
---------------------- 
NOTES FROM THE BIKELAB 
Issue #3 -- 12/30/90
by Steven K. Roberts
----------------------

Copyright (C) 1990 by Steven K. Roberts.  All Rights Reserved.

	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 interface shell, linked 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 (Private
	Eye) 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 complex 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.  Rider-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
	directional parabolic light transmitters, with two different
	degrees of collimation to accommodate varying road conditions.
	This has been proven more effective than constraining the
	beam's axis to that of the bike, since the bio-system is
	capable of rotating the entire head assembly to center the
	region of interest in its visual frame of reference (which is
	not necessarily co-axial with the bike's 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 allow real-time decision-based
	navigation at normal velocities.  A future version will reduce
	power requirements by overlaying an image-intensification
	system upon the visual field, but this is not a standalone
	solution (since it is beneficial for other autonomous wetware
	systems -- especially those 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 head 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 emergency situations.

	Wetware 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 pumped by a pair of remote 50 watt Peltier-effect
	modules.  Continuous bio-system hydration is managed by a
	second fluid loop via a small sip tube to be positioned next to
	the rider's speech output device (which doubles as the input
	port of the alimentary tract and twin oxygen-uptake units).

	Since the osseocarnisanguineoviscericartilaginonervomedullary
	system is essentially dependent upon fluid-evaporative cooling
	(despite significant augmentation by the heat-exchanger), there
	is potential for heavy accumulation of concentrated saline
	exudate within the 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.  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 the
	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.

Closing Notes
-------------

	Long one this time (how did that happen?).  A couple of
	quickies:  first, I told you wrong in issue #2 when I mentioned
	the wattage of the Night-Sun helmet lights -- information here
	suggests that it's 10-watt flood and 25-watt high beam.  The
	company can be reached at 818-790-7749 for more info.

	Also, on sources for high-brightness LED's:  I mentioned H-P;
	the other major vendor in this field is Stanley, based in
	Japan.  Their west-coast rep is AC Interface at 714-858-1866.

	Cheers from the bikelab!!!

		Steven K. Roberts 
		Nomadic Research Labs 
		P.O. Box 2390 
		Santa Cruz, CA 95063

		wordy@bikelab.Sun.com 
		GEnie, MCI, or AOL:  wordy


