摘要：AbstractIn the Landing Experiment of the Reusable Launch Vehicle (RLV-LEX), RLV (aircraft) is connected to the helicopter, using mattelic strings, through an RLV Interface System (RIS). The aircraft is carried at a constant speed by the helicopter. RLV is directionaly unstable and is to be aerodynamically controlled precisely before releasing from RIS. Control law synthesizing requires a mathematical model of RLV lateral-directional dynamics in underslung condition. In this paper, aircraft lateral-directional dynamics in hanging condition are derived using an equivalent triple pendulum analogy, with the gravity, aerodynamic forces, and moments acting on the pendulum. The lagrangian method is used to develop the mathematical model. The triple pendulum model is extended with the aerodynamics force and moments acting on pendulum and the generalized force used in Lagrange’s equation has been computed. Futher, the lateral-directional channel coupling aspect of aircraft is considered, where pendulum dynamics is coupled with directional dynamics of the aircraft. The non-linear model is linearized about an operating point for control law design. The developed model is extremely simple to synthesize control law and its response is sufficiently close to the response simulated using Kane’s method.
