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Stiquito: Advanced Experiments with a Simple and Inexpensive Robot / Edition 1

Stiquito: Advanced Experiments with a Simple and Inexpensive Robot / Edition 1

by James M. Conrad, Jonathan W. Mills, IEEE


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Stiquito: Advanced Experiments with a Simple and Inexpensive Robot / Edition 1

This revolutionary new book describes how to build an inexpensive, small-legged robot, and includes the robot kit. The book provides information on the design and control of legged robots and a curriculum for education that presents experiments and projects that illustrates what they teach. The experiments lead the reader on a tour of the current state of research in robotics. Stiquito has also been used to teach in primary, secondary, and high school curricula. The robot is intended for use as a research and educational platform to study computational sensors, subsumption architectures, neural gait control, behavior of social insects, and machine vision. The robot may be powered and controlled through a tether or autonomously with and on-board power supply and electronics.

The book begins with an introduction that describes the birth of Stiquito. The chapters that follow describe the building process, its modifications, and its increased load capacity. Other chapters examine designs for simple controllers to enhance the functionality of the robot and to give the robot intelligence and SCORPIO hardware designs for performing independent, intelligent operations. The text also illustrates Stiquito's uses in education by presenting lab exercises, describing the use of nitinol in classroom experiments, and providing a robotics curriculum for undergraduates. It examines further research on the role of logic in a mobile robot's sensors, control, and locomotion; Stiquito's platform for AI; and simulation of a robot guided by vision. The book concludes with a discussion of the future for nitinol-propelled walking robots.

Product Details

ISBN-13: 9780818674082
Publisher: Wiley
Publication date: 12/28/1997
Series: Systems Series , #6
Edition description: New Edition
Pages: 328
Product dimensions: 6.99(w) x 10.12(h) x 0.71(d)

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Advanced Experiments with a Simple and Inexpensive Robot, Robot Kit Included
By James M. Conrad Jonathan W. Mills

John Wiley & Sons

ISBN: 0-8186-7408-3

Chapter One

An Introduction to Stiquito, the Book, and the Kit

James M. Conrad


Welcome to the wonderful world of robotics. This book will give you a unique opportunity, one that has not been offered before, to learn about this field. It may also be the first to describe a robot and include the robot with the book, all for under $50. It will provide you with the skills and supplies needed to build a small robot, and will also give you instructions on how to build electronic controls for your robot.

The star of this book is Stiquito, a small, inexpensive hexapod (six-legged) robot. Stiquito has been used since 1992 by universities, high schools, and hobbyists. Stiquito is unique not only because it is inexpensive but also because its applications are limitless.

This introductory chapter will present an overview of robotics, the origins of Stiquito, a description of the Stiquito kit, an overview of the book, and suggestions on how to proceed with the book and building the kit.


This warning will be given frequently, but it is one that all potential builders must heed. Building the robot in this kit requires certain skills to produce a working robot. These hobby building skills include the following:

Tying knots in thin metal wires

Cutting and sanding short lengths (4 millimeters) of aluminum tubing

Threading the wire through the tubing

Crimping the aluminum tubing with pliers

Stripping insulation from wire

Patiently following instructions that require 3 to 6 hours to complete

If you think you will have difficulty with these skills or with the process of learning these skills, you should consider returning this book before opening the kit.


There are many different types of robots. The classic robots depicted in science fiction books, movies, and television shows are typically walking, talking, humanoid devices. The most useful and prevalent robot in use in the United States is the industrial arm robot used in manufacturing. You may have seen a car commercial that showed these robots welding and painting automobile bodies, for example. These robotic devices carry out repetitive and sometimes dangerous work precisely, each time. Unlike human workers, they do not need coffee breaks, health plans, or vacations (but they do need maintenance and the occasional sick day). An example of a robotic arm is the BPM Technology 3-D printer (see Figure 1.1).

Another type of robot used in industry is the autonomous wheeled vehicle. These robots are used for surveillance or delivering goods, mail, or other supplies. They follow a signal embedded in the floor, rely on preprogrammed moves, or guide themselves using cameras and programmed floor plans. An example of an autonomous wheeled robot, which is shown in Figure 1.2, is the SR 3 Cyberguard by Cybermotion. This device will travel through a warehouse or industrial building looking for signs of fire or intrusion.

Although interest in walking robots is increasing, their use in industry is limited. Walking robots have advantages over wheeled robots when traversing rocky or steep terrain. One robot recently walked in the crater of a volcano and gathered data in an area too hazardous for humans to venture. Researchers at the University of Illinois have built a large walking robot, Protobot (see Figure 1.3), based on the physiology of a cockroach. Although humor columnist Dave Barry dubbed this 2-foot creature "FrankenRoach" the robot's designers envision such devices scurrying around in hazardous environments, and even adapting to the loss of a limb.

Most walking robots do not take on a true biological means of propulsion, defined as the use of contracting and relaxing muscle fiber bundles. Propulsion for most walking robots is either pneumatic or motorized. Protobot approaches a biological construction because it walks by means of pneumatic cylinders emulating antagonistic muscle pairs.

True muscle-like propulsion did not exist until recently. There is a new material, nitinol, that emulates the operation of a muscle. Nitinol has the properties of contracting when heated and returning to its original size when cooled; some opposable force does need to stretch the nitinol back to its original size. This new material has spawned a plethora of new, small walking robots that could not have been built with motors. Although several of these robots were designed in the early 1990s, one of them has gained international prominence because of its low cost. This robot is called Stiquito.


In the early 1990s, Dr. Jonathan Mills was looking for a robotic platform on which to test his research on analog logic. Most platforms were prohibitively expensive, especially for a young assistant professor with limited research money. As necessity is the mother of invention, Mills set out to design his own inexpensive robot. He chose four basic materials for his designs.

1. For propulsion, he selected nitinol (specifically, Flexinol from Dynalloy, Inc.). This would provide a muscle-like reaction for his circuitry, and would closely mimic biological action. More detail on nitinol is provided throughout this book, and Appendix D contains detailed specifications for Flexinol.

2. For a counterforce to the nitinol, he selected music wire from K&S Engineering. The wire could serve as a force to stretch the nitinol back to its original length and provide support for the robot.

3. For the body of the robot, he selected 1/8-inch square plastic rod from Plastruct, Inc. The plastic is easy to cut, drill, and glue. It has relatively good heat-resistive properties.

4. For leg support, body support, and attachment of the nitinol to the plastic, he chose aluminum tubing from K&S Engineering.

Mills experimented with various designs, from a tiny, 2-inch-long, four-legged robot to a 4-inch-long robot with six floppy legs. Through this experimentation he found that the best robot movement was realized when the nitinol was parallel to the ground and the leg part touching the ground was perpendicular to the ground.

Stiquito's immediate predecessor was Sticky, a large hexapod robot. Sticky is 9 inches long, 5 inches wide, and 3 inches high. It contains nitinol wires inside aluminum tubes (the tubes are used primarily for support). Sticky can take 1.5-centimeter steps, and each leg has two degrees of freedom, which means that nitinol wire is used to pull the legs back as well as raise them.

Sticky was still not cost-effective, so Mills combined the concepts of earlier robots with the hexapod design of Sticky to make Stiquito (which means "little Sticky"). Stiquito (see Figure 1.4) has only one degree of freedom, but has a very low cost. Two years later, Mills designed a larger version of Stiquito, called Stiquito II, with two degrees of freedom.

At about the same time that Mills was experimenting with these legged robots, Roger Gilbertson of MondoTronics and Mark Tilden of Los Alamos Labs were also experimenting with nitinol. Gilbertson's and Tilden's robots are also described in this book.


The kit that is included with this book has enough materials to make one Stiquito robot, although there is enough extra in case you make a few errors while building the robot. The most important thing to remember when building this kit is that Stiquito is a hobby kit; it requires hobby building skills, such as cutting, sanding, and working with very small parts. For example, in one of the steps, you need to tie a knot in the nitinol wire. Nitinol is very much like thread, and it is somewhat difficult to tie a knot in it. But if you have time and patience (and after some practice), you will soon be able to tie knots like a professional.

The kit that is included with this book is a simplification of the original Stiquito described in Mills' technical report that was offered as a kit from Indiana University. In your kit, the plastic Stiquito body has been premolded, so you do not have to cut, glue, and drill plastic rod to make the body. Because of this simplification, more than 10 pages were removed from the original Stiquito technical report. This new body also allows room for builders to make more errors, and requires less precision when building the robot; therefore, your robot should be more robust than earlier models.

The intent of this kit is to allow the builder to create a platform on which to start experimentation for making the robot walk. The instructions provided in Chapter 2 show how you can create a Stiquito that walks in a tripod gait; that is, it allows three legs to move at one time. What you should do is examine your goals for building the Stiquito robot and plans for controlling how Stiquito walks. If your plans include allowing each of Stiquito's six legs to be controlled independently, then you should modify the assembly of your robot so that you attach control wires to each leg individually. If the design of your robot includes putting something on top-for example, a circuit that will allow it to walk on its own-you should consider how you want it to walk. If you want it simply to walk, a tripod gait may be sufficient. If you plan to put some complex circuitry like a microcontroller on top, you may want the flexibility of being able to control all six legs.

The Stiquito robot body was also designed so it could be assembled using screws instead of aluminum crimps. If you wish to use screws instead of crimps, use the sets of holes on the body that are offset slightly. The offset holes work such that you can wrap the nitinol in the same direction as the screw thread. The nitinol is then anchored at the same distance from the legs on each side of the body. I use one brass screw (5/16-inch #0-80), two brass washers (#0), and two brass nuts (#0-80) for each hole. The round screw head faces down, and one of the nuts on top tightens the screw. The other nut anchors the control wire to the screw. This assembly is illustrated in Figure 1.5; see the list of suppliers in Appendix C for sets of screws, washers, and nuts. The Stiquito body is also designed so that all 12 large holes can be used for two degrees of freedom for the legs (like Sticky and Stiquito II).

Chapter 2 has detailed assembly instructions, but here are some additional handy hints.

This is not Lego; it is not a snap-together, easy-to-build kit. This is a hobby kit, so it takes some model-building skills. Be patient. Allow six hours to build your first robot. Jonathan swears he can build a robot in an hour, but it takes me about three (while watching sports on TV). This could be a wonderful parent-child project (in fact, my young son wants to "build bugs with daddy"). Make sure to block out enough time to complete the kit.

Make sure you do not introduce any shorts across the control and ground wires on the robot, tether, or manual controller. Feel free to use electrical tape to insulate areas that might cause a short.

Make sure all electrical connections are clean and free of corrosion. Sand metal parts before tying, crimping, or attaching.

You may need to add some weight to Stiquito when using the manual controller. You can tape pennies to the bottom of the body or tape an AA battery on top. Make sure the weight does not short the control and ground wires.

In your building activities, I cannot stress enough the importance of following common safety practices.

Wear goggles when working with the kit, as many parts of the kit can act as sharp springs.

Use care when using a hobby knife; always cut away from you.

Use care when using a soldering iron; watch out for burns.

This kit is intended for adults and children over the age of 14.


This book is organized in three sections: walking robots (chapters 2-5), control of walking robots (chapters 6-11), and research ideas (chapters 12-15). The last chapter provides a wonderful reflection on nitinol wire-based robots and their future. The following list describes the specific topics of each chapter.

Chapter 2-Stiquito: A Small, Simple, Inexpensive Hexapod Robot. This is the starting point for building the robot kit included in the book. This chapter gives step-by-step instructions on how to assemble the kit with a manual controller.

Chapter 3-Building Stiquito II and Tensipede. This chapter describes two cousins of the original Stiquito robot and provides step-by-step instructions on how to build them. These robots require that you purchase materials from suppliers.

Chapter 4-Increasing Stiquito's Loading Capacity. This chapter presents another cousin of Stiquito. The SCORPIO robot is a modification of Stiquito that allows it to carry eight times more weight.

Chapter 5-Boris: A Motorless Six-Legged Walking Machine. Boris can be considered the inspiration for Stiquito. Boris is larger and more robust than Stiquito. This chapter provides well-written, step-by-step instructions on how to build Boris.

Chapter 6-A PC-Based Controller for Stiquito Robots. This chapter describes an interface that allows you to use an IBM PC or compatible computer to control the actuators on Stiquito II or Tensipede and experiment with various gaits. Concepts from this chapter can be used to design a simple PC controller for Stiquito.

Chapter 7-An M68HC11 Microcontroller-Based Stiquito Controller. A design is presented for an autonomous Stiquito controlled by a Motorola M68HC11 microcontroller. The system also includes a handheld remote control to send gait instructions to the robot.

Chapter 8-An M68HC11-Based Stiquito Colony Communication System. An M68HC11-based controller was designed with the ability to send and receive infrared signals. The new design incorporates the idea of a colony containing a queen and several colonists. The queen generates movement commands and transmits infrared movement signals to the colonists.

Chapter 9-A General-Purpose Controller for Stiquito. This chapter describes a general-purpose controller for the Stiquito robot. The controller has the ability to control the direction of walking, can synchronize the leg movements, and can be programmed for different gaits.

Chapter 10-SCORPIO: Hardware Design. The goal of the SCORPIO robotics project is to develop a microcontroller system for walking robots to perform independent, intelligent operations. This chapter covers the hardware aspects of the SCORPIO design.

Chapter 11-SCORPIO: Software Design. This chapter describes the software of SCORPIO, including the kernel, a control language, an on-board interpreter, and the control/sensing routines.

Chapter 12-Lukasiewicz' Insect: The Role of Continuous-Valued Logic in a Mobile Robot's Sensors, Control, and Locomotion. This reprinted article describes how Stiquito can be controlled via an analog computer.

Chapter 13-Stiquito, a Platform for Artificial Intelligence. This chapter presents examples and opportunities for studying and applying the paradigms of artificial intelligence using Stiquito. Topics addressed include genetic algorithms, emergent cooperation, and neural networks.

Chapter 14-Cooperative Behaviors of Autonomous Mobile Robots. This chapter describes a simulator designed to show Stiquito robots playing the game Hunt the Wumpus. The simulation tests cooperative behavior concepts of the robots.

Chapter 15-The Simulation of a Six-Legged Autonomous Robot Guided by Vision. This chapter describes a computer graphics simulation of a six-legged autonomous robot that wanders inside a maze guided solely by what it sees through a built-in camera located in its "forehead."

Chapter 16-The Future for Nitinol-Propelled Walking Robots. A wonderful chapter about the possible uses of nitinol wire. A must-read chapter for ideas on what to do after you build Stiquito.

Appendix A-Author Biographies. Meet the authors of the book chapters, and find out how to contact them.

Appendix B-An Analog Driver Circuit for Nitinol-Propelled Walking Robots. This appendix contains a schematic and brief instructions on how to build an analog controller. The controller is tailored for the Stiquito robot, but can be extended to other robots that use nitinol.


Excerpted from STIQUITO by James M. Conrad Jonathan W. Mills Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Table of Contents


• An Introduction to Stiquito, the Book, and the Kit (James M. Conrad).

• Stiquito: A Small, Simple, Inexpensive Hexapod Robot (Jonathan W. Mills).

• Building Stiquito II and Tensipede (Jonathan W. Mills).

• Increasing Stiquito's Loading Capacity (John K. Estell, Thomas A. Owen, and Craig A. Szezublewski).

• Boris: A Motorless Six-Legged Walking Machine (Roger G. Gilbertson).

• A PC-Based Controller for Stiquito Robots (Jonathan W. Mills).

• An M68HC11 Microcontroller-Based Stiquito Controller (James M. Conrad and Mohan Nanjundan).

• An M68HC11-Based Stiquito Colony Communication System (James M. Conrad, Gregory Lee Evans, and Joyce Ann Binam).

• A General-Purpose Controller for Stiquito (Shyamsundar Palleto).

• SCORPIO: Hardware Design (John K. Estell, Timothy A. Muszynski, Thomas A. Owen, Steven R. Snodgrass, Craig A. Szezublewski, and Jason A. Thomas).

• SCORPIO: Software Design (John K. Estell, Christopher A. Baumgartner, and Quan D. Luong).

• Lukasiewicz' Insect: The Role of Continuous-Valued Logic in a Mobile Robot's Sensors, Control, and Locomotion (Jonathan W. Mills).

• Stiquito, a Platform for Artificial Intelligence (Matthew C. Scott).

• Cooperative Behaviors of Autonomous Mobile Robots (Susan A. Mengel, James M. Conrad, Lance Hankins, and Roger Moore).

• The Simulation of a Six-Legged Autonomous Robot Guided by Vision (Pauto W.C. Maciet).

• The Future for Nitinol-Propelled Walking Robots (Mark W. Tilden).

Appendix A: Author Biographies.
Appendix B: An Analog Driver Circuit for Nitinol-Propelled Walking Robots.
Appendix C: Sources of Materials for Stiquito.
Appendix D: Technical Characteristics of Flexinol Actuator Wires.


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