Gibilisco S. Teach Yourself Electricity and Electronics

Подождите немного. Документ загружается.

Edge Detection

The term edge detection refers to the ability of a robot vision system to locate boundaries. It also

refers to the robot’s knowledge of what to do with respect to those boundaries. A robot car, bus,

or truck can use edge detection to see the edges of a road and use the data to keep itself on the

road. But it must stay a certain distance from the right-hand edge of the pavement to avoid cross-

ing into the lane of oncoming traffic (Fig. 34-11). It also must stay off the road shoulder. It must

be able to tell the difference between pavement and other surfaces, such as gravel, grass, sand, and

snow.

The interior of a home or business contains straight-line edge boundaries of all kinds, and each

boundary represents a potential point of reference for a mobile robot’s edge detection system. The

controller in a personal home robot must be programmed to know the difference between, say, the

line where carpet ends and tile begins, and the line where a flight of stairs begins. The vertical line

produced by the intersection of two walls would present a different situation than the vertical line

produced by the edge of a doorway, even though they might appear identical. Thus, edge detection

cannot function very well without a certain amount of AI in the robot controller.

Embedded Path

An embedded path is a means of guiding a robot along a specific route. This scheme is commonly

used by a mobile robot called an automated guided vehicle (AGV). A common embedded path con-

sists of a buried, current-carrying wire. The current in the wire produces a magnetic field that the

robot can follow. This method of guidance has been suggested as a way to keep a car on a highway,

even if the driver isn’t paying attention. The wire needs a constant supply of electricity for this guid-

ance method to work. If this current is interrupted for any reason, the robot will lose its way unless

some backup navigation method (or human control) is substituted.

Alternatives to wires, such as colored or reflective paints or tapes, do not need a supply of power,

and this gives them an advantage. Tape is easy to remove and put somewhere else; this is difficult to

do with paint and practically impossible with wires embedded in concrete. However, tape is ob-

scured by snowfall; and at night, glare from oncoming headlights might be confused for reflections

from the tape.

Robot Navigation 601

34-10 Response functions

for clinometers. At A,

the output voltage is

a simple function of

slope. At B, up-slope

causes positive

output voltage;

downslope causes

negative output

voltage.

Range Sensing and Plotting

Range sensing is the measurement of distances to objects in a robot’s environment in a single dimen-

sion. Range plotting is the creation of a graph of the distance (range) to objects, as a function of the

direction in two or three dimensions.

In linear or one-dimensional (1D) range sensing, a signal is sent out, and the robot measures

the time it takes for the echo to come back. This signal can be sound, in which case the device is

sonar. Or it can be a radio wave; this constitutes radar. Laser beams can also be used. Close-range,

one-dimensional range sensing is known as proximity sensing.

Two-dimensional (2D) range plotting involves mapping the distance to various objects, as a

function of direction in a geometric plane. The echo return time for a sonar signal, for example,

might be measured every few degrees around a complete circle in the horizontal plane, resulting

in a set of range points. A better plot would be obtained if the range were plotted every degree,

every tenth of a degree, or even every hundredth of a degree. But no matter how detailed the di-

rection resolution, a 2D range plot is done in only one plane, such as the floor level in a room, or

some horizontal plane above the floor. The greater the number of echo samples in a complete cir-

cle (that is, the smaller the angle between samples), the more detail can be resolved at a given dis-

tance from the robot, and the greater the distance at which a given amount of detail can be

resolved.

Three-dimensional (3D) range plotting is done in spherical coordinates: azimuth (compass

bearing), elevation (degrees above the horizontal), and range (distance). The distance must be mea-

sured for a large number of diverse orientations. In a furnished room, a 3D sonar range plot would

show ceiling fixtures, things on the floor, objects on top of a desk, and other details not visible with

a 2D plot. The greater the number of echo samples in a complete sphere surrounding the robot, the

more detail can be resolved at a given distance, and the greater the range at which a given amount

of detail can be resolved.

602 Monitoring, Robotics, and Artificial Intelligence

34-11 In edge detection, a

robot uses visual

boundaries to

facilitate navigation.

This is what the

controller might see

in a robot car driving

down the center line

of a highway.

Telepresence

Telepresence is a refined, advanced form of robot remote control. The robot operator gets a sense

of being “on location,” even if the remotely controlled machine, or telechir, and the operator are

miles apart. Control and feedback are done by means of telemetry sent over wires, optical fibers,

or radio.

What It’s Like

Here is an example of a telepresence scenario. The robot is autonomous and has a humanoid form.

The control station consists of a suit that you wear or a chair in which you sit with various manip-

ulators and displays. Sensors can give you feelings of pressure, sight, and sound. You wear a helmet

with a viewing screen that shows whatever the robot camera sees. When your head turns, the robot

head, with its vision system, follows, so you see an image that changes as you turn your head, as if

you were in a space suit or diving suit at the location of the robot. Binocular machine vision pro-

vides a sense of depth. Binaural machine hearing allows you to perceive sounds. Special vision

modes let you see UV or IR; special hearing modes let you hear ultrasound or infrasound.

A telechir can be propelled by means of a track drive (similar to those used by military tanks), a

wheel drive, or robot legs. If the propulsion uses legs, you propel the telechir by literally walking

around a room in your telepresence suit! In the case of track drive or wheel drive, you sit in a chair

and drive the robot like a tank or a car. The telechir, which is a form of android, has two arms, each

with grippers resembling human hands. When you want to pick something up, you go through the

normal motions with your own hands. Back-pressure sensors and position sensors let you feel (to a

limited extent) what’s going on. If an object masses 1 kg, it feels as if it masses 1 kg because of re-

sistance provided by the back-pressure sensors. But it will be as if you’re wearing thick gloves; you

won’t be able to feel texture. You might throw a switch, and something that masses 10 kg feels as if

it masses only 1 kg. This might be called “strength × 10” mode. If you switch to “strength × 100”

mode, a 100-kg object seems to mass only 1 kg.

Functional Description

Figure 34-12 is a simplified diagram of a robot telepresence system using an android and a wireless

control link.

At the control end of the system (where the human operator is), electromechanical transducers

convert the human operator’s movements into electrical signals. The modem converts these signals

into analog form. The analog signals modulate the RF produced by the transceiver, which in turn

transmits commands by wireless to the telechir end of the system. Radio signals from the telechir ar-

rive at the operator-end transceiver. These signals are converted into analog impulses, and are trans-

lated by the modem into electrical signals that power transducers, giving the operator a sense of

what is going on.

At the telechir end of the system, the transceiver receives control signals from the human oper-

ator. These signals are translated by the modem into impulses that drive electromechanical trans-

ducers, propelling or manipulating the telechir. Data obtained by the telechir, such as its visual sense

of position, environmental sounds, or the apparent mass of a lifted object, are converted by the

modem into electrical signals. These signals modulate the RF energy produced by the transceiver.

Signals are thus sent back to the operator end by wireless.

Telepresence 603

Applications

Here are a few potential applications for a telepresence system using a human operator and an an-

droid:

• Working in extreme heat or cold

• Working under high pressure, such as on the sea floor

• Working in a vacuum, such as in space

• Working where there is dangerous radiation

• Disarming bombs

• Handling toxic substances

• Serving in high-risk police or military situations

Of course, the robot must be able to survive conditions at its location. Also, it must have some way

to recover if it falls or gets knocked over.

Limitations

The technology for telepresence has existed for some time. But certain logistical problems have al-

ways bedeviled engineers committed to developing such systems.

The most serious limitation is the fact that telemetry cannot, and never will, travel faster than

the speed of light in free space. This is not a problem over short-range links (a few hundred kilome-

604 Monitoring, Robotics, and Artificial Intelligence

34-12 Telepresence

combines remote

monitoring and

control, giving the

operator the feeling

of being onsite at

a distant location.

ters or less), but it is slow in outer space, and nigh impractical in interplanetary operations. The

moon is approximately 1.3 light-seconds away from the earth; that means that any command sent

to a telechir from the earth to the moon takes 1.3 s to get there, and any data from the telechir takes

another 1.3 s to get back. For planets in the solar system, the delay is on the order of several min-

utes to several hours. On an interstellar scale, telepresence is out of the question. The nearest stars

are at distances of several light-years.

Another problem is the resolution of the robot’s vision. A human being with good eyesight can

see things in considerable detail. To send images in real-life detail, at reasonable speed, requires a sig-

nal with broad bandwidth. There are engineering problems (and cost problems) that go along with

this. However, if one is willing to deal with the cost and accommodate the signal bandwidth, robot

vision systems can be designed that offer optical resolution superior to human eyesight.

Still another limitation is best put as a question: How will a robot be able to feel something and

transmit these impulses to the human brain? For example, an apple feels smooth, a peach feels fuzzy,

and an orange feels shiny yet bumpy. How can this sense of texture be realistically transmitted to the

human brain?

The Mind of the Machine

A simple electronic calculator doesn’t have AI. But a machine that can learn from its mistakes, or

that can show reasoning power, does. Between these extremes, there is no precise dividing line. As

computers become more powerful, people tend to set higher standards for what they call AI. Things

that were once thought of as AI are now ordinary. Things that seem fantastic now will someday be

humdrum. There is a tongue-in-cheek axiom: We can call “computer intelligence” true AI only as

long as it remains a little bit mysterious.

Robotics and AI

Robotics and AI complement each other. Scientists have dreamed for more than a century about

building smart androids: robots that look like people, act like people, and can even reason like peo-

ple. Androids exist, but they aren’t very smart. Powerful computers exist, but they lack mobility.

If a machine has the ability to move around under its own power, to lift things, and to move

things, it seems reasonable that it should do so with some degree of intelligence if it is to accomplish

anything worthwhile. Conversely, if a computer is to manipulate anything, it must be able to cause

a machine to do physical work according to a precise program.

Expert Systems

The term expert systems refers to a method of reasoning in AI. Sometimes this scheme is called the

rule-based system. Expert systems are used in the control of smart robots.

The heart of an expert system is a set of facts and rules. In the case of a robotic system, the facts

consist of data about the robot’s work environment, such as a factory, an office, or a kitchen. The

rules are statements of the logical form “If X, then Y,” similar to many of the statements in high-

level programming languages. An inference engine decides which logical rules should be applied in

various situations and instructs the robot to carry out certain tasks. But the operation of the system

can only be as sophisticated as the data supplied by human programmers.

Expert systems can be used in computers to help people do research, make decisions, and

make forecasts. A good example is a program that assists a physician in making a diagnosis. The

The Mind of the Machine 605

computer asks questions and arrives at a conclusion based on the answers given by the patient and

doctor.

One of the biggest advantages of expert systems is the fact that reprogramming is easy. As the

environment changes, the robot can be taught new rules, and supplied with new facts.

How Smart a Machine?

Experts in the field of AI have been disappointed in the past few decades. Computers have been de-

signed that can handle tasks no human could ever contend with, such as navigating a space probe.

Machines have been built that can play board games well enough to compete with human masters.

Modern machines can understand, as well as synthesize, much of any spoken language. But these

abilities, by themselves, don’t count for much in the dreams of scientists who hope to create artifi-

cial life.

The human mind is incredibly complicated. A circuit that would have occupied, and used all

the electricity in, a whole city in 1940 can now be housed in a box the size of a vitamin pill and run

by a battery. Imagine this degree of miniaturization happening again, then again, and then again.

Would that begin to approach the level of sophistication in your body’s nervous system?

Is the human brain nothing more than an amazingly complicated digital switching network? Or

is there something more to the human mind? No electronic device yet constructed has come any-

where near human intelligence in every respect. Some experts think that a machine will someday be

built that is smarter than its creators. Others insist that the very idea is ridiculous.

It is tempting to extrapolate: If technological trends of the past few decades continue indefi-

nitely, will the only limit on machine intelligence be defined by human imagination?

Quiz

Refer to the text in this chapter if necessary. A good score is 18 correct. Answers are in the back of

the book.

1. An android takes the form of

(a) an insect.

(b) the human body.

(d) a stereo vision system.

2. According to Asimov’s three laws, under what circumstances is it all right for a robot to injure

a human being?

(a) Under no circumstances

(b) When the human being specifically requests it

(d) In case the robot controller is infected with a computer virus

3. An RF field strength meter can be used to

(a) test the performance of a binaural hearing system.

(b) detect the presence of ionized air.

606 Monitoring, Robotics, and Artificial Intelligence

(d) detect the presence of a wireless bugging system.

4. The extent to which a machine vision system can differentiate between two objects that are

close together is called the

(a) optical magnification.

(b) optical sensitivity.

(d) optical resolution.

5. A robot car or truck can best keep itself traveling down a specific lane of traffic by means of

(a) stereoscopic machine hearing.

(b) epipolar navigation.

(d) proximity sensing.

6. A rule-based system is also known as

(a) a logic gate.

(b) an expert system.

(d) a telechir.

7. Suppose you are using a battery-powered, multichannel baby monitor, and you hear one end

of a two-way radio conversation on the receiver. You check the baby’s room, and it is quiet. How

might this problem be resolved?

(a) Put the receiver in a different location.

(b) Switch the monitor to a different channel.

(d) Use ac power instead of battery power.

8. In robotics, the term manipulator refers to

(a) a robot propulsion system.

(b) a robot arm, and the device at its end (such as a gripper).

(d) a computer that guides a fleet of mobile robots.

9. A device with an IR sensor can be used to detect the presence of

(a) slow-moving objects.

(b) RF signals.

(d) warm or hot objects.

Quiz 607

10. Proximity sensing is most closely akin to

(a) direction measurement.

(b) edge detection.

(d) binaural machine hearing.

11. A telechir is always used in conjunction with a specialized system of

(a) track drive.

(b) wheel drive.

(d) ionization potential measurement.

12. A limit to the distance over which telepresence is practical is imposed by

(a) the speed of EM wave propagation.

(b) the image resolution of the vision system.

(d) all of the above.

13. The ionization potential of the air can be determined in order to

(a) detect smoke.

(b) plot distances and directions.

(d) detect boundaries.

14. Two-dimensional range plotting

(a) takes place along a single geometric line.

(b) takes place in a single geometric plane.

(d) requires an ultrasonic sonar system.

15. Spherical coordinates can uniquely define the position of a point in up to

(a) one dimension.

(b) two dimensions.

(d) four dimensions.

16. The total number of ways in which a robot arm can move is known as

(a) functional orientation.

(b) degrees of freedom.

(d) coordinate geometry.

608 Monitoring, Robotics, and Artificial Intelligence

17. The region in space throughout which a robot arm can accomplish tasks is called its

(a) coordinate geometry.

(b) reference axis.

(d) work envelope.

18. A robot arm that moves along three independent axes, each of which is straight and

perpendicular to the other two, employs

(a) revolute geometry.

(b) spherical coordinate geometry.

(d) cylindrical coordinate geometry.

19. Fill in the blank to make the following sentence true: “A color vision system can use three

grayscale cameras, equipped with filters that pass

light.”

(a) red, yellow, and blue

(b) blue, red, and green

(d) orange, green, and violet

20. A robot typically determines the steepness of a slope by means of

(a) an epipolar navigation system.

(b) a clinometer.

(d) a proximity sensor.

Quiz 609

DO NOT REFER TO THE TEXT WHEN TAKING THIS TEST. A GOOD SCORE IS AT LEAST 37 CORRECT.

Answers are in the back of the book. It’s best to have a friend check your score the first time, so you

won’t memorize the answers if you want to take the test again.

1. Which of the following tasks can a displacement transducer perform?

(a) It can detect the peak amplitude of an ac signal and display it on a screen.

(b) It can convert acoustic energy into radio signals.

(d) It can convert an electrical signal into mechanical rotation through a defined angle.

(e) It can be used to measure the frequency of a complex wave.

2. Which of the following is not an advantage of an IC, compared to a circuit built with discrete

components (individual resistors, capacitors, inductors, diodes, and transistors)?

(a) Compactness

(b) Reliability

(d) Low power consumption

(e) Unlimited power handling capacity

3. Computer memory is typically measured in

(a) kilobits, megabits, and gigabits.

(b) kilobits per second, megabits per second, and gigabits per second.

(d) kilobytes per second, megabytes per second, and gigabytes per second.

(e) any of the above.

610

Test: Part 4