McGraw-Hill - The Robot Builder''''s Bonanza Part 5 pps

TABLE 10.1 PARTS LIST FOR BUGGYBOT Frame: 1 6-by-12-inch sheet of 1/16-inch thick aluminumMotor and Mount: 2 Tamiya high-power gearbox motors from kit; see text 2 3-inch-diameter “Lite F

hands Especially with metal, the bit can snag as it’s cutting and yank the piece out of yourhands If you can’t place the work in the vise, use a pair of Vise-Grips or other suitablelocking pliers.

FINISHING

Cutting and drilling often leaves rough edges, called flashing, in the metal These edges

must be filed down using a medium- or fine-pitch metal file, or else the pieces won’t fittogether properly Aluminum flash comes off quickly and easily; you need to work a littleharder when removing the flash in steel or zinc stock

Build the BuggybotThe Buggybot is a small robot built from a single 6-by-12-inch sheet of 1/16-inch thickaluminum, nuts and bolts, and a few other odds and ends You can use the Buggybot as thefoundation and running gear for a very sophisticated petlike robot As with the robots builtwith plastic and wood we discussed in the previous two chapters, the basic design of theall-metal Buggybot can be enhanced just about any way you see fit This chapter detailsthe construction of the framework, locomotion, and power systems for a wired remote con-trol robot Future chapters will focus on adding more sophisticated features, such as wire-less remote control, automatic navigation, and collision avoidance and detection Refer toTable 10.1 for a list of the parts needed to build the Buggybot

TABLE 10.1 PARTS LIST FOR BUGGYBOT

Frame:

1 6-by-12-inch sheet of 1/16-inch thick aluminumMotor and Mount:

2 Tamiya high-power gearbox motors (from kit); see text

2 3-inch-diameter “Lite Flight” foam wheels

2 5/56 nuts (should be included with the motors)

2 3/16-inch collars with setscrews

1 Two-cell “D” battery holderMisc 1-inch-by-6/32 stove bolts, nuts, flat washersSupport Caster:

1 1 1/2-inch swivel casterMisc 1/2-inch-by-6/32 stove bolts, nuts, tooth lock washers, flat washers (as

spacers)See parts list in Table 8.3 of Chapter 8 for motor control switch

Build the frame of the Buggybot from a single sheet of 1/16-inch thick aluminum sheet.This sheet, measuring 6 by 12 inches, is commonly found at hobby stores As this is astandard size, there’s no need to cut it Follow the drill-cutting template shown in Fig 10.1

After drilling, use a large shop vise or woodblock to bend the aluminum sheet as shown

in Fig 10.2 Accuracy is not all that important The angled bends are provided to give theBuggybot its unique appearance

BUILD THE BUGGYBOT 127

6" by 12"

aluminumsheet

5 1/2"

FIGURE 10.1 Drilling diagram for the Buggybot frame.

MOTORS AND MOTOR MOUNT

The prototype Buggybot uses two high-power gearbox motor kits from Tamiya, whichcome in kit form and are available at many hobby stores (as well as Internet sites, such

as TowerHobbies.com) These motors come with their own gearbox; choose the 1:64.8gear ratio An assembled motor is shown in Fig 10.3 Note that the output shaft of themotor can be made to protrude a variable distance from the body of the motor Securethe shaft (using the Allen setscrew that is included) so that only a small portion of theopposite end of the shaft sticks out of the gear box on the other side, as shown in Fig 10.3

You should secure the gearboxes and motors to the aluminum frame of the Buggybot asdepicted in Fig 10.4 Use 6/32 bolts, flat washers, and nuts Be sure that the motors arealigned as shown in the figure Note that the shaft of each motor protrudes from the side

of the Buggybot

Figure 10.5 illustrates how to attach the wheels to the shafts of the motors The wheelsused in the prototype were 3-inch-diameter foam “Lite Flight” tires, commonly avail-able at hobby stores Secure the wheels in place by first threading a 3/16-inch collar (available at hobby stores) over the shaft of the motor Tighten the collar in place using itsAllen setscrew Then cinch the wheel onto the shaft by tightening a 5/56 threaded nut tothe end of the motor shaft (the nut should be included with the gearbox motor kit) Be sure

to tighten down on the nut so the wheel won’t slip

SUPPORT CASTER

The Buggybot uses the two-wheel drive tripod arrangement You need a caster on the otherend of the frame to balance the robot and provide a steering swivel The 1 1/2-inch swivelcaster is not driven and doesn’t do the actual steering Driving and steering are taken care

of by the drive motors Refer to Fig 10.6 on p 131 Attach the caster using two 6/32 by1/2-inch bolts and nuts

Note that the mechanical style of the caster, and indeed the diameter of the caster wheel,

is dependent on the diameter of the drive wheels Larger drive wheels will require either a

different mounting or a larger caster Small drive wheels will likewise require you to adjustthe caster mounting and possibly use a smaller-diameter caster wheel.

BATTERY HOLDER

The motors require an appreciable amount of current, so the Buggybot really should bepowered by heavy-duty “C”- or “D”-size cells The prototype Buggybot used a two-cell

“D” battery holder The holder fits nicely toward the front end of the robot and acts as a

BUILD THE BUGGYBOT 129

Tire

Nut

Motor andgearbox

Coupler(with setscrew)

Output gear(with setscrew)

Motor shaft

FIGURE 10.3 Secure the output shaft of the motor so that almost all

of the shaft sticks out on one side of the motor.

Nut

Base1/2" x 6/32 Bolt

Motor gearbox

Mounting flange

FIGURE 10.4 The gearboxes and motors are attached to the frame

of the Buggybot using ordinary hardware.

good counterweight You can secure the battery holder to the robot using double-sided tape

or hook-and-loop (Velcro) fabric

WIRING DIAGRAM

The basic Buggybot uses a manual wired switch control The control is the same one used

in the plastic Minibot detailed in Chapter 8, “Building a Plastic Robot Platform.” Refer tothe wiring diagram in Fig 8.4 of that chapter for information on powering the Buggybot

To prevent the control wire from interfering with the robot’s operation, attach a piece ofheavy wire (the bottom rail of a coat hanger will do) to the caster plate and lead the wire up it Use nylon wire ties to secure the wire The completed Buggybot is shown inFig 10.7

Test RunYou’ll find that the Buggybot is an amazingly agile robot The distance it needs to turn isonly a little longer than its length, and it has plenty of power to spare There is room on therobot’s front and back to mount additional control circuitry You can also add control cir-cuits and other enhancements over the battery holder Just be sure that you can remove thecircuit(s) when it comes time to change or recharge the batteries

FIGURE 10.5 Attach the foam wheels (with plastic hubs) for the Buggybot onto

the shafts of the motors.

TEST RUN 131

Nut Tooth Lockwasher

Base

Caster 1/2" x 6/32 Bolt

FIGURE 10.6 Mounting the caster to the Buggybot.

FIGURE 10.7 The completed Buggybot.

From Here

To learn more about Read

Plastic robots Chapter 8, “Building a Plastic Robot Platform”Metal robots Chapter 9, “Building a Basic Wooden Platform”Using batteries Chapter 15, “All about Batteries and Robot

Power Supplies”

Selecting the right motor Chapter 17, “Choosing the Right Motor for the Job”Using a computer or microcontroller Chapter 28, “An Overview of Robot ‘Brains’”

Ready-made toys can be used as the basis for more complex homebrew hobby robots.The toy industry is robot crazy, and you can buy a basic motorized or unmotorizedrobot for parts, building on it and adding sophistication and features Snap or screw-together kits, such as the venerable Erector Set, let you use premachined parts for yourown creations And some kits, like LEGO and Robotix, are even designed to createfuturistic motorized robots and vehicles You can use the parts in the kits as is or can-nibalize them, modifying them in any way you see fit Because the parts already come

in the exact or approximate shape you need, the construction of your own robots isgreatly simplified

About the only disadvantage to using toys as the basis for more advanced robots is thatthe plastic and lightweight metal used in the kits and finished products are not suitable for

a homemade robot of any significant size or strength You are pretty much confined tobuilding small Minibot or Scooterbot-type robots from toy parts Even so, you can some-times apply toy parts to robot subsystems, such as a light-duty arm-gripper mechanisminstalled on a larger automaton

Let’s take a closer look at using toys in your robot designs in this chapter, and examineseveral simple, cost-effective designs using readily available toy construction kits

Erector SetErector Set, now sold by Meccano, has been around since the Dawn of Time—or so itseems The kits, once made entirely of metal but now commonly including many plas-tic pieces, come in various sizes and are generally designed to build a number of dif-ferent projects Many kits are engineered for a specific design with perhaps provisionsfor moderate variations I’ve found the general-purpose sets to be the best bets Amongthe useful components of the kits are prepunched metal girders, plastic and metalplates, tires, wheels, shafts, and plastic mounting panels You can use any as you see fit,assembling your robots with the hardware supplied with the kit or with 6/32 or 8/32nuts and bolts.

Several Erector Sets, such as those in the Action Troopers collection, come with wheels,construction beams, and other assorted parts that you can use to construct a robot base.Motors are typically not included in these kits, but you can readily supply your own.Because Erector Set packages regularly come and go, what follows is a general guide tobuilding a robot base You’ll need to adapt and reconfigure based on the Erector Set partsyou have on hand

The prepunched metal girders included in the typical Erector Set make excellent motormounts They are lightweight enough that they can be bent, using a vise, into a U-shapedmotor holder Bend the girder at the ends to create tabs for the bolts, or use the angle stockprovided in an Erector Set kit The basic platform is designed for four or more wheels, butthe wheel arrangement makes it difficult to steer the robot The design presented in Fig.11.1 uses only two wheels The platform is stabilized using a miniature swivel caster at oneend You’ll need to purchase the caster at the hardware store

Note that the shafts of the motors are not directly linked to the wheels The shaft of thewheels connect to the baseplate as originally designed in the kit The drive motors areequipped with rollers, which engage against the top of the wheels for traction You can use

a metal or rubber roller, but rubber is better The pinch roller from a discarded cassette tapeplayer is a good choice, as is a 3/8-inch beveled bibb washer, which can be found in theplumbing section of the hardware store You can easily mount a battery holder on the top

of the platform Position the battery holder in the center of the platform, toward the casterend This will help distribute the weight of the robot

The basic platform is now complete You can attach a dual-switch remote control, asdescribed in Chapter 8, “Building a Plastic Robot Platform,” or connect automatic controlcircuitry as detailed in Part 5 of this book, “Computers and Electronic Control.”

Do note that over the years the Erector Set brand has gone through many owners Partsfrom old Erector Sets are unlikely to fit well with new parts This includes but is not lim-ited to differences in the threads used for the nuts and bolts If you have a very old ErectorSet (such as those made and sold by Gilbert), you’re probably better off keeping them ascollector’s items rather than raiding them for robotic parts The very old Erector Sets of the1930s through 1950s fetch top dollar on the collector’s market (when the sets are in good,complete condition, of course)

Similarly, today’s Meccano sets are only passably compatible with the English-madeMeccano sets sold decades ago Hole spacing and sizes have varied over the years, and

“mixing and matching” is neither practical nor desirable

RobotixThe Robotix kits, originally manufactured by Milton-Bradley and now sold by LearningCurve, are specially designed to make snap-together walking and rolling robots Variouskits are available, and many of them include at least one motor (additional motors are avail-able separately) You control the motors using a central switch pad Pushing the switch for-ward turns the motor in one direction; pushing the switch back turns the motor in the otherdirection The output speed of the motors is about six rpm, which makes them a bit slowfor moving a robot across the room but perfect for arm-gripper designs.

ROBOTIX 135

Wheel

Base

Drive motor Motor clamp Rubber roller

Swivel Side view

Caster Drive wheels

A

B

FIGURE 11.1 Constructing the motorized base for a robot using Erector Set

(Meccano) parts a Attaching the motor and drive roller over the wheel; b Drive wheel-caster arrangement.

The structural components in the Robotix kits are molded from high-impact plastic Youcan connect pieces together to form just about anything One useful project is to build arobotic arm using several of the motors and structural components The arm can be used

by itself as a robotic trainer or attached to a larger robot It can lift a reasonable eightounces or so, and its pincher claw is strong enough to firmly grasp most small objects.While the Robotix kit allows you to snap the pieces apart when you’re experimenting,the design presented in this chapter is meant to be permanent Glue the pieces togetherusing plastic model cement or contact cement Cementing is optional, of course, andyou’re free to try other, less permanent methods to secure the parts together, such as smallnuts and bolts, screws, or Allen setscrews

When cemented, the pieces hold together much better, and the arm is considerablystronger Remember that, once cemented, the parts cannot be easily disassembled, so makesure that your design works properly before you commit to it When used as a stand-alonearm, you can plug the shoulder motor into the battery holder or base You don’t need tocement this joint

Refer to Fig 11.2 as you build the arm Temporarily attach a motor (we’ll call it “motor1”) to the Robotix battery holder-baseplate Position the motor so that the drive spindle pointsstraight up Attach a double plug to the drive spindle and the end connector of another motor,

“motor 2.” Position this motor so that the drive spindle is on one side Next, attach another double plug and an elbow to the drive spindle of motor 2 Attach the other end ofthe elbow connector to a beam arm

Connect a third motor, “motor 3,” to the large connector on the opposite end of thebeam arm Position this motor so the drive spindle is on the other end of the beam arm.Attach a double plug and an elbow between the drive spindle of motor 3 and the connec-tor opposite the drive spindle of the fourth motor, “motor 4.” The two claw levers directlyattach to the drive spindle of motor 4

Motorize the joints by plugging in the yellow power cables between the power switchbox and the motor connectors Try each joint, and note the various degrees of freedom.Experiment with picking up various objects with the claw Make changes now before dis-assembling the arm and cementing the pieces together

After the arm is assembled, route the wires around the components, making sure there issufficient slack to permit free movement Attach the wires to the arm using nylon wire ties

A Variety of Construction SetsToy stores are full of plastic put-together kits and ready-made robot toys that seem to begyou to use them in your own robot designs Here are some toys you may want to considerfor your next project

LEGO

LEGO has become the premier construction toy, for both children and adults The LEGOCompany, parent company of the LEGO brand, has expanded the line as educationalresources, making the ubiquitous LEGO “bricks” common in schools across the country

and around the world LEGO also makes the Mindstorms, a series of sophisticated puterized robots Chapters 12 through 14 detail several LEGO-based robot creations,including the Mindstorms, as well as describing how you can use LEGO parts to buildcustom robots.

com-CAPSULA

Capsula is a popular snap-together motorized parts kit that uses unusual tube and sphereshapes Capsula kits comes in different sizes and have one or more gear motors that can beattached to various components The kits contain unique parts that other put-together toysdon’t, such as a plastic chain and chain sprockets or gears Advanced kits come withremote control and computer circuits All the parts from these kits are interchangeable Thelinks of the chain snap apart, so you can make any length of chain that you want Combinethe links from many kits and you can make an impressive drive system for an experimen-tal lightweight robot

A VARIETY OF CONSTRUCTION SETS 137

FIGURE 11.2 The robot arm constructed with parts from a Robotix construction

kit.

and they offer a snap-together approach to making working electromagnetic, hydraulic,pneumatic, static, and robotic mechanisms.

All the Fischertechnik parts are interchangeable and attach to a common plastic plate You can extend the lengths of the baseplate to just about any size you want, and thebaseplate can serve as the foundation for your robot, as shown in Fig 11.3 You can usethe motors supplied with the kits or use your own motors with the parts provided Because

base-of the cost base-of the Fischertechnik kits, you may not want to cannibalize them for robot ponents But if you are interested in learning more about mechanical theory and design,the Fischertechnik kits, used as is, provide a thorough and programmed method for jump-ing in with both feet

com-INVENTA

U.K.-based Valiant Technologies offers the Inventa system, a reasonably priced constructionsystem aimed at the educational market Inventa is a good source for gears, tracks, wheels,axles, and many other mechanical parts The beams used for construction are semiflexibleand can be cut to size Angles and brackets allow the beams to be connected in a variety ofways It is not uncommon—and in fact Valiant encourages it—to find Inventa creationsintermixed with other building materials, including balsa wood, LEGO pieces, you name it.Inventa isn’t the kind of thing you’ll find at the neighborhood Toys-R-Us It’s available mailorder and through the Internet; see the Inventa Web site at www.valiant-technology.com

FIGURE 11.3 A sampling of Fischertechnik parts.

K’Nex uses unusual half-round plastic spokes and connector rods (see Fig 11.4) to buildeverything from bridges to Ferris wheels to robots You can build a robot with just K’Nexparts or use the parts in a larger, mixed-component robot For example, the base of a walk-ing robot may be made from a thin sheet of aluminum, but the legs might be constructedfrom various K’Nex pieces

A number of K’Nex kits are available, from simple starter sets to rather massive cial-purpose collections (many of which are designed to build robots, dinosaurs, or robot-dinosaurs) Several of the kits come with small gear motors so you can motorize your cre-ation The motors are also available separately

spe-ZOOB

Zoob (made by Primordial) is a truly unique form of construction toy A Zoob piece sists of stem with a ball or socket on either end You can create a wide variety of con-struction projects by linking the balls and sockets together The balls are dimpled so theyconnect securely within their sockets One practical application of Zoob is to create “arma-tures” for human- or animal-like robots The Zoob pieces work in a way similar to bone joints

con-A Vcon-ARIETY OF CONSTRUCTION SETS 139

FIGURE 11.4 K’Nex sets let you create physically large robots that weigh very

little The plastic pieces form very sturdy structures when properly connected.

Chaos sets are designed for structural construction projects: bridges, buildings, workingelevator lifts, and the like The basic Chaos set provides beams and connectors, along withchutes, pulleys, winches, and other construction pieces Add-on sets are available that con-tain parts to build elevators, vortex tubes, and additional beams and connectors

FASTECH

No longer in production, Fastech construction kits used to offer among the best ments of parts you could buy All the parts were plastic, and the kits came with a plastictemporary riveting system that you probably wouldn’t use in your designs The plasticparts were predrilled and came in a variety of shapes and styles The components can beused on their own to make a small, light-duty robot frame and body, or they can be used

assort-as parts in a larger robot Fassort-astech kits may not be manufactured (but who knows, theycould come back), but they can sometimes be found at garage sales, thrift stores, andonline auctions

OTHER CONSTRUCTION TOYS

There are many other construction toys that you may find handy Check the nearest stocked toy store or a toy retailer on the Internet for the following:

well-■ Expandagon Construction System (Hoberman)

■ Fiddlestix Gearworks (Toys-N-Things)

■ Gears! Gears! Gears! (Learning Resources)

■ PowerRings (Fun Source)

■ Zome System (Zome System)

■ Construx (no longer made, but sets may still be available for sale)Perhaps the most frequently imitated construction set has been the Meccano/Erector Setline Try finding these “imitators,” either in new, used, or thrift stores:

Tamiya is a manufacturer of a wide range of radio-controlled models They also sell asmall selection of gearboxes in kit form that you can use for your robot creations One of the most useful is a dual-gear motor, which consists of two small motors andindependent drive trains You can connect the long output shafts to wheels, legs, ortracks

They also sell a tracked tractor-shovel kit (see Fig 11.5) that you control via a switchpanel You can readily substitute the switch panel with computerized control circuitry(relays make it easy) that will provide for full forward and backward movement of the tanktreads as well as the up and down movement of the shovel

OWIKITS and MOVITS

The OWIKITS and MOVITS robots are precision-made miniature robots in kit form Avariety of models are available, including manual (switch) and microprocessor-based ver-sions The robots can be used as is, or they can be modified for use with your own elec-tronic systems For example, the OWIKIT Robot Arm Trainer (model OWI007) is nor-mally operated by pressing switches on a wired control pad With just a bit of work, youcan connect the wires from the arm to a computer interface (with relays, for example) andoperate the arm via software control

SPECIALTY TOYS FOR ROBOT HACKING 141

FIGURE 11.5 The Tamiya Bulldozer kit can be used as a lightweight robot

plat-form The kit comes with an interesting dual motor that operates the left and right treads.

Most of the OWIKITS and MOVITS robots come with preassembled circuit boards;you are expected to assemble the mechanical parts Some of the robots use extremely smallparts and require a keen eye and steady hand The kits are available in three skill levels:beginner, intermediate, and advanced If you’re just starting out, try one or two kits in the beginner level.

Once (properly) constructed, the OWIKITS and MOVITS robots last a long, long time

I have several models I built in the mid-1980s, and with just the occasional nut tighteninghere and a dab of grease there they have continued to operate flawlessly

FURBY

The Furby, from Tiger Electronics, is an animatronic creature that appears to have ing capabilities and even artificial intelligence Actually, the Furby has neither; it’s a clevercollection of motors, gears, switches, sensors, and an on-board computer, as shown in the

learn-“deconstructed Furby” shown in Fig 11.6 The Furby interacts with its master, as well asthe environment, and contains thousands of behavioral permutations

FIGURE 11.6 The Furby, from Tiger Electronics, is a

marvel of engineering finesse.