Method for operating an assist system for a vehicle, and assist system

Abstract

A method for operating an assist system for a vehicle that includes a sensor device for detecting a directional characteristic value that is representative of a viewing direction of a driver of the vehicle. In the method, a calibration characteristic value is provided that is representative of a rest viewing direction of a standard driver. At least one initial direction characteristic value is determined, in dependence of which a rest characteristic value is determined that is representative of a rest viewing direction of the driver. A transformation characteristic value is determined based on the rest characteristic value, which is representative of a transformation between the rest characteristic value and the calibration characteristic value. Based on the transformation characteristic value, subsequently determined directional characteristic values are corrected.

Claims

1. A method for operating an assistance system for a vehicle including a sensor device for determining a direction characteristic value representative of a viewing direction of a driver of the vehicle, comprising the acts of: providing a calibration characteristic value representative of a resting viewing direction of a standard driver, wherein the calibration characteristic value describes a head pose of the standard driver and wherein the resting viewing direction of the standard driver is looking straight ahead; determining at least one initial direction characteristic value of the driver, wherein the at least one initial direction characteristic value describes a head pose of the driver; determining a resting characteristic value representative of a resting viewing direction of the driver on a basis of the at least one initial direction characteristic value; determining a transformation characteristic value representative of a transformation between the resting characteristic value and the calibration characteristic value on a basis of the resting characteristic value and the calibration characteristic value; and correcting subsequently determined direction characteristic values on a basis of the transformation characteristic value.

2. The method according to claim 1, wherein the resting characteristic value is respectively determined in predefined time windows which are spaced apart.

3. The method according to claim 1, wherein the resting characteristic value is also determined on a basis of one or more of: a current steering angle and/or a yaw rate of the vehicle; a current deviation of the direction characteristic value from the calibration characteristic value; and a road type currently being traveled on by the vehicle.

4. An assistance system for a vehicle, comprising: a control unit which is configured to perform the method according to claim 1.

5. A non-transitory computer readable medium comprising executable program code, wherein the program code carries out the method according to claim 1 when executed by a data processing apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The FIGURE shows an exemplary flowchart of a method for operating an assistance system according to the invention.

DETAILED DESCRIPTION OF THE DRAWING

(2) The FIGURE shows an exemplary flowchart of a method for operating an assistance system according to the invention. The assistance system may be, for example, an apparatus for capturing visual attentiveness of the driver, which apparatus is configured to detect a head pose of the driver and to initiate further steps on the basis thereof. For example, the determined head pose can be used to monitor the driver's attentiveness and to utter warnings if necessary. Alternatively or additionally, the determined head pose can be used to assist with detecting the viewing direction and/or to deliberately activate additional functions of the vehicle.

(3) The assistance system comprises a sensor unit having a camera which is arranged in a manner facing the driver and is configured to capture his/her head pose. Additionally, the camera can be configured to capture a viewing direction and/or a head position of the driver. When determining the head pose, viewing direction and/or head position, anatomical features such as the nose (tip), eye and/or pupil position, corners of the eyes and/or corners of the mouth of the driver and relationships between these features can be used, for example. The sensor unit can also comprise an optional lighting device. The assistance system also comprises a control unit having a data and program memory which stores a program for operating the assistance system, which program is explained in more detail below on the basis of the flowchart in the FIGURE.

(4) The program is started in a step S1 in which variables are initialized, for example. At this time, it is possible to provide, in particular, a calibration characteristic value K which is representative of a resting head pose of a standard driver, that is to say a head pose of an average driver when “looking straight ahead”. The program is then continued in a step S3.

(5) In step S3, a predefined time window Z for calibrating the assistance system is started. This can be carried out once for the purpose of activating the vehicle or else at the beginning of a (each) journey with the vehicle, for example. In other embodiment variants, the predefined time window Z can also be started after expiry of a predefined interval of time (for example every 2 hours), for example in order to ensure that the assistance system is continuously calibrated. The program is then continued in a step S5.

(6) In step S5, the sensor unit is used to determine a direction characteristic value R which is representative of a current head pose and/or a current viewing direction of the driver. The program is then continued in step S7.

(7) In step S7, a check is carried out in order to determine whether there are specific conditions which allow the calibration to be carried out. For example, for this purpose, a current speed v of the vehicle is determined in a step S7a and a check is carried out in order to determine whether a predefined minimum speed v.sub.min of the vehicle has been reached or exceeded. If the current speed v is below the predefined minimum speed v.sub.min, the current direction characteristic value R is not taken into account. In this case, the program is continued in step S5 after a predefined waiting time.

(8) Otherwise, the program is continued, for example, in a step S7b in which a current rotation Φ of the vehicle is determined and a check is carried out in order to determine whether a predefined maximum rotation Φ.sub.max of the vehicle has been reached or exceeded. An adopted steering angle and/or a yaw rate of the vehicle, for example, can fall under a rotation Φ of the vehicle. If the current rotation Φ of the vehicle is above the predefined maximum rotation Φ.sub.max of the vehicle, the current direction characteristic value R is not taken into account. In this case, the program is continued in step S5 after a predefined waiting time

(9) Otherwise, the program is continued, for example, in a step S7c in which a current rotation Θ of the driver's head is determined and a check is carried out in order to determine whether a predefined maximum rotation Θ.sub.max of the driver's head has been reached or exceeded. The rotation Θ of the driver's head can be derived, for example, from the current direction characteristic value R. In particular, the rotation Θ of the driver's head can be determined on the basis of the (uncalibrated) direction characteristic value R and the calibration characteristic value K which has been provided and is stored, for example, in the memory. In this context, a deviation of the direction characteristic value R from the calibration characteristic value K is determined, for example. If the current rotation Θ of the head is above the predefined maximum rotation Θ.sub.max of the head, the current direction characteristic value R is not taken into account. In this case, the program is continued in step S5 after a predefined waiting time.

(10) Otherwise, the program is then continued in step S9. In a manner differing from the illustrated and described embodiment variant, individual or all substeps S7a-S7c can be run through in another order or may be only optional in further embodiment variants.

(11) In step S9, the direction characteristic value R currently determined by the sensor unit is written to a buffer. The program is then continued in a step S11.

(12) In step S11, a check is carried out in order to determine whether the predefined time window Z has expired. In this case, the program is continued in a step S13; otherwise, the program is continued in step S5.

(13) In step S13, a resting characteristic value P representative of a resting head pose of the driver, that is to say an individual head pose of the driver when “looking straight ahead”, is determined on the basis of the direction characteristic values R in the buffer. For this purpose, the direction characteristic values R are accumulated, for example, and a mean value or the like is determined. The resting head pose can also be referred to as a “normal zero head pose”. The program in is then continued in a step S15.

(14) In step S15, a transformation characteristic value T representative of a transformation between the resting characteristic value P, that is to say, for example, an average resting head pose of the driver, and the calibration characteristic value K, that is to say an average resting head pose of other drivers, is determined. The transformation may be, in particular, a rigid transformation which can be described, for example, by a homogeneous 4×4 transformation matrix as the transformation characteristic value T. The resting characteristic value P and the calibration characteristic value K can be described, for example, as homogeneous vectors in this context. The transformation characteristic value T can then be stored for the corresponding driver and the program can be ended. Alternatively, the program can then also be continued in a step S17.

(15) In step S17, the transformation characteristic value T for the corresponding driver is provided. Furthermore, a new, current direction characteristic value R.sub.neu is determined. A corrected direction characteristic value R.sub.korrigiert is then determined on the basis of the transformation characteristic value T and the new direction characteristic value R.sub.neu. The corrected direction characteristic value R.sub.korrigiert is representative, in particular, of a head pose of the driver which is compensated for by the unknown individual anatomy of the driver.

(16) In other words, the measured direction characteristic value R.sub.neu can be corrected with the transformation for all future measurements provided by the sensor unit. In the case of a homogeneous 4×4 transformation matrix, this would correspond to a matrix-vector multiplication of the transformation characteristic value T by the homogeneous vector, the direction characteristic value R.sub.neu, which describes the measured head pose.

(17) The program can then be continued in a step S19 in which a control signal for operating further functions of the vehicle is determined on the basis of the corrected direction characteristic value R.sub.korrigiert. The program is then ended.

(18) In this embodiment variant, steps S5 to S15 are repeated only until a predefined time window Z has expired. In other embodiment variants, an interval of time can be started in step S15 after expiry of the predefined time window Z, after the expiry of which interval of time the program begins again in step S3 in order to thus carry out a continuous calibration at defined intervals of time.

(19) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.