Patent ID: 8185259

Claim:
A fuzzy logic-based control method for a helicopter carrying a suspended load, comprising the steps of: providing a helicopter attitude and position tracking controller, the controller being designed to generate outputs for stabilizing the helicopter while accepting tracking commands from a reference source and displacement commands from a feedback source as inputs, the design including feedback gain (k) based on minimizing a load swing history, wherein the load swing history is represented by a Linear Quadratic Regulator method, the Linear Quadratic Regulator method depending on minimizing the quadratic function, Indx = ∫ 0 t f ⁢ ( ⅇ T ⁢ Qe + η T ⁢ R ⁢ ⁢ η ) ⁢ ⁢ ⅆ t wherein Indx represents the feedback gain matrix integral over time tf, wherein η T and η represent helicopter control inputs, wherein e T represents an error signal, wherein Qe represents an angular velocity of a helicopter, and wherein R is a position vector of the load with respect to a center of mass of the helicopter; determining helicopter dynamics, suspended load forces and suspended load dynamics, the suspended load dynamics including load swing angles; providing a fuzzy logic-based anti-swing controller, the fuzzy logic-based anti-swing controller issuing the displacement commands to the helicopter attitude and position tracking controller, the displacement commands being based on fuzzy logic rules operable on a plurality of normalized fuzzy membership functions governing all fuzzy inputs and outputs and derived from time-delayed feedback of the load swing angles represented by the equation: xs=k dx LΦ L ( t−τ dx ) ys=k dy Lθ L ( t−τ dy ) where xs and ys are additional displacement outputs added to the helicopter trajectory in a longitudinal and lateral direction, wherein φ L is the load angle in a xz plane and θ L is the load angle out of a xz plane, respectively, k is a feedback gain, L is a load cable length and τ is a time delay introduced in a feedback model of the load swing angles, the fuzzy inputs including θ L and θ L rate, the fuzzy outputs including a longitudinal displacement; optimally selecting values for the k, and τ parameters by minimizing an index function expressed in terms of a time history of the load swing, the index function minimizing being performed using an evolutionary computation algorithm; and implementing an optimized fuzzy logic-based anti-swing controller in a feedback control loop with the tracking controller to achieve suspended load swing reduction of the suspended load and stability control of the helicopter.