EP2909827A1

EP2909827A1 - Method and assistance system for assisting a driver of a motor vehicle, and measuring method and measuring system for determining a mental state of a driver of a motor vehicle

Info

Publication number: EP2909827A1
Application number: EP13791942.9A
Authority: EP
Inventors: Stefanie ESSERS; Lisa DIWISCHEK
Original assignee: Takata AG
Current assignee: Takata AG
Priority date: 2012-10-22
Filing date: 2013-10-22
Publication date: 2015-08-26
Also published as: US20150258995A1; WO2014064095A1; JP2016500874A

Abstract

The invention relates to a method and an assistance system for assisting a driver of a motor vehicle, said method having the following steps: - measuring at least one value of at least one vital parameter of the driver, said vital parameter being correlated to the mental state of the driver, and/or at least one value of at least one driving dynamic variable correlated to the mental state of the driver; - classifying the mental state of the driver using the measured value of the vital parameter or the driving dynamic variable; and - generating a signal, which can be perceived by the driver, by means of a driver assistance system of the motor vehicle, said signal being selected from a plurality of different signals dependent on the classification of the mental state of the driver, or suppressing a signal of the driver assisting system and/or selecting at least one vehicle parameter dependent on the classification of the mental state of the driver. The invention also relates to a measuring method and a measuring system for determining a mental state of a driver of a motor vehicle.

Description

Method and support system for supporting a driver of a motor vehicle, and measuring method and measuring system for determining a mental state of a driver of a motor vehicle

description

The invention relates to a method for supporting a driver of a motor vehicle according to claim 1, a corresponding support system according to claim 9, a measuring method for determining a mental state of a driver of a motor vehicle according to claim 10 and a corresponding measuring system according to claim 17.

Assistance systems for motor vehicles known e.g. Control functions of the vehicle and / or warn a driver of the vehicle from critical driving situations. One danger associated with the presence of a variety of assistance systems in a vehicle is that the driver relies too much on the assistance systems and / or does not respond adequately to information provided by the assistance systems.

The problem to be solved by the invention is to improve the safety of a motor vehicle.

This problem is solved by the method with the features according to claim 1, the corresponding support system with the features of claim 9, the measuring method according to claim 10 and by the corresponding measuring system with the features of claim 17. Further developments of the invention are specified in the dependent claims. Thereafter, there is provided a method of assisting a driver of a motor vehicle, comprising the steps of:

Measuring at least one value of at least one vital parameter of the driver correlated with the driver's mental condition and / or at least one value of at least one vehicle dynamics quantity correlated with the driver's mental condition;

Classifying the mental condition of the driver based on the measured value of the vital parameter or the vehicle dynamics quantity; and

Generating a signal perceivable by the driver by a driver assistance system of the motor vehicle, wherein the signal is selected from a plurality of different signals depending on the classification of the mental state of the driver, or suppressing a signal of the driver assistance system and / or selecting at least one vehicle parameter in dependence Classification of the mental condition of the driver.

The method according to the invention therefore provides that signaling of the vehicle, e.g. signaling a driver assistance system that takes into account the driver's mental condition; In particular, an individual mental condition is considered, which may be e.g. is an under- or over-demanding condition, an emotional condition (e.g., strong positive or negative arousal), or any other condition of reduced attention. It is also possible that the mental state is determined by the intention of the driver. The classification of the mental state takes place, in particular, on the basis of individually defined limit values for the values of the vital parameter or the driving dynamics variable (s.u.).

The signal and / or the vehicle parameter are e.g. a signal or a parameter of a safety device, a driver assistance system (as already mentioned), a device for influencing the driving dynamics and / or a comfort system of the vehicle.

Depending on the determined mental state of the driver, for example, a signal (for example a signal perceivable by the driver, eg an optical, acoustic and / or haptic signal) of an assistance system of the vehicle can be selected which the driver does not disturb or whose information content it can capture as quickly and correctly as possible. Warnings to the driver can thus be adapted to his current mental state, whereby, for example, in the case of a driver who has already been determined to be stressed, the warnings are greatly reduced and triggered only with high urgency. It is also conceivable that, for example, in the case of a detected mental state which corresponds to a state of increased stress, ie a state of overworking, signaling of the assistance system or of another system of the vehicle is completely suppressed.

It is noted that the wording that the driver perceivable signal is "selected" depending on the classification means, in particular, that adequate signaling is selected from a plurality of available signals (signaling) Signals the aforementioned optical, acoustic and / or haptic signals, wherein the various available signals relate in particular to the same function of the vehicle and thus in particular transport the same information (such as a warning) Type are available, for example, a plurality of optical signals, including, for example, a first optical signal that responds to the focal visual perception channel of the driver (such as a rather static signal), and a second optical signal that responds to the driver's ambient perception channel (ei about n rather dynamic signal).

Instead of selecting a signal, signaling of the vehicle may also be suppressed, i. Signaling that would have occurred under standard conditions is prevented. By "standard conditions" is meant, in particular, a condition corresponding to a vehicle without the classification according to the invention or a normal mental condition of the driver, ie in particular that the driver is in a reasonably attentive condition Although the vehicle generates a signal (in particular an electrical signal) that indicates, for example, that a driver's reaction is expected (for example, an indication of insufficient tire pressure), a signal perceptible by the driver is omitted.

Likewise, with a higher mental stress experienced by the driver, comfort systems could be placed in the background to provide additional stimuli to the perception of the driver To reduce the driver. In this case, a correspondingly designed feedback to the driver can be made and a possibility can be provided to be able to switch on desired systems in the simplest possible way again. When changing parameters of a comfort system, for example, the recognition of an intention of the driver plays a role. Therefore, when classifying the mental state, data (eg, from a diary) from a vehicle computer may be included, eg, to determine the type of ride and any driver's deadline.

Moreover, depending on the classification of the driver's mental condition, e.g. if a condition of significant over-demand or under-demand is detected, a vehicle parameter will be changed. For example, the driving dynamics of the vehicle or other variables (such as the maximum speed) of the vehicle can be changed. It is also conceivable that parameters of a (for example passive) safety system of the vehicle be changed. For example, the timing of activating a seatbelt pretensioner of a seatbelt system and / or triggering an airbag of the vehicle could be changed (e.g., advanced). It is also possible that a pre-crash system is triggered at a different (especially earlier) time, e.g. an inflatable element of the pre-crash system is activated and / or the brake pressure increased at a different time and / or an automatic deceleration of the vehicle is initiated.

In addition, parameters of an active safety system (such as an ESP system) of the vehicle may also be changed depending on the classification of the mental state, e.g. be switched to a higher, more cautious attention level. This allows e.g. Also, a better prevention of false alarms, so incorrectly triggered warnings, since it can be detected whether a driving situation was deliberately caused by the driver or unintentionally developed and thus critical.

It is also conceivable that, based on the classification of the driver's mental condition, it is determined whether and, if so, to what extent the driver wishes to automate the driving. In some situations, a driver wants to give specific tasks, in others but also like to drive the car and enjoy this ride. Determining (the classification) The mental state of the driver, for example, allows better recognition of what is desired by the driver, and thus, for example, smoother transitions between different stages of driving automation.

The method according to the invention can also promote energy-efficient driving. This is e.g. enabled by the inclusion of environmental factors and e.g. Vehicle-to-vehicle communication ("Car-2-X communication"), for example, can be detected as to how far a green traffic light can still be driven over, or better an early, slow braking - of course, taking into account the traffic flow - By classifying the driver's condition, an improved response to other road users could also be made possible, and it would also be possible to identify which drivers are stressed on a predefined route and to redirect traffic accordingly or to pay particular attention to these drivers ,

According to one embodiment of the invention, an expected range of values subdivided into at least one first and one second classification range is determined for the vital parameter and / or the vehicle dynamics quantity used to classify the driver's mental condition, the classification ranges respectively being different mental states of the driver Driver correspond and the measured value of the vital parameter or the vehicle dynamics quantity are assigned to the first or the second classification range. The subdivision of the value range is carried out in particular individually (relative to a specific driver), whereby, as already mentioned above, individual class limit values are defined which delimit the classification ranges from one another. The definition of the class limit values can be made by calibrating the measuring device used to determine the vital parameter and / or the driving dynamics variable to a specific driver. For example, the calibration may be e.g. be updated regularly.

For example, the mental state associated with the first classification area corresponds to an under-demand of the driver and the mental state of the driver assigned to the second classification area corresponds to an excessive demand of the driver. It is of course also possible that the classification areas other mental states (see above) are assigned. Of course, more than two classification ranges can be used to allow the most accurate classification of the mental state. According to a development of this embodiment of the invention, the selection of a signaling (of a signal) takes place in that at least a first signal perceivable by the driver and the second classification region is assigned to the first classification region at least a second signal perceptible by the driver (the first signal of the second signal is different), wherein the first signal is generated when the measured value of the vital parameter has been assigned to the first classification range, and the second signal is generated when the measured value of the vital parameter has been assigned to the second classification range. As already indicated above, the first and the second signal can be different types of signals or variants of the same signal type, for example an optical signal, for example a first signal which responds to the driver's focal visual channel a second signal that responds to the driver's ambient perception channel.

The value of the vital parameter is e.g. by determining the electrodermal activity, by means of an electrocardiogram, a gaze motion measurement and / or a pupillometric measurement. The possibly recorded driving dynamics quantity is e.g. to accelerate the vehicle, e.g. is determined with sensors of an ESP system of the vehicle. Furthermore, e.g. a standard deviation from the lateral position, a number of steering movements, a mean difference between an allowed and the actually driven speed, and / or a steering angle are used as vehicle dynamics quantities.

The invention also relates to a support system for assisting a driver of a motor vehicle, in particular for carrying out a method as described above

a measuring device for measuring at least one value of at least one vital parameter of the driver correlated with the mental state of the driver and / or at least one value of at least one driving dynamics variable correlated with the mental state of the driver;

a classification device for classifying the driver's mental condition based on the measured value of the vital parameter or the vehicle dynamics quantity; and a device for selecting a signal perceptible by the driver or suppressing a signaling of the vehicle and / or selecting at least one vehicle parameter as a function of the classification of the mental state of the driver.

According to a further aspect, the invention relates to a measuring method for determining a mental state of a driver of a motor vehicle, comprising the steps:

a) generating a first signal perceivable by the driver, which signals the driver that a first action is expected from him;

b) generating a second signal perceptible by the driver that signals the driver that a second predetermined action is expected from him, the first signal from the second signal and / or the expected first action being different from the expected second action; and

c) measuring at least one value of at least one vital parameter of the driver correlated with the driver's mental condition and / or at least one value of at least one vehicle dynamics variable correlated with the driver's mental condition during generation of the first signal and / or performing the first action by the driver as well as during the generation of the second signal and / or the driver performing the second action.

The measuring method can serve, in particular, to determine the mental load that arises on a driver by signaling the vehicle (in particular a driver assistance system). It is conceivable to carry out the above-described inventive assistance method on the basis of these measurements, assigning appropriate driver assistance system signals (or signals from another vehicle system) to different driver mental states, of which, depending on the classification of the driver's mental condition Driver's one is selected.

For example, if the measurements made using the measurement method of the present invention indicate that an optical signal that predominantly addresses the driver's focal visual perception channel generates less driver stress than other signals (eg, as a visually perceptible signal representing the driver's ambient perception channel) at- speaking), such a visual signal could be assigned to a mental override condition in order to generate the least possible additional mental load on the driver.

In particular, the measuring method is carried out with the aid of a driving simulator, which uses different signals, e.g. typically generated by driver assistance systems can generate. By way of example, the first and / or the second signal of the measuring method is a signal which the driver perceives visually, audibly, tactually and / or olfactorily. It should be noted that the first and the second signal may well consist of a language information that is transmitted to a subject; e.g. a task given to him acoustically (for example by loudspeaker) or visually (for example by display on a display).

In addition, the steps a) to c) can be performed several times, wherein the type of the first signal and / or the type of the second signal are different in each implementation. The repetitions serve to determine the mental stress of a plurality of combinations of the signals. For example, at least two implementations of steps a) to c), wherein in the first implementation as the first and / or second signal, a visually perceptible signal and in the second implementation of an acoustic signal is used. It is also conceivable that in the first implementation, a visually perceptible signal of a second type is used as the first and / or second signal of a first type and in the second implementation. According to a further development of this variant, the visually perceptible signal of the first type is a signal which responds to the driver's focal visual perception channel, and the visually perceptible signal of the second type is a signal representing the driver's ambient perceptual channel responds. It is conceivable, of course, e.g. also that different acoustic signals are used. Possible signals and possible types of expected actions are summarized in Table 1 below.

The value of the at least one vital parameter is determined, for example, by determining the electrodermal activity, by means of an electrocardiogram, an eye movement measurement and / or a pillometric measurement. The vital parameters of the driver used are, for example, the following: an electrodermal activity (EDA);

- with the help of an electrocardiogram (ECG) certain variables such as nonspecific fluctuations, a tonic level, heart rate, heart rate variability (0.1 component), and also a reference EDA and ECG (non-specific fluctuations, tonic level, heart rate, heart rate variability (0.1 component) can be determined;

- Measures such as the direction of vision, the number of fixations on specific target areas ("Areas of Interest" - AOI), fixation duration on AOI, fixation site, number of saccades, saccade duration, lid closure frequency;

- quantities determined by means of pupillometry, such as the amplitude of changes in phasic dilatations of the pupil (for example, between 0.1-0.6 mm), "index of cognitive activity (ICA)" - index of cognitive activity

Some of the above Vital parameters can be determined by means of a measuring device which is integrated in a steering wheel of a vehicle. For example, the measuring device comprises at least one electrode which is arranged on a steering wheel rim of the steering wheel.

The at least one vehicle dynamics quantity correlated with the driver's mental condition is e.g. by a standard deviation from the lateral position, the number of steering movements, the mean difference between a permitted and actually driven speed and / or the steering angle. When carrying out the method according to the invention with the aid of a driving simulator, these variables result from the driving simulator data.

Since a number of different influencing parameters (covariables) can influence the result of the measuring process, these are e.g. also recorded and controlled. For example, the following covariables of test drivers (subjects) are examined: gender, age, driving experience, possibly simulator experience, last hand wash, last sporting activity, drug and caffeine consumption, current mental state (eg tired or recovered), time, temperature, noise, road conditions , Road conditions, season, humidity, wind, vehicle type and / or traffic density.

The measuring procedure is carried out, for example, as follows: EDA & ECG measuring probes are applied to the test person. In order to identify so-called "non-responders" (about 5% of the population), ie persons, in which no EDA signal can be detected Invite subjects to take a deep breath and hold their breath. This will also generate and measure a baseline level of EDA and ECG.

Subsequently, e.g. filled out two questionnaires (eg according to "NASA Task Load Index" - NASA TLX - NASA Stress Index and / or "SAM" - Self-Assessment Manikin - self-assessment manikin) to record the basic load and the general level of agitation of the test person , For example, the subject will then be presented with a demographic questionnaire, particularly to capture the covariables mentioned above, sex, age, driving experience, simulator experience, last hand wash, last physical activity, drug and caffeine consumption and current mental condition. Meanwhile, the experimenter fills out an experimental protocol sheet on time, temperature, noise, road condition, road conditions, season, humidity of wind and vehicle type. The traffic density and possibly occurring noise disturbances are logged during the experiment.

Subsequently, an eye movement measuring apparatus and a pupillometry apparatus are calibrated. After that, the test person is enabled, for example, to drive in the driving simulator or in the real vehicle. After some practice time, a basic level of the mileage and the respective driving dynamics parameters is recorded. In the actual performance of a measurement, depending on the target direction of the measurement, different tasks, i. actions anticipated by the driver (by the subject). In particular, the tasks are designed to test different input and output modalities of the subject's perception.

Furthermore, a distinction can be made between the examination of a pure reaction performance (eg the requirement to say "yes" when a stimulus is presented in the form of the first signal) and the different levels of a cognitively demanding task (eg easy, medium and difficult). Tasks that are not directly relevant to the driving task (ie the "first action") are referred to as secondary tasks ("second action"), while secondary tasks are used by varying degrees of stress (ie, by designing the "second signal") the driver in the driving data by his driving performance clearly. It is possible, for example, to use the first and second signals or first and second actions which are combined in the following Table 1 and which are combined with one another for the purpose of detecting a mental stress:

In the case of # 1, the subject is presented with a visual stimulus as the first perceptible signal (eg, a flashing LED) to which the subject should respond verbally (eg, "yes") ("expected first action"). In the second case, the test person is also presented with a visual stimulus as the first perceptible signal (eg also a flashing LED), to which it has to respond by motor (eg by pressing a button). In the third case, the subject is given a cognitive task by means of a visual second signal (eg, an ad on a display) that must verbally ("expected second action"), eg, by directional instructions.

In the fourth case, the test subject is e.g. Also on a display give a cognitive task that they can operate by operation via buttons or directly on a touch screen motor. In the fifth case, the test person has to react verbally (eg with "yes") to a first signal in the form of an acoustic stimulus (via loudspeaker), in the sixth case by motor by pressing a button In the seventh case the test person is informed by means of a second signal in Form of an acoustic signal (also via loudspeaker) presented a task that she must work through verbal answer (for example, the solution of the task to be spoken).

In the eighth case, the test person is again acoustically (via loudspeaker) presented a task by means of a second signal in the form of an acoustic signal, the solution of which is to be entered via a display by means of keys or a touch surface ("expected second action") a stimulus ("first signal") simultaneously visually and acoustically presented (eg an ad appears on a display and it is simultaneously an instruction by loudspeaker), the test person should respond verbally to this first signal (eg with "yes").

In the tenth case, a visual and audible first signal is also presented (eg a display appears again on a display and an instruction is also given by loudspeaker), whereby the test person is to respond to this by motor (eg by pressing a button). In the eleventh case, a task is presented by a second signal in the form of both a visual and an audible signal (eg, by the mentioned combination of a display on a display and an instruction by loudspeaker), the expected second action being for the subject to test Solution of the task should say aloud. In the twelfth case, a task is also presented visually and acoustically at the same time, whereby the test person solves the problem as an expected second action via keys or directly on a touch sensitive disc. to play (touch display) by motor. As mentioned, the variants compiled in the table can be combined with each other. In particular, the first signals and first actions contained therein can be combined with the second signals and second actions mentioned in the table. The second signals are generated in particular temporally after the first signals.

The acoustic first and / or second signals may e.g. in the form of the following acoustically or visually transmitted tasks (Table 2):

The type of task transmitted by means of the first and / or second signal consists either in a task that requires only a reaction of the test person or a mentally demanding task (cognitively). The "N-back" task is a specific stress task that has a light, medium, and heavy level, where at the light level, a subject must repeat a number that was presented to him in the acoustic modality (Example: Presentation = 3, Subject answers "3"), in the middle the subject must name the number presented before the last number (example: presentation = 3 - 5 - 2 - 1, subject responds "-", "3", "5" , "2"), so this includes memory effort, and in the hard stage, the subject must name the number that was presented before the penultimate number (example: presentation = 3 - 5 - 2- 1, subject responds "-" , "-" "N-Back with Interface Interaction" means that the test person does not respond verbally, but rather selects the number by input means (eg switch or touch screen) and thus outputs it manually via an interface (to a machine), which corresponds to the output modality "motor" in Table 1 .

The tasks are transmitted to the test person either acoustically (in particular by loudspeaker announcement), visually (in particular by display on a display) or acoustically-visually (in particular both by loudspeaker and via an indication on a display).

The tasks transmitted by the first and / or second signals are e.g. sufficiently practiced with the subject until fully understood and mastered to avoid learning effects or misunderstandings. The aim is in particular to classify the exact individual pattern with different demands of the driver. Individual patterns are the expression of the stresses in the physiological data (EDA, ECG, eye movement, pupillometry), which vary greatly depending on the individual. The objective is to recognize the driving ability on the basis of these patterns and to carry out a correspondingly appropriate adaptation of the vehicle (assistance systems and comfort functions), as described above in relation to the first aspect of the invention. The measuring method according to the invention could therefore also be implemented in a production vehicle.

At the end of the testing (i.e., after completion of the measuring method according to the invention, in particular after completion of several passes of the measuring method according to the invention), in addition, the maximum possible span of the EDA signal can be tested. This can be done, for example, by the so-called "shockpattern method", whereby an involuntary reaction of the subject is caused by a loud bang (eg in which the experimenter beats the table) For example, at the end of the measuring procedure, the test person fills in the questionnaires NASA-TLX and SAM again.

The invention also relates to a measuring system for determining a mental state of a driver of a motor vehicle, with

a generating device for generating a first signal perceivable by the driver, which signals to the driver that a first action is expected from him, and for generating a second signal perceptible by the driver, which signals to the driver that a second predetermined action is expected from him, the first signal from the second signal and / or the expected first action being different from the expected second action; and

a measuring device for measuring at least one value of at least one vital parameter of the driver correlated with the mental state of the driver and / or at least one value of at least one driving dynamics variable correlated with the driver's mental state during the generation of the first signal and / or the performance of the first action by the driver as well as during the generation of the second signal and / or the driver performing the second action.

The measuring system according to the invention is in particular part of a driving simulator or works together with a driving simulator. However, it is also conceivable that the measuring system is arranged in a vehicle (for example, also in a production vehicle). In both cases, the measuring device of the measuring system can be integrated in a steering wheel. It is conceivable, for example, that electrodes and / or other sensors for carrying out an EDA and / or ECG measurement are integrated in the steering wheel in the steering wheel.

The invention is explained in more detail below with reference to embodiments with reference to the figures. Show it:

Fig. 1 the Wickens cube; and

2 shows a steering wheel for carrying out the measuring method according to the invention.

One known model of human information acquisition and processing and the response to information is the so-called Wickens cube illustrated in FIG. The Wickens model presented with this cube connects different aspects (modalities, involved sensory channels, codes and levels) of information processing. In particular, the aspects (resources) are each regarded as dichotomous. Basically, human behavior is divided into the phases of "perception", "storage and processing" (cognitive work) and the production of a response. The perceptual forms ("perceptual modalities") are subdivided into visual, auditory or tactile information, assuming that these different modalities are processed differently, and within the visual modality are two visual sensory channels, namely a focal and an ambient channel The main task of the focal channel is object recognition, while the ambience channel is responsible for the perception of movement and orientation.The different "codes" are understood to be the spatial, analogous storage of information and the verbal, symbolic or pictorial storage. "Levels" refer to different processing resource levels.

With the aid of the measuring method according to the invention, it is possible in a determination of a mental state of a driver of a motor vehicle between the pure stimulus recording (based on a "first signal" presented to the driver) and the cognitive processing (based on a "second signal" presented to the driver). ) to distinguish. Moreover, when examining the impact of the recorded information on the driver's mental condition, a distinction can be made between information received in different modalities (in particular, visual, auditory or tactile). The findings obtained with the aid of the measuring method according to the invention can be used in particular to adapt the signaling of a vehicle (for example a driver assistance system) (for example driver-individual), as explained above.

2, a steering wheel 1 is shown, which comprises a measuring device 2, which is part of a measuring system according to the invention (not shown) for carrying out the measuring method explained above. The remaining components of the measuring system could be integrated together with the steering wheel 1 in a vehicle. In particular, the steering wheel could be installed as part of the support system according to the invention in a production vehicle.

The measuring device 2 is designed to determine various vital parameters ("psychophysiological parameters") which correlate with the mental state of a driver, In particular, the measuring device has electrodes 21, 22 which each serve as an ECG and / or EDA electrode The electrodes 21, 22 are, for example, dry electrodes Electrodes 21, 22 together extend over nearly the entire outer periphery of the steering wheel rim to ensure that the driver is in contact with at least one of the electrodes. Furthermore, the electrodes 21, 22 have a large surface area; For example, they also extend (eg at least approximately completely) around a skeleton of the steering wheel rim, ie they extend over a large part of the circumference of the steering wheel skeleton, which lies in a plane oriented perpendicular to the outer circumference. The electrodes 21, 22 have a particularly large area, in particular at the usual gripping points of a steering wheel.

The current mental state of the driver will be reflected in (in particular driver-specific) EDA and / or ECG values which, on the one hand, can be used to determine the effects of different stimuli on his mental state or in a production vehicle within the scope of the measuring method according to the invention to classify the driver's mental condition and to adapt signaling of the vehicle based on the classification, as explained above.

The measuring device integrated in the steering wheel 1 also has an evaluation unit 23, which detects and evaluates the electrical signals received by the electrodes 21, 22. For example, the evaluation unit 23 detects a heart rate of the driver. The source of the human heartbeat is an electrical impulse generated by a cluster of cells within the heart. Since this pulse is transmitted via the bloodstream, it can be detected as a potential difference between two points on the body. The electrodes 21, 22 of the steering wheel 1 are designed so that the heart activity of the driver can be detected as a potential difference between the two hands of the driver. For this purpose, the electrodes 21, 22 each consist of two segments, and the evaluation unit 23 has a differential amplifier in order to be able to register very small potential differences, as well as a processing unit for filtering out interference signals.

The electrodes 21, 22 also serve as temperature sensors, with which the skin temperature can be determined as another vital parameter. Body temperature (and thus skin temperature) is considered to be an indicator of the driver's mental condition and is controlled by the central nervous system as thermoregulation. The normal skin temperature of the hand varies in the range between 20 ° C and 40 ° C. By controlling the central nervous system, the Body temperature can be regulated by the sweat ß process. Thus, the activity of the sweat glands provides feedback on the sympathetic nervous system and is a feature to assess the condition of the driver.

Ekkrine sweat glands have a wide spread throughout the body, especially on the hands, feet and forehead. Their density on hand is over 2000 / cm ² . Ekkriner sweat consists of water and salts, with which the glands are either filled or not. Therefore, the activity of the sweat glands can be measured electrically as a change in the conductivity of the skin. In general, the change in conductivity of human skin is in the range between 0 and 50 or equivalent to the resistance of human skin between 20kQ and infinity. Accordingly, the electrodes 21, 22 may be configured to measure the conductivity of the driver's skin.

In particular, conductivity measurement is based on the voltage divider principle which requires two contacts on the skin. A pole is e.g. set to a DC voltage of 0.5 V, and the other is the potential measurement, which is dependent on the glandular activity. The resistance value of the voltage dividing resistor is set to e.g. 180kQ. This means in particular that a voltage is applied to the resistor, which varies between 0 V and 0.25 V. This signal is e.g. Amplified 8 times and in particular a low pass with a cutoff frequency of e.g. 10 Hz for filtering out the EDA signal over it.

It is noted that a DC voltage of 0.5V is not dangerous to humans. The maximum allowable voltage is 0.7V to prevent nerve cell excitation. Also, no cells can take damage by heating or burning, as the maximum input current, e.g. 0.5V x 0.5V x δθμβ = 12.5 μΑ.

The temperature range for the operation of the steering wheel and the electrodes 21, 2 is e.g. between -40 ° C and + 85 ° C. The bearing of the steering wheel is e.g. at temperatures between -40 ° C and + 125 ° C possible, in which temperature range, a relative humidity between 5 and 95% is expected.

Claims

claims

1 . A method of assisting a driver of a motor vehicle, comprising the steps of:

Classifying the mental state of the driver based on the measured value of the vital parameter or the driving dynamics quantity; and

Generating a signal perceivable by the driver by a driver assistance system of the motor vehicle, wherein the signal is selected from a plurality of different signals depending on the classification of the driver's mental state, or suppressing a signal of the driver assistance system and / or selecting at least one vehicle parameter in dependence the classification of the mental condition of the driver.

2. The method according to claim 1, characterized in that the signal and / or the vehicle parameter is a signal or a parameter of a safety device, a driver assistance system, a device for influencing the driving dynamics and / or a comfort system of the vehicle.

3. The method according to claim 1 or 2, characterized in that for the vital parameter and / or the driving dynamics variable in each case a subdivided into at least a first and a second classification range expected range of values is determined, the classification ranges correspond to different mental states of the driver and the measured value of the vital parameter or the driving dynamics quantity are assigned to the first or the second classification range.

4. The method according to claim 3, characterized in that the expected value range is divided into more than two classification ranges.

5. The method according to claim 3, wherein the mental state assigned to the first classification area corresponds to an under-demand of the driver and the mental state of the driver assigned to the second classification area corresponds to an excessive demand of the driver.

6. The method according to any one of the preceding claims, characterized in that the motor vehicle generates a signal indicating that an action of the driver is expected, said signal depending on the classification of the mental state of the signals provided by the motor vehicle signals is selected.

7. The method according to claim 6, characterized in that the signal of the vehicle is generated by a driver assistance system and / or a comfort system of the vehicle.

8. The method according to any one of the preceding claims as far as dependent on claim 3, characterized in that

at least a first signal perceptible by the driver is associated with the first classification region and at least one second signal perceptible by the driver is associated with the second classification region, the first signal being different from the second signal,

and wherein the first signal is generated when the measured value of the vital parameter has been assigned to the first classification range, and the second signal is generated when the measured value of the vital parameter has been assigned to the second classification range.

9. A support system for assisting a driver of a motor vehicle, in particular for carrying out a method according to one of claims 1 to 8, with

a classification device for classifying the driver's mental condition based on the measured value of the vital parameter or the vehicle dynamics quantity; and

a device for selecting a signal perceptible by the driver or suppressing a signaling of the vehicle and / or selecting at least one vehicle parameter as a function of the classification of the mental state of the driver.

10. A measuring method for determining a mental state of a driver of a motor vehicle, comprising the steps of:

c) measuring at least one value of at least one vital parameter of the driver correlated with the driver's mental condition and / or at least one value of at least one vehicle dynamics variable correlated with the driver's mental condition during generation of the first signal and / or performing the first action by the driver Driver and during the generation of the second signal and / or making the second action by the driver.

1 1. A measuring method according to claim 10, characterized in that the first and / or the second signal to the driver is visually, auditory, tactile and / or olfactory perceptible signal.

12. Measuring method according to claim 10 or 1 1, characterized in that the steps a) to c) are carried out several times, wherein different first and / or second signals are used in each implementation.

13. A measuring method according to claim 12, characterized in that at least two implementations of steps a) to c) were carried out, wherein in the first implementation as a first and / or second signal, a visually perceptible signal of a first type and the second implementation of a visually perceptible Signal of a second type is used.

14. A measuring method according to claim 13, characterized in that the visually detectable signal of the first type is a signal responsive to the driver's focal visual perception channel and the visually detectable signal of the second type is a signal indicative of the signal Ambient perception channel of the driver responds.

15. Measuring method according to one of claims 10 to 14, characterized in that the value of the vital parameter is determined by determining the electrodermal activity, by means of an electrocardiogram, a gaze motion measurement and / or a pupillometric measurement.

16. The measuring method according to claim 10, characterized in that for the at least one vital parameter an expected range of values subdivided into at least one first and one second classification range is determined, wherein the classification ranges respectively correspond to different mental states of the driver and the measured value of the vital parameter are assigned to the first or the second classification area.

17. Measuring system for determining a mental state of a driver of a motor vehicle, in particular for carrying out a measuring method according to one of claims 10 to 16, with

a generating device for generating a first signal perceivable by the driver which signals to the driver that a first action is expected from the driver, and for generating a second signal perceptible by the driver, which signals the driver that a second predetermined action from him expected, wherein the first signal from the second signal and / or the expected first action is different from the expected second action; and

18. Measuring system according to claim 17, characterized in that the measuring device (2) is integrated in a steering wheel (1) of a motor vehicle.