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Decentralized Control Design for Welding Mobile Manipulator
Phan, Tan-Tung,Chung, Tan-Lam,Ngo, Manh-Dung,Kim, Hak-Kyeong,Kim, Sang-Bong The Korean Society of Mechanical Engineers 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.3
This paper presents a decentralized motion control method of welding mobile manipulators which use for welding in many industrial fields. Major requirements of welding robots are accuracy, robust, and reliability so that they can substitute for the welders in hazardous and worse environment. To do this, the manipulator has to take the torch tracking along a welding trajectory with a constant velocity and a constant heading angle, and the mobile-platform has to move to avoid the singularities of the manipulator. In this paper, we develop a kinematic model of the mobile-platform and the manipulator as two separate subsystems. With the idea that the manipulator can avoid the singularities by keeping its initial configuration in the welding process, the redundancy problem of system is solved by introducing the platform mobility to realize this idea. Two controllers for the mobile-platform and the manipulator were designed, respectively, and the relationships between two controllers are the velocities of two subsystems. Control laws are obtained based on the Lyapunov function to ensure the asymptotical stability of the system. The simulation and experimental results show the effectiveness of the proposed controllers.
Decentralized Control Design for Welding Mobile Manipulator
Tan Tung Phan,Tan Lam Chung,Manh Dung Ngo,Hak Kyeong Kim,Sang Bong Kim 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.3
This paper presents a decentralized motion control method of welding mobile manipulators which use for welding in many industrial fields Major requirements of welding robots are accuracy, robust, and reliability so that they can substitute for the welders in hazardous and worse environment. To do this, the manipulator has to take the torch tracking along a welding trajectory with a constant velocity and a constant heading angle, and the mobile-platform has to move to avoid the singularities of the manipulator in this paper, we develop a kinematic model of the mobile-platform and the manipulator as two separate subsystems With the idea that the manipulator can avoid the singularities by keeping its initial configuration m the welding process, the redundancy problem of system is solved by introducing the platform mobility to realize this idea Two controllers for the mobile-platform and the manipulator were designed, respectively, and the relationships between two controllers are the velocities of two subsystems Control laws are obtained based on the Lyapunov function to ensure the asymptotical stability of the system The simulation and experimental results show the effectiveness of the proposed controllers.
A Study on a Mobile Platform-Manipulator
판탄둥(Tan Tung Phan),충탄람(Tan Lam Chung),뇨만융(Manh Dung Ngo),김상봉(Sang Bong Kim) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-
This paper discusses about the decentralized control method for a mobile manipulator, which uses for welding process in many industrial fields. In this paper, the mobile manipulator is divided into two subsystems that are the manipulator and the mobile platform. For this reason, a simple decentralized control method for two subsystems is proposed. The task of the mobile manipulator is the end-effector of the manipulator tracks along a seam and the mobile platform moves to maintain the initial configuration of the manipulator in order to avoiding the singularity of the manipulator in the welding process. Two controllers for the mobile-platform and the manipulator are designed, respectively and they are obtained from the Lyapunov function to ensure the asymptotical stability of the system. The simulation and experimental results have proved the effectiveness of the proposed controllers.
An efficient location-based pilot assignment in Cell-Free Massive MIMO
Nguyen Tien Hoa,Phan Lam Tung,Van Chien Trinh 한국통신학회 2023 ICT Express Vol.9 No.5
Cell-free Massive multiple-input multiple-output can offer many degrees of freedom for the high data rate and coverage probability. This network topology is one of the cutting-edge technologies potentially applied for next-generation wireless communications. In the canonical structure, however, each access point needs to accurately estimate the channel state information for the signal detection in the uplink and the precoding design in the downlink. Due to the finite lengths of coherence intervals, pilot contamination is one of the bottlenecks, reducing the data throughput of each user. We propose an efficient pilot assignment scheme called location-based pilot assignment (LPA) to overcome this limitation. It takes full advantage of the number of orthogonal pilot signals into account. The proposed algorithm divides the coverage area into smaller areas based on the number of users, where each area uses a subset of the pilot signals. Numerical results show that the proposed pilot assignment, LPA, offers good spectral efficiency to every users in the network with a tolerable computational complexity.
Dual-band isotropic metamaterial absorber based on near-field interaction in the Ku band
The Linh Pham,Hong Tiep Dinh,Dinh Hai Le,Xuan Khuyen Bui,Son Tung Bui,Hong Luu Dang,Anh Duc Phan,Dac Tuyen Le,Dinh-Lam Vu 한국물리학회 2020 Current Applied Physics Vol.20 No.2
We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one diskpair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs.