Force-Sensing Crown Structure for Multi-Axis Wearable Input
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Solution Overview
Problem
Small form factor devices, such as watches and wearable electronics, often have limited input mechanisms that cannot accurately detect non-binary forces applied by users, limiting the variety and precision of user inputs.
Innovation Solution
An input mechanism, such as a crown or button, equipped with force sensors, including capacitive sensors and strain gauges, that measure changes in capacitance or strain to determine the amount and direction of applied force, allowing for various types of user inputs through rotation, translation, and transverse movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional input mechanisms are used in small form factor devices, then the device maintains a compact size, but the input capability is limited to binary states only
Solution Approach 1:
The patent replaces traditional mechanical input mechanisms with capacitive sensing technology. The capacitive sensor detects changes in capacitance caused by different input actions (rotation, translation, transverse movement), enabling non-binary force detection without complex mechanical components. This substitution allows the device to maintain compact size while significantly enhancing input versatility.
Solution Approach 2:
The patent utilizes changes in capacitance as a parameter to detect different input forces and movements. By measuring capacitance variations caused by user interactions, the system can distinguish between different input types (rotation direction, translation distance, transverse movement) and interpret them as distinct non-binary inputs, thereby expanding input capability without increasing device complexity.
2Measurement precision
If force sensors are added to detect non-binary forces, then input precision is improved, but device complexity increases
Solution Approach 1:
The capacitive sensor serves multiple functions: it detects rotation, translation, transverse movement, and applies force detection all through a single sensing mechanism. This multi-functionality allows the system to achieve high measurement precision for various input types without proportionally increasing device complexity, as one sensor component handles multiple detection tasks.
Solution Approach 2:
The patent introduces a processing unit that acts as an intermediary between the capacitive sensor and the input interpretation system. This processing unit analyzes capacitance changes and translates them into meaningful input commands, simplifying the overall system architecture while maintaining high measurement precision. The intermediary processing layer enables complex force detection without requiring equally complex sensor hardware.
3Adaptability or versatility
If the input structure moves transversely, then input versatility is improved, but the capacitance between conductors changes causing detection errors
Solution Approach 1:
The patent separates the force detection function from the capacitance-based input detection. The force sensor independently measures applied force while the capacitive sensor detects movement types (rotation, translation, transverse movement). By extracting force detection as a separate function, the system can accommodate transverse movements without capacitance interference, as force measurement is no longer dependent on conductor capacitance stability.
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
Enables precise detection of non-binary forces, enabling a range of user inputs and improving the functionality of small form factor devices by interpreting different force amounts as distinct inputs.
Implementation Method 1
The collar includes a moveable conductor, a conductive element, and a separation defined between the moveable conductor and the conductive element. Movement of the input structure changes a capacitance between the moveable conductor and the conductive element.
Implementation Method 2
In various examples, the sensor is a strain gauge.
Data Source
AI summary
An input mechanism, such as a crown, detects amounts of applied force. In various examples, an assembly including an input mechanism has an enclosure; a stem coupled to the enclosure such that the stem is rotatable, translatable, and transversely moveable with respect to the enclosure; a sensor, coupled between the stem and the housing, to which force is transferred when the stem moves with respect to the housing; and a processing unit coupled to the sensor. The processing unit is operable to determine a measurement of the force, based on a signal from the sensor.