NOVEL CONCEPT FOR REALIZING INDIVIDUAL BLADE CONTROL (IBC) FOR HELICOPTERS

Abstract

In order to increase the acceptance of helicopters, the German Aerospace Center (DLR) has for many years been researching on technologies for active rotor control which contribute to the solution of different problems of helicopters (e.g. high noise emissions, high cabin vibrations and power consumption, low maximum cruising speed, high blade loads). These inherent problems are primarily resulting from asymmetric airflow on the rotor during forward flight as well as – depending on flight attitude and forward speed – from interactions of the blade tip vortices with following rotor blades (BVI) or other components of the helicopter. Active rotor control superimposes additional control signals on the pilot signal, changing the pitch angles of the rotor blades to alleviate the aforementioned problems. Many different technical approaches to active rotor control are well-known. A concept significantly diverging from the approaches existing up to date is the multiple-swashplate control system which is introduced in this paper as an alternative to the established active rotor control concepts. As an introduction to the subject, this paper first outlines a short motivation for active rotor control and provides a brief overview of the state of the art and the different approaches. Advantages and disadvantages of the different technologies are mentioned. The paper provides an overview of the function, underlying principles and design of the essential components of the multiple-swashplate control system for IBC applications and the integration into the rotor test rig of the DLR. The main focus is on the principles of pri-mary rotor control as well as Higher Harmonic Control (HHC) and Individual Blade Control (IBC) using electro-hydraulic actuators in the nonrotating frame. The last part of this paper outlines the current state of the project and discusses experiments planned once the necessary hardware is available.