Abstract:
Methods and apparatus are provided for an active seat damper. The method of controlling a damper of a seat of a vehicle includes receiving data indicating a condition associated with the seat and determining a natural frequency of the seat based on the condition. The method also includes outputting one or more control signals to control a natural frequency of the damper based on the natural frequency of the seat.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to vibration mitigation and more particularly relates to systems and methods for mitigating vibration in a seat of a vehicle. 
       BACKGROUND 
       [0002]    In certain driving conditions, an operator and/or passengers may experience vibrations during the operation of a vehicle. The vibrations may be transmitted to the operator from the seat on which the operator and/or passenger is sitting. In addition, if one or more of the seats of the vehicle are unoccupied during operation of the vehicle, the vehicle seat may vibrate visibly during the operation of the vehicle. These vibrations experienced during the operation of the vehicle may lead to operator dissatisfaction and may result in unwanted noise. 
         [0003]    Accordingly, it is desirable to provide improved systems and methods for mitigating vibration of the seats of the vehicle during the operation of the vehicle. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
       SUMMARY 
       [0004]    In one embodiment, a method is provided for controlling a damper of a seat of a vehicle. The method includes receiving data indicating a condition associated with the seat and determining a natural frequency of the seat based on the condition. The method also includes outputting one or more control signals to control a natural frequency of the damper based on the natural frequency of the seat. 
         [0005]    In one embodiment, an apparatus is provided for a damper control system for a seat of a vehicle. The apparatus includes at least one sensor that determines a condition of the seat and a damper control module that controls the damper based on the condition of the seat. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]    The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
           [0007]      FIG. 1  is a functional block diagram illustrating a vehicle that includes an active seat damper system in accordance with various embodiments; 
           [0008]      FIG. 2  is a dataflow diagram illustrating a control system of the active seat damper system in accordance with various embodiments; 
           [0009]      FIG. 3  is a flowchart illustrating a control method of the active seat damper system in accordance with various embodiments; and 
           [0010]      FIG. 4  is a flowchart illustrating a control method of the active seat damper system in accordance with various embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. As used herein, the term module refers to any hardware, software, firmware, electronic control component, processing logic, and/or processor device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0012]    With reference to  FIG. 1 , a vehicle  10  is shown. The vehicle  10  includes one or more occupant seats  12 . For clarity, a single seat  12  is illustrated herein, but the vehicle  10  can have any number of seats  12 , and thus,  FIG. 1  is merely exemplary. The seat  12  includes a seat bottom  14 , a seat back  16  and an active seat damper system  18  in accordance with various embodiments. Although the figures shown herein depict an example with certain arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment. It should also be understood that  FIG. 1  is merely illustrative and may not be drawn to scale. 
         [0013]    The seat bottom  14  provides a seating surface for an occupant of the vehicle  10 , as is generally known in the art. The seat bottom  14  may have any desired shape, and may be covered with any desired covering for comfort and to provide an aesthetically pleasing appearance. The seat bottom  14  may be movably coupled to the vehicle  10 , such that the seat  12  may be positionable at various locations within the vehicle  10  as is generally known. 
         [0014]    The seat back  16  is coupled to the seat bottom  14  for supporting an occupant&#39;s back. Generally, the seat back  16  is movably coupled to the seat bottom  14  such that the seat back  16  may be moved through a variety of inclined angles relative to the seat bottom  14 , as is generally known in the art. In one example, the seat back  16  includes a first end  20  and a second end  22 . The first end  20  is movably coupled to the seat bottom  14 , and the second end  22  may be coupled to a headrest  24  for supporting an occupant&#39;s head. It should be noted that the seat  12  is merely exemplary, and thus, the seat  12  need not include a headrest  24 . 
         [0015]    The active seat damper system  18  is coupled to the seat  12 . In one example, the active seat damper system  18  includes at least one sensor  26 , a damper  28  and a control module  30 . In one embodiment, the active seat damper system  18  includes one or more mass sensors  26 ′. The one or more mass sensors  26 ′ measure and observe a mass of an item seated on the seat bottom  14  and generate sensor signals based thereon. Generally, the one or more mass sensors  26 ′ measure and observe any mass positioned upon the seat bottom  14 , and thus, the one or more mass sensors  26 ′ may generate sensor signals that indicate that an occupant is seated in the seat  12  or if the seat  12  is unoccupied based on the observed mass. It should be noted that while the one or more mass sensors  26 ′ are illustrated as being coupled to the seat bottom  14 , the one or more mass sensors  26 ′ may be coupled to the seat  12  at any desired location to measure a mass associated with the seat  12 , including, but not limited to, the seat back  16 . 
         [0016]    In one embodiment, the at least one sensor  26  includes one or more acceleration sensors or accelerometers  26 ″. The one or more accelerometers  26 ″ measure and observe an acceleration of the seat  12  and generate sensor signals based thereon. Generally, the one or more accelerometers  26 ″ measure an absolute acceleration observed by the one or more accelerometers  26 ″. In one example, the one or more accelerometers  26 ″ are coupled to the headrest  24 , however, the one or more accelerometers  26 ″ may be coupled to the seat  12  at any desired location to observe an acceleration associated with the seat  12 . In addition, the one or more accelerometers  26 ″ may be coupled to any portion of the vehicle  10  to measure an acceleration of the vehicle  10  and generate sensor signals based thereon. Thus, the location of the one or more accelerometers  26 ″ is merely exemplary. In addition, it should be noted that the sensors  26 ′,  26 ″ are merely exemplary, as any number of sensors  26  could be employed and further, one or more of the conditions measured by the sensors  26 ′,  26 ″ can be derived from other sources, such as by modeling, for example. 
         [0017]    The damper  28  is coupled to the seat  12 . The damper  28  is adjustable or tunable based upon receipt of one or more control signals from the control module  30  to vary a natural frequency of the damper  28 , and thus, the seat  12 , as will be discussed in greater detail herein. In one example, the damper  28  is coupled to the seat back  16 , however, the damper  28  may be coupled to any desired portion of the seat  12  to influence a natural frequency or vibration behavior of the seat  12 . The damper  28  comprises any suitable adjustable or tunable damper, in which the natural frequency of the damper is variable based on receipt of one or more control signals, including, but not limited to, a magnetorheological damper, tuned mass damper or a tuned vibration absorber. Generally, the natural frequency of the damper  28  is adjustable between a minimum natural frequency, such as about 1.5 Hertz (Hz) for example, and a maximum natural frequency, such as about 4 Hertz (Hz), for example. By adjusting the natural frequency of the damper  28 , the natural frequency of the seat  12  may be tuned or varied to correspond with a mass of an item, such as an occupant, seated in the seat  12 , or if unoccupied, to correspond with the mass of the seat  12  itself. By varying or tuning the natural frequency of the damper  28  to correspond with a condition or mass associated with the seat  12 , vibrations associated with the seat  12  during the operation of the vehicle  10  may be minimized, thereby improving operator satisfaction. 
         [0018]    In various embodiments, the control module  30  controls the operation of the damper  28  based on one or more of the sensor signals and further based on the active seat damper systems and methods of the present disclosure to mitigate vibration experienced by the seat  12  of the vehicle  10 . As will be discussed, the control module  30  outputs one or more control signals to the damper  28  to adjust a natural frequency of the damper  28  based on the sensor signals from the at least one sensor  26 . It should be noted that the control module  30  is in communication with the at least one sensor  26  and damper  28  over any suitable communication architecture associated with the vehicle  10 . 
         [0019]    Referring now to  FIG. 2 , and with continued reference to  FIG. 1 , a dataflow diagram illustrates various embodiments of a damper control system  100  for the seat  12  ( FIG. 1 ) that may be embedded within the control module  30 . Various embodiments of the damper control system according to the present disclosure can include any number of sub-modules embedded within the control module  30 . As can be appreciated, the sub-modules shown in  FIG. 2  can be combined and/or further partitioned to similarly adjust the natural frequency of the damper  28  of the active seat damper system  18  ( FIG. 1 ). Inputs to the system can be sensed from the vehicle  10  ( FIG. 1 ), received from other control modules (not shown), and/or determined/modeled by other sub-modules (not shown) within the control module  30 . In various embodiments, the control module  30  includes a damper control module  102  and a tables datastore  104 . 
         [0020]    In one embodiment, the tables datastore  104  stores one or more tables (e.g., lookup tables) that indicate a natural frequency for the damper  28  based on the mass input to the one or more mass sensors  26 ′ and a known mass of the seat  12 . In other words, the tables datastore  104  stores one or more tables that provide natural frequency values for the damper  28  based on various masses of the seat system observed by the one or more mass sensors  26 ′ and the known mass of the seat  12 . In one example, the one or more tables are populated using the following equation: 
         [0000]    
       
         
           
             
               
                 
                   M 
                   = 
                   
                     
                       1 
                       
                         4 
                          
                         
                           π 
                           2 
                         
                       
                     
                      
                     
                       ( 
                       
                         
                           K 
                           system 
                         
                         
                           Z 
                           2 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0021]    Wherein, M is the sum of the known mass of the seat  12  and the mass observed by the one or more mass sensors  26 ′ in kilograms (kg) multiplied by a correlation coefficient (no units) for a percent of a mass measured by the one or more mass sensors  26 ′ that acts on the seat back  16  (the effective mass); K system  is the stiffness of the seat system comprising of the seat  12  and damper  28  in Newtons per meter (N/m); and Z is the natural frequency of the seat system that the damper  28  will be set to in Hertz (Hz). 
         [0022]    In various embodiments, the tables can be interpolation tables that are defined by one or more indexes. A natural frequency value  106  provided by at least one of the tables indicates a desired natural frequency for the damper  28  to arrive at a natural frequency for the seat  12  based on the mass input. As an example, one or more tables can be indexed by parameters such as, but not limited to, mass of an occupant on the seat  12  and the seat  12  itself, to provide the natural frequency value  106 . Thus, the natural frequency value  106  indicates a natural frequency for the damper  28  based on a particular mass observed by the one or more mass sensors  26 ′. 
         [0023]    In one embodiment, the tables datastore  104  stores one or more tables (e.g., lookup tables) that indicate a natural frequency for the damper  28  based on the acceleration input to the one or more accelerometers  26 ″. In other words, the tables datastore  104  stores one or more tables that provide natural frequency values for the damper  28  based on various accelerations observed by the one or more accelerometers  26 ″. In various embodiments, the tables can be interpolation tables that are defined by one or more indexes. The natural frequency value  106  provided by at least one of the tables indicates a desired natural frequency for the damper  28  to arrive at a natural frequency for the seat  12  based on the acceleration input. As an example, one or more tables can be indexed by parameters such as, but not limited to, the frequency of peak acceleration of the seat  12 , to provide the natural frequency value  106 . In this example, the natural frequency values for the damper  28  correspond directly to a measured frequency of a peak acceleration by the one or more accelerometers  26 ″. For example, the one or more tables are populated using the following equation: 
         [0000]    
       
         
           
             
               
                 
                   
                     Z 
                     damper 
                   
                   = 
                   
                     
                       1 
                       
                         2 
                          
                         π 
                       
                     
                      
                     
                       AZ 
                       accel 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0024]    Wherein, Z damper  is the frequency of the damper in Hertz (Hz), A is a correlation coefficient (no units) and Z accel  is the frequency of the peak acceleration in Hertz (Hz). In one example, A is about 1.0 or less. Thus, the natural frequency value  106  indicates a natural frequency for the damper  28  based on a particular acceleration observed by the one or more accelerometers  26 ″. 
         [0025]    The damper control module  102  receives as input sensor data  108  from at least one sensor  26 . The sensor data  108  indicates one or more conditions associated with the seat  12 . The damper control module  102  generates one or more control signals  114  to the damper  28  based on the sensor data  108 . In various embodiments, the damper control module  102  receives mass data  110  from the one or more mass sensors  26 ′. Based on the mass data  110 , the damper control module  102  determines if the seat  12  is occupied or unoccupied. For example, if the mass data  110  is greater than a mass of the seat  12 , then the damper control module  102  determines that the seat  12  is occupied. If the seat  12  is unoccupied, the damper control module  102  determines the natural frequency value  106  to be a maximum natural frequency value. 
         [0026]    The damper control module  102  also determines, based on the mass data  110 , if the mass data  110  is greater than a predefined threshold for an occupant mass on the seat  12 . For example, the damper control module  102  determines if the mass data  110  indicates that the occupant mass is greater than a 95 th  percentile for occupant mass. If the mass data  110  is greater than the predefined threshold, the damper control module  102  determines the natural frequency value  106  to be a minimum natural frequency value. 
         [0027]    If the mass data  110  is below the predefined threshold and the seat  12  is occupied, the damper control module  102  determines the natural frequency value  106  from the one or more tables of the tables datastore  104  based on the mass data  110  (e.g., by performing a lookup function on the tables to determine a natural frequency value using the mass observed by the one or more mass sensors  26 ′ and the known mass of the seat  12 ). A natural frequency of the seat  12  is determined from the mass data  110 . For example, the damper control module  102  determines a natural frequency of the seat  12  based on the following equation: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       1 
                       
                         2 
                          
                         π 
                       
                     
                      
                     
                       ( 
                       
                         
                           
                             K 
                             seat 
                           
                           M 
                         
                       
                       ) 
                     
                   
                   = 
                   Z 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
         [0028]    Wherein, M is the sum of the known mass of the seat  12  and the mass observed by the one or more mass sensors  26 ′ (i.e. mass data  110 ) in kilograms (kg) multiplied by a correlation coefficient (no units) for a percent of a mass measured by the one or more mass sensors  26 ′ that acts on the seat back  16  (the effective mass); K seat  is the known stiffness of the seat  12  in Newtons per meter (N/m); and Z is the natural frequency of the of the seat  12  in Hertz (Hz). Based on the natural frequency of the seat  12 , the damper control module  102  outputs the one or more control signals  114  to adjust the natural frequency of the damper  28  to create an equivalent natural frequency of the damper  28 , thereby reducing vibrations associated with the seat  12 . 
         [0029]    In various embodiments, the damper control module  102  receives acceleration data  112  from the one or more accelerometers  26 ″. The damper control module  102  determines if the acceleration data  112  is greater than a predefined threshold for acceleration. In one embodiment, the damper control module  102  receives an absolute acceleration measured and observed by the one or more accelerometers  26 ″ and determines if the absolute acceleration measured and observed by the one or more accelerometers  26 ″ is greater than the predefined threshold. 
         [0030]    In one embodiment, if two accelerometers  26 ″ are employed with the damper control system  18 , the damper control module  102  receives the absolute acceleration measured and observed by each of the accelerometers  26 ″ and determines if the difference between the two values (i.e. the relative acceleration between the two accelerometers  26 ″) is greater than the predefined threshold. For example, the damper control module  102  determines if the acceleration is greater than about 0.1 meters per second squared (m/s 2 ). It should be noted that this predefined threshold is merely exemplary, as the predefined threshold may vary based on the speed of the vehicle  10  and/or an operating condition of the vehicle  10 , such as between about 0.1 m/s 2  or about 1.0 m/s 2 . If the acceleration data  112  is greater than the predefined threshold, the damper control module  102  determines the natural frequency value  106  from the one or more tables of the tables datastore  104  based on the acceleration data  112  (e.g., by performing a lookup function on the tables to determine a natural frequency value using the acceleration observed by the one or more accelerometers  26 ″). The one or more control signals  114  are generated to the damper  28  based on the acceleration data  112  to control the natural frequency of the damper  28  based on the current acceleration associated with the seat  12  (i.e. the acceleration of the seat  12  observed by the one or more accelerometers  26 ″). 
         [0031]    It should be noted that if the acceleration data  112  is less than the predefined threshold, the natural frequency for the damper  28  may be set to a predefined or default value and/or may be determined based on the mass data  110 , as discussed previously herein. 
         [0032]    Referring now to  FIG. 3 , and with continued reference to  FIGS. 1 and 2 , a flowchart illustrates a control method that can be performed by the control module  30  of  FIG. 1  in accordance with the present disclosure. As can be appreciated in light of the disclosure, the order of operation within the method is not limited to the sequential execution as illustrated in  FIG. 3 , but may be performed in one or more varying orders as applicable and in accordance with the present disclosure. 
         [0033]    In various embodiments, the method can be scheduled to run based on predetermined events, and/or can run continually during operation of the vehicle  10 . 
         [0034]    The method begins at  200 . At  202 , the method can receive the mass data  110  from the one or more mass sensors  26 ′. Based on the mass data  110 , at  204 , the method determines if the seat  12  is occupied or unoccupied. In other words, if the mass data  110  indicates a mass measured greater than a mass of the seat  12 , then the method determines that the seat  12  is occupied. If the seat  12  is occupied, the method goes to  206 . Otherwise, the method goes to  208 . 
         [0035]    At  208 , the method sets the natural frequency value for the damper  28  as a maximum natural frequency value based on the seat  12  being unoccupied. In one example, the maximum natural frequency value is a default value. At  209 , the method determines the natural frequency for the seat  12  using the equation (3) from above. At  210 , based on the natural frequency of the seat  12 , the method outputs the one or more control signals  114  to adjust the natural frequency of the damper  28  to create an equivalent natural frequency of the damper  28 , thereby reducing vibrations associated with the seat  12 . Then, the method ends at  212 . 
         [0036]    At  206 , the method determines if the mass data  110  is greater than a predefined threshold for an occupant mass on the seat  12 . For example, the method determines if the mass data  110  indicates that the occupant mass is greater than a 95 th  percentile for occupant mass. If the mass data  110  is greater than the predefined threshold, the method goes to  214 . Otherwise, at  216 , the method determines the natural frequency value  106  from the tables of the tables datastore  104  based on the mass data  110  and the seat mass (known value). At  209 , the natural frequency of the seat  12  is determined based on the mass data  110  and the seat mass using equation (3). 
         [0037]    At  214 , the method determines the natural frequency value  106  is a minimum natural frequency value for the damper  28  based on the occupant mass from the mass data  110  being greater than the predefined threshold. In one example, the minimum natural frequency value is a default value. At  209 , the natural frequency of the seat  12  is determined based on the mass data  110  and the seat mass using equation (3). 
         [0038]    It should be noted that blocks  206 ,  216 ,  218  may be optional, as the method can adjust the natural frequency of the seat  12 , and thus the damper  28 , based on whether the seat  12  is occupied or unoccupied from the mass data  110 . Thus, the method illustrated herein is merely exemplary. 
         [0039]    Referring now to  FIG. 4 , and with continued reference to  FIGS. 1 and 2 , a flowchart illustrates a control method that can be performed by the control module  30  of  FIG. 1  in accordance with the present disclosure. As can be appreciated in light of the disclosure, the order of operation within the method is not limited to the sequential execution as illustrated in  FIG. 4 , but may be performed in one or more varying orders as applicable and in accordance with the present disclosure. 
         [0040]    In various embodiments, the method can be scheduled to run based on predetermined events, and/or can run continually during operation of the vehicle  10 . 
         [0041]    The method begins at  300 . At  302 , the method can receive the acceleration data  112  from the one or more accelerometers  26 ″. At  304 , the method determines if the acceleration data  112  is greater than a predefined threshold for acceleration. For example, the method determines if the acceleration is greater than about 0.1 m/s 2 . If the acceleration data  112  is not greater than the predefined threshold, the method goes to  306 . At  306 , the method waits a predetermined time period, such as about 10 seconds to about 25 seconds, before looping to  302 . 
         [0042]    Otherwise, if the acceleration data  112  is greater than the predefined threshold, the method goes to  308 . At  308 , the method determines the natural frequency value  106  from the tables of the tables datastore  104  based on the acceleration data  112 . At  310 , the natural frequency of the seat  12  is determined based on the natural frequency value  106  derived from the acceleration data  112 . At  312 , based on the natural frequency of the seat  12 , the method outputs the one or more control signals  114  to adjust the natural frequency of the damper  28  to create an equivalent natural frequency of the damper  28 , thereby reducing vibrations associated with the seat  12 . Then, the method ends at  314 . 
         [0043]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.