Line of Sight Rate Estimation Using Discrete-Time Sliding Mode Extended State Observer

Proportional Navigation is commonly used in the terminal phase of homing missiles. To implement this guidance law, it is necessary to measure or calculate Line of Sight (LOS) rate. It is usually necessary to use gimballed seekers to measure the LOS rate. However, if the system is equipped with a strapdown seeker, the LOS rate must be calculated from derivation or estimation methods. Because the signal measured by seekers usually contains noise, so deriving this signal requires a low pass filter that will cause the behavior changes in the measured variable. The issue in this paper is the design of a discrete time sliding mode extended state observer to estimate the LOS rate and evaluate it in the guidance loop. This is done by performing computer simulations. Implementing continuous time observers in processors has challenges such as sampling time selection and it is better to design the observer in discrete time form from the beginning so that its implementation issues can be considered from the design level and in computer simulations.