Abstract:
A vehicle seat includes a seat bottom and a seat back. The seat back is coupled to the seat bottom and arranged to extend in an upward direction away from the seat bottom. The vehicle seat further includes an electronics system.

Description:
PRIORITY CLAIM 
       [0001]    This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 62/221,653, filed Sep. 22, 2015, which is expressly incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to a vehicle seat and in particular to a vehicle seat including a sensor. More particularly, the present disclosure relates to a vehicle seat including one or more sensors coupled to an electronic controller for a vehicle seat. 
       SUMMARY 
       [0003]    A vehicle seat in accordance with the present disclosure includes a seat bottom and a seat back. The seat back is coupled to the seat bottom and arranged to extend in an upward direction away from the seat bottom. 
         [0004]    In illustrative embodiments, the vehicle seat includes a foundation comprising a rail and a rail receiver, a magnetic feature, and a magnetic sensor coupled to the foundation, and a seat controller coupled to the magnetic sensor. The rail is coupled to the seat bottom of the vehicle seat and the rail receiver defines a track to receive the rail and to allow the rail to move along a predefined linear path. The magnetic sensor is configured to generate sensor data in response to sensing the magnetic feature of the rail. The seat controller is configured to determine a position of the rail along the predefined linear path as a function of the sensor data generated by the magnetic sensor. 
         [0005]    In illustrative embodiments, the magnetic feature is coupled to the rail of the foundation and the magnetic sensor is coupled to the rail receiver of the foundation. In illustrative embodiments, the magnetic feature may be coupled to the rail receiver of the foundation, and the magnetic sensor may be coupled to the rail of the foundation. 
         [0006]    In illustrative embodiments, the magnetic feature comprises a magnetic stripe and the sensor data is indicative of magnetic field strength of the magnetic feature in proximity to the magnetic sensor. To determine the position of the rail along the predefined linear path may include a linear function of the magnetic field strength. 
         [0007]    In illustrative embodiments, the magnetic feature comprises a magnetic stripe, the sensor data is indicative of magnetic field strength of the magnetic feature in proximity to the magnetic sensor, and to determine the position of the rail along the predetermined linear path may include determining a sequence of magnetic field strength values based on the sensor data and decode the sequence of magnetic field strength values to determine the position. In illustrative embodiments, the magnetic feature may include a magnetic stripe including a plurality of magnetic signal tracks, the sensor data is indicative of a plurality of magnetic field strength values, wherein each magnetic fields strength value is associated with a signal track of the magnetic feature in proximity to the magnetic sensor, and to determine the position of the rail along the predetermined linear path may include to decode the plurality of magnetic field strength values to determine the position. 
         [0008]    In illustrative embodiments, the vehicle seat includes a first member, a second member coupled to the first member, a visual feature coupled to the first member, an optical sensor coupled to the second member, and a seat controller coupled to the optical sensor. The second member is configured to move rotationally relative to the first member. The optical sensor is configured to generate sensor data indicative of the visual feature, and the seat controller is configured to determine a rotational position of the second member relative to the first member as a function of the sensor data generated by the optical sensor. In illustrative embodiments, the first member may include the seat bottom and the second member may include the seat back. In illustrative embodiments, the first member may include the seat back and the second member may include the seat bottom. In illustrative embodiments, the optical sensor may include a camera, a photodiode, or a photocell. In illustrative embodiments, the visual feature may include a color gradient or a shape. 
         [0009]    Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       [0010]    The detailed description particularly refers to the accompanying figures in which: 
         [0011]      FIG. 1  is a perspective and diagrammatic view of a vehicle seat in accordance with the present disclosure showing that the vehicle seat includes a magnetic feature and a magnetic sensor that senses the magnetic feature; 
         [0012]      FIG. 2  is a perspective view of part of the vehicle seat of  FIG. 1  showing that the magnetic feature is included on a seat rail, the magnetic sensor is attached to a rail receiver, and the magnetic feature slides past the magnetic sensor; 
         [0013]      FIG. 3  is a perspective view of part of another embodiment of a vehicle seat in accordance with the present disclosure showing that the magnetic feature is included on the rail receiver, the magnetic sensor is attached to the rail, and the magnetic sensor slides past the magnetic feature; 
         [0014]      FIG. 4  is a schematic diagram illustrating at least one embodiment of the magnetic feature of  FIGS. 1-3 ; 
         [0015]      FIG. 5  is an plot showing illustrative sensor data that may be indicative of the magnetic feature of  FIG. 4 ; 
         [0016]      FIG. 6  is a schematic diagram illustrating one embodiment of the magnetic feature of  FIGS. 1-3 ; 
         [0017]      FIG. 7  is a schematic diagram illustrating one embodiment of the magnetic feature of  FIGS. 1-3 ; 
         [0018]      FIG. 8  is an plot showing illustrative sensor data that may be indicative of the magnetic feature of  FIG. 7 ; 
         [0019]      FIG. 9  is a perspective and diagrammatic view of a vehicle seat in accordance with the present disclosure showing that the vehicle seat includes a visual feature and an optical sensor that senses the visual feature; 
         [0020]      FIG. 10  is a schematic diagram illustrating at least one embodiment of the visual feature of  FIG. 9 ; 
         [0021]      FIG. 11  is a schematic diagram illustrating at least one embodiment of the visual feature of  FIG. 9 ; 
         [0022]      FIG. 12  is a cross-sectional diagrammatic view of a seat rail and rail receiver in accordance with the present disclosure showing that the rail receiver includes a visual feature and the seat rail includes an optical sensor that senses the visual feature; and 
         [0023]      FIG. 13  is a flow diagram illustrating at least one embodiment of a method for determining vehicle seat position that may be executed by the seat controller of  FIGS. 1 and 9 . 
     
    
     DETAILED DESCRIPTION 
       [0024]    A first embodiment of a vehicle seat  10  in accordance with the present disclosure is shown, for example, in  FIGS. 1 and 2 . Vehicle seat  10  includes a headrest  12 , a backrest  14 , and a seat bottom  16 . In some embodiments, headrest  12 , backrest  14 , and/or the seat bottom  16  may be movable or otherwise adjustable, for example adjustable for seat bottom angle, seat back recline, and/or head restraint position. Vehicle seat  10  is coupled to a foundation  18  and foundation  18  may be attached to a vehicle such as a car or a truck (not shown) to provide seating for the vehicle&#39;s driver and/or other occupants. 
         [0025]    Foundation  18  includes a pair of seat rails  20  and a pair of rail receivers  22 . As shown, each of seat rails  20  attaches to seat bottom  16  and extends longitudinally. Foundation  18  includes an inboard seat rail  20  and an outboard seat rail  20 . Other embodiments the foundation  18  may include a different number and/or arrangement of seat rails  20 . Each of rail receivers  22  defines a track  24  to receive a seat rail  20 . Track  24  allows seat rail  20 —and the attached seat bottom  16 —to move along a predefined longitudinal path  26  with respect to the vehicle. In some embodiments, vehicle seat  10  may include a seat mover (not shown) to move automatically the seat rail  20  along the longitudinal path  26 . 
         [0026]    Vehicle seat  10  includes a magnetic sensor  28  coupled to one of rail receivers  22 . Magnetic sensor  28  may be embodied as any electronic sensor capable of measuring magnetic field strength. Corresponding seat rail  20  includes a magnetic feature  30  which may be embodied as a magnetic stripe or any other magnetic feature detectible by the magnetic sensor  28 . Magnetic feature  30  may be applied to the corresponding seat rail  20  or may be embedded in the seat rail  20  during manufacturing. 
         [0027]    For example, in some embodiments, parts of the seat rail  20  may be magnetized selectively during manufacturing. Magnetic sensor  28  is configured to sense magnetic field strength associated with magnetic feature  30  as magnetic feature  30  moves relative to magnetic sensor  28 . Various techniques for determining the position of the seat rails  20  and/or the seat bottom  16  are described further below in connection with  FIGS. 4-8 . Although illustrative vehicle seat  10  includes a single magnetic sensor  28  and magnetic feature  30 , vehicle seat  10  may include any number of suitable magnetic sensors  28  and/or magnetic features  30  coupled to rail receivers  22  and/or seat rails  20 , respectively. 
         [0028]    As shown in  FIG. 3 , in some embodiments magnetic feature  30  is included on the rail receiver  22  and magnetic sensor  28  may be coupled to seat rail  20 . In those embodiments, magnetic feature  30  may be applied to the corresponding rail receiver  22  or may be embedded in the rail receiver  22  during manufacturing. In those embodiments, magnetic sensor  28  is configured to sense magnetic field strength associated with magnetic feature  30  as magnetic sensor  28  moves relative to the magnetic feature  30 . 
         [0029]    As shown in  FIG. 1 , illustrative vehicle seat  10  further includes a tilt unit  32  coupling seat back  14  and seat bottom  16 . Tilt unit  32  allows seat back  14  to rotate relative to seat bottom  16  about a tilt axis  34 . Thus, tilt unit  32  allows seat back  14  to rotate along a predefined rotational path  36 . Rotational position sensors to determine the rotational position of seat back  14  are described further below in connection with  FIGS. 9 and 10 . 
         [0030]    Vehicle seat  10  further includes a seat controller  38 , which may be embodied as an electronic control unit or other controller configured to control the functions of the vehicle seat  10 . Seat controller  38  is configured to determine the position of seat rails  20  and/or vehicle seat  10  based on sensor data read from magnetic sensor  28 . Seat controller  38  may be configured to determine the rotational position of seat back  14  relative to seat bottom  16  based on sensor data read from one or more magnetic sensors. Vehicle seat  10  is capable of determining seat position without using potentiometers and without counting motor turns using a Hall-effect sensor. Vehicle seat  10  may reduce costs compared to other sensor technologies. Vehicle seat  10  may provide improved reliability compared to contact sensors such as potentiometers. 
         [0031]    Seat controller  38  may be positioned underneath or within seat bottom  16  as shown in  FIGS. 1 and 9 . In some embodiments, seat controller  38  may include or be otherwise coupled with a side shield positioned on the outside of vehicle seat  10 . The side shield may include one or more buttons, switches, or other user controls that allow the user to interact with and otherwise control vehicle seat  10 . 
         [0032]    Seat controller  38  may be embodied as any device capable of performing the functions described herein. For example, seat controller  38  may be embodied as an electronic control unit, embedded controller, control circuit, microcontroller, computing device, on-board computer, and/or any other any other computing device capable of performing the functions described herein. Seat controller  38  may include typical components of an electronic control unit, including a processor, an I/O subsystem, a memory, a data storage device, and communication circuitry. Seat controller  38  may include other or additional components, such as those commonly found in an electronic control unit (e.g., various input/output devices), in other embodiments. 
         [0033]    In some embodiments, one or more of the illustrative components may be incorporated in, or otherwise form a portion of, another component. For example, the memory, or portions thereof, may be incorporated in the processor in some embodiments. Additionally, although illustrated as a separate seat controller  38 , in some embodiments part or all of the functionality of the seat controller  38  may be performed by magnetic sensor  28 , for example by an embedded microcontroller included or otherwise coupled to magnetic sensor  28 . 
         [0034]    The processor may be embodied as any type of processor capable of performing the functions described herein. For example, the processor may be embodied as a microcontroller, digital signal processor, single or multi-core processor(s), or other processor or processing/controlling circuit. Similarly, the memory may be embodied as any type of volatile or non-volatile memory or data storage capable of performing the functions described herein. In operation, the memory may store various data and software used during operation of the processor such as operating systems, applications, programs, libraries, and drivers. The memory is coupled to the processor via the I/O subsystem, which may be embodied as circuitry and/or components to facilitate input/output operations with the processor, the memory, and other components of seat controller  38 . For example, the I/O subsystem may be embodied as, or otherwise include, memory controller hubs, input/output control hubs, firmware devices, communication links (i.e., point-to-point links, bus links, wires, cables, light guides, printed circuit board traces, etc.) and/or other components and subsystems to facilitate the input/output operations. In some embodiments, the I/O subsystem may form a portion of a system-on-a-chip (SoC) and be incorporated, along with the processor, the memory, and other components of the seat controller  38 , on a single integrated circuit chip. 
         [0035]    The data storage device may be embodied as any type of device or devices configured for short-term or long-term storage of data such as, for example, memory devices and circuits, memory cards, hard disk drives, solid-state drives, read-only memory, or other data storage devices. The communication circuitry of seat controller  38  may be embodied as any communication circuit, device, or collection thereof, capable of enabling communications between seat controller  38  and other devices of vehicle seat  10  and/or the vehicle. The communication circuitry may be configured to use any one or more communication technology (e.g., wireless or wired communications) and associated protocols (e.g., Ethernet, controller area network (CAN), local interconnect network (LIN), Bluetooth®, Wi-Fi®, etc.) to effect such communication. 
         [0036]    As shown in  FIG. 4 , schematic diagram  100  illustrates one potential embodiment of a magnetic feature  30 . As shown, magnetic feature  30  is linear and arranged to extend along predefined longitudinal path  26 . For example, magnetic feature  30  may be embodied as a magnetic stripe extending along a seat rail  20  and/or a rail receiver  22 . As shown, magnetic feature  30  includes several magnetic regions  40 . Each magnetic region  40  is positioned at a particular location within magnetic feature  30 . Each magnetic region  40  has an associated magnetic field. Magnetic field strength of each magnetic region  40  is represented by shading. For example, in the illustrative embodiment, magnetic region  40   a  has the weakest magnetic field and magnetic region  40   f  has the highest magnetic field. Although illustrated as including six magnetic regions  40 , magnetic feature  30  may include any number of magnetic regions  40 . Increasing the number of magnetic regions  40  may increase the resolution of the seat position value that may be determined. 
         [0037]    As shown in  FIG. 5 , plot  102  illustrates magnetic field strength plotted against position for magnetic feature  30  of diagram  100 . As shown, each magnetic field region  40  of magnetic feature  30  has a magnetic field with a different strength. Seat controller  38  or other sensing system may determine position of seat rail  20  by measuring the analog magnetic field strength value using the magnetic sensor  28  (e.g., by measuring the field strength in gauss) and converting the magnetic field strength value to a position value. Each measured magnetic field value corresponds to a particular position value. Thus, seat controller  38  may only make a single measurement of magnetic field strength to determine the position value, and no home position is required to be measured. As shown in  FIG. 5 , the position value and the magnetic field strength value may be proportional or otherwise linearly related. 
         [0038]    As shown in  FIG. 6 , schematic diagram  200  illustrates another potential embodiment of a magnetic feature  30 . As shown, magnetic feature  30  is linear and arranged to extend along predefined longitudinal path  26 . Magnetic feature  30  may be embodied as a magnetic stripe extending along a seat rail  20  and/or a rail receiver  22 . Magnetic feature  30  includes a track  42  that includes a sequence of magnetic regions. Each of the magnetic regions has either a high magnetic field strength or a low magnetic field strength. Track  42  corresponds to a sequence of binary values. Seat controller  38  may read a sequence of binary values from magnetic sensor  28  for a position within magnetic feature  30  and then decode the sequence of binary values to determine the position value. 
         [0039]    As shown in  FIG. 7 , schematic diagram  300  illustrates another potential embodiment of a magnetic feature  30 . As shown, magnetic feature  30  is linear and arranged to extend along predefined longitudinal path  26 . Magnetic feature  30  may be embodied as a magnetic stripe extending along a seat rail  20  and/or a rail receiver  22 . Magnetic feature  30  includes four tracks  42  that each include a sequence of magnetic regions. As described above in connection with  FIG. 6 , each of the magnetic regions has either a high magnetic field strength or a low magnetic field strength. Each track  42  of magnetic regions corresponds to a sequence of binary values. Magnetic sensor  28  includes several read heads  44  with each read head  44  positioned opposite a corresponding track  42 . Seat controller  38  may read a binary value from each of the read heads  44  and decode the binary values to determine the position value. 
         [0040]    As shown in  FIG. 8 , plot  302  illustrates sensor data that may be produced by magnetic sensor  28 . The waveform  304  represents magnetic field strength of the track  42   a  measured by read head  44   a.  The waveform  306  represents magnetic field strength of the track  42   b  measured by read head  44   b.  The waveform  308  represents magnetic field strength of the track  42   c  measured by read head  44   c.  The waveform  310  represents magnetic field strength of the track  42   d  measured by read head  44   d.  As shown, each permutation of binary values (e.g.,  1111 ,  1110 , etc.) may correspond to a particular position along magnetic feature  30 . For example, area  312  illustrates binary values that may be generated by magnetic sensor  28  when located in the position shown in  FIG. 7 . 
         [0041]    Magnetic feature  30  of  FIG. 7  includes four tracks  42   a  through  42   d  and four corresponding read heads  44   a  through  44   d.  Magnetic feature  30  may have a resolution of 16 positions. In some embodiments, magnetic sensor  28  may be capable of measuring magnetic field values with a positional resolution of five millimeters. Thus, in an illustrative embodiment that supports 16 possible positions at a resolution of five millimeters each, magnetic feature  30  may be capable of measuring position within a total travel of 80 millimeters. It should be understood that in other embodiments a different number of tracks  42  and read heads  44  may be used. To support finer positional resolution and/or additional total travel, magnetic feature  30  and magnetic sensor  28  may include additional tracks  42  and read heads  44 , respectively. For example, in another embodiment, to support a total travel of 220 millimeters with five millimeter resolution (i.e., 44 possible positions), magnetic feature  30  may include six tracks  42 . As another example, to support a total travel of 400 millimeters with five millimeter resolution (i.e.,  80  possible positions), magnetic feature  30  may include seven tracks  42 . 
         [0042]    As shown in  FIGS. 9 and 10 , a diagram  400  illustrates another embodiment of a vehicle seat  10  in accordance with the present disclosure. Vehicle seat  10  includes headrest  12 , backrest  14 , and a seat bottom  16 . Vehicle seat  10  is coupled to foundation  18  and foundation  18  may be attached to a vehicle such as a car or a truck (not shown) to provide seating for the vehicle&#39;s driver and/or other occupants. Foundation  18  includes pair of seat rails  20  attached to the seat bottom  16  and pair of rail receivers  22  that define track  24  to receive seat rails  20 . 
         [0043]    Vehicle seat  10  further includes tilt unit  32  coupling the seat back  14  and the seat bottom  16 . Tilt unit  32  allows seat back  14  to rotate relative to the seat bottom  16  about tilt axis  34 . Tilt unit  32  allows seat back  14  to rotate along a predefined rotational path  36 . Vehicle seat  10  of  FIGS. 9 and 10  is capable of measuring angular position of seat back  14  along predefined rotational path  36 . 
         [0044]    Vehicle seat  10  includes an optical sensor  402 . Optical sensor  402  is coupled to seat bottom  16  along tilt axis  34  and thus remains fixed relative to the seat bottom  16  as seat back  14  rotates about the tilt axis  34 . Optical sensor  402  may be embodied as any electronic sensor capable of measuring light intensity, color, or other visual information. In some embodiments, optical sensor  402  may be capable of capturing image data. Optical sensor  402  may be embodied as, for example, a photodiode, a photocell, a digital camera, an ambient light sensor, or any other appropriate photo sensor. Vehicle seat  10  may also include a light source for optical sensor  402 , such as an LED light (not shown). The spectral content of the light source should match the spectral response of optical sensor  402 . Vehicle seat  10  may include a shroud or other aperture to prevent light generated by the light source from directly entering optical sensor  402 . 
         [0045]    Vehicle seat  10  further includes a visual feature  404 , which may be embodied as any feature of vehicle seat  10  that varies visually with the rotation of backrest  14  relative to seat bottom  16 . For example, visual feature  404  may be embodied as printed markings similar to a color wheel as shown in  FIG. 10 . As another example, visual feature  404  may be embodied as structural or mechanical features of seat back  14  and/or seat bottom  16  such as a bolt pattern or other visual features of tilt unit  32 . As yet another example, visual feature  404  may be embodied as one or more geometric shapes that vary visually relative to rotational and/or linear position along visual feature  404 . For example, visual feature  404  may be embodied as a printed and/or etched triangle shape with a base at one end of visual feature  404  that extends to a vertex at the other end of visual feature  404 . 
         [0046]    In some embodiments, vehicle seat  10  may include a reference feature having a solid, fixed brightness and/or color (e.g., a solid white or gray stripe) that may be compared to visual feature  404 . In those embodiments, vehicle seat  10  may include an additional optical sensor  402  to measure the intensity and/or color of light reflected from the reference feature. 
         [0047]    Visual feature  404  is attached to backrest  14  around tilt axis  34  and thus rotates about tilt axis  34 . Although vehicle seat  10  has optical sensor  402  fixed with respect to seat bottom  16  and visual feature  404  fixed with respect to backrest  14 , in some embodiments, optical sensor  402  may be fixed with respect to backrest  14  and visual feature  404  may be fixed with respect to seat bottom  16 . Vehicle seat  10  may include a shroud or other aperture to allow light reflected by visual feature  404  (for example, light generated by a light source) to enter optical sensor  402 . 
         [0048]    Although illustrated in  FIG. 9  as including a separate seat controller  38 , in some embodiments, part or all of the functionality of seat controller  38  may be performed by the optical sensor  402 , for example by an embedded microcontroller included or otherwise coupled to the optical sensor  402 . 
         [0049]    As shown in  FIG. 10 , one potential embodiment of a visual feature  404  is shown. Visual feature  404  is an arc including multiple segments  406 . Visual feature  404  may be, for example, applied to backrest  14  or included in backrest  14  during manufacturing. Each segment  406  has a different color, which is represented in  FIG. 10  by shading. Each color thus corresponds to a particular angular position value. Seat controller  38  may measure color using optical sensor  402  and then determine the angular position value based on the measured color. For example, seat controller  38  may determine a ratio of red, blue, and green values for the measured color and determine the angular position based on that ratio. Visual feature  404  includes twelve regions  406   a  through  406   l.  Increasing the number of colored segments  406  may increase the resolution of the angular seat position value that can be determined. In some embodiments, the color of visual feature  404  may change smoothly, for example, changing smoothly from red to blue. Additionally or alternatively, in some embodiments visual feature  404  may include segments  406  in various shades of gray and optical sensor  402  may measure intensity of the reflected light. 
         [0050]    As shown in  FIG. 11 , a schematic diagram  500  illustrates another potential embodiment of a visual feature  404 . Visual feature  404  is linear and may be used, for example, to measure position along predefined longitudinal path  26 . For example, visual feature  404  may be applied or otherwise fixed to a seat rail  20  and/or a rail receiver  22 . Visual feature  404  includes two tracks  502 . Each track  502  includes a series of segments  406 . In the illustrative embodiment, each segment  406  has a different shade of gray. Vehicle seat  10  may include an optical sensor  402  for each track  502 . Each optical sensor  402  measures the intensity of light reflected by corresponding track  502 . The combination of measured light intensity values from each optical sensor  402  represents a particular linear position value. For example, seat controller  38  may read light intensity values from optical sensors  402  and determine linear position based on those measured values. Although the illustrative embodiment includes grayscale segments  406 , some embodiments each segment  406  may have a different color, and optical sensors  402  may measure the color of the reflected light. 
         [0051]    As shown  FIG. 11 , visual feature  404  may allow for position measurements at a resolution equivalent to the width of the segments  406  of track  502  having the smallest segment width (i.e., track  502   a  of  FIG. 11 ). For example, in an illustrative embodiment, each segment  406  of track  502   a  may be five millimeters wide. In that embodiment, an aperture may limit the optical sensor  402  to view only five millimeters of the visual feature  404  at one time. Thus, in the illustrative embodiment, visual feature  404  may allow position measurements at five millimeter resolution over 80 millimeters of total travel. In another embodiment, visual feature  404  may include segments  406  having eight different shades of gray. In that embodiment, track  502   a  may include  64  segments  406  and the track  502   b  may include eight segments  406 . In that embodiment, visual feature  404  thus may allow position measurements at five millimeter resolution over 320 millimeters of total travel. To provide additional positional resolution and/or total travel, vehicle seat  10  may include additional optical sensors  402  and associated tracks  502 . 
         [0052]    As shown in  FIG. 12 , cross-sectional diagram  600  illustrates one potential embodiment of a seat rail  20  and rail receiver  22  according to the present disclosure. As shown, rail receiver  22  defines a track  24  to receive the seat rail  20 . Track  24  of rail receiver  22  includes a bottom wall  602 , and as shown in the illustrative diagram  600 , visual feature  404  is attached or otherwise included on the bottom wall  602 . Seat rail  20  further includes a bottom surface  604  that faces bottom wall  602  of track  24 . Bottom surface  604  of seat rail  20  and bottom wall  602  of track  24  are separated by an air gap. 
         [0053]    Optical sensor  402  is attached to bottom surface  604  of seat rail  20  and thus may measure light reflected by visual feature  404 . The illustrative embodiment further includes a light-emitting diode (LED)  606  and a shroud  608  attached to bottom surface  604  of seat rail  20 . Light emitted by the LED  606  is blocked by shroud  608  from being directly received by optical sensor  402 . Light emitted by the LED  606  may reflect off of visual feature  404  and then reach optical sensor  402  through an aperture in shroud  608 . The aperture in shroud  608  may be sized to allow optical sensor  402  to sense one segment  406  of visual feature  404  at a time, for example, being sized to allow optical sensor  402  to sense a five-millimeter square area of visual feature  404 . 
         [0054]    As shown in  FIG. 13 , in use, seat controller  38  may execute a method  700  for determining seat position. Method  700  begins in block  702  in which seat controller  38  receives sensor data from one or more sensors. In some embodiments, in block  704  seat controller  38  receives magnetic field strength values from one or more magnetic sensors  28 . In some embodiments, in block  706 , seat controller  38  receives optical sensor data from one or more optical sensors  402 . The optical sensor data may be embodied as light intensity values, color values, image data, or other data indicative of visual information measured by optical sensor  402 . 
         [0055]    In block  708 , seat controller  38  determines a seat position value based on the sensor data. In some embodiments, in block  710  seat controller  38  may determine a linear position along predefined longitudinal path  26  based on measured magnetic field strength. Determination of seat position based on measured magnetic field strength is described further above in connection with  FIGS. 1-5 . In some embodiments, in block  712 , seat controller  38  may decode magnetic field strengths associated with one or more tracks  42  of magnetic feature  30  to determine a linear position along the predefined longitudinal path  26 . Determination of seat position by decoding a sequence of magnetic field strength values is further described above in connection with  FIGS. 1-3 and 6-8 . In some embodiments, in block  714 , seat controller  38  may determine a rotational position along the predefined rotational path  36  based on visual features determined from the sensor data produced by one or more optical sensors  402 . For example, seat controller  38  may determine rotational position based on light intensity data or color data. In some embodiments, seat controller  38  may perform one or more machine vision algorithms to determine rotational position based on image data, for example determining rotational position based on images of a bolt pattern of vehicle seat  10 . Determination of seat position based on visual features is described further above in connection with  FIGS. 9-12 . After determining the seat position based on the sensor data, method  700  loops back to block  702  to continue receiving sensor data. 
         [0056]    Referring back to  FIGS. 1-3 , although illustrated as including a magnetic sensor  28  and a magnetic feature  30  to measure seat position along the predefined longitudinal path  26 , in some embodiments vehicle seat  10  may include one or more optical sensors  402  and corresponding visual features  404  to measure seat position along the predefined longitudinal path  26 . For example, a visual feature  404  may be attached to rail receiver  22  and an optical sensor  402  may be included on seat rail  20 , similar to the arrangement of  FIG. 2  and/or  FIG. 12 . 
         [0057]    As another example, a visual feature  404  may be attached to seat rail  20  and an optical sensor  402  may be included on rail receiver  22 , similar to the arrangement of  FIG. 3 . As still another example, a visual feature  404  may be included on a bottom wall of rail receiver  22  within track  24  so that seat rail  20  blocks ambient light from reaching visual feature  404  similar to the arrangement of  FIG. 12 . In those embodiments, vehicle seat  10  may include a light source (e.g., one or more LEDs) within track  24  of rail receiver  22  to illuminate visual feature  404 . 
         [0058]    Referring back to  FIG. 9 , although illustrated as including an optical sensor  402  and a visual feature  404  to measure rotational position along predefined rotational path  36 , in some embodiments vehicle seat  10  may include one or more magnetic sensors  28  and corresponding magnetic features  30  to measure rotational position along the predefined rotational path  36 . For example, a magnetic sensor  28  may be attached to seat bottom  16  along tilt axis  34  and a magnetic feature  30  may be included in backrest  14 , similar to the arrangement of  FIG. 9 . As another example, a magnetic sensor may be attached to backrest  14  and a magnetic feature  30  may be included in seat bottom  16 . 
         [0059]    A position sensor in accordance with the present disclosure may be used with a track for a vehicle seat to determine a longitudinal position of the vehicle seat relative to the floor. However, a position sensor in accordance with the present disclosure, may be used to determine a tilt angle of a seat bottom, a height of a seat bottom above the floor, an angular position of a seat back, a height of a headrest relative to a backrest, a length of a cushion included in a seat bottom, or any other position or dimension included in a vehicle seat or other suitable occupant support. Position sensors in accordance with the present disclosure include magnetic sensors and magnetic features and optical sensors and optical features. 
         [0060]    An occupant support comprises a stationary component, a movable component coupled to the stationary component to move relative to the stationary component, and a position sensing system. The position sensing system is configured to determine an absolute position of the movable component relative to the stationary component. The position sensing system includes a magnetic feature coupled to the movable component, a magnetic sensor coupled to the stationary component and configured to generate sensor data in response to sensing the magnetic feature, and a controller. The controller is coupled to the magnetic sensor and configured to determine an absolute position of the movable component relative to the stationary component the predefined linear path as a function of the sensor data generated by the magnetic sensor. 
         [0061]    A position sensing system in accordance with the present disclosure may be used to determine an absolute or actual location of a moving component relative to a stationary component in an occupant support. In one example, the position sensing system determines a longitudinal position of a movable rail included in a track relative to a stationary rail included in the track. In another example, the position sensing system determines a rotational angle of a moving seat back relative to seat bottom. In another example, the position sensing system determines a height of a moving seat bottom relative a floor of the vehicle. In another example, the position sensing system determines a tilt of a moving seat bottom relative to a floor of the vehicle. In another example, the position sensing system determines a position of an adjustable portion of an adjustable cushion relative to a stationary portion of an adjustable cushion. In another example, the position sensing system determines a location of a moving headrest relative to a backrest included in a seat back. In another example, the position sensing system determines an angle of a moving upper back adjuster relative to a stationary portion of the backrest included in the seat back.