Studies to look at reducing rotorcraft vibration wins top grad-level spot at ARL Student Symposium

August 27, 2014

By T'Jae Gibson

Kentaro Miura, a doctoral student at Pennsylvania State University, won first place in the graduate level category during the Army Research Laboratory's 8th Annual Summer Student Symposium earlier this month.

The symposium is held each summer to cultivate tomorrow's leaders in science and technology. The program enables students learning how to conduct, present, and defend their research in an ethical manner. It also provides opportunity for ARL researchers to assess the technical proficiency of the student workforce.

His presentation, "Passive Vibration Control of a Full Scale Tailboom with Fluidic Flexible Matrix Composite Tubes" describes research he pursued while here at ARL and continues to investigate at Penn State to understand the feasibility of using Fluidic Flexible Matrix Composite (F2MC) tubes to reduce vibrations in realistic structures like helicopter tail booms, or the long and vibration-prone structure that attaches to the rear of the fuselage.

All rotorcraft vibrate but high vibrations could shake loose screws or break parts and jostle the internal workings of the vehicle, like its engine, bad enough to cause malfunction or permanent damage. Add to that, high vibrations levels degrade the quality of the ride for soldiers and crews.

He said his research, which is believed to be among the first ever projects to demonstrate F2MC tubes on a real-life structure, looked at passively controlling vibration.

"There are mainly three approaches to vibration control: passive, active and semi-active. A passive vibration control device is designed for a specific range of operating conditions and requires no external power or a computer. An active controller actuates the structure to counteract vibration, and uses sensors and a control algorithm to adapt to different operating conditions. Semi-active control is sort of the middle ground; it uses a semi-active device that can alter its properties with minimal power.

"In my presentation I showed how this new device called Fluidic Flexible Matrix Composite Tubes could be used as a passive vibration control method for helicopter tailbooms," he said.

Miura said these tubes are, "in a nutshell, really good at pumping fluid. They are made of braided fibers and behave like the Chinese finger trap; they expand when you push on the ends, and contract when you pull on them. When these tubes are attached to vibrating structures they compress and extend axially, pumping fluid. In fact, F2MC tubes have been shown to pump significantly more fluid than would a piston of the same diameter. So, F2MC tubes would be a huge improvement over conventional fluidic vibration treatments that rely on piston-cylinders, from both a performance and weight perspective," Miura explained.

He spent the summer at ARL's Vehicle Research Laboratory at Aberdeen Proving Ground, Md., focusing his research around modeling and designing F2MC tubes for a test on a full-scale helicopter tailboom.

Miura developed a model of an OH-58C tailboom with F2MC tubes installed and used this model to design F2MC tubes and the accompanying fluidic circuit for the full-scale test. He developed a test plan for the full-scale test and, using a simplified version of the model, he developed some design tools for the system as well as gained physical insight.

"We are trying to answer the question: can we add significant damping to a tail boom without incurring a heavy weight penalty? Our theoretical predictions indicate that yes, it is possible. But of course, we need to demonstrate this experimentally to be sure," he said.

Miura, who is pursuing a doctorate degree in mechanical engineering, said this works builds on research he conducts at Penn State, which involves the investigation of what he called a "promising new type of fluidic device" that can be used to reduce vibration in structures. The Penn State team has been trying to control vibration in the helicopter tailboom and had run some tests on smaller structures using these devices, but his work at ARL will allow him to experiment on an actual helicopter.

 

Last Update / Reviewed: August 27, 2014