Application Cases

Experiment Name: Rotational Energy Harvesting for Pipeline Inspection Smart Spheres

Research Direction: Pipeline Inspection

Experimental Objectives:
Based on the analysis of the motion characteristics of pipeline inspection smart spheres, a rotational piezoelectric energy harvesting structure suitable for smart spheres is proposed. An electromechanical coupling model is established to analyze the response characteristics of the energy harvester, and key technical points for designing a self-powered energy harvester for smart spheres are identified.

Testing Equipment:
ATA-3080 power amplifier, signal generator, electromagnetic vibration exciter, acceleration sensor, oscilloscope, etc.

Figure: Single-Axis Vibration Test Platform

Experimental Procedure:
The rotational experimental platform is shown in the figure below. Rotational motion is generated by a motor, and a controller is used to adjust the speed. The motor is connected to an acrylic rotating disk via a shaft. The output of the piezoelectric energy harvester is connected to an oscilloscope or data acquisition card through a slip ring.

Figure: Schematic Diagram of the Rotational Experimental Platform

In the experiment, the piezoelectric energy harvester consists of a commercial piezoelectric fiber composite material and 6061T aluminum alloy. The piezoelectric material measures $101\times 20\times 0.21\text{mm}$, the cantilever beam measures $101\times 20\times 0.33\text{mm}$, the mass block weighs $10\text{g}$, and the load resistance is $1\text{M}\Omega$. The piezoelectric material is bonded to the cantilever beam substrate using an epoxy resin adhesive, and the electrodes of the MFC are directly connected to the two ends of the load resistor. The steady-state time-domain responses of the energy harvester under vibration and rotational excitation are shown in the figure below, with 1-second data selected at resonance frequencies of $12.3\text{Hz}$ and $8.7\text{Hz}$, respectively.

Figure: Time-Domain Response of the Energy Harvester Under Vibration and Rotational Excitation

Experimental Results:
Both vibration and rotational energy harvester responses exhibit approximately sinusoidal characteristics. However, due to the weight of the base, the rotational energy harvester shows some rotational non-uniformity. The steady-state output voltage RMS values under different frequency excitations are shown in the figure below.

Figure: Frequency Response Statistics of the Energy Harvester Under Vibration and Rotational Excitation

Under vibration and rotational excitation conditions, energy harvesters with the same parameters reached resonance states at $12.3\text{Hz}$ and $8.7\text{Hz}$, respectively. In simulations, peaks were observed at $12.29\text{Hz}$ and $8.70\text{Hz}$, respectively. The resonance frequency of the rotational energy harvester is lower, while the resonance frequency of the vibration energy harvester is approximately $\sqrt{2}$ times that of the rotational energy harvester.

The peak voltages of the rotational and vibration energy harvesters are $35.04\text{V}$ and $25.64\text{V}$, respectively, corresponding to peak powers of $1.23\text{mW}$ and $0.66\text{mW}$. In simulations, the peak voltages are $37.89\text{V}$ and $27.27\text{V}$, respectively, with ratios of approximately $1.367$ (experimental) and $1.389$ (simulation). Since the experiment was not conducted under ideal open-circuit conditions, the amplitude of the vibration energy harvester did not reach $\sqrt{2}$ times that of the rotational energy harvester. However, the rotational energy harvester has a narrower bandwidth. The $6\text{dB}$ bandwidth (where power drops to $25\%$ and voltage drops to $50\%$) of the vibration energy harvester is $1.2\text{Hz}$, while that of the rotational energy harvester is $0.6\text{Hz}$, halved. Achieving broadband performance for the rotational energy harvester is more challenging.

Aigtek ATA-3080C Power Amplifier:

Figure: Specifications of the ATA-3080C Power Amplifier