scholarly journals Kinetostatic analysis and solution classification of a class of planar tensegrity mechanisms

Robotica ◽  
2018 ◽  
Vol 37 (7) ◽  
pp. 1214-1224 ◽  
Author(s):  
P. Wenger ◽  
D. Chablat
Keyword(s):  
Static Equilibrium ◽  
Equilibrium Conditions ◽  
Geometric Conditions ◽  
Equilibrium Configurations ◽  
Groebner Base ◽  
Systematic Solution ◽  
Alternative Designs ◽  
Interesting Alternative ◽  
Solution Classification

SUMMARYTensegrity mechanisms are composed of rigid and tensile parts that are in equilibrium. They are interesting alternative designs for some applications, such as modeling musculo-skeleton systems. Tensegrity mechanisms are more difficult to analyze than classical mechanisms as the static equilibrium conditions that must be satisfied generally result in complex equations. A class of planar one-degree-of-freedom tensegrity mechanisms with three linear springs is analyzed in detail for the sake of systematic solution classifications. The kinetostatic equations are derived and solved under several loading and geometric conditions. It is shown that these mechanisms exhibit up to six equilibrium configurations, of which one or two are stable, depending on the geometric and loading conditions. Discriminant varieties and cylindrical algebraic decomposition combined with Groebner base elimination are used to classify solutions as a function of the geometric, loading, and actuator input parameters.

scholarly journals Determination of the Strain-Free Configuration of Multispan Cable

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Chuancai Zhang ◽  
Qiang Guo ◽  
Xinhua Zhang
Keyword(s):  
Finite Element ◽  
Geometric Model ◽  
Static Equilibrium ◽  
Equilibrium Conditions ◽  
Constraint Equations ◽  
Asymptotic Shape ◽  
Geometric Conditions ◽  
End Conditions

For building a reasonable finite element geometric model, a method is proposed to determine the strain-free configuration of the multispan cable. The geometric conditions (the end conditions and the unstretched length conditions) as constraints for the configuration of multispan cable are given. Additionally, asymptotic static equilibrium conditions are given for determining the asymptotic shape of the multispan cable. By solving these constraint equations, a set of parameters are determined and then the strain-free configuration of multispan cable is determined. The method reported in this paper provides a technique for building reasonable FEA geometric model of multispan cables. Finally, a three-span cable is taken as example to illustrate the effectiveness of the method, and the computed results are validated via the software ADINA.

scholarly journals Two-vortex equilibrium in the flow past a flat plate at incidence

2014 ◽  
Vol 755 ◽  
pp. 50-61 ◽  
Author(s):  
Luca Zannetti ◽  
Alexandre Gourjii
Keyword(s):  
Flat Plate ◽  
Symmetric Equilibrium ◽  
Equilibrium Conditions ◽  
Kutta Condition ◽  
Vortex Pairs ◽  
Flow Past ◽  
Equilibrium Configurations ◽  
Asymmetric Flows ◽  
Asymmetric Equilibrium ◽  
Total Circulation

AbstractThe two-dimensional inviscid incompressible steady flow past an inclined flat plate is considered. A locus of asymmetric equilibrium configurations for vortex pairs is detected. It is shown that the flat geometry has peculiar properties compared to other geometries: (i) in order to satisfy the Kutta condition at both edges, which ensures flow regularity, the total circulation and the force acting on the plate must be zero; and (ii) the Kutta condition and the free vortex equilibrium conditions are not independent of each other. The non-existence of symmetric equilibrium configurations for an orthogonal plate is extended to more general asymmetric flows.

scholarly journals EQUILIBRIUM CONDITIONS IN BEACH WAVE INTERACTION

1972 ◽  
Vol 1 (13) ◽  
pp. 62 ◽  
Author(s):  
H. Raman
Keyword(s):  
Wave Interaction ◽  
Experimental Results ◽  
Laboratory Studies ◽  
Regular Waves ◽  
Equilibrium Conditions ◽  
Wave Characteristics ◽  
New Criterion ◽  
Constant Characteristics ◽  
Stable Points

Laboratory studies were conducted in an attempt to find out a relationship between beach and wave characteristics when equilibrium conditions are reached in beach wave interaction for the simple case of regular waves acting normal to the beach. Experimental results indicate the existence of stable points on beach profiles where the coordinates of the profile do not change with time when waves of constant characteristics act on the beach. Emperical relationship between the wave and beach properties are proposed. A new criterion for classification of beach profiles is indicated.

scholarly journals Static Equilibrium Configurations of Charged Metallic Bodies

2012 ◽  
Vol 27 (1) ◽  
Author(s):  
J Nzabanita ◽  
M Herberthson ◽  
BO Turesson ◽  
F Minani
Keyword(s):  
Static Equilibrium ◽  
Equilibrium Configurations

scholarly journals Cuspidal and noncuspidal robot manipulators

Robotica ◽  
2007 ◽  
Vol 25 (6) ◽  
pp. 677-689 ◽  
Author(s):  
Philippe Wenger
Keyword(s):  
Robot Manipulators ◽  
Sufficient Condition ◽  
Necessary And Sufficient Condition ◽  
Geometric Conditions ◽  
Necessary And Sufficient ◽  
Full Classification

SUMMARYThis article synthezises the most important results on the kinematics of cuspidal manipulators i.e. nonredundant manipulators that can change posture without meeting a singularity. The characteristic surfaces, the uniqueness domains and the regions of feasible paths in the workspace are defined. Then, several sufficient geometric conditions for a manipulator to be noncuspidal are enumerated and a general necessary and sufficient condition for a manipulator to be cuspidal is provided. An explicit DH-parameter-based condition for an orthogonal manipulator to be cuspidal is derived. The full classification of 3R orthogonal manipulators is provided and all types of cuspidal and noncuspidal orthogonal manipulators are enumerated. Finally, some facts about cuspidal and noncuspidal 6R manipulators are reported.

Threaded Components Under Axial Harmonic Vibration, Part 1: Experiments

1996 ◽  
Vol 118 (3) ◽  
pp. 417-422 ◽  
Author(s):  
D. P. Hess ◽  
K. Davis
Keyword(s):  
Kinematic Model ◽  
Harmonic Vibration ◽  
Static Equilibrium ◽  
Physical Parameters ◽  
Design Element ◽  
Equilibrium Conditions ◽  
Critical Design ◽  
Threaded Fasteners ◽  
Series Of Experiments ◽  
Theoretical Analyses

Threaded components have found ubiquitous use in many systems and structures. Although frequently overlooked, they represent a complex and often critical design element. One can identify numerous instances where such elements are subjected to vibratory conditions, yet their behavior in such an environment is still poorly understood. In this paper, we report on a series of experiments that were run to examine the motions of threaded fasteners subjected to axial harmonic vibration. The components are loaded by gravity and excited over a broad range of conditions. It is found that significant relative twisting motion can occur both with and against the load. This indicates that threaded components may loosen or tighten in the presence of vibration. It is shown that the direction of twist depends on the frequency and amplitude of the vibratory input as well as various physical parameters. Previous theoretical analyses of threaded components under vibration are based on static equilibrium conditions, and only predict a loosening action, i.e., twist with load. In Part 2 of this paper, a kinematic model is developed which predicts twisting both with and against load as observed in the experiments.

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