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A commercial truck electric motor propulsion control system may require hundreds of inputs to optimize the drive torque command. As a safety-related signal, the drive torque command requires protections ensuring its integrity. Similarly, the inputs used by the control system to determine the drive torque command also require protections. To define these protections, the ISO 26262:2018 series of standards prescribe the development of safety requirements and associated Automotive Safety Integrity Levels (ASILs). Safety requirements ensure safe system output, in part, by protecting system inputs. Satisfying these safety requirements to their ASILs adds complexity and cost to commercial truck electric motor propulsion control systems. The greater the safety-related signal count, the greater the complexity and cost added.

Electric Power Assist Steering (EPAS) is a safety critical system because it affects vehicle stability and dynamics. In EPAS, electric motor takes the power from the battery and delivers this power to rack and pinion only on demand. Since EPAS contains electrical component such as Motor and electronic component such as Electronic Control Unit (ECU), reliability of these components is very important. To ensure safety and reliability, ISO 26262 standards are adapted which are derived from IEC 61508. This standard regulates the product development on system, hardware and software level and manages functional safety for electrical and electronic components. This paper discusses the applicability of the ISO 26262 standard to the development of EPAS ECU with respect to its hardware and software design. Hazard analysis and risk assessment of the basic EPAS architecture is performed and architecture is improved to achieve safety goal as per the standard.