Self-calibration of force sensors and inertial compensation
First Claim
1. A personal electronics device, comprising:
- a force sensor including an input surface, the force sensor adapted to provide a sensor signal representative of a total force normal to the input surface measured by the force sensor, the force sensor including first and second sensor plates;
a first accelerometer adapted to provide a first accelerometer signal representative of acceleration of the first sensor plate;
a second accelerometer adapted to provide a second accelerometer signal representative of acceleration of the second sensor plate; and
inertial compensation circuitry coupled to the first and second accelerometers and the force sensor, the inertial compensation circuitry adapted to;
receive the sensor signal and the first and second accelerometer signals;
determine an inertial compensation signal based on the first and second accelerometer signals and at least one inertial compensation parameter of the force sensor, the inertial compensation signal representative of an inertial force measurable by the force sensor; and
bias the sensor signal responsive to the inertial compensation signal to generate an acceleration compensated force signal.
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Abstract
A method of calibrating a force sensor that includes an input surface and an array of sensing elements. The input has a number of test locations and is deformable under applied force. The force sensor is mounted in a predetermined test orientation. For each test location of the plurality of test locations on the input surface of the force sensor a predetermined test force to the test location. An element calibration value is measured for each sensing element of the array of sensing elements of the force sensor. An (x, y) deformation map of the input surface of the force sensor corresponding to the application of the predetermined test force to the test location is determined based on the measured element calibration values.
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Citations
26 Claims
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1. A personal electronics device, comprising:
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a force sensor including an input surface, the force sensor adapted to provide a sensor signal representative of a total force normal to the input surface measured by the force sensor, the force sensor including first and second sensor plates; a first accelerometer adapted to provide a first accelerometer signal representative of acceleration of the first sensor plate; a second accelerometer adapted to provide a second accelerometer signal representative of acceleration of the second sensor plate; and inertial compensation circuitry coupled to the first and second accelerometers and the force sensor, the inertial compensation circuitry adapted to; receive the sensor signal and the first and second accelerometer signals; determine an inertial compensation signal based on the first and second accelerometer signals and at least one inertial compensation parameter of the force sensor, the inertial compensation signal representative of an inertial force measurable by the force sensor; and bias the sensor signal responsive to the inertial compensation signal to generate an acceleration compensated force signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of inertial compensation for a force sensor included in a personal electronics device, the force sensor including an input surface and first and second sensor plates, the method comprising:
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characterizing the force sensor to determine at least one inertial compensation parameter of the force sensor; measuring a first acceleration value of the first sensor plate; measuring a second acceleration value of the second sensor plate; determining an inertial force offset value based on the measured first acceleration value of the first sensor plate, the second acceleration value of the second sensor plate, and the at least one inertial compensation parameter of the force sensor; measuring a force value for a force applied to the input surface of the force sensor; and calculating an acceleration compensated force value based on the force value and the inertial force offset value. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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22. A personal electronic device, comprising:
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a housing; a display elastically coupled to the housing; a force sensor coupled to the display, the force sensor including first and second sensor plates; a first accelerometer; a second accelerometer; and circuitry coupled to the force sensor and the first and second accelerometers operable to; receive a force signal from the force sensor indicating an amount of force exerted on the display; receive a first acceleration signal from the first accelerometer indicating a first acceleration of the first sensor plate; receive a second acceleration signal from the second accelerometer indicating a second acceleration of the second sensor plate; and generate an inertially compensated force signal by adjusting the amount of force indicated by the force signal using the first and second acceleration signals. - View Dependent Claims (23, 24, 25, 26)
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Specification