Papers by Keyword: Singularity

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Authors: Wen Jia Chen, Yan Zhong He, Jiang Zhang
Abstract: In the past decades, a number of parallel manipulators have been extensively studied. However, most efforts are dedicated to six degrees of freedom (DOF) or three-DOF manipulators. There is a need for equipment providing more than three DOF's arranged in parallel and based on simpler arrangements than six-DOF arrangements in application. This paper presents a novel four-DOF parallel platform manipulator with base mounted prismatic actuators. The manipulator is driven by four linear actuators. The movable platform of the manipulator can translate along two directions and rotate around two axes respectively. The kinematics model is formulated, which describes the inverse and forward kinematics transformation. It is very easy to develop a five-axis NC machine-tool which is of large-workspace based on the four-DOF parallel mechanism presented in this paper.
2168
Authors: Han Bo Li, Ying Jun Zhao, Dong Hui Zhang, Wei Pan
Abstract: The basic principle of the wavelet analysis method to extract the mineral spectral absorption characteristics is summarized and different wavelet bases,wavelet decomposition scale extraction effect are analyzed in this paper. Then, the algorithm of mineral spectral absorption characteristics based on wavelet spectral analysis is provided and a large number of experiments are carried out using the spectrums of field rock mineral. Experimental result shows that such a method is less affected by original signal noise and depict the parameters of the mineral spectral absorption feature more precise, which is an ideal spectral feature extraction method compared with the traditional mineral spectral absorption feature extraction method.
617
Authors: Rui Qin Guo, Wei Hu, Juan Liu, Song Lin
Abstract: The singularity, namely, the output movement of the mechanism is uncertain due to kinematic bifurcation at the singular position, is the intrinsic characteristic of mechanism, resulting in movement out of control. To find a practical solution for this vexed question to make mechanism able to avoid its singular position is the greatest challenge in the field of mechanism. Based on the study of the planar four-bar linkage with singularity, the ideology of introducing self-adaptive mechanism theory into the solution of avoid singularity problem is firstly put forward in this paper. Using self-adaptive mechanism to complement the out of control parameters of singular position can make the mechanism have the ability to avoid singularity. Then the mechanism passes through the singular position smoothly with determined movement and load capability. Finally, the purpose of avoiding singularity is achieved.
227
Authors: Wen Jia Chen, Lan Lei Zhao
Abstract: Though computer technology has brought about virtual manufacturing to expedite design and analysis through simulation and visualization, machines remain essential, as ultimately products need to be made. There is a need for equipment providing more than three degrees of freedom (DOF) arranged in parallel and based on simpler arrangements than 6-DOF arrangements in application. This paper presents a new 4-DOF hybrid parallel platform manipulator with fixed-leg lengths and base mounted prismatic actuators. The movable platform of the manipulator can translate along two directions and rotate around two axes respectively (2T-2R). The kinematics model is formulated, which describes the inverse and forward kinematics transformation. It is very easy to develop a 5-axis NC machine-tool which is of large-workspace based on the 2T-2R, 4-DOF parallel mechanism presented in this paper.
1743
Authors: Qi Shuai Liu, Xi Yang, Wei Di Jin
Abstract: This paper devotes to address the problem of the singularity of the Stewart platform, which is different from the serial mechanism. An algorithm has been constructed; also, by solving a minimum problem, it finds a alternative path to instead the preliminary path, in which there are several singular configurations. At the end of this paper, a numerical case has been developed and gives two points on the preliminary path. By applying this algorithm, a singularity-free path can be found to avoid the singularities in the preliminary path and ill-condition. So, this algorithm can be proven practical.
27
Authors: Ji Man Luo, Li Na Cong, Tian Fang
Abstract: Kinematics simulation and characteristics of a new type of parallel robot manipulator (PRM) with two-dimension movement and one-dimension rotation are analyzed. The new PRM is proved to can realize expected movement, and have smooth movement curves of displacement and velocity. The moving platform center of the PRM can achieve a wide range of swing, and has a larger working space. According to the kinematics theory, the working space and singularity characteristic are analyzed. Simulation and analysis indicated that the working space of the new PRM in the form and position is not singular, and has good maneuverability, thus providing the foundation for practice application and product exploitation.
1294
Authors: Xing Qiang Tan, Zhi Jiang Xie, Guo Yun Li
Abstract: A new kind of parallel mechanism used for faster response and higher maneuverability test of wind tunnel is introduced. Based on static equilibrium analysis and screw theory, the static equilibrium equation of motion platform is established, and then kinematic Jaccobian matrix is achieved by use of force Jaccobian matrix. By means of kinematic Jaccobian matrix the singularity of 6_PUS parallel mechanism is analyzed and three kinds of singularity and their conditions are identified.
2162
Authors: Xue Feng Zhou
Abstract: This paper presents an optimization method for redundant manipulator redundancy resolution with additional task. The cost function is a compromise between the requirement of accuracy of the main task, the accuracy of the additional task, and the feasibility of the joint velocities. The joint rates that minimize the cost function can be found, and the joint position trajectories can be integrated with an initial configuration. The effectiveness of this presented method is verified by a planar 3-DoF PRR manipulator.
1787
Authors: Chao Yang, Zhen Huan Zhou, Xin Sheng Xu
Abstract: In this paper, a numerical analytical method for singularity problem in V-type notch is presented based on Hamiltonian system. The method has an advantage that all boundary conditions can be considered with one model, and belongs to a general numerical method. Results show that the singularity of the problem relates to the opening angle of the V-type notch where the crack is just a special case. Further, numerical results give rules of stress distribution under various conditions.
3561
Authors: Jun Huang, Yong Jun Li, Fan Huang
Abstract: A numerical method is proposed for calculating the fractional order derivative and successfully resolving the integrand singularity problem based on Zhang-Shimizu algorithm. And then a method is developed to calculate the twice nonlinear fractional derivative, numerical examples demonstrate the numerical method with high precision and good stability.
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