337 research outputs found
Dynamics of a ferromagnetic granular system
No full textWe study theoretically and numerically the dynamics of a one-dimensional ferromagnetic granular system. Corresponding to different types of potential in the chain, linear, weakly nonlinear and strongly nonlinear partial differential equations are derived respectively. The continuum limit is derived following the method used by Ishimori (1982). Specifically, we show that by giving initial dynamic force, a system endure anharmonic nearest neighbor interaction (NNI) and inverse power-law long range interaction (LRI) will generate nonlinear solitary waves. Both weakly and strongly nonlinear equations occupied unique properties. Furthermore, we find that the equations of motion varies with different values of the exponent parameter p in each case. Next, we focus on the discussion of the dipole-dipole interaction which corresponds to the ferromagnetic system. We show that though the main contribution to the solitary wave is the short range part, the long-range interaction effect the shape of the solitary wave as well as its propagation velocity.M.S.Includes bibliographical referencesby Guanglei Zh
Multiobjective Optimum Design of a 3-RRR Spherical Parallel Manipulator with Kinematic and Dynamic Dexterities
No full textThis paper deals with the kinematic synthesis problem of a 3-underlineRRR spherical parallel manipulator, based on the evaluation criteria of the kinematic, kinetostatic and dynamic performances of the manipulator. A multiobjective optimization problem is formulated to optimize the structural and geometric parameters of the spherical parallel manipulator. The proposed approach is illustrated with the optimum design of a special spherical parallel manipulator with unlimited rolling motion. The corresponding optimization problem aims to maximize the kinematic and dynamic dexterities over its regular shaped workspace
Conceptual design and analysis of a 6-axis double delta robot towards high acceleration
No full textIn this paper, a 6-axis parallel robot for pick-and-place operations is introduced based on the double structures of the Delta robot. Differing from the current 6-axis Delta robot, all the actuators are mounted on a base platform, which can reduce the inertia for high dynamic performance. Besides the 3-axis translation of the Delta robot, this robot’s three rotations of the end-effector are realized by the relative movements of the two sub-platforms in three directions, but without significant structural complexity compared to the existing gearbox of Delta robot. The kinematic problems are studied to reveal that the workspace volume of the robot is similar to the existing design. The simplified dynamic model is established and the simulation results show that the robot can have the 100G acceleration maximally subject to the specifications of the current commercial actuator and gearbox.</p
Stiffness Analysis and Optimization of a Co-axial Spherical Parallel Manipulator
No full textThis paper investigates the stiffness characteristics of spherical parallel manipulators. By virtue of singular value decomposition, the 6x6 dimensionally inhomogeneous Cartesian stiffness matrix is transformed into two homogeneous ones, i.e., the rotational and translational stiffness matrices. The decomposed singular values and the corresponding vectors indicate the directions of high/weak stiffness and the stiffness isotropy for the manipulator at a given configuration. Two indices, one for rotation and the other for translation, are introduced to optimize the manipulator stiffness and to map the stiffness isocontours over the workspace to show an image of the overall stiffness
Kinematics and Dynamics of an Asymmetrical Parallel Robotic Wrist
No full textThis paper introduces an asymmetrical parallel robotic wrist, which can generate a decoupled unlimited-torsion motion and achieve high positioning accuracy. The kinematics, dexterity, and singularities of the manipulator are investigated to visualize the performance contours of the manipulator. Using the method of Lagrange multipliers and considering all the mobile components, the equations of motion of the manipulator are derived to investigate the dynamic characteristics efficiently. The developed dynamic model is numerically illustrated and compared with its simplified formulation to show its computation accuracy
Optimal structural design of a Biglide parallel drill grinder
No full textThis paper deals with the optimal structural design of a Biglide parallel grinder for drill grinding. A pair of spatial modules is adopted to replace the conventional parallelogram to enhance the out-of-plane stiffness of the latter. A multi-objective design optimization problem is formulated, of which the stiffness, motion/force transmission, and work space are taken into consideration. The Pareto front of the optimization problem is obtained to provide the optimum design of the Biglide machine, and a scatter matrix is visualized to reveal the influence of the link dimensions to the performance. The selected design from the Pareto front guarantees the requirement on the elastostatic performance in the grinding process with increased dexterous workspace size.</p
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