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Calibration and verification of DEM parameters for the quantitative simulation of pharmaceutical powder compression process

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POWDER TECHNOLOGY 2021年第PartA期378卷 160-171页

作者： Gao, Yijie De Simone, Giovanni Koorapaty, Maya Takeda Pharmaceut Int Co 35 Landsdowne St Cambridge MA 02139 USA

In pharmaceutical industry, a deep understanding on the physical properties of drug substance and excipients is critical for the quality control of solid dose drug product. The purpose of this work is to develop a quantitative simulation calibration and prediction platform to model powder compression by applying the Discrete Element Method (DEM). The Luding elasto-plastic contact model was applied for particle-particle interactions. The loading stiffness, the unloading stiffness ratio, and the particle density (which served by adjusting the bulk volume of a specificmass of particles) were determined as influential parameters in this study. Calibration was established between DEM parameters and compression profile of pharmaceutical powders in a short timeframe. This platform could capture the main compressibility characteristics of pharmaceutical materials and could successfully provide quantitative predictions on compression profiles of mixtures. It was recommended for development of solid dose DP especially when the amount of DS was limited. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Discrete element method Compression Luding elasto-plastic contact model gradient descent algorithm

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A Low-Cost UAV Swarm Relative Positioning Architecture Based on BDS/Barometer/UWB

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IEEE SENSORS JOURNAL 2024年第23期24卷 39659-39668页

作者： Zhang, Shuning Wang, Ershen Wang, Yongkang Yu, Tengli Jia, Shiyu Xu, Song Qu, Pingping Shenyang Aerosp Univ Coll Aeronaut & Astronaut Shenyang 110136 Peoples R China Shenyang Aerosp Univ Coll Elect Informat Engn Shenyang 110136 Peoples R China Shenyang Aerosp Univ Coll Civil Aviat Shenyang 110136 Peoples R China China Elect Technol Grp Corp Res Inst 54 Shijiazhuang 050081 Hebei Peoples R China

The issue of relative positioning in unmanned aerial vehicle (UAV) swarms is critical for effective cooperative management and network construction. However, the current low-cost BeiDou system (BDS) exhibits poor accuracy, typically ranging from several meters to tens of meters, which fails to meet the basic requirements for cooperative positioning. To address this challenge, a combined positioning architecture based on BDS, barometer, and ultrawideband (UWB), alongside an accuracy optimization algorithm using gradient descent, is proposed. First, existing UAV swarm positioning technologies and algorithms are analyzed. By combining data from BDS, barometer, and UWB sensors, the accuracy problem of the combined system was transformed into an optimization problem. Then, models such as data credibility evaluation, information difference calculation, and gradient descent optimization were used to solve the optimization problem. Finally, a precision-optimized BDS/barometer/UWB-combined positioning architecture is proposed. Simulations and real-world experiments demonstrate that the fusion positioning architecture achieves higher cooperative positioning accuracy compared to mainstream systems, such as inertial navigation systems (INSs) and BDS. The final distance root mean square error (RMSE) is reduced to 1.313 m, a 69.0% improvement over the 4.231 m observed with standalone BDS.

关键词： BeiDou system (BDS) cooperative positioning gradient descent algorithm integrated navigation ultrawideband (UWB) unmanned aerial vehicle (UAV) swarm

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Adaptive optimized DTC-SVM using metaheuristic Bat algorithm for DSIM fed by IMC based on robust synergetic speed controller

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INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS 2021年第1期31卷 p1-25页

作者： Moati, Yahia Kouzi, Katia Iqbal, Atif Univ Laghouat Dept Elect Engn Lab Semicond & Funct Mat Laghouat Algeria Qatar Univ Dept Elect Engn Doha Qatar

Direct torque control (DTC) suffers from the large ripples of the torque and flux, which leads to deteriorating the system performances. Replacing the conventional back-to-back converter with an indirect matrix converter (IMC) can reduce the torque and flux ripples in interior dual stator induction motor. However, the ripples can be still large, and the low harmonic distortion appears in the input current caused by the lack of synchronization between the two stages of the IMC. In order to overcome this problem with improved dynamic performances (torque, flux ripples, and reducing the low harmonic distortion in the input current), a new DTC based on space vector modulation (SVM) with the synchronization between the two stage of IMC is proposed. On the other hand, an adaptive PI controller based on a gradient descent algorithm using metaheuristic Bat algorithm is presented to generate: the desired stator voltages, and the switching states of the inverter stage by the SVM. Furthermore, the control scheme performance is enhanced by inserting a robust synergetic controller (SC) in the outer loop for speed regulation. The obtained simulation results under different operating conditions illustrate the benefit of the proposed control technique, also, it demonstrates the feasibility of the proposed control approach for real-world systems.

关键词： bat algorithm direct torque control dual stator induction motor gradient descent algorithm indirect matrix converter space vector modulation synergetic controller

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A data-driven method for probabilistic response of vibro-impact system with bilateral barriers

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NONLINEAR DYNAMICS 2023年第5期111卷 4205-4219页

作者： Sun, Wenqing Feng, Jinqian Su, Jin Guo, Qin Xian Polytech Univ Sch Sci Xian 710048 Shaanxi Peoples R China

In this paper, a data-driven method is proposed to approximate the probability density function (PDF) of the response for the vibro-impact system with bilateral barriers. Non-smooth property is a challenge in random dynamical system, resulting in complex dynamics, such as discontinuous-induced singularity, grazing and chattering. The vibro-impact system is generally described as a hybrid form with discrete mapping and continuous differential equation. A non-smooth variable transformation is employed to rewritten this hybrid form to an equivalent piecewise version. For the obtained equivalent system, the Gaussian mixture model is proposed to approach the PDF governed by the Fokker-Planck-Kolmogorov (FPK) equation. The proposed algorithm can accurately simulate the PDF of the vibro-impact system with varied restitution coefficients within the theoretical difference allowed by the non-smooth variable transformation method. Taking account of the symmetry of the inverse transformation, the stationary PDF and moments of responses for the original system are obtained. Additionally, two examples are provided to demonstrate the efficiency and correctness of the proposed method.

关键词： Vibro-impact system Probabilistic response Moment estimation Gaussian mixture model gradient descent algorithm

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Global optimization on non-convex two-way interaction truncated linear multivariate adaptive regression splines using mixed integer quadratic programming

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INFORMATION SCIENCES 2022年 597卷 38-52页

作者： Ju, Xinglong Rosenberger, Jay M. Chen, Victoria C. P. Liu, Feng Univ Oklahoma Price Coll Business Div Management Informat Syst Norman OK 73019 USA Univ Texas Arlington Dept Ind Mfg & Syst Engn Arlington TX 76019 USA Stevens Inst Technol Sch Syst & Enterprises Hoboken NJ 07030 USA

Multivariate adaptive regression splines (MARS) has been adopted as a popular surrogate function to model the unknown relationships between input and output variables in complex systems. Searching optimal solutions on the complicated surrogate response surface of MARS serves as important tasks in various applications. In this paper, we present an efficient and effective approach to find a global optimal value of MARS models that incorporate two-way interaction terms which are products of truncated linear univariate functions (TITL-MARS). Specifically, with a MARS model consisting of linear and quadratic structures, we can reformulate the optimization problem on TITL-MARS into a mixed integer quadratic programming problem (TITL-MARS-OPT), which can be further solved in a more principled way. To illustrate the effectiveness of our proposed approach TITLMARS-OPT, we come up with a genetic algorithm and a gradient descent algorithm to solve the original version of TITL-MARS, and we compared the performance of the proposed approach with the benchmark algorithms. Numerical experiments are conducted on a spectrum of examples with different levels of complexity, including 6 existing models and a real world application in the wind farm optimization. Our proposed approach can find a global optimal successfully and efficiently while the comparison algorithms fail to find a global optimal solution. In the end, Python code for TITL-MARS and TITL-MARSOPT is made available on GitHub( https://***/JuXinglong/TITL-MARS-OPT). (c) 2022 Elsevier Inc. All rights reserved.

关键词： Genetic algorithm Global optimization Mixed integer quadratic programming Multivariate adaptive regression splines gradient descent algorithm

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Data-Free Solution of Electromagnetic PDEs Using Neural Networks and Extension to Transfer Learning

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2022年第7期70卷 5179-5188页

作者： Bhardwaj, Shubhendu Gaire, Pawan Univ Nebraska Elect & Comp Engn Lincoln NE 68588 USA Florida Int Univ Elect & Comp Engn Miami FL 33131 USA

In this article, we present a data-free method to solve differential equation using artificial neural networks (ANN). This method exploits the universal function approximation nature of a neural network to mimic a specified partial differential equation (PDE) and provide its solution. Specifically, use of simple feed-forward artificial neural network (FF-ANN) is shown to demonstrate the solution of 1-D second-order differential equations without use of any prior data. The article also demonstrates that the similarity in two PDEs is akin to similarity in the optimized weight matrices attained after the solution using FF-ANN. This property is then utilized for a transferred learning to enable faster convergence of a new PDE, based on the prior solution of a similar PDE. The concept is shown while considering a general form of second-order PDE, and considering specific cases of scalar in-homogeneous wave equation form and Poisson Equation form. Error convergence below 10(-6) is shown and the transferred learning process shows typical time acceleration by a factor of 1.5-3 for the considered equations.

关键词： Mathematical models Neural networks Training Differential equations Optimization Transfer learning Electromagnetics Artificial neural network (ANN) convergence data free electromagnetic (EM) gradient descent algorithm in-homogeneous partial differential equations (PDEs) Poisson equation second order transfer learning wave equation

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Mixtures of Dirichlet-Multinomial distributions for supervised and unsupervised classification of short text data

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ADVANCES IN DATA ANALYSIS AND CLASSIFICATION 2020年第4期14卷 759-770页

作者： Anderlucci, Laura Viroli, Cinzia Univ Bologna Dept Stat Sci Via Belle Arti 41 I-40126 Bologna Italy

Topic detection in short textual data is a challenging task due to its representation as high-dimensional and extremely sparse document-term matrix. In this paper we focus on the problem of classifying textual data on the base of their (unique) topic. For unsupervised classification, a popular approach called Mixture of Unigrams consists in considering a mixture of multinomial distributions over the word counts, each component corresponding to a different topic. The multinomial distribution can be easily extended by a Dirichlet prior to the compound mixtures of Dirichlet-Multinomial distributions, which is preferable for sparse data. We propose a gradient descent estimation method for fitting the model, and investigate supervised and unsupervised classification performance on real empirical problems.

关键词： Clustering gradient descent algorithm Mixture models Text data analysis

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Automatic current control of magnet cranes for steel plate yard automation

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CONTROL ENGINEERING PRACTICE 1998年第10期6卷 1193-1208页

作者： Park, SY Lee, JS Choi, JY Park, BH Pohang Univ Sci & Technol Dept Elect Engn Pohang 790784 South Korea Pohang Iron & Steel Co Tech Res Lab Instrumentat & Control Res Team Pohang 790785 South Korea

This paper presents an automatic current-control method for magnet cranes for thick steel plate yard automation. In moving the steel plates from stack to stack or from stack to shipping truck, it is difficult to lift the correct number of steel plates because the dimensions of the stacked steel plates are in general different, and their other parameters are not completely known and may even vary in a nonlinear fashion. In this paper, recursive form flux equations are first derived for the thick steel plates, and a current equation is then determined for the magnet coil. Based on these equations, an adaptive current predictor is developed to exert the right amount of current on the magnet, so as to lift the correct number of steel plates. When the initial trial with this current fails, a current tuning method is introduced to adjust the current and lift the correct number of plates. The developed magnet current controller has been successfully tested on data obtained from the storage yard at the Pohang Iron & Steel Co. (POSCO). (C) 1998 Published by Elsevier Science Lid. All rights reserved.

关键词： current control adaptive current prediction current tuning gradient descent algorithm adaptive fuzzy logic

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Intrinsic sample mean in the space of planar shapes

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PATTERN RECOGNITION 2016年 60卷 164-176页

作者： Flores, M. J. Gual-Arnau, X. Ibanez, M. V. Simo, A. Univ Jaume 1 Dept Psicol Basica Clin & Psicobiol Castellon de La Plana Castello Spain Univ Jaume 1 Inst New Imaging Technol Dept Matemat Castellon de La Plana Castello Spain Univ Jaume 1 Inst Math & Applicat Dept Matemat Castellon de La Plana Castello Spain

In this paper we consider the shape space as the set of smooth simple closed curves in R-2 (parameterized curves), modulo translations, rotations and scale changes. An algorithm to obtain the intrinsic average of a sample data (set of planar shape realizations), from the identification of the shape space with an infinite dimensional Grassmannian is proposed using a gradient descent type algorithm. A simulation study is carried out to check the performance of the algorithm. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Intrinsic sample mean Parameterized closed curve Shape space gradient descent algorithm

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Energy optimal motion planning of a 14-DOF biped robot on 3D terrain using a new speed function incorporating biped dynamics and terrain geometry

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ROBOTICA 2022年第2期40卷 250-278页

作者： Kumar, Jitendra Dutta, Ashish IIT Kanpur Dept Mech Engn Kanpur 208016 Uttar Pradesh India

In this paper, a new method is proposed to find a feasible energy-efficient path between an initial point and goal point on uneven terrain and then to optimally traverse the path. The path is planned by integrating the geometric features of the uneven terrain and the biped robot dynamics. This integrated information of biped dynamics and associated cost (energy) for moving toward the goal point is used to define the value of a new speed function at each point on the discretized surface of the terrain. The value is stored as a matrix called the dynamic transport cost (DTC). The path is obtained by solving the Eikonal equation numerically by fast marching method (FMM) on an orthogonal grid, by using the information stored in the DTC matrix. One step of walk on uneven terrain is characterized by 10 footstep parameters (FSPs);these FSPs represent the position of swinging foot at the starting and ending time of the walk, orientation, and state (left or right) of support foot. A walking dataset was created for different walking conditions (FSPs), which the biped robot is likely to encounter when it has to walk on the uneven terrain. The corresponding energy optimal hip and foot trajectory parameters (HFTPs) are obtained by optimization using a genetic algorithm (GA). The created walk dataset is generalized by training a feedforward neural network (NN) using the scaled conjugate gradient (SCG) algorithm. The Foot placement planner gives a sequence of foot positions and orientations along the obtained path, which is followed by the biped robot by generating real-time optimal foot and hip trajectories using the learned NN. Simulation results on different types of uneven terrains validate the proposed method.

关键词： Fast marching method Speed function Uneven terrain Dynamic transport cost matrix gradient descent algorithm Genetic algorithm Footstep parameters hip and foot trajectory parameters

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