Experimental evaluation of the Smart Spring for helicopter vibration suppression throughblade root impedance control

Abstract

Most active approaches for helicopter rotor vibration suppression require active materialbased actuators to provide large force and displacement simultaneously. However, successfulimplementation has been hindered by the performance limitations of the actuators. TheSmart Spring is a unique structural impedance control approach that employs piezoelectricstack actuators efficiently to suppress blade vibration. This paper presents the principles ofthe Smart Spring to control helicopter blade root impedance to suppress vibration. Openloop experiments were conducted to identify the impedance properties of proof-of-conceptSmart Spring hardware before and after installation of a helicopter blade section. Anadaptive algorithm was implemented using the Matlab xPC Target platform to controlblade impedance properties. Closed-loop tests were conducted on the blade sectionusing a mechanical shaker to provide representative disturbances. Significantreduction in blade vibration and torque reaction force was achieved simultaneously.Experimental results indicated that the Smart Spring is a promising approachfor helicopter individual blade control applications to suppress rotor vibration.