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Modeling of laser power attenuation by powder particles for laser solid forming

Procedia CIRP 2020年 95卷 42-47页

作者： Junhua Wang Zhen Zhang Fuzhu Han Shu-fan Chen Weisheng Ying Department of Mechanical Engineering Tsinghua University Beijing 100084 China School of Mechatronics Engineering Henan University of Science and Technology Luoyang 471023 China Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control Tsinghua University Beijing 100084 China

Laser solid forming (LSF) is a typical laser additive manufacturing technology integrating rapid prototyping manufacturing and laser cladding. Laser power attenuation greatly influences the amount and distribution of laser energy. It is important to establish a theoretical model of laser power attenuation to effectively control the laser energy transmission and to ensure the stability of the molten pool. Considering the effects of overlap phenomenon among powder particles, a theoretical model of laser power attenuation is proposed by introducing the concept of the effective number of powder particles. The proposed model enables the accurate calculation of the laser power attenuation in arbitrary volume fraction of powder particles. The results indicate that the laser power attenuation is proportional to the powder feeding rate, and the increase rate of laser power attenuation is inverse proportional to the powder feeding rate. In addition, a simple method for measuring the laser power attenuation is also proposed to experimentally validate the proposed theoretical model. The experimental results validate the proposed method.

关键词： Laser power attenuation Laser solid forming Powder stream

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Nonlinear Model Predictive control for Autonomous Sailboat with Optimization of Sail Angle

Nonlinear Model Predictive Control for Autonomous Sailboat w...

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OCEANS

作者： Junzhuo Wu Ya-Jun Pan Chao Shen Sean Smith Emmanuel Witrant Department of Mechanical Engineering Advanced Control and Mechatronics Lab Dalhousie University Halifax Canada Department of Systems and Computer Engineering Carleton University Ottawa Canada GIPSA-lab Université Grenoble Alpes-CNRS Grenoble France Departement of Mechanical Engineering Dalhousie University Halifax Nova Scotia Canada

ISBN: (数字)9798331540081

ISBN: (纸本)9798331540098

This paper studies trajectory tracking control problems of sailing vessels using a nonlinear model predictive control (NMPC) approach with a novel sail angle optimization approach. The proposed sail angle optimization method accounts for physical constraints during practical implementation such as operational sail angle bound and rate of change in sail angles. This technique also emphasizes the potential to use the sail to plan a safe trajectory, while a simple proportional-derivative (PD) controller is used for rudder angle regulation. The NMPC is implemented for trajectory tracking control in the simulation. Results show that the proposed controller can achieve excellent tracking performance in the presence of environmental disturbances in terms of ocean waves.

关键词： Trajectory tracking Oceans Optimization methods Ocean waves Predictive models Regulation Trajectory PD control Predictive control

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On the Process Optimization, Microstructure Evolution, and mechanical Properties of Cucrzr Produced by Laser Directed Energy Deposition

SSRN

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SSRN 2022年

作者： Zardoshtian, Ali Ansari, Mazyar Esmaeilzadeh, Reza Keshavarzkermai, Ali Jahed, Hamid Toyserkani, Ehsan Multi-Scale Additive Manufacturing Lab Department of Mechanical and Mechatronics Engineering University of Waterloo WaterlooONN2L 3G1 Canada Department of Mechanical & Mechatronics Engineering University of Waterloo 200 University Avenue West WaterlooONN2L 3G1 Canada

Laser Directed Energy Deposition (LDED) is a suitable manufacturing technology for processing CuCrZr alloy that has recently gained interest to be used in high heat flux applications due to its unique thermal properties. However, the low laser absorptivity of this alloy at the laser wavelength of 1060 nm and high thermal conductivity make it challenging to reach a successful deposition. This study reports a systematic investigation into the LDED processing of CuCrZr alloy. The effects of main process parameters, which are laser power, scanning speed, and powder feed rate on the geometry, microstructure, and microhardness of single tracks are studied. Process parameters are optimized to achieve acceptable track geometries that consists of proper bead shape and sufficient dilution as well as maximizing the deposition rate. Further, the results from the investigations on microstructure of the printed samples by optical microscopy, SEM, and EBSD methods show a realistic correlation between the microstructure and the process parameters. Laser power and a combined parameter of powder feed rate over scanning speed are found to play a key role in the grain structure morphology and nucleation. Finally, the microhardness results reveal a moderate transition of hardness from the top of the bead to the bottom of the melt pool for all samples. © 2022, The Authors. All rights reserved.

关键词： Microstructure

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Palpation simulator for laparoscopic surgery with haptic feedback

Palpation simulator for laparoscopic surgery with haptic fee...

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Proceedings of the IASTED International Conference on Biomedical engineering

作者： Kim, Sang-Youn Park, Jinah Kwon, Dong-Soo Telerobotics and Control Laboratory Dept. of Mechanical Engineering KAIST Guseong-Dong 373-1 Yuseung-gu Daejeon 305-701 Korea Republic of Comp. Graphics/Visualization Lab. School of Engineering ICU Hwaam-Dong 58-4 Yuseong-gu Daejeon 305-732 Korea Republic of

ISBN: (纸本)0889863792

This paper addresses a real-time palpation simulator that allows surgeons to employ a palpation method during laparoscopic surgery. We use a volumetric liver model obtained from CT (Computer Tomography) data as a target organ. In our simulator, feedback force is calculated according to the material property of the volumetric liver model and human operator's interaction with the volumetric model. The liver is modeled with the Shape-retaining Chain Linked Model (the S-chain model) for real-time volume haptic rendering. Human factor study is performed to investigate whether novices (people who are not familiar with haptic systems) can easily access the abnormal portion from the normal portion of the human liver. The result of the human factor study demonstrates that our simulator is suitable for the simulation of the palpation method.

关键词： Surgery

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Scaling reduction of port-Hamiltonian systems for numerical calculation

Scaling reduction of port-Hamiltonian systems for numerical ...

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ICROS-SICE International Joint Conference 2009, ICCAS-SICE 2009

作者： Nishida, Gou Ichishima, Daiji Kashima, Kenji Fujimoto, Kenji Yamakita, Masaki Maschke, Bernhard Ikeura, Ryojun Robotic Motion Lab. Advanced Science Institute RIKEN Japan Research and Development Center Sumitomo Heavy Industries Ltd. Japan Department of Mechanical and Environmental Informatics Graduate School of Information Science and Engineering Tokyo Institute of Technology Japan Department of Mechanical Science and Engineering Graduate School of Engineering Nagoya University Japan Department of Mechanical and Control Systems Engineering Tokyo Institute of Technology Japan Laboratoire d'Automatique et de Génie des Procédés UMR CNRS 5007 Université Claude Bernard Lyon 1 France Department of Mechanical Engineering Mie University Denmark

ISBN: (纸本)9784907764333

We present a novel reduction method of port-Hamiltonian systems by a renormalization group. The reduced system is suitable for a fast numerical calculation in a mesoscopic scale. Especially, we aim at the development of renormalized molecular dynamics with controls. First, we define a renormalized Hamiltonian with coarse graining. Next, we introduce a renormalized canonical Hamiltonian system. Moreover, we clarify the relationship between the renormalized Hamiltonian system and a Dirac structure. Finally, we obtain necessary conditions of boundary connections for each renormalized Hamiltonian system with different scales. © 2009 SICE.

关键词： Hamiltonians

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A spontaneous driver emotion facial expression (DEFE) dataset for intelligent vehicles

arXiv

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arXiv 2020年

作者： Li, Wenbo Cui, Yaodong Ma, Yintao Chen, Xingxin Li, Guofa Guo, Gang Cao, Dongpu School of Automotive Engineering Chongqing University Chongqing400044 China Department of Mechanical and Mechatronics Engineering University of Waterloo WaterlooONN2L 3G1 Canada Institute of Human Factors and Ergonomics College of Mechatronics and Control Engineering Shenzhen University Shenzhen Guangdong518060 China

In this paper, we introduce a new dataset, the driver emotion facial expression (DEFE) dataset, for driver spontaneous emotions analysis. The dataset includes facial expression recordings from 60 participants during driving. After watching a selected video-audio clip to elicit a specific emotion, each participant completed the driving tasks in the same driving scenario and rated their emotional responses during the driving processes from the aspects of dimensional emotion and discrete emotion. We also conducted classification experiments to recognize the scales of arousal, valence, dominance, as well as the emotion category and intensity to establish baseline results for the proposed dataset. Besides, this paper compared and discussed the differences in facial expressions between driving and non-driving scenarios. The results show that there were significant differences in AUs (Action Units) presence of facial expressions between driving and non-driving scenarios, indicating that human emotional expressions in driving scenarios were different from other life scenarios. Therefore, publishing a human emotion dataset specifically for the driver is necessary for traffic safety improvement. The proposed dataset will be publicly available so that researchers worldwide can use it to develop and examine their driver emotion analysis methods. To the best of our knowledge, this is currently the only public driver facial expression dataset. Copyright © 2020, The Authors. All rights reserved.

关键词： Classification (of information)

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Virtual sensing of wheel direction from redundant sensors in aircraft ground-steering systems

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CEAS Aeronautical Journal 2022年第1期13卷 199-213页

作者： Dal Borgo, Mattia Elliott, Stephen J. Ghandchi Tehrani, Maryam Stothers, Ian M. Institute of Sound and Vibration Research University of Southampton SouthamptonSO17 1BJ United Kingdom Department of Mechanical Engineering KU Leuven Leuven3001 Belgium DMMS Lab Flanders Make Leuven3001 Belgium ENTEG Engineering and Technology Institute Groningen University of Groningen Groningen Netherlands Ultra Electronics Precision Control Systems St Johns Innovation Park CambridgeCB4 0DS United Kingdom

Many safety-critical control systems use multiple redundant sensors to estimate the same controlled signal. If the sensors were to operate perfectly, only a subset of them would need to be used for the estimation. In practice, however, the sensors are subject to uncertainty, minor or major faults and their operation may be nonlinear. It is thus important to reliably estimate the controlled signal under these conditions, and also to assess the degree of confidence with which each sensor should be treated. An example of such a control system is the ground-steering control system of an aircraft nose landing gear. A virtual sensing technique is commonly employed, which estimates the steering angle using the measurements of multiple remote displacement sensors. The wheel position is then calculated as a nonlinear function of these sensor outputs. This paper describes how a digital twin of the ground-steering system, in which the effects of uncertainties and faults can be systematically analysed and studied, is used to assess the accuracy and integrity of the steering angle estimation for a number of different estimation algorithms. Two of these algorithms are based on a least-squares approach, while another is a soft-computing technique based on fuzzy logic. These methods are investigated for several scenarios where model uncertainty, measurement noise and sensor faults are included. It is shown that the soft-computing approach is more robust than the least squares based methods under these conditions. © 2021, Deutsches Zentrum für Luft- und Raumfahrt e.V.

关键词： Wheels

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Simulation environment for an autonomous and decentralized multi-agent robotic system

Simulation environment for an autonomous and decentralized m...

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1992 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 1992

作者： Habib, Maki K. Asama, Hajime Ishida, Yoshiki Matsumoto, Akihiro Endo, Isao Control and System Eng. Dept. University of Technology Baghdad Iraq Institute of Physical and Chemical Research Chemical Engineering Lab. Hirosawa 2-1 Wako-shi Saitama351-01 Japan Information Network System Operation Center University of Tokyo Japan Dept. of Mechanical Engineering Faculty of Engineering Toyo University Japan

ISBN: (纸本)0780307372

An autonomous and decentralized system called ACTRESS (ACTor based Robot and Equipment Synthetic System) is being under development as an intelligent robot system which can execute high level tasks. ACTRESS is composed of multiple robotic agents. Each robotic agent is called "robotor". A robotor may be a robot, a computing system and any other equipments. While researching in this field, many research issues need to have solutions, such issues may include, the communication among the agents and protocols, cooperation among a group of' agents, describing the tasks to be executed, multi-agent motion planning, multi-agent task planning, task description, human interface role, solv ing deadlocks ... etc. The aim or this paper Ls to develop a simulation environment for an autonomous and decentralized multi-agent robotic system. For this purpose, it is necessary to simulate and analyze the main functions of each agent, design and analysis of the actions to be carried out by each agent, analyzing their real time behavior with a variety of situations considering their environment and the treatment of unexpected events. Also, it is necessary to find out an efficient strategy to realize effective means for the agents to form a cooperating manner that support task execution and problem solving. In parallel with the mentioned purposes the ACTRESS structure is simulated as functions and behavior using the developed simulation environment. This simulation includes a roup of mobile robots, human interface and global environment manager. Then, software integration that deal with various aspect of the overall problem is developed. Different experiments are performed to analyze the performance or each individual robotor and the overall system. © 1992 IEEE. All rights reserved.

关键词： Intelligent robots

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Reliability-based topology optimization (RBTO)

Reliability-based topology optimization (RBTO)

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IUTAM Symposium on Topological Design Optimization of Structures, Machines and Materials: Status and Perspectives

作者： Wang, Semyung Moon, Heegon Kim, Chwail Kang, Jenam Choi, Kyung K. Department of Mechatronics Gwangju Institute of Science and Technology 1 Oryongdong Bukgu Gwangju 500-712 Korea Republic of Digital Appliance Research Lab. LG Electronics 327-23 Gasan-dong Keumchun-gu Seoul 153-802 Korea Republic of Department of Mechanical Engineering University of Iowa Iowa City IA 52242 United States

ISBN: (纸本)1402047290

Recently, topology optimization has been the subject of a significant amount of academic and industrial research due to its simplicity in implementation and impact on product design. In this paper, reliability-based topology optimization (RBTO) is introduced for structures, electromagnetics, heat transfer, and coupled systems with consideration of uncertainties in topology optimization. Continuum design sensitivity using the adjoint variable method, the density method, and optimization algorithm (SLP and MMA) are used for topology optimization. PMA is mainly used for reliability computations. Examples are given to validate the proposed method. © 2006 Springer.

关键词： Reliability

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Towards Rehabilitation of Mughal Era Historical Places using 7 DOF Robotic Manipulator

Towards Rehabilitation of Mughal Era Historical Places using...

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International Conference on Robotics and Artificial Intelligence (ICRAI)

作者： Muhammad Bilal Ali Raza Mohsin Rizwan Muhammad Ahsan Hafiz Farhan Maqbool Syed Abbas Zilqurnain Naqvi Al-Khawarizmi Institute of Computer Science UET1 Lahore HCR2 Lab National Center of Robotics and Automation Lahore Pakistan Dept. of Mechatronics & Control Engineering National Center of Robotics and Automation Lahore Pakistan Dept. of Mechatronics & Control Engineering UET Lahore Lahore Pakistan

The central aim of this research is to propose a solution to rehabilitate historic places using a robotic manipulator. In this pursuit, the objective is to clean flat or curved surfaces of mihrab/muqarnas and to write lost Arabic inscriptions on spandrel using 7 Degree of freedom (DOF) robotic manipulator. Inverse kinematics solution for 7 DOF is derived by fixing redundant joint and solving the remaining 6 DOF inverse kinematics. Image processing techniques are used to get data from the given image for the robotic calligraphy operation on the spandrel to restore the lost inscriptions. Path planning exercise is implemented to navigate the end-effector on the desired path to write lost inscriptions and to clean curved surfaces of muqarnas. Proposed solutions are verified by simulation using MATlab. The results showed that the manipulator successfully tracked the given path to perform the desired operation in mihrab as well as calligraphy operation on spandrel.

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