Keyboard Key Displacement Detection Using Magnetic Field Concentration
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Solution Overview
Problem
Existing techniques for detecting the displacement of a movable member, such as a key in a musical keyboard instrument, face difficulties in generating a magnetic field of sufficient strength, limiting the effective range of displacement that can change the detection signal level.
Innovation Solution
The implementation of a detection system with a first and second coil configuration, where the first coil is disposed on the movable member and the second coil on a supporting structure, utilizing magnetic fixing members to enhance the magnetic field strength and accurately detect the displacement of the key, and a signal processing circuit to generate a detection signal based on the distance between the coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an excitation coil and position detection coil are disposed on a fixed member with an excitable coil on the movable member, then a magnetic field is generated for detection, but the magnetic field strength is insufficient for practical displacement detection
Solution Approach 1:
A magnetic body is introduced as an intermediary element to concentrate and enhance the magnetic field between the excitation coil and excitable coil. The magnetic body is disposed on either the movable member or fixed member to create a stronger magnetic coupling, thereby improving detection signal level without requiring higher coil currents or more complex coil structures.
2Length of moving object
If the magnetic field strength is increased to improve detection signal, then the displacement detection range is improved, but the device complexity increases
Solution Approach 1:
Instead of complicating the coil configuration to increase magnetic field strength, a simple magnetic body is introduced as a mediator. This approach achieves enhanced magnetic field strength and extended detection range while maintaining the simplicity of the original coil arrangement, thus avoiding increased device complexity.
Solution Approach 2:
The magnetic properties of the system are changed by introducing a magnetic body with specific magnetic permeability. This parameter change enhances the magnetic field strength and extends the effective displacement detection range without requiring changes to the coil geometry or electrical parameters.
3Strength
If a magnetic body is disposed on the movable member or signal generator, then the magnetic field strength is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The magnetic body serves multiple functions: it enhances the magnetic field strength for detection and simultaneously acts as a structural component that can be integrated into either the movable member or fixed member assembly. This multi-functionality reduces the need for separate magnetic enhancement components, thereby simplifying manufacturing.
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 enhanced magnetic field strength allows for a wider range of displacement detection, ensuring accurate representation of the key position, thereby improving the detection signal's amplitude level and simplifying the configuration by using magnetic fixing members.
Implementation Method 1
supply of a cyclic signal causes generation of a magnetic field in the excitation coil, as a result of which a magnetic field in the excitable coil due to electromagnetic induction
Implementation Method 2
a magnetic body that is disposed on at least one of the movable member or the signal generator
Data Source
Figure 1~2
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Figure 6~8
AI summary
A detection system is used in a musical keyboard instrument that includes a key, the displacement of which changes in accordance with a playing operation. The detection system includes a detectable portion that is disposed on the key and includes a first coil; a signal generator that is configured to include a second coil that generates a magnetic field by receiving a supply of a current, and is configured to generate a detection signal with a level depending on a distance between the detectable portion and the second coil; and a magnetic body that is disposed on the key.