DC Motor Control Issues for UUVs

The objective of the low level control system of marine vehicles is to generate a desired thrust in the face of environmental disturbances and modelling uncertainties. The control objective of standard low level control solutions is the propeller angular speed that is assumed to be related to the produced thrust through a known hydrodynamic model. The presented approach differs from the above as the thrust control law is designed without the use of any (either stationary or quasi stationary) explicit hydrodynamic model. The design builds on the only hypothesis that, over a wide range of operating conditions, the produced thrust is approximately proportional to the fluid induced propeller load torque. The resulting control law is presented for a voltage driven brushed DC actuator and its use within an open water ROV model identification scenario is discussed.