The spy gadgets most in use by average consumers are home surveillance related items. These are things like cameras and listening devices that help you keep tabs on what is happening inside and outside of your home. These gadgets are not the same as having a monitored security system where someone else keeps tabs on your home. These pieces of equipment are part of a system that you control and that you use to personally ensure the safety of your home.

Cameras are among the most useful of the spy gadgets. They can be placed outside or inside the home, and come in a variety of styles. For instance, there are hidden nanny cams that look like regular household objects but that are, in fact, recording what the babysitter does with the kids when you are away. Outdoor cameras can help you identify vandals and would-be prowlers.

Listening devices, however, also have their place. Often, just a silent picture lacks context. With spy gadgets in the form of listening devices, it is possible for you to have sound with the picture. Additionally, if for some reason the visual is blocked, a sound can give you information. Just like the hidden cameras, many listening devices also come disguised as ordinary objects. Others are guarded when they think someone is listening or watching. Disguised objects helps you see who the person really is, since she or he will not realize that someone is paying close attention.

With the right spy gadgets you can protect your family, your home, and your property. All you need to do is install a surveillance system that you operate, and you can protect the things and people most precious to you with the help of spy gadgets.

So, the presented definition, as well as the rest of the material in this part of the Book, covers not just “pure” robotics or only “intelligent” robots, but rather the somewhat broader domain of robotics and automation. This includes “dumb” robots such as: metal and woodworking machines, “intelligent” washing machines, dish washers and pool cleaning robots, etc. These examples all have sensing, planning and control, but often not in individually separated components. For example, the sensing and planning behavior of the pool cleaning robot have been integrated into the mechanical design of the device, by the intelligence of the human developer.

Robotics is, to a very large extent, all about system integration, achieving a task by an actuated mechanical device, via an “intelligent” integration of components, many of which it shares with other domains, such as systems and control, computer science, character animation, machine design, computer vision, artificial intelligence, cognitive science, biomechanics, etc. In addition, the boundaries of robotics cannot be clearly defined, since also its “core” ideas, concepts and algorithms are being applied in an ever increasing number of “external” applications, and, vice versa, core technology from other domains (vision, biology, cognitive science or biomechanics, for example) are becoming crucial components in more and more modern robotic systems.

This part of the WEBook makes an effort to define what exactly is that above-mentioned core material of the robotics domain, and to describe it in a consistent and motivated structure. Nevertheless, this chosen structure is only one of the many possible “views” that one can want to have on the robotics domain.

In the same vein, the above-mentioned “definition” of robotics is not meant to be definitive or final, and it is only used as a rough framework to structure the various chapters 

Components of robotic systems

This figure depicts the components that are part of all robotic systems. The purpose of this Section is to describe the semantics of the terminology used to classify the chapters in the WEBook: “sensing”, “planning”, “modeling”, “control”, etc.

The real robot is some mechanical device (“mechanism”) that moves around in the environment, and, in doing so, physically interacts with this environment. This interaction involves the exchange of physical energy, in some form or another. Both the robot mechanism and the environment can be the “cause” of the physical interaction through “Actuation”, or experience the “effect” of the interaction, which can be measured through “Sensing”.

Robotics as an integrated system of control interacting with the physical world.

Sensing and actuation are the physical ports through which the “Controller” of the robot determines the interaction of its mechanical body with the physical world. As mentioned already before, the controller can, in one extreme, consist of software only, but in the other extreme everything can also be implemented in hardware.

Within the Controller component, several sub-activities are often identified:

Modelling. The input-output relationships of all control components can (but need not) be derived from information that is stored in a model. This model can have many forms: analytical formulas, empirical look-up tables, fuzzy rules, neural networks, etc.

The name “model” often gives rise to heated discussions among different research “schools”, and the WEBook is not interested in taking a stance in this debate: within the WEBook, “model” is to be understood with its minimal semantics: “any information that is used to determine or influence the input-output relationships of components in the Controller.”

The other components discussed below can all have models inside. A “System model” can be used to tie multiple components together, but it is clear that not all robots use a System model. The “Sensing model” and “Actuation model” contain the information with which to transform raw physical data into task-dependent information for the controller, and vice versa.

Planning. This is the activity that predicts the outcome of potential actions, and selects the “best” one. Almost by definition, planning can only be done on the basis of some sort of model.

Regulation. This component processes the outputs of the sensing and planning components, to generate an actuation setpoint. Again, this regulation activity could or could not rely on some sort of (system) model.

The term “control” is often used instead of “regulation”, but it is impossible to clearly identify the domains that use one term or the other. The meaning used in the WEBook will be clear from the context.

Scales in robotic systems

The above-mentioned “components” description of a robotic system is to be complemented by a “scale” description, i.e., the following system scales have a large influence on the specific content of the planning, sensing, modelling and control components at one particular scale, and hence also on the corresponding sections of the WEBook.

Mechanical scale. The physical volume of the robot determines to a large extent the limites of what can be done with it. Roughly speaking, a large-scale robot (such as an autonomous container crane or a space shuttle) has different capabilities and control problems than a macro robot (such as an industrial robot arm), a desktop robot (such as those “sumo” robots popular with hobbyists), or milli micro or nano robots.

Spatial scale. There are large differences between robots that act in 1D, 2D, 3D, or 6D (three positions and three orientations).

Time scale. There are large differences between robots that must react within hours, seconds, milliseconds, or microseconds.

Power density scale. A robot must be actuated in order to move, but actuators need space as well as energy, so the ratio between both determines some capabilities of the robot.

System complexity scale. The complexity of a robot system increases with the number of interactions between independent sub-systems, and the control components must adapt to this complexity.

Computational complexity scale. Robot controllers are inevitably running on real-world computing hardware, so they are constrained by the available number of computations, the available communication bandwidth, and the available memory storage.

Obviously, these scale parameters never apply completely independently to the same system. For example, a system that must react at microseconds time scale can not be of macro mechanical scale or involve a high number of communication interactions with subsystems.

Background sensitivity

Finally, no description of even scientific material is ever fully objective or context-free, in the sense that it is very difficult for contributors to the WEBook to “forget” their background when writing their contribution. In this respect, robotics has, roughly speaking, two faces: (i) the mathematical and engineering face, which is quite “standardized” in the sense that a large consensus exists about the tools and theories to use (“systems theory”), and (ii) the AI face, which is rather poorly standardized, not because of a lack of interest or research efforts, but because of the inherent complexity of “intelligent behaviour.” The terminology and systems-thinking of both backgrounds are significantly different, hence the WEBook will accomodate sections on the same material but written from various perspectives. This is not a “bug”, but a “feature”: having the different views in the context of the same WEBook can only lead to a better mutual understanding and respect.

Research in engineering robotics follows the bottom-up approach: existing and working systems are extended and made more versatile. Research in artificial intelligence robotics is top-down: assuming that a set of low-level primitives is available, how could one apply them in order to increase the “intelligence” of a system. The border between both approaches shifts continuously, as more and more “intelligence” is cast into algorithmic, system-theoretic form. For example, the response of a robot to sensor input was considered “intelligent behaviour” in the late seventies and even early eighties. Hence, it belonged to A.I. Later it was shown that many sensor-based tasks such as surface following or visual tracking could be formulated as control problems with algorithmic solutions. From then on, they did not belong to A.I. any more.

Robotics Technology

Most industrial robots have at least the following five parts:

Sensors, Effectors, Actuators, Controllers, and common effectors known as Arms.

Many other robots also have Artificial Intelligence and effectors that help it achieve Mobility.

This section discusses the basic technologies of a robot. Click one of the links above or use the navigation bar menu on the far right.

Robotics Technology — Sensors

Most robots of today are nearly deaf and blind.  Sensors can provide some limited feedback to the robot so it can do its job.  Compared to the senses and abilities of even the simplest living things, robots have a very long way to go.

The sensor sends information, in the form of electronic signals back to the cfontroller.  Sensors also give the robot controller information about its surroundings and lets it know the exact position of the arm, or the state of the world around it.

Sight, sound, touch, taste, and smell are the kinds of information we get from our world.  Robots can be designed and programmed to get specific information that is beyond what our 5 senses can tell us. For instance, a robot sensor might «see» in the dark, detect tiny amounts of invisible radiation or measure movement that is too small or fast for the human eye to see.

Here are some things sensors are used for:

Physical Property

 Technology

Contact Bump, Switch

Distance Ultrasound, Radar, Infra Red

Light Level Photo Cells, Cameras

Sound Level microphones

Strain Strain Gauges

Rotation Encoders

Magnetism Compasses

Smell Chemical

Temperature Thermal, Infra Red

Inclination Inclinometers, Gyroscope

Pressure Pressure Gauges

Altitude Altimeters

    Sensors can be made simple and complex, depending on how much information needs to be stored.  A switch is a simple on/off sensor used for turning the robot on and off.  A human retina is a complex sensor that uses more than a hundred million photosensitive elements (rods and cones).  Sensors provide information to the robots brain, which can be treated in various ways.  For example, we can simply react to the sensor output: if the switch is open, if the switch is closed, go. 

Levels of Processing

    To figure out if the switch is open or closed, you will need to measure the voltage going through the circuit, that's electronics.  Now lets say that you have a microphone and you want to recognize a voice and separate it from noise; that's signal processing.  Now you have a camera, and you want to take the pre-processed image and now you need to figure out what those objects are, perhaps by comparing them to a large library of drawings; that's computation.  Sensory data processing is a very complex thing to try and do but the robot needs this in order to have a «brain».  The brain has to have analog or digital processing capabilities, wires to connect everything, support electronics to go with the computer, and batteries to provide power for the whole thing, in order to process the sensory data.  Perception requires the robot to have sensors (power and electronics), computation (more power and electronics, and connectors (to connect it all). 

Switch Sensors

 Switches are the simplest sensors of all.  They work without processing, at the electronics (circuit) level.  Their general underlying principle is that of an open vs. closed circuit.  If a switch is open, no current can flow; if it is closed, current can flow and be detected.  This simple principle can (and is) used in a wide variety of ways.

Switch sensors can be used in a variety of ways:

contact sensors: detect when the sensor has contacted another object (e.g., triggers when a robot hits a wall or grabs an object; these can even be whiskers)

limit sensors: detect when a mechanism has moved to the end of its range

shaft encoder sensors: detects how many times a shaft turns by having a switch click (open/close) every time the shaft turns (e.g., triggers for each turn, allowing for counting rotations)

   There are many common switches: button switches, mouse switches, key board keys, phone keys, and others.  Depending on how a switch is wired, it can be normally open or normally closed.  This would of course depend on your robot's electronics, mechanics, and its task.  The simplest yet extremely useful sensor for a robot is a «bump switch» that tells it when it's bumped into something, so it can back up and turn away. Even for such a simple idea, there are many different ways of implementation.

Light Sensors

Switches measure physical contact and light sensors measure the amount of light impacting a photocell, which is basically a resistive sensor.  The resistance of a photocell is low when it is brightly illuminated, i.e., when it is very light; it is high when it is dark.  In that sense, a light sensor is really a «dark» sensor.  In setting up a photocell sensor, you will end up using the equations we learned above, because you will need to deal with the relationship of the photocell resistance photo, and the resistance and voltage in your electronics sensor circuit.  Of course since you will be building the electronics and writing the program to measure and use the output of the light sensor, you can always manipulate it to make it simpler and more intuitive.  What surrounds a light sensor affects its properties.  The sensor can be  shielded and positioned in various ways.  Multiple sensors can be arranged in useful configurations and isolate them from each other with shields.

Just like switches, light sensors can be used in many different ways:

Light sensors can measure:

light intensity (how light/dark it is)

differential intensity (difference between photocells)

break-beam (change/drop in intensity)

Light sensors can be shielded and focused in different ways

Their position and directionality on a robot can make a great deal of difference and impact

Polarized light

«Normal» light emanating from a source is non-polarized, which means it travels at all orientations with respect to the horizon.  However, if there is a polarizing filter in front of a light source, only the light waves of a given orientation of the filter will pass through.  This is useful because now we can manipulate this remaining light with other filters; if we put it through another filter with the same characteristic plane, almost all of it will get through.  But, if we use a perpendicular filter (one with a 90-degree relative characteristic angle), we will block all of the light.  Polarized light can be used to make specialized sensors out of simple photocells; if you put a filter in front of a light source and the same or a different filter in front of a photocell, you can cleverly manipulate what and how much light you detect. 

Resistive Position Sensors

    We said earlier that a photocell is a resistive device.  We can also sense resistance in response to other physical properties, such as bending.  The resistance of the device increases with the amount it is bent.  These bend sensors were originally developed for video game control (for example, Nintendo Powerglove), and are generally quite useful.  Notice that repeated bending will wear out the sensor.  Not surprisingly, a bend sensor is much less robust than light sensors, although they use the same underlying resistive principle.

Potentiometers

    These devices are very common for manual tuning; you have probably seen them in some controls (such as volume and tone on stereos).  Typically called pots, they allow the user to manually adjust the resistance.  The general idea is that the device consists of a movable tap along two fixed ends.  As the tap is moved, the resistance changes.  As you can imagine, the resistance between the two ends is fixed, but the resistance between the movable part and either end varies as the part is moved.  In robotics, pots are commonly used to sense and tune position for sliding and rotating mechanisms.

Biological Analogs

All of the sensors we described exist in biological systems

Touch/contact sensors with much more precision and complexity in all species

Bend/resistance receptors in muscles 

Reflective Optosensors

    We mentioned that if we use a light bulb in combination with a photocell, we can make a break-beam sensor. This idea is the underlying principle in reflective optosensors: the sensor consists of an emitter and a detector. Depending of the arrangement of those two relative to each other, we can get two types of sensors:

reflectance sensors (the emitter and the detector are next to each other, separated by a barrier; objects are detected when the light is reflected off them and back into the detector)

break-beam sensors (the emitter and the detector face each other; objects are detected if they interrupt the beam of light between the emitter and the detector)

    The emitter is usually made out of a light-emitting diode (an LED), and the detector is usually a photodiode/phototransistor.

    Note that these are not the same technology as resistive photocells. Resistive photocells are nice and simple, but their resistive properties make them slow; photodiodes and photo-transistors are much faster and therefore the preferred type of technology.

What can you do with this simple idea of light reflectivity? Quite a lot of useful things:

object presence detection

object distance detection

surface feature detection (finding/following markers/tape)

wall/boundary tracking

rotational shaft encoding (using encoder wheels with ridges or black & white color)

bar code decoding

    Note, however, that light reflectivity depends on the color (and other properties) of a surface. A light surface will reflect light better than a dark one, and a black surface may not reflect it at all, thus appearing invisible to a light sensor. Therefore, it may be harder (less reliable) to detect darker objects this way than lighter ones. In the case of object distance, lighter objects that are farther away will seem closer than darker objects that are not as far away. This gives you an idea of how the physical world is partially-observable. Even though we have useful sensors, we do not have complete and completely accurate information.

    Another source of noise in light sensors is ambient light. The best thing to do is subtract the ambient light level out of the sensor reading, in order to detect the actual change in the reflected light, not the ambient light. How is that done? By taking two (or more, for higher accuracy) readings of the detector, one with the emitter on, and one with it off, and subtracting the two values from each other. The result is the ambient light level, which can then be subtracted from future readings. This process is called sensor calibration. Of course, remember that ambient light levels can change, so the sensors may need to be calibrated repeatedly.

Break-beam Sensors

    We already talked about the idea of break-beam sensors. In general, any pair of compatible emitter-detector devices can be used to produce such a sensors:

an incandescent flashlight bulb and a photocell

red LEDs and visible-light-sensitive photo-transistors

or infra-red IR emitters and detectors

Shaft Encoding

Shaft encoders measure the angular rotation of an axle providing position and/or velocity info. For example, a speedometer measures how fast the wheels of a vehicle are turning, while an odometer measures the number of rotations of the wheels.

In order to detect a complete or partial rotation, we have to somehow mark the turning element. This is usually done by attaching a round disk to the shaft, and cutting notches into it. A light emitter and detector are placed on each side of the disk, so that as the notch passes between them, the light passes, and is detected; where there is no notch in the disk, no light passes.

If there is only one notch in the disk, then a rotation is detected as it happens. This is not a very good idea, since it allows only a low level of resolution for measuring speed: the smallest unit that can be measured is a full rotation. Besides, some rotations might be missed due to noise.

Usually, many notches are cut into the disk, and the light hits impacting the detector are counted. (You can see that it is important to have a fast sensor here, if the shaft turns very quickly.)

An alternative to cutting notches in the disk is to paint the disk with black (absorbing, non-reflecting) and white (highly reflecting) wedges, and measure the reflectance. In this case, the emitter and the detector are on the same side of the disk.

In either case, the output of the sensor is going to be a wave function of the light intensity. This can then be processes to produce the speed, by counting the peaks of the waves.

Note that shaft encoding measures both position and rotational velocity, by subtracting the difference in the position readings after each time interval. Velocity, on the other hand, tells us how fast a robot is moving, or if it is moving at all. There are multiple ways to use this measure:

measure the speed of a driven (active) wheel

use a passive wheel that is dragged by the robot (measure forward progress)

We can combine the position and velocity information to do more sophisticated things:

move in a straight line

rotate by an exact amount

Note, however, that doing such things is quite difficult, because wheels tend to slip (effector noise and error) and slide and there is usually some slop and backlash in the gearing mechanism. Shaft encoders can provide feedback to correct the errors, but having some error is unavoidable.

Quadrature Shaft Encoding

So far, we've talked about detecting position and velocity, but did not talk about direction of rotation. Suppose the wheel suddenly changes the direction of rotation; it would be useful for the robot to detect that.

An example of a common system that needs to measure position, velocity, and direction is a computer mouse. Without a measure of direction, a mouse is pretty useless. How is direction of rotation measured?

Quadrature shaft encoding is an elaboration of the basic break-beam idea; instead of using only one sensor, two are needed. The encoders are aligned so that their two data streams coming from the detector and one quarter cycle (90-degrees) out of phase, thus the name «quadrature». By comparing the output of the two encoders at each time step with the output of the previous time step, we can tell if there is a direction change. When the two are sampled at each time step, only one of them will change its state (i.e., go from on to off) at a time, because they are out of phase. Which one does it determines which direction the shaft is rotating. Whenever a shaft is moving in one direction, a counter is incremented, and when it turns in the opposite direction, the counter is decremented, thus keeping track of the overall position.

Other uses of quadrature shaft encoding are in robot arms with complex joints (such as rotary/ball joints; think of your knee or shoulder), Cartesian robots (and large printers) where an arm/rack moves back and forth along an axis/gear.

Modulation and Demodulation of Light

We mentioned that ambient light is a problem because it interferes with the emitted light from a light sensor. One way to get around this problem is to emit modulated light, i.e., to rapidly turn the emitter on and off. Such a signal is much easier and more reliably detected by a demodulator, which is tuned to the particular frequency of the modulated light. Not surprisingly, a detector needs to sense several on-flashes in a row in order to detect a signal, i.e., to detect its frequency. This is a small point, but it is important in writing demodulator code.

The idea of modulated IR light is commonly used; for example in household remote controls.

Modulated light sensors are generally more reliable than basic light sensors. They can be used for the same purposes: detecting the presence of an object measuring the distance to a nearby object (clever electronics required, see your course notes)

Infra Red (IR) Sensors

Infra red sensors are a type of light sensors, which function in the infra red part of the frequency spectrum.  IR sensors consist are active sensors: they consist of an emitter and a receiver.  IR sensors are used in the same ways that visible light sensors are that we have discussed so far: as break-beams and as reflectance sensors.  IR is preferable to visible light in robotics (and other) applications because it suffers a bit less from ambient interference, because it can be easily modulated, and simply because it is not visible.

IR Communication

Modulated infra red can be used as a serial line for transmitting messages. This is is fact how IR modems work. Two basic methods exist:

bit frames (sampled in the middle of each bit; assumes all bits take the same amount of time to transmit)

bit intervals (more common in commercial use; sampled at the falling edge, duration of interval between sampling determines whether it's a 0 or 1)

Ultrasonic Distance Sensing

As we mentioned before, ultrasound sensing is based on the time-of-flight principle. The emitter produces a sonar «chirp» of sound, which travels away from the source, and, if it encounters barriers, reflects from them and returns to the receiver (microphone). The amount of time it takes for the sound beam to come back is tracked (by starting a timer when the «chirp» is produced, and stopping it when the reflected sound returns), and is used to compute the distance the sound traveled. This is possible (and quite easy) because we know how fast sound travels; this is a constant, which varies slightly based on ambient temperature.

At room temperature, sound travels at 1.12 feet per millisecond. Another way to put it that sound travels at 0.89 milliseconds per foot. This is a useful constant to remember.

The process of finding one's location based on sonar is called echolocation. The inspiration for ultrasound sensing comes from nature; bats use ultrasound instead of vision (this makes sense; they live in very dark caves where vision would be largely useless). Bat sonars are extremely sophisticated compared to artificial sonars; they involve numerous different frequencies, used for finding even the tiniest fast-flying prey, and for avoiding hundreds of other bats, and communicating for finding mates.

Specular Reflection

A major disadvantage of ultrasound sensing is its susceptibility to specular reflection (specular reflection means reflection from the outer surface of the object). While the sonar sensing principle is based on the sound wave reflecting from surfaces and returning to the receiver, it is important to remember that the sound wave will not necessarily bounce off the surface and «come right back.» In fact, the direction of reflection depends on the incident angle of the sound beam and the surface. The smaller the angle, the higher the probability that the sound will merely «graze» the surface and bounce off, thus not returning to the emitter, in turn generating a false long/far-away reading. This is often called specular reflection, because smooth surfaces, with specular properties, tend to aggravate this reflection problem. Coarse surfaces produce more irregular reflections, some of which are more likely to return to the emitter. (For example, in our robotics lab on campus, we use sonar sensors, and we have lined one part of the test area with cardboard, because it has much better sonar reflectance properties than the very smooth wall behind it.)

In summary, long sonar readings can be very inaccurate, as they may result from false rather than accurate reflections. This must be taken into account when programming robots, or a robot may produce very undesirable and unsafe behavior. For example, a robot approaching a wall at a steep angle may not see the wall at all, and collide with it!

Nonetheless, sonar sensors have been successfully used for very sophisticated robotics applications, including terrain and indoor mapping, and remain a very popular sensor choice in mobile robotics.

The first commercial ultrasonic sensor was produced by Polaroid, and used to automatically measure the distance to the nearest object (presumably which is being photographed). These simple Polaroid sensors still remain the most popular off-the-shelf sonars (they come with a processor board that deals with the analog electronics). Their standard properties include:

32-foot range

30-degree beam width

sensitivity to specular reflection

shortest distance return

Polaroid sensors can be combined into phased arrays to create more sophisticated and more accurate sensors.

One can find ultrasound used in a variety of other applications; the best known one is ranging in submarines. The sonars there have much more focused and have longer-range beams. Simpler and more mundane applications involve automated «tape-measures», height measures, burglar alarms, etc.

Machine Vision

So far, we have talked about relatively simple sensors. They were simple in terms of processing of the information they returned. Now we turn to machine vision, i.e., to cameras as sensors.

Cameras, of course, model biological eyes. Needless to say, all biological eyes are more complex than any camera we know today, but, as you will see, the cameras and machine vision systems that process their perceptual information, are not simple at all! In fact, machine vision is such a challenging topic that it has historically been a separate branch of Artificial Intelligence.

The general principle of a camera is that of light, scattered from objects in the environment (those are called the scene), goes through an opening («iris», in the simplest case a pin hole, in the more sophisticated case a lens), and impinging on what is called the image plane. In biological systems, the image plane is the retina, which is attached to numerous rods and cones (photosensitive elements) which, in turn, are attached to nerves which perform so-called «early vision», and then pass information on throughout the brain to do «higher-level» vision processing. As we mentioned before, a very large percentage of the human (and other animal) brain is dedicated to visual processing, so this is a highly complex endeavor.

In cameras, instead of having photosensitive rhodopsin and rods and cones, we use silver halides on photographic film, or silicon circuits in charge-coupled devices (CCD) cameras. In all cases, some information about the incoming light (e.g., intensity, color) is detected by these photosensitive elements on the image plane.

In machine vision, the computer must make sense out of the information it gets on the image plane. If the camera is very simple, and uses a tiny pin hole, then some computation is required to compute the projection of the objects from the environment onto the image plane (note, they will be inverted). If a lens is involved (as in vertebrate eyes and real cameras), then more light can get in, but at the price of being focused; only objects a particular range of distances from the lens will be in focus. This range of distances is called the camera's depth of field.

The image plane is usually subdivided into equal parts, called pixels, typically arranged in a rectangular grid. In a typical camera there are 512 by 512 pixels on the image plane (for comparison, there are 120 x 10^6 rods and 6 x 10^6 cones in the eye, arranged hexagonally). Let's call the projection on the image plane the image.

The brightness of each pixel in the image is proportional to the amount of light directed toward the camera by the surface patch of the object that projects to that pixel. (This of course depends on the reflectance properties of the surface patch, the position and distribution of the light sources in the environment, and the amount of light reflected from other objects in the scene onto the surface patch.) As it turns out, brightness of a patch depends on two kinds of reflections, one being specular (off the surface, as we saw before), and the other being diffuse (light that penetrates into the object, is absorbed, and then re-emitted). To correctly model light reflection, as well as reconstruct the scene, all these properties are necessary.

Let us suppose that we are dealing with a black and white camera with a 512 x 512 pixel image plane. Now we have an image, which is a collection of those pixels, each of which is an intensity between white and black. To find an object in that image (if there is one, we of course don't know a priori), the typical first step («early vision») is to do edge detection, i.e., find all the edges. How do we recognize them? We define edges as curves in the image plane across which there is significant change in the brightness.

A simple approach would be to look for sharp brightness changes by differentiating the image and look for areas where the magnitude of the derivative is large. This almost works, but unfortunately it produces all sorts of spurious peaks, i.e., noise. Also, we cannot inherently distinguish changes in intensities due to shadows from those due to physical objects. But let's forget that for now and think about noise. How do we deal with noise?

We do smoothing, i.e., we apply a mathematical procedure called convolution, which finds and eliminates the isolated peaks. Convolution, in effect, applies a filter to the image. In fact, in order to find arbitrary edges in the image, we need to convolve the image with many filters with different orientations. Fortunately, the relatively complicated mathematics involved in edge detection has been well studied, and by now there are standard and preferred approaches to edge detection.

Once we have edges, the next thing to do is try to find objects among all those edges. Segmentation is the process of dividing up or organizing the image into parts that correspond to continuous objects. But how do we know which lines correspond to which objects, and what makes an object? There are several cues we can use to detect objects:

We can have stored models of line-drawings of objects (from many possible angles, and at many different possible scales!), and then compare those with all possible combinations of edges in the image. Notice that this is a very computationally intensive and expensive process. This general approach, which has been studied extensively, is called model-based vision.

We can take advantage of motion. If we look at an image at two consecutive time-steps, and we move the camera in between, each continuous solid objects (which obeys physical laws) will move as one, i.e., its brightness properties will be conserved. This hives us a hint for finding objects, by subtracting two images from each other. But notice that this also depends on knowing well how we moved the camera relative to the scene (direction, distance), and that nothing was moving in the scene at the time. This general approach, which has also been studied extensively, is called motion vision.

We can use stereo (i.e., binocular stereopsis, two eyes/cameras/points of view). Just like with motion vision above, but without having to actually move, we get two images, which we can subtract from each other, if we know what the disparity between them should be, i.e., if we know how the two cameras are organized/positioned relative to each other.

We can use texture. Patches that have uniform texture are consistent, and have almost identical brightness, so we can assume they come from the same object. By extracting those we can get a hint about what parts may belong to the same object in the scene.

We can also use shading and contours in a similar fashion. And there are many other methods, involving object shape and projective invariants, etc.

Note that all of the above strategies are employed in biological vision. It's hard to recognize unexpected objects or totally novel ones (because we don't have the models at all, or not at the ready). Movement helps catch our attention. Stereo, i.e., two eyes, is critical, and all carnivores use it (they have two eyes pointing in the same direction, unlike herbivores). The brain does an excellent job of quickly extracting the information we need for the scene.

Machine vision has the same task of doing real-time vision. But this is, as we have seen, a very difficult task. Often, an alternative to trying to do all of the steps above in order to do object recognition, it is possible to simplify the vision problem in various ways:

Use color; look for specifically and uniquely colored objects, and recognize them that way (such as stop signs, for example)

Use a small image plane; instead of a full 512 x 512 pixel array, we can reduce our view to much less, for example just a line (that's called a linear CCD). Of course there is much less information in the image, but if we are clever, and know what to expect, we can process what we see quickly and usefully.

Use other, simpler and faster, sensors, and combine those with vision. For example, IR cameras isolate people by body-temperature. Grippers allow us to touch and move objects, after which we can be sure they exist.

Use information about the environment; if you know you will be driving on the road which has white lines, look specifically for those lines at the right places in the image. This is how first and still fastest road and highway robotic driving is done.

Those and many other clever techniques have to be employed when we consider how important it is to «see» in real-time. Consider highway driving as an important and growing application of robotics and AI. Everything is moving so quickly, that the system must perceive and act in time to react protectively and safely, as well as intelligently.

Now that you know how complex vision is, you can see why it was not used on the first robots, and it is still not used for all applications, and definitely not on simple robots. A robot can be extremely useful without vision, but some tasks demand it. As always, it is critical to think about the proper match between the robot's sensors and the task.

Washing Machine

Now can you imagine if we had to do all the laundry by hand. Today we have Laundromats if you can’t have a washing machine at home, but when the first washing machine was made, we are sure the housewife said a prayer of thanks. Washing clothes is truly a back breaking endeavour, as doing everything by hand can be tedious. Today we have top or front opening washing machines, with an inbuilt dryer in some, so that when your clothes come out of the washer/dryer, all you need to do is press them and you are ready to go.

The Iron

In the old days, irons were quite a contraption and were extremely heavy. The iron used to be a huge block of iron material with a handle on top. This had to be kept on a heated plate, which was generally heated over the kitchen fire. Then after sprinkling some water on the cloth the now heated iron block was used to iron out the cloth. This took a lot of energy and you eventually ended up with a nasty burn. Today, electric steam irons combine the advantages of steam into your ironing to give you crease free clothes.

Telephone

Yes, the telephone we use is an electrical appliance. It required electric power to be used. Today, phone lines are independent of our electricity lines, but they still are running because of electricity. Earlier, there was the telegram that could be transfer only a small message, but today it does not take more than a few seconds to connect to someone across the globe and it sounds like the person is standing right next to you. Mobile phones have taken the telephone invention to another level. Today you will rarely find a person without a mobile phone. Today companies like Nokia, Samsung and Sony are all leading mobile brand manufacturers.

Lights

Of course, after Edison said “and there was light”, we all gave thanks to the man for ridding us from the darkness. The constant use of candles to light up a room was expensive and time consuming. Of course, when the first bulb was made, it too was an expensive option and only the very rich could afford electricity bills and the bulb cost. Today, you have different kinds of lights from your normal yellow light to your CFC lights to neon lights, etc. Today you don’t even need electricity to power your lights and it can be done by solar power.

Car

The car is primarily run on fuel but electricity is required in a small part to keep the battery of the car running, as the battery is required to run the car efficiently and power the engine. You also need the battery to operate the lights and other thing like the horn, windshield wipers, radio, A/C, etc, and this is what makes driving a pleasure.

Television

When the first black and white television came out, watching people on the screen must have been a novel experience. Today, we are more than used to the streamlined excellent quality of digital television. With the development of LCD and Plasma TVs we have images that look like the real thing and make viewing a truly pleasurable experience. If you are looking for the best quality LCD home theatre systems and more, you could check out Online Electronics, as they have everything you could want. For more info, check out www.onlineelectronics.net.au

Number recognition
Introduce the joys of mathematics early to a young boy and help nurture a love for numbers.  There are several great electronic educational toys that young boys will love, including oversized talking calculators that teach basic mathematics such as addition, subtraction, multiplication and division.  These are colorful toys, which children find quite attractive.  Battery power means these electronic toys can be carried anywhere.

Another great addition for your child's collection is the electronic numbers mat.  It consists of several mats with corresponding numbers and images.  When pressed, the image reads the numbers out loud.  Excellent for assisting young boys in learning to recognize and count numbers.  Mats with images emit animal sounds.

Sequencing games
When there are electronic educational toys, sequencing games no longer have to be boring stuff.  Engage your young boys in hours of fun, play and learning.  An excellent electronic toy to look for is the one offered by LeapFrog — children manipulate components of the toy to create patterns and even play melodies.  Helps focus not just on creativity and reasoning but also in developing children's motor skills.

Building toys
Lego bricks are great but there are many electronic educational toys designed for young boys that encourage them to build and create another toy out of several components.  Consider getting your child a radio and electronics set of a basic circuitry board.  All components come in a box with instructions.  

To build the toy itself, the child follows the instructions provided in an easy to read manual.  Once he's done, he will be able to make his own radio, for example, or a simple circuits board that has a computer interface or even a simple robot that comes with a sensor.  Helps encourage creativity and scientific thinking; also helps develop focus.

Electronic educational toys such as these are best for older boys.  Some components are small enough to be choking hazards, so avoid giving to a young child.

Science kit
There is a wide variety of electronic educational toys that young boys will find interesting, particularly if they are fond of science.  Consider kits such as those that introduce your child to magnets, electricity, electromagnets, radio, sound, motion, computers and light.  Try puzzles that combine light and sound or radio-controlled toys.  For older kids, try the 100-in-1 or 200-in-1 electronic project kits that will provide them with neverending fun and learning.

When it comes to saving energy while cooling or heating your homes, use an electronic thermostat to control the temperature. These are far more energy efficient than the conventional electromechanical thermostats. Also remember to fix the temperature of the air conditioner to 24 degrees. This is the most comfortable temperature and uses the least energy to cool the place.

Lighting is another part of civilization that takes up a whole lot of energy. Using florescent lighting can bring down the energy consumption by over 50 percent. Since lighting uses up over 40 percent of the energy of a home changing over to florescent lighting will lead to substantial energy conservation as well as hard cash saved.

While industries and scientists strive to make gadgets more efficient it is a fact that the smaller and lighter the gadget is the more energy efficient it will be.

Electronics Engineering has evolved today as one of the fastest growing and most in-demand industries. It encompasses a wide array of applications we use daily. These applications are television, radio, computers, telecommunication, etc. that play a vital role in making our life more easier and enjoyable than before. Using them we can see, hear and communicate even over vast distances. They really help us to move with the current scenario. Electronics also play an important role in enhancing productivity in various industries, including oil, energy, agriculture and so many other important sectors of economy.

There are a range of electronic devices that direct, control and test production processes in a variety of industries, such as steel, petroleum and chemical. It also offers a huge collection of electronic instruments for the health care industry to perform chemic tests and to check body functions. It also enables people to perform various tasks while working in homes, factories and mines and even in transport sectors. As a result, its uses are endless. Career Options in Engineering.

An electronics engineer is able to find an array of advanced solutions for the practical problems that affect our daily lives. An electronics engineer will have to perform their tasks summing up with other specialists to supervise, test, produce, fabricate and design the manufacture of complex products and systems i.e electronic equipments and components for a number of industries, including hospitals, computer industry, electronic data processing systems for communication and in defense etc. The production and manufacturing processes are done under their supervision. They also oversee installation and maintenance. They are also responsible for working their tasks with devices that use extremely small amounts of power. Electronics engineers work with microprocessors, fibre optics, and in telecommunication, television, radio etc.

Without any doubt, Career in Electronics Engineering has become today as a constantly changing and widening branch of the engineering profession. Being a labour intensive industry, electronics industry offers a range of job opportunities for the skilled job seekers. The increased production and demand of the government and non-government companies for the communication equipments, computers and military electronics along with consumer demand and increased research and development on robots have compelled the engineering colleges and universities to offer industry-oriented courses for those aspiring for a Career in Engineering. Aspirants having a creative and innovative mind and also are good at physics and mathematics will probably find electronics engineering a challenging and lucrative career.

Eligibility & Course Area :

Educational : To become a professional engineer you need to earn a degree in electronics engineering (BE / B.Tech) or must have earned the AMIE (Associate Membership Examination of the Institute of Engineers) in electronics or Graduate membership Examination of the Institution of Electronics and Telecommunication Engineers or at least a diploma in Electronics Engineering. If you are looking for research or teaching posts and management positions then you should have a post graduate degree in engineering. Aspirants looking for administrative or management positions, must have an additional degree in business administration.

Candidates, who want to enter into a BE / B.Tech, must clear their 10+2 or equivalent examination, with Physics, Chemistry and Mathematics. It is not easy task to get admission into these courses. For this purpose, candidates must have an excellent academic record in the final exams of 10+2. Aspirants who have secured good marks in the entrance test of engineering. Aspirants can enter into the IITs through the entrance test of 'JEE' (Joint Entrance Exam) while for other major institutions AIEEE (All India Engineering/Pharmacy/Architecture Entrance Examination) is conducted.

Duration :

Any engineering college or university take four years to give degree for BE / B.Tech courses. The diploma courses in polytechnics are of 3 years duration.

Personal Attributes :

Aspirants, having an interest in physics and mathematics, who have a creative and inventive mind can go to make their career in the field of engineering. They must have excellent analytical skills, an eye for detail, sustained attention and the ability to work as part of a team. Good communication skills are also required for achieving the respected jobs in this field.

Job Prospects & Career Option:

An electronics engineer can find a job in Central Government, State Governments and their sponsored corporations in public enterprises and the private organizations such as Bharat Electronics Limited, National Physical Laboratory, Co-ordination Department, Post and Telegraph Department, Civil Aviation Department, AIR, National Physical Laboratories, MTNL, Indian Telephone Industries andAll India Radio, etc. dealing in manufacture, sales and services of electronics consumer goods and appliances. These professionals also get jobs in the entertainment transmission industry, research establishments, and defense. They can also absorb into the teaching and research in one of the many engineering colleges in India or abroad.

Career Options

As an Electronic Engineer candidate can place for junior posts in the Government departments by direct recruitment. Candidates get to know about it through advertisements printed in newspapers. The Union and State Public Service Commission can conduct competitive examinations for the post of gazetted officers. The UPSC organises an Engineering Service Examination (Telecommunication and Electronics Engineering group) annually for job vacancies in Central Engineering Services and various State Public Service commissions organise their own competitive Exams for job vacancies in State engineering services.

Remuneration :

Earnings of an electronic engineer vary with market demand and among organisations.

Institutes :

Indian institute of Technology (IIT's) in New Delhi, Guwahati, Kanpur, Mumbai, Kharagpur etc are the most prestigious Engineering institutions in India. Other main Engineering colleges include Delhi College of Engineering, Delhi, University of Roorkee, Roorkee, Uttar Pradesh and Birla Institute of Technology (BITS) — (Pilani and Ranchi) etc and the various Regional engineering colleges in different states.

Pivot points can help traders determine a couple of things. First of all, these points can help determine the market entrance and exit prices for a specific trade, alerting the trader that it is time to buy or sell depending on the situation. These points can also help determine the current trend of the market, and are only one technical analysis tool among many that can be used. Day trading on the S&P 500 e-mini is the perfect way to utilize pivot points, because this analysis tool is best when used for short term trading. The actual pivot points will be different every day, and must be recalculated before trading starts that day. One strategy when it comes to pivot points is to buy when the resistance price is broken, and to sell when the trade breaks the support level.

To use pivot points successfully it is necessary to determine the price where the biggest movement of the market will happen, and the history from the movements of the day before makes it much easier to do this. When used together with other support and resistance levels, which can also help predict significant market fluctuations, pivot points can help protect against large losses due to market volatility. Once the pivot points have been set, other technical analysis tools should also be used, possibly including candlestick patterns and others, to help pinpoint market movements even more. When positive predictions are shown by more than one of the technical analysis tools, the odds of the trade being successful become even greater.

Day trading on the S&P 500 e-mini can be done successfully, and pivot points are part of this equation. This method of analysis can be successful or not, depending on how effectively it is used by the specific trader. These points can be used together with the moving averages for a prediction about specific trades as well, to increase the level of success seen. This will allow any positive trading opportunities of the day to be pinpointed, so that the trader can use these times to their advantage. The S&P 500 e-mini offers higher volatility levels, meaning bigger possible rewards, and a big exposure to the market without a high price. The contracts which are traded on this exchange are only a fraction of the amount which are used for commercial contracts, so the initial investment costs are also less.

You may certainly be surprised when you see a photo in a key chain move or change. After all, we all have been used to seeing key chains with static photos. We do not often see key chains with moving photos. Now, thanks to technology and electronics, ordinary people would have to get used to seeing pictures change even in key chains.

We do know that technology has certainly allowed for various things to be possible. However, we all cannot help but be amazed the first time we see something different from what we all have been accustomed to. One example is the key chain which can actually change pictures. Now that gadget is known as a digital photo key chain and such a product is available over at Gadget Epoint.

This digital photo key chain is certainly something to be enthralled with. And this is certainly one kind of gadget that you would want to give as a gift when you cannot think of anything good to give. Sure, the person who would be receiving this digital photo key chain would be happy knowing that he/she can actually store tons of photos in it and show it off to the rest of the world.

A digital photo key chain is not a huge gadget. In fact, it measures only 1.1 inches. But despite that small size, you can certainly think of it as a really good photo album which you can use to store your photos and show them all to anybody who dares to see. There would be no need for you to take out your mobile phone or maybe even that bulky photo album you always bring with you when you are visiting friends and relatives. All you need is this piece of electronics and you're all set.

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Our look at Forex Megadroid's toolbox begins with its broker protection feature, or «stealth mode». The brutal fact is, some Metatrader brokers trade against their clients, and things like high spreads, off quote errors and slippage make it difficult for trading robots such as Forex Megadroid to consistently earn profits. This software levels that playing field with features that preventing brokers from discovering it.

Next is the vaunted RCTPA. Changing market conditions are the bane of any automated Forex trading program; the chaos of the Forex market means that most robots are only sporadically effective, perhaps making incredible amounts of money at one time only to bleed cash at another. Not so with Forex Megadroid. There is no such thing yet as an electronic crystal ball, but RCTPA comes tantalizingly close: its claims of being able to predict market conditions 2-4 hours in advance have not only been verified and proven, but it continues to make money for those who have trusted their investments to this software.

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Your purchase comes with access to the members area of the site, where you can download the program's latest version as well as a 78-page installation manual in ebook format. Sounds daunting? Not in the least. The manual provides a complete walkthrough of installation and setup, illustrated with screenshots of the entire process.

Forex Megadroid lives up to its creators' claims. With incredible 95.82% accuracy, this software's reliability cannot be argued against. Whether you're a newcomer looking to make money through Forex trading or a veteran trader looking to enhance your trading operation, this software can be a valuable addition to your repertoire.

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At first, you may think that it is just an ordinary card that you see everyday. However, if you are going to take an even closer look at this electronics piece that is available at Gadget Epoint, then you would surely know that it is more than what it seems to be. See, this alarm card, as its name goes, has an alarm so much so that when someone tries to steal your valuables or whatever important thing you have with you, the alarm card goes off and you are immediately alerted. Now that is really a good piece of gadget, do you not think so?

The alarm card is really so ordinary-looking that those with bad intent would not surely give much importance to take a look at it. In fact, they may even discard it as just your ordinary ATM card or credit card or debit card. But see, the alarm card has a photo sensor that is very sensitive so that when someone tries to get to what it is guarding, an alarm will sound off. Now that alarm is actually going to come from the alarm card's micro speaker which has been built right into it. Really, this alarm card is very interesting with all the features that it comes with.

With that, you definitely would want to have this piece of electronics with you. You can place it right inside your bag or your favorite purse and never have to mind about the safety because the alarm card is there to guard the things you hold dear inside your bag or purse.