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Journal Article

Calculation of Failure Detection Probability on Safety Mechanisms of Correlated Sensor Signals According to ISO 26262

Functional safe products conforming to the ISO 26262 standard are getting more important for automotive applications wherein electronic takes more and more response for safety relevant operations. Consequently safety mechanisms are needed and implemented in order to reach defined functional safety targets. To prove their effectiveness diagnostic coverage provides a measurable quantity. A straight forward safety mechanism for sensor systems can be established by redundant signal paths measuring the same physical quantity and subsequently performing an independent output difference-check that decides if the data can be transmitted or an error message shall be sent. This paper focuses on the diagnostic coverage figure calculation of such data correlation-checks for linear sensors which are also shown in ISO 26262 part5:2011 ANNEX D2.10.2.
Technical Paper

Implementing Mixed Criticality Software Integration on Multicore - A Cost Model and the Lessons Learned

The German funded project ARAMiS included work on several demonstrators one of which was a multicore approach on large scale software integration (LSSI) for the automotive domain. Here BMW and Audi intentionally implemented two different integration platforms to gain both experience and real life data on a Hypervisor based concept on one side as well as using only native AUTOSAR-based methods on the other side for later comparison. The idea was to obtain figures on the added overhead both for multicore as well as safety, based on practical work and close-to-production implementations. During implementation and evaluation on one hand there were a lot of valuable lessons learned about multicore in conjunction with safety. On the other hand valuable information was gathered to make it finally possible to set up a cost model for estimation of potential overhead generated by different integration approaches for safety related software functions.
Technical Paper

Non-Intrusive Tracing at First Instruction

In recent years, we see more and more ECUs integrating a huge number of application software components. This process mostly results from the increasing amount of so called in-house software in various fields like electric-drive, chassis and driver assistance systems. The software development for these systems is partially moved from the supplier to the car manufacturers. Another important trend is the introduction of new network architectures intending to meet the growing communication requirements. For such ECUs the software integration scenarios become more complicated, as more quality of service requirements with regards to timing, safety and security need to be considered [2]. Multi-core microcontrollers offer even more potential variants for integration scenarios. Understanding the interaction between the different software components, not only from a functional, but also from a timing view, is a key success factor for modern electronic systems [6,7,8,9].
Technical Paper

Analysis of Field-Stressed Power Inverter Modules from Electrified Vehicles

This paper presents a reliability study of a directly cooled IGBT module after a test drive of 85,000 Km in a fuel cell electric vehicle, as well as of an indirectly cooled IGBT module after a test drive of 200,000km in a hybrid car on public roads. At the end of the test drive, the inverter units were disassembled and analyzed with regard to the lifetime consumption. First, electrical measurements were carried out and the results were compared with the ones obtained directly after module production (End of Line test). After that, ultrasonic microscopy was performed in order to investigate any delamination in the solder layers. As a third step, an optical inspection was performed to monitor damages in the housing, formation of cracks or degradation of wire bonds. The results show none of the depicted failure modes could be found on the tested power modules after the field test. Obviously, no significant life time consumption could be observed.
Technical Paper

Timing Analysis and Tracing Concepts for ECU Development

Integration scenarios for ECU software become more complicated, as more constraints with regards to timing, safety and security need to be considered. Multi-core microcontrollers offer even more hardware potential for integration scenarios. To tackle the complexity, more and more model based approaches are used. Understanding the interaction between the different software components, not only from a functional but also from a timing view, is a key success factor for high integration scenarios. In particular for multi-core systems, an amazing amount of timing data can be generated. Usually a multi-core system handles more software functionality than a single-core system. Furthermore, there may be timing interference on the multicore systems, due to the shared usage of buses, memory banks or other hardware resources.
Technical Paper

Spontaneous Transistor Failures in Automotive Power Electronics

The amount of electronics in vehicles is increasing, so is the amount of power electronics circuits, like inverters for electric motor drives or dc/dc converters. The muscles of these circuits are power transistors like MOSFETs and IGBTs - in each circuit are several of them. While MOSFETs and IGBTs have advanced over the years in terms of their performance, their wide product spectrum and feature spectrum as well as cost, they are still not unbreakable, but semiconductors which are more sensitive to electrical or thermal overstress than, a relay for instance. Especially electrical overstress, like overvoltage or over current, may damage a power transistor within a short time frame. Hence, electrical overstress must be avoided when designing the power electronics circuit. However, even a power transistor in a carefully designed power electronics circuit, may still be exposed to over current, short circuit, over voltage, over temperature and so forth.
Technical Paper

Extended Qualification of Power MOSFET to Fulfill Today's Requirements of Automotive Applications

This paper focuses on the requirements of electronic systems in automotive applications in terms of reliability and quality. As one of the most common devices in such applications for switching electronic loads, the power MOSFET, is investigated in detail. Today's qualification procedure for discrete devices according to AEC Q101 [1] will be explained and how this correlates to the stress of the device in the application. It will be pointed out what additional tests for “extended qualification” should be made to deal with critical failure modes reducing overly conservative safety margins and preventing excessive costs on the component side. The tests will be explained and the results presented.