Keyboard Key Displacement Sensing With Frequency-Response Coil Filter
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Solution Overview
Problem
Existing techniques for detecting key displacement in musical keyboard instruments face challenges in accurately generating detection signals for slight key movements due to limited changes in current flow through the coil.
Innovation Solution
An instrument playing apparatus featuring a movable member with a magnetic or conductive detection part and a filter coil that generates a detection signal from a reference signal, with a frequency response that changes based on the distance between the detection part and the coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a coil and metal plate configuration is used to detect key displacement, then the structure is simple and easy to manufacture, but the current change through the coil is insufficient to accurately represent slight key displacements
Solution Approach 1:
The patent changes the electrical parameters of the detection circuit by introducing a filter with specific capacitance and resistance values. The filter modifies the frequency response of the coil circuit, transforming the insufficient current changes into detectable voltage signal variations that accurately represent slight key displacements.
Solution Approach 2:
The filter circuit acts as an intermediary between the coil and the detection system. It mediates the weak current signals from the coil by converting them into more detectable voltage signals through RC filtering, thereby enhancing the measurement capability without requiring direct modification of the coil structure.
2Measurement precision
If the distance between the detection part and coil is reduced to improve sensitivity, then slight displacements become more detectable, but the risk of mechanical interference and manufacturing precision requirements increase
Solution Approach 1:
The patent replaces the reliance on precise mechanical positioning with an electrical solution. Instead of requiring tight mechanical tolerances for the distance between the detection part and coil, the system uses filter circuit parameters (capacitance and resistance) to achieve the desired detection sensitivity, thereby substituting mechanical precision requirements with electrical parameter adjustments.
3Measurement precision
If the coil sensitivity is increased to detect slight key movements, then measurement precision improves, but the device becomes more susceptible to noise and external interference
Solution Approach 1:
The patent introduces dynamic filtering characteristics to the detection circuit. The RC filter creates a frequency-dependent response that dynamically adapts to the signal characteristics, allowing the system to enhance weak displacement signals while attenuating high-frequency noise and external interference through the time constant formed by the capacitor and resistor.
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 configuration allows for the generation of detection signals that accurately represent slight displacements of the movable member, enhancing the precision of key position detection.
Implementation Method 1
a filter that includes a coil and is configured to generate a detection signal from a reference signal, the filter having a frequency response that changes depending on a distance between the detection part and the coil
Data Source
AI summary
An instrument playing apparatus has: a movable member configured to be displaced responsive to a playing operation of a user; a detection part formed from a magnetic or conductive body and disposed on the movable member; and a filter that includes a coil. The filter has a frequency response that changes depending on a distance between the detection part and the coil, and generates a detection signal from a reference signal.