When driving, the most important thing is that the car is safe and reliable. The ultimate goal is to prevent harm to vehicle occupants and other road users. Functional safety means that critical electronic systems continue to protect the driver and passengers even in case of a fault. Modern cars rely more and more on electronic systems for core functions like steering, braking and driver assistance. The international standard ISO 26262 and its defined Automotive Safety Integrity Levels (ASILs) have become the benchmark for evaluating the safety of these systems, especially in electric power steering (EPS) where precise control is key for both safety and driving comfort. ASIL refers to a set of safety integrity levels used to assess and manage risks in automotive systems. The risk classification scheme defined by ISO 26262 helps determine the necessary safety requirements for each system.
What is Automotive Safety Integrity Level (ASIL)
The ASIL classification helps define safety requirements for each automotive component based on a risk analysis of potential hazards. The risk classification system established by ISO 26262 ensures that the measures needed to reduce risks to an acceptable level are applied for each identified hazard. Risk management and requirements management are integral parts of the development process, making sure that safety goals and potential consequences are addressed for all components.
Hazards arising from malfunctioning systems are identified and categorized to prevent unreasonable risks. The ASIL assigned to each system is based on a thorough hazard and risk assessment, and the specific ASIL requirements for each component are determined according to the ASIL rating from this classification process. As new technologies emerge, ASIL classifications continue to evolve, with standards and guidelines such as SAE J2980 providing additional guidance.
ASIL defines four safety levels:
ASIL A—Lowest safety requirements, for systems with minimal safety impact. ASIL A is the lowest rating, typically assigned to systems with minimal safety impact, such as rear lights or brake lights, which require only standard quality management compliance.
ASIL B—Low to medium risk, requiring defined safety measures. Usually applied to systems where a fault could have limited safety consequences, such as power windows or interior lighting, and standard functional safety practices are sufficient.
ASIL C—High risk, requiring comprehensive safety design and monitoring. Assigned to systems where a failure could have significant safety consequences, such as electronic steering assistance or adaptive headlights, necessitating rigorous safety measures throughout development.
ASIL D—Highest risk, where failure could be life threatening, requires maximum safety measures. ASIL D classification represents the highest degree of risk, where failure could result in life threatening injuries. High-risk systems, such as anti lock brakes, typically require ASIL D classification.
ASIL levels are based on three critical factors:
Severity—Severity is evaluated at the vehicle level to determine the impact of a potential hazard.
Exposure—Exposure considers the likelihood of the failure scenario occurring in real world driving, taking into account the vehicle operating scenario and traffic density as factors influencing exposure.
Controllability—Controllability assesses the ability of the driver or automated system to prevent or mitigate harm.
How to determine ASIL Levels
ASIL levels are determined through a Hazard Analysis and Risk Assessment (HARA) process. This risk analysis involves evaluating risk parameters such as severity, exposure, and controllability for each potential hazard at the vehicle level. Engineers assess hazards caused by malfunctioning behavior of automotive components, considering each given hazard in the context of the vehicle operating scenario. Based on severity, exposure, and controllability, the system is assigned the appropriate ASIL level (asil rating) according to the iso 26262 standard. The safety goal for each system is defined based on the asil rating assigned during the risk classification process.
This classification then dictates the design, verification, validation, and safety mechanisms throughout the lifecycle of the system, from concept to production, as defined in ISO 26262. Risk reduction and risk reduction needed are determined to ensure tolerable risk is achieved, following the requirements management and development process outlined in the ISO 26262 standard. Risk management ensures that asils identified for each component meet the asil requirement for functional safety.
Analysis and Risk Assessment in Electric Power Steering
Electric Power Steering (EPS) systems play a pivotal role in the safety and performance of modern road vehicles. To ensure these systems meet the highest standards of functional safety, a thorough analysis and risk assessment process is essential. This process is guided by the automotive safety integrity level (ASIL), which determines the safety requirements for each EPS component and function.
In the context of EPS, analysis and risk assessment begin with identifying potential hazards that could arise from system malfunctions or failures. Engineers evaluate each risk by considering the likelihood of occurrence, the severity of possible outcomes, and the controllability of the situation by the driver or automated systems. This comprehensive approach ensures that every possible scenario is examined, from minor faults to critical failures that could compromise vehicle control.
The safety integrity level (ASIL) assigned to an EPS system is the result of this detailed risk assessment. By classifying risks according to the ASIL framework, manufacturers can implement targeted safety measures that address the specific needs of the system. For example, an EPS system with a higher safety integrity level (such as ASIL C or D) will require more robust design features, redundancy, and monitoring to mitigate risks and ensure continued safe operation.
Ultimately, the analysis and risk assessment process for EPS systems is a cornerstone of automotive functional safety. It enables automotive manufacturers to design steering systems that not only comply with industry standards but also provide drivers with reliable, responsive, and safe vehicle control under all operating conditions. By rigorously applying the ASIL-based risk assessment, the automotive industry continues to advance the safety and dependability of road vehicles for everyone on the road.
Functional Safety in Steering Systems
Functional safety is especially critical in steering systems, as vehicle control directly impacts driver and passenger safety.
Key applications include:
Critical control safety: ASIL based designs ensure the steering ECU remains operational even if part of the system fails, vehicle control is maintained.
Redundancy and monitoring: High risk steering systems often use dual-channel redundancy and real-time monitoring to detect faults early, prevent sudden loss of control.
Hardware and software verification: Following ISO 26262 lifecycle processes ensures every stage—from design, software development, integration to final validation—meets safety objectives.
Support for advanced driver assistance systems (ADAS): Functional safety provides a foundation for features like lane-keeping assistance, automated parking and traffic jam assist, keeping the vehicle stable and controllable in all driving conditions.
By doing so manufacturers can reduce the risk of steering failures and increase reliability and overall driving safety. Effective risk management throughout the development process is essential for achieving these safety goals.
The benefits of ASIL Compliance
For manufacturers: Compliance reduces the risk of system failures, strengthens the supply chain and ensures vehicles meet global safety regulations.
For consumers: Vehicles become safer, more predictable and easier to control, more confidence and comfort behind the wheel.
For the automotive industry: Standardized safety practices help to propagate advanced steering technologies and ensure consistent safety performance across vehicle models. ASIL classifications and risk management practices help ensure that safety goals are consistently met across all vehicle models.
Meeting ASIL requirements provides a measurable benchmark for functional safety, so manufacturers can design steering systems that are robust and reliable, safe and precise under all conditions.
How XEPS supports ASIL Compliance
XEPS provides electric power steering (EPS) systems that fully comply with ISO 26262 functional safety standards, covering all ASIL levels. To address different OEM requirements XEPS offers:
Brushed DC Motor EPS: A simple electromechanical design, limited fault propagation paths and low software complexity, this system achieves ASIL B, suitable for medium risk applications. Reliable performance with minimal fault risk.
Brushless DC Motor (BLDC) EPS: For high risk scenarios, it has dual-channel monitoring, software intensive control and independent safety mechanisms to achieve ASIL D, the highest safety level. Fully compliant with ISO 26262:2018, it ensures steering reliability in critical situations even in case of system failures.
Customized EPS Systems: For different vehicle models and applications XEPS offers EPS solutions that meet ASIL A–D, with hardware redundancy, fault monitoring and advanced software controls, tailored to OEM safety, reliability and performance requirements.
By offering these solutions XEPS enables manufacturers to design steering systems that not only meet regulatory safety standards but also driving comfort, precision and confidence.
XEPS
XEPS develops, produces and supplies customized electric steering systems solutions for the automotive industry. We help our OEM customers balance safety and cost while delivering a precise, comfortable, and safe driving experience.
