Abstract
The present disclosure relates to a method for determining the fatigue of a driver of a motor vehicle, wherein the fatigue is determined while taking into account the steering behavior of the driver, characterized in that the method includes the following steps: determination of a hysteresis of the steering system or the fatigue detection system, and taking into account the detected hysteresis in the determination of the fatigue of the driver. Furthermore, the disclosure relates to a device that is set up to execute the method.
Claims
1. A method for determining a fatigue of a driver of a motor vehicle, the method comprising: determining a hysteresis of at least one of (i) a steering system and (ii) a fatigue detection system, based on a direct relationship between a steering angle signal and a lateral acceleration signal indicating a turn rate of the vehicle; determining the fatigue of the driver based on a steering behavior of the driver and the determined hysteresis; and controlling a driver assistance system to take over control of the motor vehicle with an automated driving function based on the fatigue of the driver.
2. The method according to claim 1, the determining the hysteresis further comprising: determining the hysteresis based on at least one of (i) a steering mechanism, (ii) a steering angle sensor measuring system, (iii) a steering angle sensor preprocessing, (iv) a signal transmission, (v) a control unit input, and (iv) the determining of the fatigue of the driver.
3. The method according to claim 1, the determining the hysteresis further comprising: receiving the steering angle signal.
4. The method according to claim 3, the determining the hysteresis further comprising: analyzing the steering angle signal.
5. The method according to claim 4, the analyzing the steering angle signal further comprising: determining at least one position in the steering angle signal at which a hysteresis has occurred; and calculating the hysteresis at the at least one position.
6. The method according to claim 5, the calculating the hysteresis further comprising: applying two tangents to a curve of the steering angle signal; determining an intersection of the two tangents; and calculating the hysteresis as twice a distance between the intersection of the two tangents and a plateau of the curve of the steering angle signal.
7. The method according to claim 1 further comprising at least one of: adapting, based on the determined hysteresis, an application parameter that is used to determine the fatigue of the driver adapting, based on the determined hysteresis, a dead band event intensity that is used to determine the fatigue of the driver; and changing, based on the determined hysteresis, a hysteresis in a steering angle signal to a known value.
8. The method according to claim 1 further comprising: controlling the driver assistance system: to issue issuing a warning to the driver based on the fatigue of the driver.
9. A device for determining a fatigue of a driver of a motor vehicle, the device configured to: determine a hysteresis of at least one of (i) a steering system and (ii) a fatigue detection system, based on a direct relationship between a steering angle signal and a lateral acceleration signal indicating a turn rate of the vehicle; determine the fatigue of the driver based on a steering behavior of the driver and the hysteresis of the at least one of (i) the steering system and (ii) the fatigue detection system; and control a driver assistance system to take over control of the motor vehicle with an automated driving function based on the fatigue of the driver.
10. The device according to claim 9, wherein the device is configured to execute a computer program to determine the hysteresis and to determine the fatigue of the driver.
11. The device according to claim 9, wherein the computer program is stored on a machine-readable storage medium.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) It should be noted that the features individually listed in the description can be combined in any technically reasonable manner and reveal further embodiments of the disclosure. Further features and usefulness of the disclosure arise from the description of exemplary embodiments on the basis of the attached figures.
(2) In the figures:
(3) FIG. 1 shows a procedure of an application process of fatigue detection from the prior art; and
(4) FIG. 2 shows an action chain of the steering angle signal from the driver to the fatigue detection, and
(5) FIG. 3 shows a representation of the performance change in the case of hysteresis differences in the steering angle signal, and
(6) FIG. 4 shows possible measures against performance change in the case of fatigue detection, and
(7) FIG. 5 shows a presentation of an exemplary determination of hysteresis, and
(8) FIG. 6 shows exemplary steps of the method for the determination and consideration of hysteresis in the case of fatigue detection.
DETAILED DESCRIPTION
(9) FIG. 1 shows a procedure of an application process of fatigue detection from the prior art. Here, the application is carried out with a test vehicle that has a certain hysteresis (left half of the image). However, different hysteresis can occur in the field, which can change the warnings and thus the performance of the fatigue detection (right half of the image). A1 shows the test vehicle with an unknown hysteresis in the steering angle signal. In A2, the application is carried out. Based on this, in A23 parameters are defined and transferred to the fatigue detection process in A3. In A4, the warnings are optimized and adjusted. This is carried out up to A5 until sufficient performance, i.e. reliability, is present in the test vehicle. The stored values are taken into account as target values in A52 in the application. In the field, however, there are other vehicles with different hysteresis in the steering angle signal A6. However, these also use the fatigue detection process A3 with the stored parameters. This may cause time delays in the event of a warning A7. Furthermore, there may be a change in performance A8.
(10) FIG. 2 shows a chain of action of the steering angle signal from the driver to the fatigue detection. In this case, hysteresis errors can occur in each individual element. The main source of error, however, is mostly the measuring system of the steering angle sensor. For example, the chain of action starts with the driver, who caused a lane change due to a movement of the steering wheel. The first component w1 in the chain of action is the steering mechanism. The next component w2 is the steering angle sensor. This consists of the measuring system w21 as well as the preprocessing w22. Both components may also have a hysteresis error. This is followed by signal transmission w3, control unit input w4 and fatigue detection w5. Here, too, hysteresis can be present in each individual component or all components, which can lead to an error in the evaluation or at least a reduction in performance.
(11) FIG. 3 shows a representation of the performance change in the event of hysteresis differences in the steering angle signal. The performance change is shown on the basis of the relevant parameter specificity (correct-negative rate) and sensitivity (correct-positive-rage) in the case of hysteresis differences. The x-axis shows the hysteresis differences in degrees and the y-axis shows the ratio in percentages. The solid line (or dotted line) shows the specificity parameter and the dashed line (or dashed dotted line) shows the parameter sensitivity.
(12) FIG. 4 shows possible measures against a change in performance occurring in the case of hysteresis using the example of a fatigue detection. With the help of a hysteresis estimator, which calculates the hysteresis online in the vehicle, various measures can be taken that keep the performance constant. The vehicle 1 includes a steering system 2 and a fatigue detection system 3, and furthermore a driver assistance system 4. Also shown is a control unit 5, which may be assigned to the driver assistance system 4 and/or the fatigue detection system or the steering system 2. During the operation of the vehicle, the steering angle signal (with existing hysteresis) is evaluated. The determination of the hysteresis is carried out by the hysteresis estimator HS. Based on the hysteresis thus determined, several measures can be performed. In measure V1, the hysteresis in the steering angle signal is changed. If the steering angle signal is corrected with a changed hysteresis, the dead band event calculation does not change. In the measure V2, the application parameters are changed. If the application parameters are changed, a changed dead-band event calculation (DBE_B) can be counteracted. In the measure V3, the dead band event intensity is changed. When the dead band event intensity (DBE_I) is changed, individual dead band events have a different influence on the dead band index. A change in the dead band event calculation may be relativized thereby. The dead band index (DB_I) is calculated while taking into account the selected measure(s). Furthermore, the situation index (Si_I) is determined on the basis of the current situation (Si). The determination of the fatigue index (M_I) is then carried out taking into account the dead band index (DB_I) and the situation index (Si_I).
(13) FIG. 5 shows a representation of an exemplary approach to the determination of the hysteresis. Here, the steering angle signal curve is shown against time. For the calculation of the hysteresis, the past steering angle signal (solid line) is analyzed at positions where hysteresis occurred. Then, at these positions, the hysteresis (H.sub.1,H.sub.2,H.sub.3) is calculated using two tangents (dotted-dashed line). The course of the tangents in the area of the plateau corresponds to an approximation of the true steering angle of the driver.
(14) For the tangents, on the one hand the last point P.sub.2 before the plateau and in addition another point P.sub.1 are used for the tangent slope. This additional point P.sub.1 is at a distance of two time units to get an average value for the slope. Since the hysteresis occurs in the entire steering angle signal, the tangents are applied to each occurring plateau. The distance between the intersection of both tangents and the plateau is the error and corresponds to half the hysteresis of the total signal (since deviations occur with both positive and negative plateaus). The distances between the intersections and the plateau will be very identical with this calculation method, so that an average of all distances hits (half) the hysteresis of the signal very precisely. Examples are shown of three hysteresis H.sub.1,H.sub.2 and H.sub.3.
(15) In FIG. 6, a representation of the steps of the method of an embodiment of the disclosure is shown. In a first step S1, the procedure is started. Step S2 shows the determination of the hysteresis. To determine the hysteresis, the steering angle signal is first determined in S21. In S22, the positions in the steering angle signal at which hysteresis occurred are determined. In step S23 the calculation of the hysteresis is carried out. For this purpose, two tangents are applied to the plateaus of a respective hysteresis in a step S231. In step S232, the intersection of the tangents is calculated. In step S233, the respective hysteresis is determined on the basis of the distance of the tangent intersection point and the plateau. In step S3, a measure is performed to reduce the hysteresis error. In step S4, a fatigue determination is carried out while taking into account the optimization to reduce possible errors on the basis of detected hysteresis.
