Flight Dynamic Simulation for Multibody Aircraft Configurations

To capture salient features of the flight dynamic behavior of some aircraft configurations, the air vehicle is best idealizedasamultibodydynamic systemwhere individual rigidbodiesare connectedvia various joint connections.This paper considers automatic generation of amultibody air vehicle simulation where the standard six degrees of freedom rigid bodymodeling forms the basic kernel of themethod. By adding an extra term to the individual body equations of motion representing joint connection constraint loads, amultibodyflight dynamicmodel canbe constructed.Aglobally stable nonlinear controller computes these constraint forces and moments. Through three modeling examples (projectile with an internal moving mass, airdrop system, and articulated wing aircraft), practical aspects of the methodology are explored. Many nonlinear control techniques can be used for the constraint control problem. Here, feedback linearization and sliding mode control algorithms are shown to work effectively. Constraint computation dominates overall simulation time, independently of the control algorithmused, and severalmeans to reduce simulation time are reported. Moreover, unconstrained linear dynamic models can be generated by combining a linear model of the constrained coordinate equations of motion and a linear model of the constraint equations. Nomenclature ET, ER = translational, m; rotational error components, rad