Stabilization loop design on direct drive gimbaled platform with low stiffness and heavy inertia

The fundamental role of stabilization loop in seeker application is to precisely follow the angular rate command which is proportional to the antenna bore-sight error during the target tracking. In order to achieve this requirement, it is prerequisite to highly isolate the gimbaled antenna from the missile body motion due to the maneuvering or low frequency vibration during flight. However, the isolation ratio and stability margin of stabilization loop adopting the gimbaled platform with both low stiffness and heavy inertia are limited by mechanical characteristic such as low resonance frequency and its high magnitude. Therefore, a multi-mass model, which can accurately presents the frequency behavior of the gimbaled platform, is indispensable to design of an optimal stabilization controller. In this paper, a pragmatic three-mass model for the direct-drive gimbaled platform from the motor to the antenna is introduced, and also the PI²L controller that produces both the high gain at low frequency and high stability margins by combining a PI² controller with lead compensator is presented. In the end, the performance and the stability of designed stabilization loop are demonstrated using simulation and experiment results in both frequency and time domain.