Force Sensor Wake Detection for Low-Power User Input Sensing
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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
Engineering Contradiction Analysis
1Measurement precision
If force sensing systems operate with high sensitivity and responsive performance, then user interaction detection capability is improved, but power consumption increases
Solution Approach 1:
The system dynamically adjusts its operational state between active sensing and low-power sleep modes. The force sensors and processing circuits are enabled only when user interaction is detected, and disabled during periods of no activity, allowing the system to maintain high sensitivity when needed while minimizing power consumption during idle periods.
Solution Approach 2:
The system employs periodic sampling of force sensor data at different rates depending on the operational state. During active periods, high-rate sampling provides responsive detection, while during sleep periods, lower-rate or event-triggered sampling reduces power consumption while maintaining the ability to detect user interactions.
2Speed
If force sensing systems operate always-on for responsive performance, then user interaction detection speed is improved, but power consumption increases
Solution Approach 1:
The system transitions between dynamic operational states (active and sleep modes) based on detected activity. This allows the system to achieve fast response times when user interaction occurs while minimizing power consumption during idle periods by disabling sensors and processing circuits.
Solution Approach 2:
The system uses the force sensor data itself to trigger state transitions. When the sensor detects a force exceeding a threshold, it automatically wakes the system from sleep mode, eliminating the need for continuous operation while ensuring rapid response to actual user interactions.
3Use of energy by moving object
If power consumption is minimized through sleep modes, then energy efficiency is improved, but detection responsiveness deteriorates
Solution Approach 1:
The system uses periodic or event-triggered sampling during sleep mode to detect user interactions. When a force event is detected, the system transitions to active mode for full processing, maintaining energy efficiency while preserving the ability to respond to user inputs.
Solution Approach 2:
The force sensor operates in a self-triggering manner during sleep mode, automatically waking the system when user interaction is detected. This ensures that the system remains responsive to actual user inputs while minimizing power consumption during idle periods.
Data Source
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.