Case 01
predict → observe → prove
Prove drive boundary
Engineering context. Separate run and speed request from drive ready, running, current, speed and fault feedback. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.
Controlled setup. Use the “Map mechanics” stage of the workflow: identify infeed, zones, transfers, drives, sensors, actuators and destinations. The acceptance record should show this result: a material-flow diagram names every boundary. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.
Fault challenge. Introduce or analyse “Motor command on, belt stopped” as one bounded deviation. Inspect drive ready/run, frequency, current, coupling and load The working interpretation is that the failure is beyond PLC command. The next proving action is to trace drive and mechanics. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.
Review and recovery. The most common trap here is writing code from the I/O list alone. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.
Explain it aloud: How does a PLC control a conveyor? A defensible short answer is: It evaluates commands, permissives, sensors and state, then controls starters or drives and monitors feedback.
Case 02
predict → observe → prove
Prove zone state
Engineering context. Each zone needs occupied, available, blocked, transferring and fault meaning rather than one ambiguous photoeye bit. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.
Controlled setup. Use the “Define states” stage of the workflow: specify empty, occupied, requesting, transferring, blocked and fault conditions. The acceptance record should show this result: each zone has one coherent owner. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.
Fault challenge. Introduce or analyse “Photoeye stays blocked” as one bounded deviation. Inspect product presence, alignment, contamination, wiring and input The working interpretation is that a real product and a failed sensor can look identical to logic. The next proving action is to use independent observation. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.
Review and recovery. The most common trap here is using scattered latches without a model. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.
Explain it aloud: How are products tracked? A defensible short answer is: Use ordered sensor transitions, zone state or encoder position with explicit identity and reset rules.
Case 03
predict → observe → prove
Prove product tracking
Engineering context. Identity advances only on proven transitions and must handle gaps, accumulation, reject and restart. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.
Controlled setup. Use the “Prove drive control” stage of the workflow: test ready, run, speed, stop and fault behavior. The acceptance record should show this result: command and feedback are distinct. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.
Fault challenge. Introduce or analyse “Count is wrong” as one bounded deviation. Inspect edge logic, sensor spacing, bounce and product recirculation The working interpretation is that the event definition is unstable. The next proving action is to capture transitions. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.
Review and recovery. The most common trap here is assuming output equals motion. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.
Explain it aloud: What is zero-pressure accumulation? A defensible short answer is: It controls zones so products can queue without contacting, using occupancy and downstream availability.
Case 04
predict → observe → prove
Prove routing decision
Engineering context. A diverter command depends on classification, product position, actuator readiness and destination availability. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.
Controlled setup. Use the “Track one product” stage of the workflow: advance identity on a verified sensor sequence. The acceptance record should show this result: no duplicate or lost item occurs. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.
Fault challenge. Introduce or analyse “Diverter sends wrong item” as one bounded deviation. Inspect tracking index, classification timing, position and actuator feedback The working interpretation is that identity and physical product lost synchronization. The next proving action is to replay one item slowly. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.
Review and recovery. The most common trap here is incrementing on a held level. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.
Explain it aloud: How do you detect a conveyor jam? A defensible short answer is: Define an expected sensor or motion transition within a bounded time while the drive is commanded.
Case 05
predict → observe → prove
Prove jam detection
Engineering context. Use an expected transition and a time or motion boundary, not simply a sensor that remains on. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.
Controlled setup. Use the “Test accumulation” stage of the workflow: block downstream and fill zones deliberately. The acceptance record should show this result: transfers stop without collisions. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.
Fault challenge. Introduce or analyse “Zones collide” as one bounded deviation. Inspect downstream-available contract and transfer ownership The working interpretation is that two zones may command the same space. The next proving action is to centralize arbitration. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.
Review and recovery. The most common trap here is testing only free-flow production. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.
Explain it aloud: Why use a VFD on a conveyor? A defensible short answer is: It can provide controlled speed, acceleration, deceleration and diagnostics when appropriate to the mechanical system.
Case 06
predict → observe → prove
Prove restart policy
Engineering context. Reconcile product positions and downstream capacity before restoring automatic flow. Begin with a written normal condition and identify which request, state, physical result or communication value will provide independent confirmation. Do not begin by changing the configuration; the initial state is part of the evidence and should remain reproducible.
Controlled setup. Use the “Recover a jam” stage of the workflow: remove cause, inspect positions, reset and restart one transfer at a time. The acceptance record should show this result: state and physical products agree. Record initial conditions, the exact stimulus and the observation point so another learner can repeat the case without relying on your memory.
Fault challenge. Introduce or analyse “Jam returns after reset” as one bounded deviation. Inspect root cause, retained product state and timeout trigger The working interpretation is that reset removed indication but not cause. The next proving action is to prove motion before clearing. Change only one condition before observing the result, and preserve timestamps or measurements where timing matters.
Review and recovery. The most common trap here is clearing every bit blindly. After restoring the cause, repeat the normal case and at least one stop, timeout, disconnect or restart boundary relevant to this topic. Remove temporary forces and bypasses, return the model to a known state and retain the evidence that both operation and recovery are deliberate.
Explain it aloud: How should a diverter be interlocked? A defensible short answer is: Require correct product position, destination availability, actuator readiness and feedback before transfer.
