Helicopter Active Trailing-edge Flap With Piezoelectric Actuator

Vibration and noise are primary barriers which limit the further improvements ofthe helicopter efficiency. The current rotor researches mainly focus on improving thehelicopter performance by reducing unwanted vibration. An active trailing-edge flap isone of the most effective approaches to fulfilling active rotor blade vibration control. Itis more promising than ever before to improve the performance of active trailing-edgeflap due to the development of smart materials, such as shape memory alloys, shapememory polymers and piezoelectric materials. Since piezoelectric materials possess thecharacteristics of high response frequency, easy to control, small volume and lightweight, they have shown outstanding advantage for smart actuators which can be usedin active trailing-edge flap. In this thesis, a piezoceramic actuator has been designed forthe study of active trailing-edge flap. Therefore, the research aims to promote theengineering application foundation of the helicopter rotor active vibration control viaactive trailing-edge flap with piezoelectric actuator.A theory of rotor vibration control with active trailing-edge flap has beenintroduced. Two aerodynamic models of trailing-edge flap airfoils were conducted inthis paper, including the quasi-steady Theodorsen model and the unsteadyHariharan-Leishman analytical model. Furthermore, two numerical examples weregiven to demonstrate the aerodynamic influence on the trailing-edge flap at differentflight conditions. The flap deflection amplitude and frequency have grate influence ofrotor aerodynamic coefficients.A rhombus piezoelectric actuator has been designed for active trailing-edge flap.Design and analysis of rhombus amplification using simplified mechanical model wereinvestigated in this paper. In order to obtain an optimal output displacement of thepiezoelectric actuator, the geometry size of the amplification structures had been takeninto account. The effects of the joint stiffness and the structure deformation have beendiscussed. The finite element model of the rhombus piezoelectric actuator has beenestablished by ABAQUS, and the response of the piezoelectric actuator at differentvoltage was analyzed.The trailing-edge flap actuated with rhombus piezoelectric actuator bas been testedin the evaluation experiments, and the response of trailing-edge flap with different inputvoltage, including direct current and alternating current was obtained. At the conditionof190V D.C, the trailing-edge flap showed a6°deflection; when applied with A.C, thetrailing-edge flap showed a20Hz frequency. Based on the experimental data, a transferfunction of trailing-edge flap has been conducted by the system identification method.Finally, a closed loop active trailing-edge flap system has been established with PID controller, and the PID controller gains which minimize the system error were selectedby optimization technique.