Slow Speed Flight Control of Autonomous Underwater Vehicles: Experimental Results with NPS AUV II

A six degree of freedom model for the maneuvering of an underwater vehicle 15 discussed in which the hydrodynamic force coefficients are scaled from previous studies of a Swimmer Delivery Vehicle, and traditional as well as Sliding Mode controllers are designed for the steering, diving, and speed control functions. In slow speed flight control applications of this kind, difficulties arise because the system to be controlled is highly non-linear, coupled, and there is a good deal of parameter variation with operational conditions. The uncertainty in force coefficients and disturbances make control difficult. This paper presents an outline of the controller design methodology, a description of the testbed vehicle and a discussion of experimental flight control results for way point following, bottom following, and sonar mapping of the surrounding environment. It shows that a multivariable autopilot based on state feedback, designed assuming decoupled modeling, is quite satisfactory for the combined speed, steering and diving response of a slow speed AUV enabling autonomous missions to be planned.