Functional safety (FuSi) is a sub-area of the security of a system. It refers to the Correct function of the safety-related system and other risk-mitigating measures.
Electrical safety, fire protection or radiation protection are therefore not part of functional safety. Alternatively, one often speaks of Security integrity of the systemas safety can also be achieved through emergency shutdown and the assumption of a safe state. Functional safety may therefore also be ensured if the system no longer performs its intended function and is switched off.
The complexity of electronic and, in particular, programmable systems increases the variety of possible errors: Microcontrollers now perform almost all safety functions.
For example, they ensure that the temperature in a chemical production step remains constant, guide trains onto the right tracks at the right speed or prevent airbags from being deployed at the wrong moment.
The various aspects of functional safety are described in the IEC 61508 series of standards "Functional safety of electrical/electronic/programmable electronic safety-related systems" defined. They range from concept, planning, development and implementation through commissioning, maintenance and modification to decommissioning and deinstallation. The following methods for fault prevention are mentioned, among others:
- Avoidance of systematic errors in development, e.g. specification and implementation errors
- Detection of random faults (e.g. ageing of components) by monitoring during operation
- Safe control of recognized errors and transition to a state previously defined as safe.
Legal safety requirements
Customers and users have high expectations when it comes to product safety. In addition, minimizing risks is a general goal of society.
In Germany, politicians therefore introduced the Product Safety Act (ProdSG, until December 2011: GPSG) has created a legal framework for the implementation of safety requirements.
The avoidance of systematic errors and the control of systematic and random errors in "safety-related functions" reduces the expected risk to an acceptable level.
Important functional safety standards
The following standards are particularly relevant for functional safety (FuSi):
- EN ISO 13849: Safety of machinery - Safety-related parts of control systems
- EN/IEC 61508: Functional safety of electrical/electronic/programmable electronic safety-related systems
- EN/IEC 61511: Functional safety - Safety instrumented systems for the process industry
- EN/IEC 62061: Safety of machinery - Functional safety of electrical, electronic and programmable electronic safety-related control systems
- ISO 26262: Functional safety for road vehicles
Series of standards for motor vehicles: ISO 26262
An adaptation of this series of standards for motor vehicles is the Standard ISO 26262 ("Functional safety for road vehicles"). This was published in November 2011 and has since been enshrined in law.
Today's cars contain an ever-increasing number of electronic components and control units. In addition, the networking of the individual components with each other is also constantly increasing. As a result, the complexity of development is constantly increasing and is therefore subject to strict legal control in order to comply with the functional safety regulations according to ProdSG. Current trends such as autonomous driving and the introduction of more and more digital assistance systems continue to fuel the need for functional safety.
A simple example of functional safety in a car is the electronic stability program (ESP). The system looks at driving behavior and assesses the risk of the car skidding. If, for example, a bend is entered too quickly, an accident could occur and the system must therefore intervene, as an accident is an intolerable risk. It may not be possible to prevent a skid completely, but ESP can limit the risk of an accident to an acceptable level.
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