Tested self-reliant, adaptive technologies that can detect problems with ISS hardware and correct those problems as needed. These technologies decreased the effects of vibration in ISS allowing engineers to design future spacecraft and facilities with lightweight, inexpensive materials without sacrificing the stability demanded by sensitive payloads.Principal Investigator(s)
United States Department of Defense Space Test Program, Johnson Space Center, Houston, TX, United States
Air Force Research Laboratory, Albuquerque, NM, United States
Langley Research Center, Hampton, VA, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Department of Defense (DoD) - RetiredISS Expedition Duration:
November 2000 - August 2001
1,2Previous ISS Missions
The Middeck Active Control Experiment-II (MACE-II) will allow engineers to design future spacecraft and facilities with lightweight, inexpensive structures and materials without sacrificing the stability demanded by sensitive payloads. MACE-II, the first hands-on experiment on board station, consists of two basic parts designed to detect and compensate for vibrations. The multi-body platform (MBP) test article, which is the structure undergoing tests, has four 1-inch-diameter struts connected to five nodes. It is loosely tethered in the aisle between racks during operations and is stowed between operations. The entire platform has 20 separate sensors that monitor vibration. The experiment support module (ESM) is a self-contained computer with a power interface to the EXPRESS rack and an umbilical connection to the MBP.
During experiments scientists used a gimbal on the MBP to create a disturbance at one end of the platform. The ESM detected these movements and, using an adaptable set of algorithms, calculated the opposing forces to be applied at the opposite gimbal, thereby stabilizing the platform. The algorithms could be adapted to changes due to moving parts, variations in temperature, and normal wear and tear on mechanical systems.
A collaborating team at MIT planned to study how control systems such as that used for MACE-II can be applied to hardware and systems that change over time, such as telescopes, antennas, and robotic arms that must be moved to perform specific duties.
MACE-II also tested self-reliant, adaptive technologies that could detect problems with ISS hardware and correct those problems as needed. This would reduce the amount of crew and ground-based personnel time required to monitor and repair Station hardware. This technique is also critical for control of large flexible structures that must perform precision pointing and tracking missions.Earth Applications
Autonomous adaptive control technology demonstrated by MACE-II can be used in any vehicle that must negotiate turbulent airstreams and atmospheric changes. It can be used to develop smart, problem-solving auto pilots for commercial jets or better guidance and pointing systems for military aircraft.
Bill Shepherd, who operated MACE-II during Expedition 1, and Susan Helms, who took over the operation for Expedition 2, received preliminary training at Johnson Space Center and additional computer-based training while on Station. Power for MACE-II was supplied by EXPRESS rack.Operational Protocols
MACE-II operations were carried out in twelve 4- to 8-hour sessions. Data downlink and control uplink occurred between sessions. On July 30, 2001, the Expedition 2 crew deactivated and stowed MACE-II for its return on STS-105.
MACE-II provided data autonomously (no human intervention or prior knowledge of the system), decreasing the effects of vibration in moving structures in space. Algorithms were developed to control mechanical systems in real time using only information from on-board sensors and actuators to respond to changes in the system. The system was able to reduce unwanted vibrations without human intervention once it was turned on. These algorithms were able to "adapt" whenever they sensed changes in vibration or the loss of a sensor or actuator.
Fourteen test protocols were completed during Expedition 1, and an additional 62 test protocols were completed during Expedition 2. The MACE-II unit, which was returned on shuttle flight STS-105, successfully completed all its experiment objectives associated with the AFRL Science Team while on station. On orbit they demonstrated a decrease in vibration by a factor of ten while the system was under control. They then showed that their system could adapt to failure of a primary actuator on the system and still decrease vibration by a factor of six.
However, due to data downlink constraints, the MIT Science Team was unable to meet its science objectives. The MIT team required downlink of specific on-orbit tests to build its control algorithms. By the time data were provided to the university, there was insufficient time to uplink the commands to run the critical experiments. (Evans, et al. 2009)
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