Showing papers by "Defence Research and Development Laboratory published in 1997"

Performance Evaluation of Rotary EDM by Experimental design Technique

Abstract: This paper presents an experimental design to study the performance of rotary electro-discharge machining (EDM). Scientific investigations have been carried out to find the effect of various EDM parameters. Titanimn alloy and die steel workpieces were machined with copper-tungsten tool electrode. The response surface technique has been adopted to compare the performance of rotary EDM, since such technological surfaces serve as an objective criteria to compare EDM systems. Moreover, such a surface and its response function serve as a mathematical model of the process. The analysis of the results was based on standard statistical techniques. The response surfaces and the corresponding response functions were determined for the machining indices for metal removal rate, surface finish, micro-hardness, etc. All the calculations were carried out through a computer programme specially developed for this purpose."

Synthetic Aperture Radar : A Focus on Current Problems.

Abstract: Synthetic aperture radar (SAR) is a powerful tool for mapping and remote sensing. The theory and operation of SAR have seen a period of intense activity in recent years. This paper attempts to review some of the more advanced topics studied in connection with madern SAR systems based on digital processing . Following a brief review of the principles involved in the operation of SAR, attention is focussed on special topics such as advanced SAR modelling and ffocussing techniques, in particular clutterlock and autofocus, Doppler centroid (DC) estimation methods involving seismic migration technique, moving target, biststic radar imaging , effects of system nonlinearities,etc.

Anukalpana 2.0: A Performance Evaluation Software Package for Akash Surface to Air Missile System

Abstract: : "An air defence system is a complex dynamic system comprising sensors, control centres, launchers and missiles. Practical evaluation of such a complex system is almost impossible and very expensive. Further, during development of the system, there is a necessity to evaluate certain design characteristics before it is implemented. Consequently, need arises for a comprehensive simulation package which will simulate various subsystems of the air defence weapon system, so that performance of the system can be evaluated. With the above objectives in mind, a software package, called Anukalpana 2.0, has been developed. The first version of the package was developed at the Indian Institute of Science, Bangalore. This program has been subsequently updated. The main objectives of this package are: (i) evaluation of the performance of Akash air defence system and other similar air defence systems against any specified aerial threat, (ii) investigation of effectiveness of the deployment tactics and operational logic employed at the firing batteries and refining them, (iii) provision of aid for refining standard operating procedures (SOPs) for the multitarget defence, and (iv) exploring the possibility of using it as a user training tool at the level of Air Defence Commanders. The design specification and the simulation/modelling philosophy adopted for the development of this package are discussed at length. Since Akash air defence system has many probabilistic events, Monte Carlo method of simulation is used for both threat and defence. Implementation details of the package are discussed in brief. These include: data flow diagrams and interface details. Analysis of results for certain input cases is also covered."

Quality Engineering in Aerospace Technologies : A Review

Abstract: Quality assurance and reliability have assumed paramount importance in aerospace technologies due to stringent requirement of weight-to-strength considerations and the need for highly reliable systems. The techniques of inspection and testing have given way to the use of sophisticated reliability engineering, failure mode effects & criticality analysis, deign of experiments and total quality management concepts. The role of failure analysis to improve the quality on a continuous basis has been realised by all engaged in aerospace technologies. The number of simulation runs help to build up quality in design and development phase and obviate the need for extensive hardware testing. The techniques of metrology and nondestructive testing have been upgraded considerably during the last decade. Most of the manufacturing techniques, now being computer-aided, give consistent production and better quality.

On a New Six Degree of Freedom Modelling Method for Homing Missiles and its Application for Design/Analysis

Abstract: Development of an accurate six-degree-of-freedom (6-DOF) simulation model for homing missiles incorporating seeker servosystem detailed modelling is reported. A new modelling concept for seeker servosystem simulation, the Newtonian equivalent model (NEM) has been evolved, where body motion coupling is modelled through forces and moments transformed to the seeker. The NEM-based modelling of seeker head and its integration in 6-DOF has been discussed. In the presence of body coupling, the simulation model for seeker tracking or pointing error, gimbal angles and inertial line of sight (LOS) rates as measured by the seeker mounted rate gyros have been obtained through the new modelling method. A novel method of obtaining optimum pitch and yaw LOS rates for proportional navigation (PN) guidance mechanisation is formulated based on synthesised sight line rates measured in the seeker inner gimbal axis. This new method has been validated through simulation studies using the 6-DOF model developed and by comparing the results with those obtained by the conventional method of generating LOS rates for PN guidance. Other important applications of the 6-DOF model discussed are guidance and control design validation/tuning seeker feedforward compensation design tuning of switchover point from open-loop to closed-loop PN guidance. Importance of the detailed 6-DOF simulation model as the ultimate performance evaluation tool for the weapon system in terms of both terminal performance and adequacy of seeker field of view, gimbal angle freedom, etc. has been brought out.