09. Warning and Degradation Concept

Warning and Degradation Concept

Summary of Warning and Degradation Concept

In functional safety, "concept" is synonymous with "document". So the warning and degradation concept would be a document that discusses:

• how the driver will be warned of a malfunction
• what the system will do to "degrade" the functionality i.e. take the system to a safe state and also recover from a safe state.

For the lane assistance item, we discussed that the driver will see a warning light on the dashboard when the system malfunctions.

The lane departure warning and lane keeping assistance functionality will degrade by turning the system off. In other words, the torque request from the lane keeping assistance will be set to zero.

Gradual Degradation versus Turning a System Off

Turning off a system entirely is not the only option, however. Some systems can provide limited functionality and "degrade" to different levels depending how bad the malfunction is. A car engine control system is one example. If one sensor fails, the engine control system might reduce the torque output of the motor so that the vehicle can still be driven but at a lower speed.

A lane departure warning system is not critical for driving a vehicle. So if the system has a malfunction, we can shut the system down; on the other hand, a functioning motor is necessary for driving a vehicle. Degrading the motor system to a safer, but functioning, state would help the driver avoid getting stranded.

Warning and Degradation Concept in the Final Project

In the final project template folder , there is a functional safety concept template file.

Near the end of the file, you will see an empty data table with the following headers:

ID, Degradation Mode, Trigger for Degradation Mode, Safe State invoked?, Driver Warning

You will be responsible for filling out this table. Degradation mode describes how the vehicle will be taken to a safe state when there is a malfunction. For the lane departure warning function, the degradation mode is to turn off the functionality. For the lane keeping assistance function, the degradation mode is the same.

What will trigger the degradation mode? The malfunctions that you have already learned about. Is the safe state invoked? Yes.

The driver warning column discusses how the driver will be warned about the malfunction.