Safe operation of an autonomous underwater towed vehicle: Towed force monitoring and control

On underwater towed systems, the towing cable plays an important role in transmitting electric signals and towing forces. Hence, it is strongly recommended to monitor the towed force for preventing cable breaks and making use of it more efficiently; however, most existing underwater towed systems do not have such a capability. This paper discusses towed force monitoring and control for safe operation of an autonomous towed vehicle that is a kind of autonomous underwater vehicle (AUV). We first overview the autonomous towed vehicle and describe our related previous works. We then present our towed force measuring and monitoring manners and an experimental methodology for obtaining the feasible range of the towed force. In addition, towed force estimation only with vehicle dynamics is presented for the case when the towed force sensor became useless. Finally, we discuss towed force control to keep the towed force inside its feasible region.