Designing a Universal Control Module for Unmanned Underwater Vehicles

This paper discusses the design of a universal control module for modular built unmanned underwater vehicles. Modular built in this context means that the designed control module has to be able to deal with different actuator configurations, sensor suits and general vehicle and -hull design. To be able to design such a module, two assumptions are made: Firstly, that the used actuators are limited to thrusters. And secondly, that the hydrodynamic parameters of the vehicle at hand are roughly known. To deal with this modularity, the design of the control module is built on two principles: By usage of the well known techniques of force allocation and sensor fusion a separation of the control layer from the actual vehicle configuration is achieved. And as knowledge of the vehicle's dynamics is essential for the control, the algorithms and parameters of the module are based on the known dynamic model of the vehicle. The paper concludes with the description of the design of a nonlinear controller for the motion of a vehicle as described, based on feedback linearisation and LQI-control. It is shown that by choosing the parameters of the linearised system to equal the linear parts of the vehicle's dynamics, this approach yields the same structure as a two degrees of freedom control structure that is using the nonlinear parts of the vehicle's dynamics as feedforward terms. For this controller, simulation results are given, showing its ability to control different vehicles.