Control system tackles helicopter vibration

Technology advances

LORD has developed a next-generation AVCS that provides superior vibration control at significantly reduced weight. This modern AVCS incorporates circular force generators (CFG) which create circular instead of pure linear forces. By strategically phasing combinations of circular forces, these AVC systems can create complex forces in multiple axes. This allows the system to better match the complex vibration created by a helicopter, resulting in a lighter weight system with increased performance and fidelity.

Active vibration control systems with CFG actuators offer many advantages including:
•    Better compensation for the complex dynamics of helicopter structures,
•    Optimum broadband vibration cancellation for all flight conditions, and
•    Superior ability to track changes in rotor speed.


Cabin-based AVCS expands to light helicopters

Recently, LORD Corporation’s active control vibration system was selected for use on the Eurocopter EC130 T2 platform, a new helicopter manufactured by EADS (European Aeronautic Defense and Space Company). The EC130 T2 features enhanced comfort, improved operational performance and increased versatility for applications from aerial tourism and utility to emergency medical airlift.

The system utilized by Eurocopter features accelerometers that measure aircraft vibration levels and signals, and sends the data to a centralized computer. The computer runs a software algorithm that interprets the signals and sends commands to force generators located throughout the aircraft. These force generators create an “anti-vibration” effect that stops the progression of vibration from the main rotor.

While retaining the existing EC130’s external lines, approximately 70-percent of the EC130 T2’s airframe structure has been modified to include the AVCS. By 2013, production will transition completely to the EC130 T2 version which features AVCS by LORD Corporation.

Future of AVCS

While helicopter manufacturers continue to seek superior vibration control products with less added weight, LORD is pioneering the next-generation of solutions to resolve vibration problems – at the source. Hub-mounted active vibration control technology actively cancels rotor-induced in-plane vibration. This technology, when compared to traditional passive hub-mounted treatments, offers the possibility of real-time vibration control with the added benefit of greatly reduced weight.

Active hub systems consist of actuators mounted on the rotor head of the aircraft in contrast to classical active vibration control devices that are attached only to the cabin structure. With this approach, the ability to control or suppress vibration is moved closer to the vibration source, cancelling vibration originating from the rotor blades at the blade-pass frequency. The systems are designed to reduce weight, eliminate vibration and deliver a smoother helicopter ride across a multiple configuration of missions and roles.

Similar to a CFG, the hub-mounted active vibration control has motorized imbalanced rotors that rotate at the blade-pass frequency to create centrifugal forces. Through phasing of the two rotors, the magnitude and orientation of the centrifugal forces can be made to cancel lateral hub vibration. The system is capable of independent operation and completely self-contained – the force generator, controller, sensors, and power electronics are all included in a single unit.