Abstract
This paper reports on the development of an automatic thrust redistribution algorithm for a redundant autonomous underwater vehicle (AUV) in the case of thruster faults. Under favorable conditions, the transformation of the thruster force vector to the generalized body-fixed force vector can be computed in a least-squares manner, which provides the minimum norm solution. In the case of some type of thruster fault, the redundancy in the system allows for seamless redistribution of the thruster forces while maintaining the desired vehicle motion. An accurate, fault-detecting thrust estimator has been previously developed that is robust to changes in source power and propeller ventilation. Such an estimator is necessary in order to quantify the health of the thrusters, which can then be used to weigh the contribution of each thruster to the vehicle motion in a continuous manner. An example of the thruster health index in its simplest form is the approximated thrust divided by the reference thrust, passed through a moving average filter, and normalized over all thrusters. This index can effectively scale back the contribution of any faulty thruster to the body-fixed, vehicle force vector solution.
