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.

Damping in beams using viscoelastic layers

Abstract: Various types of sandwich beams with viscoelastic cores are currently used in aerospace and automotive industries, indicating the need for simple methods describing the dynamics of these complex st...

Radio Frequency Seeker Modelling and Seeker Filter Design

Abstract: Radio frequency seeker model, including receiver angle error noise modelling and filtering of noise from seeker measurement, is presented in this paper. The effects of eclipsing, radar cross section fluctuation, etc on seeker sight-line rate measurement are highlighted. The formulation for colour noise modelling of sight-line rate noise is derived based on the knowledge of seeker receiver angle error noise model. Two Kalman filter configurations for filtering of noise from seeker output have been considered in this paper, based on sight-line rate kinematics and noise characteristic. It has been observed from the simulation studies that sight-line rate signal varies slowly at higher interceptor-target ranges; with severe colour noise in sight line rate measurement, and therefore higher weightage for noise attenuation is beneficial in Kalman filter configuration. So, kinematic plus state augmentation for colour noise are considered for adequate filtering for higher interceptor-target ranges. Whereas for lower interceptor-target ranges, sight-line rate changes appreciably, which have been tracked by a simplified/modified spherical coordinate model, which uses knowledge of interceptor-target engagement dynamics. For both the filters, benefits of colour noise modelling and process model augmentation through coloured noise states, for filtering severe colour noise of seeker, has been demonstrated.

Realistic Pursuer Evader Engagement with Feedback Linearization Based Nonlinear Guidance Law

Abstract: In this paper realistic Six Degrees of Freedom simulation of a pursuer evader engagement during terminal guidance has been carried out using a class of nonlinear guidance law based on Feedback Linearization. This guidance law has been developed as a regulator problem based on nonlinear control theory where line of sight rate derivative along both yaw and pitch plane are made zero by taking line of sight angle and line of sight rate as output feedback. The line of sight angles and rates have been computed from noisy seeker measurements through a nonlinear state observer. The available seeker measurements are pursuer-evader relative range, relative rage rate, gimbal angles and line of sight rates along yaw and pitch plane in seeker inner gimbal frame. The present guidance law has been validated in presence of realistic non Gaussian and correlated seeker measurement noise, estimator, autopilot lag and highly time varying pursuer velocity during engagement. It is demonstrated through realistic Six Degrees of Freedom pursuer-evader engagement simulation in the presence of above constraints in a practical environment that the proposed guidance law is a viable option for intercepting maneuvering target with high heading error over the well known proportional navigation guidance law. This specific type of guidance law being not available in published literature, is claimed as quiet novel.