Electret-Based Vibrational Energy Harvester with Nonlinear Spring Modulation
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Solution Overview
Problem
Conventional vibrational energy harvester devices have poor utilization efficiency due to their narrow frequency response, as they are designed to resonate at a specific frequency, limiting the use of environmental vibrations to power generation, and reducing the Q factor to broaden frequency response decreases resonant sensitivity and increases energy loss.
Innovation Solution
A vibrational energy harvester device with a movable part and a fixed part having projections that form a comb-like structure, where an electret film with electrostatic potential is used to modulate the spring rate of the movable part as a function of position, allowing it to vibrate across a wide frequency band without significantly decreasing the Q factor, thereby enhancing energy harvesting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Q factor is reduced to broaden frequency response, then the frequency band is widened, but the resonant sensitivity decreases and energy loss increases
Solution Approach 1:
The patent applies non-linear spring elements whose stiffness characteristics change dynamically with displacement amplitude. This allows the system to maintain high Q factor at small amplitudes for sensitivity while broadening frequency response at larger amplitudes, resolving the contradiction between frequency band and energy loss
Solution Approach 2:
The patent changes the physical parameters of the spring elements by using materials or structures with non-linear elastic properties. This enables the spring rate to vary with operating conditions, allowing the system to adapt its frequency response characteristics without permanently reducing Q factor
2Adaptability or versatility
If the Q factor is reduced to broaden frequency response, then the frequency band is widened, but the resonant sensitivity decreases
Solution Approach 1:
The non-linear spring elements provide amplitude-dependent stiffness that maintains high resonant sensitivity at small vibration amplitudes while enabling broader frequency response at larger amplitudes, thus resolving the contradiction between sensitivity and frequency band
Solution Approach 2:
The patent utilizes periodic nonlinear forces generated by the non-linear spring elements during vibration cycles to create subharmonic and superharmonic resonances, which broaden the effective frequency response while maintaining peak sensitivity at the fundamental resonant frequency
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 device effectively converts a wide range of environmental vibrations into electricity with minimal energy loss, maintaining high sensitivity and efficiency across a broad frequency band.
Implementation Method 1
an electret film having an electret electric potential is formed on at least one of the first surface of the movable part and the second surface of the fixed part, and the movable part has a spring rate which is modulated according to a function of a positional parameter in the vibration direction through an electrostatic force acting between the movable part and the fixed part
Implementation Method 2
vibrational energy harvester device of electrostatic type with an electret to convert mechanical vibrational energy into electricity by electrostatic induction action
Data Source
AI summary
The present invention enables frequency response in a wide band without lowering the Q value. This vibrational energy harvester device is provided with: a movable part capable of vibration in a vibration direction as a result of mechanical vibrational energy applied from the exterior, said movable part being provided with a first surface along the vibration direction; and a fixed part provided with a second surface facing the first surface of the movable part with an interval therebetween, said fixed part being configured so as to be positionally fixed even against vibrational energy. A plurality of projections protruding in a direction orthogonal to the vibration direction are formed so as to be arranged like comb teeth in the vibration direction on each of the first surface of the movable part and the second surface of the fixed part. An electret film is formed on at least the first surface of the fixed part or on at least the second surface of the movable part. The vibrational energy harvester device is configured so that the spring rate of the movable part is modulated as a function of the position of the vibration direction by electrostatic force acting between the movable part and the fixed part.