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Functional Safety
| Question | Answer |
|---|---|
| What is Functional Safety? | Functional Safety is making sure that if something goes wrong in a vehicle, the system can detect the problem and move to a safe condition before anybody gets hurt |
| What is ISO 26262? | ISO 26262 is the automotive standard that provides the framework and processes to achieve Functional Safety throughout the vehicle development lifecycle |
| What is a (HARA)? | "HARA is a process used to identify hazards, evaluate risks, and determine the required ASIL level." |
| What is an Item | An item is a system or function that performs a specific vehicle-level operation and is the subject of Functional Safety analysis." Battery Management System Electric Drive Unit Steering System |
| What are the factors used in HARA? | "HARA evaluates Severity, Exposure, and Controllability." |
| What is Severity? | "Severity represents the potential level of harm that may result from a hazardous event." Example: Minor injury Serious injury Fatality |
| What is Exposure? | "Exposure represents how frequently the operating situation occurs." |
| What is Controllability? | "Controllability represents the driver's ability to avoid harm after a malfunction occurs." |
| What is ASIL? | "ASIL stands for Automotive Safety Integrity Level. It is a risk classification defined by ISO 26262." |
| What is a Safety Goal? | "A Safety Goal is a top-level safety requirement derived from HARA that aims to prevent or mitigate a hazardous event." Hazard: Unintended acceleration. Safety Goal: "The vehicle shall prevent unintended torque generation." |
| What is a Functional Safety Concept (FSC)? | The Functional Safety Concept defines the functional safety measures needed to achieve the Safety Goals. FSC says: WHAT must happen Not HOW it will be implemented |
| What is a Technical Safety Concept (TSC)? | defines how the FSRs are implemented using technical mechanisms, hardware, software, and system architecture." FSC:"Torque shall be monitored." TSC:Independent torque monitor Dual-core processor monitoring Plausibility checks Watchdog supervision |
| What is a Functional Safety Requirement? | "A Functional Safety Requirement is derived from Safety Goals and specifies safety behavior at a functional level." |
| What is a Technical Safety Requirement? | is derived from Functional Safety Requirements and specifies detailed technical implementation requirements." FSR> "The system shall detect unintended torque." TSR>"The torque monitor shall detect deviations exceeding 5% within 100 milliseconds." |
| What is a Safe State? | A safe state is a system condition that minimizes risk when a fault occurs." Examples Disable torque Stop charging Enter limp-home mode |
| What is Fault Tolerance? | "Fault tolerance is the ability of a system to continue operating safely after a fault occurs." |
| What is Redundancy? | "Redundancy means having independent elements performing similar functions to improve safety." Example Two sensors measuring position. One verifies the other. |
| What is Freedom from Interference? | "Freedom from Interference ensures that software or hardware elements of different safety levels cannot adversely affect each other." ASIL D software cannot be corrupted by QM software. |
| What is a Single Point Fault? | "A single point fault is a fault that directly leads to violation of a Safety Goal without any safety mechanism preventing it." Top Event ↓ Subevento ↓ Subevento ↓ Subevento ↓ Basic Event |
| What is a Latent Fault? | "A latent fault is a hidden fault that remains undetected until another fault occurs." Top Event ↑ AND / \ Fault A Fault B Supongamos que: Fault A ocurrió hace una semana. Pero nadie lo detectó. |
| What is a Safety Mechanism? | "A safety mechanism is a technical measure used to detect, prevent, or mitigate faults." Examples: Watchdog CRC Plausibility check Voltage monitoring |
| What is a Watchdog? | "A watchdog supervises software execution and detects abnormal operation." Software --> Watchdog "Estoy vivo" Timer vuelve a 100 ms |
| What is a Plausibility Check? | compares signals or measurements to determine whether values are physically reasonable Pedal sensor A = 30%, Pedal sensor B = 90%. Not plausible=Fault detected Vehicle Speed = 250 km/h, Accelerator Pedal = 0%, Motor Speed = 500 RP, Wheel Speed = 0 km/h |
| What is SPFM? | Single Point Fault Metric Answer "SPFM measures the effectiveness of safety mechanisms in handling single-point and residual faults." |
| What is LFM? | Latent Fault Metric Answer "LFM measures the effectiveness of detecting latent faults in the system." |
| What is FMEA? | "Failure Modes and Effects Analysis is a systematic method used to identify potential failures, their causes, and consequences." |
| What is FMEDA? | "Failure Modes Effects and Diagnostic Analysis extends FMEA by considering safety mechanisms and diagnostic coverage." |
| What is FTA? | Fault Tree Analysis Answer "FTA is a top-down analysis method used to identify combinations of faults that may cause a hazardous event." |
| What is DFA? | "Dependent Failure Analysis evaluates the possibility that multiple failures could occur due to a common cause." |
| What is EGAS? | "EGAS is a safety-oriented architecture originally developed for engine management systems. Capa 1: Functional Layer Es la que hace el trabajo. Capa 2: Monitoring Layer Supervisa. Capa 3: Safety Layer Si la capa 2 detecta un problema: Safe Reaction |
| Explain EGAS three-layer architecture | uses a functional layer that performs the control task, a monitoring layer that verifies the output, and a safety layer that can force the system to a safe state when a fault is detected." Layer 1 = Do work. Layer 2 = Check work.Layer 3 = Emergency stop. |
| Walk me through the safety lifecycle from HARA to test execution. | Item Definition and HARA. Hazards identified and ASIL levels. Safety Goals then Functional Safety Reqs developed in the FSC. refined in TSR in the TSC. Reqs are allocated to HW and SW, implemented, verified through test cases, and validated |
| What is a Multiple Point Fault? | is a combination of two or more independent faults that must occur together before a Safety Goal can be violated. |
| EXAMPLE EGAS | 1Pedal = 50% ↓ Calcula torque = 150 Nm ↓ Manda torque al motor 2¿El cálculo tiene sentido? Torque pedido = 150 Nm Torque generado = 600 Nm 3Safe Reaction = Torque = 0 Nm |
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yizuztineo