Automatic Field Calibration of Force Input Sensors

• US 20170090667A1
• Filed: 09/24/2015
• Published: 03/30/2017
• Est. Priority Date: 09/24/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Abdollahian, Golnaz, Westerman, Wayne C.
• Granted Patent: US 10,416,811 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01L 5/0066 Calibration arrangements
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment

Abstract

Systems and methods for calibrating a force input device are disclosed. The force input device includes a force-sensitive structure with a number of individual force sensors that compress or expand in response to input. The force input device measures an electrical property of the force sensors of the force-sensitive structure. After the force sensors are measured, the values obtained are adjusted based on a mechanical model of the response of the force sensitive structure. Upon receiving a force input event of high magnitude, the force input device recalibrates the mechanical model.

Claims

1. An input sensor comprising:

a force-sensitive structure coupled to a substrate and comprising a plurality of force sensors, each force sensor coupled to a separate area of the substrate;

an input resolver in communication with the force-sensitive structure and configured to;

measure an output by each force sensor when a compressive force is applied to an input location of the substrate;

modify the measurement of each force sensor based on an output of a mechanical model of the force-sensitive structure upon determining that the magnitude of force applied at the input location does not exceed a selected threshold; and

update the mechanical model of the force-sensitive structure upon determining that the magnitude of force applied at the input location exceeds the selected threshold, and output the measurements of each force sensor as a force input to the electronic device.

2. The input sensor of claim 1, wherein the mechanical model is configured to independently predict the output of each force sensor based in part on the location of each respective force sensor within the force-sensitive structure.

3. The input sensor of claim 1, wherein the mechanical model is configured to independently predict the output of each force sensor based in part on a material property of the substrate.

4. The input sensor of claim 1, wherein the mechanical model is configured to independently predict the output of each force sensor based in part on a material property of a frame to which the substrate is coupled.

5. The input sensor of claim 1, wherein the substrate is formed from glass or sapphire.

6. An input sensor comprising:

a force-sensitive structure coupled to a substrate and having an electrical property that changes as a function of a magnitude of force to the substrate;

an input resolver in communication with the force-sensitive structure and configured to update a mechanical model of the force-sensitive structure upon determining that the force-sensitive structure has received a magnitude of force input that exceeds the selected threshold.

7. The input sensor of claim 6, wherein the force-sensitive structure comprises an arrangement of independent force sensors each having an electrical property that changes as a function of a magnitude of force applied to the independent force sensor.

8. The input sensor of claim 7, wherein the arrangement of independent force sensors are organized as a two-dimensional grid.

9. The input sensor of claim 7, wherein the mechanical model is configured to predict the output of each independent force sensor of the arrangement of independent force sensors in response to an application of a selected unit of force.

10. The input sensor of claim 7, wherein the mechanical model is configured to predict the output of each independent force sensor of the arrangement of independent force sensors based in part on the position of the independent force sensor within the force-sensitive structure.

11. The input sensor of claim 7, wherein the mechanical model is configured to predict the output of each independent force sensor of the arrangement of independent force sensors based in part on a material property of a material forming at least a portion of each independent force sensor.

12. The input sensor of claim 7, wherein the mechanical model is configured to predict the output of each independent force sensor of the arrangement of independent force sensors based in part on a material property of the substrate.

13. The input sensor of claim 7, wherein the mechanical model is configured to predict the output of each independent force sensor of the arrangement of independent force sensors based in part on a material property of a frame to which the substrate is coupled.

14. The input sensor of claim 6, wherein the output of the mechanical model depends, at least in part, on the location of the force applied.

15-24. -24. (canceled)

25. An electronic device comprising:

a housing;

an input surface coupled to the housing;

an input sensor comprising a force-sensitive structure coupled to the input surface, the input sensor having an electrical property that changes as a function of a magnitude of force applied at a location on the input surface;

an input resolver coupled to the input sensor and configured to;

measure the electrical property of the force-sensitive structure;

modify the measurement based on a mechanical model of the force-sensitive structure upon determining that the measurement corresponds to a magnitude of force that does not exceed a selected threshold; and

update the mechanical model of the force-sensitive structure upon determining that the measurement corresponds to a magnitude of force that exceeds the selected threshold.

26. The electronic device of claim 25, wherein the electronic device is a cellular phone, a tablet computer, or a wearable electronic device.

28. The electronic device of claim 25, wherein the mechanical model is updated, at least in part, based on the location of the force applied.

29. The electronic device of claim 25, wherein the force-sensitive structure has a variable resistance.

30. The electronic device of claim 25, wherein the force-sensitive structure has a variable capacitance.

31. The electronic device of claim 25, wherein at least a portion of the input surface is optically transparent.

27. (canceled)

32-40. -40. (canceled)