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1 Link: Development Active and Passive safety Authors Dipl.-Ing. (FH) Kathrin Sattler is a research assistant at the Institute for Applied Research at Ingolstadt University of Applied Sciences Dipl.-Ing. (FH) Andreas Raith is a research assistant at the Institute for Applied Research at Ingolstadt University of Applied Sciences 48 Dipl.-Ing. Daouda Sadou is Head of Test and Functional Safety Management, Occupant Safety and Inertial Sensors at Continental Automotive GmbH in Regensburg Dr.-Ing. Christian Schyr is Product Manager Test Systems at IPG Automotive GmbH in Karlsruhe Motivation Recent years have seen a rapid rise in complexity in this field of testing. In the future, this trend will continue and intensify even further. The limits of current methods and practices are already being reached when testing the various interconnected safety systems, ❶. Therefore, new types of testing systems, testing methods and test strategies have to be developed for the chronologically consistent testing of the individual safety systems, not only, but especially, during a critical driving situation or accident scenario. To achieve this, the test scenario as depicted in ❷ is divided into the three phases of Normal Driving, Precrash and Incrash. In the Normal Driving phase, the behaviour of driver assistance systems in a normal, non-critical driving situation, such as driving in urban traffic flow, is tested. When a critical driving situation occurs in which a collision is inevitable, such as a vehicle approaching a preceding vehicle, initial measures to mitigate the severity of the accident are initiated in the pre-crash phase by means of active safety systems. This includes the activation of a reversible seat belt ten-

2 Testing System for Integrated, Highly Interconnected Safety Systems The rapid development of a wide range of new safety systems in the automotive sector and the increasing degree of interconnection between these systems in networks within the vehicle inevitably lead to an increase in testing complexity. In the current Visaps research project, the testing system developed by Ingolstadt University of Applied Sciences, IPG Automotive GmbH, Karlsruhe, and Continental Automotive GmbH, Regensburg, is being expanded and optimised by the addition of new features. sioner or the initiation of an automatic emergency braking function. The incrash phase begins at the time when both vehicles contact each other. In this e. g. Adaptive Cruise Control (ACC) e. g. Electronic Stability Control (ESC) See Feel Integrative safety system phase, passive safety systems such as the airbag are deployed. In order to be able to test the entire, consistent course of events, a new type Hear Communicate e. g. Crash Impact Sound Sensing (CISS) e. g. Car2Car communications via mobile or wireless networks ❶ Different systems communicate with each other within an integrated safety system. By extending environment detection, various sensor strategies such as radar, lidar or ultrasound are pursued (seeing). Measurements of the structural vibrations make the structure-borne sound audible (hearing). Vehicle dynamics (feeling) and Car2Car communications via mobile or wireless networks (communicating) are also part of this. of testing system has been developed. It is made up of a powerful vehicle dynamics simulation environment combined with the automatic feed-in of crash data. In the Visaps research project (Networking and Integration of Safety Systems of Active and Passive Safety) funded by the German Federal Ministry of Economics and Technology, an initial step towards such an innovative testing system has been taken by Ingolstadt University of Applied Sciences, IPG Automotive GmbH in Karlsruhe, Continental Automotive GmbH in Regensburg, Berner & Matter Systemtechnik GmbH in Munich and Otto-von-Guericke University Magdeburg, [1, 2 and 3]. Testing System The core of the hardware-in-the-loop (HiL) testing system depicted in ❸ is the real-time-capable and three-dimensional simulation of the vehicle and its environment. During complex test manoeuvres, this simulation platform communicates with the connected control unit (Safety Control Unit) via the corresponding intelligent I/Os. All signals are consist- 49

3 Development Active and Passive Safety -2.0 s -0.5 s -100 ms t ms Normal driving Driver assistance systems Precrash Active safety systems Incrash Passive safety systems ❷ Driving scenarios are divided into the three phases of Normal Driving, Precrash and Incrash ently generated by virtual sensors based on the currently simulated driving and environmental situation as shown in ❹. This means that, in contrast to conventional testing systems available on the market, complex time-based signal conditioning of the individual test cases is no longer necessary. In addition to conventional I/Os such as analogue, CAN, LIN and FlexRay, special modules for SPI (Serial Peripheral Interface) and PSI5 (Peripheral Sensor Interface) have been developed. All I/Os are equipped with fast and precisely timeable manipulation possibilities for electrical fault feed-in, such as undervoltage, short circuits or sensor faults. By means of special electrical measurement cards, the output signals of the control unit, such as the ignition circuits of the airbag, can be monitored and their correct functionality checked in the various driving situations. In the area of the connected bus systems, it is possible via the intelligent I/O to generate faults on the physical level, such as check sum or timeout faults in the case of CAN, as well as on the content-related signal level. This makes it possible to represent fault conditions of peripheral control units, such as engine or vehicle dynamics control units, in a way that is consistent with the current driving manoeuvre. By means of a trigger that is integrated into the vehicle simulation, a crash is detected and the crash data fitting the situation are imported from a database and consistently fed into the corresponding I/Os within one simulation step. Concurrently with the simulated signals, the internal signals from the control unit are synchronously acquired and analyzed in the testing system via a corresponding application interface. The integrated automation in the testing system enables efficient loading of various data inputs into the control unit as well as the reading and analysis of the fault codes according to the driving manoeuvre performed and the fault conditions fed in. Testing Methods and Test Strategy Another substantial element of efficiently testing such a highly interconnected safety system is the intelligent combination of different testing methods for the optimum coverage of the test space. A significant part of the research conducted in this project is the elaboration and evaluation of a test strategy for the system testing of highly interconnected safety systems. This test strategy depicted in ❺ is based on four different types of testing methods: systematically deter- Programming, calibration, OBD ❸ The HiL testing system which, with CarMaker, contains a vehicle dynamics and environment simulation plus a crash database, communicates through intelligent I/Os with the Safety Control Unit Crash DB Crash characteristics : Velocity : Coverage of obstacle and vehicle : Impact angle : Safety control unit Crash signals CarMaker Vehicle environment Current measurement SPI PSI5 analog Bus systems (CAN, LIN, FlexRay) Intelligent IO 50

4 Random number tests/ statistical tests Monte Carlo methods, random number tests, combination of single errors: : Finding hidden errors by searching randomly in significant data boundaries : Combination of single errors leads to deeper test coverage Priority Evolutionary testing Analysis of marginal situations, determination of most critical maneuvers: : Marginal situations can be examined thoroughly and easily : Combination with maneuverbased testing makes finding critical maneuvers fast and assuredly Test strategy Maneuverbased test cases Normal and critical situations, accidents with crash data feeding: : Testing under real conditions possible before a vehicle is available : Reduction of real driving tests : Continuous testing throughout the whole process of an accident Systematically identified test cases ISO recommended test methods, classification tree methods, equivalence classes, boundary value analysis: : Systematic approaches lead to a good coverage of data, functions and requirements : Prediction of test progress is possible : Most methods are well documented and tools are available ❹ Real-time visualisation of the vehicle and environment before and during the simulated crash ❺ Innovative testing methods are used for the system testing of highly interconnected safety systems such as the Safety Control Unit T e s t m e t r i c mined tests, manoeuvre-based testing, evolutionary testing plus random and statistical tests. Systematic testing is the most important column in this context. By means of the methods recommended by ISO [4] for the system test, such as requirements-based, back-to-back or interface tests, good test coverage can be achieved. The testing system developed in the project provides all the manipulation options and fault feed-in paths required for this purpose. For example, trace feed-in with and without data manipulation via the various bus and sensor interfaces, crash data feed-in for the seamless testing of accident scenarios and residual bus simulation with data manipulation are possible. In the future, this test metric, which is currently under development, will also make it possible to make a statement about the progress of the test. Another increasingly important testing method is manoeuvre-based testing. By connecting CarMaker to the testing system, both vehicle dynamics and environmental data of the simulation can be fed into the Safety Control Unit. As a result, normal driving conditions as well as critical situations right through to accidents can be fully represented and without the need to draw on real-world road tests. This allows extensive tests with complex scenarios to be run in an early phase of the control unit s development when a trial vehicle is not yet available, ❻. Evolutionary testing is anchored in the test strategy as the third column [5]. By means of this method, optimised test cases are found using search algorithms that are oriented to the biological processes of the recombination and mutation of genes. An initial population a parameter set for a test case in the CarMaker simulation platform record is used in the case presented here continues to be optimised until a desired target value occurs. For example, in a braking manoeuvre with steering wheel turn-in, lateral acceleration is maximised in order to find a case that is as laterally critical as possible. As a fourth item, random tests and statistical tests and their effectiveness in the system testing of highly interconnected safety systems are to be examined. The application of Monte Carlo methods, random tests and a combination of single faults makes it possible to identify faults that have not yet been detected. 51

5 Development Active and Passive Safety tested accordingly. Consequently, a very broad base of crash data is required. The generation of these crash data, whether obtained from the real world, from recordings of the sensor signals in crash tests or generated artificially such as by FEM simulation, has been very timeintensive and thus cost-intensive. Therefore, the Visaps research project also includes the development of a new type of method that generates a new data record with the desired accident configuration from existing, real-world crash data through scaling and interpolation. For this purpose, in the event of an accident, the required accident parameters, such as impact angle, impact speed or overlap of the two vehicles in relation to each other at the time of impact (t0), are calculated from the CarMaker simulation. Using these configuration data, a search for data records with configurations coming close to the calculated one is run in the database that is connected to the test system. These data records are then fed into the newly developed algorithm. Through targeted scaling and interpolation of the initial data, this algorithm generates a new data record. The signals of the artificially generated data record correspond to those of a data record created by recording the sensor signals during a real-world crash test. The accident configuration is identical to the one from the CarMaker simulation. The curves of the crash signals thus generated are fed into the testing system to test the safety system. On conclusion of the Visaps research project, the testing system will be subjected to certification according to ISO ❻ Consistent manoeuvre-based representation of complex driving and crash scenarios By combining these four different testing methods closely tied to a test metric the prerequisites have been created for achieving optimum coverage of the test space. In addition, the test metric is to be used for fault rate estimates and a complexity estimate of the development project. Based on this, a suitable selection of the testing methods as well as their scope can be determined. Outlook In the current Visaps research project, which is also funded by the Federal Ministry of Economics and Technology, the testing system developed so far is being extended by the addition of several new features and optimised by Ingolstadt University of Applied Sciences, IPG Automotive GmbH Karlsruhe and Continental Automotive GmbH Regensburg. In particular, the generation of crash data relative to runtime is a focal area of further development. Using the powerful Car- Maker vehicle dynamics simulation from IPG, a wide range of accident scenarios can be simulated and safety systems References [1] Raith, A.; Sattler, K.; Ertlmeier, R.; Brandmeier, T.: Networking and Integration of Active and Passive Safety Systems. Proceedings of the 9 th Workshop on Intelligent Solutions in Embedded Systems (WISES 2011), IEEE Conference Proceedings, p , Hochschule Regensburg, Regensburg, Juli 2011 [2] Raith, A.; Sattler, K.; Schyr, C.; Sadou, D.; Brandmeier, T.: Test system including crash data feeding for manoeuvre-based testing of integrated safety systems. crash.tech 2012, Conference Proceedings, lecture number 23, TÜV Süd, München, April 2012 [3] Sattler, K.; Raith, A.; Brandmeier, T.: Efficient test methods for the system test of highly networked safety systems. 10 th Workshop on Intelligent Solutions in Embedded Systems (WISES 2012), Alpen- Adria-Universität, Klagenfurt, July 2012 [4] International Organisation for Standardisation, ISO 26262: Road vehicles Functional safety. November 2011 [5] Reiner, J.; Meyer, J.: Evolutionäres Testen von Steuergeräten. Elektronik automotive, September 2010 Thanks The authors would like to thank Dipl.-Ing. (FH) Rudolf Ertlmeier and Prof. Dr.-Ing. Thomas Brandmeier from the Institute for Applied Research at Ingolstadt University of Applied Sciences for their contribution to this article. 52

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