Force Sensor Activity 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 sensor 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
1Reliability
If force sensing systems operate continuously with high sensitivity to detect user interactions, then detection responsiveness is improved, but power consumption increases
Solution Approach 1:
The system dynamically adjusts its operating state between low-power mode and high-sensitivity detection mode. The activity detection stage continuously monitors sensor inputs at low power consumption, and only activates the full event detection stage when user interaction is detected, thus adapting the system's detection capability to actual usage conditions.
Solution Approach 2:
The system employs periodic monitoring through the activity detection stage that continuously checks sensor inputs at intervals. This periodic action allows the system to maintain awareness of user interactions while consuming minimal power between detection cycles, activating full processing only when necessary.
2Volume of moving object
If force sensors are made smaller to reduce device size, then device compactness is improved, but sensor sensitivity deteriorates
Solution Approach 1:
The system replaces traditional mechanical force sensors with capacitive sensors that detect user interactions through changes in capacitance rather than mechanical deformation. This substitution enables smaller sensor footprint while maintaining detection sensitivity, as capacitive sensing does not require the same mechanical structure as traditional force sensors.
Solution Approach 2:
The system changes the detection parameter from mechanical force to electrical capacitance. By measuring capacitance changes rather than mechanical displacement, the system achieves comparable sensitivity with significantly reduced sensor size, allowing for more compact device design.
3Measurement precision
If activity detection stage continuously monitors all sensor inputs, then user interaction detection accuracy is improved, but power consumption increases
Solution Approach 1:
The detection system is segmented into two distinct stages: an activity detection stage that performs continuous low-power monitoring, and an event detection stage that performs detailed analysis only when needed. This segmentation allows the system to maintain detection accuracy while minimizing power consumption by distributing processing tasks across different operational phases.
Solution Approach 2:
The activity detection stage performs partial monitoring of sensor inputs, checking for basic activity indicators without executing full event detection algorithms. This partial action maintains sufficient detection accuracy for distinguishing active vs. inactive states while consuming significantly less power than continuous full-scale monitoring.
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.