In order to substitute a conventional fin operated by hydraulic actuators, a smart fin actuated by piezoelectric material was attempted. A straight unimorph actuator was embedded along the spanwise direction in the hollow inner space of the fin. A hinge which was constrained except the axial rotation was located at the 1/4th chord line, and this enabled the smart fin to rotate in its rigid pitch direction. In this paper, starting from the fundamental structural analysis, the aeroelastic and aeroservoelastic stability, and structural response simulations of the smart fin control system were performed by integration of MSC.NASTRAN, ZAERO and MATLAB/Simulink. The controller was designed to ensure the flight stability and to maintain the pitch angles of the smart fin under specific flight conditions. Closed-loop control system of the smart fin was constructed and analyzed by MATLAB/Simulink.
Helicopter uses a rotor system to generate lift, thrust and forces, and its aerodynamic environment is generally complex.
Unsteady aerodynamic environment arises such as blade vortex interaction. This unsteady aerodynamic environment
induces vibratory aerodynamic loads and high aeroacoustic noise. The aerodynamic load and aeroacoustic noise is at N
times the rotor blade revolutions (N/rev). But conventional rotor control system composed of pitch links and swash plate
is not capable of adjusting such vibratory loads because its control is restricted to 1/rev. Many active control
methodologies have been examined to alleviate the problem. The blade using active control device manipulates the
blade pitch angle with N/rev. In this paper, Active Trailing-edge Flap blade, which is one of the active control methods,
is designed to reduce the unsteady aerodynamic loads. Active Trailing-edge Flap blade uses a trailing edge flap
manipulated by an actuator to change camber line of the airfoil. Piezoelectric actuators are installed inside the blade to
manipulate the trailing edge flap.
Smart structures incorporating active materials have been designed and analyzed to improve aerospace vehicle performance and its vibration/noise characteristics. Helicopter integral blade actuation is one example of those efforts using embedded anisotropic piezoelectric actuators. To design and analyze such integrally-actuated blades, beam approach based on homogenization methodology has been traditionally used. Using this approach, the global behavior of the structures is predicted in an averaged sense. However, this approach has intrinsic limitations in describing the local behaviors in the level of the constituents. For example, the failure analysis of the individual active fibers requires the knowledge of the local behaviors. Microscopic approach for the analysis of integrally-actuated structures is established in this paper. Piezoelectric fibers and matrices are modeled individually and finite element method using three-dimensional solid elements is adopted. Due to huge size of the resulting finite element meshes, high performance computing technology is required in its solution process. The present methodology is quoted as Direct Numerical Simulation (DNS) of the smart structure. As an initial validation effort, present analytical results are correlated with the experiments from a small-scaled integrally-actuated blade, Active Twist Rotor (ATR). Through DNS, local stress distribution around the interface of fiber and matrix can be analyzed.