In order to track maneuvering targets fast and accurately

an active disturbance rejection controller for electro-optical tracking servo system is presented and its work principle is investigated. Based on structure analysis of a certain system

the target velocity is contributed to exterior unknown disturbance and the system parameter change is looked as interior unknown disturbance. The extend state observer and tracking differentiator are used to estimate the disturbance accurately with the input and output information of system response

then the controller can compensate the disturbance furthest. Experimental results indicate that the system can fast track maneuvering targets at maximal 40mrad/s angular velocity and maximal 8mrad/s2 angular acceleration while the maximal tracking error less than 0.1mrad and the maximum overshoot less than 10%

and it has good robust performance. Without useing the sensor to measure the target state

it can satisfy the system requirements with a simple structure.