ELECTRONIC

CONTROL UNIT

By Apuntar, Rench Juben & Anonuevo, Allan Cristopher

 OPERATING CONDITIONS
The control unit is subjected to very high demands with respect to:

Extreme ambient
temperatures Extreme The effects of
(in normal vehicle operation temperature moisture and
from changes • Mechanical
–40 to +60...+125 °C) • Indirect stress such as
materials and vibration
supplies from the engine
(oil, fuel etc.)

• The control unit must operate reliably when the vehicle is started with a weak battery (e.g. cold start)
and with high charge voltages (vehicle electrical system fluctuations).

• Other requirements arise from the need for EMC (ElectroMagnetic Compatibility)
DESIGN
housing of plastic or metal

multiple plugs (control unit to the

sensors, actuators and electrical power
supply)

high-performance driver circuits

majority of the electrical components

are of the surface-mounted device
technology type
 DATA PROCESSING
Analog Input Signals
Digital Input Signals
Pulse-type Input Signals
GN A L
T SI
INPU Protective circuits limit the voltages of input signals to
A levels suitable for processing. Filters separate the useful

I O N I NG signal from most interference signals.

T
L C ONDI
SIGNA
B The control unit program supports generation of the
output signals used to control the actuators.
C ESS I NG
AL P R O
SIGN
C
Switching Signals
PWM Signals
S I G N ALS
OUTPUT
D
 DIGITAL PROCESSING

In order to be able to support the microcontroller in its

work, the peripheral components must communicate
ION with it. This takes place using an address/data bus
NICAT
MM U which, The microcontroller outputs the RAM address
N AL C O
N I T-I N T ER whose contents are to be read (for example) via the
RO L U
C ON T address bus.
E

The Flash-EPROM’s complete memory area can be

programmed at the end of production with the program
M IN G and the variant-specific data record (this is the so-called
G R AM
EOL P RO End-of-Line, or EoL, programming).

F
 PERFORMANCE OF ELECTRONIC CONTROL
UNITS
Entire Engine Microcontrollers (Intel
Management Sysytem 8051 to 80515 family)
taken over by the universally Additional I/O facilities for timer-
applicable semiconductor controlled signals and an
microchip. integrated analog-digital
converter at the end of the
1980’s

First Gasoline injection Complex Engine- Development of

System Management Systems Electronic Control Unit
analog – with limited flexibility They controlled not only fuel
in the implementation of control injection but also the ignition
functions. These functions were system including knock control,
constrained by the hardware. exhaust-gas recirculation and a
whole variety of other systems.
 PERFORMANCE OF ELECTRONIC CONTROL
UNITS
Entire Engine Microcontrollers (Intel
Management Sysytem 8051 to 80515 family)
taken over by the universally Additional I/O facilities for timer-
applicable semiconductor controlled signals and an
microchip. integrated analog-digital
converter at the end of the
1980’s

First Gasoline injection Complex Engine- Development of

System Management Systems Electronic Control Unit
analog – with limited flexibility They controlled not only fuel
in the implementation of control injection but also the ignition
functions. These functions were system including knock control,
constrained by the hardware. exhaust-gas recirculation and a
whole variety of other systems.
Digital Modules in the Control Unit

Microcontroller - STRUCTURE

• Central processing unit

• Input and output
(CPU): •
devices (I/O, Program
Input/Out- memory
put),
 Digital modules in the
control unit • A clock
generator
Microcontroller - STURCTURE (oscillator)

• Data memory
• The bus
system

• Logic circuits
Digital Modules in the Control Unit
Microcontroller - Programming
 Semiconductor Memories
Memories are used to
store large volumes
(I/O data, statuses, intermediate results
of data involving frequent and rapid reading
s en ting
pre and writing)
gn als re
ig it al si
D
A (usually permanently stored) & (permanently
n st a n ts
d e& Co stored)
co
Prog ram
B
(Writing)

e c or din g
R
C
ion & (actual storage) & (reading) of information
r ete nt
ent
Perman nd retrieval
a
D Location
Semiconductor Memories
 Semiconductor Memories
Random-access memory (RAM)
- short-term memory that allows direct access to any storage location.
Dynamic RAM
Static RAM (SRAM) (DRAM)

Static RAMs use bistable switching Unlike SRAM, the information is

elements as the data storage cells. stored as an electrical charge in the
SRAM is therefore volatile memory. gate capacity of a CMOS transistor
in dynamic RAM (DRAM).
 Semiconductor Memories
Read-only Memory
- Read-only memory (ROM) is permanent-storage memory that allows any memory location to
be accessed directly but – as the name indicates – allows the information only to be read and not
modified.

- A ROM is nonvolatile memory, i.e. the information it contains is retained even when the
operating voltage is switched off.

- It is usually used to store program code (control programs) and fixed data (function tables,
encoding rules, engine characteristic data maps) that need to be retrievable at any time.
 Semiconductor Memories
Erasable ROM
- There are also ROMs whose contents can be erased and reprogrammed as outlined below.

EEPROM (Electrical
EPROM)

EPROM (Erasable Flash EEPROM

PROM)

The EEPROM (also known as

E2PROM) can be electrically erased
and reprogrammed. Every storage
cell of an EEPROM be individually
overwritten.
This type of erasable read-only memory A more sophisticated variant of the
can have its contents completely wiped EPROM and EEPROM is flash EEPROM.
by irradiation with UV light and can then
be reprogrammed using a programming
device.
 Control unit software
Real-time capability
- One of the requirements on electronic systems is real-time capability.

- This means that control procedures must react to input signals within an extremely short time.

- The complexity of an electronic system therefore makes extremely high demands of the
software that is developed.
 Control unit software

Software structure
The microcontroller in the
control unit executes
commands sequentially. The
command code is obtained
from the program memory.
 Control unit software
Interrupt control
- As soon as an event occurs that requires an extremely rapid response (e.g. speed sensor pulse),
the program that is currently running must be interrupted. This can be done using the
microcontroller’s interrupt control facility.

- Events can trigger a program execution interrupt, where-upon the program jumps and
executes the “interrupt routine”.

- An interrupt can be triggered by an external signal.

 Control unit software

Tooth interrupt
The crankshaft is equipped
with a pulse wheel (Fig. 2a)
that has a certain number
of teeth on its
circumference.
 Control unit software

Tooth interrupt
Example: crankshaft
position calculation The
engine-management system
(Motronic for gasoline
engines, EDC for diesel
engines) must know the
crankshaft position at any
given point in time.
 Control unit software
Combustion-synchronous interrupt
- As soon as an event occurs that requires an extremely rapid response (e.g. speed sensor pulse),
the program that is currently running must be interrupted. This can be done using the
microcontroller’s interrupt control facility.

- Events can trigger a program execution interrupt, where-upon the program jumps and
executes the “interrupt routine”.

- An interrupt can be triggered by an external signal.

 Control unit software
Combustion-synchronous interrupt
Some calculations must be performed for every combustion cycle.

For example, the ignition angle

and the injection have to be This interrupt takes place after
recalculated synchronously with every 30 teeth (ignition interval)
combustion for each cylinder. for a four- cylinder engine, and
after every 20 teeth for a six
cylinder engine.

The program does this by

branching to the
“synchronization program”
after certain teeth (Fig. 4).
 Control unit software
Ignition interrupt

Time frame

The ignition output takes place

within a certain crankshaft
range, depending on the value
from the ignition map.

Since the specified ignition angle

has to be adhered to exactly, the
ignition output is controlled by
an interrupt.
 Control unit software
Time frame
- Many control algorithms have to run within a certain time frame.
- Lambda control, for example, has to be processed within a fixed time frame (e.g. 10 ms) so
that the correcting variables are calculated quickly enough.
 Control unit software
Background program
- All other activities that do not run in an interrupt routine or a time frame are processed in the
background program.

- At fast engine speeds, the synchronization program and the tooth interrupt are called
frequently, leaving little CPU time for the background program.
 Software Development
Software Development
- A study of the current series projects together with the use of development capacities
demonstrate that approximately 60% of the time spent on ECU development has to be devoted to
creating the necessary software.

Development Process
- A depiction of the development steps in then form of a V-model (Figure 1) serves as the basis
for all software-development activities.

Quality Assessment
- Quality assessments are scheduled at defined points of the development process (Figure 2) for
the purpose of process monitoring.
 Software Development

This model is used to detail the

process steps which facilitate
implementation within a
product-development
department.
Software Development
THANK YOU
INPUT SIGNALS
Analog Input Signals Digital Input Signals Pulse-type Input Signals

Analog signals are continuous values A digital signal is a signal that The pulse-shaped input signals from
which means they can be represents data as a sequence of inductive-type sensors containing
an infinite number of different voltages. discrete values. information on rotational speed and
  reference mark are conditioned in their
Intake-air mass, battery voltage, intake- Digital input signals only have two own control unit stage.
manifold and boost pressure, coolant states. They are either “high” or “low”
and intake-air temperature. (logical 1 and logical 0 respectively).

The maximum resolution of these on/off switching signals, or digital

analog signals is 5 mV sensor signals such as the rotational-
speed pulses from a Hall generator or a
magnetoresistive sensor.
OUTPUT SIGNALS
Switching Signals PWM Signals

Actuators can be switched on and off Digital output signals can be in the form
using the switching signals (e.g. motor of PWM (Pulse-Width Modulated)
fans). signals. These are constant-frequency
rectangular signals with variable on-
times.