Dual Stress: Runtime Safety Monitoring for Safety-Constrained MPC Navigation

2026-08-11

AI Summary

Traditional runtime hazard monitoring based on geometric metrics struggles to fully capture the implicit safety risks inherent in model predictive control (MPC). This work proposes a novel safety monitoring framework by first interpreting the KKT multipliers generated during MPC optimization as explainable “dual stress” signals, establishing a new warning dimension orthogonal to conventional geometric approaches. By fusing these dual stress signals with geometric indicators, the method constructs a multi-channel safety monitoring mechanism. Experimental results demonstrate that, at the same false alarm rate, the dual stress signal detects 4.7 times more missed collisions than geometric methods alone. Moreover, their integration enables early warning for 75% of otherwise avoidable collisions, substantially enhancing navigation safety.

Abstract

Runtime hazard monitors for autonomous naviga- tion are conventionally built from geometric quantities: predicted clearance, time to collision, and required deceleration. A model-predictive controller that enforces safety through explicit con- straints computes, as a by-product of every control step, a second information channel that such monitors ignore: the Karush-Kuhn-Tucker multipliers of its constrained optimization, which measure the marginal control effort spent to maintain safety against each obstacle. This paper evaluates whether a horizon-weighted sum of those multipliers, a dual stress signal, provides a hazard monitor complementary to the geometric warnings the same state already supports. We compare it against a battery of fifteen geometric detectors tuned to a matched false-alarm budget, on preregistered held-out crossing scenarios driven through a physics simulator. The stress alarm actionably flags 4.7 times as many collisions missed by the entire geometric battery as the geometric battery flags in return (85 versus 18); combined, the two channels warn of three quarters of the collisions for which braking remained feasible, against under half for the geometric battery alone.

Problem

• runtime safety monitoring
• safety-constrained MPC
• hazard detection
• dual stress
• collision warning

Innovation

• dual stress
• safety-constrained MPC
• KKT multipliers
• runtime hazard monitoring
• autonomous navigation