Dissertation

Fail-Operational Steer-By-Wire System in Automated Driving Vehicles Using Wheel-Individual Smart-Actuators

Author:

Minglu Li

Pages:

202

DOI:

10.18154/RWTH-2024-04656

Year:

2024

Language:

english

Format:

ebook

The electrification and intelligence of vehicles accelerate the development of automated driving systems (ADS), in which the development of safety critical electronics requires higher reliability and safety than usual fail-silent or fail-safe concepts. Steerby-wire systems for ADS shall be fail-operational and be rated with ASIL D. It is proven in this work that by using four wheel-individual fault-tolerant Smart Actuators (SA) with ASIL B classification, the safety design goal with ASIL D classification at the system level can be achieved. Therefore, this research aims to design and develop an ASIL B compliant fault-tolerant SA for a fail-operational Steer-by-Wire system in automated driving vehicles. To achieve the safety goal and safety design requirements at the subsystem (SA) level, ISO-26262 and redundancy techniques with regard to embedded hardware and software are applied. Within the scope of this work, a cross-linked structure using a voter and switching circuit is applied to provide high system reliability. Furthermore, fault-tolerant embedded systems are developed, which include a fault-tolerant power supply using ORing technique, a fault-tolerant microprocessor system using dual microprocessors and advanced E-Gas monitoring architecture, a fault-tolerant inverter using desaturation short-circuit detection measures. To validate the developed fault-tolerant concept, different faults are injected into the designed embedded systems and the resulting behavior is evaluated. The validation results show that all functional requirements concerning the safety goal and design requirements are met. The designed ECU and power inverter can tolerate various faults and operate in various degradation modes respectively. Meanwhile, the performance of SA remains operational and its functionality is continuously available during the occurrence of injected faults. Furthermore, the result of FMEDA affirms that the developed fault-tolerant power inverter can fulfill the ASIL B safety design requirement. Overall, it is shown that the designed embedded system is suitable to support future implementation of a failoperational Steer-by-Wire system in ADS.