Here
      is an update on the current progress of the Cbot Robot. For the
      second half of April, I concentrated on developing the automatic
      battery charger and beacon so that we can keep the robot at full
      power during the next phase of testing. One of the most important
      functions a household robot must do is be able to find the battery
      charger, plug itself in, and charge itself up on a daily basis.
      For the Plant robot - this means that after it has completed
      its watering task every morning, it must return to the charger
      and slowly top off the 12v battery for the rest of the day and
      into the night. The next morning the Sun comes up - and we do
      it all over again. Below you'll find some photos of where we
      are at on this and an inside look at how the brains of the robot
      will accomplish the entire watering task!
 

      
Left: First
      thing was to construct a solid and reliable docking station,
      complete with 500 ma battery charger, an adjustable infra red
      beacon and two charging plates the robot can drive into to connect
      up. Here is a bench test of this in action. The docking station
      is on the left and has a red light just above the contacts to
      confirm there is voltage present. (13.5v to charge a Gel Cell).
      The robot on the right (without its dome) has two "feelers"
      made from a Guitar E string that are connecting to the plates.
      The battery is able to charge fine WHILE THE ROBOT IS ON. This
      allows the robot to just drive up and charge at will.
 
Here inside
      the robot arena, you can see the charger/docking station more
      clearly. The electronics are inside the metal box, and the dome
      at top has a bar of infrared LED lamps for the robot to home
      in on to park itself right on the plates.
 

      

Viewed
      from above, the guitar strings are just touching the plates and
      connect directly to the battery terminals in the robot. The white
      C shaped foam piece is connected to a lever switch. If the robot
      keeps driving towards the plates and does not stop because it
      detects no voltage, the switch closes and that will stop the
      robot. It is a fail safe.
 

      
Inside
      the docking beacon. The bottom board is a small 12F629 micro
      controller that puts out a constant 38.5 khz signal. This drives
      the second board which contains the IR LEDs.
 

      


      
Click to
      enlarge!
The
      docking beacon detector that is to be installed on the front
      of the robot started out like this, three pieces of brass shim
      stock soldered to form a vane sensor. Two photo cells that respond
      to 38.5 kHz Infrared light are on each side of the vane. by pointing
      the vane right at the beacon, both photocells will put out a
      signal. If its to the right or left - only one will thus the
      robot can home in on the beacon. This all gets painted flat black.
 

      

The
      beacon sensor now installed on the underside of the top plate
      of the robot.
 

      

      
A diagram to show
      how the robot is currently being programmed to accomplish the
      plant watering task. This type of diagram is called a "Finite
      State Machine". Each bubble is a separate state the robot
      can be in at any time, depending on what its doing. Each state
      is simply a separate block of code. The arrows show how it can
      jump from one state to another.

      
The human brain
      works in a similar manner. We mentally jump from one mind set
      to another all the time, say from walking to driving a car then
      talking on the phone. Each task we do is a separate mind state.
      Same here. This technique is very powerful in defining the artificial
      intelligence of microprocessor controlled systems.


Here is
      an example of whats inside each bubble above. This is for example
      the "Docked State" internal flow chart. Each bubble
      has its own internal diagram like this and you use it to guide
      you as you actually write the program to put into the robots
      micro processor. I have not finished ALL of the inner flow charts
      yet, but each step of the way is clearly defined for the future!

 

      
Interested in learning
      more on the development of this robot? Here are previous uploads:

      
Previous Articles
1. Plant watering sensors
2. Cbot basic concepts and project definition

BACK TO ROBOT PAGES

HOME