说明：  In this paper, formation control ideas for multiple spacecraft using the virtual structure approach are presented. If there is no formation feedback from the spacecraft to the virtual structure, the spacecraft will get out of formation when the virtual structure moves too fast for the spacecraft to track due to spacecraft control saturation or the total system must sacriˉce convergence speed in order to keep the spacecraft in formation. The spacecraft may also get out of formation when the system is a® ected by internal or external disturbances. To overcome these drawbacks, an idea of introducing formation feedback from the spacecraft to the virtual structure is illustrated in detail. An application of these ideas to multiple spacecraft interferometers in deep space is given.