Why?

In industries like automotive, aerospace, and medical devices, safety is paramount. A malfunction in these systems can mean a serious threat to life. That’s where functional safety comes in, and at the heart of functional safety is hardware diagnostics. But what exactly are hardware diagnostics, what types of failures can occur, and why are diagnostics so crucial for system safety? Let’s dive in and explore this essential topic.

Types of Failures in Functional Safety

Before understanding how hardware diagnostics work, it’s important to know the types of failures that can occur in any HW system. Two main types of failure that can occur in a HW system are Systematic failure and Random Hardware failure.

Systematic Failures

Systematic failures occur due to design flaws, incorrect implementation, or manufacturing defects. They can affect either hardware or software.
Example a sensor in a braking system may fail consistently due to a design flaw in its wiring.
Unlike random failures, systematic failures can be eliminated through careful design, testing, and corrective measures. Diagnostics can help in detecting the recurrence of these issues.

Random Hardware Failures

Random hardware failures occur unpredictably, typically due to wear and tear, environmental factors, or unforeseen physical defects in a component.
Example, a resistor in an engine control module burns out due to prolonged heat exposure.
These failures are not consistent and are hard to anticipate, making real-time hardware diagnostics essential for detecting them.

What?

What is Hardware Diagnostics?
At its core, hardware diagnostics refers to the techniques and processes used to detect failures or faults in hardware components of a system. These diagnostics are designed to identify issues before they become critical, ensuring that systems operate safely and reliably.
Hardware diagnostics is essential in preventing hazards caused by system failures, importantly due random hardware failures. In industries like automotive or aviation, where systems must operate correctly to ensure safety, diagnostics play a vital role in maintaining reliability and avoiding potentially dangerous situations.
Why is Hardware Diagnostics Important in Functional Safety?
Imagine you’re driving a car equipped with advanced driver-assistance systems (ADAS). If the hardware components that control braking or steering fail, the results could be catastrophic. This is why hardware diagnostics are crucial in functional safety. By continuously monitoring the health of critical components, these diagnostics help detect issues early, reducing the chances of failure.
Early Failure Detection: Hardware diagnostics are like a vigilant security system for your hardware components. They identify potential issues, such as a sensor malfunction or electrical failure, before they escalate into full-blown problems.
Increased Reliability: The main goal is to ensure that systems perform their intended functions reliably, even in the presence of potential faults. Diagnostics ensure that even when something goes wrong, the system remains safe or takes necessary actions like shutting down or switching to a backup mode.
Fault Isolation: Hardware diagnostics can isolate faulty components, ensuring that only the affected part is shut down or repaired while the rest of the system keeps working efficiently.

How?

Key Elements of Hardware Diagnostics in Functional Safety

To meet the demands of functional safety standards (such as ISO 26262 for or IEC 61508), hardware diagnostics must be robust, comprehensive, and well-integrated. Here are the key elements that make up an effective hardware diagnostic system:

Fault Detection Mechanisms:
Fault detection is the first step in hardware diagnostics. The system must be capable of detecting different types of faults, some of detection mechanism are,
* Built-in self-tests (BISTs)
* Watchdog timers
* Error detection and correction codes
* Redundancy checks
Diagnostic coverage:
Diagnostic coverage refers to the effectiveness of diagnostic techniques in detecting faults within a system. It’s typically expressed as a percentage, representing the fraction of potential faults that can be identified by the diagnostic measures in place. It helps in,
* Assessing the percentage of potential faults that can be detected
* Determining diagnostic coverage for different fault types
Diagnostic test intervals:
Diagnostic test intervals refer to the frequency at which diagnostic routines are executed in a system. They are crucial for:
* Ensuring timely detection of faults
* Balancing fault detection with system performance
Safe state implementation:
Safe state implementation involves designing systems to enter a predetermined, non-hazardous condition when a fault is detected. This is critical for:
* Minimizing the risk of harm when faults occur
* Ensuring system stability during fault conditions
Redundancy and Voting Systems:
To ensure reliability, many functional safety systems employ redundancy. This means having multiple components perform the same task, and using a “voting” system to decide which component’s output to trust.
Similarly there are many other elements of Hardware Diagnostics in Functional Safety that helps increase the system reliability.

Conclusion

In today’s high-stakes industries, hardware diagnostics are non-negotiable for ensuring functional safety. They play a vital role in detecting faults, preventing catastrophic failures, and ensuring the reliability of critical systems. Whether it’s through BIST, redundancy, or ECC, implementing a robust hardware diagnostic system is key to ensuring safety and reliability.