CAD.1:11 - SoTA-Echoing

When should the decisions be separated? The selected line derives the split from the whole problem and keeps a qualified existing loop, with a governor if needed, and a single constrained controller as serious alternatives in :4.1–4.3. Separation earns its additional interface and assurance work when differences in information, prediction horizon or execution resources prevent those simpler arrangements from meeting the same demand. If a single MPC formulation can retain the relevant coupling and meet the deadline, decomposition still has to offer a gain that outweighs maintaining its interfaces.

The method adopts the problem-decomposition and coupling-relaxation move in Matni, Ames and Doyle, §2.2, while treating its particular layer arrangement as a choice. It adapts Goel, Chen and Wierman’s construction, §§II–IV in :4.4 to include fast consequences in the slow decision. That fixed two-rate, prediction-dependent cost result does not select a layer count or cover actuator limits. The corresponding price is explicit here: a split that saves computation still owes an error and feasibility construction.

A contemporary alternative is to keep the stabilized dynamics fixed and combine online optimization of references with a governor. Nonhoff, Al Torshan and Müller, 2026 preprint, §§II–IV construct this combination for disturbed linear systems under strong convexity of the steady-state costs, compact convex constraints and their bounded-disturbance and initialization assumptions. Their performance statement concerns regret against varying optimal steady states; it is not a solution for arbitrary trajectory or mission objectives. Retain that alternative when changing costs, rather than preview-dependent motion, create the upper decision. The governor comparison in CAD.Reference:4.5.1 explains when the existing loop can remain.

Reopen the split when measured computation, required preview, available observations or permitted command distortion changes. A newly feasible single-loop or governor solution can remove the reason for a larger architecture; a missed task requirement can justify developing it.