Quasi-physical Model Research Articles

Adaptive finite-time extended state observer-based model predictive control with Flatness motivated trajectory planning for 5-DOF tower cranes

This paper introduces a new method to control a 5-DOF tower crane (3DTC). By considering the 3DTC as a flat system, a time-optimal trajectory is proposed for the payload. System states and control signal references can be calculated based on the flatness theory. In addition, the 3DTC works in an environment containing many factors impacting control performance and the system states are hard to measure. An adaptive finite-time extended state observer (AFT-ESO) is introduced to solve these problems. With AFT-ESO, system states and lumped disturbances can be estimated accurately, facilitating the prediction for Lyapunov-based model predictive control (LMPC) when an accurate model is required. The LMPC takes advance of the second-order sliding mode control stability conditions as a strict constraint to guarantee the global stabilization of the closed-loop system. Finally, simulations based on the quasi-physical model are proposed to show the effectiveness and robustness of the proposed strategy.

Comparative validation of global and climate-specific decomposition models at high latitudes

Reliable modelling of the solar potential of urban surfaces (i.e. roofs, facades and ground) in the built environment can contribute to boost the exploitation of solar energy. Empirical and quasi-physical models are combined into model chains for this scope. Among these models, the decomposition models are used to separate the direct from the diffuse solar irradiance. Such variables are rarely measured, thus making necessary their computation. Studies in literature pointed out that Yang4 is the best-performing decomposition model globally. However, in geographically limited applications, quasi-universal decomposition models like Yang4 and Engerer4 can be outperformed by local models (i.e. models parametrized with climate-specific data) such as Skartveit3 and Starke3. This makes necessary to perform local validation studies to verify the findings from worldwide validation studies. In this study, the four best-performing decomposition models are implemented in Python and experimentally validated against 1-min solar irradiance data (i.e. direct and diffuse irradiance) of Trondheim (Lat. 63°26′N, Norway). More than 1-year long data are considered. The study confirms that the Yang4 model performed the best for high-latitude applications, but Starke3 can achieve a level of performance close to Yang4.

Quasiphysical model for removing short glitches from LIGO and Virgo data

Quasiphysical model for removing short glitches from LIGO and Virgo data

Modified Quasi-Physical Grassland Fire Spread Model: Sensitivity Analysis

Developing models for predicting the rate of fire spread (ROS) in nature and analyzing the sensitivity of these models to environmental parameters are of great importance for fire study and management activities. A comprehensive sensitivity analysis of a general and modified quasi-physical model is provided in the current study to predict parameters that affect grassland fire propagation patterns. The model considers radiative heat transfer from the flame and fuel body and convective heat transfer to predict the fire’s rate of spread and the grassland fire patterns. The model’s sensitivity to ten main parameters that affect fire propagation, including temperature, humidity, wind speed, specifications of vegetable fuel, etc., is studied, and the results are discussed and analyzed. The model’s capability is validated with experimental studies and a comprehensive physical model WFDS. The model’s capability, as quasi-physical, faster than the real-time model, shows high consistency in fire propagation parameters compared with experimental real data from the Australian grassland fire Cases C064 and F19. The comprehensive sensitivity analysis provided in this study resulted in a modified equation for the corrected rate of fire spread which shows quite an improvement in ROS prediction from 5% to 65% compared with the experimental results. The study could be a base model for future studies, especially for those researchers who aim to design experiments and numerical studies for grassland fire spread behavior.

Quasi-Physical Equivalent Circuit Model of RF Leakage Current in Substrate Including Temperature Dependence for GaN-HEMT on Si

This article proposes a quasi-physical equivalent circuit model of RF leakage current in the substrate including temperature dependence for GaN-high-electron-mobility transistor (HEMT) on Si. In the proposed model, the effects of electrons and holes near the interface between the buffer layer and the Si substrate are considered to model the RF leakage current. Furthermore, the physical mechanism of the RF leakage current is analyzed using technology computer aided design (TCAD) simulation. Through the analysis, it was found that the RF leakage current increased at a high drain voltage and high temperature; this is because electrons were generated in the inversion layer at the interface between the buffer layer and the Si substrate with a low acceptor concentration. To model the RF leakage current, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$</tex-math> </inline-formula> circuit corresponding to the physical structure of GaN-on-Si between the drain and the source terminal was added to Angelov-GaN large-signal model. Moreover, the resistance and capacitance in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$</tex-math> </inline-formula> circuit were derived from the physical equation of the electron and hole densities in the Si substrate to consider the temperature and bias dependence of the RF leakage current. Upon the verification of the proposed model, it was proven to accurately reproduce the measurement of the temperature characteristics of the power sweep. The large-signal model with the proposed quasi-physical model of RF leakage current can simulate the degradation of the RF performance due to the extrinsic RF leakage current generated by the electrons and holes in the Si substrate. Moreover, the model also agreed with the measured dependence of large-signal characteristics on the drain electrode width. The proposed model was confirmed to be useful for the design of the transistor and amplifier.

A quasi-physical method for random packing of spherical particles

In this work, a quasi-physical method for the random packing of spherical particles based on the equivalent spring structure and the principle of force equilibrium is proposed. The model is inspired by a meshing method “Distmesh”. For the purpose of generating a feasible packing, the proposed model calculates the displacements of each particle based on physical principles and disregards forces that may not help with convergence, thus offering a natural and possibly fast route towards the final packing configuration. The packing densities predicted by the proposed method are in good agreement with those predicted by other methods and the experimental results. Finally, the topological properties of the packing of particles with log-normal size distributions, binary mixtures and ternary mixtures are evaluated by radical tessellation. The results show that the particle size differences and the proportions of each kind of particles have significant effect on the packing properties of the mixture. • Proposing a new quasi-physical model for the random packing of particles. • The model is inspired by a meshing method, which can more easily form force grids. • The model offers a natural and possibly fast route towards the final packing. • The particle size and volume ratio have significant effect on the packing properties.

Adaptive Sliding Mode Control Anticipating Proportional Degradation of Actuator Torque in Uncertain Serial Industrial Robots

The paper focuses on faulty actuator problems in an industrial robot using servomotors, and provides an adaptive sliding mode control law to overcome this circumstance. Because of multifarious reasons, robot actuators can undergo a variety of failures, such as locked or stuck joints, free-swinging joints, and partial or total loss of actuation effectiveness. The robot behavior will become worsen if the system controller has not been designed with adequate faulty tolerance. The proportional degradation of actuator torque at unknown degrees of loss, which is one type of partial loss of actuation effectiveness, is considered in this study to design a suitable controller. The robot model is constructed with uncertain parameters and unknown friction, whereas the controller uses only the approximate parameters. Symmetry and skew-symmetry give important contributions in robot modeling and transformation, as well as in the process of proving the system stability. An adjustable coefficient vector of the proposed controller can adaptively reach the upper bounds of an uncertain parametric vector, which guarantees the criterion of Lyapunov stability. In the numerical simulation stage, the selected industrial robot is a Serpent 1 robot with three degrees of freedom. A quasi-physical model based on MATLAB/Simscape Multibody for the robot is built and used in order to increase the reliability of the simulation performance closer to reality. Simulation results illustrate the efficiency of the proposal control methodology in the presence of the mentioned failure. The controller can still deliver satisfactory responses to the robot system under reasonable levels of actuator torque degradation.

Impact analysis of actuator torque degradation on the IRB 120 robot performance using simscape-based model

Actuators in a robot system may become faulty during their life cycle. Locked joints, free-moving joints, and the loss of actuator torque are common faulty types of robot joints where the actuators fail. Locked and free-moving joint issues are addressed by many published articles, whereas the actuator torque loss still opens attractive investigation challenges. The objectives of this study are to classify the loss of robot actuator torque, named actuator torque degradation, into three different cases: Boundary degradation of torque, boundary degradation of torque rate, and proportional degradation of torque, and to analyze their impact on the performance of a typical 6-DOF robot (i.e., the IRB 120 robot). Typically, controllers of robots are not pre-designed specifically for anticipating these faults. To isolate and focus on the impact of only actuator torque degradation faults, all robot parameters are assumed to be known precisely, and a popular closed-loop controller is used to investigate the robot’s responses under these faults. By exploiting MATLAB-the reliable simulation environment, a simscape-based quasi-physical model of the robot is built and utilized instead of an actual expensive prototype. The simulation results indicate that the robot responses cannot follow the desired path properly in most fault cases.

Spherical Quasi-Physical Model-Based Color-Shift Keying for Visible Light Communication

In this paper, the new family of spherical color-shift keying (SCSK) constellations is proposed for visible light communication (VLC) systems. Specifically, the constant-intensity constraint (CIC) for conventional color-shift keying (CSK) schemes, which originates from the requirement of non-flickering illumination, confines the constellation symbols on a two-dimensional (2D) plane of the three-dimensional (3D) intensity space. To fully utilize the potential degree of freedom offered by the 3D intensity space, we propose to expand the envelope of CSK constellations by replacing the constant intensity with a new spherical intensity constraint, aiming to maximize the minimum Euclidean distance (MED). More explicitly, we design the robust SCSK constellations with and without white color balance (CB), respectively. Particularly, we transform the constellation design problem to the so-called spherical circle packing (SCP) problem, which is resolved based on the spherical quasi-physical (SQP) model. Then, we propose the so-called spherical heuristic quasi-physical algorithm (SHQPA) integrating the binary search algorithm (BSA) and the configuration update algorithms (CUA) to obtain the optimal SCSK constellations. Furthermore, we also study the corresponding bit-to-symbol mapping rules for the generated SCSK constellations. Simulation results show that the new family of SCSK constellations outperforms the conventional CSK counterparts.

An Analytical Approach to Estimate the Effect of Surface Roughness on Particle Rebound

Atmospheric air is always contaminated by liquid or solid particles of different size, concentration and chemical composition. This leads to performance degradation during the operation of stationary or flying gas turbines. Erosion and the deposition of particles along the flow path are of particular importance. Multiple numerical studies investigated the influences of these phenomena. However, the basic challenge of modelling the particle wall interaction and its data spread with sufficient accuracy remains. In this work a model that estimates the statistical spread of rebound data due to target surface roughness through analytical considerations is presented. The model predicts the local impact angle of an individual particle by evaluating how deep a particle can theoretically penetrate the target surface with respect to its size. Based on roughness profiles which have been found to be characteristic for performance deterioration in compressor application a sensitivity study is conducted. A dimensionless roughness parameter Φ_R was found that characterizes the effect of target surface roughness on rebound spread data. The spread model is connected with a quasi-physical model, to evaluate the effect of surface roughness for a particle’s individual rebound behaviour. The synthesized data is discussed by taking into account measurement data reported in literature.

Effect of Actuator Torque Degradation on Behavior of a 6-DOF Industrial Robot

Actuator faults of robot manipulators may occur during their lifetime after long time in operation. There are several kinds of actuator failures such as locked joints, free-swinging joints, and loss of actuator torque effectiveness. The main goals of this paper are (i) to classify the loss of torque effectiveness, called torque degradation, into three divergent cases: Boundary Degradation of Torque (BDT), Boundary Degradation of Torque Rate (BDTR), and Proportional Degradation of Torque (PDT); and (ii) to analyze their effect on behavior of a typical industrial robot. The possible failures might degrade the whole system performance or in some certain cases leading to unavoidable damages. In normal operation, we do not have a controller designed specifically for these faults. In order to have a better understanding on how the mentioned problems affect robot operations, with an assumption that the knowledge of robot parameters are known, a closed-loop control law is used to demonstrate the control ability in dealing with these cases. By taking advantage of MATLAB/Simscape Multibody, the quasi-physical model of robot is employed instead of expensive prototypes and experiments. Simulation results show that the joint responses according to different types of failures. In many cases, the robot cannot track the reference trajectories properly.

Experimental Study on Downslope Fire Spread over a Pine Needle Fuel Bed

The downslope fire represents a percentage of wildland fireline while the heat transfer mechanism of this process is poorly understood. In this study, the experiments were carried out in a fuel bed of dead pine needles with the slopes of − 30°, − 20°, − 10° and 0° for 0.4 and 0.8 kg/m2 fuel loads. Flame length, flame angle, temperatures over the fuel bed, flow speed at the fuel bed surface, radiation heat flux near the end of the fuel bed were measured. The rate of spread shows a parabolic shape which decreases firstly and then increases from 0° to − 30°. The combustion interface, reconstructed from the temperature histories of two vertical thermocouples, was perpendicular to the fuel bed under all slope conditions for two fuel loads. The measured radiation heat flux is higher at − 30° slope than level ground, which is attributed to higher flame emissivity. A quasi-physical model was developed to describe the heat transfer mechanism of downslope fire spread. The calculation results show that the flame radiation dominated the downslope fire spread process and the combustion zone radiation should not be neglected in the near flame region.

Comparison of the World and European Records in the 100m Dash by a Quasi-Physical Model

The aim was to employ a quasi-physical model to analyse the performance and biomechanics of the World and European records at the 100m dash in Athletics. At the time of this research, the World record was hold by Usain Bolt (Jamaica) with 9.58s and the European record 9.86s by Francis Obikwelu (Portugal). The analysis of the performance employs a quasi-physical model that feature the drive, maintenance, velocity and drag terms. Obikwelu showed a slower start (drive term) and Bolt a lower rate of deceleration over the race (propulsive term). The velocity and drag terms were higher for Bolt. Correcting the race time for a hypothetical null wind speed, Bolt's time would have been 9.62s (i.e. a 0.04s impairment) and 9.89s for Obikwelu (i.e. a 0.03s impairment).

Impact ionization in AlxGa1−xAsySb1−y avalanche photodiodes

Avalanche photodiodes (APDs) have been fabricated in order to determine the impact ionization coefficients of electrons (α) and holes (β) in AlxGa1−xAsySb1−y lattice matched to GaSb for three alloy compositions: (x = 0.40, y = 0.035), (x = 0.55, y = 0.045), and (x = 0. 65, y = 0.054). The impact ionization coefficients were calculated from photomultiplication measurements made on specially designed APDs, which allowed for both pure electron and pure hole injection in the same device. Photo-multiplication measurements were made at temperatures ranging from 77 K to 300 K for all three alloys. A quasi-physical model with an explicit temperature dependence was used to express the impact ionization coefficients as a function of electric-field strength and temperature. For all three alloys, it was found that α &amp;lt; β at any given temperature. In addition, the values of the impact ionization coefficients were found to decrease as the aluminum concentration of the AlGaAsSb alloy was increased. A value between 1.2 and 4.0 was found for β/α, which is dependent on temperature, alloy composition, and electric-field strength.

A coarse-to-fine quasi-physical optimization method for solving the circle packing problem with equilibrium constraints

This paper addresses an important extension of the circle packing problem (CPP), the circle packing problem with equilibrium constraints (CPPEC). It considers the dense packing of n circular disks in a large circular container at the same time satisfying the equilibrium constraints. Under the industrial background of the layout design on satellite modules, this NP-hard global optimization problem is important in both theory and practice. We introduce two new quasi-physical models for solving CPPEC in this paper. One is to mimic the elastic movement driven by repelling forces from extruded disks, the other is to simulate a whole translation movement of the disks driven by a pulling force from an imaginative elastic rope connecting the centroid of the disks and the center of the container. Then, inspired by the coarse-to-fine control strategy in the manufacture industry, we propose a coarse-to-fine quasi-physical (CFQP) optimization method that adopts the two quasi-physical models for the quasi-physical descent procedure and combines a basin hopping with tabu method for the search procedure. In this way, not only could CFQP take into account the diversity of the search space to facilitate the global search, but it also does fine search to find the corresponding local minimum in a promising local area. Experiments were on two sets of 11 representative test instances. Computational results showed that CFQP achieved new and better results on four instances, at the same time it matched the current best records on the other six (accurate to 0.0001). Moreover, CFQP resulted in smaller equilibrium deviations than that of others published in the literature. In addition, we generated 34 new CPPEC instances basing on the CPP benchmarks, and provided computational results on the two sets of 34 new CPPEC instances, and the container radii obtained are close to the published results on CPP.

Performance of a Geobag Revetment. II: Numerical Modeling

An intensive study including laboratory experiments and use of a computer software on geobag revetment performance was reported in the companion paper. To represent the failure initiation, a set of quasi-physical model runs was carried out and the conveyance estimation system (CES) computer software was employed to predict active shear stress on geobags and mobile sand bed formation. The CES could predict the depth-averaged velocities in the laboratory measurements with reasonable accuracy. This paper reports the second part of the study, dealing with the discrete element modeling (DEM) simulation. The CES results were used for preparing a mapped velocity field for a coupled DEM simulation of geobag revetment failure. The validated DEM model could identify well the critical bag location in varying water depths and with varying bed formations. Toe scour, one of the major instability factors in revetments, and its influence on bottommost layer of the bags were also reasonably represented in this DEM model. It is envisaged that the use of a DEM model will provide more details on geobag revetment performance in riverbanks.

Optimization of 40-nm Node Epitaxial Diode Array for Phase-Change Memory Application

A numerical model of an epitaxial (EPI) diode array for next-generation memory device application, including phase-change memory, has been presented. According to a diode array process scheme and technology computer-aided design (TCAD) simulation results, a quasi-physical model with a buried n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> layer dosage, EPI layer thickness, and breakdown voltage (BVD) correlation is proposed to improve electrical performance. From the optimal silicon-based results, a 16×16 diode array shows a drive current density of ~56.6 mA/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , a BVD of ~8 V, a J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> ratio of ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> , and crosstalk immunity. Additionally, this calibrated physical model can be applied in the next generation of silicon-based fabrication with parameters extraction.

Wildland surface fire spread modelling, 1990 - 2007. 1: Physical and quasi-physical models

In recent years, advances in computational power have led to an increase in attempts to model the behaviour of wildland fires and to simulate their spread across the landscape. The present series of articles endeavours to comprehensively survey and précis all types of surface fire spread models developed during the period 1990–2007, providing a useful starting point for those readers interested in recent modelling activities. The current paper surveys models of a physical or quasi-physical nature. These models are based on the fundamental chemistry and physics, or physics alone, of combustion and fire spread. Other papers in the series review models of an empirical or quasi-empirical nature, and mathematical analogues and simulation models. Many models are extensions or refinements of models developed before 1990. Where this is the case, these models are also discussed but in much less detail.

A quasi-physical model for predicting the thermal insulation and moisture vapour resistance of clothing

Based on the improved understanding of the effects of wind and walking motion on the thermal insulation and moisture vapour resistance of clothing induced by air ventilation in the clothing system, a new model has been derived based on fundamental mechanisms of heat and mass transfer, which include conduction, diffusion, radiation and natural convection, wind penetration and air ventilation. The model predicts thermal insulation of clothing under body movement and windy conditions from the thermal insulation of clothing measured when the person is standing in the still air. The effects of clothing characteristics such as fabric air permeability, garment style, garment fitting and construction have been considered in the model through the key prediction parameters. With the new model, an improved prediction accuracy is achieved with a percentage of fit being as high as 0.96.

Discrimination of Quantum States with Linear Optics and Continuous Photon Counting

We investigate a systematic method of implementation of given measurements with linear optics and continuous measurement. We revisit the so-called Dolinar receiver, which is a quasi-physical model attaining the minimum error discrimination of binary coherent states, and show that it can be derived without heuristic assumptions. Our approach also can be applied to various kinds of measurements.