uploaded 3/26/04

Ostracode:  A small shrimp like bivalved crustacean occupying both fresh and salt water.

Movie 1:  Round the room - This demonstrates IR object avoidance and navigation
Movie 2:  Screen door escape and Cat interaction - The IR detector would not see the screen door, but the stasis sensor
engages and corrects the stuck condition.  For the most part, the cat doesn't mind the robot  unless it is touched by it.


      

      
 Ostracode is a completely autonomous mobile robot which travels
      exploring the upstairs level in our house. He is powered by twin
      processors, a Parallax B2-SX and a PIC12F629 microprocessors.
      Two Fituba servo motors power his movements, and an 8 AA pack
      Nickel Metal Hydride battery pack putting out 10.5 volts powers
      him. His weight is balanced toward the rear with the battery
      pack, and there you'll find the third caster type non driven
      wheel. A fourth encoder wheel rides exactly in the middle of
      the drive wheels and is used by the PIC to determine if he is
      slipping while driving forward.

      
Sensory input is from 4
      front and rear microswitch bumpers, 4 Modulated IR Panasonic
      proximity detectors, two under and two over the mid section.
      Also, two front facing Cadmium Sulfide photocells provide for
      day/ night detection and photo tropic tracking. This is my fifth
      robotic project, the first being a 16F84A PIC microcontroller
      bot called "Twitchy", the second was the "Aurora
      Cam" Robotic Camera, the third Boe-Bot, Fourth "PIC
      BOT" with crude Subsumption architecture, and finally this
      robotic crustacean.



      
 Behaviors:

      
- Wanders constantly, avoids
      any obstacles in path, be it laying on the floor or taller. Moves
      forward normally and when it encounters an obstacle it responds
      by an avoidance program, chirps randomly using a synthesized
      cricket sound, the speed of chirping dependent on the encounter
      situation.

      
- When he is stuck and
      the sensors are not seeing an impact, a crude Subsumption Architecture
      kicks in and he can initiate an escape routine which has been
      very successful.

      
- He has numerous "escape"
      routines to get him out of a tight situation, such as under a
      table or chair.

      
- At night, he determines
      several times it is truly dark by rotating 180 and measuring
      the light again. If the threshold is well below normal room lighting,
      he heads for the nearest wall until he touches, backs off three
      inches, spins 180 to face outward, and t hen shuts himself down
      for the night. He then checks every 10 minutes to see if its
      getting light out.

      
- A crude SA causes him
      to become phototropic - light seeking when his battery voltage
      gets to about half level.

Details

Development Environment:

For the BS2-SX the standard latest version of the Parallax Basic Stamp software was used. Dealing with the 8 "Banks" of program space is painful, but it does give 8K of storage. For the PIC processor, the program was written in PICbasic by Micro Engineering Labs, and compiled to HEX. Programming the chip I used Microchips PicStart Plus programmer and the provided software MPLAB.

      
 Left: Frontal
      View showing details inside of twin disc housings. Inside you
      can see the dual front facing modulated IR tranceivers I made
      up from angle brackets and IR LEDs, and Panasonic Detectors.
      Everything must be grounded to keep the 38.5 KHz from getting
      into the amps and receiver circuit!

 Right:
      Top view showing the removable cover, with 4 brass thumb screws.
      A window cut into the lid allows seeing the display board, with
      indicators for battery voltage, right or left activation, and
      Photocell readings using red, blue and green LEDs.

      



      
 Left: Underneath
      on the left are the rear bumpers which are only used when in
      escape back up mode to make sure you stop if you hit while backing
      up. Twin hacked Fitubo servos drive the base, and on the right
      the huge microswitches with 2 inch long levers have .032 music
      wire whiskers on them that are captive on the ends with nylon
      lace cord to keep from catching objects while the robot is rotating.

 Right:
      Close up of the rolling fourth wheel used for slip detection.
      A photo interupter looks at the wheel which when the bot is moving
      is generating 0 - 5v pulses into the PIC. By counting the pulses
      for one second, you can determine if the robot is stuck. If the
      counts are less than 2, he performs a backup escape manuever.
      Over 2 and he continues forward. Its simple, took only a dozen
      lines of basic code, and works extremely well. The wheel is hinged
      so it always is pressing against the uneven floor.

      



      
 Left: Underside
      view of fourth wheel which MUST be located between the drive
      wheels for best results. This makes it impossible to side slip
      while turning. Yes, thats dental floss holding the whisker from
      ripping off...

 Right:
      With power on, the status of the internal systems can be seen
      through a window on the top. In the center, a crude bar graph
      shows the battery voltage indicated by a quad LM339 compartor
      set for 10,9,8,7v. Right left IR impact lights are both on (he
      was aiming at the paper backing) and the blue LEDs, one on the
      upper left shows which CdS photocell is the brightest at the
      time.

      

This will certainly be my LAST robotic project with the Stamp type microcontrollers. I have moved to Microchip PIC processors because of thier extreme speed, huge varieties available, internal functions and CO$T. I use them at work for designing complex robotic applications. My next project we just started, is P.A.A.M.I. I will require bunches of cheap paralell processors to implement this new robot and the PIC's are perfect for the task.

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