Increasing cursor control device sensitivity

An aircraft includes a cursor control device having a defined return path for the touch sensor so that the impedance in the return path is known. The defined return path is embodied in a conductive feature in the cursor control device palm contact area to ground the user and improve the system's signal to noise ratio. The defined return path normalizes signal variability due to environmental factors and user specific factors such as finger size, skin moisture, contaminants, etc.

BACKGROUND

Cursor control devices (CCD) used in aircraft such as onboard the Boeing 787 utilize a capacitive touch sensitive human interface device. Existing CCDs exhibit erratic behavior and even inoperability under certain circumstances. Variation in skin moisture and operating environment, contaminates, and even user body size can have an effect on how the touch sensor reacts. If the user has very dry skin, the CCD may not react to a touch at all.

A very high impedance in the return path of the touch sensor results in a very small signal amplitude; sometimes only a few millivolts. Variability in the signal amplitude due to environmental and user specific factors result in an unreliable system.

Consequently, it would be advantageous if an apparatus existed that is suitable for removing variability in touch sensor signals due to environmental and user specific factors.

SUMMARY

In one aspect, embodiments of the inventive concepts disclosed herein are directed to a CCD having a defined return path for the touch sensor so that the impedance in the return path is known. The defined return path is embodied in a conductive feature in the CCD palm contact area that grounds the user and improves the system's signal to noise ratio.

DETAILED DESCRIPTION

Broadly, embodiments of the inventive concepts disclosed herein are directed to a CCD having a conductive feature on the palm contact area to ground the user's hand, thereby producing a return path with a known impedance.

Referring toFIGS. 1-4, an environmental view, a side view, a perspective view, and a front view of an exemplary embodiment according to the inventive concepts disclosed herein are shown. In at least one embodiment, an aircraft100cockpit includes a cursor control device102. The cursor control device102includes a palm rest200and a touch sensitive screen300. In at least one embodiment, the touch sensitive screen300includes a capacitive touch sensor.

The touch sensitive screen300is sensitive to certain environmental and user specific factors due to the high impedance in the return path of the touch screen circuit, as more fully described herein. In at least one embodiment, a return path contact302is disposed in the palm rest200of the cursor control device102.

In at least one embodiment, the return path contact302comprises one or more metallic posts embedded in the palm rest200. Such metallic posts may comprise conductive hemispheres disposed on the palm rest200. The posts may include threaded shafts to attach the posts to the palm rests200and connect to ground inside the cursor control device102chassis. A number of these hemispheres would be placed in critical areas on the palm contact area. This approach could allow existing CCD's to be retrofitted by creating a tooling drill plate to locate the holes for the threaded hemispheres.

Alternatively, or in addition, the return path contact302comprises a metallic plate affixed to the palm rest200. The metallic plate may comprise Nickel, Stainless Steel, or other suitable material. Such conductive surface would be a large area for palm contact. Alternatively, the metallic plate may comprise a plurality of metallic strips in various areas of the palm rest200where palm contact is most likely. The metallic strips may be a few millimeters wide. Multiple strips spaced 10 millimeters or more may be used. Such metallic strips may protrude slightly above the surface of the palm rest200to provide a tactile feel to the user to anchor the user to the cursor control device102in rough air.

Alternatively, or in addition, the return path contact302comprises a conductive film applied to the palm rest200. The conductive film may comprise a graphene paint, conductive epoxy, metallic foil, or other conformable coating suitable as a contact in a return path of a circuit; paint or coating color and texture may be selected to minimize sunlight reflectance. In any case, the return path contact302is in electronic communication with internal circuitry as more fully described herein.

Alternatively, the entire front plate of the cursor control device102may be fabricated using an injection molded conductive plastic.

Referring toFIG. 5, a side, environmental view of an exemplary embodiment according to the inventive concepts disclosed herein is shown. In at least one embodiment, a cursor control device102with a return path contact in the palm rest200creates a first contact point502where the user's finger500contacts the touch sensitive screen and a second contact point504where some portion of the user's palm contacts the palm rest200.

Referring toFIG. 6, a block diagram of a circuit600according to an exemplary embodiment of the inventive concepts disclosed herein is shown. In at least one embodiment, the circuit600includes a touch sensitive screen comprising a stack of a printed wiring board602with copper contacts, a layer of FR4 material604, a layer of pressure sensitive adhesive606, a glass pane608, a layer of indium tin oxide610, and a sapphire coating612.

In at least one embodiment, a signal generator614is connected to the printed wiring board602. The signal generator614may be an alternating current source operating at approximately 50 kHz, and with a peak-to-peak voltage of approximately 10 v. Electronically, the user's finger616and indium tin oxide610layer comprise components of a first capacitor618where the sapphire coating612comprises an insulating dielectric layer. Likewise, the indium tin oxide610layer and copper contacts in the printed wiring board602comprise components of a second capacitor620where the FR4 material604, pressure sensitive adhesive606, and glass pane608comprise the insulating dielectric layer.

In at least one embodiment, the electrical characteristics of the user are modeled by a combination of a body resistor622and body capacitor624. Typically, the body resistor622is approximately 1 k ohms and the body capacitor624is approximately 100 pf. Further, the return path contact is modeled by a return path resistor626and return path capacitor628. The return path resistor626is connected to a grounded terminal of the signal generator614. The return path resistor626and return path capacitor628define a return path from the user's finger616to the signal generator614with a known, generally reduced impedance resulting in a more measurable, consistent output signal630with improved signal-to-noise ratio.

While the impedance of the return path may be reduced, isolation between the user and ground of up to 20 k ohms may still yield an improvement in cursor control device response.

While the specific embodiments disclosed herein have been directed toward touch sensitive systems in an aircraft, other embodiments may be directed toward non-aircraft implementations such as consumer devices.

It is believed that the inventive concepts disclosed herein and many of their attendant advantages will be understood by the foregoing description of embodiments of the inventive concepts disclosed, and it will be apparent that various changes may be made in the form, construction, and arrangement of the components thereof without departing from the broad scope of the inventive concepts disclosed herein or without sacrificing all of their material advantages; and individual features from various embodiments may be combined to arrive at other embodiments. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes. Furthermore, any of the features disclosed in relation to any of the individual embodiments may be incorporated into any other embodiment.