Differential (mechanical device)

A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analog computers. Differentials can also provide a gear ratio between the input and output shafts (called the "axle ratio" or "diff ratio"). For example, many differentials in motor vehicles provide a gearing reduction by having fewer teeth on the pinion than the ring gear. History Milestones in the design or use of differentials include:

100 BCE–70 BCE: The Antikythera mechanism has been dated to this period. It was discovered in 1902 on a shipwreck by sponge divers, and modern research suggests that it used a differential gear to determine the angle between the ecliptic positions of the Sun and Moon, and thus the phase of the Moon.
c. 2

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related publications (5)

Related publications

Related people

Related units

Related concepts (25)

Related concepts

Related courses (17)

Related courses

Related lectures (22)

Related lectures

Tibial component positioning in total knee arthroplasty: bone coverage and extensor apparatus alignment

Pierre Lemaire, Pierre-François Leyvraz, Reto Meuli, Dominique Pioletti

Correct positioning of the tibial component in total knee arthroplasty (TKA) must take into account both an optimal bone coverage (defined by a maximal cortical bearing with posteromedial and anterolateral support) and satisfactory patellofemoral tracking. Consequently, a compromise position must be found by the surgeon during the operation to simultaneously meet these two requirements. Moreover, tibial tray positioning depends upon the tibial torsion, which has been shown to act mainly in the proximal quarter of the tibia. Therefore, the correct application of the tibial tray is also theoretically related to the level of bone resection. In this study, we first quantified the torsional profile given by an optimal bone coverage for a symmetrical tibial tray design and for an asymmetrical one. Then, for the two types of tibial trays, we measured the angle difference between optimal bone coverage and an alignment on the middle of the tibial tubercule. Results showed that the values of the torsional profile given by the symmetrical tray were more scattered than those from the asymmetrical one. However, determination of the mean differential angle between the position providing optimal bone coverage and the one providing the best patellofemoral tracking indicated that the symmetrical prosthetic tray offered the best compromise between these two requirements. Although the tibiofemoral joint is known to be asymmetric in both shape and dimension, the asymmetrical tray chosen in this study was found to fulfill this compromise with more difficulty.

1997

Crash test-based assessment of injury risks for adults and children when colliding with personal mobility devices and service robots

Aude Billard, Diego Felipe Paez Granados

Autonomous mobility devices such as transport, cleaning, and delivery robots, hold a massive economic and social benefit. However, their deployment should not endanger bystanders, particularly vulnerable populations such as children and older adults who are inherently smaller and fragile. This study compared the risks faced by different pedestrian categories and determined risks through crash testing involving a service robot hitting an adult and a child dummy. Results of collisions at 3.1 m/s (11.1 km/h/6.9 mph) showed risks of serious head (14%), neck (20%), and chest (50%) injuries in children, and tibia fracture (33%) in adults. Furthermore, secondary impact analysis resulted in both populations at risk of severe head injuries, namely, from falling to the ground. Our data and simulations show mitigation strategies for reducing impact injury risks below 5% by either lowering the differential speed at impact below 1.5 m/s (5.4 km/h/3.3 mph) or through the usage of absorbent materials. The results presented herein may influence the design of controllers, sensing awareness, and assessment methods for robots and small vehicles standardization, as well as, policymaking and regulations for the speed, design, and usage of these devices in populated areas.

2022

Screen-printed polymer-based microfluidic and micromechanical devices based on evaporable compounds

Yannick Fournier, Caroline Jacq, Thomas Maeder, Peter Ryser, Nathalie Sophie Adeline Serra

We investigate in this work the fabrication of polymer fluidic and mechanical devices based on evaporable compounds as sacrificial layers using the screen-printing process. The combination of thermosetting polymer resins with evaporable compounds as sacrificial layers allows straightforward fabrication of polymer microfluidic and micromechanical devices. Channel, cavities and spacings are first defined by sacrificial material layers. This is followed by polymer resin deposition and polymerization / solvent removal. Removal of the sacrificial layers is then accomplished by heating at their decomposition / evaporation temperature. This process does not require an ulterior dissolution step, and systems exist where the sacrificial layer molecules escape by diffusion through the polymer at high temperature: we are therefore not limited to open structures. Furthermore, the use of screen- printed thick-film compositions is very advantageous regarding process cost and flexibility. The selected sacrificial layer must be stable at the polymer processing temperature, yet decompose / evaporate cleanly at a temperature low enough to avoid degradation of the polymer. In this work, we used polymers such as ethylcellulose and silicone resins filled with graphite to impart electrical conductivity and improve mechanical stability. The selected sacrificial materials were polyol-based and were formulated to sublime rather than evaporate, in order to preserve the structures. They were formulated as thick-film pastes using a suitable cyclohexanol-based solvent mix.

IMAPS2009

MICRO-200: Mechanism Design I

Ce cours introduit les bases de la mécanique des structures : calcul des contraintes et déformations provoquées par les forces extérieures et calcul des déformations. Ces enseignements théoriques sont appliqués à la conception des éléments importants des mécanismes de précision.

ME-426: Micro/Nanomechanical devices

In this course we will see an overview of the exciting field of Micro and Nanomechanical systems. We will go over the dfferent scaling laws that dominate the critical parameters, how size affects material properties, how these devices are manufactured, designed and later used.

ME-251: Thermodynamics and energetics I

Introduction aux principes de la thermodynamique, propriétés thermodynamiques de la matière et à leur calcul. Les étudiants maîtriseront les concepts de conservation (chaleur, masse, quantité de mouvement) et appliqueront ces concepts au cycles thermodynamiques et systèmes de conversion d'énergie.

Gear

A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called cogs), which mesh with another (compatible) toothed part to transmit

Car

A car, or an automobile is a motor vehicle with wheels. Most definitions of cars say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people, no

Wheel

A wheel is a circular component that is intended to rotate on an axle bearing. The wheel is one of the key components of the wheel and axle which is one of the six simple machines. Wheels, in conjunc