Intel Engine Control Overview

[tom cloud]

Intel has some interesting data on EFI on its web site.  The following
was taken from: http://www.intel.com/pressroom/archive/releases/engback.htm

It's a lot of stuff -- I hope it doesn't cause anyone any problems.

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Engine Control Overview=20

Press Backgrounder December 1995=20

B.C.--Before Microcontrollers

It was probably inevitable, the application of computer technology to
automobiles, and skyrocketing fuel prices due to the energy crisis certainly
accelerated the process. But early engine controls were far from the
sophisticated digital devices we use to day.=20

Electronic engine control first came to light in 1978 in what was called a
"closed loop" carburetor. It was a response to the oil crisis and promised
marginally better fuel economy. At the same time, national concern over
airborne pollutants propelled inv estigation into the origins of automotive
exhaust components, how pollutants were formed, and how they could be=
 abated.=20

Why electronic control?

Gasoline-powered Otto cycle engines are simple. Combine measured amounts of
air and fuel in a confined space and ignite them. The pressure of expanding
gasses forces a piston to move. This motion is translated into rotational
movement. Like all simple things, there's more than meets the eye.=20

In the 70's, engines relied on mechanically generated signals to ignite the
fuel/air mixture. Electrical energy from a battery was stepped up from 12
volts to many thousand volts by a coil. A mechanical "distributor" selected
the appropriate spark plug and sent a signal along a wire. That selection
"window" was wide, the ignition signal (spark) could be initiated any time
within many
degrees of rotation as a "rotor" contacted mechanical switch points inside
the distributor.=20

Science knew that the outcome of combustion--both power and pollutants--was
greatly affected by how precisely the fuel/air mixture approached
theoretical perfection and when the ignition event took place. To get clean
air, fuel had to be precisely mixed i n a "stoichiometric" 14.7:1 ratio. The
mixture had to be ignited at a precise instant that varied with load, speed,=
 and
other factors. Mechanical devices could not achieve the required precision
and automakers soon approached Intel, a manufacturer of mic rocomputers and
microcontrollers. (A microcomputer chip with a single preprogrammed task is
referred to as a microcontroller.)=20

Early discussions centered on sensor data~ what information an engine
microcontroller would require. Critical needs included the rotational
position of both crankshaft and camshaft, and air flow. Throttle position
and rate of throttle position change (the transmission wants to know when
you need to accelerate quickly) were needed, too.=20

Rotation sensors i.e, crankshaft, camshaft, and ABS sensors at the wheels
utilize a wide variety of technologies. Optical sensors may use infrared
Light Emitting Diodes to peer through a slotted wheel. Other sensor designs
interpret the rise and fall of magnetic energy as a metallic part approaches
and departs. Interestingly, many very precise sensors receive only 4 signals
per 360~ of rotation--exact position is calculated mathematically,
predicting not only position, but whether the engine is accelerat ing or
decelerating. This accuracy allows the fuel/air mixture to be ignited at a
precisely selected moment appropriate for engine power and emissions=
 control.=20

Other data signals are critical to powertrain control. The microcontroller
has to know temperatures in the engine's water cooling system along with oil
temperature and transmission temperature. Fuel injection requires knowing
atmospheric density and how quickly air is being drawn into the intake
manifold. Air temperature affects air density. Hydraulic pressure
information is sent to
the microcontroller by automatic transmissions, as are battery voltage, road
speed, and oil pressure.=20

Every signal adds calculation complexity as it increases the precision of
control.=20

Within the last five years engine microcontrollers have also been required
to determine shift points as the industry installed electronically
controlled (vs. hydraulic/mechanical) automatic transmissions. The precise
management provided by digital control means every automatic transmission
will soon be under numeric control.=20

As engine control advances, so does data complexity. Oxygen sensors enabled
controllers to accurately mix air and fuel based on combustion results. Now,
a second oxygen sensor placed down stream from the catalytic converter
infers the state of the catalyt ic converter (e.g. converters work best when
hot; they suffer contaminant damage, even aging.)=20

At one time it was thought that some kind of sensor would be added to each
cylinder to monitor every combustion event. This would have added enormous
cost and complexity to engines. Instead, by increasing the power of
software--placing added burdens on th e engine computer/controller--events
can be inferred or predicted. This increase in computational power places
great demands on microcontroller performance.=20

Computer chip families or "architectures" may be understood by an analogy to
a subdivision. Every house may look different, yet it is built from common
components. And the core structure--placement of furnace, water and
sewer--may be identical in every bu ilding. Computer chips are built the
same way with a core framework embellished by appropriate structural
add-ons.  Consideration is given to growth (both in raw processing power and
memory) and additional input (more sensor data links.) So a microcontroll er
can add more memory or calculation power up to its architecture's limit,
just as a growing family can add
rooms or central air conditioning.=20

Into the 90s. Power and Memory.

If controlling what happens in an engine and automatic transmission were not
sufficient challenges, a greater one has emerged from legislation.
Specifically, On Board Diagnostics II (second generation) laws. These
require monitoring automotive systems th at affect emissions. Not only does
your cars' engine control unit have to "watch" what goes on and record
troubles for
service technicians as they happen, OBD II rules require the prediction of
deterioration of the following: catalytic converter, fuel
de livery and evaporative emissions systems, crankshaft and camshaft
position sensors, oxygen sensors, manifold air
temperature sensor, ignition system and others.=20

Let's look at the most difficult problem, ignition misfire.=20

A four-cylinder engine cruising on the freeway at 65 mph revolves at
approximately 3,200 revolutions per minute or 6400 spark events per minute.
Because of moisture, voltage drop, or a variety of other factors, some
misfire is inevitable. The engine micro controller monitors combustion and
should, for instance, 6 of 20 sparks in a row fail in any one cylinder, the
engine
controller must notify the driver "SERVICE ENGINE SOON." But what if you
splashed through a deep puddle and a damp wire caused a temporar y misfire?=
=20

Sophisticated algorithms examine error data and query whether the event is
recurring. If it was an isolated incident, as in our damp spark plug wire
example above, the check engine light is extinguished.=20

This benefits the consumer. When a car arrives for service, modern
computer-powered diagnostic equipment can directly interrogate the on-board
microcontroller and elicit a specific response. This could enable the
mechanic to go directly to, for instance, spark plug number 4 and begin=
 repair.=20

This sophisticated diagnostic power requires roughly the same computational
capability as the engine controller itself.=20

Because of increasing complexity, responsibilities, and the sheer number of
calculations, engine microcontrollers need increased power to avoid being
overwhelmed. Just as desktop computers evolved from early 8088 PC Jr.
machines into today's Pentium=AE processor powered models, so have engine
microcontrollers changed.=20

The latest generation of microcontrollers, like Intel's 83C196EA, exemplify
this vastly improved processing power and communications ability.=20

Up to Date Data Collection

Microcontrollers utilize digital signals. Sensor data (voltage, temperature,
linear and rotational velocities, etc.) must be converted from continuous or
analog information into the digital form required by microcontrollers. This
Analog-to-Digital convers ion is typically performed within the
microcontroller.=20

Another critical need is the ability to capture and compare events as they
happen. And high-speed input and output channels transport data to the
microcontroller for action. The microprocessor core itself needs raw power
and speed as it executes the complex instruction codes called algorithms.=20

Once sensors, algorithms and the microprocessor core have done their work,
control signals are sent out to tell the engine what to do. High-speed
channels specify when and how long to fire spark plugs, when and how long to
send fuel through the injectors , or when to shift to a different gear. And
there is a need to query sensors for updated data in return.=20

Intel's new 83C196EA microcontroller harmonizes with modern engine control
needs. It has 16 Analog-to-Digital converter channels built in. Its new
higher speed core zips along twice as fast--32 MHz vs. 16 MHz--as its
predecessor. This kind of speed is optimum for power train control,
particularly its high-speed I/O for controlling electronic transmissions.
The family features 17 event capture-and-compare channels and eight
capture-only channels for a total of 25 high-speed Input/Output channels.=20

Intel's history in engine control electronics is lengthy, from the first
1983 Ford EEC-IV based on the 8061 microcontroller to today's modern 8065
chip set, also known as the EEC-V. Today, Ford is still using the 8065 in
many of their new vehicles produced through the start of the next decade.
The 16-bit architectures, such as the 8065 and MCS=AE 96 controllers, have
been widely accepted in Europe and the U.S in ABS, engine control, and
networking applications. From the introduction of the 8061, Intel has
continued to provide more innovative and highly integrated microcontrollers
in order to help their customers with evolving powertrain applications.
Specifically, the 83C196EA doubles the performance of our existing
microcontrollers while adding more functionality. The 83C196EA will provide
designers with lower development costs and time-to-market.