Topic
Direct stiffness method
About: Direct stiffness method is a research topic. Over the lifetime, 2584 publications have been published within this topic receiving 53131 citations.
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10 Nov 2003
TL;DR: This paper presents systematic methods to approach the conservative congruence transformation, CCT, via the geometrical analysis for the stiffness control transformation of serial manipulators via the CCT theory in the presence of external loads.
Abstract: This paper presents systematic methods to approach the conservative congruence transformation, CCT, via the geometrical analysis for the stiffness control transformation of serial manipulators. Through the strategy of changing basis, the 6/spl times/6 Cartesian stiffness of manipulators is shown to be basis dependent. The generalized formulation and symmetric property of the 6/spl times/6 Cartesian stiffness matrix are presented via the CCT theory in the presence of external loads. Examples of the serial manipulators are conducted to verify the conservative stiffness mapping.
25 citations
10 Apr 2007
TL;DR: A controller that adjusts stiffness of the elastic elements to reduce torque requirement of actuators while generating desired motions and Stability of the controller is proved, and tracking errors are guaranteed to converge to a certain region.
Abstract: This paper proposes a tracking control method of sinusoidal motions utilizing stiffness adjustment of mechanical elastic elements for serial link systems. Although dynamics of the controlled objects is nonlinear, the stiffness adjustment realize a condition similar to a resonance of linear systems. We present a controller that adjusts stiffness of the elastic elements to reduce torque requirement of actuators while generating desired motions. The proposed controller works without using dynamics models nor parameters of the controlled objects. Stability of the controller is proved, and tracking errors are guaranteed to converge to a certain region. Simulation results demonstrate the validity of the proposed method. We also present an application of the proposed method to power assist systems.
25 citations
TL;DR: In this article, the authors defined stiffness fields, stiffness lines, and stiffness decay vectors using newly introduced U* potential lines and showed that a load path can be expressed as a stiffness line that has a minimum stiffness decay vector.
Abstract: A concept of a parameter U* has been introduced by the authors to express load transfer paths in a structure. In this paper, matrix formulation of internal stiffness shows that the value of U* expresses a degree of connection between a loading point and an internal arbitrary point. Stiffness fields, stiffness lines, and stiffness decay vectors are defined using newly introduced U* potential lines. A concept of a load path can be expressed as a stiffness line that has a minimum stiffness decay vector. A simple model structure is calculated using FEM for an application of U* analysis. The distribution of U* values shows that a diagonal member between a loading point and a support point Plays an important rold for the load transfer.
25 citations
TL;DR: In this paper, a stiffness reduction method for the design of laterally restrained web-tapered steel structures fabricated through the welding of individual steel plates is presented, which is implemented through dividing tapered members into prismatic segments along their lengths, and reducing the flexural stiffness of each segment by means of the developed stiffness reduction functions considering the first-order forces and cross-section properties of each segments, performing Geometrically Nonlinear Analysis and making crosssection strength checks.
25 citations
TL;DR: In this paper, the stiffness and strength of multilayer beams (MBs) are calculated when the beam is deformed within elasticity limits, and the stiffness for bending and shear stresses at any point of the beam's cross section.
Abstract: This article describes an original method for calculating stiffness and strength of multilayer beams (MBs) when the beam is deformed within elasticity limits. It draws on previous studies by the same author, but for the first time fully describes the proposed method, both the theory and its practical application. This method is very useful for engineering calculations and scientific research. The equations obtained allow establishing the positions of neutral layers and of the geometric and stiffness centers when the cross section of the beam is not symmetric to both x- and y-axes. This study also presents the equations for establishing the stiffness for bending and shear, and for calculating normal and shear stresses at any point of the beam’s cross section. The efficiency and practical application of this new method are demonstrated by analyzing how MB stiffness and strength change depending on the influence of certain factors, such as mechanical properties of layers, number of layers, and their arrangem...
25 citations