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  1. 1. How LCDs Workby Jeff Tyson › Introduction to How LCDs Work › Liquid Crystals › Building a Simple LCD › Backlit vs. Reflective › LCD Systems › Color › LCD Advances › Lots More Information › Shop or Compare PricesYou probably use items containing an LCD (liquid crystal display) every day. They are allaround us -- in laptop computers, digital clocks and watches, microwave ovens, CD playersand many other electronic devices. LCDs are common because they offer some realadvantages over other display technologies. They are thinner and lighter and draw much lesspower than cathode ray tubes (CRTs), for example. A simple LCD display from a calculatorBut just what are these things called liquid crystals? The name "liquid crystal" sounds like acontradiction. We think of a crystal as a solid material like quartz, usually as hard as rock,and a liquid is obviously different. How could any material combine the two?In this edition of HowStuffWorks, youll find out how liquid crystals pull off this amazing trick,and we will look at the underlying technology that makes LCDs work. Youll also learn howthe strange characteristics of liquid crystals have been used to create a new kind of shutterand how grids of these tiny shutters open and close to make patterns that representnumbers, words or images! LCD History Today, LCDs are everywhere we look, but they didnt sprout up overnight. It took a long time to get from the discovery of liquid crystals to the multitude of LCD applications we now enjoy. Liquid crystals were first discovered in 1888, by Austrian botanist Friedrich Reinitzer. Reinitzer observed that when he melted a curious cholesterol-like substance (cholesteryl benzoate), it first became a cloudy liquid and then cleared up as its temperature rose. Upon cooling, the liquid turned blue before finally crystallizing. Eighty years passed before RCA made the first experimental LCD in 1968. Since then, LCD manufacturers have steadily developed ingenious variations and improvements on the technology, taking the LCD to amazing levels of technical complexity. And there is every indication that we will continue to enjoy new LCD developments in the future
  2. 2. Liquid CrystalsWe learned in school that there are three common states of matter: solid, liquid or gaseous.Solids act the way they do because their molecules always maintain their orientation andstay in the same position with respect to one another. The molecules in liquids are just theopposite: They can change their orientation and move anywhere in the liquid. But there aresome substances that can exist in an odd state that is sort of like a liquid and sort of like asolid. When they are in this state, their molecules tend to maintain their orientation, like themolecules in a solid, but also move around to different positions, like the molecules in aliquid. This means that liquid crystals are neither a solid nor a liquid. Thats how they endedup with their seemingly contradictory name.So, do liquid crystals act like solids or liquids or something else? It turns out that liquidcrystals are closer to a liquid state than a solid. It takes a fair amount of heat to change asuitable substance from a solid into a liquid crystal, and it only takes a little more heat to turnthat same liquid crystal into a real liquid. This explains why liquid crystals are very sensitiveto temperature and why they are used to make thermometers and mood rings. It alsoexplains why a laptop computer display may act funny in cold weather or during a hot day atthe beach!Just as there are many varieties of solids and liquids, there is also a variety of liquid crystalsubstances. Depending on the temperature and particular nature of a substance, liquidcrystals can be in one of several distinct phases (see below). In this article, we will discussliquid crystals in the nematic phase, the liquid crystals that make LCDs possible.One feature of liquid crystals is that theyre affected by electric current. A particular sort ofnematic liquid crystal, called twisted nematics (TN), is naturally twisted. Applying an electriccurrent to these liquid crystals will untwist them to varying degrees, depending on thecurrents voltage. LCDs use these liquid crystals because they react predictably to electriccurrent in such a way as to control light passage. Liquid Crystal Types Most liquid crystal molecules are rod-shaped and are broadly categorized as either thermotropic or lyotropic. Image courtesy Dr. Oleg Lavrentovich, Liquid Crystal Institute Thermotropic liquid crystals will react to changes in temperature or, in some cases, pressure. The reaction of lyotropic liquid crystals, which are used in the manufacture of soaps and detergents, depends on the type of solvent they are mixed with. Thermotropic liquid crystals are either isotropic or nematic. The key difference is that the molecules in isotropic liquid crystal substances are random in their arrangement, while nematics have a definite order or pattern. The orientation of the molecules in the nematic phase is based on the director. The director can be anything from a magnetic field to a surface that has microscopic grooves in it. In the nematic phase, liquid crystals can be further classified by the way molecules orient themselves in respect to one another. Smectic, the most common arrangement, creates layers of
  3. 3. molecules. There are many variations of the smectic phase, such as smectic C, in which the molecules in each layer tilt at an angle from the previous layer. Another common phase is cholesteric, also known as chiral nematic. In this phase, the molecules twist slightly from one layer to the next, resulting in a spiral formation. Ferroelectric liquid crystals (FLCs) use liquid crystal substances that have chiral molecules in a smectic C type of arrangement because the spiral nature of these molecules allows the microsecond switching response time that make FLCs particularly suited to advanced displays. Surface-stabilized ferroelectric liquid crystals (SSFLCs) apply controlled pressure through the use of a glass plate, suppressing the spiral of the molecules to make the switching even more rapid.Building a Simple LCDTheres far more to building an LCD than simply creating a sheet of liquid crystals. Thecombination of four facts makes LCDs possible: • Light can be polarized. (See How Sunglasses Work for some fascinating information on polarization!) • Liquid crystals can transmit and change polarized light. • The structure of liquid crystals can be changed by electric current. • There are transparent substances that can conduct electricity.An LCD is a device that uses these four facts in a surprising way!To create an LCD, you take two pieces of polarized glass. A special polymer that createsmicroscopic grooves in the surface is rubbed on the side of the glass that does not have thepolarizing film on it. The grooves must be in the same direction as the polarizing film. Youthen add a coating of nematic liquid crystals to one of the filters. The grooves will causethe first layer of molecules to align with the filters orientation. Then add the second piece ofglass with the polarizing film at a right angle to the first piece. Each successive layer of TNmolecules will gradually twist until the uppermost layer is at a 90-degree angle to the bottom,matching the polarized glass filters.As light strikes the first filter, it is polarized. The molecules in each layer then guide the lightthey receive to the next layer. As the light passes through the liquid crystal layers, themolecules also change the lights plane of vibration to match their own angle. When the lightreaches the far side of the liquid crystal substance, it vibrates at the same angle as the finallayer of molecules. If the final layer is matched up with the second polarized glass filter, thenthe light will pass through.
  4. 4. If we apply an electric charge to liquid crystal molecules, they untwist! When they straightenout, they change the angle of the light passing through them so that it no longer matches theangle of the top polarizing filter. Consequently, no light can pass through that area of theLCD, which makes that area darker than the surrounding areas.Building a simple LCD is easier than you think. Your start with the sandwich of glass andliquid crystals described above and add two transparent electrodes to it. For example,imagine that you want to create the simplest possible LCD with just a single rectangularelectrode on it. The layers would look like this:The LCD needed to do this job is very basic. It has a mirror (A) in back, which makes itreflective. Then, we add a piece of glass (B) with a polarizing film on the bottom side, and acommon electrode plane (C) made of indium-tin oxide on top. A common electrode planecovers the entire area of the LCD. Above that is the layer of liquid crystal substance (D).Next comes another piece of glass (E) with an electrode in the shape of the rectangle on thebottom and, on top, another polarizing film (F), at a right angle to the first one.The electrode is hooked up to a power source like a battery. When there is no current, lightentering through the front of the LCD will simply hit the mirror and bounce right back out. Butwhen the battery supplies current to the electrodes, the liquid crystals between the common-plane electrode and the electrode shaped like a rectangle untwist and block the light in thatregion from passing through. That makes the LCD show the rectangle as a black area.
  5. 5. Backlit vs. ReflectiveNote that our simple LCD required an external light source. Liquid crystal materials emit nolight of their own. Small and inexpensive LCDs are often reflective, which means to displayanything they must reflect light from external light sources. Look at an LCD watch: Thenumbers appear where small electrodes charge the liquid crystals and make the layersuntwist so that light is not transmitting through the polarized film.Most computer displays are lit with built-in fluorescent tubes above, beside and sometimesbehind the LCD. A white diffusion panel behind the LCD redirects and scatters the lightevenly to ensure a uniform display. On its way through filters, liquid crystal layers andelectrode layers, a lot of this light is lost -- often more than half!In our example, we had a common electrode plane and a single electrode bar that controlledwhich liquid crystals responded to an electric charge. If you take the layer that contains thesingle electrode and add a few more, you can begin to build more sophisticated displays.LCD SystemsCommon-plane-based LCDs are good for simple displays that need to show the sameinformation over and over again. Watches and microwave timers fall into this category.Although the hexagonal bar shape illustrated previously is the most common form ofelectrode arrangement in such devices, almost any shape is possible. Just take a look atsome inexpensive handheld games: Playing cards, aliens, fish and slot machines are justsome of the electrode shapes youll see!There are two main types of LCDs used in computers, passive matrix and active matrix.Passive-matrix LCDs use a simple grid to supply the charge to a particular pixel on thedisplay. Creating the grid is quite a process! It starts with two glass layers called substrates.One substrate is given columns and the other is given rows made from a transparentconductive material. This is usually indium-tin oxide. The rows or columns are connected to
  6. 6. integrated circuits that control when a charge is sent down a particular column or row. Theliquid crystal material is sandwiched between the two glass substrates, and a polarizing filmis added to the outer side of each substrate. To turn on a pixel, the integrated circuit sends acharge down the correct column of one substrate and a ground activated on the correct rowof the other. The row and column intersect at the designated pixel, and that delivers thevoltage to untwist the liquid crystals at that pixel.The simplicity of the passive-matrix system is beautiful, but it has significant drawbacks,notably slow response time and imprecise voltage control. Response time refers to theLCDs ability to refresh the image displayed. The easiest way to observe slow response timein a passive-matrix LCD is to move the mouse pointer quickly from one side of the screen tothe other. You will notice a series of "ghosts" following the pointer. Imprecise voltage controlhinders the passive matrixs ability to influence only one pixel at a time. When voltage isapplied to untwist one pixel, the pixels around it also partially untwist, which makes imagesappear fuzzy and lacking in contrast.Active-matrix LCDs depend on thin film transistors (TFT). Basically, TFTs are tinyswitching transistors and capacitors. They are arranged in a matrix on a glass substrate. Toaddress a particular pixel, the proper row is switched on, and then a charge is sent down thecorrect column. Since all of the other rows that the column intersects are turned off, only thecapacitor at the designated pixel receives a charge. The capacitor is able to hold the chargeuntil the next refresh cycle. And if we carefully control the amount of voltage supplied to acrystal, we can make it untwist only enough to allow some light through. By doing this in veryexact, very small increments, LCDs can create a gray scale. Most displays today offer 256levels of brightness per pixel.
  7. 7. ColorAn LCD that can show colors must have three subpixels with red, green and blue colorfilters to create each color pixel.Through the careful control and variation of the voltage applied, the intensity of eachsubpixel can range over 256 shades. Combining the subpixels produces a possible paletteof 16.8 million colors (256 shades of red x 256 shades of green x 256 shades of blue), asshown below. These color displays take an enormous number of transistors. For example, atypical laptop computer supports resolutions up to 1,024x768. If we multiply 1,024 columnsby 768 rows by 3 subpixels, we get 2,359,296 transistors etched onto the glass! If there is aproblem with any of these transistors, it creates a "bad pixel" on the display. Most activematrix displays have a few bad pixels scattered across the screen.LCD AdvancesLCD technology is constantly evolving. LCDs today employ several variations of liquid crystaltechnology, including super twisted nematics (STN), dual scan twisted nematics (DSTN),ferroelectric liquid crystal (FLC) and surface stabilized ferroelectric liquid crystal (SSFLC).For an in-depth (and pretty technical) article that addresses all of technologies, see LiquidCrystal Materials.Display size is limited by the quality-control problems faced by manufacturers. Simply put, toincrease display size, manufacturers must add more pixels and transistors. As they increasethe number of pixels and transistors, they also increase the chance of including a badtransistor in a display. Manufacturers of existing large LCDs often reject about 40 percent ofthe panels that come off the assembly line. The level of rejection directly affects LCD pricesince the sales of the good LCDs must cover the cost of manufacturing both the good andbad ones. Only advances in manufacturing can lead to affordable displays in bigger sizes.For more information on LCDs and related topics, check out the links on the next page.
  8. 8. How Plasma Displays Workby Tom Harris › Introduction to How Plasma Displays Work › What is Plasma? › Inside the Display › Lots More Information › Shop or Compare PricesFor the past 75 years, the vast majority of televisions have been built around the sametechnology: the cathode ray tube (CRT). In a CRT television, a gun fires a beam of Photo courtesy Sony A plasma display from Sonyelectrons (negatively-charged particles) inside a large glass tube. The electrons excitephosphor atoms along the wide end of the tube (the screen), which causes the phosphoratoms to light up. The television image is produced by lighting up different areas of thephosphor coating with different colors at different intensities (see How Televisions Work for adetailed explanation).Cathode ray tubes produce crisp, vibrant images, but they do have a serious drawback: Theyare bulky. In order to increase the screen width in a CRT set, you also have to increase thelength of the tube (to give the scanning electron gun room to reach all parts of the screen).Consequently, any big-screen CRT television is going to weigh a ton and take up a sizablechunk of a room.Recently, a new alternative has
  9. 9. What is Plasma?If youve read How Televisions Work, then you understand the basic idea of a standardtelevision or monitor. Based on the information in a video signal, the television lights upthousands of tiny dots (called pixels) with a high-energy beam of electrons. In most systems,there are three pixel colors -- red, green and blue -- which are evenly distributed on thescreen. By combining these colors in different proportions, the television can produce theentire color spectrum.The basic idea of a plasma display is to illuminate tiny colored fluorescent lights to form animage. Each pixel is made up of three fluorescent lights -- a red light, a green light and a Tuning In Most plasma displays arent technically televisions, because they dont have a television tuner. The television tuner is the device that takes a television signal (the one coming from a cable wire, for example) and interprets it to create a video image. Like LCD monitors, plasma displays are just monitors that display a standard video signal. To watch television on a plasma display, you have to hook it up to a separate unit that has its own television tuner, such as a light. Just like a CRT television, the plasma display varies the intensities of the differentlights to produce a full range of colors.The central element in a fluorescent light is a plasma, a gas made up of free-flowing ions(electrically charged atoms) and electrons (negatively charged particles). Under normalconditions, a gas is mainly made up of uncharged particles. That is, the individual gas atomsinclude equal numbers of protons (positively charged particles in the atoms nucleus) andelectrons. The negatively charged electrons perfectly balance the positively charged protons,so the atom has a net charge of zero.If you introduce many free electrons into the gas by establishing an electrical voltage acrossit, the situation changes very quickly. The free electrons collide with the atoms, knockingloose other electrons. With a missing electron, an atom loses its balance. It has a netpositive charge, making it an ion.
  10. 10. In a plasma with an electrical current running through it, negatively charged particles arerushing toward the positively charged area of the plasma, and positively charged particlesare rushing toward the negatively charged area.In this mad rush, particles are constantly bumping into each other. These collisions excite thegas atoms in the plasma, causing them to release photons of energy. (For details on thisprocess, see How Fluorescent Lamps Work.)Xenon and neon atoms, the atoms used in plasma screens, release light photons whenthey are excited. Mostly, these atoms release ultraviolet light photons, which are invisible tothe human eye. But ultraviolet photons can be used to excite visible light photons, as wellsee in the next section.
  11. 11. Inside the DisplayThe xenon and neon gas in a plasma television is contained in hundreds of thousands of tinycells positioned between two plates of glass. Long electrodes are also sandwiched betweenthe glass plates, on both sides of the cells. The address electrodes sit behind the cells,along the rear glass plate. The transparent display electrodes, which are surrounded by aninsulating dielectric material and covered by a magnesium oxide protective layer, aremounted above the cell, along the front glass plate.Both sets of electrodes extend across the entire screen. The display electrodes are arrangedin horizontal rows along the screen and the address electrodes are arranged in verticalcolumns. As you can see in the diagram below, the vertical and horizontal electrodes form abasic grid.
  12. 12. To ionize the gas in a particular cell, the plasma displays computer charges the electrodesthat intersect at that cell. It does this thousands of times in a small fraction of a second,charging each cell in turn.When the intersecting electrodes are charged (with a voltage difference between them), anelectric current flows through the gas in the cell. As we saw in the last section, the currentcreates a rapid flow of charged particles, which stimulates the gas atoms to releaseultraviolet photons.The released ultraviolet photons interact with phosphor material coated on the inside wallof the cell. Phosphors are substances that give off light when they are exposed to other light.When an ultraviolet photon hits a phosphor atom in the cell, one of the phosphors electronsjumps to a higher energy level and the atom heats up. When the electron falls back to itsnormal level, it releases energy in the form of a visible light photon.
  13. 13. The phosphors in a plasma display give off colored light when they are excited. Every pixelis made up of three separate subpixel cells, each with different colored phosphors. Onesubpixel has a red light phosphor, one subpixel has a green light phosphor and one subpixelhas a blue light phosphor. These colors blend together to create the overall color of the pixel.By varying the pulses of current flowing through the different cells, the control system canincrease or decrease the intensity of each subpixel color to create hundreds of differentcombinations of red, green and blue. In this way, the control system can produce colorsacross the entire spectrum.The main advantage of plasma display technology is that you can produce a very widescreen using extremely thin materials. And because each pixel is lit individually, the image isvery bright and looks good from almost every angle. The image quality isnt quite up to thestandards of the best cathode ray tube sets, but it certainly meets most peoplesexpectations.The biggest drawback of this technology has to be the price. With prices starting at $4,000and going all the way up past $20,000, these sets arent exactly flying off the shelves. But asprices fall and technology advances, they may start to edge out the old CRT sets. In the nearfuture, setting up a new TV might be as easy as hanging a picture!To learn more about plasma displays, as well as other television technologies, check out thelinks on the next page.
  14. 14. On the most basic level, human beings are made up of five major components:
  15. 15. • A body structure Photo courtesy NASA Like you, NASAs robonaut has a movable body, brain, power system and sensor system. • A muscle system to move the body structure • A sensory system that receives information about the body and the surrounding environment • A power source to activate the muscles and sensors • A brain system that processes sensory information and tells the muscles what to doOf course, we also have some intangible attributes, such as intelligence and morality, but onthe sheer physical level, the list above about covers it.A robot is made up of the very same components. A typical robot has a movable physicalstructure, a motor of some sort, a sensor system, a power supply and a computer "brain" thatcontrols all of these elements. Essentially, robots are man-made versions of animal life --they are machines that replicate human and animal behavior.In this edition of HowStuffWorks, well explore the basic concept of robotics and find outhow robots do what they do.What is a Robot?Joseph Engelberger, a pioneer in industrial robotics, once remarked "I cant define a robot,but I know one when I see one." If you consider all the different machines people call robots,you can see that its nearly impossible to come up with a comprehensive definition.Everybody has a different idea of what constitutes a robot.Youve probably heard of several of these famous robots: • R2D2 and C-3PO: The intelligent, speaking robots with loads of personality in the Star Wars movies • Sonys AIBO: A robotic dog that learns through human interaction • Hondas ASIMO: A robot that can walk on two legs like a person • Industrial robots: Automated machines that work on assembly lines • Data: The almost human android from Star Trek • BattleBots: The remote control fighters on Comedy Central • Bomb-defusing robots • The Mars Pathfinder: NASAs exploration robot • HAL: The ships computer in Stanley Kubricks 2001: A Space Odyssey
  16. 16. • Robomower: The lawn-mowing robot from Friendly Robotics • The Robot in the television series "Lost in Space" • MindStorms: LEGOs popular robotics kitHowStuffWorks has several articles on other types of robots: • How Robotic Surgery Will Work • How Robonauts Will Work • How Snakebots Will Work • How Rumble Robots Work • How Stinger Missiles WorkAll of these things are considered robots, at least by some people. The broadest definitionaround defines a robot as anything that a lot of people recognize as a robot. Most roboticists(people who build robots) use a more precise definition. They specify that robots have areprogrammable brain (a computer) that moves a body.By this definition, robots are distinct from other movable machines, such as cars, because oftheir computer element. Many new cars do have an onboard computer, but its only there tomake small adjustments. You control most elements in the car directly by way of variousmechanical devices. Robots are distinct from ordinary computers in their physical nature --normal computers dont have a physical body attached to them.In the next section, well look at the major elements found in most robots today.Robot BasicsThe vast majority of robots do have several qualities in common. First of all, almost all robotshave a movable body. Some only have motorized wheels, and others have dozens ofmovable segments, typically made of metal or plastic. Like the bones in your body, theindividual segments are connected together with joints.
  17. 17. Robots spin wheels and pivot jointed segments with somesort of actuator. Some robots use electric motors andsolenoids as actuators; some use a hydraulic system; andsome use a pneumatic system (a system driven bycompressed gases). Robots may use all these actuator Photo courtesy NASAtypes. A robotic hand, developed by NASA, is made up of metal segments moved by tiny motors. The hand is one of the most difficult structures to replicate in robotics.A robot needs a power source to drive these actuators. Most robots either have a battery orthey plug into the wall. Hydraulic robots also need a pump to pressurize the hydraulic fluid,and pneumatic robots need an air compressor or compressed air tanks.The actuators are all wired to an electrical circuit. The circuit powers electrical motors andsolenoids directly, and it activates the hydraulic system by manipulating electrical valves.The valves determine the pressurized fluids path through the machine. To move a hydraulicleg, for example, the robots controller would open the valve leading from the fluid pump to apiston cylinder attached to that leg. The pressurized fluid would extend the piston, swivelingthe leg forward. Typically, in order to move their segments in two directions, robots usepistons that can push both ways.The robots computer controls everything attached to the circuit. To move the robot, thecomputer switches on all the necessary motors and valves. Most robots arereprogrammable -- to change the robots behavior, you simply write a new program to itscomputer.Not all robots have sensory systems, and few have the ability to see, hear, smell or taste.The most common robotic sense is the sense of movement -- the robots ability to monitor itsown motion. A standard design uses slotted wheels attached to the robots joints. An LED onone side of the wheel shines a beam of light through the slots to a light sensor on the otherside of the wheel. When the robot moves a particular joint, the slotted wheel turns. The slotsbreak the light beam as the wheel spins. The light sensor reads the pattern of the flashinglight and transmits the data to the computer. The computer can tell exactly how far the jointhas swiveled based on this pattern. This is the same basic system used in computer mice.These are the basic nuts and bolts of robotics. Roboticists can combine these elements in aninfinite number of ways to create robots of unlimited complexity. In the next section, well lookat one of the most popular designs, the robotic arm.The Robotic ArmThe term robot comes from the Czech word robota, generally translated as "forced labor."This describes the majority of robots fairly well. Most robots in the world are designed forheavy, repetitive manufacturing work. They handle tasks that are difficult, dangerous orboring to human beings.
  18. 18. Robotic arms are an essential part of car manufacturing.The most common manufacturing robot is the robotic arm. A typical robotic arm is made upof seven metal segments, joined by six joints. The computer controls the robot by rotatingindividual step motors connected to each joint (some larger arms use hydraulics orpneumatics). Unlike ordinary motors, step motors move in exact increments (check out thissite to find out how). This allows the computer to move the arm very precisely, repeatingexactly the same movement over and over again. The robot uses motion sensors to makesure it moves just the right amount.An industrial robot with six joints closely resembles a human arm -- it has the equivalent of ashoulder, an elbow and a wrist. Typically, the shoulder is mounted to a stationary basestructure rather than to a movable body. This type of robot has six degrees of freedom,meaning it can pivot in six different ways. A human arm, by comparison, has seven degreesof freedom.
  19. 19. Your arms job is to move your hand from place to place. Similarly, the robotic arms job is tomove an end effector from place to place. You can outfit robotic arms with all sorts of endeffectors, which are suited to a particular application. One common end effector is asimplified version of the hand, which can grasp and carry different objects. Robotic handsoften have built-in pressure sensors that tell the computer how hard the robot is gripping aparticular object. This keeps the robot from dropping or breaking whatever its carrying. Otherend effectors include blowtorches, drills and spray painters.Industrial robots are designed to do exactly the same thing, in a controlled environment, overand over again. For example, a robot might twist the caps onto peanut butter jars comingdown an assembly line. To teach a robot how to do its job, the programmer guides the armthrough the motions using a handheld controller. The robot stores the exact sequence ofmovements in its memory, and does it again and again every time a new unit comes downthe assembly line.Most industrial robots work in auto assembly lines, putting cars together. Robots can do a lotof this work more efficiently than human beings because they are so precise. They alwaysdrill in the exactly the same place, and they always tighten bolts with the same amount offorce, no matter how many hours theyve been working. Manufacturing robots are also veryimportant in the computer industry. It takes an incredibly precise hand to put together a tinymicrochip. Writing Robots The Czech playwright Karel Capek originated the term robot in his 1920 play "R.U.R." In the play, machine workers overthrow their human creators when a scientist gives them emotions. Dozens of authors and filmmakers have revisited this scenario over the years.
  20. 20. Isaac Asimov took a more optimistic view in several novels and short stories. In his works, robots are benign, helpful beings that adhere to a code of nonviolence against humans -- the "Laws of Robotics."Mobile RobotsRobotic arms are relatively easy to build and program because they only operate within aconfined area. Things get a bit trickier when you send a robot out into the world. Photo courtesy NASA NASAs FIDO Rover is designed for exploration on Mars.The first obstacle is to give the robot a working locomotion system. If the robot will only needto move over smooth ground, wheels or tracks are the best option. Wheels and tracks canalso work on rougher terrain if they are big enough. But robot designers often look to legsinstead, because they are more adaptable. Building legged robots also helps researchersunderstand natural locomotion -- its a useful exercise in biological research.Typically, hydraulic or pneumatic pistons move robot legs back and forth. The pistons attachto different leg segments just like muscles attach to different bones. Its a real trick getting allthese pistons to work together properly. As a baby, your brain had to figure out exactly theright combination of muscle contractions to walk upright without falling over. Similarly, arobot designer has to figure out the right combination of piston movements involved inwalking and program this information into the robots computer. Many mobile robots have abuilt-in balance system (a collection of gyroscopes, for example) that tells the computerwhen it needs to correct its movements.
  21. 21. Photo courtesy NASA NASAs Frogbot uses springs, linkages and motors to hop from place to place.Bipedal locomotion (walking on two legs) is inherently unstable, which makes it very difficultto implement in robots. To create more stable robot walkers, designers commonly look to theanimal world, specifically insects. Six-legged insects have exceptionally good balance, andthey adapt well to a wide variety of terrain.Some mobile robots are controlled by remote -- a human tells them what to do and when todo it. The remote control might communicate with the robot through an attached wire, orusing radio or infrared signals. Remote robots, often called puppet robots, are useful forexploring dangerous or inaccessible environments, such as the deep sea or inside avolcano. Some robots are only partially controlled by remote. For example, the operatormight direct the robot to go to a certain spot, but not steer it there -- the robot would find itsown way. What is it Good For? Mobile robots stand in for people in a number of ways. Some explore other planets or inhospitable areas on Earth, collecting geological samples. Others seek out landmines in former battlefields. The police sometimes use mobile robots to search for a bomb, or even to apprehend a suspect. Mobile robots also work in homes and businesses. Hospitals may use robots to transport medications. Some museums use robots to patrol their galleries at night, monitoring air quality and humidity levels. Several companies have developed robots that will vacuum your house while you sleep.
  22. 22. Autonomous MobilityAutonomous robots can act on their own, independent of any controller. The basic idea isto program the robot to respond a certain way to outside stimuli. The very simple bump-and-go robot is a good illustration of how this works.This sort of robot has a bumper sensor to detect obstacles. When you turn the robot on, itzips along in a straight line. When it finally hits an obstacle, the impact pushes in its bumpersensor. The robots programming tells it to back up, turn to the right and move forward again,in response to every bump. In this way, the robot changes direction any time it encountersan obstacle. Photo courtesy NASA The Urbie is an autonomous robot designed for various urban operations, including military reconnaissance and rescue operations.Advanced robots use more elaborate versions of this same idea. Roboticists create newprograms and sensor systems to make robots smarter and more perceptive. Today, robotscan effectively navigate a variety of environments.Simpler mobile robots use infrared or ultrasound sensors to see obstacles. These sensorswork the same way as animal echolocation: The robot sends out a sound signal or a beam ofinfrared light and detects the signals reflection. The robot locates the distance to obstaclesbased on how long it takes the signal to bounce back.More advanced robots use stereo vision to see the world around them. Two cameras givethese robots depth perception, and image-recognition software gives them the ability tolocate and classify various objects. Robots might also use microphones and smell sensors toanalyze the world around them.Some autonomous robots can only work in a familiar, constrained environment. Lawn-mowing robots, for example, depend on buried border markers to define the limits of theiryard. An office-cleaning robot might need a map of the building in order to maneuver frompoint to point.
  23. 23. More advanced robots can analyze and adapt to unfamiliar environments, even to areaswith rough terrain. These robots may associate certain terrain patterns with certain actions. Arover robot, for example, might construct a map of the land in front of it based on its visualsensors. If the map shows a very bumpy terrain pattern, the robot knows to travel anotherway. This sort of system is very useful for exploratory robots that operate on other planets(check out this page to learn more).An alternative robot design takes a less structured approach -- randomness. When this typeof robot gets stuck, it moves its appendages every which way until something works. Forcesensors work very closely with the actuators, instead of the computer directing everythingbased on a program. This is something like an ant trying to get over an obstacle -- it doesntseem to make a decision when it needs to get over an obstacle, it just keeps trying thingsuntil it gets over it.Homebrew RobotsIn the last couple of sections, we looked at the most prominent fields in the world of robots --industry robotics and research robotics. Professionals in these fields have made most of themajor advancements in robotics over the years, but they arent the only ones making robots.For decades, a small but passionate band of hobbyists has been creating robots in garagesand basements all over the world.Homebrew robotics is a rapidly expanding subculture with a sizable Web presence. Amateurroboticists cobble together their creations using commercial robot kits, mail ordercomponents, toys and even old VCRs.Homebrew robots are as varied as professional robots. Some weekend roboticists tinker withelaborate walking machines, some design their own service bots and others createcompetitive robots. The most familiar competitive robots are remote control fighters like youmight see on "BattleBots." These machines arent considered "true robots" because theydont have reprogrammable computer brains. Theyre basically souped-up remote controlcars.More advanced competitive robots are controlled by computer. Soccer robots, for example,play miniaturized soccer with no human input at all. A standard soccer bot team includesseveral individual robots that communicate with a central computer. The computer "sees" theentire soccer field with a video camera and picks out its own team members, the opponentsmembers, the ball and the goal based on their color. The computer processes thisinformation at every second and decides how to direct its own team.Check out the official RoboCup Web site for more information on Soccer robots, and thispage for information on other robot competitions. This page will give you more information onbuilding your own robots.Adaptable and UniversalThe personal computer revolution has been marked by extraordinary adaptability.Standardized hardware and programming languages let computer engineers and amateurprogrammers mold computers to their own particular purposes. Computer components aresort of like art supplies -- they have an infinite number of uses.
  24. 24. Most robots to date have been more like kitchen appliances. Roboticists build them from theground up for a fairly specific purpose. They dont adapt well to radically new applications.This situation may be changing. A new company called Evolution Robotics is pioneering theworld of adaptable robotics hardware and software. The company hopes to carve out a nichefor itself with easy-to-use "robot developer kits."The kits come with an open software platform tailored to a range of common roboticfunctions. For example, roboticists can easily give their creations the ability to follow a target,listen to voice commands and maneuver around obstacles. None of these capabilities arerevolutionary from a technology standpoint, but its unusual that you would find them in onesimple package.The kits also come with common robotics hardware that connects easily with the software.The standard kit comes with infrared sensors, motors, a microphone and a video camera.Roboticists put all these pieces together with a souped-up erector set -- a collection ofaluminum body pieces and sturdy wheels.These kits arent your run-of-the-mill construction sets, of course. At upwards of $1,000,theyre not cheap toys. But they are a big step toward a new sort of robotics. In the nearfuture, creating a new robot to clean your house or take care of your pets while youre awaymight be as simple as writing a BASIC program to balance your checkbook.The Future: AI AI in the Movies • The Matrix • AI • Blade Runner • 2001: A Space Odyssey • Demon Seed • Bicentennial Man • Westworld • The Terminator • Short CircuitArtificial intelligence (AI) is arguably the most exciting field in robotics. Its certainly themost controversial: Everybody agrees that a robot can work in an assembly line, but theresno consensus on whether a robot can ever be intelligent.Like the term "robot" itself, artificial intelligence is hard to define. Ultimate AI would be arecreation of the human thought process -- a man-made machine with our intellectualabilities. This would include the ability to learn just about anything, the ability to reason, theability to use language and the ability to formulate original ideas. Roboticists are nowherenear achieving this level of artificial intelligence, but they have had made a lot of progresswith more limited AI. Todays AI machines can replicate some specific elements ofintellectual ability.Computers can already solve problems in limited realms. The basic idea of AI problem-solving is very simple, though its execution is complicated. First, the AI robot or computer
  25. 25. gathers facts about a situation through sensors or human input. The computer compares thisinformation to stored data and decides what the information signifies. The computer runsthrough various possible actions and predicts which action will be most successful based onthe collected information. Of course, the computer can only solve problems its programmedto solve -- it doesnt have any generalized analytical ability. Chess computers are oneexample of this sort of machine.Some modern robots also have the ability to learn in a limited capacity. Learning robotsrecognize if a certain action (moving its legs in a certain way, for instance) achieved adesired result (navigating an obstacle). The robot stores this information and attempts thesuccessful action the next time it encounters the same situation. Again, modern computerscan only do this in very limited situations. They cant absorb any sort of information like ahuman can. Some robots can learn by mimicking human actions. In Japan, roboticists havetaught a robot to dance by demonstrating the moves themselves.Some robots can interact socially. Kismet, a robot at M.I.Ts Artificial Intelligence Lab,recognizes human body language and voice inflection and responds appropriately. Kismetscreators are interested in how humans and babies interact, based only on tone of speechand visual cue. This low-level interaction could be the foundation of a human-like learningsystem.Kismet and other humanoid robots at the M.I.T. AI Lab operate using an unconventionalcontrol structure. Instead of directing every action using a central computer, the robotscontrol lower-level actions with lower-level computers. The programs director, RodneyBrooks, believes this is a more accurate model of human intelligence. We do most thingsautomatically; we dont decide to do them at the highest level of consciousness.The real challenge of AI is to understand how natural intelligence works. Developing AI isntlike building an artificial heart -- scientists dont have a simple, concrete model to work from.We do know that the brain contains billions and billions of neurons, and that we think andlearn by establishing electrical connections between different neurons. But we dont knowexactly how all of these connections add up to higher reasoning, or even low-leveloperations. The complex circuitry seems incomprehensible.Because of this, AI research is largely theoretical. Scientists hypothesize on how and why welearn and think, and they experiment with their ideas using robots. Brooks and his teamfocus on humanoid robots because they feel that being able to experience the world like ahuman is essential to developing human-like intelligence. It also makes it easier for people tointeract with the robots, which potentially makes it easier for the robot to learn.Just as physical robotic design is a handy tool for understanding animal and humananatomy, AI research is useful for understanding how natural intelligence works. For someroboticists, this insight is the ultimate goal of designing robots. Others envision a world wherewe live side by side with intelligent machines and use a variety of lesser robots for manuallabor, health care and communication. A number of robotics experts predict that roboticevolution will ultimately turn us into cyborgs -- humans integrated with machines.Conceivably, people in the future could load their minds into a sturdy robot and live forthousands of years!In any case, robots will certainly play a larger role in our daily lives in the future. In thecoming decades, robots will gradually move out of the industrial and scientific worlds andinto daily life, in the same way that computers spread to the home in the 1980s.
  26. 26. The best way to understand robots is to look at specific designs. The links on the next pagewill show you a variety of robot projects around the world