Abstract:
The present invention relates to a method and apparatus for determining a head position of a vehicle driver that has non-limiting advantages of enhanced accuracy and/or precision without excessive increase of manufacturing cost of the vehicle. A vehicle is provided with at least one of a left rearview mirror and a right rearview mirror, a head position of a vehicle driver may be determined on the basis of at least one of vertical and horizontal inclination angles of the at least one rearview mirror.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority of Korean Application No. 10-2003-0051907, filed on Jul. 28, 2003, the disclosure of which is incorporated fully herein by reference. 
   FIELD OF THE INVENTION 
   Generally, the present invention relates to a vehicle. More particularly, the present invention relates to a method and apparatus for determining a head position of a vehicle driver. 
   BACKGROUND OF THE INVENTION 
   Recently, vehicle safety has become a much more important factor in vehicle manufacture, and accordingly, techniques for determining a head position of a driver have garnered strong interest. For instance, the head position of the driver may act as an important parameter in an algorithm for controlling operation of an air bag. 
   In one known way of determining the head position of the driver according to the related art utilizes the position of the driver&#39;s seat in a front and rear direction. A sensor may be used for detecting a seat position of a seat moving track, and on the basis of the output of the sensor, the head position of the driver may be estimated. Such an estimate, however, may result in rough measurement of the head position. 
   For example, the head position of the driver may vary at the same seat position, according to how much a seat back is inclined, and/or the posture of the driver. Therefore, sufficient accuracy and/or precision may not be expected from such a method of determining the head position of the driver. 
   One of the ways that may be expected to show enhanced precision/accuracy is through disposing a camera in an interior of the vehicle and calculating the head position of the driver from an image obtained by the camera. However, this approach may only be enabled by adopting a stereo camera or at least two normal cameras, which results in an excessive increase of manufacturing cost of the vehicle. 
   The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a method and apparatus for determining a head position of a vehicle driver that has non-limiting advantages of enhanced accuracy and/or precision without excessive increase of manufacturing cost of the vehicle. 
   An exemplary method according to an embodiment of the present invention determines a head position of a driver of a vehicle, the vehicle being equipped with at least one of left and right rearview mirrors. 
   In the exemplary method, in at least one of horizontal and vertical directions, an inclination angle of the at least one rearview mirror may be detected, and subsequently, a range of the head position of the vehicle driver may be calculated on the basis of the inclination angle. 
   In a preferable embodiment, the exemplary method includes detecting a first horizontal angle θ L , calculating a first horizontal angle range of the head position with respect to the left rearview mirror, detecting a second horizontal angle θ R , and calculating a second horizontal angle range of the head position with respect to the right rearview mirror. 
   The first horizontal angle denotes an inclination angle of the left rearview mirror in a horizontal direction, and the first horizontal angle range is calculated on the basis of the first horizontal angle θ L . In the same way, the second horizontal angle denotes an inclination angle of the right rearview mirror in the horizontal direction, and the second horizontal angle range is calculated on the basis of the second horizontal angle θ R . 
   The first horizontal angle range preferably includes, toward a vehicle body from the rearward direction of the vehicle body, a range of 2θ L −Δθ L  to 2θ L +Δθ L . Also, the second horizontal angle range preferably includes, toward a vehicle body from the rearward direction of the vehicle body, a range of 2θ R −Δθ R  to 2θ R +Δθ R . Here, the angles Δθ L  and Δθ R  may be predetermined angles. 
   More preferably, the Δθ R  satisfies Δθ R =tan −1 (r/l), and the Δθ Lsatisfies  Δθ L =tan −1 (r/l). Here, r denotes a horizontal distance between the vehicle body and a center of the rearview mirror, and l denotes a horizontal distance between an end of the vehicle body and a center of the rearview mirror. 
   In a further embodiment, the method further includes detecting a first vertical angle φ L , calculating a first vertical angle range of the head position with respect to the left rearview mirror, detecting a second vertical angle φ R , and calculating a second vertical angle range of the head position with respect to the right rearview mirror. 
   Here, the first vertical angle denotes an inclination angle of the left rearview mirror in a vertical direction, and the first vertical angle range is calculated on the basis of the first vertical angle φ L . In the same way, the second vertical angle denotes an inclination angle of the right rearview mirror in a vertical direction, and the second vertical angle range is calculated on the basis of the second vertical angle φ R . 
   It is further preferable that, upward from a horizontal plane of a vehicle body, the first vertical angle range includes a range of φ L +Δφ L1  to φ L +Δφ L2 , and the second vertical angle range includes a range of φ R +Δφ R1  to φ R +Δφ R2 . Here, the angles Δφ L1 , Δφ L2 , Δφ R1 , and Δφ R2  may be predetermined angles. 
   In another exemplary method of the present invention (e.g., a method without including steps relating to horizontal angles), the method may include detecting a first vertical angle φ L , calculating a first vertical angle range of the head position with respect to the left rearview mirror, detecting a second vertical angle φ R , and calculating a second vertical angle range of the head position with respect to the right rearview mirror. 
   Here, the first vertical angle may denote an inclination angle of the left rearview mirror in a vertical direction, and the first vertical angle range may be calculated on the basis of the first vertical angle φ L . In the same way, the second vertical angle denotes an inclination angle of the right rearview mirror in a vertical direction, and the second vertical angle range may be calculated on the basis of the second vertical angle φ R . 
   As described above, it may be further preferable that upward from a horizontal plane of a vehicle body, the first vertical angle range includes a range of φ L +Δφ L1  to φ L +Δφ L2 , and the second vertical angle range includes a range of φ R +Δφ R1  to φ R +Δφ R2 . Here, the angles Δφ L1 , Δφ L2 , Δφ R1 , and Δφ R2  may be predetermined angles. 
   In one exemplary embodiment of the present invention an apparatus may determine a head position of a vehicle driver, the vehicle being equipped with left and right rearview mirrors. 
   The exemplary apparatus includes a first horizontal angle detector for detecting a first horizontal angle θ L , a second horizontal angle detector for detecting a second horizontal angle θ R , and an electronic control unit (ECU) for calculating the head position of the driver on the basis of the first and second horizontal angles θ L  and θ R  that are detected at the first and second horizontal angle detectors respectively. 
   Here, the first horizontal angle denotes an inclination angle of the left rearview mirror in a horizontal direction, and the second horizontal angle denotes an inclination angle of the right rearview mirror in the horizontal direction. 
   The ECU detects the first horizontal angle θ L , and accordingly calculates, on the basis of the first horizontal angle θ L , a first horizontal angle range of the head position with respect to the left rearview mirror. The ECU also detects the second horizontal angle θ R , and accordingly calculates, on the basis of the second horizontal angle θ R , a second horizontal angle range of the head position with respect to the right rearview mirror. 
   The first horizontal angle range preferably includes, toward a vehicle body from the rearward direction of the vehicle body, a range of 2θ L −Δθ L  to 2θ L +Δθ L . Also, the second horizontal angle range preferably includes, toward a vehicle body from the rearward direction of the vehicle body, a range of 2θ R −Δθ R  to 2θ R +Δθ R . Here, the angles Δθ L  and Δθ R  may be predetermined angles. 
   More preferably, the Δθ R  satisfies Δθ R =tan −1 (r/l), and the Δθ Lsatisfies  Δθ L =tan −1 (r/l). Here, r denotes a horizontal distance between the vehicle body and a center of the rearview mirror, and l denotes a horizontal distance between a rear end of the vehicle body and a center of the rearview mirror. 
   In a further embodiment, the apparatus further includes a first vertical angle detector for detecting a first vertical angle φ L  and a second vertical angle detector for detecting a second vertical angle φ R . Here, the first vertical angle denotes an inclination angle of the left rearview mirror in a vertical direction, and the second vertical angle denotes an inclination angle of the right rearview mirror in a vertical direction, 
   In this case, the electronic control unit further detects the first vertical angle φ L , and accordingly calculates, on the basis of the first vertical angle φ L , a first vertical angle range of the head position with respect to the left rearview mirror. In addition, the electronic control unit further detects the second vertical angle φ R , and accordingly calculates, on the basis of the second vertical angle φ R , a second vertical angle range of the head position with respect to the right rearview mirror. 
   It is further preferable that, upward from a horizontal plane of a vehicle body, the first vertical angle range includes a range of φ L +Δφ L1  to φ L +Δφ L2 , and the second vertical angle range includes a range of φ R +Δθ R1  to φ R +Δφ R2 . Here, the angles Δθ L1 , Δφ L2 , Δφ R1 , and Δφ R2  may be predetermined angles. 
   In another exemplary embodiment of the present invention (e.g., an apparatus without including devices and/or steps relating to horizontal angles), the apparatus may include a first vertical angle detector for detecting a first vertical angle φ L , a second vertical angle detector for detecting a second vertical angle φ R , and an electronic control unit (ECU) for calculating the head position of the driver on the basis of the first and second vertical angles φ L  and φ R  that are detected at the first and second vertical angle detectors respectively. Here, the first vertical angle denotes an inclination angle of the left rearview mirror in a vertical direction, and the second vertical angle denotes an inclination angle of the right rearview mirror in a vertical direction. 
   The ECU detects the first vertical angle φ L , and accordingly calculates, on the basis of the first vertical angle φ L , a first vertical angle range of the head position with respect to the left rearview mirror. The ECU also detects a second vertical angle φ R , and accordingly calculates, on the basis of the second vertical angle φ R , a second vertical angle range of the head position with respect to the right rearview mirror. 
   As described above, it is further preferable that upward from a horizontal plane of a vehicle body, the first vertical angle range includes a range of φ L +Δφ L1  to φ L +Δφ L2 , and the second vertical angle range includes a range of φ R +Δφ R1  to φ R +Δφ R2 . Here, the angles Δφ L1 , Δφ L2 , Δφ R1 , and Δφ R2  may be predetermined angles. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a block diagram of an apparatus for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention; 
       FIG. 2  is a drawing for showing a principle for determination of a horizontal head position of a vehicle driver according to a preferred embodiment of the present invention; 
       FIG. 3  is a drawing for showing a principle for determination of a vertical head position of a vehicle driver according to an exemplary embodiment of the present invention; and 
       FIG. 4  is a flowchart showing a method for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
     FIG. 1  is a block diagram of an apparatus for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention. 
   An apparatus according to an exemplary embodiment of the present invention is an apparatus for determining a head position of a driver of a vehicle, wherein the vehicle is provided with a left rearview mirror  210  and a right rearview mirror  220  (refer to FIG.  2  and FIG.  3 ). 
   As shown in  FIG. 1 , an apparatus for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention includes: a first horizontal angle detector  110  for detecting a first horizontal angle θ L , the first horizontal angle θ L  being an inclination angle of the left rearview mirror  210  in a horizontal direction; a first vertical angle detector  120  for detecting a first vertical angle φ L , the first vertical angle φ L  being an inclination angle of the left rearview mirror  210  in a vertical direction; a second horizontal angle detector  130  for detecting a second horizontal angle θ R , the second horizontal angle θ R  being an inclination angle of the right rearview mirror  220  in the horizontal direction; a second vertical angle detector  140  for detecting a second vertical angle φ R , the second vertical angle φ R  being an inclination angle of the right rearview mirror  220  in a vertical direction; and an electronic control unit (ECU)  150  for calculating the head position of the driver on the basis of the first and second horizontal angles θ L  and θ R  and the first and second vertical angles φ L  and φ R . 
   The first and second horizontal angles θ L  and θ R  are respectively detected at the first and second horizontal angle detectors, and the first and second vertical angles φ L  and φ R  are respectively detected at the first and second vertical angle detectors. 
   The first and second horizontal angle detectors  110  and  130  and the first and second vertical angle detectors  120  and  140  may be similar to detectors are already known and used in the related art, e.g., in an Integrated Memory Seat (IMS) system. 
   In addition, an exemplary embodiment of the present invention, the apparatus may not require additional detectors/components for a vehicle that is equipped with such an IMS system, since such angle detectors  110 ,  130 ,  120 , and  140  are already adopted therein. 
   The first horizontal and vertical angle detectors  110  and  120  may be integrally formed as a unit assembly and mounted at the left rearview mirror  210 . In addition, the second horizontal and vertical angle detectors  130  and  140  may also be integrally formed as a unit assembly and mounted at the right rearview mirror  220 . 
   The ECU  150  may be realized by one or more processors activated by predetermined software, and the predetermined software can be programmed to perform each step of a method for determining a head position of a vehicle driver according to an exemplary embodiment of this invention, which will be described in detail. 
   Prior to a detailed description of a method for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention, a principle by which a head position of a vehicle driver can be determined on the basis of output values of the angle detectors  110 ,  130 ,  120 , and  140  according to an exemplary embodiment of the present invention is firstly described hereinafter. 
     FIG. 2  is a drawing for showing a principle for determination of a horizontal head position of the vehicle driver according to an exemplary embodiment of the present invention, and such principle will now be described with reference to the drawing. 
   As shown to the left of  FIG. 2 , a vehicle body coordinate system may be defined by an x-coordinate χ V  and a y-coordinate γ V . The x-coordinate χ V  denotes a distance, from a center of the left rearview mirror  210 , in an exact rearward direction of the vehicle. The y-coordinate γ V  denotes a distance, from a center of the left rearview mirror  210 , to a vehicle body  200 . Such x- and y-coordinates are only an exemplary way of defining a vehicle body coordinate system, and a different vehicle body coordinate system may be used. 
   A mirror coordinate system, i.e., a coordinate system with respect to the mirror  210 , may be defined by an x-coordinate χ M  and a y-coordinate γ M . The x-coordinate χ M  denotes a distance, from the center of the left rearview mirror  210 , in a normal direction of the mirror surface. The y-coordinate γ V  denotes a distance, from a center of the left rearview mirror  210 , in a tangential direction of the mirror surface. Such x- and y-coordinates are only an exemplary way of defining a mirror coordinate system, and a different mirror coordinate system may be used. 
   In  FIG. 2 , viewing lines of a driver are shown as dotted lines. 
   Usually a driver sets a rearview mirror to an angular position that can secure a rearview by merely turning his/her head. Accordingly, a minimal portion of the vehicle body  200  is usually found in a view in the mirror. A viewing line  1  of the driver, showing such a state of viewing, is directed rearward and inclined to the vehicle body  200  by a predetermined angle Δθ L  with respect to the exact rearward direction χ V . 
   To the contrary, a viewing line  2  inclined outward of the vehicle body  200  forms the predetermined angle Δθ L  with the exact rearward direction χ V . 
   The predetermined angle Δθ L  depends on specifications of the left rearview mirror  210  and the vehicle body  200 . In more detail, with r denoting a horizontal distance between the vehicle body and a center of the rearview mirror and l denoting a horizontal distance between a rear end of the vehicle body and a center of the rearview mirror in  FIG. 2 , a relationship of Δθ L =tan −1 (r/l) is satisfied. 
   A position of the left rearview mirror  210  may be converted to the head position of the driver as follows. 
   An angle of an incident viewing line  1  corresponding to the reflection line of the viewing line  3  can be calculated, in the vehicle body coordinate system, on the basis of a horizontal inclination angle θ L  of the left rearview mirror  210  and the angle Δθ L  of the viewing line  1  inclined with respect to the vehicle body coordinate χ V . In more detail, an inclination angle by which the viewing line  1  is inclined to the vehicle body  200  from the exact rearward direction χ V  is calculated as 2θ L −Δθ L , i.e., 2(θ L −Δθ L )+Δθ L . 
   An angle of an incident viewing line  2  corresponding to the reflection line of the viewing line  4  can be calculated, in the vehicle body coordinate system, on the basis of a horizontal inclination angle θ L  of the left rearview mirror  210  and the angle Δθ L  of the viewing line  2  inclined with respect to the vehicle body coordinate χ V . In more detail, an inclination angle by which the viewing line  2  is inclined to the vehicle body  200  from the exact rearward direction χ V  is calculated as 2θ L +Δθ L , i.e., 2(θ L +Δθ L )−Δθ L . 
   Therefore, on the basis of the predetermined angle Δθ L  and horizontal inclination angle θ L  of the left rearview mirror  210 , the head position of the driver  215  with respect to the left rearview mirror  210  may be concluded to lie within a range of 2θ L −Δθ L  to 2θ L +Δθ L  toward the vehicle body  200  from the rearward direction χ V  of the vehicle body. 
   Using the relationship Δθ L =tan −1 (r/l), such a range may be converted to a range of 2θ L −tan −1 (r/l) to 2θ L +tan −1 (r/l). 
   The same principle can be applied to the right rearview mirror  220 . Therefore, on the basis of a predetermined angle Δθ R  and horizontal inclination angle θ R  of the right rearview mirror  220 , the head position of the driver with respect to the right rearview mirror  220  may be concluded to lie within a range of 2θ R −Δθ R  to 2θ R +Δθ R  toward the vehicle body  200  from the rearward direction χ V  of the vehicle body. 
   Regarding the right rearview mirror  220 , a relationship of Δθ R =tan −1 (r/l) is satisfied, and using this relationship, such a range may be converted to a range of 2θ R −tan −1 (r/l) to 2θ R +tan −1 (r/l). 
   Therefore, summarizing the principles regarding the left rearview mirror  210  and the right rearview mirror  220 , the horizontal head position of the vehicle driver can be determined to lie within a range of 2θ L −Δθ L  to 2θ L +Δθ L  with respect to the left rearview mirror  210 , and within a range of 2θ R −Δθ R  to 2θ R +Δθ R  with respect to the right rearview mirror  220 . Both the horizontal angle ranges are measured toward a vehicle body from the rearward direction of the vehicle body. 
   Therefore, in a horizontal plane, the head position of the vehicle driver may be determined to lie within a range including a hatched area  280  shown in FIG.  2 . 
     FIG. 3  is a drawing for showing a principle for determination of a vertical head position of the vehicle driver according to an exemplary embodiment of the present invention.  FIG. 3  shows the left side of the vehicle and the left rearview mirror  210 . 
   A principle for determining the vertical head position of a driver on the basis of a vertical inclination angle of the left rearview mirror  210  is hereinafter described with reference to FIG.  3 . 
   In  FIG. 3 , Δφ L1  denotes an angle between a viewing line of the driver and a normal line of the rearview mirror when an uppermost rearview is taken through the left rearview mirror  210 . Δφ L2  denotes an angle between a viewing line of the driver and a normal line of the rearview mirror when a lowermost rearview is taken through the left rearview mirror  210 . The normal line of the left rearview mirror  210  lies on the mirror coordinate χ M . 
   The normal line of the left rearview mirror  210  is inclined upward by an angle φ L  from the exact rearward direction χ V . 
   Therefore, when the uppermost view is taken through the left rearview mirror  210 , the viewing line  300  of the driver is inclined upward by φ L +Δφ L1  from the exact rearward direction χ V  of the vehicle body. In the same way, when the lowermost view is taken through the left rearview mirror  210 , the viewing line  305  of the driver is inclined upward by φ L +Δφ L2  from the exact rearward direction χ V  of the vehicle body 
   Such a range of the viewing line may be converted to a vertical head position of the driver with respect to the left rearview mirror  210 . In more detail, the vertical head position of the driver may be determined to lie within a range of φ L +Δφ L1  to φ L +Δφ L2  with respect to the left rearview mirror  210 . 
   When the values of Δφ L1  and Δφ L2  are predetermined, the vertical head position of the driver can be found from the vertical inclination angle φ L  of the left rearview mirror  210 . Such angles Δφ L1  and Δφ L2  can be obviously predetermined by collecting data for various drivers and statistically processing the collected data, which does not require undue experiment. 
   The same principle as described in connection with the left rearview mirror  210  can be applied to the right rearview mirror  220 . 
   Therefore, with φ R  denoting an angle by which a normal line of the right rearview mirror  220  is inclined upward from the exact rearward direction χ V , the vertical head position of the driver can be understood to lie within a range of φ R +Δφ R1  to φ R +Δφ R2  with respect to the right rearview mirror  220 . 
   When the values of Δφ R1  and Δφ R2  are predetermined, the vertical head position of the driver can be found from the vertical inclination angle φ R  of the left rearview mirror  210 . Such angles Δφ R1  and Δφ R2  can be predetermined by collecting data for various drivers and statistically processing the collected data, which does not require undue experiment. 
   With understanding of such basic principles, a method for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention is hereinafter described in detail. 
     FIG. 4  is a flowchart showing a method for determining a head position of a vehicle driver according to an exemplary embodiment of the present invention. 
   As shown in  FIG. 4 , at step S 410 , the ECU  150  firstly detects a first horizontal angle θ L , which is an horizontal inclination angle of the left rearview mirror  210 . 
   Subsequently at step S 415 , the ECU  150  calculates, on the basis of the first horizontal angle θ L , a first horizontal angle range of the head position with respect to the left rearview mirror. At the step of S 415 , the first horizontal angle range is determined so as to include a range of 2θ L −tan −1 (r/l) to 2θ L +tan −1 (r/l) toward a vehicle body from the rearward direction of the vehicle body. Here, r denotes a horizontal distance between the vehicle body and a center of the rearview mirror, and l denotes a horizontal distance between a rear end of the vehicle body and a center of the rearview mirror: 
   In addition, at step S 420 , the ECU  150  detects a second horizontal angle θ R , which is a horizontal inclination angle of the right rearview mirror  220 . 
   Subsequently at step S 425 , the ECU  150  calculates, on the basis of the second horizontal angle θ R , a second horizontal angle range of the head position with respect to the right rearview mirror. At the step S 425 , the second horizontal angle range is determined so as to include a range of 2θ R −tan −1 (r/l) to 2θ R +tan −1 (r/l) toward a vehicle body from the rearward direction of the vehicle body. 
   In addition, at step S 430 , the ECU  150  detects a first vertical angle φ L , which is a vertical inclination angle of the left rearview mirror  210 . 
   Subsequently at step S 435 , the ECU  150  calculates, on the basis of the first vertical angle φ L , a first vertical angle range of the head position with respect to the left rearview mirror. At the step of S 435 , the first vertical angle range is determined so as to include a range of φ L +Δφ L1  to φ L +Δφ L2  upward from a horizontal plane of the vehicle body. Here, Δφ L1  and Δφ L2  denote predetermined angles. 
   Subsequently at step S 440 , the ECU  150  detects a second vertical angle φ R , which is a vertical inclination angle of the right rearview mirror  220 . 
   At step S 445 , the ECU  150  calculates, on the basis of the second vertical angle φ R , a second vertical angle range of the head position with respect to the right rearview mirror. At the step of S 445 , the second vertical angle range is determined so as to include a range of φ R +Δφ R1  to φ R +Δφ R2  upward from a horizontal plane of the vehicle body. Here, Δφ R1  and Δφ R2  denote predetermined angles. 
   After calculating the first and second horizontal angle ranges and the first and second vertical angle ranges as above, the ECU  150  determines, at step S 450 , that the head position of the driver lies within the first and second horizontal angle ranges and also within the first and second vertical angle ranges. 
   According to another embodiment of the present invention, the head position of a vehicle driver may be determined with enhanced accuracy and/or precision using devices already adoptable to a usual integrated memory seat (IMS) system, without additionally requiring costly devices such as a stereo camera. 
   Therefore, an exemplary embodiment of the present invention also contributes to improvement of accuracy and/or precision of an application apparatus, e.g., an intelligent air bag system, that functions based on the head position of a vehicle driver. 
   While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.