time limit, generation of the main warning is delayed.If the driver's response is not detected even after the time limit has expired, the main alarm is generated. This can reduce the occurrence of unnecessary warnings.

[0003] A driver's drowsiness is affected by individual differences, physical condition, mental state, and the like, and the estimation result does not always match the driver's subjective view. With the dozing warning device configured as described above, there is a possibility that the threshold drowsiness level at which the preliminary warning is generated may not match the driver's subjective view. For some drivers, a preliminary warning is issued in a state where drowsiness has progressed, so the driver feels that the timing of the warning is too late. In contrast, for other drivers, a preliminary warning is issued in a state where the driver is fully awake, and the driver feels disturbed.

[0004] Further devices of this type are also known from DE 10 2008 010 515 A1, JP 2008 - 204 056 A and US 5 694 116 A.

[0005] It is an object of the present invention to provide a drowsiness warning device that performs a warning at a drowsiness level that is more consistent with the feeling of drowsiness of a driver.

[0006] The object is achieved by the dozing warning device having the features according to claim 1. Advantageous embodiments are the subject of the dependent claims.

[0007] According to one aspect, a doze warning device to be mounted on a vehicle for preventing a driver from falling asleep is provided. The doze warning device includes a drowsiness level determining unit, a preliminary warning unit, a warning unit, a response detecting unit, and a threshold changing unit. The drowsiness level determining unit is configured to determine a drowsiness level of the driver. The preliminary warning unit is configured to perform a preliminary warning in response to the drowsiness level being higher than a warning threshold based on a comparison of the drowsiness level determined by the drowsiness level determining unit with the warning threshold.The warning unit is configured to issue a main warning prompting the driver to awaken from drowsiness if necessary after the preliminary warning is issued by the preliminary warning unit. The response detection unit is configured to detect that the driver has performed a predetermined response action within a predetermined time after the preliminary warning is issued by the preliminary warning unit. The threshold change unit is configured to change the change threshold to a higher value in response to the response detection unit detecting the predetermined response action.

[0008] According to the above configuration, the drowsiness level determination unit determines the driver's drowsiness level. When the drowsiness level increases beyond the warning threshold, a preliminary warning is performed by the preliminary warning unit. The response detection unit detects that the driver has performed a predetermined response action within a specified time after the preliminary confirmation is issued by the preliminary confirmation unit. As a result, the threshold change unit changes the warning threshold to a higher value. In contrast, if the response detection unit does not detect that the driver has performed a predetermined response action after the preliminary warning is issued by the preliminary warning unit, the warning unit performs a main warning, prompting the driver to awaken from drowsiness.At this time, the threshold is not changed by the threshold changing unit and the warning threshold is kept as it is.

[0009] If the driver responds to the preliminary warning, the driver is not drowsy. It can be said that the warning threshold that triggered the preliminary warning was relatively low from the driver's subjective perspective. In other words, if the response detection unit detects the response, a preliminary warning can be provided with the subsequent warning threshold set to a higher value to better match the driver's perception. If the response detection unit does not detect a response, the driver's drowsiness may have progressed, so it can be said that the warning threshold is appropriate. At this time, the warning unit performs the main warning and prompts the driver to wake up. Consequently, it is possible to appropriately adjust the warning threshold for the driver's drowsiness level while driving the vehicle.It is possible to issue a warning appropriately at the level of drowsiness that better matches the driver's perception. Short description of the characters

[0010] The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. Fig. 1 is a block diagram schematically showing an electrical configuration of a doze warning device according to an embodiment, Fig. 2 is a flowchart illustrating a processing procedure of a dozing warning performed by the control device, Fig. 3 a graph showing an example of a change in sleepiness level over time, and Fig. 4 is a diagram for explaining another method for determining whether the warning determination flag is valid or invalid according to another embodiment. Embodiments for carrying out the invention

[0011] An embodiment is described below with reference to the Fig. 1 to 3. Fig. 1 schematically shows an electrical configuration of a drowsing warning device 1 according to the present embodiment. The drowsing warning device 1 is mounted on a vehicle, such as a car, a bus, or a truck. The drowsing warning device 1 includes a drowsing warning control device 2 and other components communicatively connected to the drowsing warning control device 2. The other components include a camera 3, a microphone 4, an action switching unit 5, a speaker 6, a display device 7, and a ventilation device 8.

[0012] The drowsiness warning control device 2 is mainly configured by a computer. As an example of the present embodiment, such a computer includes CPU, ROM, RAM, and the like, and controls each function by executing a drowsiness warning determination program to realize the functions as the drowsiness warning device 1. Here, the drowsiness warning control device 2 is configured to include a drowsiness level determination unit 9 and a warning control unit 10. The camera 3 is provided, for example, near a measuring unit in front of the driver's seat in the passenger compartment and photographs, for example, the driver's face above the chest. The camera 3 is controlled by the image processing unit 11, and photographing data by the camera 3 is input to the image processing unit 11 to perform image processing.The image data processed by the image processing unit 11 is input to the doze warning control device 2.

[0013] The microphone 4 is used by a driver to input voice and is provided near a driver's seat. The action switching unit 5 is operated by a driver and includes, for example, a plurality of mechanical switches and a touch panel. The action switching unit 5 is provided near the driver's seat, such as in the center console and the steering wheel. The signals from the microphone 4 and the action switching unit 5 are also input to the doze warning control device 2.

[0014] The speaker 6 is provided in the passenger compartment and outputs sounds and is controlled by an audio control unit 12. The audio control unit 12 causes the speaker 6 to output sounds for warning based on a command from the doze warning control device 2, as described later. At this time, an audio memory 13, in which voice data used for a preliminary warning, which will be described later, is stored, is removably inserted in the audio control unit 12. The audio memory 13 uses, for example, a serial flash memory or an SD card.

[0015] The display device 7 is provided, for example, in a center console and performs various displays for a driver. Based on a command from the doze warning control device 2, necessary display related to the doze warning is performed. The display device 7 and the action switching unit 5 may be integrated. The ventilation device 8 is used as another device when performing a main warning as described below. The ventilation device 8, for example, sends a fragrance or cool air from the driver's seatback or headrest portion toward the driver's face to prompt the driver to wake up. The ventilation device 8 operates in cooperation based on a command from the doze warning control device 2.

[0016] In the present embodiment, the drowsiness level determination unit 9 in the drowsiness warning control device 2, as described later in the operation description, further determines the level of drowsiness of the driver. Based on a comparison of the drowsiness level with the warning threshold TH (see Fig. 3) It is determined whether the drowsiness level is higher than the warning threshold TH. If the drowsiness level exceeds the warning threshold TH, that is, if the warning determination flag becomes valid, the warning control unit 10 performs a preliminary warning.

[0017] The warning control unit 10 then determines whether the driver has performed a predetermined response action within a specified time after the preliminary warning is issued. If a response action is not detected within the specified time, the main warning is performed to prompt the driver to awaken from drowsiness. Conversely, if a response action is detected within the specified time after the preliminary warning is issued, the drowsiness level determination unit 9 changes the warning threshold TH to a higher value.

[0018] Specifically, when the drowsiness level determining unit 9 determines the driver's drowsiness level, the camera 3 captures an image of the driver's face. From the photographed image data, a change in the driver's eyelid opening degree and / or a change in the blinking pattern are obtained through image processing. The driver's drowsiness level is determined based on the result. In this case, the drowsiness level is determined by a numerical value, for example, a numerical value from 0.0 to 5.0, which increases as the degree of drowsiness increases. Since the method for determining the drowsiness level is a well-known technique, a detailed description is omitted.

[0019] The drowsiness level determining unit 9 compares the determined drowsiness level with the warning threshold TH to determine whether the driver has a determined drowsiness. In such a determination, the present embodiment uses, for example, the following method. That is, the determined drowsiness level is buffered at predetermined time intervals, for example, every second, to obtain the drowsiness level buffered in a time series. In the drowsiness level buffered in a time series, a predetermined width of a determination time window is obtained. If all drowsiness levels in such a predetermined width of determination time window data exceed the warning threshold TH (for example, 3.0), the warning determination flag becomes valid.When the warning determination flag becomes valid, it is determined that the driver has a certain level of drowsiness, and the warning control device 10 performs a preliminary warning. In addition, even if the warning determination flag becomes continuously valid, the next preliminary warning is performed at a specified time interval (for example, approximately several seconds to several tens of seconds) after the previous preliminary warning is performed.

[0020] In the present embodiment, the preliminary warning is performed by asking the driver to output a voice based on the voice data. In this case, the warning control unit 10 outputs a command signal to the audio control unit 12. The audio control unit 12 reproduces the voice data stored in the audio memory 13 and causes the speaker 6 to output a voice for a question. The wording of the question is, for example, "Are you tired?", "Were you tired?" In this case, the voice data stored in the audio memory 13 may be rewritten. Instead of a synthetic voice or the like, a voice of a person the driver knows, for example, a voice of a family member, a lover, a friend, a boss of a company, or the like, may be used as the voice used for the preliminary warning.

[0021] When the driver who heard the preliminary warning is in a state of alertness (not experiencing much drowsiness), the driver performs a predetermined response action within a specified time (for example, approximately several seconds) so as not to proceed to the main warning. It is assumed here that the driver performs a predetermined gesture as a response action by the driver. For example, the driver makes a gesture of holding his / her hand in front of the camera 3, shaking his / her head up / down, shaking his / her head left / right, or opening his / her mouth. The warning control device 10 detects whether a predetermined response action has been performed, that is, whether any of the gestures described above have been performed, based on image recognition based on image data captured by the camera 3.

[0022] The warning control unit 10 performs the main warning when a response action by the driver, that is, a predetermined gesture, is not detected even after a specified time has elapsed since the preliminary warning was issued. In this main warning, for example, a sound that awakens the driver, such as a beep, is output from the speaker 6. In the present embodiment, in addition, the fragrance or cool air is sent toward the driver's face through the ventilation device 8. Further, a warning display is made, for example, on the screen of the display device 7 to prompt the driver to take a break.

[0023] On the other hand, if the warning control unit 10 detects a response action by the driver within a specified time, the drowsiness level determination unit 9 changes the warning threshold TH to a higher value. As a result, the next time, the preliminary warning can be determined to be performed for a deeper level of drowsiness. Specifically, the numerical value of the warning threshold TH is increased, for example, by 0.1. If the current warning threshold TH is 3.0, the warning threshold TH is set to 3.1 next time.

[0024] Further, assume a case where a state where the determination by the drowsiness level determination unit 9 is equal to or less than the warning threshold TH (i.e., the state where the warning determination flag remains invalid) may continue. In the present embodiment, in such a case, the drowsiness warning control device 2 performs a random preliminary warning in response to such a state having continued for a predetermined time or longer, for example, 30 minutes or more. This random preliminary warning is also performed in the same manner as the preliminary warning described above. If the driver, having heard the preliminary warning, performs a predetermined response action, i.e., a predetermined gesture, within a predetermined time, the main warning is not performed.If the driver's response action is not detected, the main warning is carried out as described above.

[0025] When the random preliminary warning is performed, the driver who has heard the preliminary warning can perform a predetermined response action (gesture) within a specified time. In such a case, the warning threshold TH is not increased, and the numerical value of the warning threshold TH remains unchanged. Then, when the main warning is performed after the random preliminary warning, the drowsiness level determining unit 9 changes the warning threshold TH to a lower value. As a result, the next time the preliminary warning is determined, the preliminary warning for lighter drowsiness is issued. Specifically, the numerical value of the warning threshold TH is reduced, for example, by 0.1. If the current warning threshold TH is 3.0, the next time the warning threshold TH is set to 2.9.

[0026] Next, the operation of the doze warning device 1 having the above configuration will be described with reference to Fig. 2 and Fig. 3. The flow chart in Fig. 2 schematically illustrates a processing procedure for determining a driver's drowsiness level and performing a warning by the dozing warning control device 2 while the vehicle is running (while ACC is on). That is, in step S1, the driver's drowsiness level is first determined and buffered. In step S2, the drowsiness levels are determined with reference to a plurality of data within a predetermined width of a determination time window. In step S3, it is determined whether all the drowsiness levels within the determination time window have exceeded the warning threshold TH (for example, 3.0). If the drowsiness levels do not exceed the warning threshold TH (No in step S3), the processing proceeds to step S9, which will be described later.

[0027] If the drowsiness level exceeds the warning threshold TH, that is, if the warning determination flag is valid (Yes in step S3), a preliminary warning is performed in step S4. The preliminary warning is issued by asking the driver through voice, as described above. Fig. Figure 3 shows an example of how the drowsiness level changes over time. If a condition in which the drowsiness level exceeds the warning threshold TH persists for the determination time window WN, the warning determination flag becomes valid and the preliminary warning is performed. In the case of Fig. 3, a preliminary warning is issued at a time t1, at a time t2 and at a time t3. A segment that Fig. 3 indicated by hatching is a segment in which the warning marking is valid.

[0028] In the next step S5, it is determined whether a predetermined response action has not been performed by the driver within a specified time (for example, approximately several seconds). The response action by the driver is, as described above, one of predetermined gestures (i) holding his / her hand in front of the camera 3, (ii) shaking his or her head up / down, (iii) shaking his / her head left / right, and (iv) opening a mouth (or opening / closing a mouth). In this case, if the driver is in a sufficiently alert state, it is possible to easily perform a response action by listening to the speech of the preliminary warning, i.e., the question. However, if the driver's drowsiness is high, a predetermined gesture cannot be immediately performed even if the preliminary warning is heard.

[0029] If the driver does not perform the specified gesture within a specified time after the preliminary warning is issued, it is determined that there is no response action (No in step S5), and the main warning is generated in the next step S6. In this main warning, as described above, a warning sound is emitted and air is blown into the driver's face to prompt the driver to wake up. In step S7, the warning threshold TH is left as it is, and the processing of step S1 is repeated.

[0030] On the other hand, if there is a response action by the driver within a predetermined time after the preliminary warning is issued (Yes in step S5), the processing proceeds to step S8. The warning threshold TH is changed by 0.1 to a value larger than the current value. As a result, the warning threshold TH is changed to a larger value so that the preliminary warning determination is issued at a deeper level of drowsiness next time. Further, at this time, the processing of step S1 is repeated without issuing the main warning.

[0031] Here, if the driver responds to the preliminary warning without difficulty, the driver is not drowsy. It can be said that the warning threshold TH that triggered the preliminary warning was relatively low from the driver's subjective perspective. In other words, if a response action to the preliminary warning is detected, a preliminary warning can be provided with the subsequent warning threshold set to a higher value to better match the driver's perception. Consequently, by increasing the warning threshold TH, the warning threshold TH is corrected to a value suitable for the driver. If there is no detection of the driver's response action to the preliminary warning, it can be said that the driver's drowsiness has progressed, and it can thus be said that the warning threshold is appropriate.

[0032] In the present embodiment, a random preliminary warning is performed in addition to the preliminary preservation based on the determination of the driver's drowsiness level. That is, if the determined driver's drowsiness level is a relatively low value equal to or less than the warning threshold TH in step S3 described above (No in step S3), the processing in step S9 is performed. That is, to determine whether to perform a random preliminary warning, the time during which the state without the preliminary warning continues is counted. In the next step S10, it is determined whether the state without a preliminary warning has continued for a predetermined time (for example, 30 minutes to 2 hours). If the state has not continued for a predetermined time or longer (No in step S10), the processing returns to step S1.

[0033] On the other hand, if the state without the preliminary warning has continued for a predetermined time (Yes in step S10), in step S11, the preliminary warning is performed by questioning by outputting a voice. In the next step S12, it is determined whether a predetermined response action by the driver, that is, a predetermined gesture, has been performed within a predetermined time. In this case, it is assumed in most cases that if the driver is in the awake state, the driver can easily perform a response action by listening to the voice (question) of the preliminary warning. If there is a response action by the driver within a predetermined time after the preliminary warning is output (Yes in step S12), the processing proceeds to step S13. In step S13, the warning threshold TH is left as it is, and the processing of step S1 is repeated.

[0034] However, if the driver is experiencing drowsiness, there may be a case where a predetermined gesture cannot be performed immediately even if the preliminary warning is heard. If the response action has not been performed (No in step S12), the main warning is performed in step S14. In the next step S15, the warning threshold TH is then changed by 0.1 to a value lower than the current value. As a result, the warning threshold TH is changed to a low value, so that the preliminary warning determination is issued next time at a lighter drowsiness. Subsequently, the processing of step S1 is repeated.

[0035] If the driver's response to the random preliminary warning is not detected here, it is assumed that the driver's drowsiness has progressed. Nevertheless, the normal preliminary warning was not performed beforehand. From the driver's subjective perspective, the warning threshold TH was therefore too high up to this point. By lowering the warning threshold TH, the warning threshold TH is therefore corrected to a value suitable for the driver. If the driver's response to the random preliminary warning is detected, it is assumed that the driver is awake, so the warning threshold TH is assumed to be appropriate.

[0036] According to the drowsiness warning device 1 of the present embodiment, the following effects can be obtained as described above. That is, in the present embodiment, the drowsiness warning control device 2 determines the driver's drowsiness level while driving the vehicle. When the warning threshold TH is exceeded, that is, when the goods determination flag becomes valid, a preliminary warning is issued. At this time, within a specified time after the preliminary warning is issued, it is detected whether the driver has performed a predetermined response action. If a response action is detected, the warning threshold TH is changed to a higher value. Consequently, an excellent effect can be obtained in which the preliminary warning and the main warning are appropriately performed at a drowsiness level that better matches the driver's feeling while driving the vehicle.

[0037] Furthermore, in the present embodiment, a preliminary warning is also randomly performed at an appropriate time even in the state where the warning determination flag remains invalid or in the state where a preliminary warning triggered by determining the driver's drowsiness level or comparing it with the warning threshold TH is not performed. In addition, when a predetermined response action by the driver to the preliminary warning is not detected, the main warning is performed to prompt the driver to wake up, and the warning threshold TH is changed to a lower value. It is therefore possible to set the warning threshold TH more appropriately. The random preliminary warning is additionally performed in response to the preliminary warning not being performed for a predetermined time or longer.It is therefore possible to prevent the frequency at which the random preliminary warning is issued from occurring too frequently, causing the driver to feel disturbed. Conversely, it is possible to prevent the frequency from being too low, rendering the preliminary warning meaningless.

[0038] Specifically, in the present embodiment, the preliminary warning is configured to prompt the driver through the voice output based on the voice data. It is thereby possible to provide a stimulus to the driver through questions at the preliminary warning and return to the awake state or maintain the awake state. In this case, the voice data is configured to be rewriteable. Therefore, for example, the voice of a person who knows the driver, such as a family member, lover, friend, boss of a company, or the like, can also be used as the voice for the preliminary warning. Thus, a sense of security and stimulus can be provided to the driver, and a more effective preliminary warning can be issued.

[0039] Further, in the present embodiment, a predetermined gesture is specifically adopted as a predetermined response action by the driver to the preliminary warning. Accordingly, the response action by the driver can be easily completed, and the driver's awake state can be maintained by performing the gesture. Further, in the present embodiment, a voice warning is issued as the main warning for prompting the driver to awaken from drowsiness. In addition, it is possible to address a tactile perception of the driver or the like by cooperating with another device (for example, the ventilation device 8). Thus, awakening can be more effectively assisted.

[0040] Fig. 4 shows another embodiment. The present embodiment differs from the above embodiment in a method for determining whether the driver's drowsiness level determined by the drowsiness level determining unit 9 has exceeded the warning threshold TH (i.e., a method for determining whether the warning determination flag is valid or invalid). That is, in the present embodiment, the drowsiness level determined by the drowsiness level determining unit 9 from the captured image of the driver's face is also buffered in a time series at regular intervals, for example, every second. Fig. 4 shows the sleepiness level determination data. In Fig. 4 "OK" indicates that there is no drowsiness, that is, it indicates a state where it is determined that the drowsiness level is equal to or less than the warning threshold TH. "NG" indicates a state where the drowsiness level exceeds the warning threshold TH, so drowsiness is determined. "?" indicates a state where a determination cannot be made, for example, the driver's face could not be detected.

[0041] At each output cycle (in this case 1 second), the data is then traced back through the data of a given time window (in Fig. 4 by a predetermined number of data, for example, 10 as the determination time window). The total time of "NG" is obtained. When the total time of "NG" is equal to or greater than a time threshold (for example, 12 seconds), the warning determination flag is validated, and a preliminary warning is issued. Even with such a configuration, a preliminary warning can be performed as in the above embodiment. A case where the warning determination flag is continuously valid is assumed. Even in such a case, after the previous preliminary warning is performed, for example, the preliminary warning is performed at intervals of several seconds to several tens of seconds.

[0042] In addition, although illustration is omitted, the following changes are also possible as an embodiment. That is, in the above embodiment, the warning threshold TH is changed only once by detecting the response action to the normal preliminary warning (steps S5 and S8 in Fig. 2). However, the configuration may be such that the warning threshold TH is changed if a response action is detected multiple times (for example, twice) after the preliminary warning. Accordingly, detecting only one response action does not result in a change in the warning threshold TH. Consequently, it is possible to rule out the possibility of the warning threshold TH being changed due to, for example, an accidental occurrence. The change in the warning threshold TH is performed more appropriately.

[0043] In the above embodiment, the gesture is adopted as the predetermined response action by the driver to the preliminary warning. A response with a predetermined speech can be performed as a response action. It can be configured so that, based on the detection of the speech acquired by the microphone 4, it is detected whether a predetermined response action has been performed. Accordingly, the driver performs a predetermined response by speech (e.g., "OK," "not tired," etc.) as a response action to the preliminary warning. As a result, a conversation is established, and the driver's alertness can be maintained by the stimulus of the conversation. As a response action, the driver can perform a predetermined action on the action switching unit.

[0044] In the above embodiment, if the preliminary warning has not been performed for a set time or longer, the random preliminary warning is performed. However, the configuration may be such that the driver can change the set time. This makes it possible to set the timing (time interval) at which the random preliminary warning is performed according to conditions such as a driver's preference and necessity. In the above-described embodiment, the main warning further uses another device, such as a ventilation device 8 that provides a blower.Such other device may include a vibration device provided at a rear portion of the seat or the steering wheel and applying vibration to the driver, a device providing tightening of a driver's seat belt, a lighting device providing a light stimulus such as illumination, and a visual field display displayed on the windshield to promote awakening.

[0045] When a vehicle is driven by a plurality of drivers, it is preferable to provide a warning threshold TH for each driver. In this case, the warning threshold TH is set and stored for each driver. At the start of driving, a driver identification unit is provided that identifies the driver through authentication of a face, fingerprint, palmprint, etc. The warning threshold TH for the driver identified by the driver identification unit can be read and used. In addition, in the above embodiment, the numerical values of the drowsiness level, the numerical value of the warning threshold TH, and the numerical values for each time are merely examples, and various changes may be made.The method for determining driver drowsiness, the preliminary warning mode, the main warning mode, and the like can be appropriately changed and performed.

[0046] While the present invention has been described with reference to the embodiments thereof, it should be understood that the invention is not limited to the embodiments and constructions. The present invention encompasses various modifications and variations within the range of equivalence. Various combinations and forms, and further, other combinations and forms including more or fewer elements or only a single element are also included within the scope and spirit of the present invention.

Claims

[1] Drowsing warning device (1) mounted on a vehicle for preventing a driver from falling asleep, comprising: a drowsiness level determining unit (9) configured to determine a drowsiness level of the driver, a preliminary warning unit configured to perform a preliminary warning in response to the drowsiness level being higher than a warning threshold based on a comparison of the drowsiness level determined by the drowsiness level determining unit (9) with a warning threshold, a warning unit configured to issue a main warning prompting the driver to wake up from drowsiness, if necessary, after the preliminary warning provided by the preliminary warning unit, a response detection unit configured to detect that the driver has performed a predetermined response action within a specified time after the preliminary warning is performed by the preliminary warning unit, and a threshold changing unit configured to change the warning threshold to a higher value in response to the predetermined response action being detected by the response detecting unit, characterized by , that the dozing warning device (1) further comprises: a random preliminary warning unit configured to randomly perform the preliminary warning in a state where the drowsiness level determined by the drowsiness level determining unit (9) is equal to or less than the warning threshold, where: the threshold changing unit is configured to set the warning threshold to a smaller value in response to the predetermined response action by the driver not being detected by the response detecting unit within a specified time after the preliminary warning is randomly performed. [2] Dozing warning device (1) according to claim 1, wherein: the threshold changing unit is configured to change the warning threshold in response to the response detecting unit consecutively detecting a plurality of response actions. [3] Dozing warning device (1) according to claim 1 or 2, wherein: the preliminary warning unit is configured to provide the preliminary warning by asking the driver questions with a speech output based on speech data. [4] Dozing warning device (1) according to claim 3, wherein: the speech data is configured to be rewriteable. [5] Dozing warning device (1) according to one of claims 1 to 4, wherein: the driver’s predetermined response to the preliminary warning comprises a predetermined gesture, and the response detection unit is configured to detect whether the specified response action has been carried out on the basis of image recognition by a camera (3). [6] Dozing warning device (1) according to one of claims 1 to 4, wherein: the driver’s predefined response action to the preliminary warning includes a predefined voice response, and the response detection unit is configured to detect whether the predetermined response action has been performed based on a recognition of a speech obtained by a microphone (4). [7] Dozing warning device (1) according to claim 1, wherein: the random preliminary warning unit is configured to randomly perform the preliminary warning in response to the preliminary warning not being performed for a specified time or longer, and the set time can be changed. [8] Dozing warning device (1) according to one of claims 1 to 7, wherein: the warning unit is configured to carry out the main warning, which requests the driver to wake up from drowsiness, in cooperation with another device (8) mounted on the vehicle. [9] Dozing warning device (1) according to one of claims 1 to 8, further comprising: a driver identification unit configured to identify the driver, wherein the warning threshold is set for the identified driver.

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