Hardware-In-the-Loop test rig for the ISWEC wave energy system Giovanni Bracco a,⇑ , Ermanno Giorcelli a,1 , Giuliana Mattiazzo a,2 , Vincenzo Orlando b , Mattia Raffero a,3 a Politecnico di Torino, Dipartimento di Meccanica, C.so Duca degli Abruzzi, 24, 10129 Torino, Italy b Wave For Energy S.r.l., C.so Francia, 296, 10146 Torino, Italy article info Article history: Received 13 December 2013 Accepted 26 October 2014 Available online 28 November 2014 Keywords: HIL Marine energy Wave power Gyroscope abstract The Hardware-In-the-Loop (HIL) simulation is a powerful mean to reduce costs in the design and man- ufacturing process of an engineering system. HIL techniques allow to use real components inside a sim- ulation of a mathematical model. In this work such techniques are used on the ISWEC wave energy system. ISWEC (Inertial Sea Wave Energy Converter) converts sea waves energy to electric energy by means of the gyroscopic effects produced by a spinning flywheel. The peculiarity of the system lays in the fact that all the moving parts needed to produce energy are sealed inside a hull and therefore pro- tected from the aggressive ocean climate. During the research process on the ISWEC, the gyroscope and the electric generator have been manufactured and mounted on a test rig able to simulate the wave actions on the hull of ISWEC. Those real parts of the system have been replaced inside the full mathemat- ical model of ISWEC. Such HIL system is validated against real wave tank tests carried out at the INSEAN in Rome. The HIL simulations proved to reproduce the real behavior in water waves of ISWEC with errors as small as the 10%. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction In this work we address the use of HIL (Hardware-In-the-Loop) for a renewable energy application, focusing on the development and prototyping of a test-rig for the wave harvesting system ISWEC (Inertial Sea Wave Energy Converter). ISWEC research lays in the field of Wave Power, the branch of engineering studying how to harvest power from sea waves. Wave power is currently an open field. An increasing number of research institutions, governments, as well as private sector investors are becoming involved in such research subject [1]. The number of devices, based on a wide range of working principles [2–4] is growing; some projects already reached a full scale demonstration stage and are moving toward a commercially viable phase, while the growing number of patents is a clear sign of investment in emerging technologies. It is worth noticing that international and regional organiza- tions are trying to assess development stages and WECs technical and economical performances in a standardized manner. Such efforts are strongly needed to grant reliability to the industry and to allow the assessment of all devices according to widely accepted indicators. In the development process of a Wave Energy Converter (WEC), experimental testing campaigns are crucial for performance assessment. However, tank testing becomes more and more expen- sive with increasing scale of the prototype. In order to reduce time and cost of tank testing for the ISWEC, a HIL test rig able to simu- late real wave dynamics and WEC-wave interactions was manufac- tured. Indeed, Hardware-In-the-Loop techniques are nowadays more and more used to reduce time and cost of development and prototyping of engineering systems. HIL simulation is a real- time simulation technique consisting of coupling parts of a real system to a numerical model that simulates the remaining part of the whole system [5]. In this way, for instance, if a part of the system is difficult to model it can be replaced with the real part itself. On the other hand, if there is a part of the system expensive to manufacture, it can be replaced with its mathematical model. Further advantages of HIL method include the possibility to observe and study system behavior in case of system faults, mechanical parts degradation in time, effects of temperature or peculiar working environment, as well as sensor sensitivity errors. HIL methodology is very widespread for automotive and aerospace applications [6–9]. For what concerns the renewable energy field, such technique is increasingly employed in the development process [10–12] is the most relevant example of HIL application http://dx.doi.org/10.1016/j.mechatronics.2014.10.007 0957-4158/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +39 011 090 6960; fax: +39 090 6999. E-mail addresses: giovanni.bracco@polito.it (G. Bracco), ermanno.giorcelli@ polito.it (E. Giorcelli), giuliana.mattiazzo@polito.it (G. Mattiazzo), vincenzo.orlando @waveforenergy.com (V. Orlando), mattia.raffero@polito.it (M. Raffero). 1 Tel.: +39 011 090 6959; fax: +39 090 6999. 2 Tel.: +39 011 090 6949; fax: +39 090 6999. 3 Tel.: +39 011 090 6960; fax: +39 090 6999. Mechatronics 25 (2015) 11–17 Contents lists available at ScienceDirect Mechatronics journal homepage: www.elsevier.com/locate/mechatronics