Difference between failsafe and foolproof

Automotive engineering

・Running resistance

・Vehicle acceleration

・Alternator

・Fuel injection amount

・IMEP vs BMEP

・MY, CY, FY

・Turning Radius

・Roll, Pitch, Yaw

・Torque and power

・Engine vs vehicle speed

・WLTP, WLTC

・OBD

・Tire size

・Failsafe, failproof

・Water,Buttock,Transverse Line

・Gears, splines

Release date:2024/2/16　　　　　　　　　

　・In Japanese

■What is failsafe?

Failsafe is a mechanism that restores a system to a safe state even if its original functions and performance are degraded when an abnormality occurs in a system or component.

Automotive examples include

(1) The moment the throttle body becomes stuck and the car is about to go out of control, it cuts fuel and limits power output.
(2) If the radiator is clogged with debris and is about to overheat, throttle back to limit power output.

＜Latent fault is＞
A latent fault is an abnormal state in which a system or component failure does not appear in the vehicle's behavior. For example, there is a function to cut fuel as described in (1) above, but even if the fuel cut function is abnormal, you will not notice it until the throttle body breaks down. Such a failure (in this case, a failure of the fuel cut function) is called a latent fault. To detect a latent fault, take measures such as performing a fuel cut at some point and checking whether the fuel cut operates normally, even if the throttle body is not faulty.

■What is foolproof?

Foolproof is a system that eliminates insecure conditions that are not system or component malfunctions, but are caused by the misuse of the system by fools.

Automotive examples include:

(1) Detects missteps on the gas pedal and brake pedals to prevent the car from accelerating.
(2) Prevents the engine from starting unless it is in P range.
(3) Prevents shifting from P range to D range unless the brake is pressed.

Interlock is a mechanism in which a function does not become effective unless multiple independent conditions are met, as in the case of achieving (2) and (3) above. (2) is called starter interlock, and (3) is called AT interlock.

■Difference between failsafe and foolproof

As explained above, failsafe is a measure against abnormality in a system or component, and foolproof is a measure against abnormality caused by humans. Another difference is that fail-safe measures are taken after an abnormality occurs, while fool-proof measures are taken before an abnormality occurs.

Therefore, it is a failsafe to take action when a system or component breaks down due to a human anomaly.

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