A Vector Approach for Analytical Dynamics of a System of Rigid Bars

2019 ◽  
Vol 19 (08) ◽  
pp. 1950083
Author(s):  
Raman Goyal ◽  
Manoranjan Majji ◽  
Robert E. Skelton
Keyword(s):  
Virtual Work ◽  
Wrist Joint ◽  
Equations Of Motion ◽  
Analytical Mechanics ◽  
Analytical Dynamics ◽  
Principle Of Virtual Work ◽  
Angular Velocity Vector ◽  
Tensegrity Systems ◽  
Transcendental Functions ◽  
Vector Approach

An analytical mechanics approach to derive equations of motion from vector kinematic description of rigid bar assemblies is developed. It is shown that various holonomic constraints governing multibody mechanical systems can be modeled using vector kinematics without using trigonometric/transcendental functions. The principle of virtual work is utilized to derive a map between the generalized coordinates associated with the vector approach and the angular velocity vector associated with the rigid bars. The utility of the vector approach is demonstrated by deriving the dynamics of tensegrity systems and a carpal wrist joint.

Analytical Modelling of the Dynamics of the Four-Bar Mechanism: A Comparison of Some Methods

2018 ◽  
Author(s):  
J. P. Meijaard ◽  
V. van der Wijk
Keyword(s):  
Virtual Work ◽  
Equations Of Motion ◽  
Differential Algebraic Equations ◽  
Force Balance ◽  
Dynamic Force ◽  
Algebraic Equations ◽  
Principle Of Virtual Work ◽  
Principal Vector ◽  
Reaction Forces ◽  
Principal Points

Some thoughts about different ways of formulating the equations of motion of a four-bar mechanism are communicated. Four analytic methods to derive the equations of motion are compared. In the first method, Lagrange’s equations in the traditional form are used, and in a second method, the principle of virtual work is used, which leads to equivalent equations. In the third method, the loop is opened, principal points and a principal vector linkage are introduced, and the equations are formulated in terms of these principal vectors, which leads, with the introduced reaction forces, to a system of differential-algebraic equations. In the fourth method, equivalent masses are introduced, which leads to a simpler system of principal points and principal vectors. By considering the links as pseudorigid bodies that can have a uniform planar dilatation, a compact form of the equations of motion is obtained. The conditions for dynamic force balance become almost trivial. Also the equations for the resulting reaction moment are considered for all four methods.

Effect of the Gravity Force on the Propagation of a Rotating Flexible Rod After Impact

1997 ◽  
Author(s):  
Wei-Hsin Gau
Keyword(s):  
Elastic Waves ◽  
Virtual Work ◽  
Impact Load ◽  
Equations Of Motion ◽  
Fourier Method ◽  
Gravity Force ◽  
Principle Of Virtual Work ◽  
Shape Functions ◽  
Concentrated Force ◽  
The Impact

Abstract The aim of this paper is to analyze the effect of the gravity force on the impact-induced elastic waves which propagate on a radially rotating rod. The equations of motion of the system are developed using the principle of virtual work in dynamics. The impact load is included by the use of the generalized impulse momentum equations, involving the coefficient of restitution. The system is solved using the Fourier method. The deformation of the rod is supposed to be at any instant a linear combination of a set of shape functions. These shape functions are, in this investigation, the modes of a cantilever beam. The weight of the rod is modeled as a concentrated force applied at any instant at the center of the rod.

scholarly journals Generalized Lagrange-D’Alembert principle

2012 ◽  
Vol 91 (105) ◽  
pp. 49-58
Author(s):  
Djordje Djukic
Keyword(s):  
Dynamic Equilibrium ◽  
Virtual Work ◽  
Analytical Mechanics ◽  
Principle Of Virtual Work ◽  
Constraint Forces ◽  
Lagrange Equations ◽  
Virtual Displacement ◽  
Generalized Coordinates ◽  
D’Alembert Principle ◽  
Applied Forces

The major issues in the analysis of the motion of a constrained dynamic system are to determine this motion and calculate constraint forces. In the analytical mechanics, only the first of the two problems is analyzed. Here, the problem is solved simultaneously using: 1) Principle of liberation of constraints; 2) Principle of generalized virtual displacement; 3) Idea of ideal constraints; 4) Concept of generalized and ?supplementary" generalized coordinates. The Lagrange-D?Alembert principle of virtual work is generalized introducing virtual displacement as vectorial sum of the classical virtual displacement and virtual displacement in the ?supplementary" directions. From such principle of virtual work we derived Lagrange equations of the second kind and equations of dynamical equilibrium in the ?supplementary" directions. Constrained forces are calculated from the equations of dynamic equilibrium. At the same time, this principle can be used for consideration of equilibrium of system of material particles. This principle simultaneously gives the connection between applied forces at equilibrium state and the constrained forces. Finally, the principle is applied to a few particular problems.

Inverse dynamics of the 6-dof out-parallel manipulator by means of the principle of virtual work

Robotica ◽  
2009 ◽  
Vol 27 (2) ◽  
pp. 259-268 ◽  
Author(s):  
Yongjie Zhao ◽  
Feng Gao
Keyword(s):  
Parallel Manipulator ◽  
Inverse Dynamics ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Principle Of Virtual Work ◽  
Constraint Forces ◽  
Dynamical Equations ◽  
Robot System ◽  
Lead Screw ◽  
Moving Platform

SUMMARYIn this paper, the inverse dynamics of the 6-dof out-parallel manipulator is formulated by means of the principle of virtual work and the concept of link Jacobian matrices. The dynamical equations of motion include the rotation inertia of motor–coupler–screw and the term caused by the external force and moment exerted at the moving platform. The approach described here leads to efficient algorithms since the constraint forces and moments of the robot system have been eliminated from the equations of motion and there is no differential equation for the whole procedure. Numerical simulation for the inverse dynamics of a 6-dof out-parallel manipulator is illustrated. The whole actuating torques and the torques caused by gravity, velocity, acceleration, moving platform, strut, carriage, and the rotation inertia of the lead screw, motor rotor and coupler have been computed.

Solving the Inverse Dynamics of a Stewart-Gough Manipulator by the Principle of Virtual Work

1999 ◽  
Vol 122 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Lung-Wen Tsai
Keyword(s):  
Computational Algorithm ◽  
Inverse Dynamics ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Principle Of Virtual Work ◽  
Dynamical Equations ◽  
Jacobian Matrices ◽  
Systematic Methodology ◽  
Moving Platform

This paper presents a systematic methodology for solving the inverse dynamics of a Stewart-Gough manipulator. Based on the principle of virtual work and the concept of link Jacobian matrices, a methodology for deriving the dynamical equations of motion is developed. It is shown that the dynamics of the manipulator can be reduced to solving a system of six linear equations in six unknowns. A computational algorithm for solving the inverse dynamics of the manipulator is developed and several trajectories of the moving platform are simulated. [S1050-0472(00)00401-3]

scholarly journals Modeling and Analysis of a Large-Scale Double-Level Guyed Mast for Membrane Antennas

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Bingyan Li ◽  
Yuxuan Liu ◽  
Rongqiang Liu ◽  
Hongwei Guo ◽  
Qiang Cong ◽  
...  
Keyword(s):  
Large Scale ◽  
Virtual Work ◽  
Constitutive Relations ◽  
Equations Of Motion ◽  
Principle Of Virtual Work ◽  
Static Stiffness ◽  
Modeling And Analysis ◽  
Stiffness Matrices ◽  
Guyed Mast ◽  
Equivalent Mechanism

This paper proposes a double-level guyed membrane antenna for stiffness improvement of a large-scale tri-prism deployable mast using the collapsible tubular mast (CTM). Initially, the construction of the antenna and the modeling of the CTM boom are illustrated. Afterwards, the central mast with isosceles triangular cross section is mathematically equivalent to a continuum beam, in which the equations of motion and the constitutive relations are derived. Based on the equivalent central beam, the double-level guyed mast for the membrane antenna is modeled as a 2(3-SPS-S) mechanism, and then velocity Jacobian matrices and stiffness matrices of SPS branches are constructed. Additionally, the total stiffness matrix of the equivalent mechanism is derived with the principle of virtual work and then evaluated as an accurate approach. Finally, with the aim to improve the static stiffness of the double-level guyed mast, the numerical analysis using the Genetic Algorithm (GA) is carried out for optimizing the distribution of guys in terms of anchor positions and attachment heights.

Solving the Inverse Dynamics of Parallel Manipulators by the Principle of Virtual Work

1998 ◽  
Author(s):  
Lung-Wen Tsai
Keyword(s):  
Parallel Manipulator ◽  
Inverse Dynamics ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Parallel Manipulators ◽  
Principle Of Virtual Work ◽  
Dynamical Equations ◽  
Systematic Methodology ◽  
Stewart Gough Platform

Abstract This paper presents a systematic methodology for solving the inverse dynamics of parallel manipulators. Based on the principle of virtual work and the concept of link Jacobian matrices, a methodology for deriving the dynamical equations of motion is developed. It is shown that the dynamics of a parallel manipulator can be reduced to solving a system of six linear equations. To demonstrate the methodology, the dynamical equations of a Stewart-Gough platform are derived. A computer algorithm is developed and several different trajectories of the moving platform are simulated.

Introducing and Analyzing a Novel Three-Degree-of-Freedom Spatial Tensegrity Mechanism

2014 ◽  
Vol 9 (2) ◽  
Author(s):  
Bahman Nouri Rahmat Abadi ◽  
Mehrdad Farid ◽  
Mojtaba Mahzoon
Keyword(s):  
Virtual Work ◽  
Equations Of Motion ◽  
Translational Motion ◽  
Parallel Robot ◽  
Principle Of Virtual Work ◽  
Dynamical Equations ◽  
Spatial Mechanism ◽  
Gravitational Forces ◽  
Three Degree Of Freedom ◽  
Special Case

The objective of the present paper is to introduce and analyze a particular spatial mechanism as a modification of the Stewart robot. The three limbs of the Stewart parallel robot are replaced by springs. Three hydraulic actuators control translational motion of the mechanism. Kinematics of the mechanism is studied and its static equations are derived and for a special case where external and gravitational forces are neglected, an analytical solution is presented. Also, the principle of virtual work is employed to derive the equations of motion of the proposed mechanism. Based on the dynamical equations, the motion of the system is simulated.

Kinematic, Stiffness, and Dynamic Analyses of a Compliant Tensegrity Mechanism

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Bahman Nouri Rahmat Abadi ◽  
S. M. Mehdi Shekarforoush ◽  
Mojtaba Mahzoon ◽  
Mehrdad Farid
Keyword(s):  
Dynamic Characteristics ◽  
Stiffness Matrix ◽  
Analytical Procedure ◽  
Inverse Dynamics ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Degree Of Freedom ◽  
Principle Of Virtual Work ◽  
Numerical Examples ◽  
Dynamic Analyses

The objective of this study is to present an analytical procedure for analysis of a compliant tensegrity mechanism focusing on its stiffness and dynamic characteristics. The screw calculus is used to derive the static equations and stiffness matrix of a full degree-of-freedom tensegrity mechanism, and the equations of motion are derived based on the principle of virtual work. Finally, some numerical examples are solved for the inverse dynamics of the mechanism.

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