Elastodynamic Model-Based Vibration Characteristics Prediction of a Three Prismatic–Revolute–Spherical Parallel Kinematic Machine

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Jun Zhang ◽  
Yan Q. Zhao ◽  
Marco Ceccarelli
Keyword(s):  
Dynamic Characteristics ◽  
Lower Order ◽  
High Speed ◽  
Natural Frequencies ◽  
Eigenvalue Decomposition ◽  
Design Stage ◽  
Response Analysis ◽  
Early Design Stage ◽  
Synthesis Strategy ◽  
Parallel Kinematic

Parallel kinematic machines (PKMs) have been proposed as an alternative solution for high-speed machining (HSM) tool for several years. However, their dynamic characteristics are still considered an issue for practice application. Considering the three prismatic–revolute–spherical (3-PRS) PKM design as a typical compliant parallel device, this paper applies substructure synthesis strategy to establish an analytical elastodynamic model for the device. The proposed model considers the effects of component compliances and kinematic pair contraints so that it can predict the dynamic characteristics of the 3-PRS PKM. Based on eigenvalue decomposition of the characteristic equations, the natural frequencies and corresponding vibration modes at a typical configuration are analyzed and verified by numerical simulations. With an algorithm of workspace partitions combining with eigenvalue decompositions, the distributions of lower-order natural frequencies throughout the workspace are computed to reveal a strong dependency of dynamic characteristics on mechanism's configurations. In addition, the effects of the radii of the platform and the base along with the cross section of the limb on lower-order natural frequencies are analyzed to provide useful information during the early design stage. At last, frequency response analysis for the tool center point (TCP) is worked out based on the elastodynamic model to provide primary guideline for cutting chatter avoidance.

Characteristic Equation-Based Dynamic Analysis of a Three-Revolute Prismatic Spherical Parallel Kinematic Machine

2015 ◽  
Vol 10 (2) ◽  
Author(s):  
Jun Zhang ◽  
Jian S. Dai ◽  
Tian Huang
Keyword(s):  
Dynamic Model ◽  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Eigenvalue Decomposition ◽  
Mode Shapes ◽  
Design Parameters ◽  
Parallel Kinematic Machine ◽  
Characteristic Equations ◽  
Parallel Kinematic ◽  
Compliance Model

A three-revolute prismatic spherical (3-RPS) parallel kinematic machine (PKM) module is proposed as an alternative solution for high-speed machining (HSM) tool. Considering the PKM as a typical compliant parallel device, whose three limb assemblages have bending, extending, and torsional deflections, this paper applies screw theory to establish an analytical compliance model for the device. The developed compliance model is then combined with the energy method to deduce a comprehensive dynamic model of the 3-RPS module. The solution for the characteristic equations of the dynamic model leads to the modal properties of the PKM module. Based on the eigenvalue decomposition of the characteristic equations, a modal analysis is conducted. The natural frequencies and corresponding mode shapes at typical and nontypical configurations are analyzed and compared with finite element analysis (FEA) results. With an algorithm of workspace partitions combining with eigenvalue decompositions, the distributions of natural frequencies throughout the workspace are predicted to reveal a strong dependency of dynamic characteristics on mechanism's configurations. At the last stage, the effects of some design parameters on system dynamic characteristics are investigated with the purpose of providing useful information for the conceptual design and performance improvement for the PKM.

Application of Pseudo-Random Test Signals and Cross Correlation to the Identification of Bulk Handling Plant Dynamic Characteristics

1973 ◽  
Vol 95 (1) ◽  
pp. 31-36 ◽  
Author(s):  
A. W. Roberts ◽  
W. H. Charlton
Keyword(s):  
Dynamic Characteristics ◽  
Cross Correlation ◽  
Natural Frequencies ◽  
Statistical Technique ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Grain Handling ◽  
Extraneous Noise ◽  
Cross Correlation Analysis

In the determination of the dynamic characteristics of bulk handling systems the complexity of the problem usually makes experimental identification necessary. Experimental techniques which are based on statistical methods are known to be more reliable than conventional methods such as frequency response analysis. A statistical technique that employs a pseudo-random binary coded signal (prbs) to perturbate the system followed by cross correlation analysis may be used very effectively to identify the dynamic characteristics of the system even in the presence of extraneous noise signals. This paper describes this technique and discusses its application to two areas in the bulk handling field; the first deals with the determination of the natural frequencies of screw conveyors used for grain handling and the second deals with the identification of the dynamic characteristics of grain discharge chutes.

Optimum Design of Radial-Flow Impellers

1989 ◽  
Vol 203 (4) ◽  
pp. 229-232
Author(s):  
G S Ray ◽  
B K Sinha ◽  
S Majumdar
Keyword(s):  
Optimum Design ◽  
Centrifugal Force ◽  
Computer Aided Design ◽  
High Speed ◽  
Radial Flow ◽  
Design Stage ◽  
Early Design ◽  
Early Design Stage ◽  
Computer Aided ◽  
Aided Design

The paper presents a procedure of computer aided design of high-speed impellers. The configurations are obtained using programs for the strength under the influence of centrifugal force within given constraints. The method provides a tool for optimizing stresses at an early design stage.

Maneuvering Predictions for Fast Monohulls in Early Design Stage

2015 ◽  
Author(s):  
F.H.H.A. Quadvlieg ◽  
F. van Walree ◽  
V. Barthelemy
Keyword(s):  
High Speed ◽  
Model Tests ◽  
Design Stage ◽  
Correct Prediction ◽  
Design Assessment ◽  
Early Design ◽  
Early Design Stage ◽  
Directional Stability ◽  
Pros And Cons ◽  
The Time Domain

The present paper discusses directional stability and course keeping of fast monohulls. Model tests and CFD were used for analysis. In itself these are great tools, but in early design stage they are often perceived as too elaborate. In comparison, design verification is often carried out during model testing., However, it is not common to use these model tests for systematic variation or multiple design variations. In addition to model tests, tools for early design assessment are also pursued. By using a 3D panel method, maneuvering coefficients and subsequently directional stability are found in an earlier stage of the design. The present paper describes which methods can be used in the design stage, and some pros and cons of these methods. A method of choice is selected and an example is elaborated. The example ship is a high speed monohull (Fn=0.8) propelled by waterjets. This paper illustrates that the forces acting on the ship while performing forced motions are predicted. A next step (not in the present paper) is to solve the equations of motions in the time domain as a system of ordinary differential equations. However, in order to correctly predict the motions and trajectories, the correct prediction of forces and moments is essential

Dynamic Characteristics Analysis and Topology Optimization of Column Based on Finite Element Method

2013 ◽  
Vol 721 ◽  
pp. 541-544
Author(s):  
Jing Chen ◽  
Ze Long Yang ◽  
Xian Xuan Li
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Frequency Response ◽  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Response Analysis ◽  
Response Curves ◽  
Element Analysis ◽  
Column Structure

Aiming to improve the dynamic and static characteristics of a type of machining center column, the finite element modal analysis and harmonic response analysis of the column are performed, and this paper analyzes the dynamic characteristics of the column based on the first five mode shapes and natural frequencies of the column and the displacement - frequency response curves of the column. Topology optimization analysis of the column is performed with ANSYS, and the finite element analysis is performed on the column again after the column structure is improved based on the optimal distribution of material of the column structure and the design experience of column. The result shows that the first five natural frequencies of the column increase, the peak of the displacement - frequency response of the column decrease, and the dynamic characteristics are improved significantly.

Elastodynamic Modeling and Analysis for an Exechon Parallel Kinematic Machine

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Jun Zhang ◽  
Yan Q. Zhao ◽  
Yan Jin
Keyword(s):  
Differential Equations ◽  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Structural Features ◽  
Parallel Kinematic Machine ◽  
Dynamic Behaviors ◽  
Elastodynamic Modeling ◽  
Parallel Kinematic ◽  
Moving Platform

As a newly invented parallel kinematic machine (PKM), Exechon has attracted intensive attention from both academic and industrial fields due to its conceptual high performance. Nevertheless, the dynamic behaviors of Exechon PKM have not been thoroughly investigated because of its structural and kinematic complexities. To identify the dynamic characteristics of Exechon PKM, an elastodynamic model is proposed with the substructure synthesis technique in this paper. The Exechon PKM is divided into a moving platform subsystem, a fixed base subsystem and three limb subsystems according to its structural features. Differential equations of motion for the limb subsystem are derived through finite element (FE) formulations by modeling the complex limb structure as a spatial beam with corresponding geometric cross sections. Meanwhile, revolute, universal, and spherical joints are simplified into virtual lumped springs associated with equivalent stiffnesses and mass at their geometric centers. Differential equations of motion for the moving platform are derived with Newton's second law after treating the platform as a rigid body due to its comparatively high rigidity. After introducing the deformation compatibility conditions between the platform and the limbs, governing differential equations of motion for Exechon PKM are derived. The solution to characteristic equations leads to natural frequencies and corresponding modal shapes of the PKM at any typical configuration. In order to predict the dynamic behaviors in a quick manner, an algorithm is proposed to numerically compute the distributions of natural frequencies throughout the workspace. Simulation results reveal that the lower natural frequencies are strongly position-dependent and distributed axial-symmetrically due to the structure symmetry of the limbs. At the last stage, a parametric analysis is carried out to identify the effects of structural, dimensional, and stiffness parameters on the system's dynamic characteristics with the purpose of providing useful information for optimal design and performance improvement of the Exechon PKM. The elastodynamic modeling methodology and dynamic analysis procedure can be well extended to other overconstrained PKMs with minor modifications.

Simulation Analysis on Dynamic Performance of Drilling Shaft Mechanism in PCB CNC Drilling Machine

2010 ◽  
Vol 44-47 ◽  
pp. 637-640
Author(s):  
Yong Shan Xiao ◽  
Fu Min Song ◽  
Zhen Yu Zhao
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Natural Frequencies ◽  
Simulation Analysis ◽  
Mode Shapes ◽  
Response Analysis ◽  
Drilling Machine ◽  
Finite Element Software ◽  
Shaft System ◽  
The Impact

The development of PCB CNC drilling machine is toward high-precision and high-speed, and the impact of the join cannot be ignored. Based on the finite element software, the finite element model of the drilling shaft system including the joins is established; the modal analysis and the frequency response analysis are performed on the drilling shaft system, the natural frequencies and mode shapes are obtained; the effect of the different parameters on the natural frequencies is analyzed, and the basic data can be obtained from the analysis.

A Dynamics Workstation

1989 ◽  
Author(s):  
J. K. Wu ◽  
M. A. Fogle ◽  
J. Y. Wang ◽  
J. K. Lu
Keyword(s):  
Mechanical System ◽  
Dynamic Simulation ◽  
High Speed ◽  
Mechanical Systems ◽  
Design Stage ◽  
Design System ◽  
Design Quality ◽  
Modeling Tool ◽  
Early Design Stage ◽  
System Models

Abstract The engineer’s modeling capability is the weakest link in the chain that supports the simulation of dynamic mechanical systems, due to the fact that engineers are forced to define mechanical system models in a way they are not familiar with. Advanced developments in computer techniques, computer graphics, and recursive computational algorithms for mechanical systems make the high speed dynamic simulation and graphic animation of mechanical systems feasible. But without a practical, useful modeling tool, the engineer has difficulty in using these advanced techniques. The Dynamics Workstation is a modeling tool developed to help the engineer define mechanical system models in a natural, practical way. The engineer can communicate with the workstation naturally and interactively, define the model in formats that meet the needs for both high speed dynamic simulation and conventional dynamic analysis, define and assemble the model body by body using a relative coordinate system, visualize the configuration of the model, carry out simple joint exercises to detect the errors of the model in the early design stage, graphically lock and unlock joints, and adjust the system configuration even after initial assembly. The workstation automatically generates the mechanical system model based on the engineer’s interactive input data. The model design system strengthens the engineer’s modeling capability; it not only improves the design quality, but also boosts productivity.

ROTOR RESONANCES ANALYSES OF HIGH-SPEED HIGH POWER PERMANENT-MAGNET ELECTRICAL MACHINES

2021 ◽  
pp. 95-108
Author(s):  
Wedad Alsadiq Alhawil ◽  
Ali A. Mehna ◽  
Asheraf Eldieb ◽  
Tarak Assaleh
Keyword(s):  
Finite Element ◽  
Permanent Magnet ◽  
High Speed ◽  
Natural Frequencies ◽  
Design Stage ◽  
Design Parameters ◽  
Element Analysis ◽  
Finite Element Program ◽  
Element Program ◽  
The Impact

High-speed electric machines (HSEMs) have been widely used in many of today’s applications.  For high-speed machines, in particular, it is very important to accurately predict natural frequencies of the rotor at the design stage to minimize the likelihood of failure. The main goal of this study is examine the design issues and performance of high-speed machines. For permanent-magnet synchronous motors (PMSM) driven by high-frequency drives, the rotor speed is normally above 30 000 rpm and it may exceed 100 000 rpm.  This study examined a 7-kw permanent magnet synchronous machine at 200,000 rpm. 3D finite element analysis (ANSYS WORKBENCH 15) was conducted to determine the natural frequencies and rotor patterns of a synchronous high-speed permanent magnetic motor, to assess the impact of leading design parameters, such as length, column diameter, span, bearings, material properties, and to compare the results of the finite element program with the results of analytical methods (i.e. critical speed).

scholarly journals Dimensionless Numerical Approaches for the Performance Prediction of Marine Waterjet Propulsion Units

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Marco Altosole ◽  
Giovanni Benvenuto ◽  
Massimo Figari ◽  
Ugo Campora
Keyword(s):  
Performance Prediction ◽  
High Speed ◽  
Design Stage ◽  
Propulsion Systems ◽  
Mixed Flow ◽  
Early Design Stage ◽  
Hydraulic Machines ◽  
Performance Map ◽  
Key Issues ◽  
Numerical Approaches

One of the key issues at early design stage of a high-speed craft is the selection and the performance prediction of the propulsion system because at this stage only few information about the vessel are available. The objective of this work is precisely to provide the designer, in the case of waterjet propelled craft, with a simple and reliable calculation tool, able to predict the waterjet working points in design and off-design conditions, allowing to investigate several propulsive options during the ship design process. In the paper two original dimensionless numerical procedures, one referred to jet units for naval applications and the other more suitable for planing boats, are presented. The first procedure is based on a generalized performance map for mixed flow pumps, derived from the analysis of several waterjet pumps by applying similitude principles of the hydraulic machines. The second approach, validated by some comparisons with current waterjet installations, is based on a complete physical approach, from which a set of non-dimensional waterjet characteristics has been drawn by the authors. The presented application examples show the validity and the degree of accuracy of the proposed methodologies for the performance evaluation of waterjet propulsion systems.

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