NONLINEAR INDUCED DISTURBANCE REJECTION IN INERTIAL STABILIZATION SYSTEMS

A frequent problem in inertial stabilization control systems is the re jection of disturbances associated with moving components. Very often such disturbances are nonlinear and time varying. A prime example is t he relative motion of components within a gimbal; in this case, nonlin ear bearing friction induces a destabilizing torque from base motion t o the component being stabilized. This paper presents an linear quadra tic Gaussian (LQG) algorithm, based on a simple first-order linear sto chastic differential equation, for estimating and compensating in real time a particular class of disturbances that can be modeled as a plus or minus unknown slowly changing random value such as is characterize d by nonlinear Coulomb friction. Results of computer simulations testi ng the control algorithm are presented along with actual measurements from a laboratory brassboard system. The results reveal a noteworthy i mprovement in disturbance rejection as compared with a conventional pr oportional integral (PI) controller with notch filters.