Abstract:
A method is disclosed for steering a mobile platform, where the method may involve: providing a steering component graspable and rotatable by an operator of the mobile platform from a neutral position to first and second positions; coupling an input shaft to the steering component; coupling an input arm to the input shaft so that rotational movement of the input shaft causes rotational movement of the input arm, the input arm being in the neutral position when the steering component is in the neutral position; supporting an idler arm adjacent the input arm and such that portions of the idler arm and the input arm are in contact when the steering component is in the neutral position; and using a biasing system configured to act on the steering arm and the idler arm to maintain the steering component in the neutral position when no force is being applied by the operator to the steering component, to reduce a backlash generated by at least one of the input arm and the idler arm, but to enable clockwise and counterclockwise motion of the input arm in response to an input from the operator using the steering component.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 11/128,810 filed on May 13, 2005, and presently issued U.S. Pat. No. ______. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to steering systems for mobile platforms, and more particularly to a system and method for forming a zero backlash steering tiller. 
       BACKGROUND 
       [0003]    Various mechanisms may be employed to guide mobile platforms. For example, in a commercial aircraft application, a nose wheel is generally employed to steer the aircraft upon landing. The nose wheel is most typically mechanically coupled to a nose gear. Generally, the nose gear is in turn coupled to a steering mechanism, such as a tiller, in the cockpit for receipt of an input from a pilot. Thus, as the input from the pilot is transferred to the nose gear from the tiller, the nose gear serves to move the nose wheel to guide the aircraft based on the input. 
         [0004]    Generally, most tillers have at least a small degree of backlash which provides undesirable feedback to pilots while steering. This can cause the vehicle to drift off course or provide numerous small inputs to the steering system which can prematurely wear out the system. Accordingly, it is desirable to provide a steering tiller that substantially or completely eliminates the backlash in the steering tiller. 
       SUMMARY 
       [0005]    In one aspect the present disclosure relates to a method for steering a mobile platform. The method may involve: providing a steering component graspable and rotatable by an operator of the mobile platform from a neutral position to first and second positions; coupling an input shaft to the steering component; coupling an input arm to the input shaft so that rotational movement of the input shaft causes rotational movement of the input arm, the input arm being in the neutral position when the steering component is in the neutral position; supporting an idler arm adjacent the input arm and such that portions of the idler arm and the input arm are in contact when the steering component is in the neutral position; and using a biasing system configured to act on the steering arm and the idler arm to maintain the steering component in the neutral position when no force is being applied by the operator to the steering component, to reduce a backlash generated by at least one of the input arm and the idler arm, but to enable clockwise and counterclockwise motion of the input arm in response to an input from the operator using the steering component. 
         [0006]    In another aspect the present disclosure may involve a method for steering a mobile platform. The method may involve: providing a steering handle graspable and rotatable by an operator of the mobile platform from a neutral position in clockwise and counterclockwise directions to first and second positions; coupling an input shaft to the steering handle; coupling an input arm to the input shaft so that rotational movement of the input shaft causes rotational movement of said input arm, the input arm being in said neutral position when said steering handle is in said neutral position; supporting an idler arm adjacent said input arm and such that portions of said idler arm and said input arm are in contact when said steering handle is in said neutral position; using a pair of springs arranged to provide counteracting biasing forces on said steering arm and said idler arm to maintain said steering handle in said neutral position when no rotational force is being applied by said operator to said steering handle, to reduce a backlash generated by at least one of said input arm and said idler arm, but to still enable clockwise and counterclockwise motion of said input arm in response to a rotational force by the operator on the steering handle. 
         [0007]    In still another aspect the present disclosure relates to a method for steering an aircraft. The method may involve: providing a steering handle graspable and rotatable by an operator of the aircraft from a neutral position in clockwise and counterclockwise directions to first and second positions; coupling an input shaft to the steering handle; coupling an input arm to the input shaft so that rotational movement of the input shaft causes rotational movement of said input arm, the input arm being in said neutral position when said steering handle is in said neutral position; supporting an idler arm adjacent said input arm and such that portions of said idler arm and said input arm are in contact when said steering handle is in said neutral position; using a pair of springs arranged to provide counteracting biasing forces on said steering arm and said idler arm to maintain said steering component in said neutral position when no rotational force is being applied by said operator to said steering handle, to reduce a backlash generated by at least one of said input arm and said idler arm, but to still enable clockwise and counterclockwise motion of said input arm in response to a rotational force by the operator on the steering handle; sensing a rotational position of said input shaft; and using said sensed rotational position of said input shaft to control a steering movement of a wheel assembly of said aircraft. 
         [0008]    The features, functions, and advantages can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0010]      FIG. 1  is an environmental view of an aircraft employing the backlash reduction steering tiller according to various embodiments of the present disclosure; 
           [0011]      FIG. 2  is a perspective view of a zero backlash steering tiller according to one embodiment; and 
           [0012]      FIG. 3  is an exploded view of the backlash reduction steering tiller according to various embodiments. 
       
    
    
     DETAILED DESCRIPTION  
       [0013]    The following description of the various embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure, its application or uses. Although the following description is related generally to a steering system for use in a mobile platform, such as an aircraft, the system could also be potentially implemented in a marine vessel, a train or a land based motor vehicle. Thus, it will be understood that the embodiments described in the present disclosure could be employed in a wide variety of applications. Therefore, it will be understood that the following discussions are not intended to limit the scope of the appended claims. 
         [0014]    With reference to  FIG. 1 , a steering system  10  for a mobile platform, such as an aircraft  12 , is illustrated. The steering system  10  operates generally to change the direction of the aircraft  12 . The steering system  10  includes an input mechanism  14 , a portion of which is disposed in a cockpit  16  of the aircraft  12 . 
         [0015]    Referring to  FIGS. 2 and 3 , the input mechanism  14  is coupled to an idler  18 . A housing  20  may be disposed about the idler  18  and a portion of the input mechanism  14 . The idler  18  may also be coupled to a steering mechanism  22 . 
         [0016]    The input mechanism  14  includes a user interface, such as a handle  24 , coupled to an input shaft  26 . Although handle  24  is illustrated as forming the graspable steering element, it will be understood that a variety of other mechanisms could be used to interface with an occupant of the cockpit  16 , such as a joystick, lever, knob, or other appropriate mechanism by which an occupant of the cockpit  16  may manipulate a steering element. 
         [0017]    The input shaft  26  includes a first end  28  coupled to the handle  24 , a second end  30  coupled to the steering mechanism  22  and a central portion  32 . The input shaft  26  is generally configured to rotate about a Y-axis upon receipt of an input “R” or “R 2 ” from the occupant applied through the handle  24 . The input shaft  26  further includes an input arm  34  which may be integrally formed in the central portion  32 , or coupled to the central portion  32  through a post processing step, such as welding. 
         [0018]    The input arm  34  is generally circular, but may include a protrusion  36  having a vertically extending branch  38 . The protrusion  36  may be sized to enable the branch  38  to engage the idler  18 . The branch  38  may extend a selected distance “D” above a surface  40  of the input arm  34  to enable the input arm  34  to contact the idler  18 . 
         [0019]    The idler  18  is also preferably generally circular in shape, with a central opening  42 . The central opening  42  is generally sized to enable the idler  18  to be rotatably coupled to the input shaft  26 . The idler  18  is free to rotate on the input shaft  26 , typically using a bearing  41 . The idler  18  could be restrained to prevent movement up or down the input shaft  26  by a collar  43  on the input shaft  26  above the input arm  34 . The idler  18  may further include a neck  44  having a generally T-shaped branch  46 . The neck  44  may be sized to extend a length “L 1 ” from the input shaft  26 , which may typically be equivalent to a length “L 2 ” between the input shaft  26  and branch  38  of the input arm  34 . 
         [0020]    The T-shaped branch  46  may have a first end  48  and a second end  50 . The T-shaped branch  46  may be sized with a length “L 3 ” which is configured to enable the first end  48  of the T-shaped branch  46  to contact the branch  38  of the input arm  34  and the second end  50  of the T-shaped branch  46  to contact the housing  20  as will be described in greater detail below. 
         [0021]    The housing  20  may include a central opening  51  to enable the input shaft  26  to pass therethrough. The housing  20  may also be configured to enclose the idler  18  and input arm  34  of the input mechanism  14 , however, it will be understood that the shape and configuration of the housing  20  may vary for different applications. The housing  20  generally includes a stop  52  formed on an interior surface  54  of the housing  20 . The stop.  52  extends a length L 4  from the interior surface  54  to act as a contact surface for the T-shaped branch  46  of the idler  18 . Thus, the length L 4  of the stop  52  may be any length which is required to inhibit the movement of the idler  18  beyond the stop  52 . The housing  20  further includes two cavities  56  (illustrated in dashed lines for clarity) formed on the interior surface  54  for receipt of a first spring  58  and a second spring  60 . The first spring  58  may be positioned to contact the input arm  34 , and apply a pre-load force to the input arm  34 , while the second spring  60  may be positioned within the housing  20  to contact the idler  18  and apply a pre-load force to the idler  18 . Generally, the first and second springs  58 ,  60  are coil springs, however, any suitable biasing member could be employed, such as torsion springs which could apply torque about the input shaft  26  (not shown). The housing  20  may enclose the steering mechanism  22 . The housing  20  provides a means to mount the steering mechanism  22  within the aircraft  12  and keeps foreign objects from jamming the steering mechanism  22 . 
         [0022]    The steering mechanism  22  is coupled to the second end  30  of the input shaft  26 , and may, depending upon the desired configuration, be situated entirely within the housing  20 . The steering mechanism  22  includes a position transducer  62 , a controller  64  and a wheel assembly  66 . It will be understood, however, that the position transducer  62  and controller  64  may be substituted for a mechanical linkage to a mechanical steering system, as is generally known in the art. 
         [0023]    The position transducer  62  is generally coupled to the second end  30  of the input shaft  26 . The position transducer  62  operates to convert the rotational input of the input shaft  26  to a positive or negative electrical signal, depending upon the rotation of the input shaft  26 . For example, the rotation of the input shaft  26  clockwise may generate a positive electrical signal, and the rotation of the input shaft  26  counterclockwise may generate a negative electrical signal, and vice versa, however, any method of electrically distinguishing between the clockwise and counterclockwise direction could be employed. The position transducer  62  is in electrical communication with the controller  64 . 
         [0024]    The controller  64  is in communication with the position transducer  62  and the wheel assembly  66 . The controller  64  is operable to convert the electrical signal received from the position transducer  62  into a desired movement for the wheel assembly  66 , as will be discussed in greater detail below. It will be understood, however, that although the controller  64  is described herein as converting the electrical signal from the position transducer  62 , any appropriate position detecting mechanism could be employed. 
         [0025]    The wheel assembly  66  is in communication with the controller  64  and generally operates to guide the aircraft  12  based on the input received from the controller  64 . The wheel assembly  66  may include at least one wheel  68 , however, two wheels  68  are generally used in large aircraft applications. For example, the wheels  68  typically rotate about an axis  70  which may be supported by a structure  72 . The structure  72  may couple the wheels  68  to a motor  76 . The motor  76  may be in communication with the controller  64  to pivot the wheel assembly  66  to a desired angle a about an axis A based upon the input received from the controller  64 , as will be described in greater detail below. Generally, the angle a to which the wheel assembly  66  rotates is between 65 and 75 degrees. The motor  76  may be any appropriate type of motor which is capable of pivoting the wheel assembly  66  about an axis to enable the aircraft  12  to change direction. 
         [0026]    Referring further to  FIG. 2 , in order to guide or steer the aircraft  12 , the operator in the cockpit  16  may apply a force “R” to the handle  24  of the input mechanism  14 . Generally, prior to the application of the force “R” to the handle  24 , the handle  24  is in a standard position, with the first and second springs  58 ,  60  each applying a pre-load force “P 1 ” to the input arm  34  and idler  18 , respectively. The force “R” applied by the occupant to the handle  24  will cause the input shaft  26  of the input mechanism  14  to rotate, which in turn causes the input arm  34  of the input shaft  26  to apply a force F 2  against either the first spring  58  or the idler  18 , and which also causes the idler  18  to apply a force “F 3 ” to the second spring  60 , depending upon the direction of the rotation of the input shaft  26 . 
         [0027]    For example, if the operator in the cockpit  16  applies the force R clockwise, the input shaft  26  will rotate clockwise, and the input arm  34  will apply the force “F 2 ” against the first spring  58 . Further, when the input shaft  26  rotates clockwise, the idler  18  is prevented from rotating clockwise due to the stop  52  formed on the interior surface  54  of the housing  20 . Alternatively, if the operator in the cockpit  16  applies the force R counterclockwise, then the input shaft  26  will rotate counterclockwise, causing the branch  38  of the input arm  34  to apply the force “F 1 ” to the T-shaped branch  46  of the idler  18 . The application of the force “F 1 ” from the input arm  34  will in turn cause the idler  18  to apply the force “F 3 ” against the second spring  60 . 
         [0028]    As the input shaft  26  of the input mechanism  14  rotates, the position transducer  62  converts the rotation of the input shaft  26  into the corresponding electrical signal. For example, if the input shaft  26  is rotated clockwise by the occupant of the cockpit  16 , then the position transducer  62  may generate a positive electrical signal which is then transmitted to the controller  64 . Similarly, as an example, if the occupant in the cockpit  16  rotates the input shaft  26  counterclockwise, the position transducer  62  may generate a negative electrical signal which is then communicated to the controller  64 . Then, depending upon the electrical signal generated by the position transducer  62 , the controller  64  may signal the motor  76  to pivot the wheel assembly  66  to a desired angle a about the axis A. 
         [0029]    After the occupant of the cockpit  16  has completed the desired maneuver of the aircraft  12 , the occupant of the cockpit  16  may then rotate the handle  24  to the starting position, while allowing straightforward motion of the aircraft  12 . The use of the first and second springs  58 ,  60  ensures that when the input shaft  26  is in the starting position, it will return to the precise starting position with no backslash or slop when the handle  24  is released. This prevents the controller  64  from receiving numerous readings from the position transducer  62  as the first and second springs  58 ,  60  prevent small movements of the input shaft  26  when the input shaft  26  is near the starting position. In addition, if the occupant of the cockpit  16  desires to apply a counterforce R 2  in a direction opposite the force R, then it should be noted that the first and second springs  58 ,  60  enable the occupant of the cockpit  16  to smoothly transition through the starting position to guide the aircraft  12  in the opposite direction. 
         [0030]    The present disclosure provides a steering mechanism with essentially little or no backlash, and which does not require adjustment, even if the first and second springs  58 ,  60  have a loss of pre-load force P 1 . Specifically, the use of the first and second springs  58 ,  60  against the input arm  34  and idler  18  serves to remove the backlash from the steering system  10 . The use of the first and second springs  58 ,  60  also eliminates the need for adjustment to the steering system  10  to stay at zero backlash. Thus, the steering system  10  essentially forms a self-calibrating system that maintains the handle  24  at a designated “zero” position, while simultaneously removing the backlash that would otherwise be present in a convention steering system. 
         [0031]    While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.