Electromagnetic Actuator Displacement Detection Using Synchronous Sampling
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Solution Overview
Problem
Existing displacement detection methods for electromagnetic actuators driven by pulse width modulation signals are complex and require additional components like sine-wave oscillators and oscillation circuits, making them difficult to implement in compact systems with limited installation space, such as electronic keyboard instruments.
Innovation Solution
A simplified displacement detection apparatus for electromagnetic actuators using a detection coil with a sampling-signal generating portion and a synchronous sampling portion to output a displacement detection signal, which includes a main detection coil and an auxiliary detection coil connected in anti-series to cancel noise and ringing, allowing for accurate displacement detection without the need for oscillation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a differential transformer is used for displacement detection, then displacement position can be detected, but the installation space requirement increases and the structure becomes complex
Solution Approach 1:
The patent combines the displacement detection function with the existing electromagnetic actuator structure by using the drive coil as both a drive component and a detection component. The detection coil is integrated into the actuator assembly, eliminating the need for separate differential transformer components and reducing overall device complexity while maintaining detection precision.
Solution Approach 2:
The drive coil serves dual purposes: it generates electromagnetic force for actuator operation and simultaneously functions as a detection coil for displacement measurement. This multi-functionality reduces the number of components needed and simplifies the overall system structure while achieving accurate displacement detection.
2Measurement precision
If a differential transformer is used for displacement detection, then displacement position can be detected, but the installation space increases
Solution Approach 1:
The detection function is merged into the existing actuator structure, utilizing the same space occupied by the drive coil. The detection coil is positioned within the actuator assembly, eliminating the need for additional space that would be required for a separate differential transformer and its associated oscillation circuits.
Solution Approach 2:
The patent extracts the detection function from separate external components (differential transformer and oscillation circuits) and integrates it directly into the electromagnetic actuator structure. This extraction and integration approach significantly reduces the installation space requirement while maintaining detection capability.
3Ease of operation
If strain gauge or optical sensor is used for position detection, then key touch feeling can be controlled, but the cost increases
Solution Approach 1:
The drive coil is made to serve dual purposes: generating electromagnetic force for actuator operation and functioning as a detection coil for position sensing. This eliminates the need for separate expensive sensors like strain gauges or optical sensors, thereby reducing manufacturing costs while maintaining the ability to control key touch feeling.
Solution Approach 2:
The electromagnetic actuator system performs its own displacement detection using the drive coil as the detection element, eliminating the need for external sensing components. This self-service approach reduces system complexity and manufacturing costs while achieving the required control functionality.
4Measurement precision
If displacement detection coil with oscillation circuit is used, then displacement can be detected through self inductance change, but the device complexity and cost increase
Solution Approach 1:
The drive coil serves as both the actuation coil and the detection coil. By utilizing the existing drive coil for detection purposes, the patent eliminates the need for separate displacement detection coils and their associated oscillation circuits, thereby reducing circuit complexity and component costs while maintaining accurate displacement detection capability.
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 solution provides a compact and cost-effective displacement detection system that is not influenced by the duty ratio of the pulse width modulation signal, ensuring accurate and proportional displacement detection, thereby enhancing design freedom and reducing component costs.
Implementation Method 1
a detection coil which is disposed at a position where a mutual coupling coefficient with the drive coil changes in accordance with the displacement of the movable core
Data Source
AI summary
A displacement detecting apparatus of an electromagnetic actuator, including: an electromagnetic actuator including: a movable core; a drive coil which causes a displacement of the movable core; and a detection coil disposed at a position where a mutual coupling coefficient with the drive coil changes with the displacement, the actuator transmitting a drive force of the movable core to a mechanical system; a drive portion for supplying a drive current to the drive coil on the basis of a pulse width modulation signal; and a displacement detecting portion to which an output voltage of the detection coil is inputted, for outputting a displacement detection signal, wherein the displacement detecting portion includes: a sampling-signal generating portion for generating a sampling signal in synchronism with the pulse width modulation signal; and a synchronous sampling portion for outputting the displacement detection signal by sampling the output voltage in synchronism with the sampling signal.