947 research outputs found
Reply to the Ch. Lagrange’s note
No full textThe author answers to a Ch. Lagrange’s note who refutes his theory on the diurnal nutation.L’auteur répond à une note de Ch. Lagrange qui réfute sa théorie sur la nutation diurne
Artificial-Delay Adaptive Control for Under-actuated Euler-Lagrange Robotics
No full textArtificial-delay control is a method in which state and input measurements collected at an immediate past time instant (i.e. artificially delayed) are used to compensate the uncertain dynamics affecting the system at the current time. This work formulates an artificial-delay control method with adaptive gains in the presence of nonlinear (Euler-Lagrange) under-actuation. The appeal of studying Euler-Lagrange dynamics is to capture many robotics applications of practical interest, as demonstrated via stability and robustness analysis and via robotic ship and robotic aerial vehicle test cases.Accepted Author ManuscriptTeam Bart De Schutte
Adaptive single-stage control for uncertain nonholonomic Euler-Lagrange systems
No full textThis work introduces a new single-stage adaptive controller for Euler-Lagrange systems with nonholonomic constraints. The proposed mechanism provides a simpler design philosophy compared to double-stage mechanisms (that address kinematics and dynamics in two steps), while achieving analogous stability properties, i.e. stability of both original and internal states. Meanwhile, we do not require direct access to the internal states as required in state-of-the-art single-stage mechanisms. The proposed approach is studied via Lyapunov analysis, validated numerically on wheeled mobile robot dynamics and compared to a standard double-stage approach.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Bart De Schutte
Dynamic constitutive equation of GFRP obtained by Lagrange experiment
No full textThe note presents a method of constructing dynamic constitutive equations of material by means of Lagrange experiment and analysis. Tests were carried out by a light gas gun and the stress history profiles were recorded on multiple Lagrange positions. The dynamic constitutive equations were deduced from the regression of a series of data which was obtained by Lagrange analysis based upon recorded multiple stress histories. Here constitutive equations of glass fibre reinforced phenolic resin composite(GFRP) in uniaxil strain state under dynamic loading are given. The proposed equations of the material agree well with experimental results
A comparative analysis of Lagrange multiplier and penalty approaches for modelling fluid-structure interaction
No full textPurpose: When simulating fluid-structure interaction (FSI), it is often essential that the no-slip condition is accurately enforced at the wetted boundary of the structure. This paper aims to evaluate the relative strengths and limitations of the penalty and Lagrange multiplier methods, within the context of modelling FSI, through a comparative analysis. Design/methodology/approach: In the immersed boundary method, the no-slip condition is typically imposed by augmenting the governing equations of the fluid with an artificial body force. The relative accuracy and computational time of the penalty and Lagrange multiplier formulations of this body force are evaluated by using each to solve three test problems, namely, flow through a channel, the harmonic motion of a cylinder through a stationary fluid and the vortex-induced vibration (VIV) of a cylinder. Findings: The Lagrange multiplier formulation provided an accurate solution, especially when enforcing the no-slip condition, and was robust as it did not require “tuning” of problem specific parameters. However, these benefits came at a higher computational cost relative to the penalty formulation. The penalty formulation achieved similar levels of accuracy to the Lagrange multiplier formulation, but only if the appropriate penalty factor was selected, which was difficult to determine a priori. Originality/value: Both the Lagrange multiplier and penalty formulations of the immersed boundary method are prominent in the literature. A systematic quantitative comparison of these two methods is presented within the same computational environment. A novel application of the Lagrange multiplier method to the modelling of VIV is also provided.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Wind EnergyAerospace Structures & Computational Mechanic
A Spatial Bayesian Hedonic Pricing Model of Farmland Values
No full textIn 1973, British Columbia created the Agricultural Land Reserve (ALR) to protect farmland from development. This study investigates whether the ALR has been effective near the city of Victoria. Therefore, we employ a GIS-based hedonic pricing model and quantify ALR specific measures. Bayesian Model Averaging in combination with Markov Chain Monte Carlo Model Composition are used to address specification uncertainty. Results show that zoning schemes are partly credible. Zoned farmland sells for lower prices than other farmland. However, farmland located closer to the city of Victoria is priced higher and hobby farmers pay higher prices than conventional farmers.Farmland prices, Bayesian Model Averaging, Hedonic pricing., Land Economics/Use,
Leaderless Consensus of Heterogeneous Multiple Euler-Lagrange Systems With Unknown Disturbance
No full textThis article studies the leaderless consensus problem of heterogeneous multiple networked Euler-Lagrange systems subject to persistent disturbances with unknown constant biases, amplitudes, initial phases, and frequencies. The main characteristic of this study is that none of the agents has information of a common reference model or of a common reference trajectory. Therefore, the agents must simultaneously and in a distributed way: achieve consensus to a common reference model (group model); achieve consensus to a common reference trajectory; and reject the unknown disturbances. We show that this is possible via a suitable combination of techniques of distributed 'observers,' internal model principle and adaptive regulation. The proposed design generalizes recent results on group model learning, which have been studied for linear agents over undirected networks. In this article, group model learning is achieved for Euler-Lagrange dynamics over directed networks in the presence of persistent unknown disturbances. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Bart De Schutte
Le Père Lagrange et Agnes Smith Lewis
No full textLa rencontre entre ces deux grandes figures des études bibliques au tournant du XIXe et du XXe siècle que furent Agnes Smith Lewis (1843-1926) et le Père Marie-Joseph Lagrange (1855-1938), qui eut lieu en 1893 au monastère de Ste Catherine du Sinaï, est connue. Elle est mentionnée, par ex., au ch. 18 de la récente monographie que J. Soskice a consacrée aux sœurs Smith (voir mon billet sur les reproductions du Syrus Sinaiticus). Je ne suis pas sûr, en revanche, que le témoignage du P. Lagrange..
Mécanique Analytique
No full textJoseph-Louis Lagrange (1736–1813), one of the notable French mathematicians of the Revolutionary period, is remembered for his work in the fields of analysis, number theory and mechanics. Like Laplace and Legendre, Lagrange was assisted by d'Alembert, and it was on the recommendation of the latter and the urging of Frederick the Great himself that Lagrange succeeded Euler as the director of mathematics at the Prussian Academy of Sciences in Berlin. The two-volume Mécanique analytique was first published in 1788; the edition presented here is that of 1811–15, revised by the author before his death. In this work, claimed to be the most important on classical mechanics since Newton, Lagrange developed the law of virtual work, from which single principle the whole of solid and fluid mechanics can be derived.</jats:p
Optimal Translunar Lagrange Point Orbits for OLFAR
No full textInvestigation of the feasibility of using translunar Lagrange point orbits for low-frequency radio wave astronomy, in particular for Orbiting Low-Frequency Antennas fro Radio astronomy (OLFAR). Furthermore suggesting swarm and orbit configurations that lead to the best possible results.Astrodynamics & Space Missions (AS)Aerospace Engineerin
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