Influences of generic payload and constraint force on modal analysis and dynamic responses of flexible manipulator
TL;DR: This article presents the dynamic modeling and nonlinear analysis of two-link flexible manipulator with generic payload whose center of gravity is different than the point of attachment with the generic payload.
Abstract: This article presents the dynamic modeling and nonlinear analysis of two-link flexible manipulator with generic payload whose center of gravity is different than the point of attachment with the li
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TL;DR: In this article , the effect of flexibility on the dynamics of a two-link planar manipulator having two revolute joints is investigated and a mathematical model validated through experiments is obtained.
Abstract: In this paper, the effect of flexibility on the dynamics of a two-link planar manipulator having two revolute joints is investigated. For this purpose, a mathematical model validated through experiments is obtained for a Two-link planar manipulator having two revolute joints . The mathematical model takes into account the continuous change of Eigen value due to change of configuration of the manipulator. A general expression for the frequency equation for the vibrating links has been obtained which is found to be time-dependent. The effect of this time-dependency of Eigen values of links on Joint and Tip responses is included in the assumed modes method. In this paper, the types of boundary conditions to be used for the flexible links are also researched upon and it is proposed that first four modes of vibration should be used for exactly modelling the flexible links .
5 citations
01 Mar 2022-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this paper, a blind-Kriging-based natural frequency prediction of the industrial robot is proposed, utilizing the Latin Hypercube Sampling (LHS) technique, and a reliable dataset with 120 samples is generated for surrogate models based on the FEM.
Abstract: High-precision assembly conditions tend to necessitate consideration of the vibration modes of industrial robots. The modal characteristics of complex systems such as industrial robots are highly nonlinear. It means that mechanics experiments and finite element methods (FEM) to evaluate such features are usually expensive. Surrogate models combined with simulation-based design are widely used in engineering issues. However, few investigations apply surrogate models to industrial robots' modal analysis. We propose a practical scheme, i.e., the Blind-Kriging (KRG-B) based natural frequency prediction of the industrial robot, utilizing the Latin Hypercube Sampling (LHS) technique. A reliable dataset with 120 samples is generated for surrogate models based on the FEM. Then, the fourteen surrogate models with different optimization algorithms are evaluated to identify the optimal model for the natural frequency. In addition, the accuracy and robustness of the optimal surrogate model are investigated under different training samples. KRG-B model has better robustness (good fitting accuracy for both higher and lower order modes) and higher computational efficiency (1.133 s, the shortest time among all models). The proposed scheme mapping robot's joint angle and the natural frequency offers a valuable basis for further studying dynamic characteristics in industrial robotics.
3 citations
TL;DR: One important aspect of the dynamic performance evaluation of a parallel manipulator is the elastodynamic analysis which calls for the calculation of the stiffness and mass matrices.
Abstract: One important aspect of the dynamic performance evaluation of a parallel manipulator is the elastodynamic analysis which calls for the calculation of the stiffness and mass matrices. In the elastod...
1 citations
TL;DR: In this paper , a nonlinear saturation-based control method was proposed to suppress the primary resonance of a flexible manipulator considering complicated rigid-flexible coupling and modal coupling.
Abstract: When primary resonance occurs, even a small external disturbance can abruptly excite large amplitude vibration and deteriorate the working performance of a flexible manipulator. Most active control methods are effective for non-resonant vibration but not for primary resonance. In view of this, this paper puts forward a new nonlinear saturation-based control method to suppress the primary resonance of a flexible manipulator considering complicated rigid-flexible coupling and modal coupling. A vibration absorber with variable stiffness/damping is designed to establish an energy exchange channel for saturation. A novel idea of modal coupling enhancement is suggested to improve saturation performance by strengthening the coupling relationship between the mode of the vibration absorber and the controlled mode of the flexible manipulator. Through stability analysis on the primary resonance response of the flexible manipulator with the vibration absorber, the saturation mechanism is successfully established and the effectiveness of the saturation control algorithm is validated. On this basis, several important indexes are extracted and employed to optimize saturation control. Finally, a series of virtual prototyping simulations and experiments are conducted to verify the feasibility of the suggested saturation-based control method. This research will contribute to the primary resonance suppression of a flexible manipulator under a complex external excitation environment.
1 citations
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TL;DR: A technique is presented and experimentally validated for solving the inverse dynamics and kinematics of multi-link flexible robots and shows the potential use of this method not only for open-loop control, but also for incorporation in feedback control strate gies.
Abstract: A technique is presented and experimentally validated for solving the inverse dynamics and kinematics of multi-link flexible robots. The proposed method finds the joint torques necessary to produce a specified end-effector motion. Since the inverse dynamic problem in elastic manipulators is closely coupled to the inverse kinematic problem, the solution of the first also renders the displacements and rotations at any point of the manipulator, including the joints. Further more the formulation is complete in the sense that it includes all the nonlinear terms due to the large rotation of the links. The Timoshenko beam theory is used to model the elastic characteristics, and the resulting equations of motion are discretized using the finite element method. An iterative solu tion scheme is proposed that relies on local linearization of the problem. The solution of each linearization is carried out in the frequency domain.The performance and capabilities of this technique are tested, first through simulation an...
222 citations
Additional excerpts
...The nonlinear dynamic equation of motion of a multi-link flexible manipulator using principle of virtual displacements has been derived by Bayo et al. (1989)....
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TL;DR: In this paper, the coupled nonlinear mechanical behavior of extensible functionally graded microbeams, when both viscoelasticity and imperfection are present, is investigated, using the Euler-Bernoulli strain-displacement relations.
123 citations
"Influences of generic payload and c..." refers background in this paper
...For sake of simplicity, longitudinal motions of links are neglected while geometric nonlinearity arising due to axial stretching (Ghayesh and Amabili 2013; Ghayesh, Farokhi, and Alici 2015; Farokhi and Ghayesh 2017; Ghayesh 2018, 2012), coupled nonlinear and rotational terms in Eqs....
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TL;DR: In this paper, a method for deriving dynamic equations for manipulators containing both rigid and flexible links using Hamilton's principle is presented. But the approach is a natural extension of the well-known Lagrangian method for rigid manipulators.
Abstract: This paper presents a procedure for deriving dynamic equations for manipulators containing both rigid and flexible links. The equations are derived using Hamilton's principle, and are nonlinear integro-differential equations. The formulation is based on expressing the kinetic and potential energies of the manipulator system in terms of generalized coordinates. In the case of flexible links, the mass distribution and flexibility are taken into account. The approach is a natural extension of the well-known Lagrangian method for rigid manipulators. Properties of the dynamic matrices, which lead to a less computation, are shown. Boundary-value problems of continuous systems are briefly described. A two-link manipulator with one rigid link and one flexible link is analyzed to illustrate the procedure.
106 citations
"Influences of generic payload and c..." refers background in this paper
...Low and Vidyasagar (1988) presented the dynamic modeling of a two-link manipulator by applying Lagrangian approach and introducing a density form for distributed mass and flexibility in links....
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TL;DR: In this paper, an axially moving visco-elastic Rayleigh beam with cubic nonlinearity is considered, and the governing partial-differential equation of motion for large amplitude vibration is derived through geometrical, constitutive, and dynamical relations.
101 citations
"Influences of generic payload and c..." refers methods in this paper
...(13) and (14), method of multiple scales (Cederbaum 1992; Ghayesh 2010; Ghayesh and Balar 2008; Ghayesh and Moradian 2011; Ghayesh, Kazemirad, and Reid 2012; Xu and Yang 2015) is used....
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TL;DR: In this paper, the axial speed of an axially accelerating string guided by a non-linear elastic foundation is analyzed analytically and the stability of the system is constructed.
Abstract: Parametric vibrations and stability of an axially accelerating string guided by a non-linear elastic foundation are studied analytically. The axial speed, as the source of parametric vibrations, is assumed to involve a mean speed, along with small harmonic variations. The method of multiple scales is applied to the governing non-linear equation of motion and then the natural frequencies and mode shape equations of the system are derived using the equation of order one, and satisfying the compatibility conditions. Using the equation of order epsilon, the solvability conditions are obtained for three distinct cases of axial acceleration frequency. For all cases, the stability areas of system are constructed analytically. Finally, some numerical simulations are presented to highlight the effects of system parameters on vibration, natural frequencies, frequency–response curves, stability, and bifurcation points of the system.
80 citations
"Influences of generic payload and c..." refers methods in this paper
...(13) and (14), method of multiple scales (Cederbaum 1992; Ghayesh 2010; Ghayesh and Balar 2008; Ghayesh and Moradian 2011; Ghayesh, Kazemirad, and Reid 2012; Xu and Yang 2015) is used....
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