Stabilization of two-axis line-of-sight system using active disturbance rejection control

Inertially stabilized platforms are used in many places, including land, flying, and space applications. They can easily be found in drones, cameras, vehicles, helicopters, aircraft, and telescopes. They usually carry a payload such as a camera, laser range finder, or radar. A key parameter required for systems designed for targeting and tracking is the precision of the line-of-sight (LOS) stabilization. Sensors are needed to take measurements under conditions of internal and external interference. Base movement, friction, and other imperfections cause a change in the position of the LOS. The main task of the control system is to use an electric motor to keep the angular velocity of the payload measured by gyroscopes equal to zero. This paper presents a bottom-up approach to investigate the impact of single and coupled imperfections on the LOS performance and accuracy. Detailed analyses establish error budgeting for a two-axis, multi-rigid-body, gimbal LOS system. The process aims to specify the dominant sources of errors and the most significant risk areas, which may suggest potential improvements. The Active Disturbance Rejection Control (ADRC) strategy is used to isolate the LOS vector from the platform’s angular motion. The control quality of the method and its feasibility in dealing with combined errors are demonstrated through multiple simulation-based scenarios on a prototype platform.