Modeling and Robust Continuous TSM Control for an Inertially Stabilized Platform With Couplings

Inertially stabilized platforms (ISPs), typically involving two or three axis gimbal, are extensively utilized to achieve accurate tracking of optical axis regardless of vehicle motion or vibration. Due to the complex nonlinearities induced by cross-couplings, parameter uncertainties, and external disturbances, high-performance control for ISPs is always a challenging task for practical applications, especially when the dynamic mass imbalance exists. In this brief, the situation that the mass distribution of an ISP is nonsymmetrical with respect to the mass center is emphatically analyzed, where the couplings are modeled and resolved into the known and unknown parts. To cope with the unmeasured states as well as the uncertainties composed of unknown couplings and remaining dynamics that are unmodeled, a higher order sliding mode observer (HOSMO) is developed for both the states and the lumped uncertainties estimation. By incorporating the estimated information, a robust continuous terminal sliding mode (TSM) control law is synthesized to admit the desired inertial angular rates tracking in finite time without offset. The validity of the presented control approach is demonstrated by experimental studies.