Abstract:
In accordance with one embodiment of the present disclosure, a method for controlling an aircraft by a hands on throttle-and-stick (HOTAS) includes selectively connecting, by the HOTAS, two interfaces of a controller for the aircraft. The selective connection is made through one of a plurality of possible paths. Each path has an expected respective voltage drop within a predetermined range. The selected one of the possible paths connecting the two interfaces is determined by determining an actual voltage drop associated with the selected path. A control operation for the aircraft is effected by the controller based on the determined selected path. The method reduces the number of required electrical connections.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/890,739 entitled “Manual Human Interface to Electronics,” which was filed on Feb. 20, 2007. 
    
    
     TECHNICAL FIELD 
     This disclosure relates in general to control systems, and more particularly to manual human interfaces to electronics. 
     BACKGROUND 
     Many electronic systems use manual human interface controls. For example, hands on throttle-and-stick (HOTAS) is a style of aircraft cockpit Human-Machine Interaction (HMI) that allows the pilot to access the cockpit functions and fly the aircraft. Similar HOTAS systems have also been adapted for game controllers used for flight simulators. The gaming industry includes many other types of manual controllers. The steering wheels of modern open-wheel racecars, like those used in Formula One and the Indy Racing League, sometimes include sophisticated manual controls. There is generally a tradeoff between the complexity of manual controls and cost. 
     SUMMARY 
     In accordance with one embodiment of the present disclosure, a method for controlling an aircraft by a hands on throttle-and-stick (HOTAS) includes selectively connecting, by the HOTAS, two interfaces of a controller for the aircraft. The selective connection is made through one of a plurality of possible paths. Each path has an expected respective voltage drop within a predetermined range. The selected one of the possible paths connecting the two interfaces is determined by determining an actual voltage drop associated with the selected path. A control operation for the aircraft is effected by the controller based on the determined selected path. The method reduces the number of required electrical connections. 
     Some embodiments of the disclosure implement additional control inputs, such as multi-position switches, on to stick grips and throttle handles without additional wire paths into and through control sticks and throttle quadrants. Some such embodiments may use existing connector interfaces to control boxes for backward compatibility. 
     Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIGS. 1A through 1C  are perspective views of a Hands On Throttle And Stick (HOTAS) interface that forms a portion of a control system according to one embodiment; and 
         FIG. 2  is a schematic for an electrical circuit that forms a portion of the control system of  FIGS. 1A through 1C  according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The example embodiments of the present disclosure are best understood by referring to  FIGS. 1A through 2  of the drawings, like numerals being used for like and corresponding parts of the various drawings. 
       FIGS. 1A through 1C  are perspective views of a Hands On Throttle And Stick (HOTAS) interface  100  that forms a portion of a control system according to one embodiment. The control system of the illustrated example generally includes two distinct parts communicatively coupled together: the HOTAS interface  100  that may be manipulated by a pilot, co-pilot, and/or crew member (collectively referred to herein as “pilot”), and the avionics equipment that receives and interprets the pilot manipulation (e.g., electronic circuitry illustrated in  FIG. 2 ). 
     Interface  100  generally includes a plurality of control inputs  110 - 180  coupled to a control stick grip  160 . In this example, each of the eight control inputs  110 ,  120 ,  130 ,  140 ,  150 ,  160 ,  170 , and  180  has a corresponding function. For example, control input  120  may be used for aircraft trim, control input  150  may be used for target management, control input  170  may be used as a weapons trigger, and so forth. In addition, some control inputs may be manipulated between multiple positions (e.g., control  120  has four possible switch positions in addition to a neutral position) and other control inputs may be manipulated between on and off positions (e.g., control input  180  may be manipulated to an on position by pressing a button). In operation, therefore, interface  100  generally enables the pilot to access the various cockpit functions and fly the aircraft. Interface  100  is ergonomically designed to facilitate the accessibility and manipulation of each control, thus enabling a pilot to maintain continual view of the horizon and a Heads Up Display (HUD). Such a feature may improve the pilot&#39;s situational awareness, the pilot&#39;s ability to change control settings in turbulence and high acceleration maneuvers, and improve the pilot&#39;s reaction time. 
     As shown in  FIG. 1C , the base  195  of interface  100  includes a plurality of conduits through which wires may extend. Signals may propagate along the wires to communicate pilot manipulation of interface  100  to avionics equipment capable of interpreting the signals and controlling the aircraft accordingly, as described further below with reference to  FIG. 2 . Adding additional Hands On Throttle And Stick (HOTAS) controls with multiple-position switches may enable pilots to make better use of advances in avionics. One way to add additional HOTAS switches or interfaces is to add additional wires to the aircraft through the control sticks and throttle fixtures. Adding additional wires, however, typically increases costs associated with development and implementation. For example, HOTAS systems in military aircraft normally have little room for additional wires and are commonly expensive items to modify. In addition, the circuitry that interfaces with the additional wires typically uses additional connector interfaces to control boxes. 
     Accordingly, some embodiments of the disclosure implement additional control inputs on to stick grips and throttle handles (e.g., interface  100 ) without additional wire paths into and through control sticks and throttle quadrants. Some such embodiments may use existing connector interfaces to control boxes for backward compatibility. For example, the illustrated HOTAS interface  100  may be designed to mate with the physical and electrical interfaces of existing B-8 grips currently used by various military aircraft models, through such B-8 HOTAS interfaces conventionally only have five buttons/switches as compared to the eight control inputs  110 - 180  of the illustrated example. One such example implementation that does not increase the number of wire paths into and through interface  100  over that used by B-8 HOTAS interfaces is described further below with reference to  FIG. 2 . 
       FIG. 2  is a schematic for an electrical circuit  200  that forms a portion of the control system of  FIGS. 1A through 1C  according to one embodiment. As shown in  FIG. 2 , a respective portion of circuit  200  couples the switch terminals of each control input  110 - 180  to at least two respective pin interfaces of avionics equipment  202 . In this example, avionics equipment  202  generally includes a seventeen-pin electrical interface, a detector that is generally capable of determining an actual voltage drop associated with a particular manipulation(s) of control inputs  110 - 180 , and a controller that is capable of generating control signals, based on the determination, that effect a control operation for the aircraft. 
     In various embodiments, avionics equipment  202  may be backwards compatible with existing control systems, such as the seventeen-pin interface of the B-8 military aircraft control system. In addition, the interfacing avionics equipment  202  may also function as the Multi-Function Color Display (MFCD). In operation, circuit  200  generally generates electrical signals that enable avionics equipment  202  to precisely determine the various manipulations of control inputs  110 - 180  by a pilot. 
     In this example, control input  120  is a four-way thumb switch with four wires attached to respective position contacts (e.g., up, down, left, and right) and a fifth wire for the common terminal of the switch. Moving the switch to any of the four positions causes the common terminal to establish electrical continuity with the appropriate terminal corresponding to the selected position. In this manner, the five wires connected to the switch terminals of control input  120  route electrical signals to the appropriate pin interfaces A, E, B, C, and P of avionics equipment  202 , which interfaces with the wires and determines changes in the electrical continuity of the circuit caused by pilot manipulation of control input  120 . In some embodiments, the five-wire configuration of control input  120  may provide enhanced reliability and sensitivity to pilot manipulation, and thus may be suitable in some applications for critical flight control functionality, such as aircraft trim. In some embodiments, however, it may be cost prohibitive to wire each multi-contact switch with five wires. Moreover, doing so may further complicate backwards compatibility with existing electronic interfaces. 
     As shown in  FIG. 2 , some of the control inputs  140 ,  150 , and  160  use only two wires to service a four-way switch. More specifically, circuit  200  electrically couples the four-way switch terminals of control inputs  140 ,  150 , and  160  to respective pin interfaces R, G, K, D and M of avionics equipment  202  using only two wires per control input  140 ,  150  and  160 . Resistors  205 - 265  are incorporated into the design such that the various positions of each switch insert a specific resistance into circuit  200 . 
     Resistance values of resistors  205 - 265  may be selected such that sensing circuitry of avionics equipment  202  can reliably distinguish the resulting voltages established in circuit  200  when electrical contact is made by activating the switch. For example, resistors  205 ,  210 ,  215 , and  220  coupled to the switch terminals of control input  150  may have resistance values of 1.43 kiloohms, 8.45 kiloohms, 4.12 kiloohms, and 16.5 kiloohms, respectively. Similarly, resistors  225 ,  230 ,  235 ,  240  coupled to the switch terminals of control input  140  may have resistance values of 8.45 kiloohms, 4.12 kiloohms, 16.5 kiloohms, and 1.43 kiloohms, respectively; the resistors  245 ,  250 ,  255 ,  260 , coupled to the switch terminals of control input  160  may have the values of 1.43 kiloohms, 8.45 kiloohms, 4.12 kiloohms, and 16.5 kiloohms, respectively; and resistor  265  coupled to a switch terminal of control input  130  may have the value of 38.3 kiloohms. The above resistance values are for example purposes only and any of a variety of alternative resistance values may be used. In addition, the various multi-contact control inputs  140 ,  150 , and  160  need not necessarily use resistors  205 - 260  having the same or similar resistance values, though designing circuit  200  in this manner may reduce costs and simplify design. In this example, resistors  205 - 265  are integrated within interface  100 ; however, in various alternative embodiments resistors  205 - 265  may not be integrated within interface  100 , though some such embodiments may have additional wires extending into and through interface  100 . 
     By designing circuit  200  such that the common terminal of each control input is connected to electrical ground, two wires may be used to service multiple positions. If multiple control inputs share the same common ground (e.g., control inputs  130 ,  140 ,  150 , and  160  share the same common ground), “N” number of control inputs may be efficiently serviced with just “N+1” wires. Further, two switches that are impossible or even just unlikely to be operated by the pilot at the same time can share the non-common wire between them. 
     Thus, as shown in  FIG. 2 , circuit  200  may be designed to service a control system of eight control inputs  110 - 180  using the same number of wires extending into and through control interface  100  as previous designs that serviced fewer control inputs. This feature not only reduces costs and design complexity, but may enable backwards compatibility with existing connector interfaces to control boxes. 
     Although the present disclosure has been explained in the context of an aircraft HOTAS system, the teachings of the present disclosure also apply to any of a variety of alternative human interfaces to electronics. For example, the teachings of the present disclosure may also apply to the steering wheels of modern automobiles (e.g., those used in Formula One and the Indy Racing League, luxury sports cars, etc.). In addition, the teachings may also be adapted for game controllers (e.g., controllers used for flight simulators, other multi-input game controllers, etc.). 
     Although the present disclosure has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.