Rigorous Design Procedure Research Articles

Finite‐time tracking control of disturbed non‐holonomic systems with input saturation and state constraints: Theory and experiment

AbstractThis article investigates the finite‐time tracking control problem for disturbed non‐holonomic systems with input saturation and state constraints. Input saturation is ensured by utilizing saturated state feedback and designing auxiliary variables. A rigorous design procedure, which combines barrier Lyapunov function‐based backstepping and neural networks, is introduced to satisfy state constraints and overcome the influence of lumped disturbances. A finite‐time filter is developed to address the explosion of complexity problem. Together with relay switching, the designed saturated controller guarantees that the tracking errors converge to arbitrarily small neighbourhoods around zero within a finite time. Stability analysis indicates that all closed‐loop system signals maintain bounded, and the desired input and state constraints are not violated throughout the control process. To demonstrate the effectiveness of the proposed approach, simulation and experimental results on a wheeled mobile robot are presented.

Strategy towards model-based design and testing of the ITER Plasma Control System

The plasma control system (PCS) forms the backbone of safe and high performance plasma operation in all tokamaks. The ITER tokamak will be significantly larger than its predecessors and will become a nuclear environment at a later stage of its operation. Therefore, new control algorithms for the ITER PCS have to follow a systematic, rigorous and formal design and testing procedure. Then, controllers have to be formally commissioned preceding their ultimate deployment on the PCS for real-time operation. Considering the significant cost of operating the ITER machine and its tight operational schedule, limited time is available for controller commissioning. Therefore, the design team for the ITER PCS is implementing a model-based design and testing approach to exploit models not only for the design and tuning of controllers, but also the verification and validation (V&V) tests. To this end, controllers are first designed in the Plasma Control System Simulation Platform (PCSSP) in Simulink. The PCSSP has been deployed on a continuous integration (CI) server on which V&V and functional performance tests are automatically run and analysed to scrutinize the design. Once controllers have passed the design phase in PCSSP, automatic code generation or manual coding allows implementation on the real-time framework (RTF) forming the real PCS. Components on the RTF are continuously validated against their PCSSP counterparts to make sure the implementation is bug-free. The increasing complexity of the interplay between system requirements, modules, controllers, and tests results is managed in a structured Plasma Control System Database (PCSDB). This PCSDB ultimately allows the monitoring of the PCS design and implementation progress. In this work, we present the stages ITER controllers have to pass and the new tools that are being implemented to facilitate and structure this model-based design and testing workflow.

Energy-efficient recovery of tetrahydrofuran and ethyl acetate by triple-column extractive distillation: entrainer design and process optimization

An energy-efficient triple-column extractive distillation process is developed for recovering tetrahydrofuran and ethyl acetate from industrial effluent. The process development follows a rigorous hierarchical design procedure that involves entrainer design, thermodynamic analysis, process design and optimization, and heat integration. The computer-aided molecular design method is firstly used to find promising entrainer candidates and the best one is determined via rigorous thermodynamic analysis. Subsequently, the direct and indirect triple-column extractive distillation processes are proposed in the conceptual design step. These two extractive distillation processes are then optimized by employing an improved genetic algorithm. Finally, heat integration is performed to further reduce the process energy consumption. The results indicate that the indirect extractive distillation process with heat integration shows the highest performance in terms of the process economics.

A New Approach for the Design, Construction and Control of Compacted Mineral Liners of a MSW Landfill Capping

Design parameters typically used for the mineral liner of landfill cover system (e.g. water content w, dry density ρd and hydraulic conductivity k) are often difficult to obtain on site. After construction, these experimental parameters need to be checked against the predicted values. In this paper, a rigorous procedure for design, construction and control of a compacted mineral liner in a capping multilayer system has been developed. The procedure has been schematically subdivided in three phases. The first phase (design) was based on a wide preliminary set of laboratory tests, composed of classification, compaction and permeability tests. An analytical relationship among degree of saturation Sr, dry density ρd and hydraulic conductivity k is also defined. The second phase (construction) was developed through a suitable compaction of the mineral liner planned after the design phase. The last phase (in-site control) consists of checking the design parameters (w, Sr, ρd, k) actually achieved on site. A comparison between coefficients k, obtained through site permeability tests and an analytical relationship obtained in the design phase, was made successfully. Owing to this new approach, it will no longer be necessary to perform in situ permeability tests, but it will be enough to define the above-mentioned analytical relationship during the design phase. In this way, a dangerous damage to the mineral liner, caused by the execution of invasive permeability tests, will be also avoided.

Design and Numerical Characterization of a Low-Complexity Microwave Device for Brain Stroke Monitoring

This paper presents the design of a novel low-complexity microwave imaging system for monitoring brain stroke. In particular, the design is concerned with the determination of the optimal layout of the antennas array, namely, minimum number, positions, and polarization of the radiating elements, enabling the acquisition of an amount of data such to assure a reliable imaging. This goal is achieved by adopting a rigorous design procedure based on the inspection of the singular value decomposition of the relevant discretized scattering operator and taking into account the actual dynamics and signal-to-noise ratio of the measurement system. The design is first carried out in the case of ideal dipoles and then extended and assessed for actual printed monopole antennas, developed for the imaging system. The resulting system is a helmet equipped with 24 antennas, whose performances have been numerically validated in terms of both spatial resolution and reconstruction capabilities, by employing full-wave numerical simulations, realistic 3-D phantoms of the human head, and an accurate modeling of the actual antennas employed in the system.

Continuous synthesis of gold nanoparticles in micro- and millifluidic systems

Abstract Gold nanomaterials have diverse applications ranging from healthcare and nanomedicine to analytical sciences and catalysis. Microfluidic and millifluidic reactors offer multiple advantages for their synthesis and manufacturing, including controlled or fast mixing, accurate reaction time control and excellent heat transfer. These advantages are demonstrated by reviewing gold nanoparticle synthesis strategies in flow devices. However, there are still challenges to be resolved, such as reactor fouling, particularly if robust manufacturing processes are to be developed to achieve the desired targets in terms of nanoparticle size, size distribution, surface properties, process throughput and robustness. Solutions to these challenges are more effective through a coordinated approach from chemists, engineers and physicists, which has at its core a qualitative and quantitative understanding of the synthesis processes and reactor operation. This is important as nanoparticle synthesis is complex, encompassing multiple phenomena interacting with each other, often taking place at short timescales. The proposed methodology for the development of reactors and processes is generic and contains various interconnected considerations. It aims to be a starting point towards rigorous design procedures for the robust and reproducible continuous flow synthesis of gold nanoparticles. Graphical Abstract:

Application of the finite-element method and the eigenmode expansion method to investigate the periodic and spectral characteristic of discrete phase-shift fiber Bragg grating

The finite-element method (FEM) and eigenmode expansion method (EEM) were adopted to analyze the guided modes and spectrum of phase-shift fiber Bragg grating at five phase-shift degrees (including zero, 1/4π, 1/2π, 3/4π, and π). In previous studies on optical fiber grating, conventional coupled-mode theory was crucial. This theory contains abstruse knowledge about physics and complex computational processes, and thus is challenging for users. Therefore, a numerical simulation method was coupled with a simple and rigorous design procedure to help beginners and users to overcome difficulty in entering the field; in addition, graphical simulation results were presented. To reduce the difference between the simulated context and the actual context, a perfectly matched layer and perfectly reflecting boundary were added to the FEM and the EEM. When the FEM was used for grid cutting, the object meshing method and the boundary meshing method proposed in this study were used to effectively enhance computational accuracy and substantially reduce the time required for simulation. In summary, users can use the simulation results in this study to easily and rapidly design an optical fiber communication system and optical sensors with spectral characteristics.

Extremely Efficient Design of Organic Thin Film Solar Cells via Learning-Based Optimization

Design of efficient thin film photovoltaic (PV) cells require optical power absorption to be computed inside a nano-scale structure of photovoltaics, dielectric and plasmonic materials. Calculating power absorption requires Maxwell’s electromagnetic equations which are solved using numerical methods, such as finite difference time domain (FDTD). The computational cost of thin film PV cell design and optimization is therefore cumbersome, due to successive FDTD simulations. This cost can be reduced using a surrogate-based optimization procedure. In this study, we deploy neural networks (NNs) to model optical absorption in organic PV structures. We use the corresponding surrogate-based optimization procedure to maximize light trapping inside thin film organic cells infused with metallic particles. Metallic particles are known to induce plasmonic effects at the metal–semiconductor interface, thus increasing absorption. However, a rigorous design procedure is required to achieve the best performance within known design guidelines. As a result of using NNs to model thin film solar absorption, the required time to complete optimization is decreased by more than five times. The obtained NN model is found to be very reliable. The optimization procedure results in absorption enhancement greater than 200%. Furthermore, we demonstrate that once a reliable surrogate model such as the developed NN is available, it can be used for alternative analyses on the proposed design, such as uncertainty analysis (e.g., fabrication error).

Design of Single-Level Guyed Towers Considering Interrelationship between Bracing Strength and Rigidity Requirements

AbstractElastic buckling and second-order analyses are conducted to establish a more rigorous design procedure for single-level guyed towers, in which the interrelationship between the strength and...

Comparison of Rigorous Design Procedure with Approximate Design Procedure for Variable Sampling Plans Indexed by Quality Loss

Traditional acceptance sampling plans have focused on the proportion of nonconforming items as an attribute criterion for quality. In today’s modern quality management under high quality production environments, the reduction of the deviation from a target value in a quality characteristic has become the most important purpose. In consequence, various inspection plans for the purpose of reducing the deviation from the target value in the quality characteristic have been investigated. In this case, a concept of the quality loss evaluated by the deviation from the target value has been accepted as the variable evaluation criterion of quality. Further, some quality measures based on the quality loss have been devised; e.g. the process loss and the process capability index. Then, as one of inspection plans based on the quality loss, the rigorous design procedure for the variable sampling plan having desired operating characteristics (VS-OC plan) indexed by the quality loss has been proposed by Yen and Chang in 2009. By the way, since the estimator of the quality loss obeys the non-central chi-square distribution, the rigorous design procedure for the VS-OC plan indexed by the quality loss is complicated. In particular, the rigorous design procedure for the VS-OC plan requires a large number of the repetitive and complicated numerical calculation about the non-central chi-square distribution. On the other hand, an approximate design procedure for the VS-OC plan has been proposed before the proposal of the above rigorous design procedure. The approximate design procedure for the VS-OC plan has been constructed by combining Patnaik approximation relating the non-central chi-square distribution to the central chi-square distribution and Wilson-Hilferty approximation relating the central chi-square distribution to the standard normal distribution. Then, the approximate design procedure has been devised as a convenient procedure without complicated and repetitive numerical calculations. In this study, through some comparisons between the rigorous and approximate design procedures, the applicability of the approximate design procedure has been confirmed.

Finite-time output feedback stabilisation of chained-form systems with inputs saturation

ABSTRACTThis paper investigates the problem of finite-time stabilisation by output feedback for a class of non-holonomic systems in chained form with input saturation. Rigorous design procedure for saturated output feedback control is presented by using the homogeneous domination approach and the nested saturation technique. Together with a novel switching control strategy, the designed controller renders that the states of closed-loop system are regulated to zero in a finite time. A simulation example is provided to illustrate the effectiveness of the proposed approach.

Saturated finite-time stabilization of uncertain nonholonomic systems in feedforward-like form and its application

This paper investigates the problem of finite-time stabilization by state feedback for a class of uncertain nonholonomic systems with inputs saturation. Comparing with the existing relevant literature, a distinguishing feature of the systems under investigation is that the x-subsystem is in feedforward-like form. Rigorous design procedure for saturated finite-time state feedback control is presented by using the adding a power integrator and the nested saturation methods. The development of saturated finite-time controller is also presented briefly for a class of dynamic nonholonomic systems in feedforward-like form. An application example for a kinematic hopping robot is provided to illustrate the effectiveness of the proposed approach.

An UWB LNA Design with PSO Using Support Vector Microstrip Line Model

A rigorous and novel design procedure is constituted for an ultra-wideband (UWB) low noise amplifier (LNA) by exploiting the 3D electromagnetic simulator based support vector regression machine (SVRM) microstrip line model. First of all, in order to design input and output matching circuits (IMC-OMC), sourceZSand loadZLtermination impedance of matching circuit, which are necessary to obtain required input VSWR (Vireq), noise (Freq), and gain (GTreq), are determined using performance characterisation of employed transistor, NE3512S02, between 3 and 8 GHz frequencies. After the determination of the termination impedance, to provide this impedance with IMC and OMC, dimensions of microstrip lines are obtained with simple, derivative-free, easily implemented algorithm Particle Swarm Optimization (PSO). In the optimization of matching circuits, highly accurate and fast SVRM model of microstrip line is used instead of analytical formulations. ADCH-80a is used to provide ultra-wideband RF choking in DC bias. During the design process, it is aimed thatVireq= 1.85,Freq=Fmin, andGTreq=GTmaxall over operating frequency band. Measurements taken from the realized LNA demonstrate the success of this approximation over the band.

Optical characteristic research on fiber Bragg gratings utilizing finite element and eigenmode expansion methods.

Compared with coupled-mode theory (CMT), which is widely used for studies involving optical fiber Bragg gratings (FBGs), the proposed investigation scheme is visualized, diagrammatic, and simple. This method combines the finite element method (FEM) and eigenmode expansion method (EEM). The function of the FEM is to calculate all guided modes that match the boundary conditions of optical fiber waveguides. Moreover, the FEM is used for implementing power propagation for HE11 in optical fiber devices. How the periodic characteristic of FBG causes this novel scheme to be substantially superior to CMT is explained in detail. Regarding current numerical calculation techniques, the scheme proposed in this paper is the only method capable of the 3D design and analysis of large periodic components. Additionally, unlike CMT, in which deviations exist between the designed wavelength λD and the maximal reflection wavelength λmax, the proposed method performs rapid scans of the periods of optical FBG. Therefore, once the operating wavelength is set for the component design, the maximal reflection wavelength of the final products can be accurately limited to that of the original design, such as λ = 1550 nm. Furthermore, a comparison between the period scan plot and the optical spectra plot for FBG indicated an inverse relationship between the periods and wavelengths. Consequently, this property can be used to predict the final FBG spectra before implementing time-consuming calculations. By employing this novel investigation scheme involving a rigorous design procedure, the graphical and simple calculation method reduces the studying time and professional expertise required for researching and applying optical FBG.

New discounted cash flow method: Estimating plant profitability at the conceptual design level while compensating for business risk/uncertainty

Conceptual design of a new plant involves the evaluation of alternative plant configurations to determine physical feasibility (does each achieve desired production levels within the required quality limits?) and economic viability (is sufficient profit generated each year of a multiyear projected lifetime while requiring an acceptably low initial capital investment?). In testing alternatives, designers require both an absolute measure and a normalized measure in order to make a definitive evaluation. In recent years NPV (Net Present Value) has often been chosen as the absolute metric and IRR (Internal Rate of Return) as the normalized one. But these two measures provide insufficient information to develop an optimum design that can be guaranteed suitably profitable, i.e., with optimum design profits high enough to justify investment … more importantly, high enough to warrant taking on the risk/uncertainty characteristics of a particular product/plant with the business environment in which the constructed plant must operate.In this paper a relook at discounted cash flow procedures motivates a new metric based on a normalized and annualized value of NPV, designated NPV%. In line with traditional analysis, a required minimum value –NPV%required (%/year) – once found via ad hoc and/or first principles methods, is assumed to represent suitably the Enterprise's profitability expectations plus the “premium” needed to justify intrinsic business risk/uncertainty. The ability to achieve a value that justifies anticipated risk, however that property is calculated or characterized, is a major element in determining whether projected returns from a particular design are high enough to justify proceeding with the project.Surprisingly, a close analysis of spreadsheet methodology used for discounted cash flow calculations, such as in calculating NPV, reveals unexpected underlying linearities, e.g.,NPV=a(ProfitBT)+b(Fixed Capital)when “factored estimates” are used (usually the case at the conceptual design stage), as well asROIBT=e(NPV%)+fThus maximizing either ROIBT or NPV% is equivalent to minimizing the time to achieve return of invested capital (exposure to risk). NPV measures the effect on a company's balance sheet that will result from a decision to design/construct/operate. Thus once an appropriate risk premium for a plant is agreed upon, a rigorous design procedure can utilize a constrained optimization procedure in which NPV (absolute profitability) and NPV% (inverse of time exposed to the risk of capital loss) are jointly optimized, subject to the constraint NPV%>NPV%required. How much to weight the long-term profitability vs. speed of capital return is essentially a decision for the designers/investors.

A Rigorous Multimodal Analysis and Design Procedure of a Uniplanar 180$^{\circ}$ Hybrid

Uniplanar 180deg hybrids are basic building blocks in uniplanar technology. In this paper, a new rigorous analysis of a uniplanar 180deg magic-T hybrid based on an air-bridged coplanar cross is performed. The analysis proposed is multimodal since it takes into account the coplanar even and odd fundamental modes simultaneously. From this analysis, a complete circuit model for the hybrid is extracted, and the conditions for ideal performance are derived. This new multimodal model is necessary for the design of the hybrid, and allows a quantitative analysis of its performance, notably bandwidth, isolation, and return loss under any actual loading condition. It has been used to design and implement a 180deg hybrid on alumina with a working frequency of 15 GHz. A very good agreement between simulation and measurement is obtained. The experimental results prove a frequency-independent phase-shift behavior with a measured phase error less than plusmn 2deg.

Formation Flight Optimization Using Extremum Seeking Feedback

A comprehensive design procedure based on extremum seeking for minimum power demand formation e ight is presented, the e rst with performance guarantees. The procedure involves the design of a new wake robust formation hold autopilot and transformation of the closed-loop aircraft dynamics to a form in which a newly available rigorous design procedure for extremum seeking is applicable. The design procedure is applied to a formation of Lockheed C-5s, extending the use of maximum performance formation e ight to large transports. By the use of availableexperimental wake data of the C-5, a model of the aircraft in the wakeis developed that models aerodynamic interference as feedback nonlinearities. Thus, this work is also the e rst to attain stable extremum seeking for a plant with nonlinear feedback. Optimal formation e ight is attained by online minimization of an easily measurable objective, the pitch angle of the wingman.

Template design methods for binary stable cellular neural networks

AbstractStable cellular neural networks with binary outputs implement a non‐linear mapping between sets of input and output images. Such a mapping is studied in detail. We prove two theorems: the first one yields a sufficient condition in order that the non‐linear mapping be well‐defined; the second one yields a condition, that allows to describe the mapping through a simple algorithm based on the sign of the initial derivatives. Then we enunciate two additional theorems and two corollaries, that identify the class of templates satisfying the above condition: such a class is shown to be rather large and include, as particular cases, the monotonic templates, and several kinds of non‐monotonic templates. Finally,a rigorous design procedure is proposed. Copyright © 2002 John Wiley & Sons, Ltd.

Structural design and operation of a fully thermally coupled distillation column

A rigorous structural design procedure for fully thermally coupled distillation columns (FTCDC) is applied to the example system of butanol isomers in order to show the design performance. The procedure gives structural information of the column, and therefore iterative computation encountered in the design using conventional procedure and commercial packages can be eliminated. Using the outcome of the structural design, other topics, such as thermodynamic efficiency, dividing wall column structure and the arrangement of interlinking streams, are investigated. Finally, a 3×3 operation scheme, which has favorable indices of multivariable controllability, is examined by checking the control performances of set-point tracking and regulation with a model predictive control.

Rigorous Design of Fully Thermally Coupled Distillation Column.

A rigorous design procedure for a fully thermally coupled distillation column is proposed and applied to an example system of butanol isomer ternary mixture. The design procedure is composed of the calculation of limiting requirements and a rigorous simulation using material and energy balances. The result of the proposed design is compared with the design of a conventional two-column system. It is found that the fully thermally coupled distillation requires less investment and energy cost than conventional distillation, even if higher reboiler temperature is required. It is also pointed out that the dividing wall structure gives less efficient performance than the Petlyuk column having a smaller number of trays of a prefractionator than that of the mid-section of a main column.