Dynamic Performance Study of Stewart Parallel Mechanism Based on Natural Frequency

2014 ◽  
Vol 635-637 ◽  
pp. 1246-1250 ◽  
Author(s):  
Bang Jun Lv ◽  
Li Kun Peng ◽  
Jia Chen
Keyword(s):  
Natural Frequency ◽  
Parallel Mechanism ◽  
Dynamic Performance ◽  
Transmission Mechanism ◽  
Local Dynamic ◽  
Performance Study ◽  
Performance Indices ◽  
Inertia Parameters ◽  
Moving Platform ◽  
Variation Trends

The stiffness of transmission mechanism, assembled joints and moving platform, the compressibility of oil, and the load inertia of hydraulic Stewart mechanism will cause synthetically mechanical and hydraulic resonance problems, which will directly influence the system dynamic performance. The natural frequency and local dynamic isotropy index are adopted to evaluate dynamic performance. The variation trends of performance indices with configuration and inertia parameters are analyzed, and general optimal design rules and conclusions are obtained.

Elastodynamics modeling of 4-SPS/CU parallel mechanism with flexible moving platform based on absolute nodal coordinate formulation

2017 ◽  
Vol 232 (21) ◽  
pp. 3843-3858 ◽  
Author(s):  
Gengxiang Wang
Keyword(s):  
Coordinate System ◽  
Parallel Mechanism ◽  
Absolute Nodal Coordinate Formulation ◽  
Dynamic Performance ◽  
Flexible Body ◽  
Surface Approach ◽  
Absolute Nodal Coordinate ◽  
Cylindrical Joint ◽  
Moving Platform ◽  
Joint Coordinate System

The moving platform of the 4-SPS/CU (S is the spherical joint, P is the prismatic joint, C is the cylindrical joint, U is the universal joint) parallel mechanism is treated as a thin-plate element based on the absolute nodal coordinate formulation due to its physical characteristic. In order to eliminate high-frequency modes caused by the coupling between membrane and bending effects, the elastic mid-surface approach is used to evaluate the elastic force of the flexible moving platform. In order to formulate constraint equations between the flexible body and the rigid body, the tangent frame is introduced to define the joint coordinate system that is rigidly attached to the node at the joint, which is convenient for determining the constant vector in the joint coordinate system. The dynamics model of the parallel mechanism with the flexible moving platform is built based on the equation of motion. The simulation results show that the vibration frequency caused by the flexible body will be increased with the increasing stiffness of the material, and the kinematic trajectory and dynamics performance of the parallel mechanism are affected seriously when the smaller Young’s modulus is used, which illustrates that the effect of the flexible moving platform on the dynamic performance of the parallel mechanism should not be ignored.

Dynamics Model of 4-SPS/CU Parallel Mechanism With Spherical Clearance Joint and Flexible Moving Platform

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Gengxiang Wang ◽  
Hongzhao Liu
Keyword(s):  
Parallel Mechanism ◽  
Dynamic Performance ◽  
Friction Model ◽  
Contact Forces ◽  
Flexible Body ◽  
Force Model ◽  
Spherical Joint ◽  
Dynamics Model ◽  
Clearance Joint ◽  
Moving Platform

Effects of flexible body and clearance spherical joint on the dynamic performance of 4-SPS/CU parallel mechanism are analyzed. The flexible moving platform is treated as thin plate based on absolute nodal coordinate formulation (ANCF). In order to formulate the parallel mechanism's constraint equations between the flexible body and the rigid body, the tangent frame is introduced to define the joint coordinate. One of the spherical joints between moving platform and kinematic chains is introduced into clearance. The normal and tangential contact forces are calculated based on Flores contact force model and modified Coulomb friction model. The dynamics model of parallel mechanism with clearance spherical joint and flexible moving platform is formulated based on equation of motion. Simulations show that the dynamic performance of parallel mechanism is not sensitive to the flexible body because of the inherent property of moving platform; however, when the clearance spherical joint is considered into the parallel mechanism with flexible body, the flexible moving platform exhibits cushioning effect to absorb the energy caused by clearance joint.

Stiffness Optimization of redundant mechanism based on elastic coupling and inertial coupling characteristics

2021 ◽  
pp. 1-29
Author(s):  
Xiao-Jin Wan ◽  
Dengfeng Jia
Keyword(s):  
Natural Frequency ◽  
Parallel Mechanism ◽  
Virtual Work ◽  
Structural Parameters ◽  
Dynamic Performance ◽  
Algebraic Solution ◽  
Elastic Coupling ◽  
Inertial Coupling ◽  
Two Indices ◽  
Redundant Mechanism

Abstract Aiming to redundant parallel mechanism, on the basis of the kinetic energy method, virtual work principle and perturbation method, the generalized mass matrix and generalized stiffness matrix are obtained, respectively. Two indices on inertial coupling and elastic coupling are defined to measure the decoupling level of the redundant parallel mechanism in terms of two generalized matrices. Furthermore, an algebraic solution method for natural frequency equation of the mechanism is utilized to obtain the natural frequency by means of the Cholesky decomposition method. And then, in order to minimize inertial coupling and elastic coupling, and maximize the natural frequency of the mechanism, two indices and natural frequency are taken as objective functions to optimize the structural parameters of the redundant mechanism, so that optimal dynamic performance of the mechanism is acquired. In the optimization of natural frequency, two optimal solutions are selected. One is to consider inertial coupling and elastic coupling and the other is to ignore inertial coupling and elastic coupling. Finally, the dynamic performance of the two indexes is better by comparing the dexterity of the two solutions

KINEMATICS AND WORKSPACE ANALYSIS OF A 3 DEGREE OF FREEDOM PARALLEL MECHANISM WITH PARALLELOGRAM LINKAGE

2017 ◽  
Vol 41 (5) ◽  
pp. 922-935
Author(s):  
HongJun San ◽  
JunSong Lei ◽  
JiuPeng Chen ◽  
ZhengMing Xiao ◽  
JunJie Zhao
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Analytical Method ◽  
Theoretical Basis ◽  
Parallel Mechanism ◽  
Graphical Method ◽  
Degree Of Freedom ◽  
Workspace Analysis ◽  
Fixed Base ◽  
Moving Platform

In this paper, a 3-DOF translational parallel mechanism with parallelogram linkage was studied. According to the space vector relation between the moving platform and the fixed base, the direct and inverse position solutions of this mechanism was deduced through analytical method. In addition, the error of the algorithm was analyzed, and the algorithm had turned out to be effective and to have the satisfactory computational precision. On the above basis, the workspace of this mechanism was found through graphical method, which was compared with that of finding through Monte Carlo method, and there was the feasibility for analyzing the workspace of the mechanism by graphical method. The characteristic of the mechanism was analyzed by comparing the results of two analysis methods, which provided a theoretical basis for the application of the mechanism.

Dynamics of a Two-DOF Parallel Pointing Mechanism

2005 ◽  
Author(s):  
Alessandro Cammarata ◽  
Rosario Sinatra
Keyword(s):  
Numerical Simulation ◽  
Parallel Mechanism ◽  
Inverse Dynamics ◽  
Kinematic Model ◽  
Degree Of Freedom ◽  
Numerical Examples ◽  
Proposed Model ◽  
Dynamic Analyses ◽  
Moving Platform ◽  
Two Degree Of Freedom

This paper presents kinematic and dynamic analyses of a two-degree-of-freedom pointing parallel mechanism. The mechanism consists of a moving platform, connected to a fixed platform by two legs of type PUS (prismatic-universal-spherical). At first a simplified kinematic model of the pointing mechanism is introduced. Based on this proposed model, the dynamics equations of the system using the Natural Orthogonal Complement method are developed. Numerical examples of the inverse dynamics results are presented by numerical simulation.

The Parallel Mechanism and Variable Acceleration Control Method

2013 ◽  
Vol 579-580 ◽  
pp. 659-664
Author(s):  
Xiang Bo Ouyang ◽  
Ke Tian Li ◽  
Hong Jian Xia ◽  
Su Juan Wang ◽  
Huan Wei Zhou ◽  
...  
Keyword(s):  
Parallel Mechanism ◽  
Control Method ◽  
The Other ◽  
Connecting Rod ◽  
Motion Platform ◽  
The Third ◽  
Symmetric Structure ◽  
Slide Block ◽  
Operation Process ◽  
Moving Platform

t presents the parallel mechanism and variable acceleration control method, which is composed of slider, connecting rod, moving platform and linear guide etc. The motion platform is supported by three connecting rods through hinging, the other end of the connecting rods are respectively hinged with two sliders. Among them two pairs of connecting rod, two sliders and the moving platform formed a symmetric structure that is the so called Parallel Mechanism. The third connecting rod is parallel to one of two connecting rods, so that the two parallel connecting rods, slide block and the moving platform formed a parallelogram structure, it makes that the moving platform is always parallel to liner guiderail in the process of movement. By controlling the two sliders moving in the way of variable acceleration, it can make the trajectory curve, speed curve and acceleration curve of the moving platform are continuous, smooth, so impact and vibration of the moving platform is limited in the operation process.

Modelling of the whole process of a university campus CHP power plant and dynamic performance study

2016 ◽  
Vol 13 (1) ◽  
pp. 53-63 ◽  
Author(s):  
Yue Wang ◽  
Akmaral Bermukhambetova ◽  
Ji-Hong Wang ◽  
Mark Donner ◽  
Jun-Fu Lv ◽  
...  
Keyword(s):  
Power Plant ◽  
Dynamic Performance ◽  
University Campus ◽  
Performance Study ◽  
Whole Process
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