Increasing Reliability and Availability for Automotive Embedded Devices by Enhanced Wiring Diagnosis

Increasing Reliability and Availability for Automotive Embedded Devices by Enhanced Wiring Diagnosis

Overview Introduction Potential situations and their detection Deficits of previously eisting 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 Lean NO Trap Catalyst Active Crankshaft Position Sensor Engine Coolant Temperature Sensor 3 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 Continental AG

Introduction: The combustion engine, today Air Cleaner Bo Mass Air Flow Sensor with Integrated Temp. Sensor Electronic Throttle Control Ehaust Gas Recirculation Valve (EGR) Composite Manifold Manifold Absolute Pressure Sensor Piezo Direct Injection Piezo Injector Ignition Coil Dual Cont. Var. Cam Phaser Ehaust Temperature Sensor Camshaft Position Sensor 3-Way Catalyst Lean NO Trap Catalyst Large amount of sensors and actuators Active Carbon Canister High variety depending on engine type and vehicle configuration. Canister Purge Solenoid Fuel Supply Unit High Pressure Fuel Pump with Flow Control Valve Fuel Pressure Sensor Active Crankshaft Position Sensor Knock Sensor Engine Coolant Temperature Sensor Linear/Binary O2 Sensor NO Sensor 4 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 Continental AG

Introduction The automotive power train electronics has to provide answers for a wide range of challenges: Physical world Increasing compleity 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 s) 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 ECU Driver 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. During the on state of the driver, the ECU pin is pulled to ground by the driver. CEMI Shortcut to Battery (SB) Vbat ECU Driver CEMI 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). The driver suffers from ecessive current in case of being activated. 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) ECU Driver CEMI Vbat ~ In the Open Load situation, the ECU pin is disconnected: The load can not be activated (both load terminals on battery voltage potential). The potential of the ECU pin is floating in off-state. 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 comple 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 > appro. 2V or over-current 0 Open Load OFF 2V - 3V 1 Short-circuit to ground OFF < appro. 2V 2 No problem could be detected Any others 3 8 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 Continental AG

Problems with eisting 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 eisting 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 Wiring diagnosis result coded in three bit Minimize hardware effort for providing the validity information ECU Driver Serial Interface Registers, Inputs, Outputs, Control Diagnosis State 0 1 Description Reserved Over current OL - SG - SB - 3V 2V OL SG reserved OC no OC SG 2 SG ISB OC OL no OL/SG 3 OL 5V 4 No Fast Charge Pulse Generation R1 R3 5 No SB 2.5V R2 6 No SG/OL Diagnostic Pulse Generation gate driver 7 No information shunt CEMI 11 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 Continental AG

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 Registers, Inputs, Outputs, Control A fast charge pulse generator 3V OL reserved OC This results in: 2V SG no OC SG a reduced time constant to charge the EMI capacitor (important for OL and SG testing) ISB OC OL no OL/SG a minimized leakage current 5V Consequences: improved range of valid diagnosis results improved signal quality due to shorter diagnosis pulses and small leakage current. Diagnostic Pulse Generation Fast Charge Pulse Generation gate driver 2.5V R1 R2 shunt R3 CEMI 12 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 Continental AG

Solution: Diagnosis Pulse Generator Timing of the diagnosis pulse is managed autonomously by a pulse generator triggered by the software. All necessary actions are coordinated inside the driver component. ECU Driver Serial Interface Registers, Inputs, Outputs, Control Consequences: 3V OL reserved OC Optimized timing Reduced bus traffic Reduced software effort inside of the µc 2V ISB SG OC no OC SG OL no OL/SG 5V Fast Charge Pulse Generation R1 R3 2.5V R2 Diagnostic Pulse Generation gate driver shunt CEMI 13 / Förster, Kempf, Niemetz, Thiveos, Wirrer, Wolfarth / 06/2010 Continental AG

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

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