Identification and optimal control methodology for an active twist rotor

ONERA — French Aerospace Lab — developed an innovative rotor concept, featuring two independent piezo-electric actuators embedded within each blade. This patented concept allows a dynamic modification of the blade twist during a rotor revolution. The main goal is to reduce drastically the vibrations transmitted to the helicopter mast and structure, thus reducing simultaneously the fatigue and maintenance needs of the structural elements in the long term, as well as the discomfort felt by pilot and passengers. In order to ensure the stabilization of the rotor, as well as the effective decrease of rotor vibrations, a closed-loop control scheme is currently developed and simulated by ONERA Systems Control and Flight Mechanics Department (ONERA/DCSD). An adaptive, Kalman-filter based, estimation of the open-loop transfer is made, then a linear quadratic optimal control gain is calculated in order to ensure the convergence towards the objective values. During the initial part of the project, this control law is simulated through a coupling with a rotor calculation code, and the numerical results show an effective reduction of the various vibration components. After these validation steps, the control law has been implemented in a real-time environment and will be used for the wind-tunnel test phase of the active rotor.