JP2017174058A - Method for estimating inappropriate cognitive load, method for inviting attention of driver, and warning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inviting the attention of a driver who is under an inappropriate cognitive load and estimating the driver's condition.SOLUTION: The steering angle of a moving car is detected, and a vibration component generated by delay of steering of a vehicle is taken out from a detection signal. If the vibration component taken out is higher than a predetermined threshold value, the cognitive load of the driver is estimated to be in an appropriate state and the driver's attention is invited based on the result of estimation to prevent an accident.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a method for estimating that a driving driver is in a state of inappropriate cognitive load, a method for alerting the driver to prevent an accident based on the estimation, and the method. It relates to a warning device.

  Most of the causes of driver accidents are human error, or human action that produces unintended consequences. For example, an incorrect driving operation or a reaction that is too slow. And they occur when the attention directed at driving is lower than the attention required for driving in the traffic situation at that time.

  Specifically, it is necessary to pay less attention to the surroundings, such as when driving on a vacant highway, or to appear to sleep because of fatigue (referred to as “micro sleep”, 0. It occurs in a short time of 5 to 1.5 seconds.) Furthermore, there is a state where the driver is paying attention to something other than driving. As a state where the driver is paying attention to something other than driving, there is a case where a mobile phone is put on or a person is indulging in fantasies.

  The situation where the attention directed to driving as described above is lower than the attention required for driving is due to the fact that the driver is in a cognitively improper state, that is, in an “inappropriate cognitive load” state. is there.

  Signs of inappropriate cognitive burden manifest as driver response delays. Therefore, the cognitive load is in an inappropriate state by measuring the amount of delay in the driver's movement (for example, the amount of delay in the steering wheel operation or the depression of the brake pedal) with respect to the stimulus from the driving environment. Can be estimated.

  However, a significant delay in steering operation or a delay in depressing the brake pedal can directly cause an accident. Therefore, it cannot be said that the direct measurement of the amount of delay in the operation of the driver prevents the accident.

  Further, in order to prevent a drowsy driving, a method for detecting a driver's reaction delay has been proposed in the same manner as the above-described method. For example, in Patent Document 1, when the driver's attention is reduced, the steering operation is always delayed with respect to the change in the traveling direction of the vehicle. Therefore, by detecting the steering operation delay, the driver's attention is reduced. Is judged.

  Specifically, the course information output from the traveling direction sensor is compared with the steering angle information output from the steering sensor of the steering wheel. It is judged that the patient is dozing and a warning is given.

Japanese Patent Laid-Open No. 11-263143

  It is conceivable that the method described in Patent Document 1 is used to estimate that the driver's cognitive load is in an inappropriate state and to alert the driver. However, since the method described in Patent Document 1 needs to compare the course information and the steering angle information for a certain period, it is assumed that the dozing state continues for a certain period. That is, even if an inappropriate cognitive load can be estimated by this method, an accident may have already occurred.

  The present invention has been made in view of the above-described situation, and estimates the initial signs and the results based on the estimation results before the driver is in an inappropriate cognitive load state and needs emergency response. The purpose is to provide a method to alert the driver and prevent accidents.

In order to achieve the above object, a method for estimating an inappropriate cognitive load according to the present invention includes a step of detecting a steering angle of a vehicle driven by a driver, and
Extracting a driver-induced vibration component from the detection signal;
Estimating the driver's cognitive load in an inappropriate state when the value of the extracted vibration component exceeds a predetermined threshold value.

  Here, instead of the steering angle, the lateral acceleration of the vehicle body may be detected.

The method for alerting a driver according to the present invention includes a step of detecting a steering angle of a vehicle driven by the driver,
Extracting a driver-induced vibration component from the detection signal;
And a step of calling a driver's attention using at least one of sound and light when the value of the extracted vibration component exceeds a predetermined threshold value.

  Here, instead of the steering angle, the lateral acceleration of the vehicle body may be detected.

  In addition, it is preferable to extract the driver-induced vibration component at the entrance or exit of a corner of the lane in which the vehicle travels.

  Moreover, it is preferable that the vibration component is extracted from the detection signal using a filter whose frequency characteristics change according to the type and speed of the vehicle. Furthermore, it is preferable that the threshold value changes according to the type and speed of the vehicle.

A warning device according to the present invention includes a steering angle sensor that detects a steering angle of a vehicle driven by a driver,
An informing means for alerting the driver using at least one of voice and light;
Calculating means for extracting a vibration component of a predetermined frequency from the detection signal of the steering angle sensor, and comparing the value of the extracted vibration component with a threshold value stored in advance in a memory;
Control means for controlling the operation of the notification means according to the output of the calculation means,
The control means operates the notifying means when a value of a vibration component is equal to or greater than a threshold value in the calculating means.

  Here, instead of the steering angle sensor, an acceleration sensor that detects lateral acceleration of the vehicle body may be used.

  Preferably, a non-volatile memory is used as the memory, and the threshold value varies according to the type and speed of the vehicle.

  By adopting the method according to the present invention, when the cognitive load increases and the delay in the steering operation is increasing, the driver can be informed at an early stage to prevent an accident.

  Furthermore, according to the method of the present invention, since the occurrence of driver-induced vibration due to a delay in steering operation can be detected in a short time (within 2 seconds), it can sufficiently cope with emergency evacuation measures such as collision avoidance. .

It is a figure which shows the external appearance and specification of the vehicle (racing car) used for the simulation in embodiment of this invention. It is a figure which shows the driving | running | working locus | trajectory of the vehicle in the simulation. FIG. 3 is a graph showing a steering angle, a deviation, and a lateral acceleration of a vehicle traveling on the locus of case 1 in FIG. 2. It is a figure which shows the shape of the lane in which a vehicle drive | works in simulation. It is a graph (straight drive) which shows the relationship between the steering operation delay in the simulation, the steering angle, and the lateral acceleration of the vehicle body. It is a graph (running | running | working of the entrance of a corner) which shows the relationship between the delay of steering operation in a simulation, a steering angle, and the acceleration of the horizontal direction of a vehicle body. It is a graph (running | running | working of the exit of a corner) which shows the relationship between the delay of steering operation in a simulation, a steering angle, and the acceleration of the horizontal direction of a vehicle body. It is a block diagram which shows the structure of the warning device concerning embodiment of this invention. It is a perspective view which shows schematic structure of the vehicle to which the steering angle sensor was attached. It is a block diagram which shows the other structure of a warning device. It is a perspective view which shows schematic structure of the vehicle to which the acceleration sensor was attached.

  Hereinafter, a method for estimating an inappropriate cognitive load, a driver alerting method, and a warning device according to embodiments of the present invention will be described with reference to the drawings.

<Inappropriate cognitive load estimation method>
As previously mentioned, when the driver's cognitive load increases and is in an inappropriate state, the indication appears as a delay in the driver's response. Specifically, this becomes apparent as a delay in steering operation.

  However, it is dangerous to actually perform experiments using human drivers, and it is difficult to accurately measure human reaction delay before that.

  Therefore, the inventors performed a simulation using a racing car simulator to determine how the vehicle travels when there is a delay in steering operation as the cognitive load increases.

 In the present embodiment, TORCS (The Open Racing Car Simulator) which is an open source is used as a simulator. Then, a driving agent (Driving Agent) capable of the same driving operation as a human driver is set, and the driving state based on the steering angle function (hereinafter referred to as “SAF”) of the steering wheel shown below is set. A simulation was performed.

ここで、θは横方向の加速度、ｄはセンターラインからの偏移、ｄ'はその微分、αは車線のセンターラインと車の進行方向の軸とのなす角度である。

Here, θ is the acceleration in the lateral direction, d is the deviation from the center line, d ′ is the derivative thereof, and α is the angle formed by the center line of the lane and the axis in the traveling direction of the vehicle.

 Although the detailed description of the above-described function SAF is omitted, the optimized SAF behaves like proportional differential (PD) control.

 FIG. 1A shows the appearance of a car (racing car) set in the simulator (TORCS) used in this embodiment, and FIG. 1B shows its main specifications. By using TORCS and calculating the steering angle via the steering wheel operation using the above-described function SAF, the same driving state as when actually driving on the road using the car of the specification shown in FIG. realizable.

  Next, traveling of a vehicle driven by a virtual driving agent using the above-described function SAF will be described. FIG. 2 shows the trajectory of the vehicle when the vehicle 1 traveling on the right end of the lane moves to the center line. In FIG. 1, a pair of front wheels 11 and a pair of rear wheels 12 are attached to the lower part of a vehicle body 10, and a driving agent changes the steering angle of the front wheels 11 by operating a handle (not shown). Change.

 In FIG. 2, the driving | running | working locus | trajectory of the center part of a vehicle is shown about three cases implement | achieved using a simulator. In FIG. 2, initially, the car is placed 8 m to the right from the center line of a wide and straight lane in parallel with the center line, and slowly accelerates from this state to 50 km / h. The speed is maintained by depressing and releasing the accelerator pedal using simple feedback control software.

 When the vehicle speed reaches 50 km / h, the steering angle of the front wheel 11 of the vehicle is calculated by the function SAF (at a sampling interval of 20 ms) so that the actual driver operates, and the steering operation is performed.

 In FIG. 2, the locus of case 1 (indicated by a solid line) indicates a case where the vehicle returns quickly and smoothly to the center line of the lane by an accurate operation.

As a reference, FIG. 3 shows the vehicle steering angle, deviation from the center line, and lateral acceleration when the trajectory described in case 1 of FIG. Indicates. The graph of FIG. 3 shows that the lateral acceleration is 10 m / s ² or less and the movement is smooth.

 On the other hand, the locus of case 2 in FIG. 2 (indicated by a broken line) indicates a case where the handle operation is too early. If the return is too early, the movement is unnatural and vibrations occur when returning to the centerline. In addition, such a return trajectory is uncomfortable for the driver and passengers due to the lateral acceleration, and has a problem with safety.

 The trajectory of case 3 in FIG. 2 (indicated by a one-point difference line) indicates a case where the steering operation is too slow, and it takes time for the trajectory to overlap the center line as compared to case 1. In actual driving, if the driver's cognitive load is inappropriate, the steering operation may be delayed, and the corner may be off the center line at the entrance or exit of the corner.

<Simulation results>
Next, simulation results when a delay occurs in the steering operation will be described. Similarly to the above, three test cases will be described when the driving agent travels in the vicinity of the center line of the lane at a constant speed of 50 km / h and the delay times are 0, 100 ms, 200 ms, and 400 ms, respectively. These delay times correspond to reaction delays that would be caused by inappropriate cognitive load if the driver is human.

  As shown in FIG. 4, the steering wheel is operated when the vehicle runs on the straight part of the lane in the test case 1, runs at the corner entrance in the test case 2, and runs at the corner exit in the test case 3. A simulation was performed assuming that a delay occurred.

 In all these test cases, the steering delay is only added for 2 seconds. At that time, the vehicle is set to a normal driving state in which an emergency response such as stepping on a brake or operating a steering wheel is not required.

  As described above, the delay in the steering operation is caused by an inappropriate cognitive load on the driver. The reason for setting the delay time to 2 seconds in the simulation is to assume the most dangerous period of the cognitive load, that is, the period in which the above-described microsleep can occur. A typical microsleep period is 0.5 seconds to 1.5 seconds.

  In the simulation, two types of steering noise are introduced into the source code of the TORCS in order to fill a gap generated between the actual driving by the vehicle and the simulation.

 One is random noise having a frequency of about 50 Hz. This noise is caused by vibrations of the rotating wheels due to irregularities such as micro bumps existing on the surface of the road and differences in the rotation radii of the four wheels of the car.

 On the other hand, in the straight part of the lane, it is caused by fluctuations in the steering angle due to play and hysteresis existing in joint parts (steering shaft, gearbox, tie rod, joint arm, kingpin, etc.) that connect the members of the steering mechanism of the car. . This other noise is a low frequency noise of about 1 Hz.

  A simulation result when the delay time in the steering wheel operation is set to 0, 100 ms, 200 ms, and 400 ms using the above-described simulator will be described. In FIG. 4, in the test case 1, the running state of the vehicle was simulated when the steering operation was delayed for 2 seconds while the vehicle traveling straight passed through the area surrounded by the broken line. FIG. 5 shows the result.

 In FIG. 5A, the horizontal axis represents the travel distance, and the vertical axis represents the steering angle. In the graph of FIG. 5 (a), the part surrounded by a broken line shows the change in the steering angle when a delay is applied to the steering wheel operation (2 seconds). As shown in the upper right frame of the graph, The line type is changed. FIG. 5B is a graph in which a horizontal axis is enlarged by cutting out a portion surrounded by a broken line in the graph of FIG. 5A (that is, a portion where the steering operation is delayed).

 On the other hand, in FIG. 5C, the horizontal axis indicates the travel distance, and the vertical axis indicates the acceleration in the lateral direction of the vehicle body (the direction orthogonal to the traveling direction of the vehicle). In the graph of FIG. 5 (c), the portion surrounded by a broken line shows the change in acceleration when the steering wheel operation is delayed (2 seconds) as in FIG. 5 (a), and the type of the line depends on the delay time. It is changing. FIG. 5D is a graph in which the horizontal axis is enlarged by cutting out a portion surrounded by a broken line in the graph of FIG. 5C (that is, a portion where the steering operation is delayed).

 5A and 5C, regardless of the presence or absence of a delay, a noise component having a high frequency (about 50 Hz) is included in both the steering angle and the acceleration. As described above, this noise component is It is caused by road irregularities and wheel diameter fluctuations.

 Further, as shown by the solid lines in the graphs of FIGS. 5B and 5D, when the delay time of the steering operation is increased (400 ms), vibration components having a low frequency of about 0.5 Hz are included, but the strength is high. It is not different from the noise component of the frequency. That is, in the straight-ahead portion, even if a delay occurs in the steering wheel operation, it means that there is no vibration that can be distinguished from other noise components.

 Returning to FIG. 4, the test case 2 will be described. In test case 2, the running state of the vehicle was simulated when a delay was applied to the steering wheel operation for 2 seconds after the vehicle entered the curved part of the lane. The result is shown in FIG.

 The contents of the graphs in FIGS. 6A to 6D are the same as the contents described in FIGS. 5A to 5D. Unlike FIGS. 5A and 5B, FIGS. 6A and 6C show the steering angle and acceleration from entering the corner to the exit of the lane, and the shape of the graph changes accordingly. .

 Specifically, until entering the corner and after leaving the corner, there is no difference from the graphs of FIGS. 5A and 5C, but when entering the corner, both the steering angle and the lateral acceleration are negative values. Is shown.

 As shown in FIGS. 6 (b) and 6 (d), which are enlarged views within the dotted lines in FIGS. 6 (a) and 6 (c), as the delay time increases, the low frequency ( The value of the vibration component of about 0.5 Hz) is large, and the waveform is clearly different from the noise component caused by the road surface condition and the tire diameter difference. This means that if the driver's handle operation is delayed more than a certain amount at the entrance of the corner (400 ms delay in the figure), the handle vibrates in the rotational direction and the vehicle body vibrates laterally. Yes. That is, driver-induced vibration occurs.

 Returning to FIG. 4, the test case 3 will be described. In test case 3, the running state of the vehicle was simulated when the steering wheel operation was delayed for 2 seconds after the vehicle exited from the curved part of the lane. FIG. 7 shows the result.

 The contents of the graphs in FIGS. 7A to 7D are the same as the contents described in FIGS. 5A to 5D. Similarly to FIG. 6, FIGS. 7A and 7C show the steering angle and the acceleration in the lateral direction from entering the corner to exiting, and the shape of the graph changes accordingly. .

 As shown in FIGS. 7 (b) and 7 (d), which are enlarged within the dotted lines in FIGS. 7 (a) and 7 (c), as the delay time increases in each of the steering angle of the steering wheel and the lateral acceleration of the vehicle body, The value of the low frequency (about 0.5 Hz) driver-induced vibration component is large. This means that the steering wheel vibrates in the direction of rotation when the driver's steering wheel operation is delayed more than a certain amount (400 ms delay in the figure) at the corner exit as well as the corner entrance. It means to vibrate.

 Even in a general feedback control system such as a PD control system, it is known that the Nyquist condition breaks down when a delay occurs, and the system vibrates. However, the same applies to a control system having a function SAF that is similar to a human vehicle operation. May occur.

 As is apparent from the simulation results in the three test cases described above, when the driver's cognitive load is in an inappropriate state, when a delay of a predetermined value or more occurs in the steering operation, vibration occurs in the steering angle. Furthermore, lateral vibrations occur in the vehicle body. Therefore, by detecting the driver-induced vibration, it can be estimated that the driver is in an inappropriate cognitive load.

 Furthermore, since the vibration intensity is thought to be proportional to the magnitude of the cognitive load, when the vibration intensity exceeds a certain value, the driver's attention is given by using voice or light. The occurrence of accidents can be prevented in advance.

 Specifically, in the present embodiment, when the steering angle or the lateral acceleration of the vehicle body is detected, a vibration component having a predetermined frequency is extracted from the detection signal, and the value exceeds a certain value (threshold value). Judging by the driver-induced vibration, the driver is alerted by assuming that the driver is in an inappropriate cognitive load.

 Note that the strength of the vibration component used as a reference varies depending on the vehicle specifications (size and weight) and travel speed. Therefore, the vibration component threshold value is set in advance according to the vehicle type and speed, and the data is stored in the memory. Must be stored.

<Configuration and operation of warning device>
Next, with reference to FIG. 8 and FIG. 9, a warning device that realizes the above-described driver alert method will be described. FIG. 8 is a block diagram showing the configuration of the warning device, and FIG. 9 is a schematic perspective view for explaining the mounting position of the steering angle sensor of the device.

  The warning device 3 includes an interface 31, a CPU 32, a ROM 33, a RAM 34, a flash memory 35, and a notification unit 36. The warning device 3 extracts a vibration component from the output signal of the steering angle sensor 21 that detects the steering angle of the vehicle 1, When the strength exceeds a certain value, it is estimated that the cognitive load of the driver is in an inappropriate state, and alerts the driver using the notification means 36.

 As shown in FIG. 9, the steering angle sensor 21 is attached in the vicinity of the steering mechanism 16 that transmits the rotation of the handle 13 to the front wheels 11 via the steering shaft 14, and detects the steering angle of the front wheels 11.

 The interface 31 receives a signal from the steering angle sensor 21, converts the signal into a digital signal using a built-in A / D converter, and transfers the signal to the CPU 32.

  The CPU 32 reads out the software stored in the ROM 33 and performs calculation, and controls the operation of the notification unit 36 based on the result, thereby realizing the functions of the calculation unit 321 and the control unit 322. Note that the RAM 34 functions as a working memory, and the flash memory 35 stores threshold data for calculation.

 The notification means 36 uses a sound and light to alert the driver, and is composed of a speaker and an LED. When it is estimated that the driver is in an inappropriate cognitive load based on the calculation result of the calculation means 321, a warning sound is emitted from the speaker, and the LED is blinked to notify the driver.

  Next, the operation of the warning device 3 will be described. The calculation means 321 implements the functions of a filter and a comparator, extracts the vibration component from the steering angle detection signal, compares the value with the threshold value read from the flash memory 35, and if the vibration component exceeds the threshold value Then, the control means 322 is notified to operate the notifying means 36 to alert the driver.

 As described above, since the frequency and strength of the vibration component included in the steering angle detection signal differ depending on the vehicle specification and speed, the flash memory 35 stores threshold data corresponding to the vehicle type and speed. Has been.

 The threshold data stored in the flash memory 35 is calculated using a simulator. Although it is possible to measure threshold data by driving an actual car, it is difficult to realize a state of cognitive load inappropriate in actual driving, and such a state is dangerous. It is preferable to calculate using a simulator.

  In the warning device shown in FIG. 8, it is estimated whether or not the driver is in an inappropriate cognitive load based on the output signal of the steering angle sensor 21, but as shown in FIG. Based on the output signal of the sensor 22, it may be estimated whether the driver is in an inappropriate cognitive load.

 In this case, the acceleration sensor 22 is attached to the vehicle body 10 as shown in FIG. In FIG. 11, the acceleration sensor 22 is attached to the dashboard. However, the attachment position of the acceleration sensor 22 may be anywhere as long as vibrations in the lateral direction of the vehicle body 10 can be detected.

 When estimating the state of the cognitive load based on the output of the acceleration sensor 22, the threshold data stored in the flash memory 35 needs to be a value corresponding to the output of the acceleration sensor 22.

 In the present embodiment, the notification means 36 alerts the driver with sound and light. However, the driver's attention may be alerted using only one of sound and light.

 As described above, according to the present invention, as a result of the simulation of the driving of the vehicle using the racing car simulator, if the delay in the steering operation becomes large, the driver-induced vibration occurs in the steering angle, and the vehicle It was made based on finding that it vibrates in the direction. The present invention makes use of this phenomenon to estimate the initial sign that the actual driver's cognitive load is in an inappropriate state based on the delay in steering, and informs the driver of the accident before it occurs. It is something to prevent.

 According to the method of the present invention, since the occurrence of driver-induced vibration due to a delay in steering operation can be detected in a short time (within 2 seconds), it can sufficiently cope with emergency evacuation measures such as collision avoidance.

 In the above simulation, an open source simulator (TORCS) was used to analyze the relationship between the cognitive load and the vibration in the rotational direction of the steering wheel or the lateral vibration of the vehicle body. However, the simulator is not limited to this. Is not to be done. Needless to say, the analysis may be performed using another commercially available simulator.

1 car (racing car)
3 Warning device 10 Car body 11 Front wheel 12 Rear wheel 21 Steering angle sensor 22 Acceleration sensor 31 Interface 32 CPU
33 ROM
34 RAM
35 Flash memory 36 Notification means 321 Calculation means 322 Control means

Claims (11)

Detecting a steering angle of a vehicle driven by a driver;
Extracting a driver-induced vibration component from the detection signal;
Estimating that the driver's cognitive load is in an inappropriate state when the value of the extracted vibration component exceeds a predetermined threshold value, comprising: Load estimation method.   The method for estimating an inappropriate cognitive load according to claim 1, wherein a lateral acceleration of a vehicle body is detected instead of the steering angle.   The method for estimating an inappropriate cognitive load according to claim 1 or 2, wherein the driver-induced vibration component is extracted at a corner entrance or exit from a lane in which the vehicle is traveling. Detecting a steering angle of a vehicle driven by a driver;
Extracting a driver-induced vibration component from the detection signal;
A method of alerting the driver, comprising: a step of alerting the driver using at least one of sound and light when the value of the extracted vibration component exceeds a predetermined threshold value.   The driver alert method according to claim 4, wherein a lateral acceleration of the vehicle body is detected instead of the steering angle.   6. The method for alerting a driver according to claim 4, wherein a driver-induced vibration component is taken out at a corner entrance or exit from a lane in which the vehicle is traveling.   The driver alert method according to any one of claims 4 to 6, wherein the driver-induced vibration component is extracted from the detection signal using a filter whose frequency characteristic changes according to a type and speed of a vehicle.   The method for alerting a driver according to any one of claims 4 to 7, wherein the threshold value changes according to a type and a speed of the vehicle. A steering angle sensor for detecting the steering angle of a vehicle driven by a driver;
An informing means for alerting the driver using at least one of voice and light;
Calculating means for extracting a vibration component of a predetermined frequency from the detection signal of the steering angle sensor, and comparing the value of the extracted vibration component with a threshold value stored in advance in a memory;
Control means for controlling the operation of the notification means according to the output of the calculation means,
The control unit operates the notification unit when the value of the vibration component in the calculation unit is equal to or greater than a threshold value.   The warning device according to claim 9, wherein an acceleration sensor that detects a lateral acceleration of the vehicle body is used instead of the steering angle sensor.   The warning device according to claim 9 or 10, wherein a non-volatile memory is used as the memory, and the threshold value varies according to the type and speed of the vehicle.

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