Analytical dynamics. L. A. Pars

Fundamentals of Vibrations

\n Flexure-based compliant mechanisms are becoming increasingly promising in precision engineering, robotics, and other applications due to the excellent advantages of no friction, no backlash, no wear, and minimal requirement of assembly. Because compliant mechanisms have inherent coupling of kinematic-mechanical behaviors with large deflections and/or complex serial-parallel configurations, the kinetostatic and dynamic analyses are challenging in comparison to their rigid-body counterparts. To address these challenges, a variety of techniques have been reported in a growing stream of publications. This paper surveys and compares the conceptual ideas, key advances, and applicable scopes, and open problems of the state-of-the-art kinetostatic and dynamic modeling methods for compliant mechanisms in terms of small and large deflections. Future challenges are discussed and new opportunities for extended study are highlighted as well. The presented review provides a guide on how to select suitable modeling approaches for those engaged in the field of compliant mechanisms.

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Kinetostatic and Dynamic Modeling of Flexure-Based Compliant Mechanisms: A Survey

Redundant actuation can improve the performance and ability of parallel manipulator. In order to deal with coordination and distribution of the driving force of the parallel manipulator with redundant actuation and to realize the control strategy based on dynamics, on the basis of the original 5UPS/PRPU parallel manipulator, it increases a drive for the middle PRPU passive constraint branch to make it a redundant actuation branch. It introduces configurations’ redundant types and compositions of 5UPS/PRPU parallel manipulator with redundant actuation, illustrates that the mechanism is redundant actuation from the perspective of degree of freedom and establishes a dynamic model based on Lagrangian method. On the basis of the weighted optimization principle of driving torque, it optimizes the driving torque of the parallel manipulator and calculates the driving force of the redundant driving chain with cutting force. It carries out the simulation by using ADAMS software and proves validity of dynamic model. Finally it detects the dynamic performance of the parallel manipulator by processing experiment of parallel manipulator with redundant actuation and its non-redundant counterpart.

Dynamic analysis and driving force optimization of a 5-DOF parallel manipulator with redundant actuation

This paper presents a comprehensive review of friction modelling to provide an understanding of design for durability within interacting systems. Friction is a complex phenomenon and occurs at the interface of two components in relative motion. Over the last several decades, the effects of friction and its modelling techniques have been of significant interests in terms of industrial applications. There is however a need to develop a unified mathematical model for friction to inform design for durability within the context of varying operational conditions. Classical dynamic mechanisms model for the design of control systems has not incorporated friction phenomena due to non-linearity behaviour. Therefore, the tribological performance concurrently with the joint dynamics of a manipulator joint applied in hazardous environments needs to be fully analysed. Previously the dynamics and impact models used in mechanical joints with clearance have also been examined. The inclusion of reliability and durability during the design phase is very important for manipulators which are deployed in harsh environmental and operational conditions. The revolute joint is susceptible to failures such as in heavy manipulators these revolute joints can be represented by lubricated conformal sliding surfaces. The presence of pollutants such as debris and corrosive constituents has the potential to alter the contacting surfaces, would in turn affect the performance of revolute joints, and puts both reliability and durability of the systems at greater risks of failure. Key literature is identified and a review on the latest developments of the science of friction modelling is presented here. This review is based on a large volume of knowledge. Gaps in the relevant field have been identified to capitalise on for future developments. Therefore, this review will bring significant benefits to researchers, academics and industry professionals.

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A review of friction models in interacting joints for durability design

Analysis of vibration effects on the comfort of intercity bus users by oscillatory model with ten degrees of freedom

Dynamic modelling of hydraulic excavator motion using Kane's equations

A new pseudo-rigid-body model approach for modeling the quasi-static response of planar flexure-hinge mechanisms

In this paper a new non-iterative computational technique referred to as the symbolic-numeric method of initial parameters (SNMIP) is proposed. The SNMIP represents a modification of the iterative numeric method of initial parameters in differential form known in the literature. The SNMIP is applied to study free vibrations of Euler-Bernoulli axially functionally graded tapered, stepped, and continuously segmented rods and beams with elastically restrained end with attached masses. Both the longitudinal vibration of rods and transverse vibration of beams are considered. The influence of the attached masses and springs on the natural frequencies of vibration of axially functionally graded rods and beams is examined. The validity and accuracy of the method are proven through the comparison with the known results in the available literature.

Free vibration analysis of axially functionally graded tapered, stepped, and continuously segmented rods and beams

This paper formulates and solves in closed form (expressed by elementary functions) the brachistochrone problem with Coulomb friction of a particle which moves down a rough curve in a uniform gravitational field assuming that the initial velocity of the particle is different from zero. The problem is solved by the application of variational calculus. Two variants are considered: first, the initial position and the final position of the particle are given; second, the initial position is given, and the final position lies on a given vertical straight line. The new approach in treating this problem by variational calculus lies in the fact that the projection sign of the normal reaction force of the rough curve onto the normal to the curve is introduced as the additional constraint in the form of an inequality. This inequality is transformed into an equality by introducing a new state variable. Although this is fundamentally a constrained variational problem, by further introducing a new functional with an expanded set of unknown functions, it is transformed into an unconstrained problem where broken extremals appear. Brachistochrone equations in parametric form are obtained for both variants which are examined, with the slope angle of the tangent to the brachistochrone being taken as the parameter. These equations contain a certain number of unknown constants which are determined from the corresponding systems of nonlinear algebraic equations. They are solved by an alternative approach which is based on the application of differential evolution. The obtained brachistochrones are generally two-segment curves with the initial line segment representing a free-fall parabola in nonresistant medium. It is shown that regarding the special values of the parameters the results of the paper coincide with the known results from literature.

Slaviša Šalinić

Papers

Analysis of vibration effects on the comfort of intercity bus users by oscillatory model with ten degrees of freedom

Dynamic modelling of hydraulic excavator motion using Kane's equations

A new pseudo-rigid-body model approach for modeling the quasi-static response of planar flexure-hinge mechanisms

Free vibration analysis of axially functionally graded tapered, stepped, and continuously segmented rods and beams

Contribution to the brachistochrone problem with Coulomb friction