Abstract:
Methods, systems, and vehicles are provided for controlling a direction of a vehicle using aerodynamic forces. A rudder is positioned on a body of the vehicle. A control system is coupled to the rudder, and comprises a detection unit and a processor. The detection unit is configured to obtain sensor data for the vehicle. The processor is coupled to the detection unit, and is configured to at least facilitate obtaining a measured yaw rate for the vehicle using the sensor data, determining an intended yaw rate for the vehicle using the sensor data, and moving the rudder based at least in part on a comparison between the measured yaw rate and the intended yaw rate.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to vehicles, and more particularly relates to methods and systems for controlling vehicle direction using aerodynamic forces. 
       BACKGROUND 
       [0002]    Many vehicles today utilize techniques for direction control. For example, in situations in which a vehicle may be experiencing understeer or oversteer conditions, certain vehicles today may implement stability control braking intervention and/or electronic limited slip differential to correct the understeer or oversteer conditions. However, such existing techniques may not always be optimal in all situations, for example because such techniques may slow down the vehicle. 
         [0003]    Accordingly, it is desirable to provide improved techniques for direction control, for example when a vehicle may be experiencing an understeer or oversteer condition. It is also desirable to provide methods, systems, and vehicles utilizing such techniques. Furthermore, other desirable features and characteristics of the present invention will be 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 accordance with an exemplary embodiment, a method is provided. The method comprises obtaining a measured yaw rate for a vehicle, determining an intended yaw rate for the vehicle, and moving a rudder of the vehicle, via instructions provided by a processor, based at least in part on a comparison between the measured yaw rate and the intended yaw rate. 
         [0005]    In accordance with an exemplary embodiment, a system is provided. The system comprises a detection unit and a processor. The detection unit is configured to obtain sensor data for a vehicle. The processor is coupled to the detection unit, and is configured to at least facilitate obtaining a measured yaw rate for the vehicle using the sensor data, determining an intended yaw rate for the vehicle using the sensor data, and moving a rudder of the vehicle based at least in part on a comparison between the measured yaw rate and the intended yaw rate. 
         [0006]    In accordance with a further exemplary embodiment, a vehicle is provided. The vehicle comprises a body, a rudder, and a control system. The rudder is positioned on the body. The control system is coupled to the rudder, and comprises a detection unit and a processor. The detection unit is configured to obtain sensor data for the vehicle. The processor is coupled to the detection unit, and is configured to at least facilitate obtaining a measured yaw rate for the vehicle using the sensor data, determining an intended yaw rate for the vehicle using the sensor data, and moving the rudder based at least in part on a comparison between the measured yaw rate and the intended yaw rate. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
           [0008]      FIG. 1  is a functional block diagram of a vehicle that includes a rudder and a control system for controlling the runner, for use in controlling vehicle direction (e.g. yaw rate, understeer, and oversteer) using aerodynamic forces, in accordance with an exemplary embodiment; 
           [0009]      FIG. 2  is a flowchart of a process for controlling vehicle direction using aerodynamic forces, and that can be used in conjunction with the vehicle of  FIG. 1 , in accordance with an exemplary embodiments; 
           [0010]      FIG. 3  is a schematic drawing of an implementation of the process of  FIG. 2  in correcting oversteer or understeer of a vehicle, such as the vehicle of  FIG. 1 , in accordance with an exemplary embodiment; and 
           [0011]      FIGS. 4-6  are schematic drawings showing a vehicle with a rudder that is configured and moved between multiple positions for controlling vehicle direction using aerodynamic forces, and that can be used in conjunction with the vehicle of  FIG. 1 , the process of  FIG. 2 , and the implementation of  FIG. 3 , in accordance with an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The following detailed description is merely exemplary in nature and is not intended to limit the disclosure or the application and uses thereof. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
         [0013]      FIG. 1  illustrates a vehicle  100 , or automobile, according to an exemplary embodiment. As described in greater detail further below, the vehicle  100  includes a rudder  101 , along with a control system  102  for the rudder  101 , for controlling vehicle direction using aerodynamic forces. In various embodiments, the vehicle  100  comprises a land vehicle. In certain preferred embodiments, the vehicle  100  comprises an automotive vehicle, such as an automobile, truck, bus, and/or sedan as driven on highways, roads, and/or other roadways. 
         [0014]    In one embodiment, the rudder  101  is disposed on a rear portion of the vehicle  100 , for example where a spoiler would typically be placed. Also in one embodiment, in one embodiment, the rudder  101  is mounted along a bumper beam  111  of the vehicle  100 . However, this may vary in other embodiments. 
         [0015]    The control system  102  selectively moves the rudder  101  between different positions to utilize aerodynamic forces to correct understeer and oversteer for the vehicle  100 , based on the vehicle  100 &#39;s actual yaw rate, a driver&#39;s intended yaw rate for the vehicle  100 , and a speed of the vehicle  100 , in accordance with the steps of the process  200  of  FIG. 2 , as discussed further below. Examples of the placement and positional movement of the rudder  101  are further illustrated in  FIGS. 4-6  and discussed further below in connection therewith, as well as in connection with the discussion of  FIGS. 2 and 3  further below. In addition, as discussed further below in connection with  FIG. 1 , in the depicted embodiment the control system  102  includes a sensor array  103 , a controller  104 , and an actuator  105 . 
         [0016]    As depicted in  FIG. 1 , the vehicle  100  includes, in addition to the above-referenced rudder  101  and control system  102 , a chassis  112 , a body  114 , four wheels  116 , an electronic control system  118 , a steering system  150 , and a braking system  160 . The body  114  is arranged on the chassis  112  and substantially encloses the other components of the vehicle  100 . The body  114  and the chassis  112  may jointly form a frame. The wheels  116  are each rotationally coupled to the chassis  112  near a respective corner of the body  114 . In various embodiments the vehicle  100  may differ from that depicted in  FIG. 1 . For example, in certain embodiments the number of wheels  116  may vary. 
         [0017]    In the exemplary embodiment illustrated in  FIG. 1 , the vehicle  100  includes an actuator assembly  120 . The actuator assembly  120  includes at least one propulsion system  129  mounted on the chassis  112  that drives the wheels  116 . In the depicted embodiment, the actuator assembly  120  includes an engine  130 . In one embodiment, the engine  130  comprises a combustion engine. In other embodiments, the actuator assembly  120  may include one or more other types of engines and/or motors, such as an electric motor/generator, instead of or in addition to the combustion engine. 
         [0018]    Still referring to  FIG. 1 , the engine  130  is coupled to at least some of the wheels  116  through one or more drive shafts  134 . In some embodiments, the engine  130  is mechanically coupled to the transmission. In other embodiments, the engine  130  may instead be coupled to a generator used to power an electric motor that is mechanically coupled to the transmission. In certain other embodiments (e.g. electrical vehicles), an engine and/or transmission may not be necessary. 
         [0019]    The steering system  150  is mounted on the chassis  112 , and controls steering of the wheels  116 . The steering system  150  includes a steering wheel and a steering column (not depicted). The steering wheel receives inputs from a driver of the vehicle  100 . The steering column results in desired steering angles for the wheels  116  via the drive shafts  134  based on the inputs from the driver. 
         [0020]    The braking system  160  is mounted on the chassis  112 , and provides braking for the vehicle  100 . The braking system  160  receives inputs from the driver via a brake pedal (not depicted), and provides appropriate braking via brake units (also not depicted). The driver also provides inputs via an accelerator pedal (not depicted) as to a desired speed or acceleration of the vehicle, as well as various other inputs for various vehicle devices and/or systems, such as one or more vehicle radios, other entertainment systems, environmental control systems, lighting units, navigation systems, and the like (also not depicted). Similar to the discussion above regarding possible variations for the vehicle  100 , in certain embodiments steering, braking, and/or acceleration can be commanded by a computer instead of by a driver. 
         [0021]    The control system  102  is mounted on the chassis  112 . As discussed above, the control system  102  estimates movement of the vehicle  100  using radar data with respect to stationary objects in proximity to the vehicle  100 , and includes a sensor array  103  and a controller  104 . 
         [0022]    The sensor array  103  includes various sensors (also referred to herein as sensor units) that are utilized by the control system  102  for controlling direction for the vehicle  100  via movement of the rudder  101 . In the depicted embodiment, the sensor array  103  includes one or more vehicle ignition sensors  162 , steering sensors  163 , speed sensors  164 , and yaw sensors  166 . The ignition sensors  162  detect whether an ignition system of the vehicle  100  is on or off. The steering sensors  163  are used for measuring a steering angle for the steering system  150  of the vehicle  100  (e.g. an angle of the steering wheel and/or steering column of the vehicle  100 ). The speed sensors  164  are used to measure a speed of the vehicle and/or data used for calculating the wheel speed (e.g. wheel speed sensors  164  for measuring wheel speed for use by the controller  104  in calculating the vehicle speed, in one embodiment). The yaw sensors  166  measure a yaw rate of the vehicle  100 . The measurements and information from the various sensors of the sensor array  103  are provided to the controller  104  for processing. 
         [0023]    The controller  104  is coupled, directly or indirectly, to the rudder  101 , and controls movement of the rudder  101  based on the data from the sensor array  103 , for controlling direction of the vehicle  100  (e.g. to correct an understeer or oversteer condition). In the depicted embodiment, the controller  104  is coupled to the sensor array  103  and to the actuator  105 . The actuator  105  moves the rudder  101  based on instructions provided by the controller  104 . In one embodiment, the actuator  105  comprises an electric actuator. In another embodiment, the actuator  105  comprises a hydraulic actuator. However, this may vary in other embodiments. 
         [0024]    As indicated above, the controller  104  utilizes the various measurements and information from the sensor array  103  for controlling movement of the rudder  101  via instructions provided to the actuator  105 , for controlling direction of the vehicle  100  using aerodynamic forces (e.g. to correct an understeer or oversteer condition). Specifically, the controller  104  determines an actual yaw rate of the vehicle  100  (e.g., from the data provided by the yaw sensors  166 ) as well as a driver intended yaw rate for the vehicle  100  (e.g., from the data provided by the steering sensors  163 ), and controls the rudder  101  based on a comparison of the actual versus driver intended yaw rates (and, in certain embodiments, based on one or more other parameters, such as a speed of the vehicle, for example as determined provided by the speed sensors  164 ). In certain embodiments, the controller  104 , along with the rudder  101 , the sensor array  103 , and the actuator  105  provide these and other functions in accordance with the process  200  described further below in connections with  FIGS. 2-6 . 
         [0025]    As depicted in  FIG. 1 , the controller  104  comprises a computer system. In certain embodiments, the controller  104  may also include one or more of the sensors of the sensor array  103 , one or more other devices and/or systems, and/or components thereof. In addition, it will be appreciated that the controller  104  may otherwise differ from the embodiment depicted in  FIG. 1 . For example, the controller  104  may be coupled to or may otherwise utilize one or more remote computer systems and/or other control systems, such as the electronic control system  118  of  FIG. 1 . 
         [0026]    In the depicted embodiment, the computer system of the controller  104  includes a processor  172 , a memory  174 , an interface  176 , a storage device  178 , and a bus  180 . The processor  172  performs the computation and control functions of the controller  104 , and may comprise any type of processor or multiple processors, single integrated circuits such as a microprocessor, or any suitable number of integrated circuit devices and/or circuit boards working in cooperation to accomplish the functions of a processing unit. During operation, the processor  172  executes one or more programs  182  contained within the memory  174  and, as such, controls the general operation of the controller  104  and the computer system of the controller  104 , generally in executing the processes described herein, such as the process  200  described further below in connection with  FIGS. 2-6 . 
         [0027]    The memory  174  can be any type of suitable memory. For example, the memory  174  may include various types of dynamic random access memory (DRAM) such as SDRAM, the various types of static RAM (SRAM), and the various types of non-volatile memory (PROM, EPROM, and flash). In certain examples, the memory  174  is located on and/or co-located on the same computer chip as the processor  172 . In the depicted embodiment, the memory  174  stores the above-referenced program  182  along with one or more stored values  184  (e.g., a stored model and/or other values) for use in executing the functions of the controller  104 . 
         [0028]    The bus  180  serves to transmit programs, data, status and other information or signals between the various components of the computer system of the controller  104 . The interface  176  allows communication to the computer system of the controller  104 , for example from a system driver and/or another computer system, and can be implemented using any suitable method and apparatus. In one embodiment, the interface  176  obtains the various data from the sensors of the sensor array  103 . The interface  176  can include one or more network interfaces to communicate with other systems or components. The interface  176  may also include one or more network interfaces to communicate with technicians, and/or one or more storage interfaces to connect to storage apparatuses, such as the storage device  178 . 
         [0029]    The storage device  178  can be any suitable type of storage apparatus, including direct access storage devices such as hard disk drives, flash systems, floppy disk drives and optical disk drives. In one exemplary embodiment, the storage device  178  comprises a program product from which memory  174  can receive a program  182  that executes one or more embodiments of one or more processes of the present disclosure, such as the steps of the process  200  (and any sub-processes thereof) described further below in connection with  FIGS. 2-6 . In another exemplary embodiment, the program product may be directly stored in and/or otherwise accessed by the memory  174  and/or a disk (e.g., disk  186 ), such as that referenced below. 
         [0030]    The bus  180  can be any suitable physical or logical means of connecting computer systems and components. This includes, but is not limited to, direct hard-wired connections, fiber optics, infrared and wireless bus technologies. During operation, the program  182  is stored in the memory  174  and executed by the processor  172 . 
         [0031]    It will be appreciated that while this exemplary embodiment is described in the context of a fully functioning computer system, those skilled in the art will recognize that the mechanisms of the present disclosure are capable of being distributed as a program product with one or more types of non-transitory computer-readable signal bearing media used to store the program and the instructions thereof and carry out the distribution thereof, such as a non-transitory computer readable medium bearing the program and containing computer instructions stored therein for causing a computer processor (such as the processor  172 ) to perform and execute the program. Such a program product may take a variety of forms, and the present disclosure applies equally regardless of the particular type of computer-readable signal bearing media used to carry out the distribution. Examples of signal bearing media include: recordable media such as floppy disks, hard drives, memory cards and optical disks, and transmission media such as digital and analog communication links. It will be appreciated that cloud-based storage and/or other techniques may also be utilized in certain embodiments. It will similarly be appreciated that the computer system of the controller  104  may also otherwise differ from the embodiment depicted in  FIG. 1 , for example in that the computer system of the controller  104  may be coupled to or may otherwise utilize one or more remote computer systems and/or other control systems. 
         [0032]    While the sensor array  103 , the controller  104 , and that actuator  105  are depicted as being part of the same system, it will be appreciated that in certain embodiments these features may comprise two or more systems. In addition, in various embodiments the control system  102  may comprise all or part of, and/or may be coupled to, various other vehicle devices and systems, such as, among others, the rudder  101 , the bumper beam  111 , the actuator assembly  120 , the electronic control system  118 , and/or the steering system  150 . 
         [0033]      FIG. 2  is a flowchart of a process  200  for controlling vehicle direction using aerodynamic forces, in accordance with an exemplary embodiment. The process  200  can be implemented in connection with the vehicle  100 , including the rudder  101  and the control system  102  thereof, in accordance with one embodiment. In addition, the process  200  is also discussed below in connection with  FIG. 3  (which provides an exemplary implementation of the process  200  in correcting an understeer or oversteer condition) as well as  FIGS. 4-6  (which provide illustrations of exemplary positional movements of the rudder to control vehicle direction in accordance with the steps of the process  200  of  FIG. 2 ), in accordance with exemplary embodiments. 
         [0034]    As depicted in  FIG. 2 , the process  200  is initiated at step  202 . In one embodiment, the steps of the process  200  repeat, preferably continuously, throughout an ignition cycle or vehicle drive for the vehicle, in which the vehicle is being operated. 
         [0035]    A determination is made as to whether an ignition of the vehicle is turned on (step  204 ). In one embodiment, this determination is made by the processor  172  of  FIG. 1  based on measurements provided by the ignition sensors  162  of  FIG. 1 . 
         [0036]    If it is determined that the vehicle ignition is not turned on, then the directional control of the process  200  is inactive (step  206 ). In one embodiment, during step  206 , the direction control remains inactive while the determination of step  204  repeats, until a subsequent determination is made in an iteration of step  204  that the vehicle ignition is turned on. 
         [0037]    Once it is determined that the vehicle ignition is turned on, a speed of the vehicle is obtained or determined (step  208 ). In one embodiment, the vehicle speed is determined by the processor  172  of  FIG. 1  using one or more measurements from the speed sensors  164  of  FIG. 1  (e.g. wheel speed sensors). In certain other embodiments, one or more other different types of systems, sensors, and/or techniques may be utilized (e.g., using data from a vehicle accelerometer and/or a global positioning system (GPS)). 
         [0038]    A steering angle is also obtained or determined (step  210 ). In one embodiment, the steering angle is obtained or determined by the processor  172  of  FIG. 1  using one or more measurements from the steering sensors  163  of  FIG. 1 . In one such embodiment, the steering angle comprises a steering wheel angle as measured by a steering wheel sensor. 
         [0039]    A measured yaw rate for the vehicle is obtained or determined (step  212 ). In one embodiment, the measured yaw rate is measured by one or more yaw sensors  166  of  FIG. 1  and provided to the processor  172  of  FIG. 1 . In one embodiment, the measured yaw rate comprises an actual yaw rate for the vehicle as it is being driven during a current ignition cycle or vehicle drive. 
         [0040]    A driver-intended yaw rate is determined (step  214 ). In one embodiment, the driver-intended yaw rate comprises a yaw rate for the vehicle that would correspond to or be consistent with travel of the vehicle in accordance with inputs provided by an operator of the vehicle (e.g., a yaw rate consistent with the driver&#39;s application of the steering wheel). In one embodiment, the driver-intended yaw rate is calculated by the processor  172  of  FIG. 1  based on information provided by the sensor array  103  of  FIG. 1 . In one such embodiment, the processor  172  calculates the driver intended yaw rate using the steering angle of step  210  (e.g. a steering wheel angle) along with a model stored in the memory  174  of  FIG. 1  as one of the stored values  184  thereof (e.g. a vehicle dynamics bicycle model). In one embodiment, the driver&#39;s intended yaw rate is calculated from the steering wheel angle and vehicle speed. In one embodiment, the vehicle&#39;s normal yaw response to a steering input at a particular vehicle speed is characterized through a series of maneuvers to determine an overall response map that encompasses the full range of steering angle and vehicle speed inputs. Also in one embodiment, this response map is then used to determine the driver&#39;s intended yaw response based on steering wheel input and vehicle speed by referencing a calibration table. 
         [0041]    In step  216 , a comparison is made regarding the measured yaw rate of step  212  and the driver intended yaw rate of step  214 . In one embodiment, this comparison is made by the processor  172  of  FIG. 1 . 
         [0042]    If it is determined in step  216  that the measured yaw rate of step  212  is equal to the driver intended yaw rate of step  214  (or, in certain embodiments, that an absolute value of the difference between the measured yaw rate and the driver intended yaw rate is less than a predetermined threshold), then it is determined that the rudder  101  of  FIG. 1  is not presently needed for directional adjustment for the vehicle  100  (step  218 ). In one embodiment, this determination is made by the processor  172  of  FIG. 1 . The rudder  101  is maintained accordingly in a nominal position (step  220 ). In one embodiment, the nominal position is one in which the rudder  101  causes little or no change to the yaw rate for the vehicle  100  (for example, corresponding to the first position  402  depicted in  FIGS. 4-6 , discussed further below). In one embodiment, to the extent that the rudder  101  may have presently been in another position other than the nominal position (e.g. via placement in a prior iteration of step  232 ), then the rudder  101  would then be returned to the nominal position during step  220  (in one embodiment, based on instructions provided by the processor  172  to the actuator  105  of  FIG. 1 ). In one embodiment, the process returns to step  204  and repeats with a new iteration. 
         [0043]    Returning to step  216 , if it is determined in step  216  that the measured yaw rate of step  212  is greater than the driver intended yaw rate of step  214  (or, in certain embodiments, that the measured yaw rate is greater than the driver intended yaw rate by at least a predetermined amount or percentage), then it is determined that the rudder  101  of  FIG. 1  is needed for directional adjustment for the vehicle  100  in the form of yaw dampening (step  222 ) (for example, to correct an oversteer condition for the vehicle  100 ). Specifically, in one embodiment, the rudder  101  of  FIG. 1  is moved toward the second position  502  depicted in  FIG. 5  (discussed further below) to correct for the oversteer condition. In one embodiment, this determination is made by the processor  172  of  FIG. 1 . The process then proceeds to step  226 , discussed further below. 
         [0044]    Conversely, if it is determined in step  216  that the measured yaw rate of step  212  is less than the driver intended yaw rate of step  214  (or, in certain embodiments, that the measured yaw rate is less than the driver intended yaw rate by at least a predetermined amount or percentage), then it is determined that the rudder  101  of  FIG. 1  is needed for directional adjustment for the vehicle  100  in the form of yaw increase or acceleration (step  224 ) (for example, to correct an understeer condition for the vehicle  100 ). Specifically, in one embodiment, the rudder  101  of  FIG. 1  is moved toward the third position  602  depicted in  FIG. 6  to correct for the understeer condition. In one embodiment, this determination is made by the processor  172  of  FIG. 1 . The process then proceeds to step  226 , discussed directly below. 
         [0045]    During step  226 , a gain factor is determined for the adjustment of the rudder in implementing the determination of step  222  or step  224 . Specifically, in one embodiment, the gain factor determines a magnitude of the adjustment from step  222  (i.e., the magnitude of the yaw dampening to correct an oversteer condition of step  222 ) or step  224  (i.e., the magnitude of the yaw increase or acceleration to correct an understeer condition of step  224 ). In one embodiment, the gain factor is determined by the processor  172  of  FIG. 1  using a calibration table that is stored in the memory  174  of  FIG. 1  in the stored values  184  thereof. 
         [0046]    Also in one embodiment, the vehicle speed is used along with the size of the difference between the measured yaw rate versus the driver intended yaw rate to determine the amount of the gain, as part of the calibration table. In various embodiments, a larger vehicle speed results in a larger gain in step  226 , all other factors being equal (and with a smaller vehicle speed resulting in a relatively smaller gain, other factors held constant). Also in various embodiments, a larger difference between the measured yaw rate versus the driver-intended yaw rate results in a larger gain in step  226 , all other factors being equal (and with a smaller difference resulting in a relatively smaller gain, other factors held constant). 
         [0047]    For example, in one embodiment, a relatively large amount of yaw dampening (e.g. with a relatively larger gain) is provided when the measured yaw rate is significantly greater than the driver intended yaw rate and the vehicle speed is relatively large. Yaw dampening will still be provided, but in a relatively smaller amount (e.g. with a relatively smaller gain) when the measured yaw rate is greater than the driver intended yaw rate by a relatively smaller amount and/or when the vehicle speed is relatively smaller. 
         [0048]    Similarly, in one embodiment, a relatively large amount of yaw rate increase or acceleration (e.g. with a relatively larger gain) is provided when the measured yaw rate is significantly less than the driver intended yaw rate and the vehicle speed is relatively large. Yaw rate increase or acceleration will still be provided, but in a relatively smaller amount (e.g. with a relatively smaller gain) when the measured yaw rate is less than the driver intended yaw rate by a relatively smaller amount (i.e., when the absolute value of the difference between the respective yaw rates is relatively smaller) and/or when the vehicle speed is relatively smaller. 
         [0049]    The rudder  101  of  FIG. 1  is then adjusted in accordance with the determinations of steps  222 - 226 , to thereby control the direction of the vehicle  100  of  FIG. 1  using aerodynamic forces. Specifically, in one embodiment, a rudder position command is generated (step  228 ). In one embodiment, the rudder position command represents a position of the ruder  101  that accomplishes the desired yaw dampening (of step  222 ) or yaw increase or acceleration (of step  224 ) in accordance with the calculated gain (of step  226 ) via the interaction of aerodynamic forces with the rudder  101  in the desired position. In one embodiment, once the desired yaw raw (or driver intended yaw rate) is equivalent to the actual (or measured) yaw rate, the rudder  101  is returned to the nominal position (i.e. the first position  401  of  FIGS. 4-6 , described further below). Also in one embodiment, the rudder position command is generated by the processor  172  of  FIG. 1 . 
         [0050]    In addition, in one embodiment, a determination is made as to a required change in position to move the rudder  101  from its current position to its desired position of step  228 . In one embodiment, this determination is made by the processor  172  of  FIG. 1 . The rudder  101  is then moved to the desired (or commanded) position (step  232 ). In one embodiment, the rudder  101  is moved by the actuator  105  of  FIG. 1  in accordance with instructions provided by the processor  172  of  FIG. 1 . In one embodiment, once the desired yaw raw (or driver intended yaw rate) is equivalent to the actual (or measured) yaw rate, the rudder  101  is returned to the nominal position (i.e. the first position  401  of  FIGS. 4-6 , described further below). 
         [0051]    With reference to  FIG. 3 , a schematic drawing is provided for an implementation of the process  200  of  FIG. 2  in correcting oversteer or understeer of the vehicle, in accordance with an exemplary embodiment. With reference to the schematic illustration  300 , regions  302  and  308  reflect movement of the vehicle  100  with respect to a driver&#39;s intended yaw rate during a first and second portion of a turn, respectively. Region  304  reflects movement of the vehicle  100  with a greater yaw rate than the driver&#39;s intended yaw rate (i.e. vehicle oversteer) during the first portion of the turn. Region  306  reflects movement of the vehicle  100  with a smaller yaw rate than the driver&#39;s intended yaw rate (i.e. vehicle understeer) during the first portion of the turn. 
         [0052]    When the yaw rate is identical (or substantially identical) to the driver&#39;s intended yaw rate, as in region  302 , no adjustment of the rudder  101  is necessary to attain the driver&#39;s intended yaw rate for the second portion of the turn in region  308  (i.e., corresponding to steps  218  and  220  from  FIG. 2 ). When the yaw rate is larger (or significantly larger) than the driver&#39;s intended yaw rate, as in region  304 , the rudder  101  is adjusted so as to dampen the yaw rate, in order to attain the driver&#39;s intended yaw rate for the second portion of the turn in region  308  (i.e., corresponding to steps  222  and  226 - 232  from  FIG. 2 ). Conversely, when the yaw rate is smaller (or significantly smaller) than the driver&#39;s intended yaw rate, as in region  306 , the rudder  101  is adjusted so as to cause an increase or acceleration in the yaw rate to attain the driver&#39;s intended yaw rate for the second portion of the turn in region  308  (i.e., corresponding to steps  224  and  226 - 232  from  FIG. 2 ). 
         [0053]    With reference to  FIGS. 4-6 , schematic drawings are provided for the vehicle  100  of  FIG. 1  with exemplary positions of the rudder  101  of  FIG. 1  for controlling vehicle direction using aerodynamic forces in accordance with the process  200  of  FIG. 2 , in accordance with an exemplary embodiment. Each of  FIGS. 4-6  depict the rudder  101  mounted on the bumper beam  111  of the vehicle  100 , in accordance with the embodiment discussed above. 
         [0054]      FIG. 4  depicts the vehicle  100  of  FIG. 1  in a first condition  401 , in which there is no significant vehicle understeer or oversteer, in accordance with an exemplary embodiment. For example, in one embodiment, the first condition  401  corresponds to straight ahead driving for the vehicle  100 . While the vehicle  100  is experiencing the first condition  401 , the rudder  101  is placed in a first position  402 , namely the above-discussed nominal position (also referred to herein as a “straight position”). In one embodiment, while in the first position  402 , the rudder  101  is parallel to a “front to rear” direction of the vehicle  100  (and, in one embodiment, parallel to the movement of the vehicle  100 ). The first position  402  thus corresponds to the lowest amount of drag caused by the rudder  101  (in comparison to any other position). 
         [0055]      FIG. 5  depicts the vehicle  100  of  FIG. 1  in a second experiencing a vehicle oversteer condition, in accordance with an exemplary embodiment. As depicted in  FIG. 5 , the vehicle  100  begins in the first condition  401  of  FIG. 4  (i.e. no significant oversteer or understeer). However, in  FIG. 5  the vehicle  100  subsequently encounters an oversteer condition  501 . 
         [0056]    While the vehicle  100  is experiencing the oversteer condition  501 , the rudder  101  is placed in a second position  502 . In one embodiment, the rudder  101  is placed in the second position  502  by rotating the rudder  101  in a direction that is opposite to the direction of the turn of the vehicle  100 . For example, in the illustration of  FIG. 5  in which the vehicle  100  is experiencing an oversteer condition while making a left turn, the rudder  101  is rotated to the right to reach the second position  502 , in order to generate yaw damping and a counteracting yaw moment on the vehicle  100 . Similarly, by way of further example, if the vehicle  100  is experiencing an oversteer condition while making a right turn, the rudder  101  is rotated to the left to reach the second position  502 , in order to generate the yaw damping and the counteracting yaw moment on the vehicle  100 . In one embodiment, the rudder  101  forms an approximately forty five degree angle with a rear surface of the vehicle  100  while in the second position  502 . However, this may vary in other embodiments, this may vary. In certain embodiments, the magnitude of the rotation may vary based on the amount of oversteer experienced by the vehicle  100  (e.g. the rudder  101  may be rotated farther based on relatively larger oversteer conditions, and rotated less based on relatively lesser oversteer conditions, in one embodiment). 
         [0057]    Once the vehicle yaw is damped and the directional control is regained to maintain the driver&#39;s intended path for the vehicle  100  (i.e., once the oversteer condition  501  has ended, as depicted in condition  503  for the vehicle  100  in  FIG. 5 ), the rudder  101  is moved back to its nominal (or straight) position  402 . 
         [0058]      FIG. 6  depicts the vehicle  100  of  FIG. 1  in a second experiencing a vehicle understeer condition, in accordance with an exemplary embodiment. As depicted in  FIG. 6 , the vehicle  100  begins in the first condition  401  of  FIG. 4  (i.e. no significant oversteer or understeer). However, in  FIG. 6  the vehicle  100  subsequently encounters an understeer condition  601 . 
         [0059]    While the vehicle  100  is experiencing the understeer condition  601 , the rudder  101  is placed in a third position  602 . In one embodiment, the rudder  101  is placed in the third position  602  by rotating the rudder  101  in the same direction as the direction of the turn of the vehicle  100 . For example, in the illustration of  FIG. 6  in which the vehicle  100  is experiencing an understeer condition while making a left turn, the rudder  101  is rotated to the left to reach the third position  602 , in order to generate yaw acceleration on the vehicle  100 . Similarly, by way of further example, if the vehicle  100  is experiencing an understeer condition while making a right turn, the rudder  101  is rotated to the right to reach the third position  602 , in order to generate the yaw acceleration on the vehicle  100 . In one embodiment, the rudder  101  forms an approximately forty five degree angle with a rear surface of the vehicle  100  while in the third position  602 . However, this may vary in other embodiments, this may vary. In certain embodiments, the magnitude of the rotation may vary based on the amount of understeer experienced by the vehicle  100  (e.g. the rudder  101  may be rotated farther based on relatively larger understeer conditions, and rotated less based on relatively lesser understeer conditions, in one embodiment). 
         [0060]    Once the additional vehicle yaw is generated and the directional control is regained to maintain the driver&#39;s intended path for the vehicle  100  (i.e., once the understeer condition  601  has ended, as depicted in condition  603  for the vehicle  100  in  FIG. 6 ), the rudder  101  is moved back to its nominal (or straight) position  402 . 
         [0061]    With further referenced to  FIGS. 4-6 , in one embodiment the entire rudder  101  moves when an oversteer or understeer condition is detected, thereby increasing the surface area available for aerodynamic force reactions and thus increasing the effectiveness of the rudder  101 . Also in one embodiment, the dimensions of the rudder  101  are dependent upon the overall size, mass, and yaw inertia of the vehicle  101  to which it is attached, along with the desired yaw force corrections. In one example, the rudder has a width of approximately 0.5 meters along with a height of 0.5 meters. However, the dimensions of the rudder  101  may vary in different embodiments. In certain embodiments, the rudder  101  may have a relatively larger value for vehicles with a relatively larger yaw inertia, or vehicles for which increased performance may be desired, as compared with vehicles with a relatively smaller yaw inertia or for which increased performance may not be required. Conversely, in certain embodiments, if the yaw inertia of the vehicle is relatively smaller or decreased performance is necessary, then a reduced rudder size (e.g., height, width, and associated area) may be utilized. One example is Newton&#39;s second law equations can be applied to calculate the angular acceleration (yaw acceleration) of a given vehicle. The applicable equation is: 
         [0000]    
       
         
           
             
               α 
               = 
               
                 τ 
                 I 
               
             
             , 
           
         
       
     
         [0000]    in which “α” (alpha) represents angular acceleration, “τ” (tau) represents applied torque from the rudder  101  on the yaw axis of the vehicle  101 , and “I” represents the aforementioned yaw inertia of the vehicle  101 . The force on the rudder  101  is also proportional to the square of the velocity at which the vehicle  101  is operated, therefore the rudder can become particularly effective at correcting vehicle oversteer and understeer conditions at higher velocities of the vehicle  100 . 
         [0062]    It will be appreciated that the disclosed methods, systems, and vehicles may vary from those depicted in the Figures and described herein. For example, the vehicle  100 , the rudder  101 , the control system  102 , and/or various components thereof may vary from that depicted in  FIGS. 1, 4-6  and described in connection therewith. In addition, it will be appreciated that certain steps of the process  200  may vary from those depicted in  FIGS. 2-6  and/or described above in connection therewith. It will similarly be appreciated that certain steps of the method described above may occur simultaneously or in a different order than that depicted in  FIG. 2  and/or described above in connection therewith. 
         [0063]    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 appended claims and the legal equivalents thereof.