⚠ Failure Modes Addressed by Design Recovery Control (DRC)
🎯 Purpose
This document defines which failure modes are explicitly addressed
by Design Recovery Control (DRC)
and which are explicitly out of scope.
Its purpose is to prevent misinterpretation of DRC
as a general-purpose fault recovery, adaptive control,
or AI-based control framework.
🔑 Fundamental Distinction
Design Recovery Control addresses design assumption failures,
not physical or execution failures.
A failure mode is considered within the scope of DRC only if:
- ⚙ The physical system remains operational
- ⏱ Control execution is still possible
- 🛡 Safety mechanisms remain intact
- 📐 Original control design assumptions are no longer valid
If any of the above conditions are not satisfied,
the failure is outside the scope of DRC.
✅ Failure Modes Addressed by DRC
1️⃣ Control Design Assumption Drift
Description
- Gradual mismatch between assumed and actual system behavior
- No single catastrophic event
- Degradation accumulates over time
Examples
- PID gains tuned for outdated dynamics
- Environmental conditions exceeding original assumptions
- Aging effects altering response characteristics
Why DRC Applies
- Control execution remains correct
- Design parameters and assumptions are no longer valid
2️⃣ Mode Boundary Misalignment
Description
- FSM mode boundaries no longer reflect actual operating regions
- Excessive or oscillatory mode transitions occur
Examples
- Nominal ↔ degraded mode chattering
- Safety margins triggered too early or too late
Why DRC Applies
- FSM structure is sound
- Transition conditions are misaligned with reality
(Non-Catastrophic)
Description
- Output quality or response time degrades
- System remains stable and controllable
Examples
- Increased settling time
- Overshoot beyond expected margins
- Reduced tracking accuracy
Why DRC Applies
- Control loops execute correctly
- Design expectations are violated
4️⃣ Incomplete or Obsolete Design Knowledge
Description
- Original design lacks coverage for newly observed behaviors
- Edge cases emerge during long-term operation
Examples
- New operating regimes due to usage changes
- Previously unseen interaction effects
Why DRC Applies
- Design documentation and assumptions require update
- This is a design deficiency, not a runtime fault
🚫 Failure Modes Explicitly NOT Addressed by DRC
❌ 1. Physical Component Failure
Examples
- Actuator failure
- Sensor loss or corruption
- Structural damage
- Electrical short or open circuits
Handled By
- Fault detection and isolation (FDI)
- Hardware redundancy
- Maintenance and repair processes
❌ 2. Real-Time Control Instability
Examples
- Unstable control loops
- Missed deadlines
- Numerical overflow
- Timing violations
Handled By
- Control design and validation
- Real-time systems engineering
- FSM safety intervention
❌ 3. Safety-Critical Emergencies
Examples
- Runaway conditions
- Hard safety limit violations
- Immediate hazard states
Handled By
- FSM emergency states
- Hardware interlocks
- Emergency shutdown procedures
🚫 DRC must never intervene in these cases.
❌ 4. Reliability or Lifetime Optimization
Examples
- Stress minimization
- Wear balancing
- Energy efficiency optimization
Handled By
- Reliability engineering
- Lifetime management frameworks
❌ 5. Autonomous Self-Learning Control
Examples
- Online reinforcement learning
- Continuous adaptive control
- Self-modifying control logic
🚫 Explicitly excluded from DRC.
📊 Failure Classification Summary
| Failure Type |
Addressed by DRC |
| Design assumption drift |
✅ Yes |
| Mode boundary misalignment |
✅ Yes |
| Gradual performance collapse |
✅ Yes |
| Physical component failure |
❌ No |
| Real-time instability |
❌ No |
| Safety emergencies |
❌ No |
| Reliability optimization |
❌ No |
| Autonomous AI control |
❌ No |
🔒 Design Intent Freeze
This document fixes the definition of failure modes
that fall within the authority of Design Recovery Control.
Any system claiming to implement DRC
must not extend its authority beyond these boundaries.
⚖ Legal and Safety Notice
Misclassifying physical failures, execution faults,
or safety-critical emergencies
as design recovery problems
constitutes a violation of the DRC concept.
End of document.