Watt | EPFL Graph Search

The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named in honor of James Watt (1736–1819), an 18th-century Scottish inventor, mechanical engineer, and chemist who improved the Newcomen engine with his own steam engine in 1776. Watt's invention was fundamental for the Industrial Revolution. Overview When an object's velocity is held constant at one meter per second against a constant opposing force of one newton, the rate at which work is done is one watt. : \mathrm{1 ~ W = 1 ~ J {/} s = 1 ~ N {\cdot} m {/} s = 1 ~ kg {\cdot} m^2 {\cdot} s^{-3}} In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, how

Statically and dynamically balanced oscillator based on Watt's linkage

Simon Nessim Henein, Hubert Pierre-Marie Benoît Schneegans, Ilan Vardi

We present a new mechanical oscillator architecture that can be made insensitive to linear and angular accelerations while keeping constant oscillation frequency. The oscillator has the kinematics of a Watt linkage, so we call it a Watt oscillator. In order to predict its behaviour when it is subjected to external forces, we propose an analytical model using simplifying hypotheses. The solutions given by the analytical model were tested using an FEM model in order to obtain a dynamically balanced mechanism with frequency insensitive to external forces. A satisfactory correspondence between theory and FEM was found.

EUSPEN2020

Design and Control of an Innovative Micro-Rover

Michel Lauria, Roland Siegwart

During recent years the European Space Agency (ESA) has started to develop concepts for micro-rovers for planetary missions. An ESA Technology Research Program (TRP) activity "Micro-Robots for Scientific Applications" has been dedicated to this subject. Within an interdisciplinary group of space companies and research labs new designs of micro-rovers have been investigated. Two concepts, a simple and robust one and an innovative one, have been selected and functional breadboard models of them are currently built. After a discussion of the key issues for robust locomotion the present paper will focus on the design, implementation and control of SpaceCat, the more innovative solution selected as breadboard model B whereas the complementary work on breadboard model A is described in detail in [1]. It consists of 6 independently driven wheels arranged in two triangles. It therefore allows not only for efficient rolling on flat surfaces but also to step on obstacles. Additionally the center of mass and the instrumentation carrousel is adjustable, allowing to optimally balance the micro-rover in almost every situation. Even after flipping over the robot will always be able to get back on its wheels. To navigate the rover autonomously within a range of about 10 to 20 meters from the lander, an active vision system is used with a camera on the lander. It allows to control the robot through a very user-friendly interface. Local piloting and obstacle avoidance is based on various on board sensors. This enables robust and collision free operation even in rough terrain. ESA defined the following main requirements and constraints: o Stowed dimensions envelope (cm): 30 x 20 x 20 o Net mass of the robot system:max. 2 kg o Mass of the scientific payload:2 kg o Electrical power provided by lander:max. 2 Watt average, max. 3 Watt peak o Possibility to position the on board sensors: accuracy around 1 mm o Maximum speed: 5 m/h The rover must overcome obstacles of 0.1 m height and holes of 0.1 m width. It has to be able to climb slopes of 15° upwards and 20° downwards. Simple maneuvers like turning and moving backward is required too. Moreover, to ensure mission success the following requirements have been identified: o No risk of sinkage and getting stuck in the sand o Flip-over stability o Recovery after flip-over and after having been buried by a sand storm

1998

La société à 2000 watt: analyse critique

Daniel Favrat, Pierre-André Haldi

La consommation d’énergie primaire par personne, toutes énergies confondues, atteint actuellement 6’000 watt∙an/an (c’est-à-dire 190 milliards de joule/an) en Europe de l’Ouest; elle monte jusqu’à 12'000 watt∙an/an aux Etats- Unis, mais ne dépasse guère 500 watt∙an/an en moyenne en Afrique. En Suisse, elle est d’environ 5’000 watt∙an/an, soit 2,5 fois plus que la moyenne mondiale qui s’établit à 2'000 watt∙an/an (2000 watt en notation abrégée ). Mis à part que le maintien de telles inégalités ne sauraient se justifier à long terme, le fait que cette consommation d’énergie repose à 80% sur des agents énergétiques non- renouvelables (charbon, pétrole, gaz naturel, uranium) pose de sérieux problèmes en matière d’épuisement de ces ressources et d’atteintes, potentiellement irréversibles, à l’environnement. A l’évidence, une diminution drastique de la consommation de ces énergies s’impose, au moins dans les pays de nos jours les plus « énergivores ». C’est ce constat qui a incité le Conseil des Ecoles Polytechniques Fédérales à lancer en 1998, pour la Suisse, son initiative de « Société à 2000 watt ». Il s’agit d’un ambitieux programme d’encouragement à la recherche visant à trouver des solutions permettant de réduire d’un facteur 2.5 environ la consommation individuelle d’énergie en Suisse à l’horizon 2050, tout en maintenant le standard de niveau de vie actuel de la population helvétique. Cet objectif devrait être atteint par l’utilisation des technologies et procédés les plus économes en énergie, associée à un comportement général plus responsable en matière de consommation d’énergie. En d’autres termes, il s’agit de promouvoir une utilisation plus efficace et rationnelle des ressources énergétiques primaires, en favorisant par ailleurs celles dont la transformation en énergie utile conduit aux atteintes à l’environnement les plus faibles. Si des progrès substantiels sont difficiles à attendre dans certains secteurs (transport aérien par exemple), ils pourraient être beaucoup plus marqués dans d’autres (transport individuel, bâtiment, biens de grande consommation, procédés industriels, par exemple). Des études préliminaires ont montré que l’objectif d’une réduction des deux tiers de la consommation annuelle d’énergie par habitant en Suisse dans un délai d’une cinquantaine d’année ne paraît pas totalement utopique, même s’il ne sera, évidemment, pas facile à atteindre.