Many physical systems are inherently time-varying in nature. When these systems are linearized around a trajectory, generally, the resulting system is Linear Time-Varying (LTV). LTV systems describe an important class of linear systems and can be thought of as a natural extension of LTI systems. However, it is well known that, unlike LTI systems, the eigenvalues of an LTV system do not determine its stability. In this paper, the stability conditions for a class of LTV systems are derived. This class is composed of piecewise LTV systems, i.e. LTV systems that are piecewise linear in time. Sufficient conditions of stability are derived in the form of linear matrix inequalities (LMIs) by using the Lyapunov stability criterion. The feasibility of LMIs guarantees the stability of a given piecewise LTV system. Furthermore, uncertain piecewise LTV systems with scalar parametric uncertainty are also considered. Sufficient conditions for robust stability of this case are also presented, which come out to be quasi-LMIs, which can be optimized using a bisection algorithm to find the bounds of uncertainty for which the system is stable. The proposed method is applied to the problem of pitch angle control of a space launch vehicle, and the results are presented.
A Vertical Takeoff and Landing (VTOL) aircraft is capable of short/vertical takeoffs and landings, thus eliminating the requirement of long runways. This feature makes them suitable for a broader variety of missions, generally not achievable by a traditional aircraft. The dynamics of the VTOL aircraft in the vertical plane has been used as a benchmark problem to demonstrate the effectiveness of different nonlinear control techniques, mainly due to being highly coupled and non-minimum phase. This paper presents the design of an inverse optimal control for a simplified VTOL aircraft model. The proposed control law is based on a Control Lyapunov Function (CLF) which exploits the normal form typically used for control design through feedback linearization. The suggested control law is compared with dynamic feedback linearization based control law and a comparison is drawn based on their efficacy and robustness.
Quantum cryptography is a practical method of secret communication that guarantees the foolproof secrecy. This paper presents the simulation for implementation of a Quantum Key Distribution (QKD) protocol BB84, the pioneering, and most basic and fundamental protocol. We use the quantum computing platform developed by IBM named as Qiskit for the simulation of the BB84 protocol, implementing it with and without an Eve eavesdropper for studying the relative outcomes. Recently, Qiskit is globally very popular for quantum simulations because it provide us the opportunity to simulate quantum logic circuit on classical computer as well as real quantum computers owned by IBM. As per our best knowledge, there is no any proposal published for quantum circuit by anyone for BB84 QKD. We performed experimentation on local as well as cloud simulators: 1) The "qasm_simulator" was used as local machine simulator, and 2) The "ibmqx2" simulator was used as IBM cloud quantum simulator. The outcome of local as well as IBM simulator with and without an eavesdropper, between the two parties involved in key exchange were recorded and presented in the results section.
In this paper, the problem is to design and simulate an Electric Propulsion System (EPS) for Unmanned Underwater Vehicle (UUV) by doing real-time simulations using MATLAB GUI that incorporates the analysis of change in speed with respect to physical parameters of the vehicle such as drag force, power, and thrust force to be capable of doing desired missions as same as Remus-600 (UUV). For proposed EPS in which the batteries are the main power source, the electric motor will then be the driving foundation and propellers will be the driven equipment. The EPS is designed based on a study of various existing UUV around the world. MATLAB GUI based simulations has been carried out using different physical design parameters such as, current drawn from the battery, endurance, drag, thrust, RPM, etc. Finally, proposed EPS ensures the vital abilities to be more energy efficient along with high speed and enough endurance.
The COVID-19 coronavirus outbreak in recent years has become a pandemic across the globe. Which has a significant risk on human health causing nearly 5 million deaths worldwide. Recent research has shown that aerosol transmission is the main cause of COVID-19 virus spread. Sanitization of hands or the 6 feet at a recommended distance by WHO can reduce the virus but people with greater occupancy are needed to be addressed. A vulnerable place for disease infection is a hospital room where many patients have been infected with COVID-19. Transmission of the virus is the main cause of COVID-19 spread. Thus, understanding the flow physics of virus transmission through CFD analysis is necessary. A Euler-Lagrangian model is used to investigate aerosol transmission from an infected person inside a hospital room under the effect of ventilation. Ventilation plays a great role in the removal of aerosols from an enclosed environment. UDF was applied to turn the ventilation on after the coughing. Results have shown that without ventilation the aerosols are reaching the outlets of the room faster, while due to the ventilation effect the same aerosols reach slower due to recirculation. Aerosols travel according to the dominant ventilation flow. If the ventilation is turned off and there is no steady downward movement of air, the particles do not fall to the ground but will evaporate with time. Evaporation of the particles depends on the ambient temperature and relative humidity. The existence of running ventilation is required to prevent the circulation of aerosols.
From the start of the 21st century, resource-constrained devices like smart cards, RFID tags and SCADA systems have been utilized commonly in security-critical systems. This vast adoption raised many security concerns like privacy and integrity of the data for stakeholders. Secure cryptographic mechanisms are a vital tool to resolve these issues. The implementation of conventional symmetric and asymmetric ciphers is not feasible because of the limited resources. In March 2017, NIST requested the research community to submit lightweight cryptographic algorithms for future standardization. After submissions, NIST finalized ten algorithms after two rounds of scrutiny. The confusion layer in these ciphers is the essential component that resists maximum security attacks. This study aims to carry out a comparative analysis of the cryptographic properties of the confusion layer of these finalists. The outcome of this research work will assist stakeholders in selecting the right choice for preserving the privacy and integrity of their data in such systems.
This paper presents the design and analysis of a non-linear droop controller of two different secondary controllers that are used in hybrid islanded microgrid systems. Distribution generators are used to provide power to the load in alternating current (AC) microgrid, and photo-voltaic (PV) arrays, connected with a boost converter for obtaining an optimum and stable voltage, are employed in direct current (DC) microgrids where the incremental conductance (InC) Maximum Power Point Tracking (MPPT) algorithm is applied for the extraction of maximum power. An Interlinking Converter (IC) between AC and DC microgrids is controlled by hierarchical architecture primary and secondary controllers during power fluctuations to mitigate non-linearity. The conventional proportional integral (PI) controller and the Sliding Mode Controller (SMC) are employed as secondary controllers. We present a comparison of the performance characteristics of two secondary controllers designed in a MATLAB/Simulink environment. The results demonstrate that a hierarchically controlled AC/DC hybrid microgrid can be effectively, robustly, and reliably operated with the proposed secondary control scheme.
In this paper, a reflective metasurface that can work as a metasurface based perfect absorber in microwave frequency regime is presented. The unit cell consist of star shape copper layer with a square slot printed on FR4, the thickness of substrate is 2.4mm with loss tangent 0.02 backed by a metal ground. The proposed metasurface absorbs electromagnetic (EM) waves in two frequency bands specifically at frequencies from 13.82 – 14.02 GHz and 17.65 – 17.82 GHz. The absorption efficiencies of the proposed metasurface are above 90% within the operating frequency bands. The mirror symmetry of a structure make the response of metasurface same for both transverse electric (TE) or x-polarized and transverse magnetic (TM) or y-polarized incident waves.
The migration movement of fish in regular formation is a common phenomenon in nature. Exploring the principle of hydrodynamics is not only conducive to further understanding the internal mechanism of the fish swarm, but also conducive to optimizing the structural design and formation design of underwater vehicles. The immersed boundary method used in this paper is a non-fitting Cartesian mesh method, which can better deal with the problems of complex geometric shapes and moving boundaries without generating fitting meshes as frequently as the traditional mesh generation method. In this study, a solving program is developed based on the immersion boundary direct force algorithm, which uses multi-grids and non- uniform grids to accelerate the solution of the flow field. The program is verified by a typical example of cylindrical flow, and the corresponding accuracy of the program is demonstrated through comparing the achieved results with that reported in the existing literature. Based on this verified program, the movements of the juxtaposed bionic fishes in incompressible viscous flow are analyzed, the interactions between the movements of fishes and the surrounding flow field are captured, and, importantly, the hydrodynamic mechanism of juxtaposed bionic fishes swimming in a shoal of fish is revealed. Different characteristics of flow fields induced by the juxtaposed bionic fishes’ movements with the same swing frequency but in different phases, namely in-phase and anti- phase, are observed and analyzed. The result shows that the anti- phase scenario is more beneficial to enhancing the overall propulsion performance of the shoal of fish.
This research introduces a tri-band frequency selective surface with multifunction performance at two bands. Nine different functional states are achieved with biasing to the four pin diodes. Two closely spaced bands around 2 GHz and 4 GHz furnish shift in electromagnetic behavior and inversion to plane wave polarization. The binary state "0000" contributes transmission to the dual polarized plane wave for both polarizations at pass band of 2 GHz as central frequency and shielding to the wave at pass band around 4 GHz. Conversely, the binary state "1111" contributes inverse electromagnetic behavior at these bands. The binary state "1010" contributes transmission to the TE wave at 2 GHz frequency and furnishes shielding to the 4 GHz band, whereas the binary state "0101 contributes transmission to the TM wave at 4 GHz frequency with shielding at 2 GHz. The binary state "1101 = 1110" allows to transmit the band around 4 GHz for TE wave, whereas the binary state "1011 = 0111" contributes shielding to the two multi-functional bands around 2 GHz and 4 GHz frequencies. The binary state "1011 = 0111" is inversion of the "1101 = 1110" state. The binary state "1000 = 0100" allows to transmit the band around 2 GHz for TE wave, whereas the binary state "0001 = 0010" contributes shielding to the two multi-functional bands around 2 GHz and 4 GHz frequencies. Converse is true for the binary state "0001 = 0010". The binary state "0011" = "1100" shields both the bands at 2 GHz and 4 GHz frequencies for dual polarized plane wave. All the binary states which contributes a pass band at 2 GHz also add an extra pass band around 5.9 GHz which is angularly stable at TE wave excitation only.
The concept of Anesthesia is found from the carvings of about 2500 BC. A few decades back, an anesthesiologist did the anesthesiology, and a patient’s life depended on one person. So, there was a dire need to automate this system to achieve precision and accuracy and lessen the load from the shoulders of an anesthesiologist. Feedback Control is found everywhere in Engineering World and has shaken up the protection in the fields from Car travel to space. This article discusses the History, Design, and Working of an automatic anesthesia delivery system. It further includes the modern-day investigations in the field, i.e., closed-loop anesthesia Delivery Systems and Target controlled infusion. The introduction of the Bispectral Index as a significant indicator of Depth of Anesthesia is also a part of this article. The supply of low/high doses of anesthesia during an operation may cause adverse effects to the patient. To avoid this situation, an Automatic Anesthesia control system is required to control the amount of anesthetic provided, reducing human error and high precision. The Concentration of the drug is controlled by a multi-task feedback system and Microcontroller chips. Closed-loop systems can make conclusions on their manner. Our work further discusses the superiority of closed-loop systems over the open-loop system and their advantages and disadvantages. The significance of this work is that it helps anesthesiologists to enter a targeted value in the system of human body and save precious lives. The approach will have software-based simulations and empirical data to reduce tolerance levels. The difference in practice will be that we will consider the problems in this automatic control system and try to remove pests with effective use of controls engineering knowledge. The purpose is to make an automated anesthesia control system for isoflurane concentration with a high level of accuracy. Multitasking is the main characteristic of an automatic anesthesia machine, and we will try to discover ways to make it cost-effective, compact, and easy to use. It will be easy to use with a User-Friendly Graphical User Interface and equipped with the latest technology based on researches from the last decade.
Floating satellite (FloatSat) platform for testing and evaluation of Pico/Nano satellite in nearly a frictionless environment. In this paper, we have presented its basic setup and applications regarding communication and control of its speed and velocity. This proposed educational hardware setup serves as a benchmark for students to learn basic satellite systems/subsystems. Furthermore, the setup can be utilized to test and evaluate control algorithms for various space missions.
The good laboratory services are the integral part of any disease diagnosis and surveillance. Efficient and reliable diagnostic tools and kits as well as skilled and trained manpower are the basic requisite to improve health care setting of any under developed country like Pakistan. Indigenization and development of native diagnostics may help to resolve the problem. Owing to the taxonomic changes and complexity of the identification of Enterobacteriaceae, Pseudomonadaceae, Vibrionaceae and related genera, a local Quick testing strip (QTS-24) for identification of gram negative bacteria was developed. The kit is identical to the API 20E. It was designed on the principal of phenotypic biochemical characterization of bacteria. A battery of 24 bio chemical tests was built in local fabricated small cup tests strip, having dried reagents, may be incubated with standard dilution of bacterial strain followed by incubation at 37 o C. This system is capable of identifying 75 species. A comparative analysis of the developed system was run in parallel with the gold standard bacterial identification system (API-20E). 100 known bacterial strains were utilized for this analysis. QTS-24 was found 100% compatible with the API-20E. The greatest efficiency of the QTS -24 systems emphasizes the bulk scale production and countrywide marketing of the product. Moreover, it is also emphasized the development of more bacterial identification systems for other bacteria like MRSA or Mycobacterium which is the biggest challenge for our country.
Off-shore renewable energy offers promising potential for the sustainable growth of nations’ economy. This however is contingent upon the development of cutting edge technologies to effectively and efficiently harvest the Offshore Renewable Energy (ORE). Owing to attractive dividends of ORE, trend to evolve and market disruptive ORE technologies has picked up a rapid and consistent momentum across the globe with major maritime nations assuming the lead role. Developing nations including Pakistan despite being blessed with vast offshore renewable energy potentials have yet to jump start this journey. This paper therefore, focusses on this gap while analyzing in detail the vast offshore renewable energy potentials across the coastal areas and EEZ of Pakistan. The niche maritime technologies required to be indigenously developed for efficiently exploiting these national offshore renewable energy potentials are then presented. The (ORE) sectors covered in this regard include solar, wind, tidal, wave, thermal and osmotic.
Global Navigation Satellite Systems are widely used in numerous industries for positioning, navigation, and timing applications. Nevertheless, there are multiple factors that affect its positioning and dilute its overall accuracy. GNSS performance is characterized by four parameters which include Availability, Continuity, Accuracy, and Integrity. To ensure the best performance, integrity of the system is one of the most important factors to be monitored. In this paper we’ve proposed an integrity monitoring algorithm for single frequency GNSS receivers that detects and identify faulty measurements. Once the faulty satellite is identified, it is excluded from the measurements to ensure reliable outputs. Finally, the results of before and after the exclusion of faulty satellites are compared to ensure positioning accuracy.
The loss of efficiency due to the wingtip vortex was a well-known phenomenon in the aerospace industry. In the case of aircraft, it manifests as the induced drag, whereas in the case of rotary-wing, the vortices form a corkscrew wash and the vortices remain attached to the blade for several rotations. This affects performance parameters, and the blade vortex interaction (BVI) can occur due to the interaction of the trailing vortices of the blade with the other preceding blade. These trailing vortices can cause significant variation in the velocity field, resulting in an unsteady structural load and noise. Helicopters operating near the ground can cause entrainment of dust particles on the ground, affecting the pilot's field of view. This study aims to devise an experiment to measure performance parameters for rotating wings by varying at different pitch angles and RPM. These performance parameters include the coefficient of thrust and torque. This performance measurement was compared with past studies, and the maximum figure of merit from theory was measured to be 0.24. It was found maximum for a pitch angle of 10°, and a drop in the figure of merit was observed due to the stall of the rotating wing. A Numerical scheme was used to analyze sectional pressure on the blade surface. This numerical approach was validated, and then this approach was used to analyze the case of pitch angle 12.5° and RPM of 2000. The results computed from the numerical scheme were used to find the thrust coefficient and pressure coefficient on different sections, which compare well with the variation in mesh size. Error in coefficient of thrust was observed to be up to 5%.
In this paper, motion control and guidance of X-rudder Autonomous Underwater Vehicle (AUV) is studied. The AUV is propelled with the help of a single thruster. In order to achieve motion in all directions, X-rudder is included, which offers better maneuverability and safety as compared to other types of rudders. This design approach offers efficient maneuverability and motion control, however with various challenges with respect to its implementation. Decoupled mathematical model of the AUV in 3 DOF horizontal subsystem is utilized and Sliding Mode Control (SMC) technique is used to design motion control. In order to achieve desired heading of the vehicle, an optimal control allocation problem is solved based on a virtual control input by allocating distributed control effort on each of the 4 fins of the X-rudder to create cumulative desired control input. Furthermore, a constrained optimization method is applied for optimal angle calculation for rudder fins keeping in view either of two objectives i.e. minimum control effort (energy efficient) or minimum desired heading error. Detailed simulation results are presented for performance analysis of the proposed control framework.
Interest in using turbines for ocean wave energy conversion has recently raised owing to their numerous benefits in view of this application. However, the phenomenon of wave-turbine-interaction is complex and requires extensive experimental investigation. Out of the numerous physical parameters involved in the phenomenon, the rotational speed of the turbine carries a particular significance as it links the turbine power output with the characteristics of both the turbine and the waves. Therefore, it was examined with a particular focus in this study using a laboratory based wave flume. However, the angular velocity changes continually owing to variations in speed of water induced by the orbital motion of surface water caused by wave motion. Therefore, it was deemed necessary to measure the turbine instantaneous speed as a function of time. However, most of the commonly used equipment measure the number of complete revolutions per minute as opposed to the instantaneous speed of a rotating object. Consequently, a need arose to employ an unconventional approach in this case. After considering numerous options, the technique of image processing was used with encouraging results. The rotation of the turbine was captured in numerous video footages after affixing a marker to its end plate facing the 16 Mega Pixel camera having a frame capture rate of 30 per second. The results were compared with visual observations at key angular positions of the turbine which showed a good correlation. The use of image processing for measuring instantaneous rotational speed of an underwater turbine interacting with surface waves has not been reported in literature previously and can potentially play a fundamental role in further understanding the complex phenomenon of wave-turbine-interaction. It can therefore help in developing sustainable turbine based ocean waves energy conversion devices.
Missing data is a common occurrence in modern applications such as medical imaging and movie ratings data sets for recommendation systems. Matrix completion is a procedure for recovering the missing entries in a matrix on the basis of the known entries. It is assumed that there is a linear relationship between the rows or columns of the matrix to be recovered, i.e., a small number of rows (or columns) can be used to represent the whole matrix. The matrix completion problem cannot be solved uniquely without imposing constraints such as the low-rank assumption. There are two classes of optimization techniques for sparse matrix completion, namely convex and non-convex approaches. Under the weak assumption that the matrix entries are missing in a non-uniform and deterministic fashion, the matrix completion problem can be formulated as a non-convex bilinear optimization problem that can be solved via the alternating proximal algorithm. On the other hand, the soft-impute algorithm is a convex optimization approach that can deliver fast convergence by exploiting warm-start. In this paper, we test the (convex) soft-impute and (non-convex) alternating proximal matrix completion methods using some real data and furthermore, test [1]’s claim that non-convex approaches perform better than convex approaches. We show a comparison of the two approaches in terms of computational complexity, execution time, and prediction accuracy. In addition, we propose a systematic procedure to perform model selection in both algorithms.
Due to the flexibility and light weight requirements, modern day aircraft is subjected to aeroelastic loads and instabilities. Therefore, in the aircraft design process, static and dynamic aeroelasticity has major contribution. The proposed work is focused on the numerical investigation of variation of modal parameters with variation in store mass at tip of the wing. A wing is designed in CAD software (CATIA) and analyzed for its initial structural layout in MSC Nastran. Tip mass is varied through addition of lumped masses at L.E and T.E of the structure with addition of a rod. Modal parameters sensitivity is studied for a number of combinations which would lead to a feasible cg value of a store with controlled modal parameters.
