Patent Publication Number: US-2022212674-A1

Title: Alighting assistance device and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Japanese patent application JP 2021-001406, filed Jan. 7, 2021, the entire contents of which being incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to an alighting assistance device and an alighting assistance method that assist an occupant in alighting from a driver seat. 
     BACKGROUND ART 
     In a case where an occupant alights from a driver seat, his/her body making an alighting action may interfere with a steering wheel, the driver seat, or the like, and the alighting action may be inhibited. Thus, a device has been known which assists an occupant in alighting from a driver seat in order to make alighting easy, and for example, a retraction action control apparatus for a vehicle seat is disclosed in Patent Literature 1. 
     The retraction action control apparatus for a vehicle seat which is disclosed in Patent Literature 1 is a retraction action control apparatus including a retraction action controller which detects an alighting timing and causes a foremost seat to automatically perform slide movement in a vehicle front-rear direction, in which in a case where a line which divides a portion between linear portions of a pillar front end and a pillar back end of center pillars arranged on door sides of the foremost seat into two equal parts, the linear portions resulting from removal of respective curvature portions of the pillar front end and the pillar back end, is referred to as pillar bisector, when the retraction action controller detects the alighting timing, the retraction action controller performs a retraction action control process such that a reclining rotation center portion of the foremost seat as seen from a vehicle side direction performs slide movement from a driving posture seat position at a time when the alighting timing is detected to a retracted seat position on a vehicle front side including positions overlapping with the pillar bisector. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] Japanese Patent Laid-Open No. 2017-171175 
     SUMMARY 
     Problems to be Solved 
     A retraction action control apparatus for a vehicle seat which is disclosed in above Patent Literature 1 detects an alighting timing and causes a foremost seat to automatically perform slide movement to a retracted seat position, and a foot side space of an occupant is thus expanded. This makes alighting of the occupant easy. However, because an alighting action is an action of a whole body, consideration of only a foot side may be insufficient. 
     The present disclosure has been made in consideration of the above circumstance, and other problems, and an object thereof is to provide an alighting assistance device and an alighting assistance method that can make alighting easier. 
     Means for Solving the Problems 
     As a result of various studies, the inventor has found that the above object is achieved by the present disclosure described below. That is, an alighting assistance device according to one aspect of the present disclosure may be a device moving a driver seat rearward in a case where a determination is made that an occupant seated on the driver seat of a vehicle alights, the alighting assistance device including: a height change unit which changes a height of a steering wheel; a sitting height acquisition unit which acquires a sitting height of the occupant; and a height controller which controls the height change unit such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit is higher in the case where a determination is made that the occupant alights. 
     In a case where the occupant seated on the driver seat of the vehicle alights, when not only the driver seat moves rearward but also the steering wheel is lifted up, not only a foot side space of the occupant but also a space around an upper body of the occupant expands, and the occupant thus more easily alights. In a case where the occupant alights, the occupant may alight while raising his/her upper body by gripping the steering wheel. In this case, when the steering wheel is lifted up high, it is more difficult for the occupant to grip the steering wheel as his/her sitting height is higher. Because his/her arm bends at the elbow when he/she raises his/her upper body by gripping the steering wheel, it is difficult to apply a force to the arm. In the case where a determination is made that the occupant alights, the alighting assistance device controls the height change unit so as to change the height of the steering wheel such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit is higher. Thus, the occupant easily grips the steering wheel, and because his/her arm is stretched more (because the elbow more shallowly bends) when he/she raises his/her upper body by gripping the steering wheel, it becomes easy to apply a force to the arm. Consequently, the alighting assistance device can make alighting easier. 
     In another aspect, in the above-described alighting assistance device, the sitting height acquisition unit includes an input unit which inputs a body height of the occupant, a measuring unit which measures an eye level of the occupant seated on the driver seat of the vehicle, and a sitting height processing unit which obtains the sitting height of the occupant based on the body height input to the input unit and the eye level measured by the measuring unit. 
     It is possible to obtain a so-called hip point based on the eye level, and it is possible to obtain the sitting height based on the body height and the hip point. The alighting assistance device includes the input unit, the measuring unit, and the sitting height processing unit and can thus precisely acquire the sitting height by a simple procedure. 
     In another aspect, the alighting assistance device in those above descriptions further includes a body height acquisition unit which acquires a body height of the occupant, in which the height controller further controls the height change unit such that the height of the steering wheel becomes higher as the body height acquired by the body height acquisition unit is lower in a case where the sitting height is the same. In the above-described alighting assistance device, the body height acquisition unit optionally acquires a height (a position in an up-down direction, a lift amount) of a seat surface of the driver seat. In the above-described alighting assistance device, the body height acquisition unit is optionally the input unit of the sitting height acquisition unit (the body height acquisition unit is optionally used also as the input unit of the sitting height acquisition unit). 
     A small occupant whose body height is relatively low often sets the seat surface high and positions the position of the driver seat on a front side compared to a large occupant whose body height is relatively high. Thus, when the height of the steering wheel is set low, a space around the upper body of the occupant becomes narrow for the small occupant whose body height is relatively low. In a case where the sitting height is the same, the alighting assistance device controls the height change unit so as to change the height of the steering wheel such that the height of the steering wheel becomes higher as the body height acquired by the body height acquisition unit is lower. Thus, the space around the upper body becomes wider for the small occupant, and the occupant more easily alights. Consequently, the alighting assistance device can make alighting easier. 
     In another aspect, the alighting assistance device in those above descriptions further includes an arm length acquisition unit which acquires an arm length of the occupant, in which in a case where the driver seat is moved rearward, a movement amount is increased as the arm length acquired by the arm length acquisition unit is longer. The above-described alighting assistance device optionally further includes a position change unit which changes a position of the driver seat in a front-rear direction and a position controller which controls the position change unit such that the position of the driver seat comes to a rear side as the arm length acquired by the arm length acquisition unit is longer in the case where a determination is made that the occupant alights. The above-described alighting assistance device optionally further includes a second input unit which inputs the body height of the occupant, and the arm length acquisition unit optionally obtains the arm length of the occupant based on the body height input to the second input unit and the sitting height acquired by the sitting height acquisition unit. 
     Such an alighting assistance device makes a rearward movement amount of the driver seat larger (more) as the arm length is longer. Thus, even the occupant whose arm length is relatively long easily grips the steering wheel, and because his/her arm is stretched more (because the elbow more shallowly bends) when he/she raises his/her upper body by gripping the steering wheel, it becomes easy to apply a force to the arm. Consequently, the alighting assistance device can make alighting easier. 
     In another aspect, in the alighting assistance device in those above descriptions, after the driver seat moves rearward, the height controller controls the height change unit. The above-described alighting assistance device optionally further includes a position change unit which changes a position of the driver seat in a front-rear direction and a position controller which controls the position change unit such that the position of the driver seat comes to a rear side in the case where a determination is made that the occupant alights, and the height controller optionally controls the height change unit after the position controller controls the position change unit. 
     Such an alighting assistance device moves the driver seat rearward and thereafter lifts up the steering wheel. Thus, because the occupant has a wider clearance from the steering wheel (because the distance between the steering wheel and the occupant becomes longer) when the steering wheel is lifted up, the occupant can be given a sense of security about a lifting action of the steering wheel. 
     An alighting assistance method according to another aspect of the present disclosure is a method moving a driver seat rearward in a case where a determination is made that an occupant seated on the driver seat of a vehicle alights, the alighting assistance method including: a sitting height acquisition step of acquiring a sitting height of the occupant; and a height control step of changing the height of the steering wheel such that the height of the steering wheel becomes lower as the sitting height acquired in the sitting height acquisition step is higher in the case where a determination is made that the occupant alights. 
     In such an alighting assistance method, in the case where a determination is made that the occupant alights, the height of the steering wheel is changed such that the height of the steering wheel becomes lower as the sitting height acquired in the sitting height acquisition step is higher. Thus, the occupant easily grips the steering wheel, and because his/her arm is stretched more (because the elbow more shallowly bends) when he/she raises his/her upper body by gripping the steering wheel, it becomes easy to apply a force to the arm. Consequently, the alighting assistance method can make alighting easier. 
     Advantageous Effect of Disclosure 
     An alighting assistance device and an alighting assistance method according to the present disclosure can make alighting easier. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of an alighting assistance device according to one embodiment of the present disclosure. 
         FIG. 2  is a diagram for explaining a second input unit of the alighting assistance device according to one embodiment of the present disclosure. 
         FIG. 3  is a diagram illustrating, as one example, a sitting height conversion table which is stored in the alighting assistance device according to one embodiment of the present disclosure. 
         FIG. 4  is a diagram illustrating, as one example, steering wheel height information which is stored in the alighting assistance device according to one embodiment of the present disclosure. 
         FIG. 5  is a flowchart illustrating an action of the alighting assistance device about assistance for alighting according to one embodiment of the present disclosure. 
         FIG. 6  is a diagram for explaining movement of a driver seat and a change in a height of a steering wheel in a case of alighting according to one embodiment of the present disclosure. 
     
    
    
     MODE FOR CARRYING OUT THE DISCLOSURE 
     One or plural embodiments of the present disclosure will hereinafter be described with reference to drawings. However, the scope of the disclosure is not limited to the disclosed embodiments. Note that configurations provided with the same reference characters in the drawings indicate the same configurations, and description thereof will appropriately be omitted. In the present specification, in a case where configurations are referred to as generic terms, those will be denoted by reference characters without additional characters. In a case where an individual configuration is indicated, the configuration will be denoted by a reference character with an additional character. 
     An alighting assistance device in one embodiment is a device being installed in a vehicle and moving a driver seat rearward in a case where a determination is made that an occupant seated on the driver seat of a vehicle alights. This alighting assistance device may include: a height change unit which changes a height of a steering wheel; a sitting height acquisition unit which acquires a sitting height of the occupant; and a height controller which controls the height change unit such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit is higher in the case where a determination is made that the occupant alights. In the following, such an alighting assistance device will more specifically be described. 
       FIG. 1  is a block diagram illustrating a configuration of the alighting assistance device in one embodiment of the present disclosure.  FIG. 2  is a diagram for explaining a second input unit of the alighting assistance device according to one embodiment of the present disclosure.  FIG. 2A  is a perspective view, and  FIG. 2B  is a side view.  FIG. 3  is a diagram illustrating, as one example, a sitting height conversion table which is stored in the alighting assistance device according to one embodiment of the present disclosure.  FIG. 4  is a diagram illustrating, as one example, steering wheel height information which is stored in the alighting assistance device according to one embodiment of the present disclosure. The steering wheel height information indicates the correspondence relationship between the sitting height and the height of the steering wheel, the horizontal axis of  FIG. 4  represents the sitting height, and the vertical axis represents the height of the steering wheel. 
     Here, in the following descriptions, the terms denoting directions such as “front”, “rear”, “right”, “left”, “up”, “down”, and so forth indicate the directions of the vehicle in a case where a moving direction in forward traveling of the vehicle is set as “front”. 
     As illustrated in  FIG. 1 , for example, an alighting assistance device D in one embodiment includes an input unit or inputter  1 , a sitting height acquisition unit or acquirer  2 , a control processing unit or processor  3 , a storage unit  4 , a seat driving unit  5 , and a steering device  6 . In the example illustrated in  FIG. 1 , the alighting assistance device D may further include a head- up display (HUD)  7 . 
     The seat driving unit  5  may be a device which is connected with the control processing unit  3  and moves a posture of a driver seat DS of the vehicle in accordance with control by the control processing unit  3 . As illustrated in  FIG. 2 , for example, the driver seat (a seat for a driver) DS includes a seat cushion DSa which forms a seat surface, a seat back DSb which, at its lower end (one end), is mounted on a back end (other end) of the seat cushion DSa and serves as a backrest, and a pillow-like headrest DSc which is mounted on an upper end (other end) of the seat back DSb. The seat driving unit  5  is incorporated in this driver seat DS. In the present embodiment, the seat driving unit  5  includes an electrically driven reclining mechanism  51  which adjust an inclination of the seat back DSb, an electrically driven slide mechanism  52  which adjusts a position (front-rear position) of the seat cushion DSa in a front-rear direction, an electrically driven lift mechanism  53  which adjusts a position (up-down position, height) of the seat cushion DSa in an up-down direction, and an electrically driven tilt mechanism  54  which adjusts a height of a front end (one end) of the seat cushion DSa in the up-down direction and thereby adjusts an inclination of the seat surface of the seat cushion DSa, for example. Such electrically motorized reclining mechanism  51 , slide mechanism  52 , lift mechanism  53 , and tilt mechanism  54  are configured by known usual means and are disclosed in Japanese Patent Laid-Open No. 2011-79472, Japanese Patent Laid-Open No. 2019-172016, Japanese Patent Laid-Open No. 2006-218882, and so forth, for example. The inclination of the seat back DSb (an angle of the seat back DSb) is expressed by an angle formed by an extension direction extending in a general height direction of a seat back DSb with respect to a horizontal plane (for example, a floor surface or the like of the vehicle) which has the up-down direction as a normal line. The inclination of the seat surface is expressed by the angle formed between the horizontal plane and the seat surface. 
     The input unit  1  may be a device which is connected with the control processing unit  3  and inputs an instruction to move the posture of the driver seat DS (an instruction to adjust the posture of the driver seat DS), for example, and input various kinds of data such as a body height of an occupant seated on the driver seat DS, for example, the various kinds of data being necessary for causing the alighting assistance device D to act. In the present embodiment, as illustrated in  FIG. 1  and  FIG. 2 , the input unit  1  includes a first input unit  11  and a second input unit  12 . 
     The first input unit  11  may be a device for inputting various kinds of data such as the body height of the occupant. The first input unit  11  may be configured to include plural switches such as keys in a numeric keypad, for example, but in the present embodiment, the first input unit  11  is a columnar dial switch which is rotatable around an axis and is capable of being pushed in an axis direction and is arranged in a center console partitioning the driver seat from a passenger seat in a vehicle cabin, for example. As for this dial switch, when the dial switch is rotated, a numerical value displayed in the HUD  7  (or a center display (not illustrated)) increases or decreases in accordance with a rotational direction (for example, the numerical value increases by clockwise rotation, and the numerical value decreases by counterclockwise rotation), and when the dial switch is pushed, the numerical value displayed in the HUD  7  (or the center display) is confirmed and is input to the alighting assistance device D. 
     The second input unit  12  may be a device for inputting the instruction to move the posture of the driver seat DS. In the present embodiment, for example, as illustrated in  FIG. 2 , the second input unit  12  includes a seat back switch (SB switch)  121  for inputting an instruction to adjust the inclination of the seat back DSb and a seat cushion switch (SC switch)  122  for inputting respective instructions to adjust the front-rear position, the up-down position, and the inclination of the seat surface in the seat cushion DSa and is disposed on a side surface of a lower portion of the driver seat DS such that the SB switch  121  and the SC switch  122  form a similar shape to the shape of the driver seat DS in a side view. The SB switch  121  is configured to be inclined in a general front-rear direction with respect to a lower end portion as a rotation axis. The SC switch  122  is configured such that a front end and a back end are inclined in a general up-down direction with respect to a general central portion as a rotation axis and is further configured to move in the front-rear direction. 
     The sitting height acquisition unit or acquirer  2  may be a device which is connected with the control processing unit  3  and acquires the sitting height of the occupant seated on the driver seat DS in accordance with control by the control processing unit  3 . The sitting height acquisition unit  2  may be the first input unit  11  (may also be used as the first input unit  11 ), for example. Although the occupant may input his/her own sitting height by manual inputting from the first input unit  11 , because the occupant hardly knows his/her own sitting height, in the present embodiment, the sitting height acquisition unit  2  includes an input unit for inputting the body height of the occupant, a measuring unit  21 , and a sitting height processing unit  22  ( 35 ). 
     This input unit for inputting the body height of the occupant may be provided as a third input unit to the input unit  1  separately from the first and second input units  11  and  12  but is provided as the first input unit  11  (used also as the first input unit  11 ) in the present embodiment. 
     The measuring unit or measurer  21  may be a device which measures an eye level of the occupant seated on the driver seat DS of the vehicle. The eye level is measured from a predetermined reference position (height), for example, such as a position (height) of the floor surface of the vehicle, a position (height) of the seat surface of the seat cushion DSa, or a position (height) of a so-called hip point corresponding to the posture of the driver seat DS. In the present embodiment, as one example, the eye level is measured from the position (height) of the seat cushion DSa (a position of a reference point of a seat). In the present embodiment, the measuring unit  21  includes an eye level data acquisition unit  211  and an eye level processing unit  34  ( 212 ), for example. The eye level data acquisition unit  211  is a device which is connected with the control processing unit  3  and acquires predetermined data for measuring the eye level of the occupant seated on the driver seat DS in accordance with control by the control processing unit  3 . In the present embodiment, the eye level processing unit  212  ( 34 ) is functionally configured by the control processing unit  3  by execution of control processing programs described later and obtains the eye level of the occupant by processing the predetermined data acquired by the eye level data acquisition unit  211 . 
     For example, the eye level data acquisition unit or acquirer  211  includes a camera which generates an image of the occupant seated on the driver seat DS and a distance meter which measures the distance to the occupant seated on the driver seat DS and is arranged on a lateral side of the center display (not illustrated), for example. The eye level processing unit  212  ( 34 ) obtains the eye level of the occupant based on the image of the occupant which is generated by the camera and the distance to the occupant which is measured by the distance meter. The distance meter measures the distance by so-called TOF (time of flight) based on a time between a transmission timing of an infrared light pulse and a reception timing of a reflected light, the time being obtained by transmitting the infrared light pulse and then receiving the reflected light of the infrared light pulse which is reflected by the occupant, for example. The eye level processing unit  212  ( 34 ) obtains a pixel position of a white portion of the eye by extracting the white portion of the eye by image processing such as a white filter from a predetermined image region, which is in advance defined and which the face of the occupant is assumed to enter, in the image of the occupant which is generated by the camera, obtains an actual length of a subject which enters one pixel from the distance to the occupant which is measured by the distance meter, an optical characteristic (for example, an image-capturing magnification or the like) of an image-capturing optical system of the camera, and so forth, and obtains the eye level of the occupant from an actual height of a lower end portion of the image generated by the camera, the pixel position of the white portion of the eye, and the actual length of the subject which enters one pixel. Note that the actual height of the lower end portion of the image generated by the camera is in advance obtained from optical characteristics of the image-capturing optical system in the camera, an image-capturing direction (optical axis direction), and so forth and is stored in the storage unit  4 . The predetermined image region is in advance obtained from an arrangement position of the camera, an arrangement position of the driver seat DS, the optical characteristics of the image-capturing optical system of the camera, its image-capturing direction, and so forth, for example, and is stored in the storage unit  4 . Alternatively, for example, the eye level data acquisition unit  211  includes a so-called stereo camera instead of the camera and the distance meter. An image of the occupant seated on the driver seat DS is generated by the stereo camera, and the distance to the occupant seated on the driver seat DS is measured by the stereo camera. Alternatively, for example, the eye level data acquisition unit  211  includes a mark whose size (dimensions) is known and a camera which generates an image of the occupant seated on the driver seat DS and the mark. The mark is provided to a part whose image can be captured by the camera even in a case where the occupant is seated on the driver seat DS, for example, a side portion of the headrest DSc, and the camera is arranged to capture an image of the face of the occupant and the mark from an obliquely front side. The eye level processing unit  212  ( 34 ) extracts each of the white portion of the eye and the mark, by image processing, from a predetermined image region in an image of the occupant which is generated by the camera, thereby obtains the pixel position of the white portion of the eye and the number of pixels which the mark enters, obtains the actual length of the subject which enters one pixel from the number of pixels which the mark enters and the size of the mark, and obtains the eye level of the occupant from the actual height of a lower end portion of the image generated by the camera, the pixel position of the white portion of the eye, and the actual length of the subject which enters one pixel. 
     In the present embodiment, the sitting height processing unit or processor  22  ( 35 ) may be functionally configured by the control processing unit  3  by execution of the control processing programs described later and obtains the sitting height of the occupant based on the body height input to the first input unit  11  and the eye level measured by the measuring unit  21 . The sitting height processing unit  22  ( 35 ) will further be described later. 
     The steering device  6  may be a mechanism for steering steered wheels. The steering device  6  may include a steering wheel  61 , a steering shaft  63  which is coupled with the steering wheel  61 , a steering angle driving mechanism  64  which gives a steering angle to the steered wheels in accordance with a rotation angle of steering shaft provided to the steering shaft  63  by an operation of the steering wheel  61 , and a height change unit  62  which is connected with the control processing unit  3  and changes a height of the steering wheel  61  in accordance with control by the control processing unit  3 , for example. Optionally, for example, the height change unit  62  is a tilt mechanism which is connected with the control processing unit  3  and moves up and down the steering wheel  61  in an electrically driven manner in accordance with control by the control processing unit  3 , and this tilt mechanism changes a tilt angle of the steering shaft  63  and thereby moves up and down the steering wheel  61 , for example. In the present embodiment, the steering device  6  further includes a telescopic mechanism (not illustrated) which is connected with the control processing unit  3  and moves forward and rearward the steering wheel  61  in an electrically driven manner in accordance with control by the control processing unit  3 . Such electrically motorized tilt mechanism and telescopic mechanism are configured by known usual means and are disclosed in Japanese Patent Laid-Open No. 2020-19327, Japanese Patent Laid-Open No. 2019-23050, and so forth, for example. Note that the steering device  6  may include a rotation angle of steering shaft sensor which detects the rotation angle of steering shaft provided to the steering shaft  63  by an operation of the steering wheel  61 , and the steering angle driving mechanism  64  may be a mechanism which gives a steering angle to the steered wheels in accordance with a steering wheel detected by the rotation angle of steering shaft sensor. In such a case, for example, the steering shaft  63  is, at its one end, coupled with the steering wheel  61 , its other end is coupled with a so-called universal joint, and the steering wheel  61  is moved up and down by changing the tilt angle of the steering shaft  63  by the tilt mechanism. 
     The HUD  7  may be a device which is arranged in a dashboard in front of the driver seat DS, is connected with the control processing unit  3 , and displays predetermined information such as the body height of the occupant which is input by the first input unit  11 , for example, by projecting the predetermined information onto a transparent planar optical member such as a windshield, for example, in accordance with control by the control processing unit  3 . The HUD  7  is configured by known usual means and is disclosed in Japanese Patent Laid-Open No. 2015-161965, Japanese Patent Laid-Open No. 2019-166886, and so forth, for example. 
     The storage unit  4  may be circuitry which is connected with the control processing unit  3  and stores various kinds of predetermined programs and various kinds of predetermined data in accordance with control by the control processing unit  3 . The various kinds of predetermined programs include the control processing programs, for example. The control processing programs include a control program which respectively controls the units  1 ,  2 ,  4  to  7  of the alighting assistance device D in accordance with functions of those units, a seat control program which controls the seat driving unit  5 , a steering wheel control program which controls the tilt mechanism (one example of the height change unit  62 ) and the telescopic mechanism in the steering device  6  and thereby controls the position (the position in the up-down direction (height) and the position in the front-rear direction) of the steering wheel, an eye level processing program which processes the predetermined data acquired by the eye level data acquisition unit  211  and thereby obtains the eye level of the occupant, a sitting height processing program which obtains the sitting height of the occupant based on the body height of the occupant which is input to the first input unit  11  and the eye level measured by the measuring unit  21 , and so forth, for example. The various kinds of predetermined data include data necessary for executing those programs such as occupant information including the body height of the occupant, sitting height conversion information, and the steering wheel height information. Such a storage unit  4  includes a ROM (read-only memory) as a non-volatile storage element, an EEPROM (electrically erasable programmable read-only memory) as a rewritable non-volatile storage element, and so forth, for example. Furthermore, the storage unit  4  includes a RAM (random access memory) and so forth serving as a so-called working memory of the control processing unit  3 , which stores data and so forth generated during execution of the predetermined programs. The storage unit  4  functionally includes an occupant information storage unit  41 , a sitting height conversion information storage unit  42 , and a steering wheel height information storage unit  43 . 
     The occupant information storage unit  41  may store the occupant information. The occupant information is predetermined information about the occupant which includes the body height of the occupant. When the first input unit  11  accepts the body height of the occupant seated on the driver seat DS, a controller  31  of the control processing unit  3  stores the body height of the occupant in the occupant information storage unit  41 . Note that the occupant information storage unit  41  may store an identifier for specifying and identifying an occupant (occupant identifier) and the occupant information while associating those with each other. Accordingly, the occupant information for plural occupants can be stored. In this case, for example, after the occupant identifiers are displayed on the HUD  7  and the first input unit  11  accepts selection of the occupant identifier, the first input unit  11  may accept the body height of the occupant. 
     The sitting height conversion information storage unit  42  may store the sitting height conversion information. The sitting height conversion information is information for obtaining the sitting height based on the body height and the eye level. The sitting height conversion information may be a function formula for calculating the sitting height from the body height and the eye level, for example; however, in the present embodiment, the sitting height conversion information is a sitting height conversion table CT which is illustrated in  FIG. 3  and in which the body height, the eye level, and the sitting height are associated with each other, for example. This sitting height conversion table CT is a two-dimensional matrix-like table and includes a body height registration region CTa in which respective body heights of rows are registered, an eye level registration region CTb in which the respective heights of eyes of columns are registered, and a sitting height registration region CTc in which sitting heights are registered in a two-dimensional matrix manner. In this sitting height conversion table CT, roughly, a higher sitting height SH is registered at the same body height as the eye level is higher, and a higher sitting height SH is registered at the same eye level as the body height is higher. For example, SH 11 &lt;SH 126  holds at a body height of 150 [cm], and SH 11 &lt;SH 411  holds at an eye level of 76 [cm]. Also, SH 11 &lt;SH 4126  holds. In such a sitting height conversion table CT, the row is designated from the rows by the body height, the column is designated from the columns by the eye level, and the sitting height in the position where those designated row and column intersect with each other is thereby selected (retrieved, extracted) from the sitting heights which are registered in a two-dimensional matrix manner. Accordingly, the sitting height based on the body height and the eye level is obtained. 
     The steering wheel height information storage unit  43  may store the steering wheel height information. The steering wheel height information is information for obtaining the height of the steering wheel based on the sitting height. The steering wheel height information is set such that the height of the steering wheel becomes lower as the sitting height is higher. Furthermore, the steering wheel height information is set such that the height of the steering wheel becomes higher as the body height is lower in a case where the sitting height is the same. The steering wheel height information may be a table in which the sitting height and the height of the steering wheel are associated with each other, for example; however, in the present embodiment, the steering wheel height information is a function formula for calculating the height of the steering wheel from the sitting height. Optionally, in the present embodiment, for example, the steering wheel height information is each of function formulas Fα(SH) and Fβ(SH) of lines α and β illustrated in  FIG. 4 . The function formula Fα(SH) of the line α is for a large occupant whose body height is relatively high, Fα(SH)=HH 1  holds when SH&lt;SH 1 , and Fα(SH)=HH 1 −α×(SH−SH 1 ) holds when SH 1 ≤SH. A term SH denotes the sitting height, Fα(SH) denotes the height of the steering wheel in a case of the sitting height SH, HH 1  denotes a predetermined default height of the steering wheel which is in advance set, SH 1  denotes a predetermined sitting height which is in advance set, and −a denotes a slope and is in advance set (a&gt;0). The function formula Fβ(SH) of the line β is for a small occupant whose body height is relatively low, Fβ(SH)=HH 1  holds when SH&lt;SH 1 , and Fβ(SH)=HH 1 −b×(SH−SH 1 ) holds when SH 1 ≤SH. A term Fβ(SH) denotes the height of the steering wheel in a case of the sitting height SH, and −b denotes a slope and is in advance set (b&gt;0). In such a manner, the steering wheel height information Fα(SH) and Fβ(SH) is set such that in a case where the sitting height SH is shorter than SH 1 , the height of the steering wheel is a constant value HH 1 , and in a case where the sitting height SH is SH 1  or higher, the height of the steering wheel is lower than the constant value HH 1 . As described above, because the steering wheel height information is set such that the height of the steering wheel becomes higher as the body height is lower in a case where the sitting height is the same, a&gt;b&gt;0 (−a&lt;−b&lt;0) holds. The determination about whether the occupant is small or large is executed based on a lift amount by the lift mechanism  53  of the seat driving unit  5 , for example, and a threshold value (determination threshold value) for distinguishing whether the occupant is small or large is in advance set. In a case where the lift amount is the determination threshold value or larger, the occupant is determined to be a small occupant, and Fβ(SH) is used. In a case where the lift amount is smaller than the determination threshold value, the occupant is determined to be a large occupant, and Fα(SH) is used. Those HH 1 , SH 1 , a, b, and the determination threshold value are in advance and appropriately set from plural samples, for example. 
     Note that as for the determination about whether the occupant is small or large, for example, a threshold value (second determination threshold value) for distinguishing those may in advance be set. In a case where the body height of the occupant is the second determination threshold value or higher, the occupant is determined to be a large occupant, and Fα(SH) may be used. In a case where the body height of the occupant is smaller than the second determination threshold value, the occupant is determined to be a small occupant, and Fβ(SH) may be used. Further, in the example illustrated in  FIG. 4 , the steering wheel height information is configured to include two function formulas Fα(SH) and Fβ(SH) but may include plural, three or more function formulas. Further, in the example illustrated in  FIG. 4 , the vertical axis (that is, the value of function formulas F(SH)) represents the height of the steering wheel; however, in the present embodiment, as described above, because the height of the steering wheel is changed by adjusting the tilt angle of the steering shaft  63  by the tilt mechanism in the steering device  6 , the vertical axis (that is, the value of the function formulas F(SH)) may be represented by the tilt angle of the steering shaft  63 . 
     The control processing unit  3  may be circuitry which respectively controls the units  1 ,  2 ,  4  to  7  of the alighting assistance device D in accordance with the functions of those units and which controls the driver seat DS and the steering wheel such that in a case where it is determined that the occupant seated on the driver seat DS of the vehicle alights, the driver seat DS is moved rearward, and the height of the steering wheel becomes lower as the sitting height of the occupant is higher. The control processing unit  3  is configured to include a CPU (central processing unit) and its peripheral circuits, for example. In the control processing unit  3 , the control processing programs are executed, and the controller  31 , a seat controller  32 , a steering wheel controller  33 , the eye level processing unit  34  ( 212 ), and the sitting height processing unit  35  ( 22 ) are thereby functionally configured. 
     The controller  31  may respectively control the units  1 ,  2 ,  4  to  7  of the alighting assistance device D in accordance with the functions of those units and manages control of the whole alighting assistance device D. 
     The seat controller  32  may control the seat driving unit  5 . Optionally, as illustrated in  FIG. 2A , when the SB switch  121  is inclined forward and while the SB switch  121  is inclined and positioned on a front side, the seat controller  32  controls the reclining mechanism  51  such that the seat back DSb is inclined forward and the inclination of the seat back DSb gradually becomes small. When the SB switch  121  is restored (returned to a prior neutral position), the seat controller  32  stops the reclining mechanism  51 . The seat back DSb maintains its posture at the current inclination. Meanwhile, when the SB switch  121  is inclined rearward, except the point that the seat back DSb is inclined rearward, the seat controller  32  acts similarly to the above-described case where the SB switch  121  is inclined forward. As illustrated in  FIG. 2A , when the SC switch  122  is moved forward and while the SC switch  122  is positioned on a front side, the seat controller  32  controls the slide mechanism  52  such that the seat cushion DSa is gradually moved forward. When the SC switch  122  is restored (returned to a prior neutral position), the seat controller  32  stops the slide mechanism  52 . The seat cushion DSa maintains its posture in the current front-rear position. Meanwhile, when the SC switch  122  is moved rearward, except the point that the seat cushion DSa is moved rearward, the seat controller  32  acts similarly to the above-described case where the SC switch  122  is moved forward. As illustrated in  FIG. 2A , when the back end of the SC switch  122  is inclined upward and while the SC switch  122  is inclined and positioned on an upper side, the seat controller  32  controls the lift mechanism  53  so as to gradually move the seat cushion DSa upward. When the SC switch  122  is restored (returned to a prior neutral position), the seat controller  32  stops the lift mechanism  53 . The seat cushion DSa maintains its posture in the current up-down position (height). Meanwhile, when the back end of the SC switch  122  is inclined downward, except the point that the seat cushion DSa is moved downward, the seat controller  32  acts similarly to the above-described case where a back end of the SC switch  122  is inclined upward. As illustrated in  FIG. 2A , when the front end of the SC switch  122  is inclined upward and while the SC switch  122  is inclined and positioned on an upper side, the seat controller  32  controls the tilt mechanism  54  so as to gradually move the front end of the seat cushion DSa upward. When the SC switch  122  is restored (returned to a prior neutral position), the seat controller  32  stops the tilt mechanism  54 . The seat cushion DSa maintains its posture with the seat surface at the current inclination. Meanwhile, when the front end of the SC switch  122  is inclined downward, except the point that the front end of the seat cushion DSa is moved downward, the seat controller  32  acts similarly to the above-described case where the front end of the SC switch  122  is inclined upward. When the posture of the driver seat DS is adjusted, the seat controller  32  stores the adjusted posture of the driver seat DS (the inclination of the seat back DSb, the front-rear position of the seat cushion DSa, the up-down position (height, lift amount) of the seat cushion DSa, and the tilt amount of the seat cushion DSa) in the storage unit  4 . 
     Furthermore, the seat controller  32  may control the seat driving unit  5  so as to move the driver seat DS rearward in a case where it is determined that the occupant seated on the driver seat DS of the vehicle alights. Optionally, the seat controller  32  controls the slide mechanism  52  such that the driver seat DS is moved by a predetermined movement amount set in advance and the position of the driver seat thereby comes to a rear side in a case where it is determined that the occupant seated on the driver seat DS of the vehicle alights. Accordingly, the slide mechanism  52  moves the seat cushion DSa of the driver seat DS rearward by the predetermined movement amount from the present position, for example. Note that a limit position of rearward movement of the seat cushion DSa may in advance be set, and the movement may be stopped in a case where the limit position is reached during the rearward movement of the seat cushion DSa of the driver seat DS. When the rearward movement of the driver seat DS is finished, the seat controller  32  informs the steering wheel controller  33  about the finish of the movement. 
     As described above, the eye level processing unit  34  may ( 212 ) obtain the eye level of the occupant by processing the predetermined data acquired by the eye level data acquisition unit  211 . 
     The sitting height processing unit  35  ( 22 ) may obtain the sitting height of the occupant based on the body height of the occupant which is input to the first input unit  11  and the eye level measured by the measuring unit  21 . Optionally, in the present embodiment, the sitting height processing unit  35  ( 22 ) obtains the sitting height of the occupant by using the sitting height conversion information stored in the sitting height conversion information storage unit  42  based on the body height of the occupant which is input to the first input unit  11  and the eye level measured by the measuring unit  21 . Optionally, in the present embodiment, because the sitting height conversion information is the sitting height conversion table CT, the sitting height processing unit  35  ( 22 ) designates the row from the rows by the body height of the occupant which is input to the first input unit  11  and is stored as the occupant information in the occupant information storage unit  41 , designates the column from the columns by the eye level measured by the measuring unit  21 , thereby selects (retrieves, extracts) the sitting height in the position where those designated row and column intersect with each other from the sitting heights which are registered in a two-dimensional matrix manner, and obtains the selected sitting height as the sitting height of the occupant. 
     The steering wheel controller  33  may control the tilt mechanism (one example of the height change unit  62 ) and the telescopic mechanism in the steering device  6  and thereby controls the position (the position in the up-down direction (height) and the position in the front-rear direction) of the steering wheel. Furthermore, in the present embodiment, in the case where it is determined that the occupant alights, the steering wheel controller  33  controls the tilt mechanism (one example of the height change unit  62 ) in the steering device  6  such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit  2  is higher. Optionally, in the case where it is determined that the occupant alights, the steering wheel controller  33  uses the steering wheel height information stored in the steering wheel height information storage unit  43  and thereby controls the tilt mechanism in the steering device  6  such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit  2  is higher. Optionally, in the present embodiment, the steering wheel height information is two function formulas Fα(SH) and Fβ(SH). Thus, in the case where it is determined that the occupant alights, the steering wheel controller  33  first determines whether the occupant seated on the driver seat DS is a large occupant or a small occupant and selects one function formula F(SH) from the two function formulas Fα(SH) and Fβ(SH) based on the determination result. In the above-described example, the steering wheel controller  33  compares the lift amount stored in the storage unit  4  with the determination threshold value. As a result of this comparison, in a case where the lift amount is the determination threshold value or larger, the occupant is determined to be a small occupant, and Fβ(SH) is selected. In a case where the lift amount is smaller than the determination threshold value, the occupant is determined to be a large occupant, and Fα(SH) is selected. The steering wheel controller  33  substitutes the sitting height SH of the occupant which is obtained by the sitting height processing unit  22  ( 35 ) of the sitting height acquisition unit  2  into the selected function formula F(SH), for example, the function formula Fα(SH), and obtains a height Fα(SH) of the steering wheel which corresponds to the sitting height of the occupant. Then, when the steering wheel controller  33  receives a notification indicating a finish of the movement from the seat controller  32 , the steering wheel controller  33  controls the tilt mechanism in the steering device  6  such that the obtained height Fα(SH) of the steering wheel is provided and thereby changes the height of the steering wheel. 
     Such control processing unit  3  and storage unit  4  may be capable of being configured by a computer which is referred to as, so-called, ECU (electronic control unit). 
     Note that the steering wheel controller  33  corresponds to one example of a height controller which controls the height change unit such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit is higher in the case where it is determined that the occupant alights and also corresponds to one example of a body height acquisition unit which acquires the body height of the occupant. In the present embodiment, the steering wheel controller  33  as one example of the body height acquisition unit acquires the height (the position in the up-down direction, the lift amount) of the seat surface of the driver seat DS. Further, the body height acquisition unit may be the input unit (first input unit  11 ) of the sitting height acquisition unit (the body height acquisition unit may also be used as the input unit of the sitting height acquisition unit). 
     Next, an action of the present embodiment will be described.  FIG. 5  is a flowchart illustrating an action of the alighting assistance device about assistance for alighting according to one embodiment of the present disclosure.  FIG. 6  is a diagram for explaining movement of the driver seat and a change in the height of the steering wheel in a case of alighting according to one embodiment of the present disclosure.  FIG. 6A  illustrates a situation where the movement of the driver seat and the change in the height of the steering wheel have not yet been performed, and  FIG. 6B  illustrates a situation where the movement of the driver seat and the change in the height of the steering wheel have already been performed. 
     When the vehicle starts working, such an alighting assistance device D executes initialization of each of the necessary units and starts working. The control processing programs are executed, and in the control processing unit  3 , the controller  31 , the seat controller  32 , the steering wheel controller  33 , the eye level processing unit  34  ( 212 ), and the sitting height processing unit  35  ( 22 ) are thereby functionally configured. 
     The occupant who rides on the vehicle and is seated on the driver seat DS adjusts the posture of the driver seat DS so as to realize a proper driving posture (driving position). For example, the posture of the driver seat DS is adjusted as illustrated in  FIG. 6A . Then, the occupant inputs his/her own body height from the first input unit  11 . When the first input unit  11  accepts the body height of the occupant seated on the driver seat DS, the alighting assistance device D stores the body height of the occupant as one piece of the occupant information in the occupant information storage unit  41  of the storage unit  4  by the controller  31  of the control processing unit  3 . Note that although the posture of the driver seat DS is manually adjusted here, the posture of the driver seat DS may automatically be adjusted when the first input unit  11  accepts the body height of the occupant. A proper driving posture is disclosed in Japanese Patent No. 6662360 (Japanese Patent Laid-open No. 2019-038320), for example. 
     The occupant seated on the driver seat DS causes the vehicle to travel and attempts to alight when the vehicle arrives at a destination, for example. 
     In  FIG. 5 , when it is determined that the occupant seated on the driver seat DS of the vehicle alights (S 1 ), the alighting assistance device D acquires the body height of the occupant stored in the occupant information storage unit  41  by the steering wheel controller  33  of the control processing unit  3  (S 2 ). 
     The determination in process S 1  is executed in accordance with ON and OFF of an ignition by an ignition key (or ignition button), for example, and when the ignition is turned OFF, the alighting assistance device D determines, by the steering wheel controller  33  of the control processing unit  3 , that the occupant seated on the driver seat DS alights. Alternatively, for example, the determination in process S 1  is executed in accordance with fastening and unfastening of a seat belt of the driver seat DS, and when the seat belt is unfastened, the alighting assistance device D determines, by the steering wheel controller  33  of the control processing unit  3 , that the occupant seated on the driver seat DS alights. For example, a switch or the like which is turned ON and OFF in accordance with fastening and unfastening of a buckle of the seat belt is provided to a tongue of the seat belt, and fastening and unfastening of the seat belt can thereby be detected. 
     Next, the alighting assistance device D measures the eye level of the occupant seated on the driver seat DS by the measuring unit  21  (S 3 ) and obtains, by the sitting height processing unit  22  ( 35 ), the sitting height of the occupant by using the sitting height conversion table CT stored in the sitting height conversion information storage unit  42  based on the body height of the occupant which is input to the first input unit  11  and stored in the occupant information storage unit  41  and the eye level which is measured by the measuring unit  21  (S 4 ). Note that the alighting assistance device D may store the obtained sitting height of the occupant as one piece of the occupant information in the occupant information storage unit  41  by the controller  31  and may use the sitting height in the next or further subsequent alighting of the occupant. Further, as described above, those processes S 3  and S 4  are executed in a case where the first input unit  11  accepts the body height of the occupant seated on the driver seat DS when he/she rides on the vehicle, and the obtained sitting height of the occupant may be stored as one piece of the occupant information in the occupant information storage unit  41 . In this case, instead of those processes S 3  and S 4 , the alighting assistance device D may acquire the sitting height of the occupant which is stored in the occupant information storage unit  41  similarly to process S 2 . 
     Next, the alighting assistance device D acquires the lift amount from the storage unit  4  by the steering wheel controller  33  (S 5 ). Note that the steering wheel controller  33  may acquire the lift amount from the lift mechanism  53  of the seat driving unit  5 . 
     Next, the alighting assistance device D obtains, by the steering wheel controller  33 , the height of the steering wheel based on the sitting height of the occupant which is acquired in process S 4  and the lift amount acquired in process S 5  (S 6 ). Optionally, the steering wheel controller  33  determines whether the occupant is large or small based on the lift amount acquired in process S 5  and selects either one of the two function formulas Fα(SH) and Fβ(SH). Then, the steering wheel controller  33  substitutes the sitting height SH of the occupant which is acquired in process S 4  into the selected function formula F(SH), for example, the function formula Fα(SH) in a case where the function formula Fα(SH) is selected and thereby obtains the height Fα(SH) of the steering wheel. 
     Then, the alighting assistance device D moves the driver seat DS rearward by the predetermined movement amount by the seat controller  32 . After this movement is finished, the alighting assistance device D controls, by the steering wheel controller  33 , the tilt mechanism in the steering device  6  such that the height Fα(SH) of the steering wheel which is obtained in process S 6  is provided, thereby changes the height of the steering wheel (S 7 ), and finishes this process. Accordingly, the driver seat DS illustrated in  FIG. 6A  moves rearward as indicated by an arrow B in  FIG. 6B , and the steering wheel  61  is moved upward as indicated by an arrow A in  FIG. 6B  such that the steering wheel comes to the height Fα(SH). 
     In a case where the occupant seated on the driver seat DS of the vehicle alights, when not only the driver seat moves rearward but also the steering wheel  61  is lifted up, not only a foot side space of the occupant but also a space around the upper body of the occupant expands, and the occupant thus more easily alights. In a case where the occupant alights, the occupant may alight while raising his/her upper body by gripping the steering wheel  61 . In this case, when the steering wheel  61  is lifted up high, it is more difficult for the occupant to grip the steering wheel  61  as his/her sitting height is higher. Because his/her arm bends at the elbow when he/she raises his/her upper body by gripping the steering wheel  61 , it is difficult to apply a force to the arm. 
     In a case where it is determined that the occupant alights, the alighting assistance device D and an alighting assistance method implemented therein in the embodiment control the height change unit  62  (the tilt mechanism of the steering device  6  in the above-described example) to change the height of the steering wheel such that the height of the steering wheel becomes lower as the sitting height acquired by the sitting height acquisition unit  2  is higher. Thus, the occupant easily grips the steering wheel  61 , and because his/her arm is stretched more (because the elbow more shallowly bends) when he/she raises his/her upper body by gripping the steering wheel  61 , it becomes easy to apply a force to the arm. Consequently, the above alighting assistance device D and the alighting assistance method can make alighting easier. 
     It is possible to obtain the so-called hip point based on the eye level, and it is possible to obtain the sitting height based on the body height and the hip point. In the present embodiment, the sitting height conversion information indicating the correspondence relationship between the body height and eye level (hip point) and the sitting height is in advance prepared and stored in the storage unit  4 . The above alighting assistance device D and the alighting assistance method include the first input unit  11 , the measuring unit  21 , and the sitting height processing unit  22  ( 35 ) and can thus precisely acquire the sitting height by a simple procedure by using the sitting height conversion information. 
     A small occupant whose body height is relatively low often sets the seat surface high and positions the position of the driver seat on a front side compared to a large occupant whose body height is relatively high. Thus, when the height of the steering wheel is set low, a space around the upper body of the occupant becomes narrow for the small occupant whose body height is relatively low. The above alighting assistance device D and the alighting assistance method change the height of the steering wheel such that the height of the steering wheel becomes higher as the body height is lower in a case where the sitting height is the same. Thus, the space around the upper body becomes wider for the small occupant, and the occupant more easily alights. Consequently, the above alighting assistance device D and the alighting assistance method can make alighting easier. 
     The above alighting assistance device D and the alighting assistance method move the driver seat DS rearward and thereafter lift up the steering wheel  61 . Thus, because the occupant has a wider clearance from the steering wheel (because the distance between the steering wheel  61  and the occupant becomes longer) when the steering wheel  61  is lifted up, the occupant can be given a sense of security about a lifting action of the steering wheel  61 . 
     Note that in the above-described embodiment, the alighting assistance device D may further include an arm length acquisition unit which acquires an arm length of the occupant and may increase the movement amount as the arm length acquired by the arm length acquisition unit is longer in a case where the driver seat is moved rearward. The alighting assistance device D of this modification form makes the rearward movement amount of the driver seat DS larger (more) as the arm length is longer. Thus, even the occupant whose arm length is relatively long easily grips the steering wheel, and because his/her arm is stretched more (because the elbow more shallowly bends) when he/she raises his/her upper body by gripping the steering wheel, it becomes easy to apply a force to the arm. Consequently, the above alighting assistance device can make alighting easier. 
     In the alighting assistance device D of this modification form, the control processing programs further include an arm length processing program for obtaining the arm length of the occupant, and as indicated by broken lines in  FIG. 1 , an arm length processing unit  36  is functionally configured in the control processing unit  3  by execution of the control processing programs. 
     The length ratios among parts of a human body, which correspond to nations or races, have statistically been ascertained (known). Thus, as for the arm length, it is possible to obtain the arm length based on the ratio of the sitting height to the body height. Consequently, arm length conversion information indicating the correspondence relationship between the ratio of the sitting height to the body height and the arm length, which corresponds to a place of delivery of the vehicle, for example, is in advance prepared as a function formula or a table, for example, and is stored in the storage unit  4 . Then, the arm length processing unit  36  obtains the arm length of the occupant by using the arm length conversion information stored in the storage unit  4  based on the body height of the occupant which is input to the first input unit  11  and stored in the occupant information storage unit  41  and the sitting height which is obtained by the sitting height processing unit  35  ( 22 ). The arm length processing unit  36  corresponds to one example of the above-described arm length acquisition unit which acquires the arm length of the occupant. 
     Rearward movement amount information indicating the correspondence relationship between the arm length and the rearward movement amount of the driver seat DS is in advance prepared as a function formula or a table, for example, and is stored in the storage unit  4 . The rearward movement amount information is set such that the movement amount is made larger (more) as the arm length is longer. Then, in a case where it is determined that the occupant seated on the driver seat DS of the vehicle alights, the seat controller  32  obtains the movement amount corresponding to the arm length obtained by the arm length processing unit  36  by using the rearward movement amount information stored in the storage unit  4  and controls the slide mechanism  52  so as to move the driver seat DS by this obtained movement amount. 
     Note that in the above description, the arm length is obtained and acquired based on the ratio of the sitting height to the body height, but the arm length may be input from the first input unit  11  and may thereby be acquired. 
     In order to express the present disclosure, the present disclosure has appropriately and sufficiently been described through the embodiments with reference to the drawings in the above descriptions. However, it should be noted that a person skilled in the art can easily change and/or improve the above-described embodiments. Accordingly, unless changed forms or improved forms that are carried out by a person skilled in the art depart from the scope of rights of the claims, the changed forms or the improved forms are construed as encompassed in the scope of rights of the claims. 
     REFERENCE SIGNS LIST 
     
         
         D alighting assistance device 
           1  input unit 
           2  sitting height acquisition unit 
           3  control processing unit 
           4  storage unit 
           5  seat driving unit 
           6  steering device 
           7  HUD 
           11  first input unit 
           21  measuring unit 
           22  ( 35 ) sitting height processing unit 
           211  eye level data acquisition unit 
           212  ( 34 ) eye level processing unit 
           31  controller 
           32  seat controller 
           33  steering wheel controller 
           41  occupant information storage unit 
           42  sitting height conversion information storage unit 
           43  steering wheel height information storage unit 
           52  slide mechanism 
           61  steering wheel 
           62  height change unit