Force Sensor Input Detection With Low-Power Activity Gating

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Solution Overview

Problem

Existing force sensing systems in mobile devices face challenges in balancing low power consumption with responsive performance while maintaining acceptable sensitivity and size, particularly in detecting user interactions with human-machine interfaces.

Innovation Solution

A force sensing system comprising an input channel, activity detection stage, and event detection stage, which includes a sensor conditioning stage for normalizing and filtering inputs from force sensors, and a thresholding module for determining user inputs, allowing for power-gated operation to minimize power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If force sensing system operates always-on to provide responsive performance, then detection responsiveness is improved, but power consumption increases

Engineering Contradiction:

Improvedetection responsivenessVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The system dynamically adjusts its operational state between active and sleep modes based on detected activity levels. The activity detection stage continuously monitors sensor inputs at low power, and only activates the full event detection stage when activity exceeds a threshold, enabling the system to be responsive when needed while conserving power during idle periods

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system employs periodic sampling of sensor data at different rates depending on operational state. During normal operation, sensors are sampled at a lower rate to reduce power consumption, while during active states following activity detection, sampling rate increases to ensure responsive event detection, creating a periodic alternation between low and high power states

Inventive Principle:

Principle #19Periodic action

2Use of energy by moving object

If force sensing system reduces power consumption through sleep modes, then energy efficiency is improved, but detection responsiveness deteriorates

Engineering Contradiction:

Improveenergy efficiencyVSAvoiddetection responsiveness

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The activity detection stage performs preliminary monitoring of sensor inputs even in low-power states, detecting potential events before they require full system activation. This preliminary action ensures that when an actual event occurs, the system is already prepared to respond immediately, eliminating wake-up delays while still maintaining low power consumption during idle periods

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The activity detection stage serves as an intermediary between the low-power sleep mode and the high-power event detection stage. It continuously monitors sensor data at minimal power consumption and acts as a trigger mechanism that activates the full event detection system only when necessary, thereby maintaining responsiveness without requiring the entire system to remain always-on

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If mechanical buttons are used for user interface, then user interaction feedback is improved, but device reliability deteriorates due to wear and tear

Engineering Contradiction:

Improveuser interaction feedbackVSAvoiddevice longevity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces mechanical button systems with a force sensing system that uses capacitive or piezoresistive sensors to detect user inputs. This substitution eliminates moving parts and mechanical wear while maintaining the ability to detect press events, providing a solid-state solution that improves reliability while preserving user interaction capabilities through virtual buttons that can simulate mechanical feedback

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If virtual buttons are used instead of mechanical buttons, then device reliability is improved, but user interaction realism deteriorates

Engineering Contradiction:

Improvedevice longevityVSAvoiduser interaction realism

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system incorporates haptic feedback mechanisms including linear resonant actuators that generate vibrations in response to detected force events. When the force sensor detects a user press, the LRA activates to produce tactile feedback that simulates the sensation of a mechanical button click, thereby restoring realism to the user interaction experience while maintaining the reliability benefits of having no mechanical buttons

Inventive Principle:

Principle #18Mechanical vibration

Data Source

PatentUS10860202B2Force sensing system and method

Publication Date: 2020.12.08 CIRRUS LOGIC INC

AI summary

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.