Fig. 2:Digital Clay prototype and actuator with embedded
sensor is examined by inventor Dr. Haihong Zhu
An affiliation of the FPMC with activities in tribology, noise control (acoustics), and design has expanded
the relevant fluid power problems addressed through the Center.
Georgia Tech Tribology Laboratory
Professor Richard Salant of Georgia Tech’s Tribology Laboratory, is one of the preeminent experts in the
behavior and design of fluid seals, a critical element in every fluid power system. Over the last ten years, this
laboratory has been developing simulations of rotary lip seals. The effort has been concentrated on elucidating the
basic operating principles and developing predictive computer models. This led to the first elastohydrodynamic
models of the rotary lip seal that explain both the sealing mechanism and the load support mechanism. It
was found that the lubricating film plays a central role in the operation of these seals. The flow in the lubricating
film was found to interact with the asperities on the lip surface so as to hydrodynamically generate load support
to maintain the film, as well as a reverse pumping effect to prevent leakage. These mathematical models were
later expanded to include thermal and transient effects. Work on the effects of shaft surface finish has shown
that very small levels of roughness on the shaft surface can produce large effects on the seal behavior, increasing
the reverse pumping rate and decreasing the liftoff speed (the minimum speed at which the lip lifts off the shaft
and establishes a continuous lubricating film).
The most recent project of this laboratory involves the development of a numerical model (and associated
computer program) of a generalized reciprocating hydraulic rod seal, including mixed lubrication and surface
roughness. Such a model will be capable of predicting the key seal performance characteristics, such
as leakage and friction. The model consists of three coupled analyses: a fluid mechanics analysis, a deformation
analysis and a contact mechanics analysis. Since these analyses are strongly coupled, an iterative
computational procedure is used. The model is to be validated through comparisons of model predictions
with experimental measurements and observations.
Integrated Acoustics Laboratory (IAL)
Georgia Tech’s Integrated Acoustics Laboratory (IAL) is a state of the art research and education facility
dedicated to the study of acoustics and vibration. A number of graduate research programs have used the
IAL resources, including an investigation of automotive component noise and vibration paths, an investigation
of the noise produced by a hydraulically-powered fastener installation technology, and research into
acoustic testing methods. Whereas noise is one of the primary obstacles cited in the further use of fluid
power, cooperation with Professor Kenneth Cunefare, director of this laboratory, brings a valuable dimension
to the activities surrounding the FPMC.
The IAL is centered around three major test facilities: a full anechoic chamber, hemi-anechoic chamber, and a
reverberation room (see Fig. 3). All test chambers are isolated from the hosting structure and operate over a
frequency range of 80-10,000 Hz. Each chamber is equipped with a dedicated multi-channel data acquisition
system as well as extensive supporting instrumentation for the support of simultaneous research in all areas of
the laboratory. The lab also has a scanning laser vibrometer.
Fig. 3:Reverberation chamber configured for acoustic absorption measurement
The IAL has the resources to support modeling the acoustics and vibrations of complex structures. Of particular
interest here is noise from hydraulic components, in particular from pumps. Researchers within the IAL have developed integrated software tools to perform acoustic design optimization.
Fig. 4:Scanning laser vibrometer image of brake rotor in
squeal
The Active Noise Control Laboratory, associated with the IAL, focuses on advanced concepts in active
control. Ongoing research includes brake squeal control (Fig. 4) and state-switched vibration absorbers. With
respect to brake squeal, the research group has been investigating the use of dither control for the suppression
of squeal, and has demonstrated its potential in that application.
Advancement of Design Technology for Fluid Power Systems
Cooperation of the FPMC with faculty of Georgia Tech’s System Realization Laboratory opens the door
to a systematic incorporation of new knowledge on fluid power and motion control into the design process
for systems with fluid power elements.
Continuous advances in computing and networking capabilities are fundamentally changing the discipline of engineering design. There is abundant capacity to
capture and store huge volumes of data about engineered systems and processes; there is processing
power to quickly perform complex analyses and optimizations; and there is networking bandwidth to share
large datasets in real-time among distant collaborators. The challenge is to use all these capabilities such that
they improve the designer’s ability to make rational decisions. To support decisions, one needs to provide
the appropriate supporting information quickly, accurately and economically. This is the focus of Dr. Chris
Paredis’ research:
How should one discover, formalize, catalogue, retrieve and apply design knowledge in an efficient manner,
resulting in accurate information in support of product lifecycle decisions?
Dr. Paredis addresses these questions from a fundamental, theoretical perspective. It is his vision that
information can be generated efficiently through the development of modular, composable, and reusable
knowledge representations, while the accuracy issue can be addressed through the development of novel,
formal, more expressive representations and methods for uncertain knowledge and information.
More Information
The 2005 Annual FPMC Industry Status Review
showcased projects grouped into three categories:
- Component and System Design and Control
- Haptics
- Vibration Control.
Detailed summaries of those projects can be
reached through http://www.me.gatech.edu/wayne.
book/fpmc05/Index.htm
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