JPH11115710A - Fail-safe device in follow-up traveling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fail-safe device in a follow-up traveling system for a vehicle, which can be realized at a low cost, certainly judges the lowering of the awakening degree of a driver due to follow-up traveling, especially, in a low speed range, and can take suitable action. SOLUTION: This fail-safe device is provided with a shift lever actuator 5 which forcibly operates a shift lever for changing over the traveling range of the automatic transmission of a vehicle, and a control circuit 10 which forcibly changes over to a first seed range or a second speed range by the shift lever actuator 5 in the case that a speed becomes less than a first set value (10 km/h), and restricts the speed not to increase without exceeding a second set value and also operates a warning device 6 by judging that the awakening degree of the driver is lowered in the case that the shift lever is not operated within a D range regardless of such a state that the speed should be increased by exceeding the second set value (20 km/h).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a follow-up running system for automatically controlling the accelerator and brake of a vehicle so as to keep the inter-vehicle distance substantially constant and adjusting the vehicle speed, and monitors the degree of awakening of the driver during the follow-up running. A fail-safe device.

[0002]

2. Description of the Related Art In recent vehicle control technology, adaptive cruise control (ACC) that automatically controls a distance between a vehicle and a preceding vehicle during traveling to automatically keep the distance between the vehicles ahead substantially constant.
l) has been put to practical use. However, those currently in practical use are usually provided with a traveling speed limit of 40 km / h or more.

Further, a congestion follow-up control system that follows a preceding vehicle even during low-speed traveling such as congestion, and a system that automatically controls handling at this time, have been proposed. When the operation of the accelerator and the brake (further, the steering wheel) is automated, there is a concern that the driver's arousal level is considerably reduced because the amount of driving operation and matters to be noted are considerably reduced.

As a prior art for detecting the degree of awakening of a driver, a pressure sensor is provided on a steering wheel to monitor the gripping force (Japanese Patent Laid-Open No. 1-190545).
A method has been proposed in which the state of the driver (face direction) is monitored by a visual sensor and image processing (for example, page 87 of the 2nd Image Sensing Symposium Lecture on June 13 and 14, 1996).

[0005]

However, each of the above-mentioned conventional arousal level detection techniques has the following problems.

(1) That is, first, there is a problem that the degree of awakening of a driver cannot always be determined accurately.
First of all, the normal gripping force of the steering varies depending on the personality of the driver and the driving situation, and the variation is large, so that the awakening level is lowered even if the gripping force is always smaller than the set threshold value. It is not always true. In addition, the direction of the driver's face also varies depending on the driver's personality and driving conditions, and it is difficult to determine whether the change is normal or due to a decrease in arousal level. .

(2) In each case, a special sensor and a signal processing device are required, and there is a problem in that realization is considerably costly.

Accordingly, the present invention has been made in view of such conventional problems, and can be realized at low cost, and in particular, it is possible to reliably determine a decrease in the driver's arousal level due to following running in a low speed range. The purpose of the present invention is to provide a fail-safe device in a follow-up traveling system in which adaptive measures can be taken.

[0009]

According to a first aspect of the present invention, there is provided a fail-safe device for following a traveling system, comprising: an inter-vehicle distance detecting means for detecting a distance to a preceding vehicle; Vehicle speed control means for automatically controlling the accelerator and brake of the vehicle so as to keep the distance detected by the distance detection means substantially constant, and adjusting the vehicle speed. A fail-safe device for monitoring a degree of awakening of a driver, a shift lever actuator for forcibly operating a shift lever for switching a travel range of an automatic transmission of a vehicle to switch the travel range, and a vehicle speed set to a first setting. When the low speed range is equal to or less than the value, the shift lever actuator is controlled to operate the shift lever, and the A shift lever control means for switching to a first speed range or a second speed range; and a vehicle speed adjusted by the vehicle speed control means unless the shift lever is detected to be in a drive range position. Vehicle speed restriction control means for restricting the magnitude from increasing beyond the second set value having the above-mentioned magnitude.

According to a second aspect of the present invention, there is provided a fail-safe device in a following running system, wherein the following distance detecting means detects a distance to a preceding vehicle, and the distance detected by the following distance detecting means in the following running mode is made substantially constant. A vehicle speed control means for automatically controlling the accelerator and brakes of the vehicle to maintain the vehicle speed and adjusting the vehicle speed, and in a vehicle follow-up traveling system, a fail-safe device for monitoring the degree of awakening of the driver during the follow-up traveling. A shift lever actuator for forcibly operating a shift lever for switching a travel range of the automatic transmission of the vehicle to switch the travel range, and a shift lever actuator for switching a travel range to a low speed range in which a vehicle speed is equal to or less than a first set value. The shift lever actuator is controlled to operate the shift lever to forcibly switch to the first speed range or the second speed range. Shift lever control means and the vehicle speed adjusted by the vehicle speed control means should be increased beyond a second set value which is greater than or equal to the first set value. Based on the fact that the lever is not detected at the position of the drive range, a wakefulness determination unit that determines a decrease in the wakefulness of the driver,
When the arousal level determining means determines that the driver's arousal level is low, the apparatus is provided with an alarm means for giving an alarm to the driver.

According to a third aspect of the present invention, there is provided a fail-safe device in the following traveling system, wherein the following traveling system comprises:
The vehicle further includes a steering control means for automatically controlling a steering device of the vehicle in the following traveling mode.

According to a fourth aspect of the present invention, there is provided a fail-safe device in the follow-up traveling system, wherein the steering control means functions only when the vehicle speed is in a low speed range equal to or less than the first set value, and the steering device of the vehicle is provided. It is characterized by automatic control.

According to a fifth aspect of the present invention, there is provided the fail-safe device in the follow-up traveling system, wherein the warning means gives a warning to the driver by voice.

According to a sixth aspect of the present invention, there is provided the fail-safe device in the follow-up traveling system, wherein the warning means gives a warning to the driver by a warning sound.

Further, in the fail-safe device according to the seventh aspect of the present invention, the warning means gives a warning to the driver by character display.

The fail-safe device in the follow-up traveling system according to claim 8 is characterized in that the warning means gives a warning to the driver by displaying an image.

According to a ninth aspect of the present invention, there is provided a fail-safe device in the follow-up traveling system, wherein the alarm means gives an alarm by stimulating a driver's sense by vibration, smell, or cold air. .

According to a tenth aspect of the present invention, in the fail-safe device according to the following traveling system, the alarm means includes:
A stimulus to one or two or more of the sense of hearing and the sense of touch is added to the driver to give an alarm.

In a preferred embodiment, the first set value is 1%.
0 km / h to 20 km / h, and the second set value is 20 km / h to 30 km / h.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram illustrating a main configuration of a follow-up traveling system to which the fail-safe device according to the present embodiment is applied. As shown in FIG. 1, the system of the present embodiment includes a vehicle speed sensor 1 (vehicle speed detecting means), an inter-vehicle distance sensor 2 (inter-vehicle distance detecting means), a shift lever position detecting device 3 (shift lever position detecting means), accelerator/
Brake actuator 4, shift lever actuator 5, alarm device 6 (alarm unit), ACC switch 7, control circuit 10 (vehicle speed control unit, shift lever control unit, vehicle speed limit control unit, awakening degree determination unit, steering control) Means).

Here, the vehicle speed sensor 1 is, for example, a general vehicle that detects the output shaft rotation speed of an automatic transmission (not shown) of the vehicle (that is, the rotation speed of a rotation shaft connected to a propeller shaft of the vehicle). This is an existing sensor, and the control circuit 10 detects the vehicle speed from the detection output of this sensor. The inter-vehicle distance sensor 2 includes, for example, a radio wave radar or a laser radar,
A sensor device for measuring a distance between a preceding vehicle and the own vehicle,
It is a well-known and existing component in a follow-up traveling system.

The shift lever position detecting device 3 is an existing switch in a general automatic transmission called, for example, an inhibitor switch, and is a shift lever (also referred to as a select lever) for selecting a traveling mode of the automatic transmission. Element for detecting the selection position.

The accelerator / brake actuator 4 is
An actuator for forcibly operating an accelerator or a brake under the control of the control circuit 10 even if an accelerator pedal or a brake pedal is not operated in order to perform following travel. It is. The shift lever actuator 5
An actuator that forcibly operates the shift lever under the control of the control circuit 10 even if the shift lever is not operated in order to realize the fail-safe function of the present invention.

The warning device 6 gives a warning to the driver by, for example, voice, warning sound, character display, and image display, and specifically includes a speaker, LED, or liquid crystal display. The warning device 6 may be a device that gives a warning by applying a stimulus to the driver's sense by vibration, smell, or cold air, or one of visual, auditory, and tactile sensations. Alternatively, a warning may be given by adding a stimulus to two or more senses to the driver.

The ACC switch 7 is an operation switch for instructing the control circuit 7 to shift to an ACC mode (follow-up running mode) in which follow-up control is performed by a driver's operation.
When the ACC switch 7 is on, the control circuit 7 determines that the ACC mode is commanded.

In this case, the control circuit 10 is an element constituting various control means and determination means of the present invention. Specifically, the control circuit 10 operates according to a preset program and includes a memory for storing various set values. Consisting of a microcomputer. The control circuit 10 is characterized in that, in this case, the following cruise control and the control as a fail-safe device are performed by the processing shown in the flowchart of FIG.

Next, the characteristic control processing of the control circuit 10 of this embodiment will be described with reference to the flowchart of FIG. In addition,
The series of processes in FIG. 2 are repeatedly executed at a constant cycle (for example, a cycle of 0.1 second) by, for example, activation of the control circuit 10.

First, in step S2, the ACC switch 7
Is determined, and if it is in the ON state, step S6
Otherwise, to step S4. Then, in step S4, the alarm state (the alarm device 6)
Is operating), the alarm state is released, the alarm device 6 is stopped, and a series of processing is terminated.

On the other hand, in step S6, the vehicle speed V0 at that time is determined from the output of the vehicle speed sensor 1. Then, in step S8, the set vehicle speed V1 one cycle later (for example, 0.1 seconds later) is calculated.

In this step S8, the following distance sensor 2
The set vehicle speed V1 is determined as a preferable target vehicle speed for maintaining the vehicle-to-vehicle distance at a predetermined constant value based on the distance to the preceding vehicle (vehicle distance) detected at the time from the output of the vehicle and the current vehicle speed V0. Desired. When the preceding vehicle is not detected, for example, the traveling speed when there is no preceding vehicle set by the driver or the like is equal to the set vehicle speed V.
Set as 1.

Next, at step S10, the current vehicle speed V0
Is equal to or less than a preset set value (for example, 20 km / h) and whether the set vehicle speed V1 obtained in step S8 is larger than the set value is determined. If this condition is satisfied, step S
Proceed to step S12, otherwise proceed to step S14.

Note that the set value (for example, 20 km / h) in step S10 corresponds to the second set value of the present invention. In step S10, it is determined whether or not the vehicle speed is to be increased to a high speed range exceeding the second set value. It is determined whether or not there is a transitional situation in which the situation is resolved and accelerated.

In step S14, if an alarm condition is present at that time, the alarm condition is released, the alarm device 6 is stopped, and the flow advances to step S22.

On the other hand, in step S12, the detection output of the shift lever position detecting device 3 is read, and it is determined whether or not the running mode selected at that time is the drive range (D range). Proceed to S16, otherwise proceed to Step S18.

In step S16, if an alarm condition is present at that time, the alarm condition is released, the alarm device 6 is stopped, and the flow advances to step S22.

On the other hand, in step S18, the alarm device 6 is operated to set an alarm state. Note that the content of the warning here is to notify the driver that the shift lever should be operated to the D range, and to notify the driver that the driver's awakening degree is decreasing, to call attention. And measures to increase the driver's arousal level.

The warning in step S18 is made when the process first proceeds to step S18.
The contents may be different depending on the case where a predetermined time has elapsed since the execution of step S18 every time thereafter.

For example, at first, the driver is simply informed of the switch to the D range by display or sound, and if this step S18 is still executed after a certain period of time, the driving is stopped. It is more likely that the driver's arousal level has dropped, so a relatively loud warning sound is issued, and after a certain period of time, vibrations are applied to the driver's seat, etc. May be taken.

Next, in step S20, the set vehicle speed V1 is forcibly set to the second set value (for example, 20 km / h) regardless of the set value in step S8. As a result, the vehicle speed during the follow-up running is limited to the second set value or less.

Next, in step S22, the accelerator / brake actuator 4 is controlled based on the latest set vehicle speed V1 obtained in step S8 or changed in step S20 and the vehicle speed V0 at that time. Control is performed so that the actual vehicle speed is substantially equal to the set vehicle speed V1. As a result, automatic following of the preceding vehicle or automatic running at the set speed when there is no preceding vehicle is realized.

Next, in step S24, it is determined whether or not the latest set vehicle speed V1 is smaller than a set value (for example, 10 km / h). If it is smaller than the set value, the process proceeds to the next step S26.
A series of processing ends. Note that the set value (for example, 10 km / h) here corresponds to the first set value of the present invention. The determination in step S24 is that the vehicle speed is the first speed.
It is determined whether or not the speed falls within a low speed range that is equal to or less than the set value.

In step S26, the selected position of the shift lever is forcibly switched to the first speed range (or the second speed range) by controlling the shift lever actuator 5, and a series of processing ends.

According to the above processing, when the vehicle speed is in the low speed range that is equal to or less than the first set value (10 km / h),
The shift lever is forcibly driven by the processing of steps S24 and S26, and the travel range is automatically and forcibly set to 1
The speed range is switched to the second speed range or the second speed range.

Steps S10, S12, S18, S
According to the processing of No. 20, the vehicle speed (in this case, the set vehicle speed V1) adjusted for the follow-up traveling should be increased beyond the second set value (20 km / h) which is equal to or more than the first set value. However, if it is not detected that the shift lever is at the position of the drive range, an alarm state occurs, the above-described warning is issued by the alarm device 6, and the vehicle speed adjusted for the following running is reduced. , The second set value (20 km / h).

That is, in this case, steps S10 and S12
By the processing of step S18, it is substantially determined that the driver's awakening level is reduced particularly due to the following running in the low speed range.
At 20, the safety measures in the case of a low alertness are taken. For this reason, an excellent effect of being able to reduce the danger due to a decrease in the arousal level of the driver can be obtained, particularly when the following running is performed in the low speed range.

That is, in the case of the apparatus of this embodiment, if the vehicle follows a low speed range due to traffic congestion, for example, the vehicle speed falls below the first set value. By the processing in S24 and S26, the selected position of the shift lever is reliably set to the first speed or the second speed.

Thereafter, for example, when the congestion is resolved and the vehicle should be accelerated following the preceding vehicle, the vehicle speed to be adjusted exceeds the second set value, and the determination result in step S10 becomes positive. Therefore, the determination process of step S12 is performed. In this case, if the driver grasps this situation and operates the shift lever to the D range, the result of the determination in step S12 becomes affirmative. Even if it is in the state, step S16 is executed at the time when the D range is operated, and the alarm state is immediately released.

However, for example, when the driver's awakening degree is reduced due to the following traveling in the low-speed range (or the preceding traveling in the high-speed range).
Since the driver cannot operate such a shift lever, the result of the determination in step S12 is negative, and steps S18 and S20 are executed (the awakening degree is determined to be low, and a corresponding measure is taken).

That is, according to the present apparatus, the switching between the general ACC (following traveling state in a high speed range) and the following traveling state in a low speed range such as following a traffic jam is performed as shown in FIG. 1 (b). When the awakening degree of the driver is decreasing, the driver does not shift from the following traveling state in the low-speed range to the following traveling state in the high-speed range. The drop is reliably determined and a warning is given to the driver. Therefore, particularly when the vehicle is traveling in a low-speed range, the danger caused by the driver's arousal level can be reliably reduced. This has the effect of greatly contributing to improved performance.

Further, as described above, the present apparatus is mainly constituted by elements existing in a general vehicle and elements already generally used as components of a follow-up traveling system. Compared to the case where a wakefulness detection device is provided, there is an advantage in practical use that the cost can be significantly reduced and the required space in the vehicle is extremely small.

The present invention is not limited to the above-described embodiment, but may have various aspects. For example, specific numerical values of the first set value and the second set value of the present invention may be appropriately set according to a required degree of safety or the like. However, considering the generally required safety level (safety speed) and the traveling speed in the case of following a traffic jam, the first set value is about 10 to 20 km / h and the second set value is about 20 km / h. It is preferably about 30 km / h.

Also, for example, step S18 in FIG.
Or the like, the warning may not be issued by the alarm device, and only the speed limitation (for example, the processing in step S20 in FIG. 2) may be performed. Conversely, there may be a mode in which only the alarm is performed without performing the speed limitation. However, it is needless to say that the combination of the two can further ensure the safety against the reduction in the arousal level.

Further, as shown by a dotted line in FIG. 1, for example, a steering actuator 8 controlled by a control circuit 10 (steering control means) may be provided to automatically control the steering device of the vehicle in the following running state. Good. In this case, since the steering wheel operation is unnecessary in addition to the operation of the brake and the accelerator, the driver's awakening degree is particularly likely to decrease, and the effect of the fail-safe device becomes more remarkable.

It is preferable that the automatic control of the steering device is performed only when the vehicle speed is in the low speed range below the first set value. This is because during low-speed follow-up driving, the vehicle speed is low and the range to be careful is narrow, and there is enough processing time, so it is relatively easy to automatically control steering using image processing technology etc. However, since it is necessary to pay attention to a wide range in a short time during high-speed running, it is relatively difficult to automatically control the steering using high-load processing such as image processing technology.

[0055]

According to the first aspect of the present invention, when the vehicle speed falls within a low-speed range that is equal to or lower than a first set value (for example, 10 km / h).
The shift lever is forcibly driven by the operation of the shift lever actuator under the control of the shift lever control means, and the traveling range is automatically and forcibly switched to the first speed range or the second speed range.

If it is not detected that the shift lever is in the drive range position, the vehicle speed adjusted for following the vehicle is controlled by the vehicle speed limit control means to be equal to or greater than the first set value. Set value (for example, 20 km
/ H).

[0057] Therefore, an excellent effect is obtained that the danger caused by a decrease in the driver's arousal level can be reduced, particularly when the vehicle is to be followed in a low speed range. That is, according to the present apparatus, for example, when the vehicle is running following in a low speed range due to traffic congestion or the like, the vehicle speed falls below the first set value. The forcible switching of the shift lever by the control ensures that the selected position is the first speed or the second speed.

Thereafter, for example, when the congestion is resolved and the vehicle should be accelerated following the preceding vehicle, the vehicle speed to be adjusted exceeds the second set value. If the shift lever is operated in the D range, the vehicle speed is not limited and the vehicle follows the preceding vehicle and accelerates. However, if the driver neglected to operate the shift lever in the D range, the vehicle speed limiting control means The control restricts the vehicle speed from increasing beyond the second set value.

That is, for example, when the driver's awakening degree is reduced due to the following traveling in the low speed range (or the preceding traveling in the high speed range).
Since the driver cannot operate the shift lever according to such a situation, the vehicle speed limiting control means operates to limit the vehicle speed to the second set value or less.

Therefore, when the awakening degree of the driver is low, the vehicle does not shift from the following traveling state in the low speed range to the following traveling state in the high speed range. In addition, the danger due to the driver's awakening level can be reduced reliably, and there is an effect that it can greatly contribute to improving the safety of the following traveling system that also performs following traveling in a low speed range such as following a traffic jam.

Further, the present device can be mainly constituted by existing components of a general vehicle and components already generally used as components of a following-traveling system. Compared to the case of providing, there is a practically excellent advantage that it can be realized at much lower cost and the required space in the vehicle is extremely small.

Further, in the fail-safe device according to the second aspect of the present invention, when the vehicle speed falls within a low speed range equal to or less than the first set value (for example, 10 km / h), the control by the shift lever control means is performed. The shift lever is forcibly driven by the operation of the shift lever actuator, and the traveling range is automatically and forcibly switched to the first speed range or the second speed range.

Then, the vehicle speed adjusted for the following running is set to a second set value (20 km / h) which is equal to or higher than the first set value.
If the shift lever is not detected to be in the drive range position despite the situation where it should be increased beyond the threshold, it is determined that the awakening degree of the driver has decreased by the awakening degree determination unit, The alarm means gives the driver an alarm, for example, as set forth in claims 5 to 10.

Therefore, an excellent effect is obtained that the danger caused by a decrease in the driver's arousal level can be reduced, particularly when the vehicle is to be followed in a low speed range. That is, according to the present apparatus, for example, when the vehicle is running following in a low speed range due to traffic congestion or the like, the vehicle speed falls below the first set value. The forcible switching of the shift lever by the control ensures that the selected position is the first speed or the second speed.

Thereafter, for example, when the congestion is resolved and the vehicle should be accelerated following the preceding vehicle, the vehicle speed to be adjusted exceeds the second set value. If the shift lever is operated in the D range, it is not determined that the arousal level is lowered. However, if the driver does not operate the shift lever in the D range, the arousal level of the driver is reduced by the arousal level determination unit. Is determined, and the warning is issued by the warning means.

That is, for example, when the driver's awakening degree is reduced by the following traveling in the low-speed range (or the preceding traveling in the high-speed range).
Since the driver cannot operate the shift lever according to such a situation, an alarm is activated and an alarm is issued.

Therefore, when the awakening degree of the driver is decreasing, the decrease in the awakening degree is reliably determined at the time of transition from the following traveling state in the low speed range to the following traveling state in the high speed range. A warning is given to the driver, and particularly when the vehicle is traveling in a low-speed range, the danger caused by a decrease in the driver's arousal level can be reliably reduced. This has the effect of greatly contributing to the improvement of the safety of the following cruising system.

Also, the present device can be mainly constituted by the existing components of a general vehicle and the components already generally used as components of the follow-up traveling system. Compared to the case of providing, there is a practically excellent advantage that it can be realized at much lower cost and the required space in the vehicle is extremely small.

When the vehicle further comprises a steering control means for automatically controlling the steering device of the vehicle in the following running mode,
The steering device of the vehicle is automatically controlled, so that the steering wheel of the driver becomes unnecessary, and the burden on the driver can be further reduced.
In this case, the driver's arousal level is more likely to be reduced, and the effect of the fail-safe device of the present invention on the reduction in the arousal level is more remarkable.

Further, when the steering control means is made to function only when the vehicle speed is in a low speed range equal to or lower than the first set value, the automatic control of the steering device is performed. The load on image processing and the like can be reduced, and the practicality is further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a following traveling system that is an example of the present invention.

FIG. 2 is a flowchart showing processing contents of a fail-safe device of the system.

[Explanation of symbols]

Reference Signs List 1 vehicle speed sensor (vehicle speed detecting means) 2 inter-vehicle distance sensor (inter-vehicle distance detecting means) 3 shift lever position detecting device (shift lever position detecting means) 4 accelerator / brake actuator 5 shift lever actuator 6 alarm device (alarm means) 7 ACC switch 8 Steering actuator 10 Control circuit (vehicle speed control means, shift lever control means, vehicle speed limit control means, awakening degree determination means, steering control means)

Claims (10)

[Claims] 1. An inter-vehicle distance detecting means for detecting a distance to a preceding vehicle, and automatically controlling an accelerator and a brake of the vehicle such that the distance detected by the inter-vehicle distance detecting means in a following driving mode is kept substantially constant. A vehicle speed control means for adjusting a vehicle speed, a fail-safe device for monitoring a degree of awakening of a driver during a following operation in a vehicle following operation system, wherein a driving range of an automatic transmission of the vehicle is switched. A shift lever actuator that forcibly activates a shift lever to switch the travel range, and when the vehicle speed is in a low speed range that is equal to or less than a first set value,
Shift lever control means for controlling the shift lever actuator to operate the shift lever to forcibly switch to the first speed range or the second speed range; and unless the shift lever is detected to be in the drive range position. Vehicle speed limiting control means for limiting the vehicle speed adjusted by the vehicle speed control means so as not to exceed a second set value greater than or equal to the first set value. Fail-safe device in driving system. 2. An inter-vehicle distance detecting means for detecting a distance to a preceding vehicle, and automatically controlling an accelerator and a brake of the vehicle so as to keep the distance detected by the inter-vehicle distance detecting means substantially constant in a following driving mode. A vehicle speed control means for adjusting a vehicle speed, a fail-safe device for monitoring a degree of awakening of a driver during a following operation in a vehicle following operation system, wherein a driving range of an automatic transmission of the vehicle is switched. A shift lever actuator that forcibly activates a shift lever to switch the travel range, and when the vehicle speed is in a low speed range that is equal to or less than a first set value,
A shift lever control unit for controlling the shift lever actuator to operate the shift lever to forcibly switch to a first speed range or a second speed range; and controlling the vehicle speed adjusted by the vehicle speed control unit to the first speed. Despite the situation in which the shift lever is to be increased beyond the second set value that is equal to or larger than the set value, the degree of arousal of the driver is determined based on the fact that the shift lever is not detected to be in the drive range position. A wakefulness judgment means for judging a decrease, and an alarm means for giving an alarm to the driver when the wakefulness judgment means judges that the wakefulness of the driver has been decreased. Safe device. 3. The fail-safe device according to claim 1, wherein said follow-up traveling system further comprises a steering control means for automatically controlling a steering device of the vehicle in the follow-up traveling mode. 4. The vehicle according to claim 3, wherein the steering control means functions only when the vehicle speed is in a low speed range equal to or lower than the first set value and automatically controls a steering device of the vehicle. A fail-safe device in a follow-up traveling system. 5. The fail-safe device according to claim 2, wherein the warning means gives a warning to the driver by voice. 6. The fail-safe device according to claim 2, wherein the warning means gives a warning to the driver by a warning sound. 7. The fail-safe device according to claim 2, wherein the warning means gives a warning to the driver by character display. 8. The fail-safe device according to claim 2, wherein the warning means gives a warning to the driver by displaying an image. 9. The fail-safe device according to claim 2, wherein the warning means applies a stimulus to the driver's sensation by vibration, smell, or cold to give a warning. 10. The warning device according to claim 1, wherein the warning unit applies a stimulus to one or more of sight, hearing, and tactile sensation to the driver to give a warning. Item 3. A fail-safe device in the follow-up traveling system according to Item 2.