Active Pitch Link Actuator for Impedance Control of Helicopter Vibration

The present paper describes the design and static test results for an Active Pitch Link device developed for the SHARCS (Smart Hybrid Active Rotor Control System) project. This project aims to demonstrate the feasibility of simultaneous reduction of vibration and noise on helicopters via integrating three independent active control systems on a helicopter blade: an Active Pitch Link (APL), and Actively Controlled Flap (ACF) and an Actively Controlled Tip (ACT). The goal of the project is to design and build a 4-bladed scaled (1.096 m radius) rotor featuring all three systems and demonstrate its capabilities in wind tunnel testing. The present paper provides the details of the APL design, including the operational principle, the selection of spring stiffness, actuators and instrumentation. Static tests have been performed to demonstrate the performance of the device and they showed that the resultant system stiffness can indeed be varied continuously between two extremes set by the design requirements.