Control of modular aerial robots: Combining under- and fully-actuated behaviors

This work presents the design of flight control algorithms for set-point stabilization of a class of modular aerial vehicles obtained by rigidly interconnecting a number of single ducted-fan aircraft. Interestingly enough, for such a modular configuration, certain types of interconnection structure between the different modules may lead to redundancy both in term of the overall number of actuators available onboard and in the number of degrees of freedom that can be actually governed simultaneously. The design of the control policy for such a complex dynamical behavior is handled by defining specific control allocation algorithms for each possible case (for which a taxonomy is given in the paper) and by deriving an overall control structure capable to switch among these policies according to the properties of the selected configuration. This approach results in an architecture that combines classical control schemes for under-actuated air vehicles - such as those employed in most Vertical Take-Off and Landing (VTOL) aircraft - with control strategies for fully-actuated vehicles.