Force sensing system and method

Patent metadata

Field	Value
Publication number	US-10860202-B2
Application number	US-201916422543-A
Country	US
Kind code	B2
Filing date	May 24, 2019
Priority date	Oct 26, 2018
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

A force sensing system for determining if a user input has occurred, the system comprising: an input channel, to receive an input from at least one force sensor; an activity detection stage, to monitor an activity level of the input from the at least one force sensor and, responsive to an activity level which may be indicative of a user input being reached, to generate an indication that an activity has occurred at the force sensor; and an event detection stage to receive said indication, and to determine if a user input has occurred based on the received input from the at least one force sensor.

First claim

The invention claimed is:

1. A force sensing system for determining if a user input has occurred, the system comprising:
an input channel, to receive an input from at least one force sensor;
an activity detection stage, to monitor an activity level of the input from the at least one force sensor and, responsive to an activity level which may be indicative of a user input being reached, to generate an indication that an activity has occurred at the force sensor; and
an event detection stage to receive said indication, and to determine if a user input has occurred based on the received input from the at least one force sensors;
wherein the event detection stage comprises a comparison stage arranged to compare the received indication against a stored touch event model, and to determine if a user input has occurred based on the comparison;
wherein the touch event model comprises a support-vector machine model;
wherein the event detection stage is configured to determine based on the comparison against the touch event model whether the user input corresponds to a defined type of user input or a defined sequence of defined types of user input;
wherein the event detection stage is operable, dependent on a defined type of user input to which a first received said indication is determined to correspond, to adapt the support-vector machine model for a second received said indication.

2. The system of claim 1 , wherein the system further comprises:
a sensor conditioning stage, to perform conditioning of an input received from the input channel to provide a conditioned force sense signal, wherein the activity detection stage performs the activity level monitoring on the conditioned force sense signal.

3. The system of claim 2 , wherein the system is configured to receive inputs from multiple force sensors, preferably the sensor conditioning stage is configured to determine an inverse correlation matrix of the inputs received from the input channel, to determine a sensor diagonalization of the inputs received from the input channel.

4. The system of claim 1 , configured in an anomaly-detection operation to determine whether an input from the at least one force sensor, or an average or other combination or cross-correlation of inputs from respective force sensors, has a characteristic indicative of an anomalous user input,
optionally wherein the characteristic comprises the amplitude being negative and optionally the magnitude being greater than a threshold value.

5. The system of claim 4 , configured in the anomaly-detection operation to employ a mapping function to map said amplitude to a value within a predefined range of values,
optionally wherein the mapping function comprises a sigmoid function.

6. The system of claim 4 , configured, if it is determined in the anomaly-detection operation that said characteristic is present, to:
operate in an anomaly mode; and/or
disable one or more functions; and/or
sample the at least one force sensor at a given anomaly-mode sample rate; and/or
operate using anomaly mode system parameters.

7. The system of claim 1 , configured in an anomaly-detection operation to determine whether an input from the at least one force sensor, or an average or other combination or cross-correlation of inputs from respective force sensors, has a characteristic indicative of an anomalous user input by comparison against an anomaly-detection model which comprises a support-vector machine model defined by a support-vector machine classification algorithm.

8. The system of claim 1 , wherein the activity detection stage comprises a thresholding module, the thresholding module configured to determine if the activity level of the input from the at least one force sensor or of the conditioned force sense signal exceeds at least one threshold, wherein if the activity level exceeds the at least one threshold the activity detection stage determines that an activity has occurred at the force sensor.

9. The system of claim 8 , wherein one said threshold is a noise threshold, and wherein the thresholding module is configured to derive the noise threshold adaptively based on a running estimate of noise in the input from the at least one force sensor.

10. The system of claim 9 , wherein the thresholding module is configured to calculate a current value of the threshold based on a combination of a previous value of the noise threshold and a current value of the input from the at least one force sensor,
optionally wherein said combination is a weighted sum,
and optionally wherein the weighted sum is defined by a first weighting when the values of the input from the at least one force sensor are falling and a second weighting different from the first weighting when the values of the input from the at least one force sensor are rising.

11. The system of claim 8 , wherein the system further comprises a feature extraction module configured to extract features from a monitored signal, the monitored signal comprising the input from the at least one force sensor or the conditioned force sense signal.

12. The system of claim 11 , wherein the thresholding module is further configured to perform at least one of the following:
compare the rate or rise and/or fall of the monitored signal against a corresponding rise threshold and/or a fall threshold indicative of an activity occurring at the sensor;
compare an active duration of the monitored signal against a minimum and/or maximum duration threshold indicative of an activity occurring at the sensor; and
compare the monitored signal against defined classified parameters to determine whether an activity has occurred at the sensor.

13. The system of claim 11 , wherein the feature extraction module is power gated by the thresholding module, such that the feature extraction module is enabled if the power level of the monitored signal exceeds a power level threshold indicative of an activity occurring at the sensor.

14. The system of claim 1 , wherein the support-vector machine model is defined by a support-vector machine classification algorithm.

15. The system of claim 1 , wherein the event detection stage is configured to
output an indication of the defined type, or defined sequence of defined types, to which the user input corresponds.

16. The system of claim 1 ,
wherein said support-vector machine model is adapted for the second one of said received indications to:
increase a probability of a defined sequence of defined types of user input being determined to have occurred based on the first and second said received indications; or
increase a probability of the second one of said received indications being determined to correspond to a defined type of user input whereby the first and second received indications are determined to correspond to said defined sequence of defined types of user input.

17. The system of claim 1 , wherein the event detection stage is configured to detect the type of user input that has occurred, by comparison of the received indication with a stored touch event model, to distinguish between:
a tap event (e.g. greater than ¼ second duration and less than ½ second duration);
a press event (e.g. greater than ½ second duration),
wherein the event detection stage is arranged to output an indication of the type of user input that has been detected.

18. The system of claim 1 , wherein the system further comprises a calibration and diagnostics stage which is configured to receive the output of the input channel and/or the output of the sensor conditioning stage and to determine

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Sepehr Hamid
• Peso Parada Pablo
• Zwart Willem
• Birchall Tom
• Kost Michael Allen
• Das Tejasvi
• Maru Siddharth
• Beardsworth Matthew
• Duewer Bruce E

Classifications

• H03K17/9625

  using a force resistance transducer · CPC title

• H04M2250/22

  including a touch pad, a touch sensor or a touch detector · CPC title

• G06F2203/04105

  Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position · CPC title

• G06F3/0488 Primary

  using a touch-screen or digitiser, e.g. input of commands through traced gestures · CPC title

• G06F3/0416

  Control or interface arrangements specially adapted for digitisers · CPC title