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.

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.

scholarly journals A new technique for the efficient use of Macro-Mistnets

Koedoe ◽  
1985 ◽  
Vol 28 (1) ◽  
Author(s):  
I.L. Rautenbach
Keyword(s):  
New Technique ◽  
Simple Method ◽  
A New Technique

A cheap and simple method of adapting yacht masts to allow quick and efficient stringing and versatile manipulation of a 6,0 x 30,0 metre macro-mistnet, is described.

scholarly journals Statistical properties of cloud lifecycles in cloud-resolving models

2009 ◽  
Vol 9 (6) ◽  
pp. 2195-2205 ◽  
Author(s):  
R. S. Plant
Keyword(s):  
Statistical Properties ◽  
New Technique ◽  
Average Lifetime ◽  
Cumulus Clouds ◽  
Simple Method ◽  
Model Simulations ◽  
Cloud Resolving Model ◽  
Time Histories ◽  
A New Technique

Abstract. A new technique is described for the analysis of cloud-resolving model simulations, which allows one to investigate the statistics of the lifecycles of cumulus clouds. Clouds are tracked from timestep to timestep within the model run. This allows for a very simple method of tracking, but one which is both comprehensive and robust. An approach for handling cloud splits and mergers is described which allows clouds with simple and complicated time histories to be compared within a single framework. This is found to be important for the analysis of an idealized simulation of radiative-convective equilibrium, in which the moist, buoyant updrafts (i.e., the convective cores) were tracked. Around half of all such cores were subject to splits and mergers during their lifecycles. For cores without any such events, the average lifetime is 30 min, but events can lengthen the typical lifetime considerably.

scholarly journals A new technique to prevent curling of guide wire in urinary bladder during J stent insertion with flexible cystoscope

2016 ◽  
Vol 10 (1-2) ◽  
pp. 34 ◽  
Author(s):  
Nasir Mahmood ◽  
Tahir Pasha
Keyword(s):  
Urinary Bladder ◽  
Local Anaesthetic ◽  
Ureteral Obstruction ◽  
Guide Wire ◽  
New Technique ◽  
Stent Insertion ◽  
Common Procedure ◽  
Simple Method ◽  
Flexible Cystoscope ◽  
A New Technique

Insertion of J stent is a very common procedure performed by urologists. This procedure is often performed to relieve ureteral obstruction due to stones, tumours, ureteral kink, or stricture on urgent basis. An increasing number of urologists are using a flexible cystoscope and local anaesthetic for J stent insertion. Occasionally, the guide wire curls in the bladder, making it impossible to insert the J stent. Here, we describe a simple method to overcome this problem using modified ureteral dilator, which is usually available in the cystoscopy suite.

Modeling Mechanical Stick-Slip Friction Using Electrical Circuit Analysis

1988 ◽  
Vol 110 (4) ◽  
pp. 440-443 ◽  
Author(s):  
Paul J. Kolston
Keyword(s):  
Mechanical System ◽  
Mechanical Systems ◽  
Electrical Circuit ◽  
Circuit Analysis ◽  
New Technique ◽  
Analysis Program ◽  
Stick Slip ◽  
A New Technique ◽  
Vast Range

A new technique for modeling stick-slip friction in mechanical systems is proposed. The technique uses an electrical circuit analysis program to analyze the electrical circuit equivalent of the mechanical system. The stick-slip characteristic can be altered to take almost any form. The method is easy to apply to a vast range of systems, and two examples are given to illustrate its validity.

scholarly journals Statistical properties of cloud lifecycles in cloud-resolving models

2008 ◽  
Vol 8 (6) ◽  
pp. 20537-20564 ◽  
Author(s):  
R. S. Plant
Keyword(s):  
Statistical Properties ◽  
New Technique ◽  
Average Lifetime ◽  
Cumulus Clouds ◽  
Simple Method ◽  
Model Simulations ◽  
Cloud Resolving Model ◽  
Time Histories ◽  
A New Technique

Abstract. A new technique is described for the analysis of cloud-resolving model simulations, which allows one to investigate the statistics of the lifecycles of cumulus clouds. Clouds are tracked from timestep-to-timestep within the model run. This allows for a very simple method of tracking, but one which is both comprehensive and robust. An approach for handling cloud splits and mergers is described which allows clouds with simple and complicated time histories to be compared within a single framework. This is found to be important for the analysis of an idealized simulation of radiative-convective equilibrium, in which the moist, buoyant, updrafts (i.e., the convective cores) were tracked. Around half of all such cores were subject to splits and mergers during their lifecycles. For cores without any such events, the average lifetime is 30 min, but events can lengthen the typical lifetime considerably.

scholarly journals Web security through improvised image based CAPTCHA

2017 ◽  
Vol 7 (1.1) ◽  
pp. 256
Author(s):  
R. Murugan ◽  
Tejasri. P ◽  
Nobesh Reddy ◽  
G. Dinesh
Keyword(s):  
Turing Test ◽  
Web Security ◽  
New Technique ◽  
User Needs ◽  
Simple Method ◽  
A New Technique

CAPTCHA is a Completely Automated Public Turing Test to tell Computers and Humans Apart [1]. Whenever a website is hosted onto a server it is not human that always tries to access the website. Sometimes a human generated computer bot also known as Zombie may try to access the website. In such situations bots need to be filtered from legitimate users and this can be accomplished by using a simple method called CAPTCHA. Initially CAPTCHA was developed on text-based platform later it was evolved to audio, image etc. In this paper a new technique to differentiate bots from humans is introduced. It is a question-based image-oriented technique where a question comprising of keywords is posed along with four different images out of which only one image has relation with all the keywords. The user needs to spot the image to pass the test. A flag will be counting the number of times the user failed the test and depending on the number of failure attempts the user is judged.

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.

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