Hybrid force sensitive touch devices
A hybrid touch-screen display that integrates force-based touch-screen technology with any one from among a group of projective capacitive, surface capacitive, resistive, digital resistive, SAW, IR, APR, DST, optical and electromagnetic touch-screen technologies to provide an ability to compensate for non-perfect force transfer. An alternate implementation is also disclosed that employs a single force sensor for relative force measurement in a system in which force is traditionally not measured, here a water dispenser unit. This allows compensation for varying static loads, run-time calibration, and filtering of extraneous loads through firmware.
1. A touch-sensitive display assembly adapted to calculate coordinates of a touch in a coordinate plane as well as a force of the touch along a z-axis, the touch-sensitive display assembly comprising:
a housing;
a frame coupled to the housing;
a touch display screen in the housing and exposed through the frame, the touch display screen adapted to calculate coordinates of the touch in a coordinate plane using one or more sensors;
a support structure underlying the touch display screen;
at least one force sensor underlying the support structure, the at least one force sensor adapted to determine a force of the touch perpendicular to the coordinate plane; and
a control system comprising a non-transitory computer memory for storing instructions for:
determining the coordinates of the touch in the coordinate plane from the touch display screen;
determining a force component of the touch perpendicular to the coordinate plane from the force sensor;
subdividing an area of the touch display screen into a plurality of concentric areas; and
computing an absolute touch pressure at the determined coordinates in the coordinate plane by compensating the force component as a function of the predefined concentric area within which the touch occurred.
2. The touch-sensitive display assembly according to claim 1 , wherein the at least one force sensor is a corner-mounted force-based sensor.
3. The touch-sensitive display assembly according to claim 1 , wherein the at least one force sensor is surface-mounted on the back of the support structure.
4. The touch-sensitive display assembly according to claim 1 , wherein the at least one force sensor is mounted on a printed circuit board inside the housing.
5. The touch-sensitive display assembly according to claim 1 , further comprising rubberized padding between the housing and touch sensitive display screen.
6. The touch-sensitive display assembly according to claim 5 , wherein the rubberized padding comprises a continuous rectangular gasket.
7. The touch-sensitive display assembly according to claim 6 , wherein the continuous rectangular gasket comprises silicon.
8. The touch-sensitive display assembly according to claim 6 , wherein the rubberized padding imposes a predetermined preload force to the touch sensitive display screen to minimize impact from shock and vibration.
9. The touch-sensitive display assembly according to claim 1 , wherein the at least one force sensor comprises a force sensing resistive sensor.
10. The touch-sensitive display assembly according to claim 1 , wherein the at least one force sensor comprises a piezo resistive sensor.
11. The touch-sensitive display assembly according to claim 1 , wherein the at least one force sensor comprises a force transducing rubber sensor.
12. The touch-sensitive display assembly according to claim 1 , wherein the control software ignores a touch if the absolute touch pressure is below a predetermined minimum threshold.
13. The touch-sensitive display assembly according to claim 1 , wherein the control software computes a first set of touch coordinates from the force sensing sensors, and a second set of coordinates from the touch sensitive display screen.