Force Sensor Compliant Member Displacement Detection
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Solution Overview
Problem
Traditional force sensors using strain gauges in metal beams are limited by non-symmetries, manufacturing tolerances, and off-axis deformations, which affect the accuracy and precision of force measurements, thereby restricting their functionality in controlling electronic devices.
Innovation Solution
The development of an input device with a force sensor that includes a compliant member and a sensor to detect displacement, allowing the estimation of force input based on movement, using a processing unit to determine the force from the displacement and characteristics of the compliant member, which can be a set of O-rings or a deformable structure, to control the movement of the input structure relative to the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used in metal beams to measure force, then the sensor can detect force input, but non-symmetries in the metal beam, manufacturing tolerances, and off-axis deformations affect measurement accuracy and precision
Solution Approach 1:
The patent replaces the traditional strain gauge mechanical measurement system with a magnetic field-based sensing system. A magnet is attached to the input structure, and a magnetic sensor (such as a Hall effect sensor or fluxgate magnetometer) measures the magnetic field changes caused by displacement of the input structure. This substitution eliminates the need for strain gauges and metal beams, thereby avoiding issues related to manufacturing tolerances, non-symmetries, and off-axis deformations that plague mechanical strain measurement systems.
Solution Approach 2:
The patent introduces a compliant member as an intermediary element between the input structure and the measurement system. This compliant member (such as an elastic beam or flexible support) translates force input into controlled displacement of the magnet, which is then measured by the magnetic sensor. The compliant member provides a predictable, repeatable mechanical response that is less sensitive to manufacturing variations, improving measurement consistency while maintaining the ability to detect force input.
2Adaptability or versatility
If traditional force sensors are used, then force detection is possible, but the functionality to control electronic devices is limited due to accuracy and precision restrictions
Solution Approach 1:
By replacing the traditional strain gauge system with a magnetic field-based sensing system, the patent achieves higher measurement precision and accuracy. This improved precision enables more sophisticated control functionality in electronic devices, such as pressure-sensitive keyboards, force-feedback joysticks, and precision input devices that can detect subtle differences in applied force.
Solution Approach 2:
The magnetic sensing system provides multiple measurement capabilities beyond simple force detection. The system can measure displacement, velocity, and acceleration of the input structure by analyzing temporal changes in the magnetic field. This multi-functionality enhances the adaptability of the device for various control applications, including touch interfaces, gesture recognition, and haptic feedback systems.
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 solution enhances the accuracy and precision of force measurement by correlating displacement with force input, enabling more precise control of electronic devices and providing a more reliable means of detecting force characteristics such as magnitude, duration, and direction.
Implementation Method 1
a compliant member encircling the input structure within the housing and configured to deform in response to the force input, thereby controlling a movement of the input structure relative to the housing
Implementation Method 2
a sensor positioned within the housing and configured to detect a value of a displacement of the input structure caused by the force input
Data Source
AI summary
Embodiments are directed to a force sensor used within an electronic device, such as a stylus, watch, laptop, or other electronic device. A force sensor may be positioned, for example, within a stylus body. The force sensor may include an input structure constrained within a housing by a compliant member. The input structure may extend at least partially out of the stylus body and be configured to receive a force input. One or more sensors of the force sensor may detect a value of a displacement of the input structure caused by the force input. A processing unit may determine a value of the force input using a spring characteristic of the compliant member and the detected value of displacement.