Defence Science Journal
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Life Cycle Assessment Based Analysis of Water Bottle Designs for Defence Application
Get PDFThis paper presents the successful implementation of the Life Cycle Assessment (LCA) approach for the sustainable development of a defence product. Alternative designs of this product are evaluated from the environmental burden perspective. The products considered are water bottles used by the armed forces in places like the Siachen glacier, where the environmental factors are of great concern. From the environmental degradation perspective, the suitability of three existing bottle types has been analysed using LCA and Life Cycle Impact Assessment (LCIA) approaches on SimaPro software for each of its components and the bottle as a whole. Using this software, uncertainty analysis has also been carried out by conducting a Monte Carlo simulation for a reasonable confidence level. The latest design was found to have the least environmental burden, being 82.62% less compared to the first design. To augment the environmental performance further, the best design was again reviewed by carrying out component level analysis to identify feasible alternative materials that would be functionally equivalent but with lower environmental impact. It suggested switching to lower impact material for the cap and cap cover for the proposed design. With the adoption of the changed material, the environmental performance improved by 10.61 % as compared to the best design and 84.46 % compared to the earliest design. 
Process Optimization and Design of an Automation Controller for a Multidisciplinary Combat Engineering System
Get PDFDesign of an automation controller for a “Electro-Hydro-Mechanical Object Laying System” is presented in this paper, which is a multidisciplinary equipment consisting of Electromechanical and Hydraulic Actuators and large number of sensors for process feedback. There are complex mechanisms and processes involved in this system, which are required to be operated/executed in sequential and parallel manner in real time. The operation of spatially distributed Electromechanical & Hydraulic actuators with feedbacks from multiple type of sensors are required to be synchronized for multiple activities at a faster rate along with safely handling of the objects. All the activities are automated with minimum human intervention to avoid risk to the crew. This paper mainly focuses on electronic controller hardware design for military environment and process optimization to achieve faster object laying rate
Secrecy of WSN Data Over Nakagami m Fading Channels with Selection Combining Diversity
Get PDFWe consider the security of wireless sensor network (WSN) data over Nakagami – m fading channels at the physical layer. A WSN in which the fusion center performs selection diversity has been considered for better quality reception. The links between the WSN node and fusion center are assumed to follow Nakagami-m fading distribution. Closed-form expressions for secrecy outage probability (SOP) are derived, and it is established that SOP analysis also leads to the analysis of the existence of secrecy as a special case of SOP. The analytical expressions have been validated through results from simulations. The analysis is valid for all positive real values of the fading parameter, m. The limits on the signal-to-noise ratio can be obtained to secure the transmitted data against eavesdropping with the required SOP and secrecy rate using the analysis presented in this paper
Closed Loop Vector Formulation in Eulers Complex Numbers for Multi Loop Planar Mechanisms With N bars A Novel Modeling Approach and Algorithm
Get PDFThis paper presents a novel iterative algorithm incorporated in a user-friendly GUI for modeling the kinematics of multiple looped N-bar closed-loop mechanisms. Past research works have used custom coding or expensive commercial software to analyze the mechanisms of specific applications. The proposed algorithm focuses on kinematics and offers a quick, easy-to-use, cost-effective solution to analyze a wide range of generic mechanisms, reducing the need for custom coding and lowering computational costs. The algorithm employs algebraic equations, such as solving complex closed-loop vector equations using the Euler form of complex numbers, to simulate and derive the unknowns necessary to characterise any generic closed-loop mechanism. The Python code implemented in the algorithm adapts to various scenarios by utilising available information on the position, velocity, and acceleration variables of the mechanisms. The simulation tool can display real-time color contour plots (RGB color scale) for linear and angular velocities and accelerations, simulate mechanisms with multiple loops and switch configurations, and find inverse mechanisms. The approach for solving multiple loop problems and the algorithm utilized to solve the configurations, methods, equations used and GUI features implementation are all described in this study. The case study considered for a four-bar mechanism indicates a strong agreement between the results obtained from the proposed kinematics-based simulator and ANSYS software. These results demonstrate the simulator’s effectiveness in providing low-cost and user-friendly simulation results for various generic mechanisms involving multiple interconnected loops
Analysis of the Effect of Circular Ring Baffles in Suppressor on Flow Field and Far Field Noise Levels at 9 mm Semi Automatic Pistol
Get PDFA firearm generates complex phenomena in muzzle flow and modelling the flow field around the projectile has great importance on high-intensity noise prediction. The negative effects of noise can be reduced using a suppressor which can be internally or externally attached to the barrel of a firearm. The purpose of this paper is to numerically and experimentally investigate the effect of the number and distance of circular ring baffles in the suppressor on the flow field and far field noise levels. Calculations were carried out in two-dimensional, axisymmetric, transient conditions and Ffowcs Williams and Hawkings acoustic analogy (FW-H) equations were solved to predict the far field noise. Nine cases including a gun without a suppressor, a suppressor without baffles, one, three, and five baffles which were placed at 20 mm intervals from the suppressor inlet, and one, three, five, seven, and nine baffles which were placed with equal intervals in the suppressor were simulated and compared; generations of noise during the shooting process were analyzed. The results showed that in the case without a suppressor, the peak sound pressure level was 156.1 dB at a 2.5 m distance, while this value decreased by nearly 7.6% in the case of the suppressor with seven baffles which has an average value of 144.2 dB. The results obtained here may provide a beneficial reference for predicting the muzzle noise and optimizing the number of baffles in the suppressor for small caliber gun systems
Effect of Twin Island Configuration on Airwake Aerodynamics over Generic Aircraft Carrier using CFD
Get PDFThe technological advancements have led to the evolution of numerous concepts in an aircraft carrier’s topdeck design, the twin island concept being the latest entrant. An aircraft carrier’s bluff body geometry presents many challenges to the pilot, landing on deck being the most critical. The present study aims to undertake a computational investigation of the aerodynamic analysis of a Twin Island GAC (Generic Aircraft Carrier) conceptualized vis- à-vis its base variant. The flow over the twin island GAC flight deck and downstream is analysed using various transverse planes perpendicular to the flow direction as detailed in the paper. Subsequently, a parametric study was undertaken for understanding the effects of longitudinal translations of the two islands with respect to the baseline GAC position. The results depict the advantage of certain variants of twin islands over a single island, and ~68 % reduction in turbulence is achieved along the glideslope by one of the variations which could aid in reducing pilot workload. The data can act as a catalyst for utilization and incorporation in future floating platform designs and further studies in this field
Effect of Gyroscopic Couple on Aircraft Landing Gear Shimmy
Get PDFThis article presents the effect of gyroscopic couples on the shimmy response of landing gear. The gyroscopic effect between the rotational motions of the aircraft’s longitudinal and vertical axes may be one of the causes of shimmy. The vertical load acting on the wheel axle plays a significant role in a tire’s dynamic characteristics, which may influence shimmy oscillation. So, vertical dynamics also need to be considered for shimmy analysis along with lateral and torsional modes. Suitable mathematical models are required to study the system’s shimmy oscillation and stability nature. The mathematical model was developed by introducing a gyroscopic couple with 5 degrees of freedom (DOF). A numeric analysis was made to investigate the influence of gyroscopic couples on the landing gear model. The simulation results of the model with and without gyroscopic couple are compared and the effect of each parameter on shimmy is studied
GPS Receiver Simplification for Low cost Applications and Multipath Mitigation Analysis on SDR based Re configurable Software Receiver
Get PDFMany modern position-based applications rely heavily on the Global Navigation Satellite System (GNSS). Most applications require precise position data obtained through sophisticated hardware with a high computational capacity in the receiver. Some cost-effective applications may not require precise position data and require less complex signal processing. The use of efficient hardware and signal processing techniques to reduce the overall cost of a GNSS receiver is an active research topic. This paper considers Global Positioning System (GPS) constellation and proposes two factors to reduce the receiver complexity: sampling frequency and the number of tracking channels. A Keysight GNSS signal generator to record GPS signals, a Software Defined Radio board and a software-based GPS receiver are used in the experimentation. The sampling frequencies are 40, 20, 10 and 5 MHz considered, and tracking channels are reduced from 12 to 6 and then 4. The increase of error in the receiver position with 6 and 4 satellites is considerably small, but the number of tracking channels and signal processing requirements are reduced considerably. The GPS signals are affected by many errors; one of the significant sources of error is multipath propagation. Three distinct GPS multipath scenarios are generated for four satellite signal combinations with the GNSS simulator for the receiver performance analysis. Three multipath mitigation techniques, namely Early Minus Late (EML), Narrow correlator (NC) and strobe correlator (SC) methods, are considered because of their simple structure and fewer signal processing requirements. The error reductions of three multipath scenarios are compared, and the SC method performs better in all three multipath scenarios
Human Error Management in Aviation Maintenance using Hybrid FMEA with a Novel Fuzzy Approach
Get PDFHuman errors significantly contribute to aviation accidents during aircraft maintenance. Therefore, managing human errors becomes a critical aspect of aviation maintenance. The existing literature has extensively analysed human errors. However, there is a gap in accurately identifying and prioritising critical human errors and effectively managing them to reduce incidents and accidents. This research work proposes a novel fuzzy approach for human error analysis using a hybrid FMEA with Fuzzy AHP-TOPSIS. We identified inadequate maintenance processes, attention/memory, inadequate documentation, inadequate supervision, judgement/decision-making, and knowledge/rule base as some of the critical human errors in aircraft maintenance. Based on these findings, we recommended practically implementable solutions at the organisational, workspace, and individual levels to mitigate human errors in aircraft maintenance
Selection of Combat Aircraft by Using Shannon Entropy and VIKOR Method
Get PDFThe selection of military defense equipment, especially fighter aircraft, has a bearing on the readiness ofthe Indian Air Force to defend the country’s independence. This study analyses a collection of alternative fighteraircraft that are linked to several choice factors using a multiple-criterion decision-making analysis technique. Tohandle such scenarios and make wise design judgements, a variety of criterion decision analysis techniques can beused. In this study, we assess fifth-generation fighter aircraft that incorporate significant 21st-century technologicaladvancements. These aircraft represent the state-of-the-art in fleet planning operations to 2022. These are generallyequipped with quick-moving airframes, highly integrated computer systems, superior avionics features, networkingwith other battlefield elements, situational awareness, command, control, and other communication capabilities.The study proposes a strategy for the selection of the fifth-generation combat aircraft for the National Air Force.Because of the problems, the Army needed an application that could assist with decision-making for combat selection systems. Solving the decision problem for evaluating fifteen military fighter alternatives in terms of nine decision criteria is the main objective of this work. We use the Shannon entropy and VIKOR model for the Air Force’s fleet program to evaluate military fighter aircraft suitability. The entropy technique is used to compute the weight of the criteria, and then the VIKOR technique has been used to rank the fighter aircraft