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Fact sheet number: FS-2001-03-52-MSFC
Release date: 03/01

Middeck Active Control Experiment-II

Experiment Name: Middeck Active Control Experiment-II

Mission: Launched on STS-106(2A.2B) and operations begun during Expedition One

Project Manager: R. Rory Ninneman of the Air Force Research Laboratory at Kirtland Air Force Base, N.M.


The Middeck Active Control Experiment Reflight, or MACE II, Program research will provide data on decreasing the effects of vibration in moving structures in space. This will allow future spacecraft to be designed with low-cost structures lighter in weight than those currently used, and still achieve performance requirements by actively decreasing the effects of vibration.

This research will allow future spacecraft to continue performing their missions as their subsystems degrade and fail, extending the life of a spacecraft.

Experiment Operations

The first active science experiment to fly aboard the International Space Station, MACE II is an on-orbit demonstration of advanced control technologies to suppress unwanted vibration.

Managed by the Air Force Research Laboratory Space Vehicles Directorate at Kirtland Air Force Base, N.M., the MACE II Program has two separate science teams, led by the Air Force Research Laboratory and the Massachusetts Institute of Technology at Cambridge, Mass, respectively.

The Air Force science team has developed algorithms - computer commands -- to control mechanical systems "on the fly," using only information from on-board sensors and actuators, reducing or eliminating unwanted vibrations without human intervention. These algorithms also can modify themselves or "adapt" whenever they sense changes. The MIT science team is investigating the control of systems whose characteristics change over time, or due to changes in their geometry, such as when an antenna is moved through a large angle from one position to another.

The MACE II flight hardware consists of two primary components. The structure to be tested is the Multibody Platform. Approximately 60 inches (152 centimeters) long, the platform is made of four struts less than 1 inch (2.5 centimeters) in diameter connected to five nodes. The two outermost nodes have two-axis gimbals, rotating parts that can swing up to 60 degrees. The center node has three reaction wheels mounted at 90-degree angles. The gimbals and the reaction wheels control the motion of the platform.

The platform contains 20 separate sensors to measure motion and vibration. The platform is connected to the Electronic Support Module, a self-contained control computer. The support module runs algorithms, called protocols, like programs on a personal computer. The support module reads data from the platform sensors, calculates the forces to be applied at each gimbal or reaction wheel to minimize vibration, and then sends commands back to the platform.

For these experiments, scientists create a disturbance at one end of the platform, using the two-axis gimbals. When the gimbals move, the entire platform will vibrate. But when the support module detects this and executes its algorithms, the gimbals on the opposite end of the platform should remain steady.

All data from the experiment are stored to removable hard drives for future analysis on the ground.

The Air Force team includes Planning Systems Inc. and Melbourne Controls Group of Melbourne, Fla.; Payload Systems Inc. of Cambridge, Mass.; the University of Michigan, Ann Arbor, Mich.; Virginia Polytechnic Institute, Blacksburg, Va.; and Sheet Dynamics Ltd. of Cincinnati.

The MIT team includes Lockheed Martin Space Systems Sunnyvale Operations, Sunnyvale, Calif.; Midé Technology Corporation of Cambridge, Mass.; and the NASA Langley Research Center in Hampton, Va.

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