Electronic components make up 15 to 20% of vehicle value today. That figure will increase by as much as 30 to 40% in the future as vehicles incorporate more electronics in safety mechanisms, fuel-consumption and emission-control systems, integrated communications and navigation systems, car infotainment solutions, and comfort features.
Implementing these functions today requires 20 to 50 electronic control units (ECUs) utilizing approximately 70 to 150 sensors to perform all their functions. The sensors measure a wide range of analog environmental quantities such as pressure, temperature, flow, speed, acceleration, and angle. They transmit the measured values to the ECUs for engine and climate control, airbag triggering, and comfort and safety functions. Systems such as antilock braking systems (ABS), electronic stability program/control (ESP/ESC), and braking assist also rely on sensor input.
In these applications, the ability of the various systems to self-diagnose is increasingly important. For example, if it is possible to detect sensor defects directly at the sensor element, the ECU has reliable data on which to make corrective decisions. System deactivation and emergency operation are especially important for safety-related systems.
Vehicle electronics as a network application
An analysis of vehicle electronic control systems shows that the complexity of these assemblies grows exponentially. Simple electronic control and regulating assemblies have been replaced with more complex IT-systems. Within these, the software and the intercommunication between the ECUs constitute, in addition to the actual hardware, a new point of emphasis.
The individual assemblies in a modern vehicle are interconnected via 10 to 20 different data buses (see below).
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For example, it is possible via the diagnostic CAN bus to access each individual ECU and query its status, read out error codes, and even re-flash the firmware. Today, many applications share sensors for cost reasons. This means that a sensor-module measured value (data) is processed by several ECUs.
A large number of functions in the car have become network applications. The common structure of the past—one ECU implementing one application—has been superseded by networked functions shared across several ECUs.
The figure below shows such a functional tree for a trunk lid, where two ECUs are actively involved in the opening of the lid. Additional ECUs are involved in display and control functions.
Malfunctions in this system can be caused by any several defects. Consequently six different defect patterns are possible with the opening of the trunk lid—it is possible to observe that nothing at all happens, the lock opens, or the lid strikes the stop.
Should the one required sensor malfunction, it can result in more than ten different entries in the fault memories of the involved ECUs. From this constellation of error codes, it is necessary to make significantly more detailed sensor diagnostic information available than in the past.
