**1. Introduction**

486 Smart Actuation and Sensing Systems – Recent Advances and Future Challenges

Enrico Zenerino, Joaquim Girardello Detoni and Andrea Tonoli

*Mechatronics Lab, Politecnico di Torino, Italy* 

*Mechatronics Lab, Politecnico di Torino, Italy* 

*Mechatronics Lab, Politecnico di Torino, Italy* 

*Magnetics*, Vol. 43, No. 11, pp. (3940-3950).

*system,* IEEE, ISBN 978-1-4244-6789-1

Physics Publishing.

IEEE, ISBN 978-4577-0752-0

Vol.59, pp. (154-159)

*Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Italy* 

*Department of Electronics and Telecommunications, Politecnico di Torino, Italy* 

*Harvesting from Low-Speed Flows,* IEEE, ISBN 978-1-4244-4193-8

Implementation in in Developing Cuntries, Third Printing

Vol.19, (August 2009), pp. (1-8), ISSN 0960-1317/09/094010

*Transactions On Industry Application*, Vol.43, No.2, pp. (505-512)

Mediterranean Electrotechnical Conference, pp. (1516-1521). Lu, X.; Shuang-Hua, Y. (2010). *Thermal energy harvesting for WSNs* 

Nechleba, M (1957). *Hydraulic Turbines. Their Design and Equipment.* ATIA ,Prague

Arnold, D.P.; (2007). Review of Microscale Magnetic Power Generation, *IEEE Transactions on* 

Bansal, A.; Howey, D.A.; Holmes, A.S. (2009) - *CM-Scale Air Turbine and Generator for Energy* 

Chunyan, M.; Gengxin, L. (2010). *Research on a self powered wireless ultrasonic flow sensor* 

Hendershot, J. R.; Miller T. J. E. (1994). *Design of brushless permanent-magnet motors*, Magna

Inversin, A.(1994). *Micro-Hydropowe Soucebook*, A Pratical Guide to Design and

Kim, S.; Ji, C.; Galle, P.; Herrault, F.; Wu, X.; Lee, J.; Choi, C and Allen, M. G. (2010). An electromagnetic energy scavenger. *Journal of Micromechanics and Microengineering,* 

Lineykin, S.; Ben-Yaakov, S. (2007). Modeling and Analysis of Thermoelectric Modules, *IEEE* 

Lossec, M.; Multon, B and Ahmed, H.B. (2010). Micro-kinetic Generator: Modeling, Energy Conversion Optimization and Design Considerations Proceedings of the IEEE

Valdes, L.C. (2004). Competitive solar heat engines, *Renewable energy*, Vol. 29, pp. 1825-1842 Yan, T.C. ; Ibrahim, T. ; Nor, N. M. (2011). *Micro Hydro Generator Applied on Domestic Pipeline,* 

Zainuddin, H. ; Yahaya, M. S. ; Lazi, J. M. ; Basar, F. M. ; Ibrahim, Z. (2009). Design and Development of Pico-hydro Generator System for Energy Storage Using Consuming Water Distributed to Houses, *World Academy of Science, Engineering and Technology,* 

**Author details** 

Marcello Chiaberge

Diego Boero

**6. References** 

Magnetoelastic materials belong to the wide category of smart materials because of their capability of coupling mechanical quantities (force, strain) to magnetic ones (field, induction) and viceversa. Recently, they have received a lot of interest for actuating and sensing purposes. Moreover, in the general framework of recovering some environmental energy, this kind of smart materials have been considered to recover the mechanical energy of vibrations [51].

Indeed, by employing the inverse magnetostriction or *Villari Effect* [26], it is possible to scavenge the vibration energy by means of the induced magnetization change in the material to generate electrical power. This opens the possibility to have a regenerative source of electrical power, especially useful in harsh environments. For this reason, this kind of technology can result of great interest in several application fields, such as health monitoring of civil infrastructure (bridges, buildings), automotive and biomedical tasks. Magnetostrictive alloys (Terfenol, Galfenol, Metglas) are actually the most known and employed magneto-elastic materials in this kind of applications. Nevertheless, they have interesting properties like high energy densities, high bandwidth, absence of depolarization phenomena that make them complementary to the piezoelectrics.

Energy harvesting techniques from vibrations have a promising future in civil engineering, where a strong need of structural monitoring of the health of ageing bridges and structures is occurring [17]. Indeed, for all civil infrastructure in general, it is possible to infer the structural health by measuring accelerations and resonant frequencies [21, 31]. Usually, the resonant frequencies are measured in suitable places along the structure by using the vibrations induced by wind or traffic [4, 27, 30]. Moreover, the sensors can detect other local environment parameters as well, namely temperature, wind speed, humidity, etc. Once the data are measured, among all the possible transmission techniques, the wireless method is

©2012 Visone et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0),which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### 2 Will-be-set-by-IN-TECH 488 Smart Actuation and Sensing Systems – Recent Advances and Future Challenges

undoubtedly the more effective because, for example, it reduces costs with respect to periodic human intervention and it improves reliability with respect to wired solutions. The use of sensors together with wireless transmission results in the so called wireless sensors networks (WSN) [7]. Of course, in the same line of reasoning, the source of electrical power for the WSN should be self-contained too. The easiest choice could be then the use of batteries but, due to the limited life-span of them, an increment of the sensors maintenance whole costs should be considered, with the aggravation of workers safety concerns because the sensors can be located in inconvenient places along the bridge. Then, smart renewable energy methods should be used instead. Solar and thermal harvesting have been proposed [43] but these solutions can be both costly and bulky. Nevertheless, bridges as many other civil infrastructure vibrate because of the wind action and of traffic loadings or, when presents, for trains traffic loadings. The possibility to convert this ambient mechanical energy, otherwise wasted, into electrical energy is very attractive in those applications [36, 39]. So, together with measurements purposes, vibrations can be harvested to feed the sensors.

It is worth that this type of conversion could be performed by means of linear electromagnetic generators too [20, 47]. In those devices, a proof mass oscillates with the structure, making a permanent magnet move linearly in a coil. This solution is undoubtedly well assessed and reliable. But, usually, this type of device has a narrow bandwidth that can be broaden at the cost of a very sophisticate mechanical construction. Another conversion technique, as already introduced, can make use of smart materials instead. These devices can be in principle less bulky and with higher reliability, because of their simpler mechanical design and construction.

Another field of application for energy harvesting from vibration is the automotive one. In fact, on one hand, the society is looking forward for vehicles more and more efficient. On the other hand, moving vehicle are site of vibrations of two different kinds. The first is due to the *internal* combustion engine operations and so, whenever the engine is on, a source of vibration is present. These vibrations are usually damped by means of engine rubber supports or even more complicated ways, while they could be used to recover some more energy. Obviously, the vibrations level is higher in big vehicles like trucks or tractors. A second source of vibrations can be referred as *external* and it is intrinsically related to the vehicle movement and interaction with the roads irregularities. It is apparent that both of them can be exploited to scavenge electrical power, instead of wasting the energy in rubber damping or shock absorbing. Also in this case, the harvested power can be used to recharge the vehicle battery or for feeding monitoring sensor nodes. A typical example is a tyre pressure sensor, [46]. In this case, the knowledge of the tyre health and pressure status allows to reduce the fuel consumption and to limit accidents. Another example of application on vehicles is the mechanical energy harvesting on the suspension system. Noting that the electrical energy transfer on the load (*e.g.* the battery) is strictly related to the mechanical source damping, this kind of solution can be conceived also for obtaining shock absorption, [54]. This additional feature is very attractive for enhancing the comfort of the passengers, particularly for workers (*e.g.* on trucks or tractors).

The harvesting from vibrations can be also considered in flying vehicles. In this case the vibrations are induced on the wings by the movement in the air flow. In [2], a sheet of piezoelectric material on the wings of an unmanned plane is applied making a harvester in a sort of unimorph cantilever arrangement.

Another potential huge field of application for vibrations harvesting is the biomedical one [32]. In this case the source of vibrations is the human gait (walking and running) and it could be used to power devices aimed to monitor human health conditions, [18], out of personal multimedia readers, smartphone, etc. In this framework of human activities induced vibrations, even the movement of the heart muscle has been conceived as a possible energy source to feed internal biomedical devices as pacemakers, [23].

Aim of this chapter is to discuss the main achievements and the open challenges in the field of vibrations energy harvesters based on magnetostrictive materials. This is a very attractive field involving the modeling of active materials that, with their complex behavior, are the link between the mechanical and the electrical *worlds* and so represent the path by which a *smart* electromechanical conversion can take place.

Different modeling strategies will be considered, ranging from the basic linear one [22, 45] allowing to understand the device working principles to the more accurate nonlinear approaches [10, 50], outlining their impact on the practical design of the harvester. To this aim, some detail on the experimental setup for material characterization, [1, 11], the modeling of the mechanical source and its coupling to the active material will be presented.

Finally, many open problems will be also reviewed, such as the power conversion stage requirements, the main arrangements (bulk or cantilevers) of magnetostrictive harvesters in connection to the different fields of applications.

The chapter is structured as follows:

2 Will-be-set-by-IN-TECH

undoubtedly the more effective because, for example, it reduces costs with respect to periodic human intervention and it improves reliability with respect to wired solutions. The use of sensors together with wireless transmission results in the so called wireless sensors networks (WSN) [7]. Of course, in the same line of reasoning, the source of electrical power for the WSN should be self-contained too. The easiest choice could be then the use of batteries but, due to the limited life-span of them, an increment of the sensors maintenance whole costs should be considered, with the aggravation of workers safety concerns because the sensors can be located in inconvenient places along the bridge. Then, smart renewable energy methods should be used instead. Solar and thermal harvesting have been proposed [43] but these solutions can be both costly and bulky. Nevertheless, bridges as many other civil infrastructure vibrate because of the wind action and of traffic loadings or, when presents, for trains traffic loadings. The possibility to convert this ambient mechanical energy, otherwise wasted, into electrical energy is very attractive in those applications [36, 39]. So, together with

It is worth that this type of conversion could be performed by means of linear electromagnetic generators too [20, 47]. In those devices, a proof mass oscillates with the structure, making a permanent magnet move linearly in a coil. This solution is undoubtedly well assessed and reliable. But, usually, this type of device has a narrow bandwidth that can be broaden at the cost of a very sophisticate mechanical construction. Another conversion technique, as already introduced, can make use of smart materials instead. These devices can be in principle less bulky and with higher reliability, because of their simpler mechanical design and construction. Another field of application for energy harvesting from vibration is the automotive one. In fact, on one hand, the society is looking forward for vehicles more and more efficient. On the other hand, moving vehicle are site of vibrations of two different kinds. The first is due to the *internal* combustion engine operations and so, whenever the engine is on, a source of vibration is present. These vibrations are usually damped by means of engine rubber supports or even more complicated ways, while they could be used to recover some more energy. Obviously, the vibrations level is higher in big vehicles like trucks or tractors. A second source of vibrations can be referred as *external* and it is intrinsically related to the vehicle movement and interaction with the roads irregularities. It is apparent that both of them can be exploited to scavenge electrical power, instead of wasting the energy in rubber damping or shock absorbing. Also in this case, the harvested power can be used to recharge the vehicle battery or for feeding monitoring sensor nodes. A typical example is a tyre pressure sensor, [46]. In this case, the knowledge of the tyre health and pressure status allows to reduce the fuel consumption and to limit accidents. Another example of application on vehicles is the mechanical energy harvesting on the suspension system. Noting that the electrical energy transfer on the load (*e.g.* the battery) is strictly related to the mechanical source damping, this kind of solution can be conceived also for obtaining shock absorption, [54]. This additional feature is very attractive for enhancing the comfort of the passengers, particularly for workers

The harvesting from vibrations can be also considered in flying vehicles. In this case the vibrations are induced on the wings by the movement in the air flow. In [2], a sheet of

measurements purposes, vibrations can be harvested to feed the sensors.

(*e.g.* on trucks or tractors).

