In this article, a new fault-tolerant control (FTC) method is presented for the Lipschitz nonlinear systems that is capable of handling the actuator faults, sensor faults, unknown external ...disturbances, and system uncertainties. An augmented system is first constructed by treating the sensor fault as an auxiliary state. An adaptive fault estimation scheme with an <inline-formula> <tex-math notation="LaTeX">H_\infty </tex-math></inline-formula> performance criterion is then developed to simultaneously estimate the actuator and sensor faults. To achieve the tracking control, a nonlinear sliding mode-based state feedback control law is proposed depending on the estimated states and information about fault from the fault estimating unit. The efficacy of the suggested technique is evaluated using a nonlinear model of the multirotor unmanned aerial vehicle (UAV) system with six degrees-of-freedom (DoF) motion. The proposed method is implemented in the inner loop subsystem in order to obtain the attitude and altitude tracking while the outer-loop control is simply a PID controller. Several simulations on the nonlinear system are performed to prove the effectiveness of the proposed method compared with the existing methods.
This research article concentrates on forced convection with a high Reynolds number of the water-alumina-based nanofluid in the square cavity containing a rotating disk with a unit speed. A very ...dense mesh is used to obtain the numerical results with the finite element package of COMSOL Multiphysics 5.6. For the research study, we select the parameters, the Reynolds number (106 to 1.005 × 106), a radius of the rotating disk (0.1m–0.2 m), and volume fraction (0.001–0.009 and 0.01–0.05). About 54 simulations are obtained using the Rayleigh numbers 7 × 106 to 1.54 × 106 and keeping the Prandtl number less than 0.7. The outcomes will be validated with correlations from the local Nusselt number literature and the independent mesh study. The results will be displayed with the surface plots and graphs for temperature, average temperature, local and average Nusselt number, mass flow rate, skin friction coefficient, and average values on the surface of the circular rotating disk. A correlation originated between the temperature as an average on the surface of a rotating cylinder and mass flow rate, which describe a negative association between the mass flow rate and the average temperature on the surface of a circular disk. It was concluded that the coefficient of skin friction improves with an upsurge in volume fraction of the nanofluid, whereas it shows a non-functionality with an average Nusselt number when an increment is made in the radius of a circular disk.
The aim of this paper is to investigate Pakistan's efficient generation portfolios by comparing the portfolio costs, risks, efficient frontiers, and diversification levels under different cases and ...scenarios. Uncertainty in the energy sector of Pakistan has contributed to the necessity of effective electricity planning that can minimize given market risks and discourage the use of stand-alone generating costs. This paper presents a novel energy production optimization empirically using mean-variance portfolio theory. The proposed research work leverages the mean-variance portfolio theory to design an efficient electricity generation mix to diversify its energy mix by investing in renewable energy sources. The portfolio optimization for the energy sector is driven by the minimization of either the cost or risk of the energy resource portfolio subject to various budget constraints. In the context of decentralized energy sources, the current work presents an optimal portfolio design that takes into account average costs, risks, and diversity of the energy resources for electricity generation. This is followed by the computation of optimal efficient frontier for energy portfolio based on extensive statistical analysis over data collected for eight different technologies, namely coal, high-speed diesel, fuel oil, gas, solar, wind, and hydro. Numerical results reveal that diversification of energy sources, which consists of a mixture of all technologies, yields a solution that guarantees reliability of more than 90% for the given data.
Non-Newtonian fluids flow generated by “cilia” are critical in medicine and bio-medical engineering. Such investigations are created by the back-and-forth movement of a microscopic hair-like ...structure connected to the walls, which causes a metachronal wave to form and drive biological fluids. Motivated by a wide range of biological applications, this study aims to explain the incompressible flow of Ellis fluid caused by the propagation of an infinite metachronal wave train traveling along channel walls owing to constantly beating cilia. The problem is simplified by low Reynolds number and long wavelength assumption. The mathematical model is solved with the aid of symbolic computational software Mathematica 13 version. The consequences of emerging parameters are then shown in graphical form and discussed comprehensively. From the study, it is worth mentioning that velocity declines with increasing material constants. Temperature distribution is also improved in the core sector of the channel and reduced at the walls. It is predicted that this approach will make an essential contribution to the progress and enhancement of various types of drug delivery systems in the biomedical industry and biomechanics.
Solar-powered desalination holds the potential to meet rising water needs. Most of the global desalination methods require a lot of electrical energy that mostly comes from non-renewable energy ...resources, including coal, natural gas, and oil. Carbon emissions from these sources cause breathing problems and ozone depletion. An empirical study is performed to evaluate the optically active desalination process. The suggested mechanism moves the light funnel axially regardless of incident light intensity to maintain the water reservoir temperature to a fixed level to perform desalination. To reduce tracking error, control systems with the triple-axis movement of Fresnel lenses are developed using an optimization algorithm employing the least-squares criterion. It also maintains the temperature of the water reservoir at 250°C by absorbing total incident irradiance through a copper slab by incorporating a customized nano honeycomb layer. A textured glass surface on top of the reservoir reduces solar reflections. The light rays are concentrated by top Fresnel lenses, while the bottom Fresnel lens produces a parallel beam of concentrated light that falls on a copper slab inside the reservoir, vaporizing the desalinated water to maintain a clean water supply. Total dissolved solids (TDS), the potential of hydrogen (pH), and microbial measurements are made before and after the desalination process. To increase the rate of desalination and decrease the boiling point of water, a low-pressure suction pump is used. This low-cost and environmentally friendly project produces pure drinking water and could be installed at any location.
Dissimilar redundant actuation systems (DRAS) are in practice in advanced aircraft in order to increase reliability and to resolve the actuator failure issue due to common cause. This paper addresses ...the problem of force fighting that occurs due to dynamics mismatch of two dissimilar actuators in DRAS and provides a method to achieve precise tracking of aircraft control surface. The nonlinear system dynamics are first transformed into linear parameter varying (LPV) form using recursive least square (RLS) method. The LPV observer based controller is then designed to synchronize the positions of dissimilar actuators in DRAS and to drive the control surface smoothly. By applying linear matrix inequalities (LMIs), parameter dependent Lyapunov function (PDLF) is obtained to achieve global stability and to compute the controller and observer gains. To test controller according to real flight condition, an external disturbance signal that acts as air load is applied at the control surface input. Several simulations on the nonlinear system validate the dominant performance of proposed controller as compared to the existing methods in literature.
For the past few years, software security has become a pressing issue that needs to be addressed during software development. In practice, software security is considered after the deployment of ...software rather than considered as an initial requirement. This delayed action leads to security vulnerabilities that can be catered for during the early stages of the software development life cycle (SDLC). To safeguard a software product from security vulnerabilities, security must be given equal importance with functional requirements during all phases of SDLC. In this paper, we propose a policy-driven waterfall model (PDWM) for secure software development describing key points related to security aspects in the software development process. The security requirements are the security policies that are considered during all phases of waterfall-based SDLC. A framework of PDWM is presented and applied to the e-travel scenario to ascertain its effectiveness. This scenario is a case of small to medium-sized software development project. The results of case study show that PDWM can identify 33% more security vulnerabilities as compared to other secure software development techniques.
The paper proposes the application of fractional order controller in position tracking control of 2-link nonlinear robotic arm. The nonlinear system dynamics is linearized using inverse dynamics of ...the model and fractional order PID controller is designed to deal with remaining tracking errors. The optimal values of controller parameters are calculated using Nelder-Mead optimization technique based on desired design criteria. The objective function is designed using weighted sum approach on each performance specification based on transient domain parameters. It can be seen from simulation results that fractional order controller together with computed torque controller improved tracking performance of proposed system as compared to PID controller used in the outer loop. Moreover, the robustness of proposed scheme is checked by applying the disturbance signal at control input channels of 2-link nonlinear robotic arm links.
•This research emphasizes on an adaptive nonlinear integral-sliding-mode (ISM) controller design for F16 aircraft. The objective is to attain the desired maneuvering subject to the unknown external ...disturbance and aerodynamical uncertainty effects.•The nonlinear dynamics of F16 aircraft is first partitioned into inner faster and outer slower loop. For each loop, the adaptive ISM control strategy is proposed where the baseline controller is designed using nonlinear-dynamics-inversion (NDI technique)•The aerodynamics coefficients, that are the nonlinear function of angle-of-attack α, and side slip angle β, are estimated using iterative reweighted least square algorithm. The estimated information is available to the controller design where the estimation error is treated as unmatched uncertainty.•A detailed analysis is performed to show that the aircraft internal dynamics are stable for the applicability of NDI controller.•A detailed comparison is performed with NDI controller and ISM/NDI controller to validate the dominant performance of proposed scheme.
Aircraft dynamics are highly nonlinear and the traditional linear flight controllers cannot fully utilize the real-time performance ability of aircraft. This paper investigates a nonlinear control approach for high maneuvering fighter aircraft that deployed baseline nonlinear-dynamics-inversion (NDI) control and high-level robust adaptive integral-sliding-mode (ISM) control. The design objective is to maintain the acceptable flight quality at a high angle-of-attack under the influence of unknown disturbance and aerodynamics uncertainties. The nonlinear dynamics of F16 aircraft are divided into two loops by utilizing time-scale separation principle and adaptive ISM/NDI controller is designed for each loop. The aerodynamics coefficients are estimated using the iterative reweighted least square (IRLS) algorithm based on the wind tunnel real-time flight data available at NASA Langlet and Ame Research center. The internal dynamics stability is proven to validate the complete system stability. Simulations are conducted on F16 aircraft and compared the results with the NDI controller and ISM/NDI controller (without adaptive strategy).
We investigated the dynamics of nanofluid and heat transfer in a three-dimensional circular annular using the κ−ε turbulence model and energy equations. The pipe contained two concentric and rotating ...cylinders with a constant speed in the tangential direction. A heat flux boundary condition was executed at the inner cylinder of the annular. The pipe was settled vertically, and water alumina nanofluid was allowed to enter, with the initial velocity depending on the Reynolds number, ranging from 30,000 to 60,000. The volume fraction of the solid particles was tested from 0.001 to 0.1. The speed of the rotation of the cylinders was tested in the range from 0.5 to 3.5. The simulations were developed using COMSOL Multiphysics 5.6, adopting the finite element procedure for governing equations. The results were validated using the mesh independent study and the average Nusselt number correlations. We found that the average Nusselt number in the middle of the channel decreases linearly with the increase in the volume fraction of the water alumina nanofluid. The novelty of the present work is that various correlations between the average Nusselt number and volume fraction were determined by fixing the Reynolds number and the rotation of the inner cylinder. We also found that fixing the Reynolds number and the volume fraction improves the average Nusselt number at the outlet linearly. In addition, it was stated that the increase in the total mass of the nanofluid would decrease the average temperature at the outer cylinder of the annular. Moreover, the maximum average improvement percentage in the average Nusselt number, which is about 21%, was observed when the inner cylinder rotation was changed from 1.5 to 2.5 m/s.
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