This paper presents a survey of ground experiments primarily conducted in the United States and U.S. facilities dedicated to the study of active control of flexible structures. The facilities are briefly described in terms of capability, configuration, size, and instruments. Topics on the experiments include vibration suppression, slewing control, and system identification. The experiments are listed in tables containing the experiment's name, the responsible organization, a brief description of the test article configuration, and the actuator/sensor devices used in the experiment. Selected experiments will be further discussed to help illustrate the control problems. Some of the test facilities dedicated to ground testing of large space structures are discussed in more detail, to give the reader a better appreciation of ground-testing work. Several research issues are mentioned, including real-time computer systems, test article suspension, and new actuator/sensor technology development. reliable performance for on-orbit construction, maintenance, experiment operations, etc. Permanently manned spacecraft operations will also bring in their own special needs, most notably the requirement to counter disturbances caused by human motions. These challenges are beyond the current state of the art in space structure design. It is envisioned that new design methods will be needed to tackle these challenges. Since complex, flexible space structures are new, they must be studied and validated via thorough ground testing, both in controlled laboratory environments and in realistic operating scenarios. With the increase in size, complexity, and capability, these future space systems will be proportionally more expensive and, thus, there will be an even greater incentive to ensure that these space systems operate as designed. Ground testing will signficantly contribute to this effort. Dr. Jer-Nan Juang is Principal Scientist of the Spacecraft Dynamics Branch, NASA Langley Research Center. He coordinates joint technical activities with other Langley and NASA organizations, other government agencies, and industry/universities on a national and international basis. He conducts personal analytical and experimental research in the fields of mechanical designs, controller designs, and system identification for control of flexible space structures including robotics. He is a Fellow of the American Astronautical Society and the
