mahsa javaheripour

Proportional navigation is one of the most widely used methods in guiding flying objects. This method requires the rotation rate of the line between the interceptor and the target to calculate the guidance command. For a variety of reasons, including cost savings, simple sensors are used to measure tracking information, including line of sight angle. Therefore, some non-measurable information such as the angular velocity of the line of sight must be estimated using mathematical equations. Due to the noise and other problems, the use of derivatives is not desirable in this situation. Therefore, in this paper, an extended nonlinear observer is used to estimate the angular velocity of the line. Due to the nonlinear dynamics of the intercepting of flying objects, a nonlinear type of observer has been selected. By performing a computer simulation, the correct operation of the proposed observer is shown.

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.

The line of sight (LOS) rate is a parameter that is needed to calculate the acceleration applied to missiles by the proportional guidance laws in order to hit the target. This rate is usually measured using gimbaled seekers. However, if the type of missile seeker be strap down, the LOS rate must be calculated from deriving the missile's seeker output angles or estimation methodes. The derivation method is not desirable due to the noisy output of the seekers and low pass filters are needed to achieve an acceptable output, which will cause a lag in the guidance loop. In this paper, a discrete time extended state observers will be designed to estimate the LOS rate. The advantage of the time discontinuity of the observer is that issues related to the implementation of the observer on the processors, such as the choice of sampling time, considered from the design level and examined in computer simulation.