Robomagellan Entrant for EveRobotics

   Emerald Valley Engineering and Robotics

The Robo-Magellan

    * Rules of the Robo-Magellan
    * Our Robot (documentation), Specifications, Schematics, and
Source Code

Rules:

Robo-Magellan is a robotics competition emphasizing autonomous
navigation and obstacle avoidance over varied, outdoor terrain. Robots
have three opportunities to navigate from a starting point to an
ending point and are scored on time required to complete the course
with opportunities to lower the score based on contacting intermediate
points.

The robot must not be constructed in such a way as to damage the
environment or other robots. See "Safety" for other restrictions. No
robot may weigh more than 50 pounds nor may it use an internal or
external combustion engine. The robot must fit inside a 4' x 4' x 4'
cube for the entire duration of its run.

Robots must be autonomous. Remote control is not allowed, with the
exception of the remote control safety switch.

The course will be outdoors with both natural and man made terrain and
obstacles. The terrain may include pavement, dirt, small rocks, grass,
hills, gullies, trees, curbs and weeds. This list is not
comprehensive. The robot will not need to traverse a water obstacle to
complete the course although weather conditions may make some surfaces
wet and/or soggy. The contest will not necessarily be postponed in the
event of inclement weather.

Robots will be placed at a designated starting point prior to each
run. The destination and bonus way-points will be designated with
latitude/longitude coordinates and marked by 18", orange, plastic
traffic cones. Way-points will be specified as degrees and minutes
with minutes carried out to four positions right of the decimal point
(N 47 22.1245 W 122 32.0493). The datum is WGS84.

The total straight-line distance between the start and destination
will be less than 1,000 feet. However, the shortest route may be
longer due to obstacles. The route taken from start to destination,
including bonus way-points, may be significantly longer than 1,000
feet.

Our Robot:
Physical Platform:
The EVErobotics Robo-Magellan entrant is built on a Traaxxas Stampede
1/10th scale electric truck frame. We were able to reuse the stock
speed controller and steering servo by substituting the radio receiver
module's control signals with pulse-out signals output by the Javelin
micro-controller. The control signals consist of 50 Hertz positive TTL
pulses of between 1mS and 2mS with 1.5mS as null for both steering and
throttle.
Stampede truck frame
Traxxas, Stampede Frame

Transmition
Stampede Transmission
We replaced the stock electric motor with a gear motor, P/N:
MS-25010-370 sold by BaneBots to achieve a gear reduction of 10:1 for
constant torque and low speed at optimum motor rpm. The stock drive
train configuration gives the truck a 30 mph top speed! We want less
than 5 mph. The pinion gear had to be bored out from 3mm to 4mm to
accommodate the larger diameter gear motor shaft.  We may also try an
alternate gear-motor sold by the same company, P/N: MP-28005-385 that
has a 5:1 gear reduction.

gear motor
MS-25010-370 Gear-Motor
    or     planetary gear motor
MP-28005-385 Gear-Motor
The stock springs on the truck frame were replaced with heavier
springs to enable the frame to support the added weight of batteries,
embedded computer, sensors, and micro-controllers. Also, we will
eventually have to retrofit  the drive-train with metal parts when it
fails from moving 3-5 times more mass than it was designed for.

Controllers:
The micro-controllers used in the robot are a Javelin Stamp made by
Parallax, and an ARMmite single board programmable controller made by
Coridium. We presently use the Javelin to manage the sonar sensors and
control throttle, brake, and steering. The Javelin speaks Java (or a
subset of Java with hardware control libraries), and the ARMmite is
programmed in C or BASIC (C for me thanks). We use the ARMmite to
process data from the GPS module and the electronic compass. The
ARMmite stores an array of GPS way-points which it uses to calculate
the robots heading, desired heading, and cross-track error,  then it
relays suggested steering information to the Javelin serially. The
ARMmite was an exciting find; it speaks ANSI/ISO C99 and the compiler
is GNU C. The development software is free, easy to use, and allows
you to use the editor of your choice (Notepad++ is the way to go). The
ARMmite development software is also distributed with hardware control
libraries (all open source). For language purists the ARMmite and the
Javelin are ideal, the hardware libraries are open source and the code
is perfectly familiar if you know Java or C/C++. Furthermore, the
ARMmite's specs blow its competition out of the water; it's ARM7
processor runs at 60Mhz (the Javelin runs at 25Mhz, and the fastest
Parallax has to offer, the BS2sx-IC runs at 50Mhz), the ARMmite
executes 10 million+ instructions per second (Parallax's best the
BS2px-IC only runs 19 thousand, and the Javelin runs a pitiful 8,500),
the ARMmite can be programmed over USB, Bluetooth, Zigbee (wireless),
or serial RS-232; the list of advantages goes on. The ARMmite is a
powerful and capable industrial grade controller sold at the same
price as the hobbyist grade Parallax products. Alright, enough with
the sales pitch, I don't work for Coridium, I promise. Lastly we have
integrated a fully fledged embedded computer into our design. The  AR-
B5230 mother board made by Acrosser processes data from cameras and
other sensors to form a map of the robot's environment and make
complex decisions based on all the information available to it. The
computer also serves as an embedded development platform for its own
software as well as the attached peripheral controllers, and as a
means for remote control and/or remote monitoring of the robot via an
802.11g wireless network interface.

Javelin Stamp
Parallax, Javelin Stamp Module     ARMmite
Coridium, ARMmite Controller     AR-B5230
Acrosser, AR-B5230

Sensors:
The sensors that have been acquired and installed so far are a GPS
module made by Parallax,  an electronic compass, three sonar range
finders also made by Parallax, a rotary encoder, and two USB cameras.
The GPS module provides data for navigation between way-points, the
compass gives the robot accurate heading information, and the sonar
modules provide data for obstacle  avoidance, the cameras are used in
a machine vision system which identifies 18" orange traffic cones and
in the future will do more advanced analysis of the robots
environment, and a rotary encoder mounted on the motor acquires motor
rpm. Other useful sensors  include switches affixed to feelers to
ensure that the robot can detect and navigate around obstacles
invisible to its other sensors,  as well as an accelerometer to
measure incline etc. to be used in an inertial navigation system.

GPS Module
Parallax, GPS Module     Ultrasonic Sensor
Parallax, Sonar Range Finder     Compass Module
Robot Electronics, CMPS03
 Electronic Compass Module
Encoder Sensor
NTE,  NTE3100, Photon Coupled Interrupter Module     USB2.0 Color CMOS
Camera
Digitus, USB CMOS Camera     Accelerometer
Dimension Engineering, DE-ACCM3D, 3 Axis Accelerometer
Specifications:

    * Javelin Stamp
    * ARMmite
    * AR-B5230
    * GPS module
    * sonar range finder
    * CMPS03 - Compass Module
    * DE-ACCM3D Buffered ±3g Tri-axis Accelerometer
    * NTE, NTE3100

    C Source Code:

    * GPSMain.c
    * GPS.c
    * GPS.h
    * crossTrack.c
    * crossTrack.h
    * gpsOut.c
    * gpsOut.h
    * compass.c
    * compass.h

Schematics:

    * Javelin Stamp
    * ARMmite

    Java Source Code:

    * magellanMain.java
    * GPSModule.java
    * sonarSensor.java

System Controller Source Code

    * Sputnik.cs
    * Vision.cs
    * Coridium.cs
    * Javelin.cs
    * Diolan.cs
    * I2C.cs
    * Program.cs

Theory of Operation:
Our robot uses a GPS module, an electronic compass module, and a
rotary encoder to navigate between an array of way-points.  Each way-
point is a longitude latitude coordinate pair that has been
manipulated by an expression which converts the coordinates to base
ten values using dimensional analysis. Once the coordinates are
converted to base ten coordinate pairs it does math with them. The
robot converts the rectangular coordinates to polar form and then it
finds theta, the angle between north and target way-points, this
becomes the robot's desired heading. Then it figures out which
direction it should turn based on the values of its desired heading
and its present heading (given by the electronic compass). Lastly it
computes cross-track error (the difference between the desired heading
and the present heading). Using this information the robot can decide
where it needs to go and how to get there. The sonar sensors provide a
means for obstacle detection and avoidance, but play no part in macro-
navigation, if there were no obstacles they would not be used at all.
Lastly, two USB web-cameras and an embedded PC running WindowsXP and a
custom application written in C# enable the robot to identify 18"
orange traffic cones that mark the way-points and touch them (GPS is
only accurate enough to put the robot in the neighborhood of the way-
point). The cameras will also be used for an adaptive vision system to
aid in obstacle detection and avoidance.