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: In this paper, the dynamical response of axially moving, partially supported, stretched viscoelastic belts is investigated analytically in the Kelvin-Voigt model, where the tension in the belt span is assumed to vary periodically over a mean value (as it occurs in real mechanisms).
Abstract: The dynamical response of axially moving, partially supported, stretched viscoelastic belts is investigated analytically in this paper. The Kelvin–Voigt viscoelastic material model is considered and material, not partial, time derivative is employed in the viscoelastic constitutive relation. The string is considered as a three part system: one part resting on a nonlinear foundation and two that are free to vibrate. The tension in the belt span is assumed to vary periodically over a mean value (as it occurs in real mechanisms), and the corresponding equation of motion is derived by applying Newton’s second law of motion for an infinitesimal element of the string. The method of multiple scales is applied to the governing equation of motion, and nonlinear natural frequencies and complex eigenfunctions of the system are obtained analytically. Regarding the resonance case, the limit-cycle of response is formulated analytically. Finally, the effects of system parameters such as axial speed, excitation characteristics, viscousity and foundation modulus on the dynamical response, natural frequencies and bifurcation points of system are presented.
80 citations
TL;DR: In this paper, the authors investigated the nonlinear dynamics of an axially accelerating beam using the Galerkin scheme, which reduced the equation of motion to a set of nonlinear ordinary differential equations with coupled terms, and solved the linear part of this set of equations to determine the linear natural frequencies.
Abstract: Geometrically nonlinear dynamics of an axially accelerating beam is investigated numerically in this paper. Employing the Galerkin scheme, the equation of motion is reduced to a set of nonlinear ordinary differential equations with coupled terms. The linear part of this set of equations is then solved to determine the linear natural frequencies. The frequency of the axial acceleration is set to twice the first or second linear natural frequency (subharmonic resonance), and bifurcation diagrams of Poincare maps are obtained via direct time integration and choosing the amplitude of the speed variations as a bifurcation parameter. The results are presented for four different values of the mean value of the axial speed, specifically in the form of time traces, phase-plane portraits, fast Fourier transforms (FFTs), and Poincare maps.
79 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: A general form of an analytical solution algorithm for the nonlinear vibrations and stability of parametrically excited continuous systems with intermediate concentrated elements is developed in this paper, where the method of multiple timescales is applied directly to the equations of the motion which are in the form of a set of nonlinear partial differential equations with nonlinear coupled terms.
77 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 effect of link flexibility on the dynamic stability of a two-link force-controlled robot manipulator was investigated, and it was shown that the link flexibility is an important source of dynamic instability in the motion of force controlled manipulators.
Abstract: This study investigates the effect of link flexibility on the dynamic stability of a two-link force-controlled robot manipulator. The nonlinear open-loop equations for the compliant motion are derived first. By employing the hybrid force/position control law, the closed-loop dynamic equations are then explicitly derived. The nonlinear closed-loop equations are linearized about some equilibrium configurations. Stability analyses are carried out by computing the eigenvalues of the linearized system equations. Results are verified by the numerical simulations using the complete nonlinear dynamic equations. The effect of the wrist force sensor stiffness on the dynamic stability is also investigated. Results show that the link flexibility is indeed an important source of dynamic instability in the motion of force-controlled manipulators. Moreover, the system stability is dominated by the effect of the distributed flexibility of the first link.
70 citations
"Influences of generic payload and c..." refers background in this paper
...The effect of link flexibility on dynamic stability of a two-link force controlled robot manipulator carrying no payload has been investigated in Chiou and Shahinpoor (1990)....
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TL;DR: In this paper, two variables of joint angle and elastic deformation are partly decoupled by a nonlinear decoupling feedback control method and an extended state observer is introduced to estimate nonlinear terms of the two-link flexible manipulator system.
69 citations
"Influences of generic payload and c..." refers background in this paper
...Yang et al. (2015) designed a nonlinear controller for trajectory tracking control of a two-link flexible manipulator model in space....
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