[FoRK] the end of M.E.
eugen at leitl.org
Thu Jun 9 13:15:19 PDT 2005
the end of the m.e.?
They call this "convergence." Old lines are changing, or disappearing
altogether. What it's doing under the hood is downright electrifying.
by Peter W. Huber and Mark P. Mills
The turf still divides up quite neatly. The electrical engineers move the
light stuffâelectrons, power, bits, and logic. The mechanical engineers
do the heavy lifting; they move atoms. And, like it or not, the MEs still
control most of the real estate.
Look at our cars. They're made of big heavy things that shake, bounce, and
sway; they're propelled by pistons, shafts, gears, and belts; controlled by
shafts, gears, valves, and hydraulic fluids. All the really important parts
go click-click, bang-bang. The car is a 100 kW (peak) machine. The stuff
that hums instead of clanking, the electric load, peaks at 2 kW.
Mechanical engineers control most of the rest of our energy economy, too.
The United States consumes 100 quadrillion Btus, or quads, of raw thermal
energy every year, in three broad sectorsâelectric power,
transportation, and heatâwith consumption split (roughly) 40-30-30 among
the three. But electric power plants themselves are mainly thermomechanical:
The furnaces, boilers, and turbines themselves consume over half of the
fuel; only about 16 quads worth of mechanical energy actually get to the
shafts that spin the generators that dispatch the gigawatt-hours.
[Image: Komatsu's 930E is a 2,000 kW truck. A 16-cylinder diesel engine drives a
generator that powers electric motors on the wheels.]
It doesn't have to be that way, and pretty soon it won't be. General
Electric's 4,400-horsepower, diesel-electric GEVO-12 locomotive is powered
by an enormous, diesel-fueled engine-driven generator; everything beyond is
electric. Komatsu's 930Eâa monster mining truck with 320-ton
capacityâis propelled by a 2-megawatt Detroit diesel-electric generator.
Everything else, right down to the 12-foot wheels, is driven electrically.
Submarines have been largely all-electric for decades, and the surface ships
now on the Navy's drawing boards are all-electric, from the propeller to the
guns. Thermomechanical engines are still the prime movers on all of these
platforms, but what they move is electricity. An on-board generator powers
an all-electric drivetrain; an electric motor drives the propeller or
Electric drives are taking over because an electrical bus can convey far
more power in much smaller, lighter conduits, and do it far more precisely
and reliably, than even the best designed mechanical drivetrain. Indeed, on
the key metrics of speed and power density, the electrical powertrain is
about five orders of magnitude better. Electricity moves at close to the
speed of light; all thermal and mechanical systems move at the speed of
sound, or slower. It takes 10,000 driveshafts in 10,000 redlining Pontiacs
to convey about as much power (1 gigawatt) as a single power plant
dispatches down a few dozen high-voltage cables. By a very wide margin,
electricity is indeed the fastest and densest form of power that has been
tamed for ubiquitous use.
But precisely because it is so fast and dense, electricity is inherently
difficult to control. Direct-drive electrical systems are fast all right,
but they tend to jitter, overshoot, jerk out of control, and fall off the
edge. The solution, historically, has been to get mechanical againâwrap
the electric coils and magnets around heavy, inertial, and frictional
components to get back to a simple and steady source of mechanical
powerârotating a shaft, sayâwhich can then be channeled through
gears, belts, hydraulic fluids, and other arrays of click-click, bang-bang
logic well before it reaches the final payload. Until recently, direct-drive
electrical moversâsystems in which the power stays electric right down
to the very threshold of payloadâhave remained the exception, not the
Power in Control
But big motors and their electric power supplies can now be built compact
and precise enough to mimic the small muscles of a hand. A key breakthrough
occurred in 1982, when Hans Becke and Carl Wheatley (both at RCA) were
granted a patent for what is now called the insulated gate bipolar
transistor. IGBTs are high-power semiconductor gates. They control kilowatts
almost as efficiently as logic semiconductors control the picowatts that we
Sensors have also become sufficiently small, fast, and accurate to provide
real-time feedback of what's happening at the payload. And cheap
microprocessors are now readily available to make sense of it all, and to
constantly recalculate how much power to dispatch to the drive to make it do
exactly what's needed.
Supplied with a suitably shaped and amplified stream of power, a loudspeaker
vibrates a diaphragm through a Beethoven symphony; do the same with a
hundred kilowatts, and you can run a Pontiac. What's new now is that
inexpensive semiconductors are available to provide the extraordinarily
precise control of very large amounts of electric power, at very low cost,
in very compact controllers.
The sidestick, being tested by Mercedes-Benz, is part of a fully
computer-controlled car handling system of the possibly near future.
Because they move less material in the middle, direct-drive powertrains have
far less inertia and friction; and because they are informed by very fast
sensors controlled by computers they can react much faster to the outside
world. Direct-drive motors can thus reach levels of precision that are
completely unattainable with any conventional technology. With less weight
in the powertrain, and fewer moving parts, direct-drives are also more
robust. Pneumatic and hydraulic fluids leak, turn into molasses when they
get cold, and are easily contaminated. Shafts, belts, and pulleys need
lubricants, and get bent out of shape when they expand or contract. They
corrode and need periodic maintenance. Electric wires don't.
The transformation is already well under way in the car's peripheral
systems. The belts and pulleys that drive water and oil pumps, and radiator
cooling fans, are giving way to electric motors. The best brakes are already
electrohydraulic; all-electric brakes will follow. With electronic
throttles, the gas pedal sends electrical instructions to a microprocessor
that controls the fuel injection system electronically. Drive-by-wire
electric power steering began appearing in production vehicles in 2001.
Passive, reactive, energy-dissipating springs and shock absorbers are being
displaced by an active array of powerful linear motors that move wheels
vertically as needed to maintain traction beneath and a smooth ride above.
And electric actuators will displace the steel camshaft on every valved
engine. Put each valve under precise, direct, digital-electric control,
actuated independently by its own compact electric motorâopen and close
each valve as dictated by current engine temperature, terrain, load, and
countless other variablesâand, in effect, you continuously retune the
engine for peak performance. Belts, shafts, and chains melt away. Everything
shrinks, everything gets lighter, and every aspect of performance
To meet this steadily rising demand for electric power, car manufacturers
are making the transition to a 42-volt grid to replace the existing 14-volt
grid. Lower-voltage wires just can't convey large amounts of power
efficiently. A new 42-volt industry standard emerged recently, and half of
global automobile production will be on a 42-volt platform within the next
decade or so.
Next-generation integrated high-power alternator/starter motors have already
been incorporated in BMWs and Benzes, and in Ford and GM trucks; about half
of all new cars will have them by 2010. These units will supply the car with
abundant, efficiently generated electric power, in a much lighter package,
that will provide a virtually instant engine start as well.
Cheap in the Gearbox
This will set the stage for the last big stepâthe one already taken in
monster trucks: Silicon and electric power will knock out the entire
gearbox, driveshaft, differential, and related hardware; electric drives
power the motors that turn the wheels. Power chips now make it possible to
build high-power motors the size of a coffee can, and prices are dropping
fast. When such motors finally begin driving the wheels, the entire output
of the engine will have to be converted immediately into electricity before
it is distributed, used, or stored throughout the car. It will take
heavy-duty wiring and substantial
silicon drives and electric motors to propel a hybrid-electric sport utility
vehicle down a highway at 70 mphâbut they'll be far smaller than the
steel structures in today's powertrain. Cars will shed many hundreds of
pounds, and every key aspect of performance will improve considerably.
As this process unfolds, the engineering focus will shift inexorably toward
finding the most efficient means of generating electricity on-board. Trains
and monster trucks both use big diesel generators. Hybrid cars on the road
today burn gasoline, but it's the fuel cell that attracts the most attention
from visionaries and critics of the internal combustion engine. Remarkably
elegant in its basic operation, the fuel cell transforms fuel into
electricity in a single step, completely bypassing the furnace, turbine, and
generator. In this scenario, mechanical engineering ultimately surrenders
its last major under-the-hood citadel to chemical engineers.
Much the same transformation is well under way in the factory. The
19th-century factory was powered by a single driveshaft spanning the length
of the building; belts and chains delivered power to each individual work
bay. That primary mechanical driveshaft gave way to electric power long ago,
with motors powering the lathe, drill, or milling machine in each
workstation. But, by and large, the motors still connect to shafts and belts
and compressors. As in the car, mechanical systems still control the last
few meters of the powertrain.
I, Sensitive Robot
The new industrial robots, however, are complex configurations of electric
servo motors; the electric power now runs right to the final threshold of
where the power is needed. Packed with sensors, the robots are now precise,
sensitive, and far more compact than any mechanical alternative. They are
also far more flexibleâthey now can be instantly reconfigured to perform
new tasks through software alone, a dramatic advance over previous systems
that required hours of manual rewiring.
At the same time, high-power lasersâbuilt around another family of
recently developed semiconductorsâare rapidly taking over functions
previously viewed as mechanical. At kilowatt and megawatt power levels,
lasers don't move bits, they move material. They fuse powdered metals into
finished parts, without any machining, cutting, or joining. They supply
ultra-fine heating, soldering, drilling, cutting, and materials processing,
with fantastic improvements in speed, precision, and efficiency. They create
thermal pulses that can blast metals and other materials off a source and
deposit them on a target to create entire new classes of material coatings.
They move ink in printersânot just desktop devices, but also the mammoth
machines used to produce newspapers. They solder optoelectronic chips
without destroying the silicon real estate around them, and they supply
unequaled precision in the bulk processing of workaday materialsâheat
treating, welding, polymer bonding, sintering, soldering, epoxy curing, and
the hardening, abrading, and milling of surfaces.
Delphi has sold millions of its electric power steering units, which
eliminate hoses, pump, and hydraulic fluid.
Mechanical systems can be remarkably cleverâjust look at how a high-end
mechanical watch powers and times the movement of hands around the watch
face. In engines and machines of every description, much of the mechanical
engineering is still devoted to imposing a desired logic on the flow of
power. Until quite recently, EEs themselves relied on at least
semi-mechanical systems to choreograph and order the flow of electricity.
The huge electromechanical switches that phone companies used to route calls
until the 1960s set up circuits by reconfiguring tapestry-like arrays of
small, electromechanical switchesâthousands and thousands of them,
clicking away, day and night. But the advent of the transistorâinvented
by Bell Labsâchanged all that. Semiconductors now choreograph the flow
(or photonic) power through our watches and our phone lines.
Pushing semiconductors up the power curve took 20 years longer than it did
to push them down. But it has now been done. And these fundamentally new
technologies of "digital power" make possible an extraordinary new variety
of compact, affordable, product-assembling, platform-moving, people- moving,
and power-projecting systems that seem to be all but magical. They will
inevitably infiltrate, capture, and transform the capital infrastructure of
our entire energy economyâthe trillions of dollars of hardware that
convert heat into motion, motion into electricity, and ordinary electricity
into highly ordered electron and photon power.
One might say that the age of mechanical engineering was launched by James
Watt's steam engine in 1763, and propelled through its second century by
Nikolaus Otto's 1876 invention of the spark-ignited petroleum engine. We are
now at the dawn of the age of electrical engineering, not because we
recently learned how to generate light-speed electrical power, but because
we have now finally learned how to control it.
Peter W. Huber, a former mechanical engineering instructor at MIT, is a
senior fellow of the Manhattan Institute. Mark P. Mills, a physicist, is a
founding partner of a venture fund, Digital Power Capital. They are
co-authors of The Bottomless Well (Basic Books, 2005) .
Eugen* Leitl <a href="http://leitl.org">leitl</a>
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