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To effectively harvest vibration energy from pavement without affecting driving comfort and safety, parameter optimization was done with the orthogonal experiment design and the finite element analysis. L
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^{4}) Taguchi’s orthogonal experiments were carried out with planted depth, PZT material, PZT diameter and thickness as optimization parameters and with open voltage and pavement displacement as optimization objectives. The experiment results were obtained via the finite element method. By using range analysis method, the dominance degree of the influencing factors and the optimum condition was obtained for the two objectives, respectively. Further, the multi-objective optimization was performed based on a weight grade method. The combined optimum conditions in order of their dominance degree are PZT diameter 35 mm, PZT thickness 6 mm, planted depth 50 mm and material PZT4. The validity of optimization scheme was confirmed.

Piezoelectric harvesting energy from pavement is a new process of capturing the wasted pavement vibration and transferring it into electricity to store it for later use or to power electronic sensors [

It has been well known that Taguchi’s approach is an efficient way to correlate various factors for parameter optimization and to identify the most influencing factors based on the experimental design and analysis method with good consistency and reproducibility. To our knowledge, the studies on the application of Taguchi experimental design for the purpose of high efficiency of piezoelectric harvesting energy are few [

In this paper, the optimization of piezoelectric harvesting device from pavement was studied based on Taguchi experimental design for high efficiency of harvesting energy and good coupling with pavement. The parameters, including embedded depth, thickness and diameter of PZT disk, and material type of PZT disk, were involved. Firstly, the influence of factors on piezoelectric harvesting device from pavement was investigated. Then, the orthogonal experiments were carried out and analyzed with the output voltage and relative displacement ratio as optimization objectives. Dominance degree of the factors and the optimum conditions for piezoelectric harvesting energy from pavement were studied.

The efficiency of a harvester is always represented by the electromechanical coupling factor k and the energy transmission coefficient

The output voltage of PZT disk under the applied stress can be obtained from the following equation in [

where,

Meanwhile, the good coupling with pavement reflects that there is no much change of pavement displacement with or without the harvester under pavement while a vehicle passes through. Here, the relative deformation ratio p is adopted to express the coupling property.

where, d_{0} and d_{w} represent the pavement displacements without and with the harvester under the pavement, respectively.

If the relative deformation ratio p is less, it indicates that the harvester has good coupling with pavement. The pavement displacement d_{0} and d_{w} can be obtained according to the maximum displacement value of the pavement via FEM. Therefore, the output voltage

Parameters, which affect the harvesting energy efficiency and coupling with pavement, deal with three types. One is related to the harvester’s ceramic material, another relates to the harvester structure and the other is the embedded depth under pavement. If the cylindrical harvester is adopted in the harvester-pavement piezoelectric system, the structural parameters of the harvester include the diameter and thickness of PZT disk．Therefore, the detailed parameters including the embedded depth of the harvester under pavement, PZT material, the diameter and thickness of PZT disk, are chosen to optimize.

According to the Taguchi parameter design methodology, a

The results of open voltage_{w} and d_{0} are obtained via FEM, the relative deformation ratio p is then calculated according to Equation (3). All are shown in _{w} and relative deformation ratio p vary in a range of 53.593 - 140.638 V 0.0648 - 0.0663 mm, and 3.68% - 6.08%, respectively. The open voltage _{0 }without the harvester is d_{0} = 0.0625 mm through the finite element analysis.

The orthogonal experiment was analyzed by range analysis method for

In _{i} is the average value of the objective variable, where i denotes the level of the certain factor. R is the range calculated as the difference between the maximum and the minimum values of k_{i} for a certain factor. According to the value of R, the dominance degree of each factor can be determined.

Experiments were run according to the chosen optimum conditions. The optimized values are shown in

Run | Factors | Results | |||||
---|---|---|---|---|---|---|---|

1(Planted depth h/mm) | 2(PZT materials) | 3(PZT thickness/mm) | 4(PZT diameter/mm) | Open voltage U_{3}/V | Pavement displacement d_{w}/mm | Relative deformation ratio p | |

1 | 1(20) | 1(PZT4) | 1(2) | 1(20) | 53.593 | 0.0663 | 6.08 |

2 | 1(20) | 2(PZT5A) | 2(4) | 2(25) | 87.267 | 0.0655 | 4.80 |

3 | 1(20) | 3(PZT5H) | 3(5) | 3(30) | 62.627 | 0.0654 | 4.64 |

4 | 1(20) | 4(PZT8) | 4(6) | 4(35) | 98.81 | 0.0648 | 3.68 |

5 | 2(30) | 1(PZT4) | 2(4) | 3(30) | 134.121 | 0.0654 | 4.64 |

6 | 2(30) | 2(PZT5A) | 1(2) | 4(35) | 86.819 | 0.0660 | 5.60 |

7 | 2(30) | 3(PZT5H) | 4(6) | 1(20) | 78.95 | 0.0651 | 4.16 |

8 | 2(30) | 4(PZT8) | 3(5) | 2(25) | 86.676 | 0.0654 | 4.64 |

9 | 3(40) | 1(PZT4) | 3(5) | 4(35) | 133.342 | 0.0651 | 4.16 |

10 | 3(40) | 2(PZT5A) | 4(6) | 3(30) | 139.898 | 0.0649 | 3.84 |

11 | 3(40) | 3(PZT5H) | 1(2) | 2(25) | 57.358 | 0.0662 | 5.92 |

12 | 3(40) | 4(PZT8) | 2(4) | 1(20) | 79.207 | 0.0660 | 5.60 |

13 | 4(50) | 1(PZT4) | 4(6) | 2(25) | 126.082 | 0.0650 | 4.00 |

14 | 4(50) | 2(PZT5A) | 3(5) | 1(20) | 120.888 | 0.0658 | 5.28 |

15 | 4(50) | 3(PZT5H) | 2(4) | 4(35) | 140.638 | 0.0656 | 4.96 |

16 | 4(50) | 4(PZT8) | 1(2) | 3(30) | 103.561 | 0.0662 | 5.92 |

Optimization objective | Analysis type | Planted depth/mm | PZT materials | PZT thickness/mm | PZT diameter/mm |
---|---|---|---|---|---|

Open voltage U_{3}/V | k_{1} | 75.574 | 111.785 | 75.333 | 83.160 |

k_{2} | 96.642 | 108.718 | 110.308 | 89.346 | |

k_{3} | 102.4512 | 84.893 | 100.883 | 110.052 | |

k_{4} | 122.7922 | 92.064 | 110.935 | 114.902 | |

R | 47.218 | 26.891 | 35.602 | 31.742 | |

Relative deformation ratio p | k_{1} | 4.8 | 4.72 | 5.88 | 5.28 |

k_{2} | 4.76 | 4.88 | 5.00 | 4.84 | |

k_{3} | 4.88 | 4.92 | 4.68 | 4.76 | |

k_{4} | 5.04 | 4.96 | 3.92 | 4.60 | |

R | 0.28 | 0.24 | 1.96 | 0.68 |

Optimization objective | Optimization conditions (in order of dominance degree) |
---|---|

Open voltage U_{3}/V | Planted depth 50 mm, PZT thickness 6 mm, PZT diameter 35 mm, PZT material PZT4 |

Relative deformation ratio p | PZT thickness 6 mm, PZT diameter 35 mm, planted depth 20 mm, PZT material PZT4 |

pared to the several highest values of the orthogonal experimental results in

Considering the practical application of harvester-pavement piezoelectric system,

where _{3} is the same as important as p for the application of the harvester-pavement piezoelectric system, both

The following discussion is on the multi-objectives optimization.

In the optimum conditions, the open voltage

Analysis type | Planted depth/mm | PZT materials | PZT thickness/mm | PZT diameter/mm |
---|---|---|---|---|

k_{1} | 74.789 | 101.852 | 56.855 | 72.288 |

k_{2} | 90.427 | 97.040 | 96.197 | 56.209 |

k_{3} | 92.584 | 79.442 | 94.759 | 99.962 |

k_{4} | 104.416 | 83.882 | 114.406 | 106.043 |

R | 29.627 | 22.410 | 57.552 | 49.834 |

tion ratio also increases with the planted depth except of 30 mm. It shows that the output voltage benefits from the bigger of the planted depth.

The effect of different PZT materials on open voltage and relative deformation ratio is shown in

In order to save manpower, material and financial resources, the finite element method was used in the paper to

perform the electromechanical analysis.

The mesh of Plane 42, which is suitable for elastic material properties, is used for asphalt pavement and end cap. Mean while, Plane 13 is adopted to mesh the piezoelectric material. The material properties can be found in [

To optimize the harvester parameters and the embedded position in piezoelectric harvesting from pavement vi-

bration,

planted depth, PZT material, PZT thickness and diameter as optimization parameters. The finite element method was adopted to do experiment. It is demonstrated that the open voltage varies in wide range and the relative deformation ratio has less change under the conditions in orthogonal experiment design. Range analysis results show that the planted depth is the most important factor for open voltage while it is not so important for relative deformation ratio. The PZT diameter and thickness are the key important factors for all the two optimization objectives. Different PZT materials have fewer influences on two objectives. By using the weight grade method, the optimum conditions obtained from the two-objectives optimization are PZT thickness 6 mm, PZT diameter 35 mm, planted depth 50 mm and PZT4 material, which are in order of their dominance degrees. The validity of the optimum conditions is confirmed and is of practical value for the application of piezoelectric energy harvesting technology in pavement.

This research was supported by the National Natural Science Foundation of China (No. 51175359) and the 4th “333 Engineering” Research Funding Project of Jiangsu Province (BRA2014086).

ChunhuaSun,HongbingWang,GuangqingShang,JianhongDu, (2015) Parameters Optimization for Piezoelectric Harvesting Energy from Pavement Based on Taguchi’s Orthogonal Experiment Design. World Journal of Engineering and Technology,03,149-157. doi: 10.4236/wjet.2015.34016