Modeling and control of a helicopter slung-load system

This article investigates modeling and modern control for a helicopter and slung-load system. For this purpose complex, physics based, control oriented helicopter models are used. Point mass approach is used to model the external loadʼs dynamics. The resulting nonlinear equations of motion are then trimmed for straight level flights and linearized around these flight conditions. Behaviors of representative trim variable values (i.e. cable angle and longitudinal and lateral cyclic blade pitch angles) and modes (i.e. flight dynamics and load modes) are thoroughly examined while some model parameters (e.g. cable length, load mass, and equivalent flat plate area) change. These behaviors are compared to data found in the literature. Furthermore, variance constrained controllers (i.e. output variance constrained and input variance constrained controllers) are applied for control system design. These controllersʼ performance is examined when they are aware of the slung-loadʼs existence and when they are not aware of the slung-load.