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In this paper, we propose a hardware and a software design method considering functional safety for an electro-mechanical brake (EMB) control system which is used as a brake actuator in a brake-by-wire (BBW) system. A BBW system is usually composed of electro-mechanical calipers, a pedal simulator, and a control system. This simple by-wire structure eliminates the majority of bulky hydraulic brake devices such as boosters and master cylinders. The other benefit of a BBW system is its direct and independent response; this leads to enhanced controllability, thus resulting in not only improved basic braking performance but also considerably easier cooperative regenerative braking in hybrid, fuel-cell, and electric cars. The importance of a functional safety based approach to EMB electronic control unit (ECU) design has been emphasized because of its safety critical functions, which are executed with the aid of many electric actuators, sensors, and application software.

Currently major investments by Tier1 and vehicle manufacturers are made to implement and optimize safety critical automotive systems according to the ISO standard 26262 “Road vehicles functional safety”. The ISO 26262 standard describes methods to detect the safety critical faults of a system designed according to the rules of functional safety, but it does not describe how an actual implementation shall look like. Development of ISO 26262 standard compliant systems concentrates on optimizing and improving cost and performance in a competitive environment. More competitive and practical implementations use fewer additional hardware and software resources for safety control and error detection and have higher performance with less overhead. Microcontrollers already have implemented many safety related hardware functions, so called safety mechanisms to mitigate safety critical risks.