Magnetic Sensor Proximity Sensing Using Modulated Fields
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Solution Overview
Problem
Current magnetic sensor-based proximity sensing technologies face challenges in accurately measuring the movement of individual finger and thumb bones due to interference from the Earth's static magnetic field and environmental noise, limiting their precision and reliability.
Innovation Solution
A magnetic sensor-based proximity sensing architecture that utilizes a modulated magnetic field generated by a differential voltage source pair, exciting an electromagnetic coil to create a modulated magnetic field, which is then demodulated by sensors to determine distance and direction, enabling precise tracking of finger and hand movements. This system includes multiple sensors aligned to detect magnetic field changes in different axes for three-dimensional positioning and incorporates additional components like electrodes for capacitive touch and force sensors for haptic feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a magnetic sensor-based proximity sensing system is used to detect finger and hand movements, then the ability to track movement is improved, but the measurement precision deteriorates due to interference from Earth's static magnetic field and environmental noise
Solution Approach 1:
The patent applies periodic action by modulating the magnetic field at a specific frequency (e.g., 100 Hz) using an electromagnetic coil. This allows the sensor to distinguish between the modulated signal and static environmental magnetic fields, thereby improving measurement precision while maintaining movement tracking capability. The modulated field creates a time-varying signal that can be demodulated to extract proximity information.
Solution Approach 2:
The patent converts the harmful static magnetic field interference into a beneficial signal by superimposing a modulated AC magnetic field on top of it. The sensor then detects the modulated component, effectively filtering out the DC Earth's magnetic field. This approach transforms the problematic static field environment into one where AC coupling naturally rejects the interference.
2Measurement precision
If multiple magnetic sensors are used to detect magnetic field changes in different axes for three-dimensional positioning, then the positioning capability is improved, but the device complexity increases
Solution Approach 1:
The patent employs a single electromagnetic coil that can generate magnetic field modulation in multiple directions by changing the current flow pattern. This multi-functional coil replaces what would otherwise require multiple separate coils or sensors, reducing device complexity while maintaining the capability to detect three-dimensional positioning through differential measurements.
Solution Approach 2:
The patent adds the time dimension by using modulated magnetic fields at different frequencies to encode spatial information. Instead of relying solely on spatial arrangement of multiple sensors, the system uses frequency modulation to distinguish between different spatial positions, effectively trading spatial complexity for temporal processing.
3Reliability
If a modulated magnetic field is used to avoid interference from Earth's static magnetic field, then the reliability of proximity sensing is improved, but the device complexity increases due to additional components
Solution Approach 1:
The patent combines the functions of the electromagnetic coil, modulation circuit, and magnetic field generator into a single integrated module. By merging these components, the system achieves reliable modulated magnetic field generation without proportionally increasing device complexity. The coil serves both as the magnetic field source and the modulation element when driven by an AC signal.
Solution Approach 2:
The magnetic sensor system uses its own electromagnetic coil to generate the modulated field, making the system self-contained. The same coil that would otherwise just be a passive component becomes an active field generator when driven by a modulation signal, eliminating the need for separate external field generation equipment and reducing overall system complexity.
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
Enables precise location and positioning of electronic devices and accurate tracking of finger and hand movements, providing improved stability against environmental interferences and long-term drift, while allowing for the computation of orientation, position, and angle of finger bones, enhancing user interaction and control.
Implementation Method 1
An electromagnetic coil (e.g., spiral, cylindrical, or circular) can get excited by the modulation current and generate a magnetic field B (T) that has the same modulation simulation
Implementation Method 2
The magnetic sensor receives the modulated magnetic field and performs demodulation. The distance d between the magnetic sensor and the electromagnetic coil can be determined based on magnetic field amplitude after demodulation
Data Source
AI summary
Magnetic sensing technology can be used to detect changes, or disturbances (e.g., changes in magnetic field strength), in magnetic fields and can be used to measure the precise location/positioning of an electronic device in proximity to a magnetic source. In order to avoid interference by earth's static magnetic field, a modulated magnetic field can be used for magnetic based proximity sensing. Received modulated magnetic field signals can be demodulated to determine proximity of the sensor to the source of the modulated magnetic field. Devices such as gloves or devices with fingertip nodes based on receiving modulated magnetic fields can be used to detect user hand position.