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.

This paper presents a method for Line-of-Sight stabilization in submarine periscopes with respect to disturbances in the sea surface movements. These disturbances can cause unstable images taken by the periscope and give altered information from the targets that are located on the see surface, on the land, or in the air. To overcome this problem, an image stabilization method is required to geneRate reference signals for servomotors to remove the unwanted motions incurred on the image sequences. To drive the stabilization equations, basic rotation and homogeneous transformation matrices will be used. The stabilization equations will be derived for two different cases: 1) the range of target is known and 2) the range of target is unknown. In fact, these equations map the input space to the three-dimensional output space. The input space consists of the deviation angles of the periscope platform, the optional target range, which can be measured or given by the operator (optional data), and some desired operator information. The output space consists of three reference signals for three servomotors inside the persicope. The proposed method is implemented on an experimental periscope, mounted on a moving platform, which simulates the sea surface movements. The experimental results show good performance of the proposed method against sea surface movements.

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.

A generalized three-dimensional Line-of-Sight guidance with lead angle (GLOS) is presented for maneuvering targets. In the proposed guidance law, we define a desired Line-of-Sight (LOS) from the tracker by taking the target future maneuvers into account. Because of the limitation of the tracker field-of-view (FOV), the lead angles in the azimuth and elevation channels must be fractions of the azimuth and elevation angles for straight collision trajectory. Simulation results show that GLOS has better performance, i.e., lower miss distance and total control effort, than the conventional LOS guidance with lead angle.

In this paper, an explicit optimal Line-of-Sight guidance law for second-order binomial control systems is derived in closed-loop without acceleration limit. The problem geometry is assumed in one dimension and the final time and final position are fixed. The formulation is normalized in three forms to give more inSight into the design and performance analysis of the guidance law. The computational burden of the guidance law is reasonable for today’s microprocessors; however curve fitting or look-up table may be used for the implementation of the second-order optimal guidance law. The performance of the second-order optimal guidance law is compared in normalized forms with zero-lag and first-order optimal guidance laws using third-, fourth-, and sixth-order binomial control systems with/without acceleration limit. Moreover, the effect of the final time, the equivalent time constant of the vehicle control system, the vehicle-to-target Line-of-Sight weighting factor in cost function, and acceleration limit are investigated. Normalized miss distance analysis shows that the miss distance of the secondorder guidance law is smaller than the two mentioned schemes for small total flight times, especially with large maneuvering capability.

This paper suggests modified proportional navigation (PN) with a weighted combination of Linear acceleration and Line-of-Sight (LOS) acceleration feedback. For this purpose, a comprehensive miss distance analysis is carried out for PN with Linear acceleration feedback and PN with LOS acceleration feedback using a fifth-order binomial guidance and control system. The miss distance (MD) due to initial heading error, target acceleration, and seeker noise are sepaRately analyzed. A modified PN with acceleration feedback using variable gains is suggested based on MD analysis for infrared seekers as a special case. The PN stRategies are compared using an equivalent effective navigation ratio, defined using the LOS Rate profile solution. In addition, the first-order optimal guidance law is converted into PN with PD block with variable gains.