Abstract:
Methods and apparatus are provided for controlling a steering assist unit of a vehicle. The method includes receiving sensor data indicating a wheel position of a wheel relative to a frame of the vehicle, and determining a travel limit value for the steering assist unit based at least on the wheel position of the wheel. The method further includes outputting a control signal to control the travel of the steering assist unit based on the travel limit value.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to steering systems for vehicles and more particularly relates to systems and methods for variable steering assist in a motor vehicle. 
       BACKGROUND 
       [0002]    Steering systems generally assist the operator of the vehicle in maneuvering the vehicle during use. Generally, steering systems have a steering assist unit, such as a rack and pinion mechanism, which can have a fixed range of travel. In certain driving conditions, however, it may be desirable to have a greater range of travel for the steering system, such as when parking the vehicle. However, having a greater range of travel may be undesirable when the vehicle is traveling over uneven surfaces. 
         [0003]    Accordingly, it is desirable to provide systems and methods for variable steering assist 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]    A method is provided for controlling a steering assist unit of a vehicle. The method includes receiving sensor data indicating a wheel position of a wheel relative to a frame of the vehicle, and determining a travel limit value for the steering assist unit based at least on the wheel position of the wheel. The method further includes outputting a control signal to control the travel of the steering assist unit based on the travel limit value. 
         [0005]    An apparatus is provided for a steering assist unit control system for a vehicle. The apparatus includes a steering assist unit having a path of travel. The apparatus further includes a steering assist control module that determines a travel limit value for the steering assist unit based on a speed of the vehicle and a wheel position of a wheel of the vehicle. 
     
    
     
       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 a steering system in accordance with various embodiments; 
           [0008]      FIG. 2  is a dataflow diagram illustrating a control system of the steering system in accordance with various embodiments; and 
           [0009]      FIG. 3  is a flowchart illustrating a control method of the steering system in accordance with various embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    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. 
         [0011]    With reference to  FIG. 1 , a vehicle  10  is shown having a steering system  12  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. 
         [0012]    In various embodiments, the steering system  12  includes a hand wheel  14  coupled to a steering shaft  16 . In one exemplary embodiment, the steering system  12  is an electric power steering (EPS) system that further includes a steering assist unit  18  that couples to the steering shaft  16  of the steering system  12  and to tie rods  20 ,  22  of the vehicle  10 . The steering assist unit  18  includes, for example, a rack and pinion steering mechanism (not shown) that may be coupled through the steering shaft  16  to a steering actuator motor and gearing (hereinafter referred to as the steering actuator). During operation, as the hand wheel  14  is turned by a vehicle operator, the motor of the steering assist unit  18  provides the assistance to move the tie rods  20 ,  22  which in turn moves steering knuckles  24 ,  26 , respectively, coupled to roadway wheels  28 ,  30 , respectively of the vehicle  10 . Although an EPS system is illustrated in  FIG. 1  and described herein, it is appreciated that the steering system  12  of the present disclosure can include various controlled steering systems including, but not limited to, steering systems with hydraulic configurations, and steer by wire configurations. 
         [0013]    As shown in  FIG. 1 , the vehicle  10  further includes various sensors  32 ,  34 ,  36  that observe conditions of the steering system  12  and/or of the vehicle  10  and generate sensor signals based the observed conditions. In various embodiments, the sensor  32  is a vehicle speed sensor, the sensor  34  is a first wheel position sensor associated with the wheel  28  and the sensor  36  is a second wheel position sensor associated with the wheel  30 . It should be noted that the sensors  32 ,  34 ,  36  are merely exemplary, as any number of sensors could be employed and further, one or more of the conditions measured by the sensors  32 ,  34 ,  36  can be derived from other sources, such as by modeling, for example. It should also be noted that the vehicle  10  can include various other sensors that detect and measure observable conditions of the steering system  12  and/or of the vehicle  10 , including, but not limited to a yaw angle sensor and a hand wheel angle sensor. 
         [0014]    In one example, the sensors  34 ,  36  are associated with a suspension system  38 ,  39  of the vehicle  10 . As a further example, the sensors  34 ,  36  are associated with a magneto-rheological active shock suspension system, which is in turn associated with each of the wheels  28 ,  30 . Generally, each of the sensors  34 ,  36  detect and measure a position of the respective wheel  28 ,  30  relative to a frame  40  of the vehicle  10 . It should be noted, however, that the sensors  34 ,  36  can be independent wheel position sensors, if desired. 
         [0015]    In various embodiments, a control module  42  controls the operation of the steering system  12  and/or the vehicle  10  based on one or more of the sensor signals and further based on the steering control systems and methods of the present disclosure. Generally speaking, the steering control systems and methods of the present disclosure determine a range of travel for the steering assist unit  18 . In one example, the steering control systems and methods of the present disclosure determine a range of travel for a rack of the steering assist unit  18  based on the vehicle speed (e.g., from the vehicle speed sensor  32 ) and the wheel position (e.g., from the wheel position sensor  34 ,  36 ). According to various embodiments, the control module  42  increases the amount of travel the steering assist unit  18  can move the tie rods,  20 ,  22  if the vehicle is below a predetermined speed and the wheel position is within acceptable limits. Conversely, the control module  42  decreases the amount of travel the the steering assist unit  18  can move the tie rods  20 ,  22  if the vehicle is above the predetermined speed or below the predetermined speed and the wheel position is outside of acceptable limits. It should be noted that the control module  42  is in communication with the sensors  34 ,  36  and steering assist unit  18  over a suitable communication architecture, such as a data bus, associated with the vehicle  10 . 
         [0016]    Referring now to  FIG. 2 , and with continued reference to  FIG. 1 , a dataflow diagram illustrates various embodiments of a steering control system  100  for the steering system ( FIG. 1 ) that may be embedded within the control module  42 . Various embodiments of the steering control system according to the present disclosure can include any number of sub-modules embedded within the control module  42 . As can be appreciated, the sub-modules shown in  FIG. 2  can be combined and/or further partitioned to similarly limit the travel of the rack of the steering system  12  ( 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  42 . In various embodiments, the control module  42  includes a steering travel control module  102  and a travel datastore  104 . 
         [0017]    The travel datastore  104  stores one or more tables (e.g., lookup tables) that indicate an acceptable amount of travel of the steering assist unit  18  along a path of travel associated with the steering assist unit  18 . In other words, the travel datastore  104  stores one or more tables that provide limits for the movement of the steering assist unit  18 . In various embodiments, the tables can be interpolation tables that are defined by one or more indexes. A travel limit value provided by at least one of the tables indicates an amount of travel permitted by the steering assist unit  18 . For example, the amount of travel may be an amount of travel of a rack of the steering assist unit  18 . As a further example, one or more tables can be indexed by vehicle parameters such as, but not limited to, vehicle speed and wheel position, to provide the travel limit. Thus, the travel limit indicates an amount of travel permitted by the steering assist unit  18  based on a particular vehicle speed and wheel position. 
         [0018]    The steering travel control module  102  receives as input vehicle speed data  106  from sensor  32  and wheel position data  108  from sensors  34 ,  36 . The steering travel control module  102  generates a steering assist control signal  110  to the steering assist unit  18  based on the vehicle speed data  106  and wheel position data  108 . In one example, the vehicle speed data  106  and wheel position data  108  are received and a travel limit value  112  is determined from the one or more tables of the travel datastore  104  based on the vehicle speed data  106  and wheel position data  108  (e.g., by performing a lookup function on the tables to determine a travel limit value using the vehicle speed and wheel position). The steering assist control signal  110  is generated to the steering assist unit  18  based on the vehicle speed data  106  and wheel position data  108  to control the travel of the steering assist unit  18  based on the current operation of the vehicle  10 . 
         [0019]    For example, at a predetermined vehicle speed, such as less than about 15 miles per hour (mph) the permitted travel limit for the steering assist unit  18  may be increased so long as the wheel position data  108  is within acceptable limits (i.e. the suspension system  38  is not at full rebound), as the slow movement of the vehicle  10  reduces a risk of collision between neighboring components of the steering system  12 . The increased travel of the steering assist unit  18  thereby reduces the turning radius of the vehicle  10 , which aids in parking the vehicle  10 . If, however, the wheel position data indicates that one or more of the wheels  28 ,  30  are outside of acceptable limits, the travel limit of the steering assist unit  18  is not increased or decreased to prevent damage to the steering system  12 . Thus, the control module  42  adapts the travel limits of the steering assist unit  18  based on the current operating conditions of the vehicle  10 , which aids in the maneuverability of the vehicle  10 , thereby increasing customer satisfaction. Generally, the acceptable travel limits depend on the proximity of neighboring components to the steering system  12 . For example, the acceptable travel limits for the steering system  12  can range from about 86 millimeters (mm) to about 92 mm. In this example, if the wheel position data indicates that one or more of the wheels  28 ,  30  is experiencing jounce due to passing over an uneven surface, the travel limit for the steering system  12  can be reduced from about 92 mm to about 86 mm. 
         [0020]    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  42  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. 
         [0021]    In various embodiments, the method of  FIG. 3  can be scheduled to run based on predetermined events, and/or can run continually during operation of the vehicle  10 . 
         [0022]    The method can begin at  200 . At  202 , the method receives the vehicle speed data  106  and wheel position data  108 . The travel limit value  112  is determined from the tables of the travel datastore  104  based on the vehicle speed data  106  and wheel position data  108  at  204 . The steering assist control signal  110  is generated based on the travel limit value  112  at  240 . Thereafter, the method can end at  206 . 
         [0023]    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.