Wearable On-Wrist Detection via Temperature Gradient Sensing
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Solution Overview
Problem
Existing wearable device systems face inaccuracies and high power consumption when detecting whether they are worn by a user, particularly due to the reliance on continuous sampling of optical sensors which can lead to false positives and reduced battery life.
Innovation Solution
The integration of temperature sensors to determine the on-wrist or off-wrist state by measuring temperature differences between sensors on opposite surfaces of the device, with the option to use optical sensors during isothermal conditions or verify the results, thereby reducing power consumption and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors are continuously sampled to determine on-wrist or off-wrist state, then detection accuracy can be maintained, but power consumption increases and battery life decreases
Solution Approach 1:
The patent implements periodic sampling of optical sensors instead of continuous sampling, where the sampling occurs at specific intervals or under specific conditions (e.g., when temperature gradient indicates potential on-wrist state). This reduces the overall power consumption while maintaining adequate detection accuracy by sampling at strategically chosen moments rather than continuously.
Solution Approach 2:
The patent introduces temperature sensors as intermediary indicators to predict potential on-wrist states. Instead of directly and continuously using power-intensive optical sensors for detection, the system first uses low-power temperature sensors to identify conditions where on-wrist state is likely, then triggers optical sensor sampling only in those scenarios. This intermediary approach significantly reduces power consumption while maintaining detection accuracy.
2Measurement precision
If optical sensors are exclusively used to detect on-wrist or off-wrist state, then detection can be performed, but false positive errors occur under certain conditions
Solution Approach 1:
The patent merges multiple sensing modalities (optical sensors and temperature sensors) into a unified detection system. Instead of relying exclusively on optical sensors which are susceptible to false positives from dielectric surfaces, the system combines optical detection with temperature-based detection. The temperature sensor provides an additional verification layer that can distinguish between actual skin contact and false positive conditions, thereby improving reliability while maintaining detection capability.
3Use of energy by moving object
If temperature sensors are used to determine on-wrist state by measuring temperature differences, then power consumption is reduced, but detection accuracy may be affected under isothermal conditions
Solution Approach 1:
The patent implements a dynamic detection strategy where the system adapts its sensing approach based on environmental conditions. When temperature sensors indicate isothermal conditions (ambient temperature equals wrist temperature), the system dynamically switches to or augments with optical sensor verification. This dynamic adaptation ensures detection accuracy is maintained during isothermal conditions while still benefiting from the low power consumption of temperature-based detection during non-isothermal conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces power consumption and minimizes false positives by leveraging temperature sensors to determine the wear state, while maintaining accuracy through opportunistic use of optical sensors, thereby optimizing device operation and extending battery life.
Implementation Method 1
a first temperature sensor disposed at a first surface of the electronic device that is in contact with skin of the user when the electronic device is worn by the user, and the first temperature sensor is configured to measure a first temperature at the first surface
Implementation Method 2
A difference between the first temperature corresponding to the first temperature sensor and the second temperature corresponding to the second temperature sensor indicates on-wrist
Data Source
AI summary
Temperature sensors and/or optical sensors can be used to determine whether an electronic device is worn or not worn by a user of the electronic device (e.g., on-wrist or off-wrist). In some examples, the temperature sensors can serve as a complement or a replacement to optical sensors when determining on-wrist or off-wrist. In some examples, detecting, via temperature sensors, a temperature difference between opposite sides of the wearable device (e.g., front face and back face) indicates on-wrist.