Piezoelectric Resonator Energy Recovery With Injection-Locked Phase Control
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Solution Overview
Problem
Existing vibration energy recovery systems using piezoelectric generators face significant efficiency losses when the vibration frequency deviates from the resonance frequency, due to limitations in adjusting the resonant frequency dynamically and automatically controlling the phase shift between energy recovery instants and resonator oscillations.
Innovation Solution
A device comprising an electrical generator, a converter, and a frequency-to-phase conversion system using injection-locked oscillators (ILOs) to automatically adjust the phase shift and resonate frequency, ensuring optimal energy recovery across varying vibration frequencies with low power consumption and instantaneous adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a piezoelectric generator is designed to operate at a fixed resonance frequency, then energy recovery efficiency is maximized at that frequency, but efficiency drops significantly when vibration frequency deviates from resonance
Solution Approach 1:
The patent implements dynamic frequency tuning by applying control voltages to piezoelectric actuators that modify the stiffness of the resonator structure in real-time. This allows the resonance frequency to be dynamically adjusted to match varying vibration frequencies, maintaining high energy recovery efficiency across different operating conditions
Solution Approach 2:
The system changes the physical parameters of the resonator (specifically stiffness) by applying electrical voltages to piezoelectric materials. This parameter modification enables the resonance frequency to be tuned across a range of values, allowing the system to adapt to different vibration frequencies while maintaining optimal energy recovery
2Adaptability or versatility
If discrete capacitors and accelerometers are added to dynamically adjust resonance frequency, then frequency adaptability is improved, but device complexity and integration difficulty increase
Solution Approach 1:
The patent uses piezoelectric materials that serve dual functions: as sensors for detecting vibration characteristics and as actuators for adjusting the resonator stiffness. This multi-functionality eliminates the need for separate capacitors and accelerometers, reducing device complexity while maintaining frequency adaptability
Solution Approach 2:
The control voltage generation circuitry is integrated directly into the energy harvesting system, combining the frequency tuning function with the existing piezoelectric elements. This merging of functions reduces the number of discrete components needed and simplifies the overall system architecture
3Measurement precision
If accelerometer placement is used for control algorithm, then resonance frequency detection is achieved, but placement restrictions and system complexity increase
Solution Approach 1:
The piezoelectric elements inherently sense the vibration frequency through the piezoelectric effect, eliminating the need for separate accelerometers. The system uses its own operational signals for control, and the piezoelectric material's electrical response directly provides frequency information for the control algorithm
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 enables self-adjustment of the phase shift and resonance frequency, maximizing power transfer and maintaining efficiency even when the vibration frequency differs from the resonant frequency, thereby enhancing the energy recovery process.
Implementation Method 1
an electrical generator (104) including a conversion element (106) for converting mechanical vibration energy of the mechanical resonator (102) into electrical charges
Implementation Method 2
it is proposed to electrically adjust the resonant frequency of a piezoelectric generator using the indirect piezoelectric effect. Indeed, the voltage applied to the terminals of the piezoelectric material induces a mechanical force on the resonator
Data Source
AI summary
A device for recovering or dampening vibratory energy from a mechanical resonator, comprising:an electrical generator comprising an element for converting mechanical vibration energy into electrical charges coupled to the resonator, the electrical generator periodically transferring a portion of the electrical charges from one terminal of the conversion element to the other;a frequency variation to phase variation conversion device, comprising an injection-locked oscillator of which the free-running oscillation frequency is equal to the resonance frequency of the resonator, and supplying to the electrical generator a control signal of frequency equal to that of the signal outputted by the conversion element and of which the phase shift depends on the difference between the frequency of the signal outputted by the conversion element and the resonance frequency of the resonator.