Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Seeker Based Optimal Guidance Law, A Few Issues

Abstract: Optimal Guidance Law (OGL) dynamically eliminates guidance time constant over homing duration and improves miss distance compared to conventional PN/APN guidance with accurate estimation of time-togo and target acceleration. In other words OGL attempts to make guidance system with time lag to appear as zero-lag guidance system over duration of homing by computing commanded acceleration on the basis of correct information of system dynamics, target maneuver and time-to-go. Due to un-modeled part of system dynamics such as body rate coupling, radome error coupling among others, OGL behaves unsatisfactorily when applied to Homing Guidance System with RF Seeker even when time-to-go & target maneuver are estimated accurately. If Inner Guidance Loop (IGL) is designed on basis of stability condition, some canonical form of guidance will give rise to unstable IGL. For normal PN/APN based system, a slightly modified formula guidance loop design based on minimum stability margin is presented. Moreover for sensitive scheme like OGL, some extra margin is required for guidance system to perform satisfactorily. In this paper, Zarchan’s formula of just stable IGL is modified for minimum control margin of IGL. An approximate measure of extra guidance time constant required for RF Seeker based OGL is also presented. Moreover IGL transfer function is derived and analyzed for OGL law. It is found that while stability of IGL for OGL based homing guidance with time constant selected based on stability margin formula of PN/APN based homing loop for 3 ' = N , is nearly retained; miss distance vs. flight time curves show oscillatory behavior because of un-modeled dynamics. One way to overcome this effect is to have longer range RF seeker or more stringent radome slope error specification. It is also shown that if time constants for OGL is selected with stability margin formula based on higher navigation gain, somewhat longer seeker range will assure guidance performance without making radome slope specification too stringent to be peacticable. Obviously, OGL based law can be easily applied to IR seeker based system as radome slope error is not present.

Damage Assessment Software Program

Abstract: The software package described here deals with the assessment of damage inflicted by missiles carrying pre-fragmented, bomblet, incendiary, runway-denial penetration submunition (RDPS), smart munition, and terminallyguided submunition warhead. The targets to be neutralised could be static, semistatic or mobile, like runways,bridges, bunkers, armoured tanks, soft-skinned vehicles, and personnel. This is graphical user interface(GUI)-based software, where the user can specify the target dimensions, target types, the number of missiles, its aimpoint, the type of warhead and the mode of operation. The software gives the number of targets that have beenneutralised effectively, as the output. This GUI-based software has been developed using Microsoft Visual Basic,Version 6.0. Defence Science Journal, 2008, 58(6), pp.745 -751 , DOI:http://dx.doi.org/10.14429/dsj.58.1702

Evaluation of defects in axisymmetric composite structures by thermography

Abstract: Thermography has been developed to evaluate delaminations, voids, missing layers and cloth joints in axisymmetric composite structures made by filament winding and hand lay-up techniques. The composite structures were made of carbon/epoxy, carbon/phenolic, carbon/polyimide and high silica glass/phenolic. Thermography has been found to be simple, fast, very effective and reliable to locate these defects.