Aurora's Home Robotics

The Quest for Autonomous Robots

Autonomous means "self-governing" and "independent". Just what I wanted - a robot to clean up my room without me having to worry about it.

I started wondering how to design a simple robot for robot-crazy teens to make, but with lots of complicated-looking parts. This page is dedicated to the "tech-talk" about how this project evolved. If you are familiar with or have experience with electrical engineering, software, or hardware, and are the do-it-yourself type of person, this page may be an excellent inspiration for you. If not, click here to visit the other robot page.

I ran across some inexpensive micro controllers(Atmel AT89C52) with 8k flash memory that could have a BASIC interpreter put in.  This micro controller has lots of I/O ports to work with (32!), and would drive full-bridge PWM motor drivers (Allegro A3952SB) that could handle high current (2 A) for the drive motors.  Light sensors (CdS and photogate), IR detectors, and contact (touch) switches makes this robot autonomous and able to interact with its environment. 

The system runs on 9V (for motors) & 5V (all electronics), carries all its own power, brains, and mechanics.  Putting these elements together makes for a cool robot that kids can make themselves in a summer RoboCamp! 

Our Goal: 

To design and build a robot that interacts with its environment.  Pretty simple, and very wide open.  The only thing we had to abide by were the chips we had on hand (mentioned above). 

Three weeks into this project, Alexa the Robotic Excavator was roving around the floor on her own, going forward, reverse, turning wide and spinning on her own axis.  She can sense black and white boundaries, track a light source, and execute several different digging programs.  Total project cost thus far:  under $40 (this is if you were to buy everything from scratch, including sensor parts... we were lucky enough to have all our electronics on hand, so it was more like $20).   Total project time: 75 hours (including programming time!).  Transferring it all to a proto-board and make it into a nicer-looking package:  8 more hours.

In the photo above, we're playing with the motor driver chips, turning a fan on and off using directly applied voltage.  We then added the CPU (not shown), and had it turning the motor fans and muscle wire on and off after some quick BASIC programming.  We played with CdS sensors, phototransistors, IR detectors (as proximity sensors), touch switches, pressure sensors, and more.  We hooked up input sensors to the CPU which then determined how the output motors would be driven.  Total project time thus far:  under 2 hours.

Excavator "Alexa"

After a late dinner near Christmastime 2001, I found a selection of inexpensive (wired remote-controlled) construction toys at our local thrift store.  This one is an Excavator, and uses four different motors.  One motor each for the drive (which go forward and reverse), one for moving the arm, and one for moving the scoop.  The motors work as linear actuators, moving the pistons in and out.  The whole contraption runs on 4 AA's.  It was a lucky find  - a toy that had motors and gears already installed!  We played with the different models, figured out our project design based on this new platform, cut off the remote controller, and re-wired the motors to a new board.  This new board had to have four motor drivers.  Project time this far:  3 hours.

The board installed on Alexa the Excavator.  The little ICs are the drivers, the larger is the CPU, and LEDs indicate motor direction.  A CdS is our only input at the moment, but we are soon mounting IR proximity detectors and touch sensors so she can interact with her environment.  Total project time thus far:  5 hours.

The photo below sure looks more complicated than the above close-up!  Alexa is completely autonomous now (she can run by herself and react to her environment without human intervention).  The difference now are the sensors are all wired, a serial port was installed for debugging, and an LED display shows which program we're running (10 different ones to choose from!)  Alexa carries her own power (6 D-cells), and in a sense, is very similar to the LEGO Mindstorms robot in that it is independent of the computer once its programmed (no wires but on the robot).  

Funny problems we faced:  She chugs along at a fast rate - too fast, in fact.  We had quite a time getting her to see the black line - the robot would speed right over the line without the CPU catching it in time.  When we tried to the proximity detection system (IR),  she climbed right OVER the barriers instead (great tread capability!) of "seeing" them and avoiding the objects. 

Photos Below:  Alexa has contact switches at each of the arm and scoop mechanical limits, so she knows when fully retracted or extended.  She's also got three CdS photocells on board for seeking light, and IR detectors everywhere.  The IR detectors help her detect walls and avoid objects as well as locate a pile of candy to dig (the pile itself has IR emitters).  Alexa also has two photogate type light sensors mounted on the base pointing toward the floor, so she can stay in a white-floored rink defined by a black line (she won't cross the black line) as well as line-track a black line.  Whew!  Total project time:  75 hours (about three weeks).

Well, we have now prototyped the board, neatened the wires, and have recorded movies (link soon!) of Alexa for your viewing enjoyment.  She currently has different 10 programs on board, and you push a button to select which program number you'd like, then another button to run the program.  She has a detachable umbilical cord that runs optional power (so we don't burn up so many batteries) and a serial connection to our laptop computer (for watching her thoughts as she does things).  It is mounted with 16 sensors (4 touch switches, 3 light sensors, 2 IR photogates for seeing white and black lines for line-detecting, and 7 IR emitters/detectors for proximity detectors), 4 motors, 1 CPU, 1 LED display, 3 switches, and lots of LEDs!   Total project time: 83 hours (roughly four weeks). 

The programs range from:  "Reset position" where it figures out its arm & scoop position, then retracts the arm and scoop;  "Dig" where it will scoop and transport and dump;  "Line-Track" where it will follow a black line (made of a strip of electrical tape on white posterboard);  "Light Seek" where it scans for light, turns towards it and travels right to the source;  "Avoid Sequence" where is travels around a room and avoids smacking into walls... and more!  We've got these programs prioritized, so we can run them independently, or all at the same time:  it seeks light while traveling in a room, all the while staying inside a rink defined by a black line, but avoids obstacles in the rink, digs and scoops near a light source, and so forth. 

This was so much FUN to build!!! 

The two below (Dozer Bulldozer and Gemini Backhoe) are additional projects that will eventually "talk" to each other via Infrared communication. 

Tuppy

Tuppy is a line tracking robot, using LEGO wheels, IC comparator, visible light detectors, and gear-head motors.  Tuppy can track white lines on black or black lines on white while blinking yellow and green indicator LEDs!  Very nice project for first-timers.  The book is a bit lacking in exact directions for circuitry, but all the more fun to figure out!! 

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Thanks again and again!"

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