Adaptive attitude control of suspended cargo from aerial vehicles under operational constraints

The nonlinear problem of controlling the attitude of a suspended cargo during transportation and various flight phases of an aerial vehicle is considered. The control system requirement is to provide independent cargo attitude control relative to the aerial vehicle. The suspension is done by a cable and a pair of spherical joints on both sides, resulting in a system containing two oscillations of the cable and a two-dimensional rotation of cargo, simplified as a double spherical pendulum model. The technical solution is obtained by a reaction wheel system installed in the cargo and an Omni wrist at the pivot point. Different stages of flight, agile movement of the drone, and highly perturbed environments require a robust control capable of being adjusted rapidly to new operating conditions. Attitude control algorithms are synthesized based on the newly developed optimized integral sliding mode, and the sufficient conditions of reachability and convergence for the nonlinear case are derived. The efficiency of the algorithm is confirmed by the results of numerical simulation.