For speech recognition, specialties include vowel sounds, consonant sounds, grammar, syntax, context, and other variables. For example, a context specialty program might determine whether a speaker means to say “weigh” or “way,” or “two,” “too,” or “to.” Another program lets the controller know when a sentence is finished and the next sentence is to begin. Another program can tell the difference between a statement and a question. Using the blackboard as their forum, the specialty circuits “debate” the most likely and logical interpretations of what is heard or seen. A “referee” called a focus specialist mediates.

For object recognition, specialties might be shape, color, size, texture, height,width, depth, and other visual cues.How does a computer know if an object is a cup on a table, or a water tower a mile away? Is that a bright lamp, or is it the sun? Is that biped thing a robot, a mannequin, or a person? As with speech recognition, the blackboard serves as a debating ground.

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Perpetual motion describes “motion that continues indefinitely without any external source of energy; impossible in practice because of friction.” It can also be described as “the motion of a hypothetical machine which, once activated, would run forever unless subject to an external force or to wear”.There is a scientific consensus that perpetual motion in an isolated system would violate the first and/or second law of thermodynamics.

Cases of apparent perpetual motion can exist in nature, but either are not truly perpetual or cannot be used to do work without changing the nature of the motion.

For example, the motion of a planet around its star may appear “perpetual,” but interplanetary space is not completely frictionless, so planets’ orbital motion is very gradually slowed over time. The fly-by of a space probe past a planet can be used to speed up the probe but in doing so alters the motion and reduces the energy of the planet in its orbit around the Sun.

The flow of current in a superconducting loop can be used as an energy storage medium, but just as with a battery, using it to power a device will remove the equivalent amount of energy from the current in the loop.

Machines which extract energy from seemingly perpetual sources—such as ocean currents—are capable of moving “perpetually” (for as long as that energy source itself endures), but they are not considered to be perpetual motion machines because they are consuming energy from an external source and are not isolated systems (in reality, no system can ever be a fully isolated system).

Similarly, machines which comply with both laws of thermodynamics but access energy from obscure sources are sometimes referred to as perpetual motion machines, although they also do not meet the standard criteria for the name.

Despite the fact that successful isolated system perpetual motion devices are physically impossible in terms of the current understanding of the laws of physics, the pursuit of perpetual motion remains popular.

Links

Video Link : http://youtu.be/1nK2NkoUbes

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Wrist force is complex. Several dimensions are required to represent all the possible motions that can take place. The illustration shows a hypothetical robot wrist, and the forces that can occur there. The orientations are right/left, in/out, and up/down. Rotation is possible along all three axes. These forces are called pitch, roll, and yaw. A wrist-force sensor must detect, and translate, each of the forces independently. A change in one vector must cause a change in sensor output for that force, and no others.

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In the case of a ground-based, mobile robot, the work environment can be defined in simplistic terms using a two-dimensional (2-D) coordinate system, specifying points on the surface such as latitude and longitude. With submarine or airborne mobile robots, the work environment is three-dimensional (3-D).

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The size and shape of the work envelope depends on the coordinate geometry of the robot arm, and also on the number of degrees of freedom.Some work envelopes are flat, confined almost entirely to one horizontal plane. Others are cylindrical; still others are spherical. Some work envelopes have complicated shapes. The illustration shows a simple example of a work envelope for a robot arm using cylindrical coordinate geometry. The set of points that the end effector can reach lies within two concentric cylinders, labeled “inner limit” and “outer limit.” The work envelope for this robot arm is shaped like a new roll of wrapping tape.

When choosing a robot arm for a certain industrial purpose, it is important that the work envelope be large enough to encompass all the points that the robot arm will be required to reach. But it is wasteful to use a robot arm with a work envelope much bigger than necessary.

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The most common number of wheels is three or four. A three-wheeled robot cannot wobble, even if the surface is a little irregular. A fourwheeled robot, however, is easier to steer.

The most familiar steering scheme is to turn some or all of the wheels.This is easy to do in a four-wheeled robot. The front wheels are on one axle, and the rear wheels are on another. Either axle can be turned to steer the robot. The illustration at the upper left shows front-axle steering. Another method of robot steering is to run the wheels at different speeds. This is shown in the upper-right illustration for a three-wheeled robot turning left. The rear wheels are run by separate motors, while the front wheel is free-spinning (no motor). For the robot to turn left, the right rear wheel goes faster than the left rear wheel. To turn right, the left rear wheel must rotate faster.

A third method of steering for wheel-driven robots is to break the machine into two parts, each with two or more wheels. A joint between the sections can be turned, causing the robot to change direction. This scheme is shown in the lower illustration.

Simple wheel drive has limitations. One problem is that the surface must be fairly smooth. Otherwise the robot might get stuck or tip over. This problem can be overcome to some extent by using track-drive locomotion or tri-star wheel locomotion. Another problem occurs when the robot must go from one floor to another in a building. If elevators or ramps are not available, a wheel-driven robot is confined to one floor.However, specially built tri-star systems can enable a wheel-driven robot to climb stairs.

Another alternative to wheel drive is to provide a robot with legs. This is more expensive and is more difficult to engineer than any wheeldriven scheme.

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Forms of VR

There are three degrees, or types, of VR. They are categorized according to the extent to which the operator participates in the experience. The first two forms are sometimes called virtual virtual reality (VVR). Passive VR is, in effect, a movie with enhanced graphics and sound. You can watch, listen, and feel the show, but you have no control over what happens, nor on the general contents of the show. An example of passive VR is a ride in a virtual submarine, a small room with windows through which you can look at a rendition of the undersea world. Exploratory VR is like a movie over which you have some control of the contents. You can choose scenes to see, hear, and feel, but you cannot participate fully in the experience.An example of exploratory VR is a ride in a tour bus on an alien planet, in which you get to choose the planet. Interactive VR is what most people imagine when they think of true VR.You have nearly as much control over the virtual environment as you would have if you were really there.Your surroundings react directly to your actions. If you reach out and push a virtual object, it moves. If you speak to virtual people, they respond.

Programming

The program, or set of programs, containing all the particulars for each VR session is called the simulation manager. The complexity of the simulation manager depends on the level of VR.

One dimension: In passive VR, the simulation manager consists of a large number of frames, one representing each moment in time. The frames lend together into a space-time experience path. This can be imagined, in simplified form, as a set of points strung out along a straight line in one geometric dimension (Fig. 1). Each point represents data for one instant of time in the VR session. This is similar to the way frames exist in a movie or a videotape.

Two dimensions: In exploratory VR, there are several different sets of frames, from among which you can choose to construct the experience path. Imagine each set of frames as lying along its own individual line, as shown in Fig. 2. You choose the line through space-time along which you want to travel. (Again, this is a simplistic rendition; there are far more points in an actual exploratory VR session than are shown here.) This is similar to having a selection of movies or videotapes from which to choose.

Three dimensions: In interactive VR, the sequence of frames depends on your input from moment to moment, adding another dimension to the programming. This can be rendered as a three-dimensional space (Fig. 3). The drawing shows only a few points along one path. There can be millions upon millions of points in the interactive experience space. The number of possible experience paths is vastly larger than the number of points themselves. It is impossible to make a good analogy with movies or videotapes in this case. The software, and the required computer hardware, for interactive VR is far more powerful than that in the passive or exploratory VR experiences.

Hardware

Several hardware items, in addition to the programming, are required for VR.

Computer: For VR to be possible, even in the simplest form, a computer is necessary. The amount of computer power required depends on the sophistication of the VR session. Passive VR requires the least computer power, while exploratory VR needs more, and interactive VR takes even more. A high-end personal computer can provide passive and exploratory VR with moderate image resolution and speed. Larger computers, such as those used in file servers or that employ parallel processing (more than one microprocessor operating on a given task), are necessary for highresolution,
high-speed, and vivid interactive VR. The best interactive VR equipment is too expensive for most personal-computer users.

Robot: If the VR is intended to portray and facilitate the operation of a remotely controlled robot or telechir, that robot must have certain characteristics. In low-level VR, the telechir can be a simple vehicle that rolls on wheels or a track drive. In the most sophisticated VR telepresence systems, the telechir must be an android (humanoid robot).

Video system: This can be a simple monitor, a big screen, a set of several monitors, or a head-mounted display (HMD). The HMD gives a spectacular show, with binocular vision and sharp colors. Some HMDs shut out the operator’s view of the real world; others let the operator see the virtual universe superimposed on the real one. The HMD uses small liquid-crystal display (LCD) screens, whose images are magnified by lenses and/or reflected by mirrors to obtain the desired effects.

Sound system: Stereo, high-fidelity sound is the norm in all VR universes. Loudspeakers can be used for low-level, group VR experiences. In an individual system, a set of headphones is included in the HMD. The sound programming is synchronized with the visual programming. Speech recognition and speech synthesis can be used so that virtual people, virtual robots, or virtual space aliens can communicate their virtual thoughts and feelings to the user.

Input devices: Passive and exploratory VR systems do not need input devices, except for the media that contain the programming. Interactive systems can make use of a variety of mechanical equipment. The nature of the input device(s) depends on the VR universe. For example, driving a car requires a steering wheel, gas pedal, and brake (at least). Games need a joystick or mouse. Devices called bats and birds resemble computer mice, but are movable in three dimensions rather than only two. Levers, handles, treadmills, stationary bicycles, pulley weights, and other devices
allow for real physical activities on the part of the operator. For complete hand control, special gloves can be used. These have air bladders built in, providing a sense of touch and physical resistance, so objects seem to have substance and heft. The computer can be equipped with speech recognition and speech synthesis so that the user can talk to virtual creatures. This requires at least one sound transducer at the operating location.

A complete system: Figure 4 is a block diagram showing the hardware for a typical interactive VR system, in which the user gets the impression of riding a bicycle down a street. This can be used for exercise as well as for entertainment. The system provides sights, sounds, and variable pedal resistance as the user negotiates hills and encounters wind. If a teleoperated android is put on a real bicycle, the VR system can be used to control that robot and bicycle remotely. This would involve the addition of two wireless transceivers (one for the computer and the other for the telechir), along with modems and antennas.

Applications

Virtual reality has been used as an entertainment and excitement medium.It also has practical applications.

Instruction: Virtual reality can be used in computer-assisted instruction (CAI). For example, a person can be trained to fly an aircraft, pilot a submarine, or operate complex and dangerous machinery,without any danger of being injured or killed during training. This form of CAI has been used by the military for some time. It has also been used for training medical personnel, particularly surgeons, who can operate on “virtual patients” while they perfect their skills.

Group VR: Passive and exploratory VR can be provided to groups of people. Several theme parks in the United States and Japan have already installed equipment of this type. People sit in chairs while they watch, and listen to, the portrayal of an intergalactic journey, a submarine ride, or a trip through time. The main limitation is that everyone has the same virtual experience.

Individual VR: Interactive VR, intended for individual users, is also found in theme parks. These sessions are expensive and generally last only a few minutes. You might walk on an alien planet inhabited by robots, ride in a Moon buggy, or swim with porpoises. The environment reacts to your input from moment to moment. You might go through the same 10-min “show” 100 times and have 100 different VR experiences. Hostile environments: In conjunction with robotics,VR facilitates remote control using telepresence. This allows a human operator to safely operate machines located in dangerous places. People using such a system get illusions similar to those in theme parks, except that a robot, at some distance, follows the operator’s movements.Teleoperated robots have been
used for rescue operations, for disarming bombs, and for maintaining nuclear reactors.

Warfare: Teleoperated robot tanks, aircraft, boats, and androids (humanoid robots) can be used in combat. One person can operate a “super android”with the strength of 100 fighting men and the endurance of a well-engineered machine. Such robots are immune to deadly radiation and chemicals. They have no mortal fear, which sometimes causes human soldiers to freeze up at critical moments in combat. Exercise:Walking, jogging, riding a bike, skiing, playing golf, and playing handball are examples of virtual activities that can provide most of the benefits of the real experience. The user might not really be doing the thing, but calories are burned, and aerobic benefits are realized. There is no danger of getting maimed by a car while cycling on a virtual street, or breaking a leg while skiing down a virtual mountain. (However, outdoor people will doubtless prefer the real activity to the virtual one, no matter how realistic VR becomes.)

Escape: Another possible, but not yet widely tested, use for virtual reality is as an escape from boredom and frustration in the real world. You can put on an HMD and romp in a jungle with dinosaurs. If the monsters try to eat you, you can take the helmet off. You can walk on some unknown planet, or under the sea.You can fly high above clouds or tunnel through the center of the earth.

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The camera in a common videocassette recorder (VCR) uses a vidicon. Closed-circuit television systems, such as those in stores and banks, also employ vidicons. The main advantage of the vidicon is its small physical bulk; it is easy to carry around. This makes it ideal for use in mobile robots.

In the vidicon, a lens focuses the incoming image onto a photoconductive screen. An electron beam, generated by an electron gun, scans across the screen in a pattern of horizontal, parallel lines called the raster. As the electron beam scans the photoconductive surface, the screen becomes charged. The rate of discharge in a certain region on the screen dependson the intensity of the visible light falling on that region. The scanning in the vidicon is exactly synchronized with the scanning in the display that renders the image on the vidicon screen.

A vidicon is sensitive, so it can see things in dim light. But the dimmer the light gets, the slower the vidicon responds to changes in the image. It gets “sluggish.”This effect is noticeable when a VCR is used indoors at night. The image persistence is high under such conditions, and the resolution is comparatively low.

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The drawing shows a simple version of a two-pincher gripper. The claws are attached to a frame, and are normally held apart by springs. The claws are pulled together by means of a pair of cords that merge into a single cord as shown. This allows the gripper to pick up small, light objects.To release the grip, the cord is let go.

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The Turing test is one method that has been used in an attempt to find out if a machine can think. It was invented by logician Alan Turing.

The test is conducted by placing a male human (M), female human (F), and questioner (Q) in three separate rooms. None of the people can see the others. The rooms are soundproof, but each person has a video display terminal. In this way, the people can communicate. The object: Q must find out which person is male and which is female, on the basis of questioning them. But M and F are not required to tell the truth. Both M and F are told in advance that they may lie. The man is encouraged to lie often, and to any extent he wants. It is the man’s job to mislead the questioner into a wrong conclusion. Obviously, this makes Q’s job difficult, but the test is not complete until Q decides which room contains the man, and which contains the woman.

Suppose this test is done 1000 times, and Q is right 480 times and wrong 520 times. What will happen if the man is replaced by a computer, programmed to lie occasionally as does the man? Will Q be right more often, less often, or the same number of times as with the real man in the room?

If the man-computer has a low level of artificial intelligence (AI), then according to Turing’s hypothesis, Q will be correct more often than when a human male is at the terminal, say 700 times out of 1000. If the mancomputer has AI at a level comparable to that of a human male, Q should be right about the same number of times as when the man was at the terminal—say, correct 490 times and wrong 510 times. If the computer has AI at a level higher than that of the human male, then Q ought to bewrong most of the time—say, correct 400 times and mistaken 600 times.

The Turing test has not produced comprehensive results concerning computers with levels of AI higher than the intelligence of a human being, because no such computer has yet been developed.However, computers have been devised with high-level AI relative to specialized skills or tasks, such as board games. Powerful computers have proven equal to human masters at the game of chess, for example.

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