The Hindu : Karnataka News : `Smart' vibration damper for ALH

Online edition of India's National Newspaper
Monday, Jul 19, 2004

Karnataka

Karnataka

`Smart' vibration damper for ALH

By Harichandan A. A.

BANGALORE, JULY 18. A Hindustan Aeronautics Limited (HAL)-Indian Institute of Science (IISc) project on using `smart materials' to reduce vibrations in HAL's indigenous Advanced Light Helicopter, may come out with a working model, as early as next year.

Ashok K. Baweja, Director of Design and Development at HAL, told The Hindu , "We funded this project with about Rs. 6 crore and (the) scientists at IISc's Department of Aerospace are working closely with our Rotary Wing Research and Development Centre (RWRDC)."

"We use piezoelectric materials, (substances that change structure in response to an electric current) that will change themselves depending on the vibration. The deflection (in the rotor blades) they cause will oppose the deflection caused by the natural vibration of the helicopter and so reduce it," Mr. Baweja said.

N.R. Mohanty, Chairman of HAL, said: "the ALH already meets international standards. What we are doing with IISc is to bring the vibrations down even further. Call it value addition." The ALH is considered to be a best-in-class aircraft and HAL estimates a market for some 300 aircraft, HAL officials said.

While the first working model of the damper may be ready by next year, the scientists at IISc feel it will take five years to build one that can finally be fitted onto the helicopter's rotors. They are working on a "control algorithm" that, when finished, will look at the vibrations of the helicopter, and send suitable electronic signals to "twist" the rotor blades in such a way as to reduce the vibration, even as the chopper was in full flight.

This is done by the use of smart materials of two types — piezoelectric ceramics and Magnetostrictives, which, as their names suggest, are amenable to changes in their structures when subjected to an electric or a magnetic field, respectively. These materials, which can be either "surface mounted" or "embedded" in the rotor blades, will respond to commands from an onboard computer and twist the blades by up to two degrees, reducing vibrations by up to 60 per cent.

But there are hurdles to be cleared, the researchers said.

Helicopters are subject to "unsteady aerodynamic forces" as they use their rotors for providing both lift and thrust (moving forward). They also work in "environments of high (electronic and/or electrical) noise". The control algorithm then must be robust enough to handle measurements made in such environments.

Further, much work was needed on the "operational capability of the smart materials themselves — for example, on their fatigue tolerance. Finally, actual flight tests would have to be conducted repeatedly to generate enough data to validate the research work and make necessary corrections.

At present, American aerospace major, Boeing is probably the only company to be running flight tests on a helicopter. However, no commercial helicopter was equipped with such a system, yet, the scientists said.

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