  This work introduces two multi-level control strategies to address the
problem of guidance and control of underwater vehicles. An outer-loop
path-following algorithm and an outer-loop trajectory tracking algorithm are
presented. Both outer-loop algorithms provide reference commands that enable
the generic submarine to adhere to a three-dimensional path, and both use an
inner-loop adaptive controller to determine the required actuation commands.
Further, a reduced order model of a generic submarine is presented.
Computational fluid dynamics (CFD) results are used to create and validate a
model that includes depth dependence and the effect of waves on the craft. %The
model and the procedure to obtain its coefficients are discussed, and examples
of the data used to obtain the model coefficients are presented. An example of
operation following a complex path is presented and Results from the reduced
order model for each control strategy are compared.
