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GatorKS

GatorKS is my latest and most advanced robot.  The robot uses the ATMEL AVR microcontroller board I designed, based off of the ATmega640/1280/2560 family.


Contents

  1. 1 Mechanical Aspects
    1. 1.1 Drive System
    2. 1.2 Actuation
  2. 2 Electrical Aspects
    1. 2.1 Processor Board
    2. 2.2 Sensory and peripherals
  3. 3 Software Aspects
    1. 3.1 Behaviors
    2. 3.2 Control Systems
  4. 4 Future Work



Mobility Demo

Mechanical Aspects


Drive System

GatorKS has an omni-directional drive system.  This means each wheel assembly can be moved independently as can the angular velocity of each wheel.  This sort of drive system has many advantages.   Two of which are featured in the "Mobility Demo" video to the right.  The robot us shown translating while maintaining a fairly consistent heading.   Also the robot displays the ability to rotate about its center axis.  Essentially the robot has no turn radius.

 



Actuation

GatorKS uses 6 Futaba s148 servo's for its drive system.  Half of them were modified, and the other three are standard.  The modified servo's allow for continuous rotation, which makes them ideal for powering wheels.  The unmodified servo's have an angular range of 180 degrees, and are used for positioning the wheel assemblies of GatorKS.  The 180 degree's of motion for the positioning servo's is enough for full 360 degree positioning when considering the modified wheel servos can turn both clockwise and counterclockwise.

There are two additional Futaba 3003 servo's on GatorKS.  One is for panning a ping sonar sensor, and the other is for tilting a Nintendo Wii Remote.  There is also a speaker blower mechanism (shown below).


Electrical Aspects

Processor Board

The processor on GatorKS is and ATMEL ATmega640 microcontroller.  This microcontroller has a rich variety of features.  At the moment GatorKS utilizes only a few of these.  The highlights are 16 ADC channels, 4 USARTs, SPI, 6 timers, and 12+ Hardware PWM pins.  For the complete feature list take a look at the datasheet.

The Board I designed to house the ATmega640 is also augmented with USB support for UART0.  All of the i/o was designed to be space at .1" (25.4mm) for easy interfacing of protoboards.

Sensory and peripherals

GatorKS has quite a few sensors already.  There are 4 Sharp IR range finders, 2 Ping sonars, and a Nintendo Wii Remote all on board.  The Sharp IR sensor's are currently only used for wall following.  The ping sonars are used for accurate ranging, aqnd the Nintendo Wii Remote is used to track infrared blobs such as fire. GatorKS uses a Bluesmirf Bluetooth module for wireless PC communication, which is necessary
for using the Wii Remote.

Software Aspects

Behaviors

Currently GatorKS has two unique robotic behaviors at the moment.  The first was wall following.  The video first shows the robot aligning itself parallel to the wall.  Next the robot uses it's panning sonar to measure how far the robot must move from the wall.  Just before the robot begins to follow the wall, a Sharp IR range finder value is stored in memory.  This value is used to keep the robot a set distance from the wall.  The panning sonar then serves to eleviate collisions due to corners, and sharp turns.

GatorKS Wall Following


The second behavior is firefighting.  GatorKS uses the Nintendo Wii Remote to flocate the flame of an oil lamp.  Once the flame is detected the robot steers toward the lamp until the robot is a set distance away.  Then the robot uses the speaker blower mechanism to put out the flame.  The speaker blower mechanism is intentionally underpowered, and required very accurate positioning to use.  This behavior is designed to show the dexterity of GatorKS.

GatorKS Firefighting

Control Systems

Each behavior of GatorKS has multiple linear control systems at work (PI, PID etc.).  These control systems make GatorKS more responsive accurate, and fluid that simple boolean expressions.  The wall followinf be havior has three controllers.  One for alligning the bot with the wall, another for moving a set distnace from the wall, and the last is for maintaining this distance while following the wall.

The firefighting behavior has multiple controllers for tracking the x and y position of an oil lamp.  It is probably more accurate to say that the tracking is of x and y rotations, rather than displacements, since the robot is tracking with angular movements.  The below video shows how responsive, and smooth GatorKS is to track the fire.

GatorKS Flame Tracking


Future Work

GatorKS is a very new robot.  I have only been developing the design for a month now.  I plan to add more features and behaviors.  I also will be putting time into perfecting the firefighting behavior.  Some additional behaviors I want to implament are human tracking using IR leds + the Wii remote, or another embeddedd camera solution.  I also want to try mapping.

last updated August 16, 2009