Patent Publication Number: US-RE42183-E

Title: Interface control

Description:
FIELD OF THE INVENTION 
     The present invention relates to an interface control. More particularly, the present invention relates to an interface control device which allows a user to control the operation of computer applications, machinery, and video games. 
     BACKGROUND OF THE INVENTION 
     Joystick controls have been employed in a wide variety of applications, including computer software, industrial machinery, and multimedia interfaces to control the positioning of an object displayed on a screen, such as a cursor or pointer. A typical prior art joystick includes a gimballed stick pivotally coupled to a flat base portion. Angle sensors coupled to the gimballed stick generate position control signals in response to a user pivoting the gimballed stick relative to the base portion. These control signals are used to manipulate the position of the cursor. A depressible switch coupled to the top of the stick is used to generate a trigger control signal for implementing various functions, such as selecting items from a pull down menu or causing a character in a video game to jump. 
     The structure of these gimballed joystick controllers makes them somewhat difficult to operate. Rotating the arm and wrist to control positioning functions (i.e., pivoting the stick) while pressing downward with the thumb or finger to manipulate trigger functions requires a fair amount of practice and coordination. Further, requiring a user to simultaneously combine these motions may lead to an inadvertent change in the positioning of a cursor while implementing a trigger function. For instance, in a point-and-shoot operation, where a user first positions the cursor onto a target on the display screen and then activates the trigger function, depressing the trigger switch with the thumb or finger often results in slight movements of the arm and/or wrist, thereby causing the cursor to slip off the target. This phenomenon is commonly referred to as cursor creep. 
     The conventional joystick controller described above has the further disadvantage of undesirably requiring the use of two hands, i.e., one hand to hold the base of the controller and the other hand to operate the controller&#39;s stick. The only manner in which these controllers may be operated with one hand is to place the controller on a table or other flat surface. 
     Other joystick controllers have been developed in response to the above-mentioned problems. One such controller includes a pivoting, handgrip-shaped stick having one or more squeezable trigger switches built into a side portion of the handgrip. The positioning of an image is controlled by pivoting the handgrip, while the trigger functions are controlled by squeezing the trigger switches with the fingers. Although in such a design the positioning controls are somewhat isolated from the trigger function controls (i.e., squeezing the trigger switch with the index finger is not likely to cause as much of an inadvertent change in position as would depressing a trigger switch on the top of the stick with the thumb), cursor creep is nevertheless a problem. Further, such a controller requires the use of two hands or, alternatively, a tabletop support. 
     Some have attempted to develop a one-handed controller by simply reducing the size of conventional joystick controllers. These controllers fit within a user&#39;s hand, where the thumb, resting atop the stick, controls the positioning function. The trigger function is controlled by squeezing a trigger switch located on the side of the controller&#39;s stick. 
     These miniaturized versions of conventional joystick controllers are for the most part clumsy and ineffective. Merely reducing the size of a controller designed for two-handed operation so as to be operated by one hand severely limits the precision with which a user may control a cursor. Further, these miniaturized controllers are ineffective in isolating trigger controls from positioning controls. Indeed, squeezing a trigger switch with, for example, the index finger typically causes the controller stick to move forward, thereby resulting in undesirable vertical cursor creep. 
     This undesirable interaction between positioning and trigger controls of miniature joystick controllers, coupled with users&#39; complaints of inferior ergonomics, has led others to revert to the more primitive two-handed video game controller shown in FIG.  1 . Controller  1  has four keys  2 a- 2 d clustered together in a first portion of controller  1  and three keys  4 a- 4 c grouped together in a second portion of controller  1 . Keys  2 a- 2 d control the positioning of a displayed object (such as the hero of the video game) by generating digital positioning signals in response to a user depressing one or more of keys  2 a- 2 d. Keys  4 a- 4 c control various trigger functions (i.e., start-stop, jump, shoot, for example). The controller shown in  FIG. 1 , although virtually eliminating inadvertent interaction between positioning and trigger controls, nonetheless requires the use of two hands. 
     Thus, there is a need for joystick controller which may be operated in one hand. There is also a need for a controller having improved precision and ergonomics. Such a device should also isolate positioning and trigger controls, thereby eliminating cursor creep and other inadvertent position control signals produced during activation of trigger functions. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an interface control is disclosed which offers users superior performance and ergonomics. In the preferred embodiment, a thumbpiece is slidably disposed within a longitudinal arm member having a first end pivotally coupled to a fixed point. The arm member may pivot about the fixed point such that a second end portion of the arm member follows an arcuate path having as its center the fixed point. The thumbpiece slides back and forth along the longitudinal axis of the arm member. A first sensor coupled to the arm member in a region proximate to the fixed point senses the angular position of the arm member. A second sensor coupled to the thumbpiece senses the linear movement of the thumbpiece relative to and longitudinally along the arm member. A third sensor coupled to the thumbpiece senses a downward force exerted upon the thumbpiece. 
     The interface control may, in one embodiment, comfortably rest in the palm of a user&#39;s hand. Positioning the fingers along the underside of the interface control, a user places the thumb in the thumbpiece. The user controls the horizontal positioning of, for example, a cursor by causing the arm member to pivot either to the right or to the left about the fixed point. This motion is detected by the first sensor, which in response thereto causes the cursor to move either right or left, respectively, on a display screen. The vertical positioning of the cursor is controlled by sliding the thumbpiece along the length of the arm member. The second sensor detects this linear movement of the thumbpiece and, in response thereto, causes the cursor to move up and down on the display screen. A user may implement trigger functions by exerting a downward force on the thumbpiece. This pressure is detected by the third sensor which, in turn, causes some predetermined function to be implemented on the display screen. 
     In another embodiment, the longitudinal arm member is disposed within a track defining an arcuate path rather than being coupled to a fixed pivot point. In this embodiment, positioning and trigger functions are controlled in the same manner as described in the preferred embodiment. By moving the arm member along the arcuate path as defined by the track, the thumbpiece follows an arcuate path having as its center a virtual pivot point. A sensor coupled to the arm member senses the arcuate movement of the arm member relative to the interface control and in response thereto generates a horizontal positioning control signal. The vertical positioning of the cursor and trigger functions are implemented as described above in connection with the preferred embodiment. 
     Embodiments of the present invention isolate the trigger function from the positioning controls. The downward force used to implement a trigger function will always be orthogonal to those motions of the thumb which are used to control the positioning of the cursor, regardless of the positions of the arm member or thumbpiece. This orthogonal relationship prevents a user from inadvertently altering the positioning of the cursor when trying to implement a trigger function. 
     Embodiments in accordance with the present invention also achieve superior ergonomics. The arm member is preferably of a length approximately equal to that of an adult thumb where different length arm members can be provided for different size hands. Together the arm member, which rotates to form an arcuate path, and the thumbpiece, which slides along the length of the arm member, emulate the natural pivoting and curling/extending motions of the thumb, respectively. The result is a comfortable, precise, and easy to use interface control. 
     In another embodiment, additional trigger switches are provided within cavities formed in the underside of the interface control. The fingertips of the user&#39;s hand, each comfortably nestled within an associated cavity, control the operation of the additional trigger switches, which may be used to implement numerous other functions. 
     Embodiments of the present invention are usable as an interface between a user and a machine where the machine carries out come predetermined function in response to commands issued by the user. In one embodiment, for instance, the user may control the mechanical operation of construction equipment. In another embodiment, the user may control moveable elements on a display screen, such as a cursor in a software application or an object in a video game. 
     This invention will be more fully understood in view of the following description taken together with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a prior art four-key cluster joystick controller; 
         FIG. 2  is a plan view of one embodiment in accordance with the present invention; 
         FIGS. 3A and 3B  are side and end views of the embodiment of  FIG. 2 , respectively; 
         FIG. 4  is a perspective view of a portion of the embodiment of  FIG. 2 ; 
         FIG. 5  shows one embodiment in accordance with the present invention resting in the palm of a user&#39;s hand; 
         FIG. 6  shows another embodiment in accordance with the present invention; 
         FIG. 7  is an end view of another embodiment in accordance with the present invention; 
         FIG. 8  is a plan view of yet another embodiment in accordance with the present invention; 
         FIG. 9  shows the embodiment of  FIG. 2  used in conjunction with the prior art controller of  FIG. 1 ; and 
         FIGS. 10 ,  11  and  12  are plan views of three other embodiments in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with the present invention, an interface control is disclosed which allows a user to simultaneously control both a trigger function and the positioning of a cursor through a single contact surface using only the thumb. In the preferred embodiment shown in  FIGS. 2 ,  3 A,  3 B,  4  and  5 , a hand-held interface control  10  is provided in support  12  which includes base plate  14  and side wall  16  having first rounded end portion  16 a, second rounded end portion  16 b, and side portions  16 c,  16 d connecting rounded end portions  16 a,  16 b. Top plate  18  ( FIGS. 3A and 3B ) is provided above side wall  16  and encloses a portion of support  12 . Longitudinal arm member  20  ( FIGS. 2 ,  3 A,  3 B,  4 ,  5 ) is disposed in and pivotally connected to support  12  ( FIG. 2 ) at point  22 . Arm member  20  may be connected to support  12  by any suitable means, such as bolt  23  ( FIGS. 2 ,  3 A,  3 B,  4 ,  5 ), or an appropriate bearing surface which allows arm member  20  to pivot about point  22  as indicated by arrows  25 a,  25 b (FIG.  2 ). As will be explained below, the resistance provided between (1) arm member  20  and base plate  14  and (2) thumbpiece  28  and arm member  20  may be adjusted to a level suitable to the needs of a particular user or application. 
     First sensor  26  ( FIGS. 2 ,  3 A,  3 B) is coupled to arm member  20  and senses the angular rotation of arm member  20  about point  22 . First sensor  26 , preferably a rotary resistive potentiometer although other appropriate sensing structures such as capacitive sensors, for example, can also be used, generates first positioning signals indicative of the direction and magnitude of arm member  20 &#39;s rotation about point  22 . 
     Referring to  FIGS. 3A and 4 , arm member  20  has cavity  30  formed at one end thereof. Cavity  30  is bounded on either side by side walls  20 a,  20 b which have formed therein grooves  34 a,  34 b (groove  34 b, which is formed within side wall  20 b, is not shown in FIG.  4 ). 
     Thumbpiece  28  ( FIGS. 2 ,  3 A, and  4 ) is slidably mounted within cavity  30  of arm member  20  and may slide along the length of arm member  20 , as indicated by arrows  32 a,  32 b (FIG.  2 ). Outwardly protruding flanges  36 a,  36 b ( FIG. 4 ) provided on the sides of thumbpiece  28  matingly couple with grooves  34 a,  34 b formed in side walls  20 a,  20 b, respectively, of arm member  20  to facilitate the sliding of thumbpiece  28  along the length of arm member  20 . Curved contact surface  38 , which is provided on a top surface of thumbpiece  28 , engages the thumb of a user operating hand-held interface control  10  ( FIGS. 2 ,  3 A, and  3 B). 
     Shaft  40  ( FIGS. 2 ,  3 A) has a first end fixably mounted to a bottom surface of thumbpiece  28  and a second end slidably disposed within second sensor  42 . Second sensor  42 , which is disposed within arm member  20 , detects the linear movement of shaft  40  (and thus the linear movement of thumbpiece  28 ) relative to sensor  42  and generates second positioning signals indicative of the position of thumbpiece  28  relative to arm member  20 . 
     Second sensor  42  is preferably a linear resistive potentiometer. If a rotary potentiometer is used as second sensor  42 , thumbpiece  28  may be coupled to the potentiometer by a conventional rack and pinion gear. It is to be understood, however, that any other sensing device capable of detecting either motion or pressure may be used as first sensor  26  and second sensor  42  in interface control  10 . Although first sensor  26  and second sensor  42  preferably produce analog positioning signals, interface control  10  may also employ s sensors which produce digital positioning signals. 
     A third sensor  44  ( FIG. 3A ) is secured to a bottom surface of arm member  20  so mat third sensor  44  moves with arm member  20  about point  22  (FIG.  2 ). A bottom surface of third sensor  44  is in contact with and slides along (when arm member  20  pivots about point  22 ) a top surface of base plate  14  (FIG.  3 A). When a user exerts a downward pressure upon thumbpiece  28 , third sensor  44  engages base plate  14  and in response thereto generates a trigger control signal. Third sensor  44  may be any conventional pressure sensitive device which converts a pressure into an electric signal. In one embodiment, third sensor  44  is a microswitch of well known design. 
     A user cradles hand-held interface control  10  in the palm of his or her hand, positioning his fingers along the underside of bottom plate  14  and resting his thumb on curved contact surface  38  of thumbpiece  38 , as shown in FIG.  5 . Using only his thumb, the user may control the horizontal and vertical positioning of, for instance, a cursor on a display screen, as well as implement various related functions (such as selecting options from a pull-down menu). 
     The horizontal positioning of the cursor is manipulated by pivoting arm member  20  about point  22 , whereby arm member  20  traces an arcuate path as indicated by arrows  25 a,  25 b (FIG.  2 ). First sensor  26 , in response to the arcuate motion of arm member  20 , generates a first positioning signal which controls the horizontal positioning of a cursor on a display screen indicative of the angular position of arm member  20 . For instance, to move the cursor to the right on the display screen, the thumb (resting in thumbpiece  28 ) is used to move arm member  20  in an arcuate path to the right, as indicated by arrow  25 a. 
     Preferably, arm member  20  is of a length (measured between portions  16 a and  16 b of side wall  16 ) approximately equal to that of the user&#39;s thumb so that when a user places the thumb on contact surface  38  of thumbpiece  28 , the user&#39;s large thumb joint is immediately above point  22 . The length of arm member  20  may be of varying lengths so as to accommodate different size hands. As discussed above, arm member  20 , pivoting about point  22 , travels in an arcuate path between sidewalls  16 a,  16 b of interface control  10 . This arcuate path emulates the natural motion of the thumb as it pivots about the large thumb joint, thereby resulting in a natural and ergonomic relationship between the thumb and arm member  20 . Hence, interface control  10  uses the natural arcuate motion of a user&#39;s thumb to effect linear changes in the horizontal positioning of a cursor on the display screen. 
     The vertical positioning of the cursor is controlled by sliding thumbpiece  28  along the length of arm member  20  as indicated by arrows  32 a,  32 b (FIG.  2 ). Second sensor  42  detects the linear movement of thumbpiece  28  and, in response thereto, generates second positioning signals which control the vertical positioning of the cursor. For instance, to move the cursor up or down on a display screen, the user simply uses his or her thumb to move thumbpiece  28  away from or towards point  22 . This movement is easily achieved by extending or curling the thumb. Note that by positioning the fingers on the bottom side of base plate  14 , the combined movement of the fingers assist the thumb in the curling and extending motions. 
     Trigger functions are implemented by exerting a downward pressure (using the thumb) upon thumbpiece  28 . Third sensor  44  senses this downward pressure and, in response thereto, generates a trigger control signal. Depending upon the particular application with which interface control  10  is being used, this trigger control signal may implement a variety of functions. For instance, in computer software or interactive systems, this trigger control may select items from a menu. When used with a video game, for example, this trigger control may cause a character to jump. 
     The downward pressure exerted by the thumb to implement a trigger control signal is always orthogonal to the thumb motions used to control horizontal and vertical positioning, regardless of the angular position of arm member  20  or the linear position of thumbpiece  28 . This orthogonal relationship eliminates undesirable interaction between the trigger control and the positioning controls and thus prevents cursor creep. A user, when exerting a downward pressure on thumbpiece  28 , is not likely to inadvertently pivot or extend/curl the thumb (which would cause a change in the positioning of the cursor). Thus, by isolating the trigger and positioning controls, as described above, interface control  10  provides advantages over conventional joystick controllers which suffer from cursor creep problems. 
       FIG. 6  shows another embodiment of the present invention. Interface control  50 , the operation of which is identical to that of interface control  10 , includes all the components of interface control  10  plus additional features described below. Interface control  50  includes two groups of cavities  52 a,  52 b, and  52 c and  54 a,  54 b, and  54 c formed in the bottom surface of base plate  14 . When a user cradles interface control  50  in the left hand, the tips of the three fingers closest to the thumb may comfortably rest within associated cavities  52 a- 52 c. Each of cavities  52 a,  52 b, and  52 c has an associated switch  56 a,  56 b,  56 c, respectively, disposed therein so that each of the user&#39;s fingers may activate one of associated switches  56 a,  56 b,  56 c while holding interface control  50 . Switches  56 a,  56 b,  56 c, when depressed by the user&#39;s finger tips, generate second, third, and fourth trigger control signals, respectively, for implementing additional predetermined functions. 
     In a similar manner, a right-handed user may place one of the three fingers closest to the thumb (of the right hand) in each of cavities  54 a,  54 b, and  54 c to operate associated switches  58 a,  58 b,  58 c, which, like switches  56 a,  56 b,  56 c, generate second, third, and fourth trigger control signals, respectively, for implementing various predetermined functions. 
     If additional control signals are desired for implementing even more predetermined fractions, control circuitry may be added so that the simultaneous depression of two of more switches  56 a,  56 b,  56 c (or  58 a,  58 b,  58 c for right-handed users) generate these additional control signals. For instance, simultaneously depressing switches  56 a and  56 b (for left-hand operation) or  58 a and  58 b (for right-hand operation) may generate a fifth trigger control signal. 
       FIG. 7  is an end view of another embodiment in accordance with the present invention. Interface control  60 , which operates in a manner identical to interface control  10  ( FIGS. 2 ,  3 A,  3 B,  4 , and  5 ), includes a plurality of first detents  61  formed on the top surface of base plate  14 . One second detent  62  is provided on the bottom surface of arm member  20  such that as arm member  20  pivots about point  22  (not shown), second detent  62  moves between pairs of the plurality of first detents  61 . Arm member  20  may preferably come to rest only at those positions where second detent  62  is positioned between a pair of first detents  61 , thereby providing arm member  20  with a discrete number of click stops. These click stops may add increased stability and control to the positioning controls of interface control  60 . 
     The embodiments in accordance with the present invention are advantageous over conventional joystick controllers. Indeed, interface controls  10  and  50  are suitable for one-handed operation, thereby leaving the user&#39;s other hand free to perform other tasks. This one-handed operation also eliminates the need for a flat surface, as required when using a mouse or operating conventional joystick interface controls with one hand. 
     Using the thumb to control positioning functions contributes to the superior ergonomics of interface controls  10  and  50 . As mentioned above, conventional joystick controllers require various combinations of wrist and arm movements to control the positioning of a cursor and additional finger or thumb motions to control trigger functions. Such unnatural combinations of motions necessitate training and practice in order for a user to become proficient. This is especially true as the size of such a control is reduced. Unlike conventional controllers, embodiments in accordance with the present invention (1) isolate the horizontal and vertical positioning functions from each other and (2) isolate the positioning functions from the trigger functions while simultaneously allowing both functions to be controlled by a single user contact point. The result is an interface control which allows users to issue vertical and horizontal positioning commands in concert for smooth and precise motions along both axes (i.e., a diagonal motion), as well as implementing trigger functions without inadvertently altering those positioning commands. Further, the interface controls described herein allow users to control both positioning and trigger control functions with simple, intuitive thumb motions. 
     When a user traces his or her thumb across the tips of the fingers, every joint in his or her hand moves in concert to facilitate the thumb&#39;s motion. This opposed position of a user&#39;s thumb relative to his or her fingers and palm is utilized by interface controls  10  and  50  to achieve a comfortable and natural interface between the user and a machine (such as a computer). Indeed, by positioning a user&#39;s fingers along the bottom surface of base plate  14  and his or her thumb in thumbpiece  28 , interface controls  10  and  50  operate in a manner consistent with the thumb&#39;s natural motions. By taking advantage of the thumb&#39;s full arcuate motion about the large thumb joint and the thumb&#39;s excellent linear motion, interface controls in accordance with the present invention allow a user to quickly and easily position a cursor or pointer on a display screen. The superior ergonomics of the above interface controls afford users a high degree of precision and efficiency without the extensive practice and training required of conventional joystick controllers. This accuracy and ease of use makes the present interface controls especially well suited for CAD or any other computer illustration systems. 
     The frictional coupling between elements of the preferred embodiments may be manipulated to adjust the “feel” of interface controls  10  and  50 . For instance, contact surface  38  ( FIGS. 4 and 8 ) of thumbpiece  28  may be shaped with respect to the top surfaces of sidewalls  20 a,  20 b so that the sides of a user&#39;s thumb are in frictional contact with sidewalls  20 a,  20 b. This frictional contact may increase the stability with which thumbpiece  28  slides along arm member  20 , thereby increasing the accuracy of vertical positioning of a cursor. 
     In a similar manner, the frictional coupling between third sensor  44  ( FIG. 3A ) and the top surface of base plate  14  of housing  12  may be adjusted to increase the accuracy of the horizontal positioning control of interface controls  10  and  50 . For example, a strip of Teflon material (not shown) may be provided between third sensor  44  and bottom plate  14  to achieve a desirable “silky” feel when a user pivots arm member  20  about point  22  (FIG.  4 ). The Teflon causes drag to progressively increase as thumbpiece  28  is depressed, without any significant increase in static friction. This resultant increase in drag contributes to an increased stability in performing drag-select operations in which the trigger switch is depressed while the cursor is moved from a first position to a second position (as in highlighting text in word processing programs). 
       FIG. 8  shows another embodiment in accordance with the present invention. Interface control  65  includes arm member  29  slidably disposed on conventional curved guide tracks  64 a,  64 b within support  67 . Tracks  64 a,  64 b define an arcuate path having as its center virtual pivot point  66 . Arm member  29  slides along this arcuate path as indicated by arrows  25 a,  25 b as if arm member  29  were pivoting about virtual pivot point  66 . Disposing arm member  29  within tracks  64 a,  64 b in this manner eliminates the need for arm member  29  to be coupled to a fixed pivot point, as is arm member  20  of interface control  10  ( FIGS. 2 ,  3 A,  3 B,  4 , and  5 ), and therefore allows for interface control  65  to be of a significantly smaller size. Thumbpiece  28  is slidably disposed within arm member  29  and slides along the length of arm member  29  as indicated by arrows  32 a,  32 b. 
     The positioning and trigger functions of interface control  65  are controlled in a manner identical to those of interface control  10  as described above (see  FIGS. 2 ,  3 A,  3 B,  4 , and  5 ) and will thus not be described here. Interface control  65  possesses all of the advantages discussed above with respect to interface control  10 , including allowing users to control the operation of applications with simple and intuitive motions that closely emulate the natural motions of the human thumb and isolates positioning controls (1) from each other and (2) from trigger controls as described above. Likewise, interface control  65  may be also be provided with the friction coupling and feedback features described above. 
     The embodiments described above may be used in virtually any application which requires an interface control between a user and a machine. Embodiments in accordance with the present invention may be used to control the operation of a construction crane or boom. Interface controls  10  and  50  are ideal for replacing the mouse or trackball in computer software applications such as word processing, databases, and spreadsheets. For instance, interface control  50  of  FIG. 6  (see also  FIGS. 2 ,  3 A,  3 B,  4 , and  5 ) is well suited for use with video games. As described above, thumbpiece  28  may be used to control the positioning of a character in the video game. By depressing thumbpiece  28  so as to activate third sensor  44 , the user may implement various predetermined functions, such as starting/stopping the game and selecting game options. Switch  56 a ( 58 a for right-handed users) may, for instance, cause the character to jump. Switch  56 b ( 58 b) may cause the character to fire a bullet, and so on. 
     Embodiments of the present invention may also be incorporated into conventional two-banded video game controllers (see  FIG. 1 ) to provide a superior video game interface control. For example, positioning control keys  2 a,  2 b,  2 c, and  2 d ( FIG. 1 ) may be replaced by interface control  10 , as illustrated in FIG.  9 . Two-handed video game controller  90  has disposed within a first portion thereof a portion of interface control  10  of  FIGS. 2 ,  3 A,  3 B, and  4 . For purposes of clarity, not all of the components of interface control  10  are labelled. Arm member  20  and thumbpiece  28  control the positioning of objects (i.e., characters of a video game) displayed on a screen in the same manner as described previously with reference to  FIGS. 2 ,  3 A,  3 B, and  4 , while keys  4 a,  4 b, and  4 c implement various trigger functions. 
     The above described interface controls may be mounted in virtually any enclosure, including (but not limited to) control panels, automobile dashboards, steering wheels, or handgrips of other interface controls. For instance, in one such embodiment, base plate  14  ( FIG. 2 ) may be disposed within the handgrip portion of a floor-mounted lever arm control, i.e., a transmission selector in a vehicle, to provide users with a superior means to control such things as the vehicle&#39;s navigation system or communications with the vehicle&#39;s on-board computer system. 
     In another embodiment, interface controls in accordance with the present invention may be disposed within a control panel such as the dashboard of an automobile, boat, or even an airplane to provide control over certain operations. For example, interface control  10  may be mounted in the control panel of construction equipment to control the operation of a boom or crane. A control panel-mounted interface control  10  could also be used to manually control, for instance, the processing operations of an industrial application or the positioning and firing of lasers in medical applications. These embodiments, like those discussed above, are advantageous since multiple control functions (1) are disposed on a single contact surface and (2) are isolated from one another. 
     Some of the ergonomic advantages discussed herein may be compromised in order to provide a user interface control capable of controlling positioning in three, rather than two, directions. In one such embodiment in accordance with the present invention, various elements of interface control  10  may be incorporated into the handgrip of a conventional full-size joystick to provide three-dimensional positioning control as well as trigger functions. 
       FIG. 10  shows interface control  70  including gimballed stick  72  having fanned at one end an inclined, elongated upper portion  74 . Formed within top surface  76  of upper portion  74  is secondary interface control  80  which includes all the features of and operates in a similar manner to interface control  10  ( FIGS. 2 ,  3 A,  3 B, and  4 ). Secondary interface control  80  preferably has thumbpiece  28  fixably mounted within arm member  20  so that thumbpiece  28  may not slide along arm member  20 , thereby eliminating the need for second sensor  42  as well as grooves  34 a,  34 b and flanges  36 a,  36 b (FIG.  4 ). The other end of stick  72  ( FIG. 10 ) is pivotally mounted to a base portion (not shown) having sensors which generate first and second positioning signals in response to stick  72  pivoting with respect to the base portion, as discussed above in reference to conventional joystick controllers. 
     A user curls the four fingers of his or her hand around stick  72  and places the thumb in thumbpiece  28  (FIG.  10 ). The user controls the horizontal and vertical positioning of, for instance, a cursor displayed on a CRT in a conventional manner as described above, i.e., by pivoting stick  72  about the base portion. The user controls the depth positioning of the cursor with the thumb by pivoting arm member  20  about pivot point  22  (see FIG.  2 ). Trigger functions are activated by pressing downward on thumbpiece  28  (as discussed in reference to interface control  10 ). 
     Various forms of feedback may be added to the above described embodiments to provide a user with additional information about the particular application he or she is controlling, as described below in reference to  FIGS. 11 and 12 . For instance, arm member  20  of interface control  10  ( FIGS. 2 ,  3 A,  3 B, and  4 ) may be fitted with a first actuator that in response to a first feedback signal prevents arm member  20  from further pivoting in one or both directions or, in the alternative, alters the frictional contact between arm member  20  and baseplate  14  so as to alter the ease with which arm member  20  pivots. 
     Referring to  FIG. 11 , interface control  80 , the operation of which is identical to that of interface control  10 , includes all of the components of interface control  10  plus additional features described below. For purposes of clarity, not all of the components of interface control  80  common with those of interface control  10  are shown. Arm member  20  of interface control  80  has coupled thereto electromagnetic coil  82  which, in turn, is wound around a conventional ferrous core (not shown). Shaft  84  extends along arm member  20  and has a first end matingly coupled to surface  86  of sidewall  16 b. A second end of shaft  84  extends through coil  82  and is coupled to iron armature  88 . Armature  88  is preferably positioned as close to coil  82  as possible. When a first feedback current is provided to coil  82 , the resultant magnetic field produced by coil  82  attracts armature  88  towards coil  82 , thereby causing the first end of shaft  84  to shift towards and press against surface  86  of sidewall  16 b. The resultant increase in frictional coupling between arm member  20  and sidewall  16 b resists any pivoting movement of arm member  20  about point  22 . In other words, coil  82 , shaft  84 , and armature  88  act as a magnetically activated brake. Varying levels of feedback current will result in proportionally varying levels of drag. This brake may be implemented to simulate detents, stops, or other forms of reflective feedback. 
     In a similar manner, a second actuator may be provided that in response to a second feedback signal inhibits the movement of thumbpiece  28  along arm member  20 , as illustrated in FIG.  12 . Arm member  20  has provided therein a sliding bar  90  having a first end coupled to thumbpiece  28 . Iron core  92  is coupled to arm member  20  and is positioned in a region proximate to a second end of bar  90 . Magnetic coil  94  is wound around ferrous care  92 . A second feedback current provided to coil  94  will induce a magnetic attraction between bar  90  and against core  92 , thereby resulting in an increased frictional coupling between bar  90  and core  92 . This increased frictional coupling resists the sliding motion of thumbpiece  28  along arm member  20 . Note that in some embodiments shaft  40  ( FIG. 3A ) (not shown in  FIG. 12  for simplicity) may also serve the same function as bar  90  in addition to being part of the longitudinal sensing structure of arm member  20 . 
     The embodiments described above and illustrated in  FIGS. 11 and 12  would, for instance, be especially well suited for use with applications in which it is desirable to preclude a user from selecting certain options or moving a cursor into certain areas. In a video game application, for instance, the game&#39;s character may be precluded from entering a restricted area of the displayed image. The video game may issue feedback signals as discussed above to preclude the user from causing the character to move into the restricted areas. Thus, the feedback signals, by restraining or even preventing (1) arm member  20  from pivoting about point  22  and/or (2) thumbpiece  28  from sliding along arm member  20  directly inform the user he can no longer move in that direction. In a similar manner, an additional actuator may be contained within third sensor  44  (see  FIG. 3A ) to preclude activation of trigger functions at certain predetermined character positions. Unlike conventional interface control feedback systems which use flashing lights or sounds to warn users of an improper selection or movement, the direct force-reflecting feedback described above, by preventing the user from effecting certain positioning commands, provides a realistic feel to video games and other applications. 
     In other applications, interface control  80  ( FIG. 11 ) may be used to facilitate the selection of options or icons. As the user moves the cursor or pointer over an icon displayed on a screen, feedback, signals generated by the application may simulate a detent by increasing the frictional coupling between arm member  20  and sidewall  16 b and between thumbpiece  28  and arm member  20 , as described above with reference to  FIGS. 11 and 12 , when the cursor or pointer is positioned near or overlaps certain icons displayed on the screen. This simulated detent varies the amount of force the user must exert to effect further positioning changes in certain directions, i.e., the detent may either make it easier or harder for the user to cause the cursor to pass across the icon. In this manner, the user can “feel” when, he or she has reached a particular icon (or any other specific screen location). This simulated detent may be deactivated when, for instance, the icon has been selected or when the cursor has passed over the icon. 
     The actuators discussed above may comprise a solenoid, a servomotor, or any other suitable device known in the art which generates a force in response to electric signals. The actuators may also employ shape-memory alloys, piezo ceramics, or electro-rheological compounds. Further, motor-type actuators may be employed to augment or restrain motion. 
     In other embodiments, the actuators discussed above may used to activate and deactivate electrically controlled detents so as to provide tactile click stops in the pivoting motion of arm member  20  ( FIG. 2 ) about point  22  or in the linear motion of thumbpiece  28  along arm member  20 . These detents may be logically correlated with specific targets or options on a display screen such that once a particular option is selected, its corresponding detent is electrically deactivated. Adaptive feedback of this type can be very effective in making the above-described controls more intuitive. 
     Embodiments of the present invention may also be equipped with a spring return mechanism. With reference to interface control  10  (FIG.  2 ), a centering spring may be coupled to arm member  20  which causes arm member  20  to return to its center position whenever arm member  20  has deviated from the center position by exerting pressure on arm member  20 . A manually controlled latch may also be provided which engages the centering spring to and disengages the centering spring from arm member  20  so as to turn on and off the centering mechanism. Such a centering mechanism is useful in applications requiring proportional control (i.e., a conventional joystick) rather than absolute control (i.e., a mouse). The centering spring may also be electrically actuated by an external signal from the interfaced device (i.e., computer, video game, and so on). Inclusion of such an electrically actuated spring allows the interfaced device to switch the controller between two modes of operation (spring centering and non-centering), as the particular application may require. In a similar manner, an additional centering spring may be coupled to thumbpiece  28  to provide proportional control in the vertical direction. 
     While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention.