Fixed - Vl-022 - Forcing Function

Behind her, the intercom crackled. A voice, low and her own, whispered: “Liar.”

Before we dissect VL-022, we must anchor ourselves in the basic theory. A forcing function is a design feature or constraint that physically prevents an action from being performed incorrectly or out of sequence. Unlike a warning label or a pop-up dialog box, a forcing function does not rely on memory, vigilance, or goodwill.

The Interlock must be "fail-secure." This means if power is lost to the forcing function, the default state is . For example, a VL-022 compliant interlock on a conveyor belt uses a spring-engaged, solenoid-released brake. If the solenoid loses power, the brake engages automatically. VL-022 - Forcing Function

The Sentinel must have higher reliability than the system it protects. This often means using (e.g., one capacitive sensor, one mechanical limit switch) rather than identical sensors. The VL-022 specification requires that the Sentinel can detect its own failures.

The most cited example of a physical forcing function is the household microwave. You cannot start the microwave if the door is open. The machine physically cuts the power circuit when the latch is released. No amount of button-mashing on the keypad will generate radiation until the door is shut and latched. This is a forcing function designed for safety; it forces the user to close the door to achieve their goal, thereby preventing the error of operating the device while exposed. Behind her, the intercom crackled

The Arbiter must be deterministic and formally verifiable. Avoid machine learning for VL-022 applications unless the model can be proven to have zero false negatives. Common implementation languages include ladder logic (for PLCs) or certified C for safety-critical software.

These functions are "passive"—they exist inherently in the geometry or logic of the system. However, traditional forcing functions have a critical weakness: they cannot adapt to evolving fault conditions or multi-layered failure modes. This is where enters the arena. Unlike a warning label or a pop-up dialog

Result: Even with a broken spring, the patient does not experience a free-flow event. This design has been credited with preventing over 200 adverse events in clinical trials.

The question is no longer "Should we use a forcing function?" The question is "Is our forcing function VL-022 compliant?"