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How the functional safety and diagnostics works in vehicles?

ISO 26262 standard is followed for the development of safety-critical components and systems in the motor vehicle industry. It helps in identifying the hazards that can arise even in the concept phase due to the function failure. In the consecutive steps, the risks are quantified as a result, thereby, the safety requirements are assumed to be defined in a subsystem, that happened in the starting phase of the progressive process.

As per the IOS 26262 standard, the security requirements which are suitable are known initially or only partially but due to its consequences, documentation such as the Safety Manual is done based on the assumptions from the results of the safety objectives.

The technical security measures required for vehicles are summarized as the accuracy decision for the time of flight measurement based on a quartz clock system. An integrated oscillator with external and internal clock signals monitors and became a subject for frequency measurement. As a result, an approximate 3% of accuracy is secured with time reference of the system.

A large part of the digital chip area is occupied by the memory modules (RAM) and is redundantly implemented with an error correction code (ECC). One error bit per memory word is allowed to be corrected and thereby reducing the failure rate significantly.

The installation of the sequence controls and counter functions in the digital part is redundantly done. A current pulse generator was introduced for the Analog signal chain to be checked in a pulse generator for current. This generator helped in a current pulse as an input for the trans-impedance amplifier, where programming the amplitude and width are possible. In the RAM, the measured values of this current pulse are stored with the digital evaluation logic being available.

The external circuitry, in addition, can be checked with an example of detecting the short circuit as an input for the module. The internal and external supply voltages can be monitored with a voltage and temperature sensor.

The measured values are stored in built-in ADC where they can be compared with programmable digital threshold values and if there is an occurrence of an error, an external microcontroller can trigger an interruption.

Source:- http://www.iso.org, Trends in der Automobil-Sensorik

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