Closed-loop CBF framework protects flight envelopes without altering control laws
Open-loop CBFs break robustness; new approach enforces safety at the reference level instead.
A team from MIT and partners introduces closed-loop model-based control barrier functions (CLM-CBF) to keep aircraft within safe flight envelopes. Traditional CBF safety filters rely on open-loop system models and modify control inputs directly, which can change closed-loop dynamics and weaken robustness guarantees. The paper shows that enforcing safety at the reference level instead—using a model of the entire closed-loop system—maintains the original controller's stability properties while still preventing violations of aerodynamic and structural constraints.
The framework is designed for modular integration: it can be layered onto existing flight control architectures as a safety filter without touching the underlying control law. This retrofitting capability is critical for aviation, where certified controllers must not be altered. The authors validate the approach against stall and load factor limits, demonstrating robust envelope protection even under uncertainty. For engineers, this means adding safety guarantees to legacy systems without a full redesign.
- CLM-CBF enforces safety at the reference level using a closed-loop model, not the control input
- Preserves stability and robustness guarantees of the existing controller, enabling retrofitting into certified flight systems
- Addresses stall and excessive load factor risks with explicit model-based filtering, validated on a flight envelope protection case study
Why It Matters
Lets aviation safety systems be retrofitted onto existing flight controllers without compromising stability—reducing stall and overload risks.