Polyimide FSR for Handheld Controller Miniaturization
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Solution Overview
Problem
Existing hand-held video game controllers with force sensing resistors (FSRs) exhibit crude response curves and are difficult to miniaturize due to materials used, limiting their suitability for virtual reality applications, where precise and natural interaction is required.
Innovation Solution
A FSR constructed with a polyimide substrate and interdigitated metal fingers, allowing for direct soldering and high-temperature manufacturing, providing a more precise and repeatable Force vs. Resistance response curve, enabling improved user interaction in VR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mylar-based FSR is used, then the FSR can be constructed with flexible materials, but the FSR consumes large footprint and is difficult to miniaturize
Solution Approach 1:
The patent uses a flexible printed circuit board (FPC) as the substrate for the FSR, replacing traditional mylar construction. The FPC maintains flexibility while enabling direct soldering and compact integration, thus reducing footprint while preserving the flexible material characteristics needed for FSR operation
Solution Approach 2:
The patent replaces the mechanical mylar-based construction with an FPC-based system that allows direct electrical connection through soldering. This substitution eliminates the need for large header connectors, enabling miniaturization while maintaining the mechanical flexibility required for force sensing
2Adaptability or versatility
If mylar-based FSR is used, then the FSR can be constructed with flexible materials, but it cannot tolerate high temperatures of reflow oven
Solution Approach 1:
The patent employs a flexible printed circuit board (FPC) substrate that combines the flexibility of thin film materials with the high-temperature tolerance required for reflow soldering processes. The FPC can withstand reflow oven temperatures while maintaining its flexible characteristics for FSR operation
Solution Approach 2:
The patent creates a composite structure using FPC substrate combined with force sensing elements. This composite material approach allows the FSR to achieve both flexibility from the FPC material and high-temperature tolerance through the engineered composite structure, enabling survival in reflow soldering processes
3Stability of the object's composition
If PCB substrate is used for FSR, then the FSR can be constructed with rigid structure, but the response curve is crude and non-monotonic
Solution Approach 1:
The patent uses a flexible printed circuit board (FPC) substrate instead of rigid PCB, allowing the FSR to maintain structural stability while achieving smooth, monotonic response curves. The FPC's flexible nature enables better force distribution and more accurate force-to-resistance conversion compared to rigid PCB substrates
4Adaptability or versatility
If mylar-based FSR with header connector is used, then the FSR can be constructed with flexible materials, but manufacturing costs cannot be reduced
Solution Approach 1:
The patent replaces the mechanical header connector system with direct soldering connections on the FPC substrate. This substitution eliminates the need for separate connector components and assembly steps, enabling more cost-effective manufacturing while maintaining flexibility through the FPC construction
Solution Approach 2:
The patent merges the FSR sensing element directly with the FPC substrate, eliminating the need for separate header connectors and reducing component count. This integration combines multiple functions into a single unified structure, reducing manufacturing complexity and cost while preserving flexible material characteristics
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
The polyimide-based FSR offers a smaller footprint, reduced manufacturing costs, and enhanced repeatability, enabling more natural and precise user interactions in VR systems by translating varying forces into analog inputs, reducing user fatigue and accidental actuations.
Implementation Method 1
the force sensing resistor (FSR), which uses variable resistance to measure an amount of force applied to the FSR
Data Source
AI summary
Logic of a handheld controller can implement sensor fusion algorithms based on force data provided by a force sensing resistor (FSR) in combination with touch sensor data provided by a touch sensor. An example sensor fusion algorithm can be used to pause calibration adjustments for the touch sensor—at least with respect to a high-level value that corresponds to a touch of a control—in response to a user pressing upon the control of the handheld controller with an above-threshold amount of force, which may be detected by a FSR associated with the control. For instance, calibration adjustments with respect to the high-level value can be paused in response to FSR values crossing a threshold value from below the threshold value to above the threshold value, and the calibration adjustments can be resumed in response to the FSR values crossing the threshold value in the opposite direction.