A coordination control strategy is developed for 3-bearing swivel duct(3BSD) nozzles. A 3BSD nozzle's deflection angle and direction are changed through rotations of three revolute pairs. There is a nonlinear relationship between the deflection angle/direction and the rotation angles. The rotation speed of a revolute pair is limited by the power of the actuator. The moment of inertia and the aerodynamic load for each revolute pair are different and time-varying. A high-precision control system of 3BSD nozzles is required for applications on vertical and/or short take-off and landing(V/STOL) aircrafts. Difficulties of coordination control of 3BSD nozzles are distinct travel ranges, speed constraints, time-varying dynamic models, and disturbances. The proposed control strategy is a combination of the characteristic model and the dynamic control allocation method. A dynamic control allocation module is used as the coordination supervisor, which is aware of the kinematic model, the constraints, and the dynamic models of the revolute pairs. Second-order characteristic models are used to represent the dynamic behavior of the revolute pairs. The gradient projection algorithm is modified for parameter estimation. A modified all-coefficient adaptive controller is developed to reject the disturbances. Experimental results of a scaled 3BSD nozzle indicate that the coordination control strategy is effective.
