Canada’s National Research Council has won a patent on “an active and adaptive rotor-blade control system called Smart Spring,” which is designed to reduce the noise and vibration when rotor blades interact with the vortices shed by the tip of the preceding blades. Previous engineering approaches, according to NRC, have attempted to alter the varying aerodynamic load on the blades to reduce the onset of this vibration. NRC took a different approach with Smart Spring.
The system consists of accelerometers, a signal-analysis processing computer and piezoelectric actuators used to exert forces in response to an applied voltage. The piezoelectric actuators are located near the blade root, where the loads are highest and damping forces have the greatest effect. A signal-processing computer analyzes the output from the sensors to measure the amplitude and mode of blade vibration, and it uses this information to control the piezoelectric actuators that change the blade torsion stiffness.
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