IN THIS ISSUE:
Project Update
The Emailbag
Solar Power and Battery Babysitting
The Brain Interface Unit

ALERT: Don't take the density of aluminum for granite! It's
tempting to throw unlimited aluminum at a project, thinking it
light... but its density is almost identical to that of
granite: 2.64 versus the rock's 2.69. A cubic foot of
aluminum weighs 165 pounds; of granite, 168. Bike parts, eh?

Project Update


Two weeks have passed. Most of you took off for the holidays
-- the email and phone have been eerily quiet. What have I
done with this surplus of time?

Hm. One thing about a system this complex is that apparently
trivial components -- the ones we take for granted -- end up
monopolizing huge blocks of time. Considering the fact that
it's MY time we're talking about here, that 29 weeks left until
departure is already feeling like quite a squeeze. I did learn
something useful about that during a recent visit to Trimble
Navigation, though: admiring the project organization
represented by a giant D-size PERT chart, I complained that
when I tried to use InstaPlan for similar purposes, it just
turned into an intimidating graphic linear TO-DO list.

"Project management tools assign resources to tasks," an
engineer told me. "In your case, since you're the only
resource, it doesn't make any difference what you work on.
Just DO something!"

This obvious little bit of advice changed my life. Duly
inspired, I hustled back to the lab and got to work... spending
the last couple of weeks on gasket-compressing latches and
manpack tie-downs for the RUMP lid, OrCAD PCB software
installation, Lemo environmental connector specification, the
IBC BoardMaker learning curve, setting up the bike's new MIDI
system, testing commercial audio amplifier modules with the
intent of finding low quiescent power drain, probing the myriad
trade-offs of battery charger design, working on the
multi-platform SCSI bus architecture, and trying to get my body
in shape with weights and a new sweat machine. Presumably, all
these except for the last one will eventually find their way
into articles here, so let's get on with the mail...

The Emailbag


John Chapin here at Sun writes:

Are you set up so that I could drop by your lab occasionally
and see what's going on? Mostly to get a visual impression of
all the neat stuff you describe in your newsletter.

I expect a fair number of those 367 people are on the Sun MTV
campus like I am, so I'll understand if you need to be
organized about visitors. How about some open-house hours a
couple times a month?

John...

Excellent idea... I'm planning on it! I'll do a posting to the
Sun-local nomadness alias when the time comes, probably
sometime in mid-January. (Oh, and it's now 434 subscribers,
not counting reposts and forwarding.)

Also, sometime just before departure, probably in early July, I
will have some kind of send-off event, hopefully here at Sun.
We're talking with a couple of bands, and will invite all local
sponsors, media, Bay Area friends, and so on. More on that as
it develops!

This from Dave Webb at Tektronix:

Steve Sergeant and I were discussing your plans for vertical
handgrips in the steering of your recumbent, as an alternative
to the conventional horizontal steering bar. Riding
frequently in the Oregon rain, I occasionally use the steering
bar to pull my bike (a lightly modified Infinity recumbent)
back underneath me when recovering from skids. Is your vertical
handgrip position in danger of compromising your ability for
skid recovery?

Since one can't effectively lift one's ass from the seat on a
recumbent when trying to recover from a skid, the steering bar
serves both to lever the bike into a more vertical position,
and to help slide oneself sideways on the seat, allowing the
bike to remain vertical if one has reacted quickly enough. It
seems that being able to lift oneself by the hands plays a part
in these actions. I don`t have good data on this, because I
don't intentionally put myself into skids for experimental
reasons. However, it is fairly easy to get the Infinity into a
skid, because there is very little weight on the front wheel.
I've collapsed a steering bar once doing this. The steering
cables become much more like horse's reins when this happens.
The cable to the unbroken side of the steering bar still worked
(in tension, of course), and by leaning the bike to the other
side, I was able to keep the usable cable in tension until the
bike could be stopped. After this incident, Infinity doubled
the wall thickness of their steering bars.

Another consideration in steering bar design is the effect of
sideswiping, or being sideswiped by another vehicle. The
steering bar is the widest part on my bike, and is vulnerable
to this. Perhaps this is less of a threat to your new design.
Please let me know the details.

Dave....

Thanks for your thoughts on the steering... I've pondered and
worried about it myself. Original motive of the new design is
to increase typing/flute-playing speed, and the configuration
evolved from lots of thoughts about what happens when it falls
over, where the grips hit, etc. My one lingering concern is
the movement of my body on steep climbs... might need a
5-point harness to prevent wasting energy! :-)

I haven't had much experience with skids... very rare on a
megacycle like this. I'm trying to remember times when I put
substantial force on the bars, and I honestly can't (with the
possible exception of pulling when hill climbing to lock myself
into the seat). But width is an issue -- on a narrow Florida
bridge once, my right shifter hit the back of a guy fishing,
not only infuriating him and nearly causing an incident, but
also driving me into the concrete wall and nearly wiping me
out. Narrower profile would be nice, especially in wrecks:
the new steering hardware will be protected by small cages
TIG-welded to the seat frame.

I've always been a trifle uneasy about cables... they appear to
offer an easier design solution that's nicely tweakable, but
are quite limiting structurally. The system has to be
perfectly aligned for them to work properly, and is generally
non-deterministic. But the Infinity did feel pretty good to
ride (Maggie had one during our trip down the west coast).

I guess the real test of the new steering geometry is to just
try it. I know the human interface issues will be much
improved (just having the thumb free to wander over a small
panel and reducing internal tendon friction by removing the
wrist twist make a huge difference in output data rate). I'll
report on what happens... the mechanical design is done and my
machinist and I are chasing parts....

>From Michael Johnston at Lehman Brothers:

You wouldn't happen to have a digitized raster image of
BEHEMOTH just laying around on your Sparc would you? In my
minds eye I simply can't imagine just what a 12 foot long,
self-sufficient, mobile communications bike would look like!
By the way, I applaud your decision to go with the CellBlazer
on the project. I infer from your latest issue that you are
relatively new to the net. If you're going to be doing heavy
Unix telecomm (or wireless SLIP for that matter) a CellBlazer
is the only way to go.

Michael...

No GIF files yet, but that's a good idea! Maybe I'll hear
from someone who has the facilities here at Sun to make that
happen <hint, hint>.

(NOTE to readers: in subsequent correspondence, Michael
suggested that I post my archives of road stories -- along with
new ones and other files -- via 'netlib' directly from the
unixycle. This will allow anyone interested to access anything
in the library via email... without having to FTP. Ah,
technology....)

Solar panels and power management are popular topics this week, and
the following two letters are responsible for the article that follows:

>From Joe Reed N9JR...

I am interested in your solar power generation system. I would
be interested in knowing how you handle widely changing light
situations and how you generate power on the bike. Spare
nothing: power consumption calculations, estimated generator
potential, design characteristics, empirical evidence. Plus
those things you have discovered and what you would suggest as
improvements.

>From Nicholas Schectman at Harvard...

I've been getting regular reposts of your Nomadness journal and
am wondering about the solar cells you mentioned in #1. You
mentioned wattage (82, I think), but could you provide me with
other info -- cost, weight, square footage, and supplier name
particularly. I have several applications in mind that could
use lightweight (footage is probably less important) power: the
most realistic (if the cells can be got in small doses) is
recharging of the batteries I use for my bike lights now, but
I'm also interested in running computers off solar, if it
doesn't weigh too much.

Solar Power and Battery Babysitting


This is a critically important part of BEHEMOTH -- the primary
power source for everything except the wheels. (Actually, they
are solar-powered too, if you want to get philosophical about
it... I am part of the food chain, after all...)

From the very beginning of this adventure back in 1983, I have
depended on photovoltaics. The original Winnebiko carried a
small 5-watt Solarex panel that charged a 4 amp-hour SAFT NiCad
pack -- about right for the Model 100 laptop, UNGO box, CB, and
basic lights. The Winnebiko 2, on the road from 1986-88, had a
pair of 10-watt panels (a lighter, newer Solarex design) and a
pair of the same NiCads, later replaced with 10 amp-hours of
Gates lead-acids to simplify management. There were
correspondingly more loads, of course, and the batteries were
attached to two swappable buses to provide redundancy and
improved noise isolation. And the new system is up to 82 watts
of PV's, with 49 amp-hours of main system batteries as well as
a few others scattered here and there as required by
particularly picky subsystems, all managed by FORTH tasks
linked to extensive data collection and power-steering logic.
Ah, bike parts.

Let's see if we can do this without graphics. First, the big
picture: there are three 15 amp-hour Sonnenschein Dryfit A200
series batteries (12 pounds each <grimace>) aboard BEHEMOTH,
two in the WASU (wheeled auxiliary storage unit) and one in the
RUMP. Electrically, they appear as one big battery, and some
switching logic at the trailer-disconnect header lets the bike
power bus continue uninterrupted if I go somewhere without my
WASU. This main battery has four charge sources:

The 72-watt photovoltaic array that is the trailer lid,
made up of four Solarex MSX-18 modules (each is about
17x19" overall, with 14x18" active area). Parallelled,
these collectively produce about 4.8 amps into the
12-volt battery in full sun, and are simply passed
through a Schottky diode into the charge bus. (Solarex
is at 301-948-0202.)

A 10-amp line-operated switching supply from Resonant
Power Technology (408-982-0200), likewise
diode-isolated. This efficient transformerless unit is
only 1.5x3x6" and has a jumper for 110 or 220 volt
input.

The regenerative braking controller, still under
construction, based on a .5-horsepower 3-phase
Semifusion variable-reluctance motor-generator that is
the hub of the new front wheel. A dedicated
microprocessor controls this, and will extract power
from the bike's momentum as a function of right-hand
brake lever compression up to the point at which the
hydraulics engage. (Don't email me for details on
this... let me get it working first!)

An external cable intended to plug into the cigarette
lighter of a motor vehicle, to let me "jump start" on
cloudy days away from power lines when I'm not moving.

Battery management takes place in two layers. The first works
whether processors are alive or not, since basing the health of
such a fundamental system upon working software is dangerous
indeed. This is in transition (I'm currently testing competing
products), but here's the basic idea: a basic off-the-shelf
solar charge controller intervenes when it thinks the batteries
are full and does something to divert the incoming power. My
first pass was with a pair of Sonnenschein SR-50 regulators
(203-271-0091), matched to the batteries and thermally linked
to them via a thermistor. The concept is simple: terminal
voltage reaches 2.3 volts/cell plus/minus tempco effect, and
the two-terminal unit gets hot, shunting excess power into its
finned radiator.

Despite the apparent waste of this approach, it makes sense,
and I integrated them into a larger system that uses
hall-effect current sensors to monitor total charge current,
total load current, and current discarded by the regulators.
This allows the processor, if alive, to notice that power is
being tossed and switch on an optional load, like the Peltier
refrigerator. But I ran into a problem -- the SR-50 is a 50
watt unit, so I had to parallel two of them. No two things
electronic are ever perfectly matched, so in full sun at full
charge, one would get hot and go into thermal shutdown, the
next would quickly follow suit, then the batteries would take
all the abuse of overcharge. No good.

Last week I installed a new ASC unit from Specialty Concepts
(818-998-5238). This is designed to intelligently track
battery level, use pulse charging for increased efficiency, and
protect the battery against overcharge by safely shorting the
solar panels (it is a 4-terminal device). The concept and
execution are good and it works, but I objected to the 10mA or
so of "dark current" that it drew from the battery when no
charging was taking place. I isolated it with a schottky
diode, and since its sense line was no longer on the big
"capacitor" of the battery, it went into an interesting 2.2 kHz
oscillation that still seemed to charge effectively but no
longer let me adjust the setpoint to anything predictable.
(There was also some noise on the power bus that could be heard
in the HF rig.)

So now we're back to square one -- an obvious approach is to
let the trailer-control processor simply do what it wants to do
anyway: disconnect the charge sources with big FETs whenever
the batteries are full (adding hysteresis to keep oscillation
under control). But for simplicity and reliability, I'm still
seeking a standalone dumb controller that can do the job even
when computers are down, probably a larger version of the
original shunt regulator. <sigh> Nothing is ever trivial.

By the way, the choice of solar panels was a deliberate one.
There are many to choose from, from heavy glass-covered units
ideal for permanent installations to the flexible and
much-publicized Sovonics flexible amorphous models. The former
are too bulky; the latter are too inefficient (and amorphous
panels degrade at the rate of about 10-15% per year for the
first 2-3 years of service, yielding a net output per unit area
of about half that of silicon). Of course, dollars/watt is a
different story entirely, but the bike is more like the space
program than a homestead... I want the best performance
available, and hang the expense (well, there are
Gallium-Arsenide space-grade cells that run about 22%
efficient, but they are VERY expensive). The solution was the
Solarex MSX series, sold heavily in the marine market and
robust enough to be walked on if laminated into a boat deck.
Backing is aluminum, and the silicon semicrystalline chips are
sealed in Tedlar -- overall thickness about .1 inch. They have
no frame -- just four grommeted holes for mounting. I'm not
sure of prices, but Real Goods carries them retail at $139 (10
watts), $239 (18 watts), or $299 (40 watts). If there seems to
be a major nonlinearity in those prices, you're right --
contact them for info at 707-468-9214 (you need their catalog
anyway).

Incidentally, solar panel packaging on a bicycle is not
trivial. Any amount of shading (over a few percent) will knock
the output to zero -- I saw one bicycle at the Solar Expo and
Rally in Willits, CA that had a small panel mounted
horizontally on the rear rack, almost always shaded at least
30% by seat and rider! Keeping them horizontal is OK -- output
falls off sinusoidally with the sun's angle, so steering them
for optimum performance costs you more in aerodymic drag and
mechanical complexity than it buys you in power. It is good to
keep them cool... the worst installation example of all is
something I must admit with embarrassment from the Winnebiko II
epoch: one of the 10-watt panels was the top surface of my
electronics bay... under a clear Zzipper fairing! The
greenhouse effect, particularly when the bike was stopped,
could quickly elevate the panel -- and the electronics within
-- to 140 degrees F.

The solar trailer lid hinges on one side, using Hartwell
quick-release hinges (714-993-2752) and a Southco E3
vise-action latch (215-459-4000). A cannibalized SLIK tripod
leg swings down and lets me park the panel at any angle when
stopped; and the whole assembly can be removed and cabled to
the trailer via an extension cord when I'm camped and the bike
is snug inside the porta-condo.

Sharp-eyed readers will have noticed that I mentioned 82 watts
of solar power, then talked about the quartet of 18-watt
modules on the trailer. There is an additional 10-watt module
built into the lid of a Zero Halliburton 103X aluminum case,
grafted brilliantly to the curved surface by metal-wizard Ron
Covell of Covell Specialty Fabrications (408-438-4559). This
is the detachable manpack that contains the laptop, RF
business-band packet data link to the bike, full-duplex VHF
intercom, security components, and so on. I like it to be an
autonomous unit, so it has its own 4 amp-hour battery and local
management.

I also mentioned other batteries... a quick look at the power
distribution scheme might be useful. Generally, the 12-volt
bus is distributed everywhere on the bike and spot-regulated
locally as needed (in most cases by a little Maxim MAX638-based
board designed by Dave Wright). This is much more efficient,
quiet, controllable, and fault-tolerant than having centralized
DC supplies, and it simplifies dynamic load-shedding when some
subsystems are not required.

In the case of some units, however, like the Macintosh
Portable, the manufacturer has already done an excellent
power-management job that would only be thwarted by my
efforts. In these situations, I give the unit what it expects
-- its own battery (the Mac uses a custom drop-in 6-volt
lead-acid pack). The main bus then simply serves as a charge
source through a matched DC-to-DC converter.

In a similar vein, there is also a charging station for all the
little stuff -- the 9.6-volt Makita NiCads (I carry a drill and
flashlight that uses them), up to 8 AAs at a time, and so on.

Finally, there is the maintenance issue. Via the Microswitch
Hall-effect sensors (model CSLA1CH, very nice), there are A-D
converters on the 68HC11 machines that can monitor all relevant
currents and voltages -- plus little Acculex micropower LCD
digital panel meters and associated thumbwheel switches in
console, trailer, and manpack. These allow low-level debugging
without exploratory surgery if nothing seems to work. (Acculex
is at 508-880-3660.)

As you can see from all this, power is one of the essential
infrastructures of BEHEMOTH, every bit as important as the
frame and gearing. The massive amount of apparent overhead
yields a robust and dependable substrate that allows new
subsystems to be added relatively easily, just by setting
device addresses for power switching, serial I/O, audio, and so
on. I'll keep you posted as some of the unimplemented
components of the power management system take shape.

The Brain Interface Unit (BIU)

(first published in Nomadness, issue #9, Fall 1990)


On the road, BEHEMOTH’s bio-controller is always embedded in its modified Bell Tourlite shock-isolation shell, interfaced through visual, aural, and kinesthetic channels to on-board silicon-based systems.  I’d like to give you a brief overview of BIU functionality...

Naturally, every effort has been made to maximize communication bandwidth with the neuron-based system inside the flesh-shrouded head assembly.  A 720 X 280-pixel display presents an apparent graphic overlay upon the system’s binocular view of the world, spectrally peaked at 720 nanometers to minimize any ambiguity with reality and adjustable in apparent focus to minimize attention-switching stress.  A second visual sub-window is provided by a circular optical reflector mounted on the solar attenuation shield, giving the controller a steerable view of conditions aft.  Optional visual attenuation filters can be installed under conditions of high solar flux, softening specular reflections while diverting airflow-borne particulates from the moist and delicate components of the image-acquisition optics.

Both of the rider’s aural channels are coupled to transducers that allow reception of synthesized human language, long-range bidirectional RF communication with others of the same species, alert messages, or any of a number of laser-extracted cross-interleaved Reed-Solomon digitized stereophonic wavefronts selected for relaxation, stimulation, motivation, or subjective time-compression purposes.  Note that these transducers are of limited bandwidth, but can be augmented by miniature units inserted directly into the auditory canals, or alternatively by high-power acoustical drivers located behind the entire brain packaging system.  Wetware-initiated lexical utterances are converted into analog data by a boom-mounted input transducer, and are coupled through the audio network to speech recognition, recording, or communication subsystems as required.

Due to the human visual system’s insensitivity to infrared and other useful wavelengths, the BIU incorporates powerful parabolically-focused light transmitters, with two different degrees of luminance and collimation to accommodate varying conditions.  This has been proven more effective than constraining the beam’s axis to that of the substrate vehicle, since the bio-system is capable of quickly adjusting the azimuth and elevation of the entire head assembly to center the region of interest in its visual frame of reference (not necessarily co-axial with the current physical trajectory).  Whenever the system is traversing a region of the planet that is devoid of insolation, reflections of these beams from landscape features and signage allow real-time decision-based navigation at normal velocities.  We considered reducing power requirements by overlaying an image-intensification system upon the visual field, but this is not an effective solution... it is highly beneficial for autonomous wetware systems piloting petroleum-based land vehicles to recognize the presence of BEHEMOTH and take appropriate evasive action.

The ability of the bio-system to track objects of interest through precise 3-axis positioning of the head assembly enables an additional level of interface with the on-board computer network.  Three 40 kHz ultrasonic receivers positioned on the BIU’s crown and temples receive a reference beam transmitted from the console.  Pitch and yaw angles are derived from raw phase and doppler information, and are used by a dedicated processor to determine precise head pointing angle.  These data, in quadrature form, are converted to conventional ADB events and passed to the Mac, yielding an apparent link between the rider’s nares and the on-screen cursor.  All mouse pointing is done with gross angular BIU movement; clicking and dragging are accomplished via handlebar contact closures antipodal to the data-entry keys associated with the user’s phalanges.

The BIU is designed to cushion the relatively delicate host organism upon occurrence of rapid deceleration associated with impact.  Should the human system separate from BEHEMOTH and become launched upon a divergent ballistic trajectory, the twin coiled cables carrying all interface lines will achieve full extension, actuating lanyard-release connectors.  This is designed to prevent abrupt cervical misalignment (or separation) in high-velocity crisis situations.

Biophysical temperature rise resulting from the accumulated losses of propulsion workload (exacerbated by the low thermal conductivity of the shock-isolating foam shell, especially under conditions of elevated ambient) can be controlled through a fluid heat exchanger closely coupled to the scalp and thermally cycled with an insulated reservoir of aquatic phase-change nodules via a manually-activated peristaltic pump.  Bio-system hydration is managed via a small bite valve that can be inserted into the rider’s speech output device (which doubles as the input port of the alimentary tract and auxiliary oxygen-uptake unit).

Since the osseocarnisanguineoviscericartilaginonervomedullary system is essentially dependent upon fluid-evaporative cooling involving a large percentage of its epidermal surface (despite significant augmentation by the cranial heat-exchanger), there is potential for heavy accumulation of concentrated saline exudate within the crushable BIU interface layer.  This is reduced through an absorptive accumulator that can be manually cleared, as well as a circumferential fluid-removal channel that carries waste coolant back to the occipital region and thence into an overflow tube terminating at the first thoracic vertebra.  These measures insure a minimum of irritation to the delicate ocular membranes under heavy load (the wetware information system, though only dissipating about 10 watts, is unfortunately dependent upon the same metabolic processes that support the bio-engine’s fuel, waste, and heat management facilities).

In short, the BIU is the key interface link between BEHEMOTH and all aspects of its biological host organism.  It provides crash safety, cooling, hydration, sweat removal, visual graphics display, luminance attenuation, communication and entertainment audio, a voice control channel, a view of the road behind, a steerable light source, and a mechanism for hands-free mouse control.

And I never ride anywhere without it.