🚗Autonomous Vehicle Systems Unit 9 – Safety and reliability

Key Concepts and Definitions

• Safety involves protecting individuals from harm or injury and ensuring the system operates without causing damage
• Reliability refers to the ability of a system to perform its intended function under specified conditions for a specified period
• Risk is the combination of the probability of an event occurring and the severity of its consequences
• Hazard represents a potential source of harm or adverse health effect on a person or persons
• Fault tolerance enables a system to continue operating properly in the event of the failure of some of its components
• Redundancy involves the duplication of critical components or functions of a system with the intention of increasing reliability
• Validation is the process of ensuring that a system meets the operational needs of the user
  • Involves testing the complete integrated system in a realistic environment
• Verification is the evaluation of whether a system complies with its specified requirements and regulations
  • Performed at various stages of the development process

Safety Challenges in Autonomous Vehicles

• Complex decision-making in dynamic environments with multiple actors (pedestrians, vehicles, obstacles)
• Ensuring safe operation under various weather conditions (rain, snow, fog) and lighting (day, night)
• Handling edge cases and unexpected scenarios not encountered during training or testing
• Cybersecurity vulnerabilities and potential for hacking or malicious attacks on the system
• Interaction with human-driven vehicles and predicting their behavior
• Ethical considerations in unavoidable collision scenarios (trolley problem)
• Building public trust and acceptance of autonomous vehicle technology
• Establishing liability in the event of accidents involving autonomous vehicles

Reliability Engineering Principles

• Design for reliability by incorporating redundancy, fault tolerance, and fail-safe mechanisms
• Conduct Failure Mode and Effects Analysis (FMEA) to identify potential failure modes and their impact
• Perform reliability testing to assess the system's ability to function under various conditions
  • Accelerated life testing subjects components to increased stress to estimate their lifespan
  • Reliability growth testing identifies and fixes issues to improve reliability over time
• Implement preventive maintenance strategies to minimize downtime and extend system life
• Continuously monitor and analyze field data to identify emerging reliability issues and trends
• Use reliability prediction methods (MIL-HDBK-217) to estimate the reliability of components and systems
• Apply reliability-centered maintenance (RCM) to optimize maintenance strategies based on system criticality
• Establish a robust supply chain and manage obsolescence to ensure long-term availability of components

Risk Assessment and Management

• Identify potential hazards and risks associated with the autonomous vehicle system
• Analyze the likelihood and severity of each identified risk using quantitative or qualitative methods
• Evaluate the acceptability of risks based on predefined criteria and stakeholder input
• Prioritize risks based on their potential impact and likelihood of occurrence
• Develop risk mitigation strategies to reduce the likelihood or severity of high-priority risks
  • Elimination removes the hazard completely
  • Substitution replaces the hazard with a less dangerous one
  • Engineering controls reduce the hazard through design changes
  • Administrative controls limit exposure to the hazard through procedures and training
• Implement risk mitigation measures and monitor their effectiveness over time
• Continuously reassess risks throughout the system lifecycle as new information becomes available

Safety Standards and Regulations

• ISO 26262 provides a framework for functional safety in automotive electrical and electronic systems
  • Defines Automotive Safety Integrity Levels (ASIL) to classify the severity of potential hazards
• ISO/PAS 21448 (SOTIF) addresses safety concerns related to the intended functionality of the system
• SAE J3016 defines levels of driving automation and the roles of human drivers and automated systems
• UN Regulation No. 157 establishes requirements for Automated Lane Keeping Systems (ALKS)
• NHTSA provides guidance and voluntary standards for the development and deployment of autonomous vehicles
• Compliance with regional and national regulations (Federal Motor Vehicle Safety Standards in the US)
• Adherence to industry best practices and guidelines (SAE, IEEE, NIST)
• Collaboration with regulatory bodies to shape future standards and policies for autonomous vehicles

Sensor Fusion and Redundancy

• Combine data from multiple sensors (cameras, radar, lidar, ultrasonic) to enhance perception accuracy
• Exploit the strengths of each sensor type while mitigating their individual weaknesses
  • Cameras provide rich visual information but are affected by lighting conditions
  • Radar accurately measures distance and velocity but has low spatial resolution
  • Lidar provides high-resolution 3D point clouds but is expensive and has limited range
• Implement sensor redundancy to ensure reliable operation in case of sensor failures or degradation
• Use diverse sensor types to provide complementary information and cross-validation
• Apply data fusion algorithms (Kalman filter, particle filter) to estimate the state of the environment
• Perform temporal fusion to integrate sensor data over time and track objects
• Implement fault detection and isolation techniques to identify and handle sensor failures
• Regularly calibrate and maintain sensors to ensure optimal performance and data quality

Fault Detection and Diagnosis

• Monitor system parameters and performance indicators to detect anomalies and deviations from normal behavior
• Implement rule-based or model-based fault detection techniques to identify specific fault conditions
  • Rule-based methods use predefined thresholds and logic to detect faults
  • Model-based methods compare system behavior with a mathematical model to detect discrepancies
• Employ machine learning algorithms (SVM, neural networks) for data-driven fault detection and classification
• Analyze fault symptoms and patterns to isolate the root cause of the problem
• Develop a fault diagnosis framework that considers the relationships between faults and their observable effects
• Use fault trees or Bayesian networks to represent the causal dependencies between faults and symptoms
• Incorporate expert knowledge and historical data to improve fault diagnosis accuracy
• Implement fault recovery mechanisms to maintain safe operation or bring the system to a safe state

Testing and Validation Methods

• Conduct extensive simulation testing to evaluate the system's performance in a wide range of scenarios
  • Use high-fidelity simulation environments (Gazebo, CARLA) to model vehicle dynamics and sensor behavior
  • Generate synthetic datasets with diverse weather conditions, road layouts, and traffic scenarios
• Perform hardware-in-the-loop (HIL) testing to validate the integration of software and hardware components
• Conduct real-world closed-course testing in controlled environments to assess system performance
  • Test specific functionalities (lane keeping, obstacle avoidance) in isolation before full system integration
• Carry out public road testing with safety drivers to validate the system's behavior in real traffic conditions
• Implement a phased approach to testing, gradually increasing the complexity and scope of the scenarios
• Develop comprehensive test case libraries that cover both common and edge case situations
• Use coverage metrics (code coverage, scenario coverage) to assess the thoroughness of the testing process
• Continuously monitor and analyze real-world performance data to identify areas for improvement and validation