Dynamics of circularly towed cable systems, part 2: Transitional flight and deployment control

When the towpoint of an aerial cable system moves in a tight circular path, the drogue at the cable tip moves towards the center of the circle, and its altitude decreases relative to its equilibrium position in forward flight. Such a system has both military and civilian applications, including remote pickup and delivery of payloads. This work studies the transitional dynamics of such a system as the aircraft changes from straight flight to circular flight. The system dynamics are modeled using a discretized cable model, allowing the cable to take on zero tension values. Numerical simulation results show that the cable becomes slack during the transition if the aircraft turns too rapidly. Parametric studies of the towpath are performed for both tow-in and tow-out maneuvers. Tension waves can be reduced by appropriate control of the towpoint. Simulated annealing is used to optimize some parameters used to specify the tow-in maneuver. Alternatively, a deployment controller is developed using fuzzy logic that avoids some of these problems by deploying the cable while I the aircraft orbits. Instability of deployment for certain combinations of cable length and length rate are observed.