Vehicle networks form the very backbone of car electronics. To make sure everything works in harmony, it is necessary to carry out comprehensive testing during development. This involves putting each control device through a series of integration tests. The first step is to test each individual interface before integrating the various elements into different sections of the vehicle network, and then finally looking at the vehicle network as a whole. Each round of testing is initially carried out under laboratory conditions before integrating the different elements into the vehicle. Such network testing is carried out at the Steinbeis Transfer Center for Microelectronics (TZM) in Göppingen.
The introduction of CAN bus technology in the early 1990s and the networking of electric and electronic vehicle components resulted in a significant rise in the complexity of the electronic systems used in vehicles. Previously, networks were restricted to the electrics in the engine but they have now expanded into all areas of vehicle electronics. Development of the kinds of advanced driver assistance systems, safety systems and driving comfort systems now found in modern vehicles has led to a sharp rise in the number of control devices, and with this: an increase in vehicle data. This has made it necessary to exchange data more and more quickly – and of course accurately – between individual control devices. To meet such requirements, modern vehicles not only need CAN technology, but also LIN, MOST and FlexRay. Even Ethernet technology, previously associated with IT and industrial communications, are part and parcel of modern vehicle technology.
Given the sheer number of control devices now used in modern vehicles (there are over 100 different devices in luxury segment vehicles) and given the huge degree of variety now offered by carmakers, it is clear that tremendously complex processes are required to ensure everything functions as required. Specialists have to establish clear processes to keep things running smoothly and test networks as efficiently as possible in terms of time and money.
Another important and related factor is the degree to which testing can be automated. Automation makes it possible to reduce testing errors to a minimum and slash the amount of time needed to test each control device. One of the challenges this brings forth is the degree to which test processes and individual testing can be standardized, while at the same time taking the immense complexities of the individual control devices into account. For example, LIN slaves, which are actually quite simple in terms of complexity, have to be tested in addition to highly complex gateways, which link up several, sometimes completely different bus systems.
To put the right kind of testing environment into place, TZM decided to use products provided by a company called Vector Informatik. The testing environment used for network testing is based on a Vector VT System. This makes it possible to monitor and assess all bus systems simultaneously. Control devices are administered through a database which contains all key information required for the testing. This database also includes the current status of testing and results. A control slip is attached to each control device so that it can be positively identified and the right data can be sent to the database. The testing environment is set up to ensure that the test runs and test parameter sets are kept completely separate. Information from the database is used at the beginning of each testing sequence to create a parameter file in XML format. This is to establish the right parameters for the testing environment.
During each test sequence, all required testing is carried out in the most logical order. This means that the test environment first checks individual bus interfaces, and once each interface has been tested, it switches to the next interface to carry out testing in this area. All parameters are documented along with test results in test protocols so that it is possible to reproduce results later. The control devices are tested both individually and then as part of the overall network. This is to check whether all control devices are reacting in line with the network specification, for example, as outlined by the network management system or wake-up protocols.
Testing can be kept highly automated by ensuring that the test environment is able to test control devices one after the other. Once all the interfaces relating to a control device have been tested, the test environment automatically jumps to the next control device. The setup goes through each control device on a first-in, first-out basis (FIFO queue). This means a previously tested control device an be removed at any point and a new control device can be connected to the test system. As a result, ideally the test system can even carry out integration testing without interruption.
By going through test results afterwards, irregularities can be evaluated to see if there are any problems with individual control devices and whether, for example, these may have been caused by incorrectly setting up parameters for the test environment. If the latter is the case, the preparations made before testing need re-examining and testing will have to be repeated. Test documentation is based on the results of the test evaluation and the assessment of findings. Noticeable irregularities are documented in an error database. The network test is finished once this part of the process is complete.
The TZM has been working successfully on this and other industry projects since 1991. There are currently around 90 people working in the fields of engineering and development, embedded systems and software engineering, spanning a variety of projects related to medical technology, the automotive industry and automation technology. The project outlined above was carried out by the embedded systems division, whose focus lies in networks and bus systems, plus two other core fields: embedded software and the setting up of test systems.
Christoph Königs (Bereichsleiter Embedded Systems), Tobias Streitberger (Teamleiter Testing) und Marc Pejga (Teamleiter Fahrzeugvernetzung) all work at the Steinbeis Transfer Center for Microelectronics in Göppingen. The Steinbeis Enterprise has been providing companies with engineering services for over 20 years with a focus on the automotive industry, the medical industry and automation. In 2007, the Steinbeis Transfer Center for Microelectronics was honored with a special transfer prize by the Steinbeis Foundation.
Christoph Königs
Tobias Streitberger
Marc Pejga
Steinbeis Transfer Center Microelectronics (Göppingen)