A non-ideal portal frame energy harvester controlled using a pendulum I. Iliuk, J.M. Balthazar, A.M. Tusset, J.R.C. Piqueira, B. Rodrigues de Pontes, J.L.P. Felix and Á.M. Bueno Eur. Phys. J. Special Topics, 222 7 (2013) 1575-1586 Published online: 30 September 2013 DOI: 10.1140/epjst/e2013-01946-4