McGraw-Hill - The Robot Builder''''s Bonanza Part 2 pptx

Sensory Devices Imagine a world without sight, sound, touch, smell, or taste. Without these senses, we’d be nothing more than an inanimate machine, like the family car, the living room television, or that guy who hosts the Channel 5 late-night movie. Our senses are an integral part of our lives—if not life itself. It makes good sense (pardon the pun) to build at least one of these senses into your robot designs. The more senses a robot has, the more it can interact with its environment. That capacity for interaction will make the robot better able to go about its business on its own, which makes possible more sophisticated tasks. Sensitivity to sound is a sensory sys- tem commonly given to robots. The reason: Sound is easy to detect, and unless you’re try- ing to listen for a specific kind of sound, circuits for sound detection are simple and straightforward. Sensitivity to light is also common, but the kind of light is usually restricted to a slen- der band of infrared for the purpose of sensing the heat of a fire or navigating through a room using an invisible infrared light beam. SENSORY DEVICES 21 FIGURE 2.4. A robotic arm from General Electric is designed for precision manufacturing. Photo courtesy General Electric. Ch02_McComb 8/29/00 8:39 AM Page 21 Robot eyesight is a completely different matter. The visual scene surrounding the robot must be electronically rendered into a form the circuits on the robot can accept, and the machine must be programmed to understand and act on the shapes it sees. A great deal of experimental work is underway to allow robots to distinguish objects, but true robot vision is limited to well-funded research teams. Chapter 37, “Robotic Eyes,” provides the basics on how to give crude sight to a robot. In robotics, the sense of touch is most often confined to collision switches mounted around the periphery of the machine. On more sophisticated robots, pressure sensors may be attached to the tips of fingers in the robot’s hand. The more the fingers of the hand close in around the object, the greater the pressure detected by the sensors. This pressure infor- mation is relayed to the robot’s brain, which then decides if the correct amount of pressure is being exerted. There are a number of commercial products available that register pressure of one kind or another, but most are expensive. Simple pressure sensors can be constructed cheaply and quickly, however, and though they aren’t as accurate as commercially manufactured pressure sensors, they are more than adequate for hobby robotics. See Chapter 35, “Adding the Sense of Touch,” and Chapter 36, “Collision Avoidance and Detection,” for details. The senses of smell and taste aren’t generally implemented in robot systems, though some security robots designed for industrial use are outfitted with a gas sensor that, in effect, smells the presence of dangerous toxic gas. Output Devices Output devices are components that relay information from the robot to the outside world. A common output device in computer-controlled robots (discussed in the next section) is the video screen or (liquid crystal display) panel. As with a personal computer, the robot communicates with its master by flashing messages on a screen or panel. A more common output device for hobby robots is the ordinary light-emitting diode, or a seven-segment numeric display. Another popular robotic output device is the speech synthesizer. In the 1968 movie 2001: A Space Odyssey, Hal the computer talks to its shipmates in a soothing but electronic voice. The idea of a talking computer was a rather novel concept at the time of the movie, but today voice synthesis is commonplace. Many hobbyists build robots that contain sound and music generators. These generators are commonly used as warning signals, but by far the most frequent application of speech, music, and sound is for entertainment purposes. Somehow, a robot that wakes you up to an electronic rendition of Bach seems a little more human. Projects in robot sound-making circuits are provided in Chapter 40, “Sound Output and Input.” Smart versus “Dumb” Robots There are smart robots and there are dumb robots, but the difference really has nothing to do with intelligence. Even taking into consideration the science of artificial intelligence, 22 ANATOMY OF A ROBOT Ch02_McComb 8/29/00 8:39 AM Page 22 all self-contained autonomous robots are fairly unintelligent, no matter how sophisticated the electronic brain that controls it. Intelligence is not a measurement of computing capac- ity but the ability to reason, to figure out how to do something by examining all the vari- ables and choosing the best course of action, perhaps even coming up with a course that is entirely new. In this book, the difference between dumb and smart is defined as the ability to take two or more pieces of data and decide on a preprogrammed course of action. Usually, a smart robot is one that is controlled by a computer. However, some amazingly sophisticated actions can be built into an automaton that contains no computer; instead it relies on sim- ple electronics to provide the robot with some known “behavior” (such is the concept of BEAM robotics). A dumb robot is one that blindly goes about its task, never taking the time to analyze its actions and what impact they may have. Using a computer as the brains of a robot will provide you with a great deal of operat- ing flexibility. Unlike a control circuit, which is wired according to a schematic plan and performs a specified task, a computer can be electronically “rewired” using software instructions—that is, programs. To be effective, the electronics must be connected to all the control and feedback components of the robot. This includes the drive motors, the motors that control the arm, the speech synthesizer, the pressure sensors, and so forth. Connecting a computer to a robot is a demanding task that requires many hours of careful work. This book presents several computer-based control projects in later chapters. Note that this book does not tell you how to construct a computer. Rather than tell you how to build a specially designed computer for your robot, the projects in this book use read- ily available and inexpensive microcontrollers and single-board computers as well as ready- built personal computers based on the ubiquitous IBM PC design. You can permanently integrate some computers, particularly the portable variety, with your larger robot projects. The Concept of Robot “Work” The term robota, from which the common word robot is derived, was first coined by Czech novelist and playwright Karel Capek in his 1917 short story “Opilec.” The word robota was used by Capek again in his now-classic play R.U.R. (which stands for “Rossum’s Universal Robots”), first produced on stage in 1921. R.U.R. is one of many plays written by Capek that have a utopian theme. And like most fictional utopias, the basic premise of the play’s “perfect society” is fatally flawed. In R.U.R. the robots are created by humans to take over all labor, including working on farms and in factories. When a scientist attempts to endow the robot workforce with human emotions—including pain—the automatons conspire against their flesh-and-bone masters and kill them. In Czech, the term robota means “compulsory worker,” a kind of machine slave. In many other Baltic languages the term simply means “work.” It is the work aspect of robot- ics that is often forgotten, but it defines a “robot” more than anything else. A robot that is not meant to do something—for example, one that simply patrols the living room looking for signs of warm-blooded creatures—is not a robot at all but merely a complicated toy. That said, designing and building lightweight “demonstrator” robots provides a per- fectly valid way to learn about the robot-building craft. Still, it should not be the end-all THE CONCEPT OF ROBOT “WORK” 23 Ch02_McComb 8/29/00 8:39 AM Page 23 of your robot studies. Never lose sight of the fact that a robot is meant to do something— the more, the better! Once you perfect the little tabletop robot you’ve been working on the past several months, think of ways to apply your improved robot skills to building a more substantial robot that actually performs some job. The job does not need to be labor sav- ing. We’d all like to have a robot maid like Rosie the Robot on the Jetsons cartoon series, but, realistically, it’s a pretty sophisticated robot that knows the difference between a clean and dirty pair of socks left on the floor. From Here To learn more about… Read Kinds of batteries for robots Chapter 15, “All about Batteries and Robot Power Supplies” Building mobile robots Part 2, “Robot Construction” Building a robot with legs Chapter 22, “Build a Heavy-duty, Six-legged Walking Robot” Chapter 23, “Advanced Locomotion Systems” More on robot arms Chaps. 24 -26 Robotic sensors Part 4, “Practical Robotic Projects” 24 ANATOMY OF A ROBOT Ch02_McComb 8/29/00 8:39 AM Page 24 Take a long look at the tools in your garage or workshop. You probably already have all the implements you will need to build your own robots. Unless your robot designs require a great deal of precision (and most hobby robots don’t), a common assortment of hand tools is all that’s really required to construct robot bodies, arms, drive systems, and more. Most of the hardware, parts, and supplies you need are also things you probably already have, left over from old projects around the house. You can readily purchase the pieces you don’t have at a hardware store, a few specialty stores around town, or through the mail. This chapter discusses the basic tools and supplies needed for hobby robot building and how you might use them. You should consider this chapter only as a guide; suggestions for tools and supplies are just that—suggestions. By no means should you feel that you must own each tool or have on hand all the parts and supplies mentioned in this chapter. Once again, the concept behind this book is to provide you with the know-how to build robots from discrete modules. In keeping with that open-ended design, you are free to exchange parts in the modules as you see fit. Some supplies and parts may not be readily available to you, so it’s up to you to consider alternatives and how to work them into your design. Ultimately, it will be your task to take a trip to the hardware store, collect the items you need, and hammer out a unique creation that’s all your own. 3 TOOLS AND SUPPLIES 25 Ch03_McComb 8/29/00 8:38 AM Page 25 Copyright 2001 The McGraw-Hill Companies, Inc. Click Here for Terms of Use. Construction Tools Construction tools are the things you use to fashion the frame and other mechanical parts of the robot. These include a hammer, a screwdriver, and a saw. We will look at the tools needed to assemble the electronics later in this chapter. BASIC TOOLS No robot workshop is complete without the following: ■ Claw hammer. These can be used for just about any purpose you can think of. ■ Rubber mallet. For gently bashing together pieces that resist being joined nothing beats a rubber mallet; it is also useful for forming sheet metal. ■ Screwdriver assortment. Have several sizes of flat-head and Philips-head screwdrivers. It’s also handy to have a few long-blade screwdrivers, as well as a ratchet driver. Get a screwdriver magnetizer/demagnetizer; it lets you magnetize the blade so it attracts and holds screws for easier assembly. ■ Hacksaw. To cut anything, the hacksaw is the staple of the robot builder. Buy an assort- ment of blades. Coarse-tooth blades are good for wood and PVC pipe plastic; fine-tooth blades are good for copper, aluminum, and light-gauge steel. ■ Miter box. To cut straight lines, buy a good miter box and attach it to your work table (avoid wood miter boxes; they don’t last). You’ll also use the box to cut stock at near- perfect 45° angles, which is helpful when building robot frames. ■ Wrenches, all types. Adjustable wrenches are helpful additions to the shop but careless use can strip nuts. The same goes for long-nosed pliers, which are useful for getting at hard-to-reach places. One or two pairs of Vise-Grips will help you hold pieces for cut- ting and sanding. A set of nut drivers will make it easy to attach nuts to bolts. ■ Measuring tape. A six- or eight-foot steel measuring tape is a good length to choose. Also get a cloth tape at a fabric store so you can measure things like chain and cable lengths. ■ Square. You’ll need one to make sure that pieces you cut and assemble from wood, plas- tic, and metal are square. ■ File assortment. Files will enable you to smooth the rough edges of cut wood, metal, and plastic (particularly important when you are working with metal because the sharp, unfinished edges can cut you). ■ Drill motor. Get one that has a variable speed control (reversing is nice but not absolute- ly necessary). If the drill you have isn’t variable speed, buy a variable speed control for it. You need to slow the drill when working with metal and plastic. A fast drill motor is good for wood only. The size of the chuck is not important since most of the drill bits you’ll be using will fit a standard 1/4-inch chuck. ■ Drill bit assortment. Use good sharp ones only. If yours are dull, have them sharpened (or do it yourself with a drill bit sharpening device), or buy a new set. ■ Vise. A vise is essential for holding parts while you drill, nail, and otherwise torment them. An extra large vise isn’t required, but you should get one that’s big enough to han- dle the size of the pieces you’ll be working with. A rule of thumb: A vice that can’t close around a two-inch block of metal or wood is too small. 26 TOOLS AND SUPPLIES Ch03_McComb 8/29/00 8:38 AM Page 26 ■ Safety goggles. Wear them when hammering, cutting, and drilling as well as any other time when flying debris could get in your eyes. Be sure you use the goggles. A shred of aluminum sprayed from a drill bit while drilling a hole can rip through your eye, per- manently blinding you. No robot project is worth that. If you plan to build your robots from wood, you may want to consider adding rasps, wood files, coping saws, and other woodworking tools to your toolbox. Working with plas- tic requires a few extra tools as well, including a burnishing wheel to smooth the edges of the cut plastic (the flame from a cigarette lighter also works but is harder to control), a strip-heater for bending, and special plastic drill bits. These bits have a modified tip that isn’t as likely to rip through the plastic material. Small plastic parts can be cut and scored using a sharp razor knife or razor saw, both of which are available at hobby stores. OPTIONAL TOOLS There are a number of other tools you can use to make your time in the robot shop more productive and less time consuming. A drill press helps you drill better holes because you have more control over the angle and depth of each hole. Be sure to use a drill press vise to hold the pieces. Never use your hands! A table saw or circular saw makes it easier to cut through large pieces of wood and plastic. To ensure a straight cut, use a guide fence or fashion one out of wood and clamps. Be sure to use a fine-tooth saw blade if you are cut- ting through plastic. Using a saw designed for general woodcutting will cause the plastic to shatter. A motorized hobby tool, such as the model shown in Fig. 3.1, is much like a handheld router. The bit spins very fast (25,000 rpm and up), and you can attach a variety of wood, plastic, and metal working bits to it. The better hobby tools, such as those made by Dremel and Weller, have adjustable speed controls. Use the right bit for the job. For example, don’t use a wood rasp bit with metal or plastic because the flutes of the rasp will too easily fill with metal and plastic debris. A RotoZip tool (that’s its trade name) is a larger, more powerful version of a hobby tool. It spins at 30,000 rpm and uses a special cutting bit—it looks like a drill bit, but it works like a saw. The RotoZip is commonly used by drywall installers, but it can be used to cut through most any material you’d use for a robot (exception: heavy-gauge steel). Hot-melt glue guns are available at most hardware and hobby stores and come in a vari- ety of sizes. The gun heats up glue from a stick; press the trigger and the glue oozes out the tip. The benefit of hot-melt glue is that it sets very fast—usually under a minute. You can buy glue sticks for normal- or low-temperature guns. I prefer the normal-temperature sticks and guns as the glue seems to hold better. Exercise caution when using a hot-melt glue gun: the glue is hot, after all! You’ll know what I’m talking about when a glob of glue falls on your leg. Use a gun with an appropriate stand; this keeps the melting glue near the tip and helps protect you from wayward streams of hot glue. A nibbling tool is a fairly inexpensive accessory (under $20) that lets you “nibble” small chunks from metal and plastic pieces. The maximum thickness depends on the bite of the tool, but it’s generally about 1/16 inch. Use the tool to cut channels and enlarge holes. A tap and die set lets you thread holes and shafts to accept standard-sized nuts and bolts. Buy a good set. A cheap assortment is more trouble than it’s worth. CONSTRUCTION TOOLS 27 Ch03_McComb 8/29/00 8:38 AM Page 27 A thread size gauge, made of stainless steel, may be expensive, but it helps you deter- mine the size of any standard SAE or metric bolt. It’s a great accessory for tapping and dieing. Most gauges can be used when you are chopping threads off bolts with a hacksaw. They will provide a cleaner cut. A brazing tool or small welder lets you spot-weld two metal pieces together. These tools are designed for small pieces only. They don’t provide enough heat to adequately weld pieces larger than a few inches in size. Be sure that extra fuel and oxygen cylinders or pellets are readily available for the brazer or welder you buy. There’s nothing worse than spending $30 to $40 for a home welding set, only to discover that supplies are not available for it. Be sure to read the instructions that accompany the welder and observe all precautions. Electronic Tools Constructing electronic circuit boards or wiring the power system of your robot requires only a few standard tools. A soldering iron leads the list. For maximum flexibility, invest in a modular soldering pencil, the kind that lets you change the heating element. For rou- tine electronic work, you should get a 25- to 30-watt heating element. Anything higher may damage electronic components. You can use a 40- or 50-watt element for wiring switches, relays, and power transistors. Stay away from “instant-on” soldering irons. For any appli- cation other than soldering large-gauge wires they put out far too much heat. 28 TOOLS AND SUPPLIES FIGURE 3.1 A motorized hobby tool is ideal for drilling, sanding, and shaping small parts. Ch03_McComb 8/29/00 8:38 AM Page 28 Supplement your soldering iron with these accessories: ■ Soldering stand. This is useful for keeping the soldering pencil in a safe, upright posi- tion. ■ Soldering tip assortment. Get one or two small tips for intricate printed circuit board work and a few larger sizes for routine soldering chores. ■ Solder. Don’t buy just any kind of solder; get the resin or flux core type. Acid core and silver solder should never be used on electronic components. ■ Sponge. Sponges are useful for cleaning the soldering tip as you use it. Keep the sponge damp, and wipe the tip clean every few joints. ■ Heat sink. Attach the heat sink to sensitive electronic components during soldering. It draws the excess heat away from the component, so it isn’t damaged. (See Chapter 6.) ■ Desoldering vacuum tool. This is useful for soaking up molten solder. Use it to get rid of excess solder, remove components, or redo a wiring job. ■ Dental picks. These are ideal for scraping, cutting, forming, and gouging into the work. ■ Resin cleaner. Apply the cleaner after soldering is complete to remove excess resin. ■ Solder vise. This vise serves as a “third hand,” holding together pieces to be soldered so you are free to work the iron and feed the solder. Read Chapter 6, “Electronic Construction Techniques,” for more information on soldering. Volt-Ohm Meter A volt-ohm meter, or multitester, is used to test voltage levels and the resistance of circuits. This moderately priced tool is the basic prerequisite for working with electronic circuits of any kind. If you don’t already own a volt-ohm meter you should seriously consider buying one. The cost is small considering the usefulness of the device. There are many volt-ohm meters on the market today. For robotics work, you don’t want a cheap model, but you don’t need an expensive one. A meter of intermediate quality is sufficient and does the job admirably at a price of between $30 and $75 (it tends to be on the low side of this range). Meters are available at Radio Shack and most electronics out- lets. Shop around and compare features and prices. DIGITAL OR ANALOG There are two general types of volt-ohm meters available today: digital and analog. The difference is not that one meter is used on digital circuits and the other on analog circuits. Rather, digital meters employ a numeric display not unlike a digital clock or watch. Analog meters use the older-fashioned—but still useful—mechanical movement with a needle that points to a set of graduated scales. Digital meters used to cost a great deal more than the analog variety, but the price difference has evened out recently. Digital meters, such as the one shown in Fig. 3.2, are fast becoming the standard. In fact, it’s hard to find a decent analog meter these days. VOLT-OHM METER 29 Ch03_McComb 8/29/00 8:38 AM Page 29 AUTOMATIC RANGING Some volt-ohm meters, analog or digital, require you to select the range before it can make an accurate measurement. For example, if you are measuring the voltage of a 9-volt tran- sistor battery, you set the range to the setting closest to, but above, 9 volts (with most meters it is the 20- or 50-volt range). Auto-ranging meters don’t require you to do this, so they are inherently easier to use. When you want to measure voltage, you set the meter to volts (either AC or DC) and take the measurement. The meter displays the results in the readout panel. ACCURACY Little of the work you’ll do with robot circuits will require a volt-ohm meter that’s superac- curate. A meter with average accuracy is more than enough. The accuracy of a meter is the minimum amount of error that can occur when taking a specific measurement. For example, the meter may be accurate to 2000 volts, plus or minus 0.8 percent. A 0.8 percent error at the kinds of voltages used in robots—typically, 5 to 12 volts DC—is only 0.096 volts. Digital meters have another kind of accuracy. The number of digits in the display deter- mines the maximum resolution of the measurements. Most digital meters have three and a half digits, so they can display a value as small as .001 (the half digit is a “1” on the left side of the display). Anything less than that is not accurately represented; then again, there’s little cause for accuracy higher than this. 30 TOOLS AND SUPPLIES FIGURE 3.2 A volt-ohm meter (or multitester) checks resistance, voltage, and current. This model is digital and has a 3 1/2-digit liquid crystal display (LCD) readout. Ch03_McComb 8/29/00 8:38 AM Page 30 [...]... (6/ 32, 8/ 32, and 10 /24 , respectively) are good for all-around construction Get a variety of bolts in 1/ 2- , 3/ 4-, 1-, 1 1/ 4-, Ch03_McComb 8 /29 /00 8:38 AM Page 39 EXTRUDED ALUMINUM 39 and 1 1 / 2- inch lengths You may also want to get some 2- and 3-inch-long bolts for special applications Motor shafts and other heavy-duty applications require 1/4-inch 20 or 5/16-inch hardware Pan-head stove bolts are the. .. transistors are the 2N 222 2 and the 2N3904 (some transistors are marked with an “MPS” prefix instead of the “2N” prefix; nevertheless, they are the same) Both kinds are available in bulk packages of 10 for about $1 Common PNP signal transistors are the 2N3906 and the 2N2907 (See Chapter 5 for the difference between NPN and PNP.) If the circuit you’re building specifies a transistor other than the generic... counterparts are the TIP 32 and TIP 42 These transistors come in the TO -2 2 0 style package (see Fig 3.6) A common larger-capacity NPN transistor that can switch 10 amps or more is the 2N3055 It comes in the TO-3 style package and is available everywhere It costs between 50 cents and $2, depending on the source DIODES Common diodes are the 1N914, for light-duty signal-switching applications, and the 1N4000... assortment of the small PC-mount pots (about 80 cents each retail) in the 1-megohm and 2. 5K-, 5K-, 10K-, 50K-, 100K-, 500K-, and 25 0K-ohm values You’ll find that 500K-ohm and 1-megohm pots are often used in op amp circuits, so buy a few extra of these Ch03_McComb 8 /29 /00 8:38 AM Page 41 ELECTRONIC SUPPLIES AND COMPONENTS 41 CAPACITORS Like resistors, you’ll find yourself returning to the same standard... configurations The standard length is usually 12 feet, but if you need less most hardware stores will cut to order (you save when you buy it in full lengths) The stock is available in plain (dull silver) anodized aluminum and gold anodized aluminum Get the plain stuff: it’s 10 to 25 percent cheaper Two particularly handy stocks are 41/64-by-1 / 2- by-1/16-inch channel and 57/64-by9/16-by-1/16-inch channel I use these... beside the unit under test, making sure it is close enough so the leads reach the circuit Plug in the leads, and test the meter operation by first selecting the resistance function setting (use the smallest scale if the meter is not auto-ranging) Touch the leads together: the meter should read 0 ohms If the meter Ch03_McComb 8 /29 /00 8:38 AM Page 32 32 TOOLS AND SUPPLIES does not respond, check the leads... square-shaped wrapping post Give the tool five to ten twirls, and the connection is complete The edges of the post keep the wire anchored in place To remove the wire, you use the other end of the tool and undo the wrapping Several different wire-wrapping tools are available Some are motorized, and some automatically strip the wire for you, which frees you of this task and of the need to purchase the. .. apparatus Part II, Robot Construction Ch04_McComb 8 /23 /00 3:33 PM Page 45 4 BUYING PARTS Building a robot from scratch can be hard or easy It’s up to you Personally, I go for the easy route; life is too demanding as it is From experience, I’ve found that the best way to simplify the construction of a robot is to use standard, off -the- shelf parts, things you can get at the neighborhood hardware, auto parts,... sure to ask the store personnel if they have any nonworking items they will sell you at a reasonable cost Here is just a short list of the electronic and mechanical items you’ll want to be on the lookout for and the primary robot- building components they have inside: I VCRs are perhaps the best single-source for parts, and they are in plentiful supply (hun- I I I I I dreds of millions of them have been... basic, no-nonsense model is enough, but don’t settle for the cheap, single-trace units A dual-trace (two-channel) scope with a 2 0- to 25 -MHz maximum input frequency should do the job nicely The two channels let you monitor two lines at once, so you can easily compare the input and output signals at the same time You do not need a scope with storage or delayed sweep, although if your model has these features . Get the plain stuff: it’s 10 to 25 percent cheaper. Two particularly handy stocks are 41/64-by-1 / 2- by-1/16-inch channel and 57/64-by- 9/16-by-1/16-inch channel. I use these extensively to make the. assortment of the small PC-mount pots (about 80 cents each retail) in the 1-megohm and 2. 5K-, 5K-, 10K-, 50K-, 100K-, 500K-, and 25 0K-ohm values. You’ll find that 500K-ohm and 1-megohm pots are. provides a per- fectly valid way to learn about the robot- building craft. Still, it should not be the end-all THE CONCEPT OF ROBOT “WORK” 23 Ch 02_ McComb 8 /29 /00 8:39 AM Page 23 of your robot studies.