| Inertial stabilization of a sensor (such as EO, IR, SAR, or laser) is important in UAV applications, for example, to satisfactorily carry out certain sensor functions, image processing, or target tracking. Basic stabilization is usually accomplished by suspending the sensors in a two-axis gimbal system, with the sensors on the inner gimbal.Generally the gimbal system attenuates disturbances and makes the gimbal rotate following a certain rate command by a controller. In this paper we can only think of the fundamental disturbances that are caused by basic properties of the gimbal system.At first, this paper makes an instruction of the configuration and development of gimbal system all over the world, then mainly concentrates on the study of the two-axis yaw-pitch gimbal configuration and discusses kinematic equations and dynamical models of the two-axis yaw-pitch gimbal system. After that, this paper largely focuses on comparing the precision of target positions gotten by both direct and indirect control modes.There are direct and indirect control modes classified by where the input signals of the controller gains. These signals are directly gained from inertial sensors mounted on the two-axis gimbal system in direct mode, and indirectly from INS mounted on fuselage body in indirect mode. Based on principles of photogrammetry, this paper compares position error gotten by both direct and indirect control modes. Both theoretical and MATLAB simulation results are presented.At last, it explains how to calculate target positions based on four common points without locating in the same line in each of three different images obtained by camera which is rigidly mounted on the fuselage body of UAV when UAV lies in noncollinear positions and gives position error charts using Monte Carlo simulation. Besides, this paper makes an analysis of several contributors to the position error in this simulation and deduces how to use Monte Carlo for the two-axis gimbal system. |
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