Simulation and active control of towed undersea vehicles

Towed undersea vehicles are used extensively in the field for activities such as fish stock assessment, petroleum exploration, and minehunting. The accurate positioning of the vehicle in time and space is often critical to ensuring useful measurements are obtained from onboard sensors. This paper discusses the development of a simulation facility aimed as a design tool for the development of towed undersea vehicles. The simulation was developed in two parts: the cable dynamics simulation, and the vehicle simulation. The cable is simulated using a lumped mass approach in which the cable is discretized into a number of nodes and the equations of motion are then written for each node. The vehicle simulation is a 2D implementation of a previously-developed 3D untethered vehicle model. Both the cable and vehicle models were validated using data available in the literature. The two models were then coupled to form the complete towed vehicle simulation. The system of differential equations describing the motion of the nodes and vehicle is solved using a fourth order fixed time step Runge Kutta integrator. The use of this simulation is then demonstrated in an evaluation of the depth and pitch control obtained in a bottom-following task.