Polyimide FSR for Handheld Controller Sensor Fusion
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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 interactions are required.
Innovation Solution
A FSR constructed with a polyimide substrate and a resistive substrate with conductive interdigitated metal fingers, allowing for direct soldering and higher temperature resistance, enabling a more precise and analog input response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If mylar-based FSR is used, then the FSR can be constructed with flexible materials, but the FSR requires a large header connector that increases footprint and prevents miniaturization
Solution Approach 1:
The patent changes the substrate material parameter from mylar to polyimide, which enables direct soldering without requiring a large header connector. This material parameter change allows the FSR to be miniaturized while maintaining flexible construction and improved response characteristics suitable for VR applications.
Solution Approach 2:
The patent replaces the mechanical header connector system with direct soldering capability. By using polyimide substrate instead of mylar, the FSR eliminates the need for a bulky header connector, enabling direct integration onto circuit boards and significantly reducing the overall footprint.
2Object-affected harmful factors
If mylar-based FSR is used, then the FSR can be constructed with flexible materials, but the FSR cannot tolerate high temperatures of reflow oven
Solution Approach 1:
The patent changes the substrate material parameter from mylar to polyimide, which has superior thermal stability. Polyimide can withstand the high temperatures of reflow oven processing, enabling the FSR to be manufactured using standard PCB assembly processes without degrading the flexible construction or response characteristics.
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 becomes crude and non-monotonic
Solution Approach 1:
The patent uses a composite structure combining polyimide substrate with conductive material layers. This composite material approach provides both the structural stability needed for manufacturing and the precise, monotonic response characteristics required for accurate force sensing in VR applications, avoiding the crude response curves associated with standard PCB substrates.
4Device complexity
If existing FSR materials are used, then the FSR can be constructed simply, but the response curve is crude and suitable only for binary switching
Solution Approach 1:
The patent changes the material composition parameters to use polyimide substrate with specific conductive material layers. This material parameter optimization enables the FSR to provide precise, analog response curves suitable for VR applications while maintaining relatively simple construction methods, avoiding the need for complex multi-layer structures.
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 provides improved sensitivity, reduced hysteresis, and higher repeatability, enabling more natural and precise interactions in VR systems by translating varying forces into digitized values, 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
Implementation Method 2
A FSR constructed with a polyimide substrate and a resistive substrate with conductive interdigitated metal fingers, allowing for direct soldering and higher temperature resistance, enabling a more precise and analog input response
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 data or proximity data provided by a touch sensor or an array of proximity sensors, respectively. An example sensor fusion algorithm can be used to re-calibrate the FSR when an object contacts an associated control, as detected by the touch sensor. Another example sensor fusion algorithm can be used to ignore spurious inputs detected by the FSR when an object is in contact with an adjacent control. Another example sensor fusion algorithm can be used to detect a hand size of a hand grasping a handle of the controller, as detected by the array of proximity sensors, and to adjust the threshold force to register a FSR input event at the FSR according to the hand size.