Updated 2/1/2005

PAAMI's current appearance before installation of gripper assembly and can sensors.


Priority Arbitration Architecture Machine Intelligence

Basic Concept 1

Pid Drive Experiments

Wheel Encoder

Bumper Optimization

Beacon Sensor Testing

Dual Battery Charger

The Docking Station

Drop Off Sensors

Rear Bumper

IR Imges of Sensors

New Arm and Gripper

Stasis Sensor

Priority Arbitration Architecture

 This is the home page of our latest robot, a machine based on a very recent concept in programming and physical hardware using Priority Arbitration Architecture, implemented in a strictly hardware fashion. What this means is rather than a single large processor controlling her, PAAMI has over a dozen microcontrollers running in parallel, simultaneously. While an in depth description of her architectural concept can be found here, the basics are simple, a layered series of behaviors each programmed into one processor and running independently of the other behaviors. All 8 layers of behaviors are in order of priority, with the most important at the top of the stack. The behaviors control of the robot is arbitrated by the arbiter processor, which allows only the highest priority processor that is requesting control over the robot to actually have full control. So each processor can be programmed separately, and finished before we move on to higher level of behaviors. This makes the programming 10x easier, but the amount of hardware is increased a bit.

On the electrical side, PAAMI has two 12v gel cells - one for electronics and one for the drive motors. Two 5x7 circuit boards are point to point wired with ribbon cable interconnection. All Processors are PIC processors running at 10MHz each, of several different types. She carries her own constant current dual battery charger to simplify docking connection to two contacts. All drive, LCD and other signals between processors are send along 9600kb serial busses. Access to the electronics is through the hinged lid on top, which the beacon sensor is mounted. Programming is done in PICbasic from Micro Engineering Labs and burned with the Microchip Picstart Plus burner.

Current behaviors

Pammi has 8 possible levels of arbitrated subsumption. Currently not all slots are filled, but as she grows we can add more levels and more processors. Here is a list of the current levels, from highest priority to lowest:

Decide:  Controls day/night activity and oversees general movements using sonar to plan routes.
Impact:  Bumper, and  drop off evasive actions
(Seek)    Finds cans or tennis balls
(Gripper)  Controls gripper
IR Avoid:  Proximity object avoidance before impacts occur
Charge Beacon:  Locates and connects to charger, turns off power, sleep at night. 
Sonar Cruise:  What we do when nothing else is going on.  Move forward within a fixed distance of objects then either veer a bit, or turn away.

Each of these behavioral processors can control the drive motors, the LCD display, the audio speaker, and status lights, and soon the arm/gripper. The higher behaviors can subsume all the behaviors below them. A trigger which can be an event such as bumper impact to beacon detect can initiate the processor to subsume the rest below it.

The Future

The best is yet to come with PAAMI. After we finish up with the drop off sensor array and new back bumper, a sophisticated optical scanning array will be installed on the front to detect soda cans and tennis balls. A pivot down gripper will then arc over the top of the robot, grab the soda can and PAAMI will stack them in a designated area. That is our ultimate goal for her at this point. The skill learned in constructing this robot will apply directly to our next robotic project, an outdoor dual tank track locomotion robot, tentatively called "GeoBot" that will autonomously collect rock specimens and return them to base.

PAAMI Pictorial

  Top View - About 16 inches long, PAAMI is constructed from a clear polycarbonate called "Hyzod", available in sheet form. Top and base plates are 1/4" with the pylons between 1/2" polycarbonate as well. The bumper is 1/16 inch material and everything else is 1/8 inch Hyzod. From this top view you can see the batteries in the rear, beacon sensor dome flanked by the battery charger circuit, LCD display and primary board stack.
  Side View - The large 5 inch wheels allow movement in the home environment over numerous obstacles such as shoes, cat toys, and deep carpeting. A rear ball shaped caster wheel rides freely and can reverse its orientation to suit. Here you can see the drop off sensors which keep her from going over stairwells.
  Frontal View - Plenty of sensor action here. The entire front of the bot is one huge bumper plate, bent as it surrounds the angled sides. The four black boxes on the front are IS417 proximity sensors which has a range of about 6 inches in normal lighting. Each has two powerful IR LEDs and seem to work fine even in bright sunlight. Dominating this scene is the beacon sensor, under the clear bubble on top. More on this in the next panel. Just under that is the Devontech sonar sensor for obstacle avoidance in the cruise mode, and perhaps later for scanning for soda cans. The dual homing photocell array works in a very unique way. It is constructed to use fuzzy logic to determine the most likely location of a white light source. That would be windows and a large Arcadia door. Thats where the charger is and allows the robot one more piece of information to find the charger.
  Left - The beacon Sensor. A substantial write up on its construction can be found here. What Id like to add to that it works pretty well through the clear dome, and protects it from impact damage. The golden arcs in front are a new bumper design I've been experimenting with, using the E string on a guitar. The shorter arc is in front of the rear arc, about 1/4 inch. When an object such as the coffee table shelf or cat scratching post will hit the dome, which is above and not protected by the bumpers, the front string bends like a spring and touches the rear one thus creating the electrical contact for an evasive response to follow from the Impact Processor. Amazingly, the beacon sensor works fine with this in front of it.
  Bottom view - Lots of action going on here too. Besides the wheels and motors which move the bot at a maximum rate of 1/3 foot per second, the stasis sensor wheel (detailed here) rolls along the middle as well. The large copper plates on the front are for connection with the charger shown better here. And all four drop off sensors can be seen on each side of the wheels. A fifth one is not shown here, behind the caster wheel. A write up on the charger and plates can be found here.
  Rear View - The back bumper consists of two plates of thin lexan with the main power switch in between. I am redesigning the rear bumper assembly at this time to include a rear drop off sensor to keep the bot from rolling off backwards down the stair way.
  Front Underside - Careful examination of this image shows the thin stasis wheel in the middle between the motors. It has a rubber O ring around its edge to ride smoothly without slipping on nearly any surface. Paamis speaker is a 16 ohm flat polyester type which can be driven directly by the processors arbitrator mux. Right in front of it you can see a gap in the bumper coverage. This clear spot goes about three inches in. Here will be the optical array for the soda can and tennis ball sensors. Later, the gripper assembly will be mounted on top, with a gripper that comes down from above and grabs the item.

You are visitor number since June 17, 2001

FastCounter by bCentral