Wheelies: Computers help electric cars turn

Researchers have modified this off-road vehicle and turned it into an electric car. Because the car now has a motor in each wheel (but no engine, transmission or differential), the researchers are designing and testing a computer program that controls each wheel’s speed independently. (The yellow “training wheel” extending from the side of the vehicle keeps the car from turning over in case the program doesn’t work correctly.)

A typical car produces power when its engine burns gasoline (or diesel) to move a piston up and down in a cylinder. The transmission transfers that mechanical energy to the wheels. It does so through a variety of rods, gears and other equipment. Sometimes that power only goes to two wheels (as in front- or rear-wheel-drive cars). Four-wheel-drive vehicles provide torque to each wheel. (Torque is a twisting force — unlike the push or pull that tends to shove or tug an object in one direction.)

To make today’s vehicles run smoothly as they turn corners, automakers include a set of gears known as a differential. It allows some wheels to rotate at different speeds. To be precise, it lets wheels on the outside of a turn rotate faster than those on the inside of a turn. They have to, explains Junmin Wang, because wheels on the outside of the turn have to travel farther, in a given span of time, than do the inside wheels. (A mechanical engineer at Ohio State University, Wang studies how to make electric cars safe and reliable.)

Without a differential, wheels on one side or the other would slip or skid during every turn. That would decrease the vehicle’s overall traction. It also would make car tires wear out faster than normal.

The challenge, Wang says, has been coordinating wheel speeds in all-electric vehicles without using a differential. Not only do electric vehicles send power to the wheels through wires, but many also give each wheel its own motor. (This tends to make the car lighter.) But, a computer must control each in-wheel motor’s speed.

Determining how fast each wheel should rotate remains a big challenge. That’s what Wang and his team worried over while designing their all-electric car. Their prototype, or early version, began its life as an off-road vehicle (like many armers and hunters use).

The engineers removed their car’s engine, transmission and differential. Then they installed a motor in each wheel and a computer. With its extra-heavy-duty batteries, the final car tips the scales at about 800 kilograms (a little more than 1,750 pounds). That’s about the same as the original vehicle. If they had this altered a full-size car this way, the weight savings would have been even greater.

In earlier studies, Wang notes, some researchers tried to gauge a wheel’s speed with cameras or with microphones (listening for a skid, for example). His team approached things in a new way. They estimate the forces on a car’s wheels when it rounds a corner.

The computer that controls the wheels receives its commands from the steering wheel, gas pedal and brakes. The car updates those commands about 100 times each second. The computer also gets information from an accelerometer (a sensor that measures changes in the rate of movement) and other sensors. For example, one of those other sensors lets the computer know if the car is skidding sideways.

Finally, data from a Global Positioning System (GPS) device provides data on the car’s speed. (Normally, a car’s speed is measured by a device that measures how fast the car’s transmission is turning. But remember, Wang’s car lacks that transmission.)

With each new batch of data, the computer calculates how fast each wheel should be rotating to make the car’s ride safe and smooth. Then it directs the batteries to deliver the proper amount of power to each wheel. Afterward, the computer checks how each wheel responds. If each wheel isn’t turning at the proper speed, the computer will adjust it. Wang’s group shares details on this computer control of their car’s wheels in the January 2013 issue of Control Engineering Practice.

“The computer and sensors make a virtual differential,” explains Wang. If a vehicle doesn’t have a real, gear-based differential, he notes, some sort of computerized control is vital. After all, if a car’s wheels don’t rotate at the proper speeds, they could send the vehicle in the wrong direction or into a skid, flip or crash.

The team’s results “are very interesting,” says Pierre Sicard. He’s an electrical engineer at the University of Quebec in Three Rivers, Canada. Monitoring wheel speed is useful for preventing the car from skidding or locking up its brakes, he notes.

But monitoring wheel speed can help in other ways too, he adds. For instance, electric vehicles can recover energy when they’re braking. (In most cars today, braking converts kinetic energy into heat, which is lost. But with the right equipment, the kinetic energy of a car’s motion can be converted to electrical energy. This can be returned to the batteries and stored for later use, Sicard points out.) Boosting energy efficiency is one of the big challenges automotive engineers will face with all cars in the future.

More and more electric vehicles soon will be hitting the roads. Research by Junmin Wang’s team and others will undoubtedly help make those cars lighter, safer and more energy-efficient.

Power Words

accelerometer  An instrument for measuring vibrations or a change in the rate of movement. These sensors typically can measure movement changes in all three dimensions (front-to-back, side-to-side, and up-and-down).

differential  The set of gears that enables wheels on the outside of a vehicle’s turn to travel faster than those on the inside of the turn. This difference in rotational speed is required because the outer wheels have to travel a greater distance when a vehicle turns.

electrical engineer  An engineer who designs, builds, or analyzes electrical equipment.

engine  A machine designed to convert energy into useful mechanical motion. Sometimes an engine is called a “motor.”

engineer  A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

GPS  Abbreviation for Global Positioning System.

GPS device  This system uses devices that calculate their position (in terms of latitude, longitude and elevation — or altitude) at any place on Earth, whether on the ground or in the air. They do this by comparing how long it takes signals from different satellites to reach them.

kinetic energy  The energy held by an object due to its being in motion. The amount of this energy contained will depend on both the mass (usually weight) of the object and its speed.

mechanical engineer An engineer who designs, builds or operates machines.

motor  A device that converts electricity into mechanical motion.

prototype  A first or early model of some device that still needs to be perfected.

transmission  In a liquid-fueled vehicle, the machinery used to transfer power from the engine to the drive wheels.

Sumber : http://discovermagazine.com/

Amazing 3-D Display Lets Video Chatters Interact With Remote Objects [Video]

inFORM may be the future of remote ball-rolling. Image credit: MIT Tangible Media Group

The future of the Web, it seems, is not just sending data but transmittingactions. Telepresence robots and remote-control drones already let an internet user in one place control far-off gadgets in the physical world. Now another such device has emerged on the scene—a dynamic display that transmits 3-D shapes from the sender to the receiver.

The device is called inFORM, a “dynamic shape display” developed by researchers at MIT. Think of it as a long, wireless line of communication. On the receiving end of this line is a surface comprised of 30 by 30 pins. Each pin has a tiny motor attached to its base, which can move it up and down independently of the 899 others.

On the other end of the line, a depth-sensing camera records physical objects or movements and sends that information to the motorized surface. Each of the pins acts as a three-dimensional pixel to recreate that information in a physical form. It essentially makes the 3-D vision pop up from the surface.

This may all sound kind of confusing and obscure, but think of it this way: it’s like a cross between Skype one of those bizarre, ’90s pin-art toys.

Hi Mom! Look at my face! Image credits: bloomua/Shutterstock and Heather Katsoulis/Flickr

The list of potential applications inFORM’s developers foresee is nifty and far-reaching: from 3-D visualizations of CT scans, via interactive terrain models for urban planners, to long-distance design sessions between collaborating architects. But to make these applications practical, the resolution will need to be ramped up significantly. Future iterations of inFORM will have to include far more pins and far greater control.

Sumber : http://discovermagazine.com/

What Brain Activity Can Explain Suspension of Disbelief?

Although we know a fair amount about the brain activity linked with reading, no one has isolated the mechanisms tied specifically to suspension of disbelief. Yet we can extrapolate how the brain behaves on a more general level.

Poet Samuel Taylor Coleridge coined the term “suspension of disbelief” in 1817, but almost two centuries would lapse before we could infer how the brain might support this puzzling phenomenon. Coleridge asked readers of his fantastical poems, includingThe Rime of the Ancient Mariner, to give him “that willing suspension of disbelief for the moment, which constitutes poetic faith.” That phrase, “poetic faith,” encapsulates what our brain is doing. It isn't that we stop disbelieving—it's that we believe two inconsistent things. We accept that we are sitting and reading or watching a movie. We also believe or, more accurately, feel that what we are reading or viewing is happening.

Action is the key. When we are reading a story or watching a movie, we know that we cannot or will not act to change what is occurring, a phenomenon philosopher Immanuel Kant called disinterestedness. Yet because we are not going to act, the brain economizes. We turn off the neural processes that tell us we might need to do something about what we are seeing. The prefrontal cortex does not try to assess the reality of what we are seeing, nor does it trigger motor impulses. That is why when we are sitting in a theater, we do not jump out of our seats to save the blond starlet even though we know she is about to get chopped up by a chainsaw-wielding fiend.

Losing ourselves refers to another element of poetic faith, when the audience is, in the psychologists' term, “transported.” We cease to be aware of our body, our posture or our environment. No longer are we in our living room or able to see the cinema's glowing exit sign. Perhaps most important, our limbic system causes us to feel emotions—anger, disgust, jealousy, desire, fear—about the stories we are watching or reading.

Being transported emotionally into an alternative reality helps us to invest more completely in a piece of fiction, no matter how unbelievable. Thus, we are able to believe in the supernatural occurrences in Coleridge's Ancient Mariner, the inhuman strength and speed of Superman, or the harrowing journey of a Hobbit in his quest to destroy an evil ring.

Sumber : Norman N. Holland, author of Literature and the Brain,

elephant

If you think back to history class, you might remember the tale of Hannibal’s crossing of the Alps in 218 B.C. to sneak up on Rome during the Punic Wars. It was notable not just because he brought an entire army from Carthage to Rome the long way around, but because that army included elephants.
The use of war elephants dates back at least to the fourth century B.C., when Indian kings took Asian elephants into battle. The practice soon spread west to the Persian Empire and then northern Africa, where African elephants were put to military use. There’s only one known case, though, of an African elephant-Asian elephant matchup, at theBattle of Raphia near Gaza on June 22, 217 B.C. The battle, over the sovereignty of Syria, matched the forces of Ptolemy IV, pharaoh of Egypt, against those of Antiochus III, a Greek king whose reign stretched into western Asia.
Ptolemy won the battle — but not because his elephants were any help, at least according to Greek historian Polybius, who described the encounter in his work The Histories:

A few only of Ptolemy's elephants ventured to close with those of the enemy, and now the men in the towers on the back of these beasts made a gallant fight of it, striking with their pikes at close quarters and wounding each other, while the elephants themselves fought still better, putting forth their whole strength and meeting forehead to forehead. The way in which these animals fight is as follows. With their tusks firmly interlocked they shove with all their might, each trying to force the other to give ground, until the one who proves strongest pushes aside the other's trunk, and then, when he has once made him turn and has him in the flank, he gores him with his tusks as a bull does with his horns. Most of Ptolemy's elephants, however, declined the combat, as is the habit of African elephants; for unable to stand the smell and the trumpeting of the Indian elephants, and terrified, I suppose, also by their great size and strength, they at once turn tail and take to flight before they get near them.

This account stumped later historians and naturalists. African elephants tend to be larger than Asian elephants, so what was up with Ptolemy’s elephant soldiers?
One possibility is that Ptolemy’s elephants belonged to an extinct subspecies. Another, proposed by classical scholar Sir William Gowers in 1948, holds that Ptolemy fought with smaller forest elephants (African elephants are actually two species — forest and savanna). That idea has persisted for decades.
The answer, however, lies in where Ptolemy was sourcing his war elephants.
The natural range for African elephants does not stretch into present-day Egypt. To get elephants, Ptolemy’s army looked to what is now Eritrea. Today, elephants in Eritrea are rare, numbering only 100 to 120. The population lives near the border with Ethiopia, sometimes migrating into that country. When Adam Brandt of the University of Illinois Urbana-Champaign and colleagues conducted a genetic study of those elephants — by sequencing DNA in elephant poo — they found that Eritrea’s elephants are not forest elephants; they’re savanna elephants (Loxodonta africana) with no genetic ties to either the forest or Asian species.
“Most likely, the Greek historian who wrote about the battle added in his own interpretation as to the relative size of the elephants,” study coauthor Alfred Roca of the University of Illinois Urbana-Champaign, wrote in an email. “There were semi-mythological accounts in the ancient world that attributed great size to the elephants of India, and these were probably known to Polybius, and were likely the source of his belief that Indian elephants were the largest of all.”
The Eritrean elephant population shows signs of inbreeding and isolation, the researchers report in the January-FebruaryJournal of Heredity. That’s not surprising because the population is small, and its nearest elephant neighbors are more than 400 kilometers away.
Being a small, isolated population is generally not good for survival, but Eritrea’s elephants are getting a helping hand from that nation’s agriculture ministry. The ministry is trying to minimize conflict between humans and elephants, and they’ve seen some success: The range and size of the population appears to be increasing. If these elephants need a bit of a genetic boost, though, the researchers note that their study has identified Eastern Africa savanna elephants as the population with the closest genetic affinity to the Eritrean population and best suited for any future breeding or transplantation projects.

dolphins

Swimming dolphins generate thrust just fine and have no need to compensate for supposedly underpowered muscles.

That conclusion comes from using bubbles in a pool to study dolphin swimming, says Frank E. Fish of West Chester University in Pennsylvania.

The study contradicts a storied 1936 paper by Sir James Gray, who calculated that dolphins didn’t have the muscle to produce the thrust they need to swim as fast as they do. Called “Gray’s paradox,” the work raised hopes of learning dolphins’ tricks to improve torpedoes (and swimsuits).

Scientists hypothesized that dolphins somehow reduce drag by creating smooth, laminar flow in water rushing by their skin instead of the usual turbulent flow. Soviet scientists even analyzed water-skin interactions of naked women being towed through water as stand-ins for dolphins.

To measure thrust from actual dolphins, Fish and his colleagues filmed the animals swimming through a curtain of tiny air bubbles. The frame-to-frame shifts in bubble position let the researchers work out how much thrust the dolphins produced.

A bottlenose dolphin’s flukes can generate high thrust and power without special drag-reducing tricks, the team reports January 15 in the Journal of Experimental Biology. So there’s no need for a “paradox.”