Omar Kassim Ariff

Differential Geometric Guidance Based on the Involute of the Target's Trajectory

This paper presents a novel approach to missile guidance using the differential geometry of curves and not relying on the line of sight information. The target’s trajectory is treated as a smooth curve of known curvature and the new algorithm is based on the involute of the target’s curve. The missile’s trajectory uses the concept of virtual target to generate the correct involute trace. It is shown that the missile is either on the trace immediately or may be able to reach it through an alignment procedure. In general, following the trace requires a three-dimensional maneuver in which the missile flies above the target’s tangent plane. The projection of the three-dimensional trajectory onto the tangent plane coincides with the involute trace, but is traversed in the time-to-go, thus resulting in the intercept. Two air-to-air scenarios of point masses are considered for a maneuvering target of the F-16 fighter class: 1) a two-dimensional engagement with target executing a constant g turn; 2) a three-dimensional engagement with target executing a barrel-roll maneuver. Perfect target information is assumed in simulations. In the first case, intercepts occur both for the involute law and proportional-navigation (PN) guidance; PN based intercepts occur quicker, but the involute-based trajectories are more difficult to evade and always result in a side impact. In the second case, PN fails to intercept the target, while the involute law is successful.

Waypoint Navigation of Small-Scale UAV incorporating Dynamic Soaring

The latest attempts at improving small scale autonomously guided Uninhabited Aerial Vehicles (UAVs) have concentrated around the increase of range and speed. One of these ways is to incorporate dynamic slope soaring manoeuvres as part of the flight path. This is in contrast to most conventional path-planning algorithms where waypoint guidance is merged with terrain avoidance or contour following capability. Additionally, current trajectory optimization techniques are iterative and so have a considerable computational load. The proposed algorithm is based on Dubins curves, and is therefore optimal by definition. Being non-iterative, it is comparatively a more efficient algorithm. Hence, a key advantage of the proposed technique is that the desired trajectory is generated quickly in real time with minimum computational load while satisfying the spatial constraints of dynamic slope soaring.

Aerodynamic Interference Correction Methods Case: Subsonic Closed Wind Tunnels

The approach to problems of wall interference in wind tunnel testing is generally based on the so-called classical method, which covers the wall interference experienced by a simple small model or the neo-classical method that contains some improvements as such that it can be applied to larger models. Both methods are analytical techniques offering solutions of the subsonic potential equation of the wall interference flow field. Since an accurate description of wind tunnel test data is only possible if the wall interference phenomena are fully understood, uncounted subsequent efforts have been spent by many researchers to improve the limitation of the classical methods by applying new techniques and advanced methods. However, the problem of wall interference has remained a lasting concern to aerodynamicists and it continues to be a field of active research until the present. The main objective of this paper is to present an improved classical method of the wall interference assessment in rectangular subsonic wind tunnel with solid-walls.

Impact of Eurycoma longifolia extract on DNA integrity, lipid peroxidation, and functional parameters in chilled and cryopreserved bull sperm

This study aims to assess the effect of Eurycoma longifolia aqueous extract on chilled and cryopreserved quality of bull sperm. Semen samples were obtained from four Simmental-Brangus. Each sample was divided into two fractions: the first fraction was used for chilling the semen, and the second fraction was used for the freezing process. Both fractions were extended with Tris-egg yolk extender supplemented with 0.0, 0.25, 0.5, 1.0, 2.5, 5.0, and 7.5 mg/ml Eurycoma longifolia aqueous extract. The diluted chilled fraction was chilled at 5 °C for 6 days, whereas the frozen-thawed fraction was frozen in liquid nitrogen. Data revealed that 1 mg/ml E. longifolia aqueous extract yielded significantly (p < .05) higher sperm motility, morphology, viability, and sperm membrane integrity compared with the control group and other treated groups in chilled semen evaluation. For cryopreserved sperm, a significant difference (p < .05) in sperm motility, viability, sperm membrane integrity, DNA integrity, and lipid peroxidation was observed between 5 mg/ml E. longifolia aqueous extract and other treated and control groups. However, no significant difference in the percentage of sperm exhibiting normal sperm morphology was observed among the groups. In conclusion, the addition of 0.25 and 1 mg/ml E. langifolia extract to chilled semen and 5 mg/ml E. longifolia aqueous extract to cryopreserved sperm into Tris-egg yolk extender helps in maintaining superior quality of bull spermatozoa during chilling and freezing.

Flight Data Monitoring/Tracker System for Search and Rescue Mission

Traditionally, Kalman Filter is used for the purpose of mixing several input signals and extracting a more reliable output, which greatly benefits aircraft navigation. This paper considers a fusion of four sensor systems: Global Positioning System (GPS), accelerometer, gyroscope and magnetometer. The resultant device, known as Starfish Main Tracking Unit (MTU), is a Flight Data Monitoring (FDM) / Tracking System equipment that uses General Packet Radio Service (GPRS) / Iridium / ICS (Internet Communications Services), which provides low cost telemetry as well as multiple solutions for global flight following and flight data transfer between aircraft and ground. Users from ground are able to monitor their fleet, configure their systems and also generate various flight reports from a single web-based interface, named the Starfish Fleet Management system. This developed system complements the Black Box by downloading limited aircraft data to the ground, provides real time tracking and assist in Search and Rescue (SAR) mission.

Autonomous Aerial Hard Docking of Fixed and Rotary Wing UAVs: Task Assessment and Solution Architecture

This paper covers exploratory efforts that attempt to address limitations and restrictions in the operating envelope of UAVs, and proposes a conceptual solution to the problem. UAVs, like aircraft, can be categorized into two main types: fixed wing and rotary wing. A fixed wing UAV flies using wings that generate lift caused by the vehicle’s forward airspeed and the shape of the wings. The greatest advantage of fixed wing UAVs obtained from utilizing aerodynamic lift is its long range and high endurance performance. However, this primary advantage comes from the fact that most fixed wing UAVs have wings that are of a high aspect ratio, which becomes a liability in confined operating conditions. An autonomous aerial hard docking system is proposed as a system that manages to enable different UAV platforms to have operational envelopes which far exceed the operational envelopes of the constituent UAV platforms. The paper outlines necessary subsystems that need to exist for autonomous aerial hard docking capability. It presents practical requirements of the various constituent subsystems, namely the guidance and navigation subsystem, the grasping subsystem and the damping subsystem. For each of the subsystems, the challenges which have to be overcome to ensure the effectiveness of the complete system are examined. It further elaborates the testing, investigation and development steps that need to be implemented to realize this capability. It ends by elaborating on the work already underway and future development plans. Note that this paper presents a conceptual logical and architectural solution, and as such detailed analysis findings are inappropriate and premature.

Computational Approach in Sizing of Pulsejet Engine

Research in pulsejet has intensified recently due to its design simplicity that can be developed into efficient small scale propulsive units for new applications such as UAVs and Unmanned Combat Vehicles (UCAV). A major obstacle for its development is low efficiency of the engine. The objective of this research is to investigate the possibility of using pulsejet in certain applications where the pulsejet can trade its low efficiency with low cost, simple design, and light weight. Numerical analysis is used for analysing the pulsejet engine design. The main results drawn from this research is in increasing efficiency and improving performance of engine by improving size of engine, especially diameter of combustion chamber. The computed results show good resemblance with published data.

Investigation into Air Interception Guidance Algorithms for Autonomous Aerial Hard Docking of Dissimilar Platforms

Autonomous aerial hard docking is the process where an aircraft approaches and forms a rigid connection with another aircraft. After the docking process is complete, it is not necessary for the lift and propulsion system of the docked aircraft to be operating. Docking allows the larger aircraft to carry the small aircraft outside its airframe, thereby extending the range of endurance of the smaller aircraft. In this paper, we investigate specific scenario where docking occurs between a rotary wing aircraft and a fixed wing aircraft. To perform the above procedure, a guidance system on each platform has to ensure interception while satisfying the primary interception condition of velocity vector co-linearity at the moment of intercept of the two trajectories or flight paths. Pursuit guidance and proportional navigation were assessed as candidates for further development for the terminal docking phase. Since the platforms are in quasi-perfect knowledge of each other, the pursuer evader scenario is replaced by the pursuer-pursuer scenario. The novelty of this work lies in the formulation of terminal constraints, as well as the findings obtained. This paper concludes that contrary to the missile guidance scenario, pursuit based guidance laws provide superior baseline laws from which AAHD guidance and navigation laws can be developed.

Three dimensional path planning algorithm for small UAVs incorporating existing dynamic soaring heuristics

An area under consideration of improving the mission effectiveness of small-scale, autonomous Uninhabited Aerial Vehicles (UAVs) has been the increase of speed. One method is to incorporate dynamic slope soaring maneuvers as part of the flight path during waypoint navigation. Research into autonomous dynamic soaring capability in small-scale UAVs began with selecting a suitable maneuver heuristic. The output from the heuristic model has then been used to formulate a non-iterative trajectory forming algorithm. By utilizing Dubin’s curves, a viable trajectory can be generated between the exit point of the dynamic soaring maneuver and the next waypoint. The result is a complete, easily implemented three-dimensional autonomous dynamic soaring capability.

Comparative Study on Aircraft Landing Instruments: Accuracies and Limitations

A normal aircraft flight includes taxi, takeoff, climb, cruise, descent, precision approach and finally landing. This study focuses on landing where the aircraft returns to the ground safely. In low visibility conditions, when pilots are unable to see the runway, the aircraft can always be diverted to another airport. However, low visibility can also affect all airports in the vicinity, forcing aircrafts to land in low visibility conditions depending on Instrument Flight Rules (IFR). Many countries have employed the landing systems because of inaccuracy, unreliability and dependency of Visual Flight Rules (VFR). In this paper, aircraft landing systems accuracies and limitations will be studied and compared for the purpose of assessing the best possible system currently available that can be achieved and implemented.