Increasing Reliability and Availability for

Increasing Reliability and Availability
for Automotive Embedded Devices by Enhanced Wiring
Diagnosis
Overview
Introduction
Potential failure situations and their detection
Deficits of previously existing concepts
Components of the improved solution
Summary
Authors:
Ralf Förster, Annette Kempf, Michael Niemetz, Konstantin Thiveos, Gerhard Wirrer, Wolfgang Wolfarth
Continental Automotive, Engine Systems, Regensburg
2 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Introduction: The combustion engine, 15 years ago
Injectors
Ignition Coil
Camshaft
Position Sensor
3-Way Catalyst
Active Crankshaft
Position Sensor
3 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Engine Coolant
Temperature
Sensor
Lean NOx
Trap Catalyst
Introduction: The combustion engine, today
Air Cleaner Box
Mass Air Flow
Sensor with
Integrated
Temp. Sensor
Electronic
Throttle Control
Exhaust Gas
Recirculation
Valve (EGR)
Composite
Manifold
Manifold
Absolute Pressure
Sensor
Piezo Direct
Injection Piezo
Injector
Ignition Coil
Dual Cont. Var.
Cam Phaser
Camshaft
Position Sensor
Exhaust
Temperature
Sensor
3-Way Catalyst
Lean NOx
Trap Catalyst
High variety
depending on
engine type and
vehicle
configuration.
Active
Carbon
Canister
Canister Purge
Solenoid
Fuel Supply Unit
Large amount of
sensors and
actuators
High Pressure
Fuel Pressure
Fuel Pump with
Sensor
Flow Control Valve
4 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Active Crankshaft
Position Sensor
Knock Sensor
Engine Coolant
Temperature
Sensor
Linear/Binary
O2 Sensor
NOx Sensor
Introduction
The automotive power train electronics has to provide answers for a wide range of challenges:
Physical world
Increasing complexity of the wiring harness
Corrosive environments
Vibration
Large temperature range
Requirements
Legal requirements for continuous monitoring (i.e. detection of environment relevant malfunction)
Mobility requirements (limited operation in case of failures)
Low maintenance and service costs / easy troubleshooting
Safety requirements
The control unit (ECU) needs to be able to perform diagnostics for the wiring of sensors and actuators.
5 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Wiring problems and their detection
Normal Operation (NO)
Vbat
Low Side Driver ECU pins are driving loads connected to battery voltage:
During the off state of the driver, the ECU pin is tied high by the load.
ECU
During the on state of the driver, the ECU pin is pulled to ground by the
driver.
Driver
CEMI
Shortcut to Battery (SB)
Vbat
In the Short circuit to Battery situation, the ECU pin is connected to the
battery voltage directly:
The load can not be activated (both load terminals on battery voltage
potential).
ECU
Driver
The driver suffers from excessive current in case of being activated.
CEMI
The potential of the ECU pin is on battery level in the on and off state of
the driver.
6 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Wiring problems and their detection
In the Short circuit to Ground situation, the ECU pin is directly connected to
ground:
The load can not be de-activated and is permanently on.
The potential of the ECU pin is on ground potential during the on and off
state of the driver.
Open Load (OL)
Vbat
In the Open Load situation, the ECU pin is disconnected:
The load can not be activated (both load terminals on battery voltage
potential).
~
~
ECU
Driver
The potential of the ECU pin is floating in off-state.
CEMI
7 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Wiring problems and their detection
The possible error cases are detected by the driver units by:
Pin potential (voltage) measurement or
Driver current measurement
The detection is based on comparators and data latches, without complex logic.
The result of the diagnosis is typically reported via a two-bit information:
Description
Detectable in Driver
State
Condition
Two-bit diagnosis
information
Short-circuit to
battery
ON
> approx. 2V or
over-current
0
Open Load
OFF
2V - 3V
1
Short-circuit to
ground
OFF
< approx. 2V
2
No problem could be
detected
Any
others
3
8 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Problems with existing approaches: Timing
Timing
Short diagnosis pulses are needed if the driver state is not matching the required state for detection.
The detection is limited to certain ranges of PWM frequencies and duty cycle values.
Timing of diagnosis is difficult to keep in case of serial communication with peripheral devices.
µC has to create the correct timing for the necessary diagnosis pulses.
PWM Duty cycle ranges where valid
diagnosis results can be obtained
depend on:
Size of the EMI capacitor
Digital filters in the driver
component
Frequency of the PWM
Type of diagnosis (SG/OL/SB)
9 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Problems with existing approaches: Validity
Validity
Situations "no error present" and "no error could be detected" must be distinguished.
Validation of diagnosis result requires a huge effort software for considering all the influencing aspects:
Duty cycle values applied during the time frame where the diagnosis was performed.
Timing of the readout of diagnosis information.
Knowledge about hardware parameters (time constants of the schematic and of the digital filters).
For diagnosis of a PWM output this means:
The µC has to know all parameters (time constants of filter and EMI capacitor).
The µC has to track all changes of operation parameters (duty cycle, frequency) between two readouts
of the diagnosis information.
Finally, all this information must be combined to derive the validity of the diagnosis information obtained
from the driver device.
10 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Solution: The Third Bit
ECU
Wiring diagnosis result coded in three bit
Driver
Minimize hardware effort for providing the validity information
Serial Interface
Registers, Inputs, Outputs, Control
Diagnosis
State
Description
0
Reserved
OL
SG
SB
3V
OL
-
-
OC
failure
SG
2V
1
Over current
x
x
OC
SG failure
☺
x
3
OL failure
☺
☺
4
No failure
☺
☺
☺
5
No SB failure
x
x
☺
6
No SG/OL
failure
☺
☺
x
7
No information
x
x
x
11 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
no OC
failure
SG
failure
2
reserved
ISB
OL failure
no OL/SG
failure
5V
R1
Fast Charge
Pulse
Generation
R3
2.5V
R2
Diagnostic
Pulse
Generation
gate driver
shunt
CEMI
Solution: Fast Charge
The fast charge functionality consists of:
ECU
Driver
A low impedance pull-up resistor
Serial Interface
An activation switch for the pull-up resistor
A fast charge pulse generator
Registers, Inputs, Outputs, Control
3V
OL
reserved
OC
failure
SG
This results in:
a reduced time constant to charge the EMI capacitor (important for
OL and SG testing)
2V
no OC
failure
SG
failure
OC
ISB
OL failure
no OL/SG
failure
5V
a minimized leakage current
R1
Fast Charge
Pulse
Generation
Consequences:
R3
2.5V
R2
improved range of valid diagnosis results
Diagnostic
Pulse
Generation
gate driver
improved signal quality due to shorter diagnosis pulses and small
leakage current.
shunt
12 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
CEMI
Solution: Diagnosis Pulse Generator
Timing of the diagnosis pulse is managed autonomously by a pulse
generator triggered by the software.
ECU
Driver
Serial Interface
All necessary actions are coordinated inside the driver component.
Registers, Inputs, Outputs, Control
3V
OL
Consequences:
Optimized timing
reserved
OC
failure
SG
2V
no OC
failure
SG
failure
Reduced bus traffic
OC
ISB
Reduced software effort inside of the µC
OL failure
no OL/SG
failure
5V
R1
Fast Charge
Pulse
Generation
R3
2.5V
R2
Diagnostic
Pulse
Generation
gate driver
shunt
13 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
CEMI
Summary
Introduction of autonomous wiring diagnostics in the driver devices provides:
Improved diagnosis capabilities over a wider range of signal characteristics (duty cycle, frequency)
Less signal disturbance by shorter diagnosis pulses
Reduced bus traffic in case of devices attached via serial interfaces
Enormously reduced software effort in the µC for determining the validity
Reduced dependencies between the µC software and properties of driver circuits enable software
standardization (e.g. Autosar).
Engine management ECUs using drivers designed according the shown concepts are under development
and will arrive in market products soon.
14 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 © Continental AG
Thank you for your attention