Middeck Active Control Experiment Reflight (MACE II) Program

Abstract

The Middeck Active Control Experiment Reflight (MACE II) Program* is an on-orbit demonstration of adaptive structural control technology. In recent years, there has been a significant interest in the use of adaptive methods for controlling structures in high precision aerospace applications. This is because adaptive methods offer the potential to autonomously adjust to system characteristics different from those modeled or seen in qualification testing. This is especially true of spacecraft, which are generally tested in a l-g environment. Despite extensive research, it remains extremely difficult to predict on-orbit O-g behavior. The original MACE flight program, conducted by NASA Langley and the Massachusetts Institute of Technology (MIT), experienced similar difficulties. The dynamics observed on orbit varied from those observed during ground qualification testing. The initial fixed gained controllers developed during ground testing were unstable. The controllers were redesigned during the mission based on on-orbit system identification measurements. The resulting redesigned controllers met the performance ~objectives of the mission. The MACE II technical objectives are to develop adaptive algorithms which will (1) greatly decease the need for modeling and ground testing to develop the controllers and (2) allow for autonomous reconfiguration of the control system to changing * This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States. dynamic characteristics and sensor/actuator failures. By decreasing modeling and testing requirements, lowering operations and maintenance activities that require human intervention, and increasing reliability; adaptive methods have the potential to significantly reduce cost and increase performance of these systems. The Air Force Research Laboratory (AFRL) is currently engaged in advancing adaptive control technologies for application to precision space systems. This paper gives brief historical review and lessons learned from previous AFRL structural control programs and an overview of MACE II program.