Improving Techniques in Statically Equivalent Serial Chain Modeling for Center of Mass Estimation

2014 ◽  
Author(s):  
Bingjue Li ◽  
Andrew P. Murray ◽  
David H. Myszka
Keyword(s):  
Center Of Mass ◽  
Original System ◽  
Rigid Bodies ◽  
Joint Angles ◽  
Practical Applications ◽  
Serial Chain ◽  
System Of Rigid Bodies ◽  
Final Development ◽  
Data Error ◽  
Insight Into

Any articulated system of rigid bodies defines a Statically Equivalent Serial Chain (SESC). The SESC is a virtual chain that terminates at the center of mass (CoM) of the original system of bodies. A SESC may be generated experimentally without knowing the mass, CoM, or length of each link in the system given that its joint angles and overall CoM may be measured. This paper presents three developments toward recognizing the SESC as a practical modeling technique. Two of the three developments improve utilizing the technique in practical applications where the arrangement of the joints impacts the derivation of the SESC. The final development provides insight into the number of poses needed to create a usable SESC in the presence of data collection errors. First, modifications to a matrix necessary in computing the SESC are proposed. Second, the problem of generating a SESC experimentally when the system of bodies includes a mass fixed in the ground frame are presented and a remedy is proposed for humanoid-like systems. Third, an investigation of the error of the experimental SESC versus the number of data readings collected in the presence of errors in joint readings and CoM data is conducted. By conducting the method on three different systems with various levels of data error, a general form of the function for estimating the error of the experimental SESC is proposed.

Improving Techniques in Statically Equivalent Serial Chain Modeling for Center of Mass Estimation

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Bingjue Li ◽  
Andrew P. Murray ◽  
David H. Myszka
Keyword(s):  
Center Of Mass ◽  
Original System ◽  
Rigid Bodies ◽  
Joint Angles ◽  
Practical Applications ◽  
Serial Chain ◽  
System Of Rigid Bodies ◽  
Final Development ◽  
Data Error ◽  
Insight Into

Any articulated system of rigid bodies defines a statically equivalent serial chain (SESC). The SESC is a virtual chain that terminates at the center of mass (CoM) of the original system of bodies. An SESC may be generated experimentally without knowing the mass, CoM, or length of each link in the system given that its joint angles and overall CoM may be measured. This paper presents three developments toward recognizing the SESC as a practical modeling technique. Two of the three developments improve utilizing the technique in practical applications where the arrangement of the joints impacts the derivation of the SESC. The final development provides insight into the number of poses needed to create a usable SESC in the presence of data collection errors. First, modifications to a matrix necessary in computing the SESC are proposed, followed by the experimental validation of SESC modeling. Second, the problem of generating an SESC experimentally when the system of bodies includes a mass fixed in the ground frame are presented and a remedy is proposed for humanoid-like systems. Third, an investigation of the error of the experimental SESC versus the number of data readings collected in the presence of errors in joint readings and CoM data is conducted. By conducting the method on three different systems with various levels of data error, a general form of the function for estimating the error of the experimental SESC is proposed.

Material and Local Time Derivatives of Screws With Applications to Dynamics and Stiffness

2004 ◽  
Author(s):  
Harvey Lipkin
Keyword(s):  
Elastic System ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Rigid Bodies ◽  
Material Derivative ◽  
Gravitational Loading ◽  
Moving Body ◽  
Rigid Body Mechanics ◽  
Derivatives Of ◽  
Insight Into

Screw quantities provide geometric insight into three-dimensional mechanics modeled by rigid bodies and lumped parameters. Four distinct cases of time differentiation are examined by combining fixed and moving body derivatives (fundamental to rigid body mechanics) with material and local derivatives (fundamental to continuum mechanics). Three combinations always yield another screw quantity while the most common, the material derivative with respect to the fixed body, does not. Two fundamental formulations are examined with this last derivative, Euler’s Laws and the gravitational loading of an elastic system. By coincidence, the formulations appear screw-like when they are expressed at the center-of-mass but, in contrast to actual screw formulations, they do not retain invariant forms when expressed at arbitrary points.

Estimation of the Center of Mass Using Statically Equivalent Serial Chain Modeling

2009 ◽  
Author(s):  
Sebastien Cotton ◽  
Andrew Murray ◽  
Philippe Fraisse
Keyword(s):  
Humanoid Robot ◽  
Center Of Mass ◽  
Mechanical Systems ◽  
Rigid Bodies ◽  
New Technique ◽  
Simple Method ◽  
Sensitivity Calculation ◽  
Serial Chain ◽  
A New Technique ◽  
Branched Chain

This paper proposes a new technique to estimate the center of mass (CoM) of mechanical systems defined by an articulated set of rigid bodies. This technique is based on the use of the statically equivalent serial chain, a serial chain representation on any multi-link branched chain. Through the use of this model, and without any knowledge of each individual body’s CoM or CoM location, a simple method to estimate the mechanical system’s CoM is developed. This method is validated with the CoM estimation of the Hoap-3 humanoid robot. A sensitivity calculation for estimating the CoM in this way is also presented.

Numerical Study of Viscous Flows Inside Partially Filled Spinning and Coning Cylinders

1996 ◽  
Vol 118 (2) ◽  
pp. 335-340 ◽  
Author(s):  
Mohamed Selmi
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Center Of Mass ◽  
Steady Motion ◽  
Practical Interest ◽  
Nonlinear Effects ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Practical Applications ◽  
Analysis And Design

This paper is concerned with the solution of the 3-D-Navier-Stokes equations describing the steady motion of a viscous fluid inside a partially filled spinning and coning cylinder. The cylinder contains either a single fluid of volume less than that of the cylinder or a central rod and a single fluid of combined volume (volume of the rod plus volume of the fluid) equal to that of the cylinder. The cylinder rotates about its axis at the spin rate ω and rotates about an axis that passes through its center of mass at the coning rate Ω. In practical applications, as in the analysis and design of liquid-filled projectiles, the parameter ε = τ sin θ, where τ = Ω/ω and θ is the angle between spin axis and coning axis, is small. As a result, linearization of the Navier-Stokes equations with this parameter is possible. Here, the full and linearized Navier-Stokes equations are solved by a spectral collocation method to investigate the nonlinear effects on the moments caused by the motion of the fluid inside the cylinder. In this regard, it has been found that nonlinear effects are negligible for τ ≈ 0.1, which is of practical interest to the design of liquid-filled projectiles, and the solution of the linearized Navier-Stokes equations is adequate for such a case. However, as τ increases, nonlinear effects increase, and become significant as ε surpasses about 0.1. In such a case, the nonlinear problem must be solved. Complete details on how to solve such a problem is presented.

Market Opportunity Analysis in Thailand: Case of Individual Power Sources by Thermoelectric-Generator Technology for Portable Electronics

2019 ◽  
Vol 16 (03) ◽  
pp. 1950027
Author(s):  
Surapree Maolikul ◽  
Thira Chavarnakul ◽  
Somchai Kiatgamolchai
Keyword(s):  
Thermoelectric Generator ◽  
Electrical Power ◽  
Technology Commercialization ◽  
Market Opportunity ◽  
Business Research ◽  
Power Sources ◽  
Practical Applications ◽  
Portable Electronics ◽  
Decision Factors ◽  
Insight Into

Thermoelectrics, an energy-conversion technology, has been developed for its potential to support portable electronics with an innovative power source. Primarily focusing on the metropolitan market in Thailand, the study, thus, aimed at the market insight into portable electronics users’ characteristics and opinions of thermoelectric-generator (TEG) technology commercialization. The business research was conducted to analyze their behaviors for power-supply lacking problems, encountering heat or cold sources, purchasing decision for a TEG-based charger and key decision factors. For practical applications, an innovative TEG-based charger should be more flexible by harnessing various heat or cold sources from ambient situations to generate electrical power.

The Temporal and the Eternal

2005 ◽  
pp. 611-636
Keyword(s):  
Rational Decision ◽  
Practical Applications ◽  
The World ◽  
The Universe ◽  
Insight Into

This chapter, taken from Josiah Royce's Gifford Lectures of 1899, argues that any rational decision as between a pessimistic and an optimistic view of the world, any account of the relations between God and Man, any view of the sense in which the evils and imperfections of the Universe can be comprehended or justified, any account of our ethical consciousness in terms reconcilable with our Idealism must turn in part upon a distinction between the Temporal and the Eternal, and upon an insight into their unity in the midst of their contrast. The problem at issue is one of the most delicate and, at the same time, one of the simplest of the great issues of philosophy. The chapter deals with it at first in a purely theoretical fashion and then proceeds to its practical applications.

Literature Review of Clergy Resilience and Recommendations for Future Research

2020 ◽  
pp. 009164712096813
Author(s):  
Andrea M. Sielaff ◽  
Kate Rae Davis ◽  
J. Derek McNeil
Keyword(s):  
Literature Review ◽  
Traumatic Stress ◽  
Well Being ◽  
Work Life ◽  
Future Research ◽  
Review Of The Literature ◽  
Practical Applications ◽  
Insight Into ◽  
Professional Ministry

Clergy often experience a call to help others; however, this passion is hard to sustain because of the chronic and traumatic stress that are components of the job. Because of the unique stressors that are part of professional ministry, clergy need targeted support that is systemic as well as individual to practice resilience. This review of the research provides insight into what factors most impact clergy well-being; as congregations, supervisors, and denominations learn more about these factors, they can more effectively create environments in which clergy can be resilient. This review of the literature also illuminates what clergy might do for themselves to create a sustainable work life that supports their growth and thriving in the midst of adversity in ministry. In addition to articulating the specific stressors clergy face, this review resources congregations, clergy, and supervisors with practical applications of resilience research.

scholarly journals Stability of time-delay systems via Lyapunov functions

2002 ◽  
Vol 8 (3) ◽  
pp. 197-205 ◽  
Author(s):  
Carlos F. Alastruey ◽  
Manuel de la Sen
Keyword(s):  
Lyapunov Function ◽  
Lyapunov Functions ◽  
A Priori ◽  
Original System ◽  
Delay Systems ◽  
Multivariable Systems ◽  
Time Delay Systems ◽  
Input Output ◽  
Practical Applications ◽  
System A

In this paper, a Lyapunov function candidate is introduced for multivariable systems with inner delays, without assuminga prioristability for the nondelayed subsystem. By using this Lyapunov function, a controller is deduced. Such a controller utilizes an input–output description of the original system, a circumstance that facilitates practical applications of the proposed approach.

Experimental and empirical study of large transverse deformation of triangular plates subjected to water hammer shock loading

2019 ◽  
Vol 233 (12) ◽  
pp. 2498-2509
Author(s):  
Mojtaba Haghgoo ◽  
Mohammad Rezasefat ◽  
Ali Mahmoudi ◽  
Hashem Babaei
Keyword(s):  
Mechanical Properties ◽  
Center Of Mass ◽  
Experimental Tests ◽  
Experimental Results ◽  
Dimensionless Numbers ◽  
Hydrodynamic Loads ◽  
Drop Hammer ◽  
Properties Of Materials ◽  
Plate Geometry ◽  
Insight Into

In this paper, the dynamic plastic response of isosceles triangular plates under hydrodynamic loads was investigated experimentally using a drop hammer machine. To do this, a series of experimental tests were carried out on mild steel triangular plates with different thicknesses to bring insight into the effect of geometry and mechanical properties of the plate on the deformation of specimens, which were impacted by a piston-induced pressure wave inside a water tube. The effects of various impact loads originated from different drop hammer standoff distances, and hammer weights concerning variations of deflection of the center of mass were described. The experimental results were presented in terms of deflection of the center of mass of the plates and deflection profiles. The experimental results showed that the plate with lower thickness experienced higher deflection-to-thickness ratio. An empirical model was also proposed based on new dimensionless numbers for triangular plates in order to predict the ratio of deflection of the center of mass to thickness. The dimensionless numbers considered the effects of plate geometry, hydrodynamic applied load, and mechanical properties of materials. Comparison between the experimental results and empirical predictions demonstrated that the suggested model is accurate enough to predict of the response of isosceles triangular plates under hydrodynamic loads.

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