Before we dive deeper into the topic, let’s define the term functional safety, to make sure we’re on the same page. Simply said, functional safety is about ensuring the safe operation of systems even when they go wrong.In the era of digital transformation, the driving experience looks a lot more different and consumers have increasing requirements.
That’s the reason why the main challenges for the automotive industry are now their design and integration of more and more electronic systems. Modern customers look for infotainment systems that allow them to continue their usual activities while driving. Electronics lie behind every improved aspect of our vehicles. Even engines are controlled by engine management units.
However, safety has always been a main concern for the automotive industry. As tragic statistics show, nearly 1.25 million people die in road crashes each year, which means on average 3 287 deaths a day. With these numbers in mind, manufacturers constantly look for new emerging technologies that allow them to build cars with advanced functional safety.
In recent years many safety improvements are implemented in new vehicles. Some of them are pedestrian recognition, adaptive cruise control, and blind-spot monitoring. Driver assistance systems no work with analog sensor-based applications conditioned to interface with the digital world. These are playing an increasing role in driver safety systems and are just another highlight of the ever-increasing requirement of functional safety.
Electronics might help to improve our safety on the road. Nevertheless, if an electronic system like the control of the ABS fails, this would be a threat itself. This is one good reason why people still don’t trust these technologies that much. That’s where functional safety standards come in help.
Before we dive deeper into the topic, let’s define the term functional safety, to make sure we’re on the same page. Simply said, functional safety is about ensuring the safe operation of systems even when they go wrong.
There’s an internationally approved standard that guides development and sets basic minimum expectations for every industry. For automotive electronics that are ISO 26262. To be more specific, the standard defines functional safety as “the absence of unreasonable risk due to hazards caused by malfunctioning behavior of electrical/electronic systems”.
Furthermore, it’s possible to address the needs of multiple standards by identifying their requirements and adopting common principles like quality management and a focus on safety from the outset.
ISO 26262 is an international functional safety standard, which aims to provide a unifying safety for all automotive electronic and electrical safety-related systems. It’s built on IEC 61508, which is a functional safety standard developed for industrial applications, but it’s especially focused on automotive electronics and software.
IEC 61508 includes Safety Integrity Levels. There are 4 levels defined, based on the average probability of failure on demand. This essential concept was enhanced and adapted for automotive needs. However, for applications where safety requirements are not applicable, Automotive Safety Integrity Levels (ASIL) now contain the 5th level, referred to as Quality Management (QM).
The ISO 26262 international standard was improved in 2011. In fact, there are no legal requirements to comply with it, but it’s considered highly relevant.
As noted above within the standards there are different safety levels. They are defined to reflect the criticality of a function. Good examples of units that need to have higher integrity are breaks, windscreen wipers or airbags, because an unintended airbag deployment, for instance, or no vision through the windscreen could be fatal. On the other hand, parking sensors or speedometers aren’t essential for human safety, so they’d need lower integrity levels.
With the advanced driver-assistance systems and driving becoming highly autonomous, electronics assume increased control of the vehicle. That’s why the required integrity and therefore safety engineering are also rising.
In fact, the level of integrity is linked to the ability of a human to avert a dangerous situation. The functional safety standards provide guidance to qualify the level of integrity needed and metrics to quantify the integrity of systems.
ISO 26262 defines Automotive Safety Integrity Levels (ASIL) ranging from the lowest – ASIL A to the highest – ASIL D. The standard also provides metrics for single-point faults, latent faults and PMHF ( Probabilistic Measure of Hardware Failure), known as a failure in time, for ASIL B to ASIL D.
In practice, these metrics are a proposal for automotive applications. Developers can justify their own target metrics, as the objective is to enable and develop safe products, not just add bullet points to their datasheet.
Now that you know the safety integrity levels and how they work, we can classify the example we gave earlier. The braking and airbag deployment could be classified as ASIL D, while the parking sensors could go for ASIL B or even lower, depending on the overall safety case.
No matter the coverage achieved, it’s crucial to follow suitable processes when targeting functionally safe applications. That’s exactly where the approved standards come in hand. Precise development processes can improve the overall quality of a product for any use, even if the functional safety doesn’t apply.
The number of electronic complex applications in modern vehicles is constantly increasing. This makes functional safety a must. The appliance of internationally approved standards is growing in importance for vendors as well. There’s a realization that an extremely wide range of markets can benefit from more reliable systems.
Functional safety requirements in accordance with ISO 26262 affect the entire system engineering approach, all the way from the design of the ASIC through processes and quality management.
It’s essential that mechanic manufacturers and automotive software developers work closely together to ensure the optimized implementation of all safety features. The standards are a foundation upon which the automotive industry can develop systems to address the need for higher performance of cars, driver safety, fuel efficiency, comfort, and in-car infotainment .