Active Pitch Link
The Active Pitch Link (APL) is the first novel, patented, and only piezoactuator-based, all-electric, high frequency active pitch link in the world. It offers a reduction of vibration of 90% in a fail-safe manner.
The APL is a stiffness control device, which is the only existing active control system designed deliberately to alter the blade root stiffness for vibration reduction in helicopters.
The Active Pitch Link (APL) is designed to replace a conventional pitch link on helicopter, which is inserted between the blade horn and the rotor swashplate, to perform Individual Blade Control (IBC) and reduce the transmitted vibration between the rotating to the non-rotating frames on a helicopter.
Based on state of the art computational models developed over several years of research, the form factor and performance characteristics of the APL can be easily scaled to meet different sizes and use requirements without any compromise to performance.
The Active Pitch Link has been tested for over 50 hours at the Whirl Tower Test Facility and confirmed 90% reduction of vibration of the 2/rev [N+1/rev] vibrations.
Periodic controlled vibrations have been generated by an implemented fan-system, with 14 m/s upwash and 20 degrees azimuth rotor radius in the rotating frame. The test results show that while the 1/rev vibratory load (corresponding to cyclic control in our system) remains largely unchanged, the 2/rev vibration is reduced by >90%.
We estimate the APL’s technology readiness level (TRL) to be at 6 (prototype demonstrated in relevant environment – Whirl Tower Testing).
The APL offers mainly a torsional control of the rotor blade and an independent reduction of vibration by >90% with a potential for simultaneous reduction of noise.
In case of any electrical or mechanical failure the APL will simply convert into a conventional pitch link that nearly all helicopters are equipped with nowadays.
The APL implementation onto a helicopter caries zero to low weight penalty due to a replacement of an existent component (pitch link) rather than adding a new system on a helicopter.
The APL has low power consumption requirements. The current generation of APL only requires 15-150 W (150V and 0.1-1A) to operate.
The APL requires much lower stroke from an actuator, which is usually the main limitation in implementing any other active vibration reduction technology on helicopters.
The APL has been designed for new helicopters with the potential to retrofit helicopters in service.
The APL is changes stiffness at high frequencies (0-200Hz) and withstands high axial, transverse and centrifugal loading at ~1000RPM.