The CAN bus is the most common data network in modern vehicles. However, as the trend continuously moves towards an increasing number of ECUs per additional communication networks have found their ways into new vehicle designs. The LIN bus, for example, is a subsystem of the CAN network and is used to relieve the bus load of the supervising CAN network and to reduce overall costs.
On the other hand, FlexRay communication between ECUs has become popular for safety critical applications, such as drive-by-wire. All the different networks within vehicles are connected via gateway ECUs that require special test cases like routing and transmission time.
Image 1: functional test system for testing network characteristics of control units
Modern vehicle ECU's also support overall vehicle safety features on a system level. It is therefore of paramount importance that the ECU works faultlessly under all operating conditions. It is furthermore required that an ECU will not affect the overall communication in the vehicle environment or goes out of control in the event of a communications breakdown if the unit is connected to the vehicle bus.
For the purposes of test the ECU’s system functions can be divided into physical, i.e. usually electrical, and communication characteristics. The test system measures electrical characteristics without a network connection. In order to measure the communication characteristics it is necessary to simulate the vehicle environment via one or more bus nodes.
Furthermore, failure simulations are yet other test tasks not to be neglected. The scope of failure simulation includes hardware faults as well as failures of the communication protocol written into the software.
System architecture requirements
The development of the test system started already 15 years ago, originally developed and implemented around the specifications for high speed and low speed CAN buses, CAN transport protocols and CAN diagnosis (KWP 2000) requirements. Further developments have added the ability to test K-line functions and LIN bus systems. Meanwhile, the