Model-based estimation of the line tension in a fishing reel

Rotating-spool fishing reels offer several advantages with respect to fixed-spool ones, among all the bigger casting distance achieved thanks to the spool free rotation. However, the rotating spool may cause backlash as soon as the lure touches the water, since the line keeps freely going out from the spool. Backlash will eventually create annoying tangles of line around the reel, which has to be cut off, with consequent loss of time and money. The only solution is to anticipately brake the spool as soon as the backlash starts: this is mostly achieved by expert fishermen by a manual stop, and is not an easy task for beginners. This research investigates the possibility of detecting such phenomenon and building a reliable estimate of the fishing line tension, to be used in a suitable automatic spool brake control. A mathematical model of the rotating-spool is first derived, and two different estimators are then proposed to retrieve the variable of interest, used as a backlash indicator flag. The estimators are experimentally validated on two different types of fishing line, and they are shown to detect the phenomenon of interest within 100 ms at most from its beginning.