In mineral processing industries, grinding process is performed in tumbling mills that describe a class of mills delimited by a cylindrical chamber filled with balls and/or rock that rotate around its longitudinal axis. These tumbling mills range in size from small 0.3 m diameter lab mills to a 16 m diameter semi-autogenous industrial mill and are driven by chain and sprocket (lab mills), gear and pinion (pilot and industrial scale mills) and gearless drives in very large diameter mill (8 to 12 m dia.). All of these mill drives present advantages and limitations. In this work, we focus on the...