The YAAARC-3 "Jeep"
Progress Report
At our April, 2000 meeting, we have agreed to move forward on a group project substantially larger than any we
have worked on before. This latest project is to start with a base platform that more involved robotics pro
jects can be constructed upon. The platform is based on one of those electric kiddie cars, consisting of a
square-tube metal frame, two 12-volt gearbox driven rear wheels, and rack steering. The metal frame is then
covered with a plywood sheet that additional hardware and electronics can be easily mounted to.
An MC6 PWM motor controller has been purchased from Diverse Electronics to drive the rear wheels. This controller
takes either a POT input or PWM, and can drive up to a 30 Amp load at 12 volts. A lead-acid battery
for a garden tractor has also been purchased to provide power to the platforms motors and onboard electronics.
A steering assembly has yet to be acquired. We are invisioning a jackscrew assembly comprised of a reversab
le DC motor with a worm gear attached to its shaft. A nut, attached to the cross-link between the front whe
els, will ride across the worm gear. By driving the motor clockwise or counterclockwise will control left an
d right turning. A feedback method is yet to be designed, and will certainly be application specific.
Applications for the platform could be: Experiments in high current motor controls, navigation, fluxgate co
mpasses, jewel compasses, GPS navigation, machine vision, stereoscopic vision, SONAR ranging, voice regoniti
on & response, Spread Spectrum radio control, RF data links for telemetry and remote control, payload delive
ry, etc. It was even suggested that the platform could be entered into local parades and throw candy to the
bystanders.
This platform should prove to be an asset to the YAAARC in the development of our skills and knowledge of ro
bots.
I propose that we name this robot platform "YAAARC-3" as our last group project was YAAARC-2...
Progress Timeline:
4/26/00 - YAAARC decided to go ahead...
4/27/00 - Ordered an MC6 Motor Controller from Diverse Electronics.
5/2/00 - The MC6 arrived. YeeHaa!!!
5/8/00
o Tested the motors using the MC6 Motor Controller from Diverse Electronics.
It worked quite well except for a strange annomoly. The motors somtimes
wouldn't run unless I just 'touch' the T0-220 power enable transistor...
o The "Jeep" can now run forward and backward using a simple program provided
by Diverse Electronics for testing their MC6 controller.
May thru June
o Wrote software to support I2C communications between a controlling computer
and the BS2 that runs the MC6 Motor Controller. The plan is to have the BS2
only run the MC6 and the Jeep's steering system in order to minimixe complexity.
The Master Computer would send "commands" (following a predefined protocol)
every 1/2 second or so to tell the motors what to do. If communication
is lost, the Jeep simple *stops*.
7/26/00
o Purchased a number of parts from Scott Edwards and Parallax to play
with:
2 - Serial BackPacks
1 - Stamp Super Carrier breadboard
1 - BS2SX
2 - Serial 8k EEPROMs
2 - Serial 8-bit A/D
2 - Serial 12-bit A/D (2 channel)
1 - Serial RTC
1 - DTMF transceiver
1 - IRODS
o Installed Serial Packpacks on a pair of 4 line by 20 character LCD's
and tested them. NOTE: They require a little bit different
programming than the S.E.E. 4x20 display, but was well worth the $60
savings over the full S.E.E. price :-)
o Integrated a 4x20 LCD into the Motor Controller BS2 software. It
indicates the status of the motors (FWD, REV, speed, Steering
position, and IRODS status).
o Developing I2C communication between two Stamps. This is so there
can be a Stamp running the MC6 Motor Controller, and a Stamp doing
other 'bot functions (navigation, decision making, throwing candy,
etc.)
o Tested the new BS2SX on a Super Carrier breadboard.
NOTE: Learned that you can't use the older STAMP2.EXE to talk to it.
You MUST use the STAMP2SX.EXE with this chip. Also note that
baudrate values are different for the BS2SX compared to the BS2.
o Tested the IRODS (Infra Red Object Detection System) and it worked
GREAT! It dependably detects an object within its IR pattern that is
within a preset range. VERY repeatable and FAST. Though I would
like a wider IR pattern as it's quite a narrow beam and could miss a
target. Might be better used on the smaller 'bots.
o Modified the Jeeps software to disable the motor controller should
IRODS detect an object. However, as soon as the object is removed
the 'bot takes off because the code loop is still running. So it's
reaction is unpredictable :-( More work is needed to develop a
'safe' reaction (hey, it was just a prliminary test afterall...)
o Seperated the two drive motors in the wiring harness. Each motor is
now brought out seperatly and now terminate in a 4-pin connector.
This allows anyone to test different propulsion schemes by making
each drive motor available seperatly.
o Temporarily mounted the 12-volt Lead-Acid battery to the frame using
nylon straps and buckles. I am still looking for a good
acid-resistant (plastic) case that will hold the battery. Saw some
inexpensive Coleman Coolers at Wal-Mart but they were too short :-(
o Built an aluminum frame to hold the MC6 Motor Controller. The frame
is easily mounted to the plywood base with two wood screws. The
metal frame provides better physical protection of the electronics
and brings out all signals to barrier type terminal strips mounted
on the top of the frame.
o Building (hope to have it done by meeting time) an aluminum frame to
hold all power management (ON/OFF, circuit breakers, fuses,
connectors, voltage regulators, etc.)
This frame extends 12-inches above the plywood base, positioning an
easy to reach push-pull MASTER switch that will be used as an
EMERGENCY STOP button. Pull the switch to turn on main power, slap
it down in an emergency to kill power :-)
o I may start on another aluminum frame, similar to the one used on the
motor controller, to support a pair of BS2 Super Carrier boards. It
would also hold a 4x20 LCD.
o Aquired a number of 486 motherboards. I'd like to run Linux on one
of them and have it be the Master Brains of the 'bot (provided we
have the programming experience within the group ).
Does anyone have any handy Linux software tid-bits, or have any
experiance or resources????