Abstract:
The subject matter of this specification can be embodied in, among other things, a control apparatus that includes a first mounting plate, a restoring plate having a first surface disposed adjacent the first mounting plate, and a second surface. An elongate member includes a first elongate portion, a second elongate portion, an axis member between the first elongate portion and the second elongate portion, pivotally mounting the elongate member to the first mounting plate and defining a first axis, a displaceable force plate having a substantially flat surface disposed adjacent the second surface of the restoring plate, and a compliant member providing a biasing force between a retaining portion and the force plate against the second surface of the restoring plate. The mass of the second elongate portion substantially offsets the mass of the first elongate portion about the axis member.

Description:
TECHNICAL FIELD 
       [0001]    This specification relates to mechanical input controls, and more particularly, aircraft flight controls. 
       BACKGROUND 
       [0002]    Joystick input devices have been employed in a wide range of applications, from aircraft control to video game inputs. Joysticks may be provided to supply directional input information related to a single rotational axis, or to multiple axes. More sophisticated joystick instruments may provide magnitude data as well. 
         [0003]    In operation, an operator will manually displace the joystick relative to one or more of its rotational axes in order to issue directional commands to other equipment. Sensors within the joystick will sense the angular displacement of the joystick and develop input signals accordingly, which may be transmitted to the equipment to be controlled. The sensors and the signals they produce may operate electronically, hydraulically, or otherwise. 
         [0004]    In many applications it is desirable that the joystick return to a center or neutral position after it has been released by the operator. Many joysticks are designed to be displaced about two perpendicular axes, so that directional information may be detected through 360 degrees. Thus, in order to return the joystick to a center position on one or both axes, certain designs have included springs to provide a centering force relative to each axis. While these mechanisms can provide the desired centering functions, these return mechanisms also tend to add weight, complexity, and cost to the design of the joystick, and cause the joystick to be mass unbalanced and therefore more susceptible to the effects of acceleration, e.g., to resist movement of the stick by gravity, g-forces. 
       SUMMARY 
       [0005]    In general, this document describes mechanical input controls, and more particularly, aircraft flight controls. 
         [0006]    In a first aspect, a control apparatus includes a first mounting plate, a restoring plate having a first surface disposed adjacent the first mounting plate, and a second surface. An elongate member includes a first elongate portion, a second elongate portion, an axis member between the first elongate portion and the second elongate portion, pivotally mounting the elongate member to the first mounting plate and defining a first axis, a displaceable force plate having a substantially flat surface disposed adjacent the second surface of the restoring plate, and a compliant member providing a biasing force between a retaining portion and the force plate against the second surface of the restoring plate. The mass of the second elongate portion substantially offsets the mass of the first elongate portion about the axis member. 
         [0007]    Implementations can include some, all, or none of the following features. The second elongate portion can include the compliant member and the retaining member. The second surface of the restoring plate can be multi-faceted and can include a center position facet symmetrically located relative to the first axis, the center position comprising an angular position of the restoring plate wherein the center position facet abuts the substantially flat surface of said force plate and said restoring force is evenly distributed on opposite sides of said first axis. A second mounting bracket can define a second axis, the force plate being pivotally mounted to the second mounting bracket about the second axis, the centering force being evenly distributed about the second axis when the substantially flat surface of the force plate abuts the center position facet. A first lateral facet can be adjacent the center position facet and form a first angle therewith, the first lateral facet intersecting the center position facet along a first contact line extending substantially parallel to the first axis. A first secondary lateral facet can be adjacent the first lateral facet and form a second angle therewith, the first secondary lateral facet intersecting the first lateral facet along a second contact line extending substantially parallel to the first axis. A second lateral facet can be adjacent the center position facet and form a third angle therewith, the second lateral facet intersecting the center position facet along a third contact line extending substantially parallel to the first axis. The self-centering, angularly displaceable member can also include a second secondary lateral facet adjacent the second lateral facet and forming a fourth angle therewith, the second secondary lateral facet intersecting the second lateral facet along a fourth contact line extending substantially parallel to the first axis. The displaceable force plate can be a linearly displaceable force plate. The first secondary lateral facet can be non-planar. 
         [0008]    In a second aspect, a control apparatus includes a first mounting plate, a restoring plate having a first surface, and a second surface disposed adjacent the first mounting plate. An elongate member includes a first elongate portion, a second elongate portion, an axis member between the first elongate portion and the second elongate portion, pivotally mounting the elongate member to the first mounting plate and defining a first axis, and a compliant member providing a biasing force between a retaining portion and the first surface of the restoring plate. The mass of the second elongate portion substantially offsets the mass of the first elongate portion about the axis member. 
         [0009]    Implementations can include some, all, or none of the following features. The second elongate portion can include the compliant member and the retaining member. The second surface of the restoring plate can be multi-faceted and can include a center position facet symmetrically located relative to the first axis, the center position comprising an angular position of the restoring plate wherein the center position facet abuts the substantially flat surface of said first mounting plate and said restoring force is evenly distributed on opposite sides of said first axis. A second mounting bracket can define a second axis, the restoring plate being pivotally mounted to the second mounting bracket about the second axis, the centering force being evenly distributed about the second axis when the substantially flat surface of the first mounting bracket abuts the center position facet. A first lateral facet can be adjacent the center position facet and form a first angle therewith, said first lateral facet intersecting the center position facet along a first contact line extending substantially parallel to the first axis. A first secondary lateral facet can be adjacent the first lateral facet and form a second angle therewith, the first secondary lateral facet intersecting the first lateral facet along a second contact line extending substantially parallel to the first axis. A second lateral facet can be adjacent the center position facet and form a third angle therewith, the second lateral facet intersecting the center position facet along a third contact line extending substantially parallel to the first axis. The self-centering, angularly displaceable member can include a second secondary lateral facet adjacent the second lateral facet and forming a fourth angle therewith, the second secondary lateral facet intersecting the second lateral facet along a fourth contact line extending substantially parallel to the first axis. At least one of the facets can be an arcuate surface. 
         [0010]    In a third aspect a control apparatus includes a restoring plate having a first surface configured to be mounted adjacent to a first mounting plate, and a second surface. An elongate member includes a first elongate portion, a second elongate portion, an axis member between the first elongate portion and the second elongate portion, configured to pivotally mount the elongate member to the first mounting plate and defining a first axis, a linearly displaceable force plate having a substantially flat surface disposed adjacent the second surface of the restoring plate, and a compliant member providing a biasing force between a retaining portion and the force plate against the second surface of the restoring plate. The mass of the second elongate portion substantially offsets the mass of the first elongate portion about the axis member. 
         [0011]    The apparatus described herein may provide one or more of the following advantages. First, a control apparatus can provide a control stick having a self-centering capability. Second, the control apparatus can be substantially mass-balanced about an axis. Third, the control apparatus can be substantially neutral to forces of acceleration. Fourth, the control apparatus can be constructed with reduced size (e.g., envelope), weight, cost, and/or parts count. 
         [0012]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0013]      FIGS. 1A and 1B  are plan views of an example passive control stick. 
           [0014]      FIG. 2  is a perspective view of an example restoring plate. 
           [0015]      FIGS. 3A-3C  are plan views of an example passive control stick at various operating positions. 
           [0016]      FIG. 4  is an example torque profile for an example passive control stick. 
           [0017]      FIG. 5  is a plan view of another example passive control stick. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    This document describes mechanical devices for accepting operator input, such as flight control sticks or side sticks used by aircraft pilots. In general, an aircraft or other machine may provide a “joystick” type side stick user control, and an operator may manipulate the stick to control the machine. For example, the operator may push, pull, move side to side, or otherwise manipulate a control stick to steer the machine. In general, some implementations may benefit from a control stick configuration that automatically returns to a default position after being displaced, or one that substantially maintains default position against gravity or other acceleration forces, e.g., g-forces. 
         [0019]    Weight, cost, and size, are other considerations that may generally influence the selection of a control stick mechanism, especially for use in aircraft applications. Issues of weight, cost, and/or size considerations, however, may run counter to the inclusion of self-centering features which can add complexity to a control stick design, and still may not provide the aforementioned substantial neutrality to g-forces. 
         [0020]    This document describes a control stick design that is substantially mass balanced about its axis to provide increased resistance to movement under acceleration. In general, the balanced nature of the control stick is accomplished by incorporating mechanical components used for providing self-centering and other functions into the movable mechanisms of the control stick itself in a design that balances the amount of mass included on each control of the control stick&#39;s axis point. In some implementations, by incorporating the mass of such mechanisms into the balance of the control stick, the control stick can provide increased neutrality to acceleration without using additional counterweights, thereby providing increased neutrality without substantially increasing weight. 
         [0021]      FIGS. 1A and 1B  are plan views of an example passive control stick  100 . In some embodiments, the passive control stick  100  can be provided as a side stick, a center stick, a control column, a control yoke, or any other appropriate adaptation of a lever control device. Referring to  FIG. 1A , the passive control stick  100  is shown in a substantially centered or default position. The passive control stick  100  includes an upper elongate portion  102   a  extending above a fixture base plate  114  and a lower elongate portion  102   b  extending below the fixture base plate  114 . The upper elongate portion  102   a  and the lower elongate portion  102   b  are two opposing radial sections of a rotary member  103 , which rotates about an x-axis  118  located substantially at the fixture base plate  114 . Angular displacement of the upper elongate portion  102   a  causes a similar angular displacement in the lower elongate portion  102   b.    
         [0022]    As shown in  FIGS. 1A and 1B , the upper elongate member  102   a  includes a grip assembly  116 . The grip assembly  116  extends radially away from the x-axis  118 . In use, a user manipulates the grip assembly to cause the passive control stick to rotate about the x-axis  118 . In some embodiments, the grip assembly may be formed for manipulation by a user. For example, the grip assembly may be sized and contoured to fit the hand of a pilot of other machine operator. 
         [0023]    With regard to the example passive control stick  100 , a restoring plate  104  is coupled to the underside of the fixture base plate  114 . The restoring plate  104  remains substantially fixed relative to the movement of the passive control stick  100  about the x-axis  118 . The restoring plate  104  will be discussed in further detail in the description of  FIG. 2 . 
         [0024]    With regard to the example passive control stick  100 , the lower elongate portion  102   b  includes a force plate  106  and a compliant member  112 , e.g., a spring. The force plate  106  is disposed between the restoring plate  104  and the compliant member  112 . Angular displacement of the lower elongate portion  102   b  is translated to rotation of the force plate  106  about the restoring plate  104 . The force plate  106  is guided by a linear bearing  108  disposed between the force plate  106  and a base portion  115  of the lower elongate member  102   b.  The compliant member  112  is compressed between the force plate  106  and the base portion  115 , biasing the force plate  106  against a lower surface of the restoring plate  104 . 
         [0025]    With regard to the example passive control stick  100 , the upper elongate portion  102   a  and the lower elongate portion  102   b  are formed so the mass of the upper elongate portion  102   a  and the mass of the lower elongate portion  102   b  are substantially balanced across the x-axis  118 . In some implementations, the mass of the upper elongate portion  102   a  may be equal to the mass of the lower elongate portion  102   b,  with their respective masses being distributed substantially symmetrically about the x-axis  118 . In some implementations, the mass of the upper elongate portion  102   a  may be equal or unequal to the mass of the lower elongate portion  102   b,  with their respective masses being distributed substantially asymmetrically about the x-axis  118 . For example, the upper elongate portion  102   a  may include relatively lightweight components located to create a relatively long lever arm, e.g., distance between the components and the fulcrum, and the lower elongate portion  102   b  may include relatively heavier components located to create a relatively shorter lever arm. As such, unequal masses and/or unequal lever lengths may be combined to substantially balance the distribution of the passive control stick about the x-axis. 
         [0026]    Referring to  FIG. 1B , the example passive control stick  100  is shown in an offset or rotated position. For example, a user may push the grip assembly  116  to the right, causing the passive control stick  100  to rotate clockwise as illustrated in  FIG. 1B . 
         [0027]    As will be discussed in further detail in the descriptions of  FIGS. 3A-3C , as the example passive control stick  100  is moved away from the centered configuration shown in  FIG. 1A , the force plate  106  rotates about the restoring plate  104 . The shape of the restoring plate, which will be discussed in further detail in the description of  FIG. 2 , causes the force plate  106  to compress the compliant member  112 . Compression of the force plate  106  against the surface of the restoring plate  104  forms a restoring force that urges the passive control stick back toward the substantially centered or default position shown in  FIG. 1A . 
         [0028]      FIG. 2  is a perspective view of an example restoring plate  200 . In some implementations, the restoring plate  200  can be the restoring plate  104  of  FIGS. 1A and 1B . The restoring plate  200  forms a cam-like surface comprised of a collection of adjacent planar segments, or facets. In the illustrated example, the multifaceted surface includes seven facets including a center position facet  128 , lateral facets  126 ,  130 ,  134  and  6  backside  136 , and secondary lateral facets  124 ,  132 . Adjacent facets intersect along contact lines between each angled surface. In the illustrated example, there are ten contact lines labeled  138 - 156  (even numbers only) in  FIG. 2 . The vertical lines  158 ,  160 ,  162 , and  164  forming the four corners of the restoring plate  104  may also be considered contact lines if the passive control stick  100  is allowed to pivot to such an extent that facets  124  and  134  are allowed to contact the force plate  106 . As will be described in more detail below, contact lines  138 ,  140 ,  142 , and  144  affect the rotation of the force plate  104  about the x-axis  118 , and contact lines  146 ,  148 ,  150 , and  152 ,  154 ,  156  affect rotation about the y-axis. The corners  158 ,  160 ,  162 , and  164  will also affect the rotation of the restoring plate  104  about the y-axis, if the passive control stick  100  is allowed to rotate sufficiently to allow the corners to contact the force plate  106 . 
         [0029]    Facet  128  of the example passive control stick  100 , located in the center of restoring plate  104 , defines the center position of the passive control stick  100 .  FIG. 1  shows the example passive control stick  100  in the centered position with facet  128  abutting the surface of force plate  106 .  FIG. 3A  shows the example passive control stick  100  in the centered position with facet  128  abutting the surface of force plate  106 . In some embodiments, the facet  128  may be slightly non-planar. For example, the facet  128  may be formed with a slight undercut to reduce adhesion that may occur between the facet  128  and the force plate  106  in the presence of a fluid, e.g., a lubricant, when the force plate  106  is substantially coplanar to the facet  128 . In some embodiments, the facet  128  may be omitted. For example, some applications may not benefit or require a centering action from the example passive control stick  100 . 
         [0030]    Although the example restoring plate  104  has been described as having planar facets, contact lines, and corners, other embodiments can exist. For example, the contact lines may be curved or arcuate rather than straight, greater or fewer facets may be used, the facets may be non-planar or arcuate rather than being substantially flat, and/or the corners may be rounded rather than sharp. Combinations of flat and arcuate surfaces, and/or straight, arcuate, smooth, and/or sharp transitions between surfaces can be combined to provide complex torque profiles according to the intended application of a passive control stick. 
         [0031]      FIGS. 3A-3C  are plan views of the example passive control stick  100  at various operating positions.  FIG. 3A  is a plan view of the example passive control stick  100  looking down the x-axis. In  FIG. 3A  the center position relative to the x-axis  118  is formed when the contact lines  140 ,  142  frame the left and right edges of facet  128 , and are laterally offset a substantially equal distance from the x-axis  118 . The restoring force exerted by force plate  106  acts substantially uniformly against facet  128  on each side of the x-axis  118 . Thus, substantially no torque is developed tending to rotate the force plate  106  about the x-axis  118 . The force plate  106  will tend to remain in the center position relative to the x-axis until an external displacement force is applied to the upper elongate member  102 A. The passive control stick  100  will tend to remain substantially centered even when the passive control stick  100  is exposed to external forces of acceleration, such as gravity or g-forces, since the upper elongate member  102   a  and the lower elongate member  102   b  are substantially mass-balanced about the x-axis  118 . 
         [0032]    In contrast to the centered position, when the force plate  106  of the example passive control stick  100  is angularly displaced with regard to the x-axis  118  the restoring force exerted by force plate  106  is concentrated along lines or at points that are laterally offset from the x-axis  118 . This generates a restoring torque which tends to return the force plate  106  to the center position. Thus, when the upper elongate member  102   a  of the passive control stick  100  is displaced by an external force such as a user manipulation, the restoring torque tends to re-center the passive control stick  100  as soon as the external force is removed. Conversely, the passive control stick  100  tends to remain substantially stable in the centered position until an external force is applied to the upper elongate member  102   a.    
         [0033]    In  FIG. 3B , the example passive control stick  100  is displaced a small distance to the right by a force, causing the force plate  106  to rotate a small amount in the clockwise direction. The force plate  106  is rotated away from the contact line  140 , and the force plate  106  is rotated into the contact line  142 , further compressing the compliant member  112 . Contact line  142  is offset from the x-axis  118  by a lateral distance D×1. Thus, rotation of the forge plate  106  about the x-axis  118  generates a restoring torque substantially equal to the spring force applied to the contact line  142 , multiplied by the distance D×1. As the force plate  106  rotates about the x-axis  118 , the distance D×1 will vary little during the course of the limited angular displacement of the passive control stick  100 . In some embodiments, the restoring torque can be proportional to the linear displacement of the force plate  106  due to the downward rotation of the force plate  106  away from the contact line  142 . Rotation of the force plate  106  in the opposite direction of that shown in  FIG. 3B  will have substantially the same effect, only the force plate  106  will act against contact line  140  and the restoring torque will be directed in the opposite direction. 
         [0034]    Referring now to  FIG. 3C , the example passive control stick  100  has been displaced to the right by a relatively greater distance than in  FIG. 3B , causing the force plate  106  to rotate in the clockwise direction by an amount equal to the angle β. Thus, the force plate  106  of  FIG. 3C  lies substantially parallel to the facet  130 . If the passive control stick  100  is rotated further to the right, the surface of the force plate  106  will be rotated clear of the contact line  142 , and force plate  106  will rotate against the contact line  144 , further compressing the compliant member  112 . The contact line  144  is located a distance from the x-axis equal to D×2 which is greater than D×1. When the contact line  144  engages the force plate  106 , the force applied against the force plate  106  is offset further from the x-axis  118 , and the restoring torque is increased proportionally. 
         [0035]    In some embodiments, the example passive control stick  100  can include a mounting bracket defining a second axis. The force plate  106  can be pivotally mounted to the mounting bracket about the second axis, and the centering force can be substantially evenly distributed about the second axis when the force plate  106  is substantially parallel to the plane of the facet  128 . 
         [0036]      FIG. 4  is an example compound torque profile for the example passive control stick  100  of  FIG. 1 . In some embodiments, compound force profiles may be created in any practical direction by altering the lower surface of the restoring plate  104 . For example, the angular position where the restoring torque jumps to a higher level may be manipulated by altering the angles α and β. In some embodiments, the size of the jump may be controlled by selecting the width of the lateral facets. With the restoring plate  104  profile shown in  FIGS. 1 ,  2 A- 2 B, and  3 A-C, as the width of lateral facets  126  and  130 , is increased, the distance D×2 between the contact lines  140 ,  142  and the contact lines  138 ,  144  will increase. Thus, the greater the width of the lateral facets  126 ,  130 , the greater will be the increase in the restoring torque at angles greater than α or β. In various embodiments, the passive control stick  100  can be a self-centering joystick capable of having multiple complex compound force profiles. 
         [0037]    When the angular displacement of the force plate  106  is less than α or β, the restoring torque increases in a substantially linear manner with increasing angular displacement. However, when the angular displacement exceeds α or β, the restoring torque jumps to a higher level as the more distant contact lines  138 ,  144  engage the force plate  106 . Once the angular displacement exceeds α or β, the restoring torque again increases linearly with further angular displacement of the force plate  106 . 
         [0038]    As discussed in the description of  FIG. 2 , although the example restoring plate  104  has been described as having planar facets, contact lines, and corners, other embodiments can exist. For example, the contact lines may be curved rather than straight, greater or fewer facets may be used, the facets may be non-planar rather than being substantially flat, and/or the corners may be rounded rather than sharp. Combinations of flat and curved surfaces, and/or smooth and sharp transitions can be combined to provide other torque profiles that can be relatively more or less complex than the example torque profile shown in  FIG. 4 . 
         [0039]      FIG. 5  is a plan view of another example passive control stick  500 . The example passive control stick  500  is substantially similar in form and function to the example passive control stick  100  of  FIGS. 1A-1B , except that he restoring plate  104  has been replaced by a restoring plate  504 , and the force plate  106  has been removed. 
         [0040]    The restoring plate  504  of the example passive control stick  500  s substantially similar to the restoring plate  104 , except the restoring plate  504  has been inverted vertically compared to the restoring plate  104 . The restoring plate  504  is not coupled to the fixture base plate  114 , rather fixture base plate  114  is compressed against the fixture base plate  114  by the compliant member  112  and is guided by the linear bearing  108 . 
         [0041]    Angular displacement of the example passive control stick  100  about the x-axis  118  causes the restoring plate  504  to rotate about the x-axis  118  as well. As the restoring plate  104  rotates, the contact lines of the restoring plate come into contact with the fixture base plate  114 . This contact causes the restoring plate  104  to compress the compliant member  112  to create complex restoring torques substantially similar to those discussed in the descriptions of  FIGS. 3A-3C . In various embodiments, the example passive control sticks  100  and  500 , and/or the example restoring block  200  can be made of metal (e.g., aluminum, steel, titanium), plastic, composite materials (e.g., fiberglass, carbon fiber), wood, or combinations of these and/or any other appropriate material. In various embodiments, the example passive control sticks  100  and  500 , and/or the example restoring block  200  can be formed by casting, molding, machining, extruding, or combinations of these and/or any other appropriate formation technique. 
         [0042]    In some embodiments, the example passive control stick  500  can include a mounting bracket defining a second axis. The restoring plate  504  can be pivotally mounted to the mounting bracket about the second axis, and the centering force can be substantially evenly distributed about the second axis when the restoring plate  504  is substantially parallel to the plane of the facet  128 . 
         [0043]    Although a few implementations have been described in detail above, other modifications are possible. For example, other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.