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A magnetorheological (MR) damper with energy harvesting ability was proposed based on electromagnetic induction (EMI) principle. The energy harvesting part was composed of a permanent magnet array and inducing coils which move vertically. This device could act as a linear power generator when the external excitation was applied, and the kinetic energy could be converted into electrical energy due to the relative linear motion between the magnets array and the inducing coils. Finite element models of both the MR damper part and the linear power generator part were built up separately to address the magnetic flux distributions, the magnetic flux densities, and the power generating efficiency using ANSYS software. The experimental tests were carried out to evaluate the damping performance and power generating efficiency. The results show that the proposed MR damper can produce approximately 750 N damping forces at the current of 0.6 A, and the energy harvesting device can generate about 1.0 V DC voltage at 0.06 m·s^{−1} excitation.

Over the past couple of decades, magnetorheological (MR) fluid has undergone significant development due to its unique rheological properties under exerted magnetic fields [

Till now, the MR dampers have wide applications in automotive industry including off-road vehicles [

Recently, energy harvesting MR dampers have received a great deal of attention due to their capability of recovering kinetic energy that normally dissipated by traditional MR dampers. Many researchers explored different principles and designs of energy harvesting MR dampers, which can be classified into two main categories. The first category is to convert the linear damper vibration into oscillatory rotation and use rotational permanent magnetic DC or AC generators to harvest kinetic energy. These mechanical mechanisms include rack and pinion, ball screw, and hydraulic transmission. Avadhany et al. [

In addition to the energy harvesting with mechanical transmission mechanism in the MR damper, the second category is based on the design of an electromagnetic induction (EMI) device, which generates power from the relative linear motion between magnets and coils. Cho et al. [

In this paper, a new MR damper with energy harvesting ability was proposed based on the EMI principle. The sharing component between the damper part and the linear power generator part could minimize the magnetic field interference without extra guild layer and shell layer; also the component itself provided necessary function in both generating process and damping capability. This new design is expected to simplify the structure of linear power generator and also provided a low cogging force. The inducing coils in the linear power generator had two representative electric circuits. In this study, finite element method was utilized to address the magnetic field distribution and magnetic flux density for the damper part and linear power generator part, respectively, and cogging force conducted from linear power generator was also identified. The properties of proposed MR damper were experimentally investigated, and power regenerative characteristics were also discussed.

Figure

Schematic diagram of the proposed MR damper with energy harvesting ability.

The linear power generator is radially arranged inside the MR damper. Each two permanent magnets are separated by a spacer; also a magnet and a spacer are grouped to a pole pair. There are totally eight pairs of magnet-spacer assembling together, and they are screwed on the shaft. The inducing coil was arranged on the winding base. The phase of the generated voltage depends on the magnetic field distribution, the phase angle is 90° between each nearby coil, and each two different phases of coil are connected together to increase power generating efficiency. In this design, the 0° and 180° phase coils are connected together, which is called coil A; also the 90° and 270° are connected together, which is called coil B. Thus, the 14 phase coils are wound in the winding base and combined into two inducing coils, that is, coil A and coil B. When the interaction between permanent magnets and inducing coils occurred, the vibration energy would be converted into electrics into coil A and coil B.

The magnetic circuit of the linear power generator is shown in Figure

Magnetic circuit of the linear power generator.

In order to address the magnetic field distribution and magnetic flux density on the piston head and the generating property of the linear power generator, the finite element models were built up using ANSYS software, and the issues of cogging force and magnetic interference were also discussed in this section.

As shown in Figure

In this simulation analysis, the physics environment is set as magnetic nodal option from preferences of ANSYS. The two-dimensional axisymmetric entity model of the MR damper part is built up as shown in Figure

Modelling of the MR damper part: (a) entity model and (b) finite element model.

Figure

Finite element analysis of MR damper part: (a) magnetic flux distribution and (b) magnetic flux density.

Figure

Magnetic flux density under different applied current.

Figure

Damping force versus displacement at the different applied current.

The numerical analysis was carried out to address the magnetic property for only one pole pair. It can be assumed that the reluctance values of the pole spacer are neglected for their high magnetic permeability; thus the magnetic flux is given as [^{2}),

The induced voltage

The number of turns of

Figure

Modelling of the linear power generator: (a) entity model and (b) finite element model.

Figure

Finite element analysis of the linear power generator: (a) magnetic flux distribution and (b) magnetic flux density.

Figure

Magnet force distribution of the linear power generator.

Figure

Specifications of the proposed MR damper.

Parameter | Value |
---|---|

Diameter of piston |
79 mm |

Diameter of coil space |
50 mm |

Thickness of cylinder |
5 mm |

Gaps of MR fluid |
1 mm |

Length of piston |
28 mm |

Height of gallery |
9 mm |

Length of gallery |
9 mm |

Number of turns |
250 |

Weight of coil space |
18 mm |

Diameter of excitation coil wire | 0.5 mm |

Resistance of excitation coil | 4 Ω |

Diameter of generator structure |
17 mm |

Magnet thickness |
5 mm |

Magnet height |
5 mm |

Magnet number | 8 |

Diameter of rod |
2.5 mm |

Spacer thickness |
4 mm |

Length of teeth |
2 mm |

Thickness of piston rod |
5 mm |

Length of air gap |
4.5 mm |

Coil maximum current | 1.5 A |

Coil wire turns | 256 |

Diameter of inducing coil wire | 0.5 mm |

Resistance per inducing coil | 4 Ω |

The proposed MR damper: (a) piston head, (b) permanent magnets array and shaft, (c) winding base and inducing coils of generator, and (d) the assembly.

Figure

Damping force and displacement relation of the MR damper.

Figure

Damping force and velocity relation of the MR damper.

Figure

Comparison between theoretical result and experimental data: (a) damping force versus time and (b) damping force versus displacement.

In this experiment, the measured inducing voltage from the two inducing coils A and B illustrated the properties of the linear power regenerator. The calculation data was obtained by the numerical analysis mentioned in Section

Comparison between numerical analysis result and experimental test of inducing voltage: (a) coil A and (b) coil B.

Because the inducing coils installed in the piston are equivalent as an electrical inductance, the value of generated DC voltage is better to evaluate the performance effect of proposed linear power generator compared with AC voltage. Thus, a bridge rectifier is developed, and the relevant experiment was carried out to evaluate performance of the linear power generator. The principle of the bridge rectifier is shown in Figure

Schematic of the AC-DC rectifier.

Figure ^{−1} excitation. However, there are still some noises existing in the initial data denoted as black line due to lack of filtering. There are two ways to minimize the signal noises: the first is a commercial rectifier or DAQ board should be adopted as the signal processing unit to minimize the noises from electro circuit. The second is a shield or a filter should be applied to isolate the interference from environment.

Inducing voltage of linear power generator with AC-DC rectifier.

In this study, an MR damper with energy harvesting ability was designed, fabricated, and tested. The proposed MR damper used the piston rod as the sharing component between the linear power regenerator and the MR damper part, and this shared component could isolate the magnetic field between two function areas. As a result, the magnetic field interference was minimized without extra designed shield and guild layer.

The finite element method was developed to address the magnetic field and magnetic flux distribution of the MR damper part. The simulation result proved the efficiency and feasibility of the proposed MR damper. Then the numerical method was utilized to evaluate the generating performance of the linear power generator, and the finite element model was utilized to investigate the magnetic field distribution. The issue of cogging force and minimization of the magnetic interaction had been solved.

Experimental tests were carried out to address the performances of the proposed MR damper. The results show that the damping force ranges from 200 N at the current of 0 A to 750 N at the current of 0.6 A. The dynamic range equals about 3.75. The AC-DC rectifier was applied on the power generating, and the results show that 1.0 V DC voltage output was harvested after the AC-DC processing.

The authors declare that there are no competing interests regarding the publication of this paper.

This research was financially supported by the National Natural Science Foundation of China (nos. 51475165 and 11462004), the Natural Science Foundation and the Educational Commission Project of Jiangxi Province of China (nos. 20151BAB206035 and GJJ150525), and the Australian Research Council Discovery Project (no. 1501002636).