Role of modern fractional derivatives in an armature-controlled DC servomotor Kashif Ali Abro, J. F. Gómez-Aguilar, Ilyas Khan and K. S. Nisar Eur. Phys. J. Plus, 134 11 (2019) 553 Published online: 06 November 2019 DOI: 10.1140/epjp/i2019-12957-6