🚀 go-pugleaf

rbyrnes@alsvid.une.edu.au (Rod Byrnes) writes:
>I'm in the process of designing a droid, and am wondering how to power it. 
>...
      Beyond batteries, the usual solution for larger machines is
an internal combustion engine.  CMU and White Sands have both built
engine-powered mobile robots, and some factory AGVs are engine-powered,
notably Caterpillar's, which has considerable parts commonality with
their lift trucks.

      Something that really needs to be done is to develop a suitable
engine powerplant for indoor robots of moderate size.  Here's an approach
I looked into once, but never did much with.

      Start with a small four-cycle engine generator, something about
1HP, maybe 300W continuous, 600W surge capacity, preferably water-cooled.
Get it converted to run on butane.  This is a standard conversion, and 
will result in a powerplant with exhaust suitable for indoor operation.  
(Butane-powered lift trucks are routinely used indoors.)  A four-cycle
engine is required because two-cycle engines with lubrication via oil
in the fuel aren't suitable for butane operation. Briggs and Stratton
has some nice little engines.

       Repackage the powerplant.  Remote the radiator, encase the engine
in fiberglas and metal.  Add a really good muffler.  Add temperature,
butane pressure, water level, RPM, and vibration sensors.  Add a 
minature Halon fire suppression system (available from a boat supply
house; these are simply a Halon cylinder with a sprinker head and an
electrical pressure switch to sense discharge).  Provide standard
butane cylinder plumbing for butane-torch cylinders.

       Build an engine control system, with hard-wired overtemp/overspeed/
vibration/fire extinguisher triggered emergency shutdown.  Add a
microcontroller for general control of engine, generator, and electrical
power system.  Provide suitable controls for starting the engine, using
the generator as a cranking motor.  The electrical power system will
involve several power supplies.  One will run off the battery used
for starting, critical loads, and engine-off operations, probably through 
a DC-DC converter.  A second will only be turned on when the generator
is running, and will supply most loads.  Finally, loads requiring heavy
power (drive motors) will be driven directly from the generator.  For
short periods, just as with a car, the engine can be driven at well above
its continuous rating, and such a capability should be supported, with
the robot's control system cooperating with the engine control system
to do this safely.  This allows the use of a much smaller engine.

       The end result should be a box around a cubic foot in volume
that can run a sizable robot all day.

       I'm outlining a non-trivial engineering task here, but someone
who has a background in both computers and motorsports, and a really
good shop, should be able to do it.  A good project for someone in
one of the heavy engineering schools.

					John Nagle