Phased Electret Vibration Sensor Ripple Cancellation
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Solution Overview
Problem
Conventional vibration power-generating devices using electrets face challenges in conveniently detecting external vibrations due to the superimposition of ripple voltage on power generation voltage, making it difficult to directly understand vibration status from power output and requiring additional processing.
Innovation Solution
A vibration sensor design that includes a plurality of substrates with electrets and electrodes arranged in phases, generating electric signals with a predetermined phase difference to reduce the influence of ripple voltage, allowing for enhanced detection of external vibrations by superimposing signals with phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electret and electrodes are arranged in interdigital manner for power generation, then vibration energy conversion efficiency is improved, but ripple voltage is superimposed on output voltage making vibration detection inconvenient
Solution Approach 1:
The electrode array is divided into multiple phases (at least two phases), with each phase having electrodes arranged at different positions along the movement direction of the electret. This segmentation allows the output signals from different phases to be combined in a way that cancels out the ripple voltage components while preserving the fundamental vibration signal, thus resolving the contradiction between maintaining power generation efficiency and improving vibration detection convenience.
2Power
If electret traverses multiple electrode pairs for power generation, then power output is improved, but ripple voltage superimposition requires complex signal processing
Solution Approach 1:
The electrode array is segmented into multiple phases with specific spatial arrangements. By combining the output signals from these phased electrode groups, the system achieves ripple voltage cancellation through constructive and destructive interference of the signal components. This approach maintains high power output from the traversing electret while eliminating the need for complex post-processing to remove ripple effects.
Solution Approach 2:
The ripple voltage, which is normally a harmful distortion in the output signal, is converted into a beneficial effect through the phased electrode arrangement. The periodic ripple components from different phases are out of phase with each other and cancel out when combined, while the fundamental vibration signal reinforces. This transforms the harmful ripple superimposition into a useful signal processing mechanism that occurs naturally in the electrical domain.
3Power
If conventional vibration power-generating device structure is used, then power generation function is achieved, but additional processing devices are needed for vibration detection
Solution Approach 1:
The vibration sensor achieves dual functionality by using the same electret-electrode interaction mechanism for both power generation and vibration detection. The phased electrode arrangement enables the device to simultaneously generate power from ambient vibration while providing a clean detection signal that directly reflects the vibration characteristics. This eliminates the need for separate processing devices and makes the system universally applicable for both energy harvesting and sensing applications.
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 vibration sensor effectively reduces the impact of ripple voltage on the fundamental signal, improving the convenience of vibration detection by directly outputting a signal close to the external vibration, eliminating the need for complex signal processing.
Implementation Method 1
an electret group including a plurality of electrets that are arrayed in a relative movement direction on a side of one of surfaces of the first substrate
Implementation Method 2
a positional relationship between the electret group and the electrode group changes with a relative change in position of the first and second substrates by the external vibration to output an external vibration detection signal
Data Source
Figure 1
Figure 2A~2B
Figure 3~4A
AI summary
With the relative positional change between a first substrate and a second substrate due to an external vibration, the positional relationship between an electret group and an electrode group changes, as a result of which a vibration sensor outputs the detection signal of the external vibration. The electrode group is divided into two or more predetermined number of phases, and small electrode groups are formed that can generate electric signals in response to the external vibration on a per-phase basis. In the electrode group, a phase difference generation gap that generates predetermined phase differences between the respective electrical signals generated in the small electrode groups is provided between adjacent electrodes included in the electrode group, according to the predetermined number of phases. The vibration sensor outputs, as the detection signal of the external vibration, a signal formed by superimposing the electric signals generated in the small electrode groups as a result of the relative positional change between the first substrate and the second substrate due to the external vibration. This provides a highly simple and convenient vibration sensor for detecting an external vibration by use of electrets.