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Adaptive Cruise Control : Failure Analysis using PathFinder

Introduction

Adaptive Cruise Control (ACC) is an advanced driver assistance system designed to make driving more comfortable and safer by automatically adjusting the vehicle’s speed to maintain a safe following distance from the vehicle ahead. Here are its main functions:

Speed Adjustment: ACC adjusts the vehicle’s speed to maintain a preset distance from the vehicle in front. If the vehicle ahead slows down, ACC will reduce the car’s speed to maintain the gap, and if the road ahead is clear, it will accelerate back to the preset speed.

Stop-and-Go Functionality: Some ACC systems offer stop-and-go functionality, allowing the vehicle to come to a complete stop and then resume driving in traffic without the driver needing to manually operate the brakes or accelerator.

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Adaptive Cruise Control (ACC) enhances driving comfort and safety by automating speed control and maintaining a safe following distance, allowing the driver to focus more on steering and monitoring the road.

System Description

Adaptive Cruise Control (ACC) systems are comprised of several key components, each playing a crucial role in its operation. Excluding the actuation system, which directly controls the vehicle’s speed through throttle and brake manipulation, the main components are the Sensor and the Electronic Control Unit (ECU):

Sensor(s): Sensors are the eyes of the ACC system, responsible for detecting and monitoring the position and speed of vehicles ahead. There are several types of sensors used in ACC

Electronic Control Unit (ECU): The ECU is the brain behind the ACC system. It processes the data collected by the sensors to make real-time decisions. Key functions of the ECU include:

  • Data Analysis: It analyzes sensor data to determine the distance and speed of the vehicle ahead, as well as its own vehicle’s speed and lane position.
  • Decision Making: Based on the analyzed data, the ECU calculates the necessary adjustments to the vehicle’s speed to maintain a safe following distance, factoring in the driver’s set preferences for speed and distance.

The ECU communicates with other vehicle systems to ensure a harmonious operation.

Although direct actuation is excluded from this description, the ECU plays a critical role in sending the commands to the vehicle’s braking and throttle systems based on the ACC’s objectives.

The Electronic Control Unit (ECU) for Adaptive Cruise Control (ACC) systems is a multi-layered

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The Electronic Control Unit (ECU) for Adaptive Cruise Control (ACC) systems is a multi-layered architecture combining an application layer for ACC algorithms, core software including an operating system for task management, and hardware components like processors and memory for executing instructions and managing data. This structure enables the ECU to process sensor inputs, make real-time decisions, and control the vehicle’s speed and distance, ensuring efficient and safe ACC operation.

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Failure Analysis

Failure analysis of an Adaptive Cruise Control (ACC) system involves systematically identifying and assessing potential points of failure within the system and understanding the impact of these failures on safety and system performance. This analysis is crucial for safety assurance, as it helps engineers and safety analysts to anticipate potential hazards, mitigate risks, and ensure the system operates safely under various conditions.

Importance in Safety Assurance

Identifies Weak Points: By analyzing failures, engineers can identify vulnerabilities within the ACC system, including hardware (sensors, ECU), software (application layer, operating system), and interaction with other vehicle systems.

Informs Design Improvements: Failure analysis results can guide design improvements and the development of safer, more resilient systems.

Role of Fault Tree Analysis (FTA)

Fault Tree Analysis (FTA) is a systematic, deductive procedure used for determining the various combinations of hardware and software failures, and human errors that could lead to a particular system failure. In the context of ACC systems, FTA helps in:

Visualizing Failure Pathways: FTA provides a visual representation of the logical relationships between system failures and causes, making it easier to understand complex failure chains.

Quantifying Risk: By assigning probabilities to individual failures, FTA allows for the quantification of the overall risk of system failure, aiding in risk management and decision-making.

Prioritizing Mitigation Efforts: FTA helps identify the most critical failures that could lead to unsafe conditions, allowing teams to prioritize mitigation efforts effectively.

Safety Standard Compliance: FTA is recommended by various safety standards, such as ISO 26262 (specific to automotive systems) and IEC 61508 (for functional safety of electrical/ electronic/programmable electronic safety-related systems). These standards recognize FTA as an effective tool for identifying and analyzing system failures, helping ensure that safety-critical systems like ACC meet the required safety levels.

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RoboSafety’s PathFinder in Action

Step 1

At high-level, the ACC failure can be the result of a software failure, hardware failure or communication failure with other vehicle systems (e.g., brake actuators). We can model this situation using intuitive user interface of the PathFinder.

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Step 2

In this step we can further explore the causes related to Hardware Failure.

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Step 3 — N

In the same fashion, teams can work on different branches of the tree until system failures have been covered in sufficient details.

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PathFinder Features

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