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MICROGRAVITY EQUIPMENT VIBRATIONS -
A SENSITIVITY AND CONTROL STUDY

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This research work is funded by the Marshall Space Flight Center in Huntsville, AL,
and is currently being performed at Clarkson University in Potsdam, NY.


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  • People involved with this research project...
  • Importance of this research...
  • Objectives of this research project...
  • Results of preliminary studies...
  • Equipment used in experimental study...
  • Photos of the progress thus far...
  • Movie of base excitation of multi-level structure...
  • Companies providing equipment and support for this work...
  • Site info including author's e-mail and snail mail addresses...

  • Marker People involved with this research project...
  • Mark Whorton, NASA Marshall Space Flight Center, Advisor
  • Goodarz Ahmadi, Clarkson University Dept. of MAE Professor, Advisor
  • Jeffrey T. Shimmel, Clarkson University Dept. of MAE Graduate Student

  • Marker Importance of this research...
    The increase of space flights and the future space station has made a new low gravity environment accessible to the science community. Potential scientific research uses of the microgravity environment include crystal growth, critical point viscosity measurements, protein growth and tissue culturing, fluid physics and transport phenomena, as well as many other experiments.

    While there is much interest in using the microgravity condition for scientific experiments, the environment on-board the shuttle has been found to be exposed to many undesirable vibration excitations. The bandwidth of these excitations is from very low frequency - less than 0.001 Hz, to around 30 Hz. The very low frequency accelerations are in the microgravity range whereas the accelerations above 0.01 Hz are several orders of magnitude above the microgravity level.

    The undesirable vibrations above the microgravity level, the so-called g-jitter, affect the performance of various other science experiments. Most earlier studies of passive and active vibration control strategies were directed towards protection of the flexible space structures. Comparatively, little attention was given to low amplitude (and low frequency) vibration control of sensitive scientific equipment aboard spacecraft. With an active control system, ambient acceleration levels on the isolation platform can be educed to about I mirco-g in the 0.1 to 10 Hz bandwidth.

    This study is concerned with sensitivity analysis of scientific equipment to orbital vibration environment, as well as with developing a practical and effective vibration control technology for microgravity application. Computer simulations and laboratory experiments will be used to provide the needed understanding of the sensitivity typical scientific devices and to test the effectiveness of vibration control strategy.

    Marker Objectives of this research project...
    One of the main objectives of this research work is to gain a fundamental understanding of the degree of sensitivity of the equipment that is used in delicate (scientific) flight experiments in the orbital vibration environment. The other main goal is to develop a practical and effective microgravity vibration control strategy. The specific objectives are the following:
  • To provide an understanding of the sensitivity of experimental flight hardware to microgravity loading including g-jitter vibrations.
  • To develop a practical design for an effective vibration control strategy for space applications.
  • To construct an experimental model for laboratory experimentation.
  • To develop passive, active and hybrid vibration control strategies with use of smart materials such as (piezoelectric and shape memory alloys).
  • To analyze the experimentally obtained data and to assess the vibration sensitivity and performance of the control devices.

  • Marker Results of preliminary studies...
    This is in progress.

    Marker Equipment used in experimental study...
    The equipment used in this research project was either donated, purchased, or built here at Clarkson University in the vibrations lab or in the undergraduate machine shop. All of these components can be seen in the photos listed below.
  • The MultiQ-3 AD/DA Board is a general purpose data aquisition and control board made up of 8 analog inputs and 8 analog outputs. The system is accessed through the PC bus and has a separate terminal board on which all of the connections to the board can be made. (This was supplied by Quanser Consulting)
  • WinCon is a real-time Windows 95/98/NT application that runs Mathworks Simulink generated code using the Real Time Workshop on a PC. WinCon consists of a client and a server and this software can be run on various setups ranging from 1 PC to an entire network of PCs. (This was supplied by Quanser Consulting)
  • The accelerometers used are Piezoelectric and are powered by simple, inexpensive, constant-current signal conditioners. These sensors are easily placed into systems having a fixed voltage sensitivity, low per channel cost, and low-impedance output. (These were supplied by PCB Piezotronics)
  • The accelerometer power supply is an 8-channel singal conditioner with a selectable gain from 1x, 10x, to 100x. This unit is a line-powered, 8 channel digitally controlled amplifier that provides constant-current excitation to up to 8 transducers. (This was supplied by PCB Piezotronics)
  • The vibration exciter is a versatile instrument that operates in the frequency range of 10Hz to 20kHz with a maximum obtainable bare table frequency with assisted air cooling of 100 g's, and a maximum of 60N of force. (This was supplied by Brel & Kjr)
  • The power amplifier for the vibration exciter has a maximum of 75VA and is switchable between 1.8A and 5A. It has low distortion over a wide frequency range and a built in attenuator with variable gain control and along with sensors to detect heat build up as well as clipping in the signal. (This was supplied by Brel & Kjr)

  • Marker Photos of the progress thus far...
    (Please be patient while these load - use the back button on your browser to return here.)
  • Brel & Kjr shaker attached to structure. - The complete experimental setup. (20.6Kb)
  • A PCB accelerometer attached to the first level. (11.2Kb)
  • Quanser Consulting A/D-D/A terminal and computer boards. (44.3Kb)
  • A view through the plexiglass window of the cover. (31.9Kb)
  • The entire experimental set-up. (32.6Kb)
  • The completed 6 low pass filters. (26.6Kb)
  • One low pass filter temporarily attached to the case for testing. (61.8Kb)
  • Another look at one of the completed low pass filters. (41.8Kb)
  • Brel & Kjr shaker power amplifier on the left - PCB accelerometer power supply on the right. (28.9Kb)
  • Close-up of Brel & Kjr shaker / base / structure connection. (40.8Kb)

  • Marker Movie of base excitation of multi-level structure...
    This is in progress.

    Marker Companies providing equipment and support for this work...
  • Quanser Consulting Advanced Teaching Systems
  • Brel & Kjr Sound & Vibration
  • PCB Piezotronics

    Go to Quanser Homepage Go to WinCon Homepage Go to Brel & Kjr Sound & Vibration Homepage Go to PCB Piezotronics Homepage

  • Marker Site Info...
  • This site was last updated on July 29, 1999 and is maintained by:
    Jeffrey T. Shimmel
    Clarkson University
    Department of MAE
    P.O. Box 5725
    Potsdam, NY 13699-5725

  • Questions and comments can be mailed to shimmejt@clarkson.edu

  • Go to The Main Homepage of Jeffrey T. Shimmel - there is a link to return here.

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  • Questions and comments can be mailed to shimmejt@clarkson.edu

  • Go to The Main Homepage of Jeffrey T. Shimmel - there is a link to return here.