A dynamic model to maintain the depth of underwater towed system

Underwater towed system have the increasing applications for exploring underwater environments. The depth and stabilization of towed system are necessary to guarantee good data accuracy. While a wide body of work exists that describes numerical models for controlling the towed system, they usually neglect the dynamic relationship between the towed body and tow cable. This paper analyses nonlinear dynamics of underwater towed system. A control model has been proposed to maintain the depth of cable towed body system during the tow ship turning maneuvers. The cable has been modeled and analyzed using the finite difference method. The towed body is modeled as a rigid body with six degrees of freedom, while the tow ship motion is treated as a moving boundary to the system. The newly dynamic model is formulated by coupling the tow cable model, towed body model and control model. A special procedure has been developed to calculate the length of the tow cable i.e. deploying or retracting speed. The simulation illustrated the significant improvement of the control model for maintaining the depth of towed system.