cs.ROSep 17, 2026

Constraint-Unified MPC for Over-Actuated Surface Vehicles with Post-Detection Fault Reconfiguration

Authors: Sebastian Burmester, Ruiheng Jiang, Noa Sendlhofer, Raffaello D'Andrea, Aswin Ramachandran

Organizations: Institute for Dynamic Systems and Control (IDSC), ETH Zürich, Switzerland

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Abstract

Choreographed aquatic performances require small autonomous surface vehicles to track precise paths under per-thruster force and rate limits, including after thruster failures. We report a deployed system in which trajectory tracking, thrust allocation, and the per-thruster force and rate limits are resolved in a single quadratic program over the per-thruster commands, with fault reconfiguration entering through one binary flag per thruster from an external detector. The system has driven a fleet in live performances on Lake Zürich and at the Time Space Existence 2025 exhibition in Venice. The field campaign measures 1.6 cm root mean square position error in a 10-minute hold and 4.3 cm over a 10 m square at 0.6 m/s. At 0.5 m/s, losing the front thruster increases the error to 11.6 cm, while losing the starboard-side thruster increases it to 11.5 cm. Losing two thrusters simultaneously leaves the craft tracking a 0.4 m/s square with a root mean square position error of 1.25 m. Compared to our own cascaded baseline, the unified formulation tracks the nominal square to the same few centimeters and holds station more tightly with roughly half the thruster force. The architectures separate after a thruster failure, where the unified controller stays within 24 cm of the reference path while the cascade leaves it.

Figures & tables

Figure 1: Live performance on Lake Zürich
Figure 2: Vehicle coordinates and actuation.
Massmm30.0 kg30.0\,\mathrm{kg}
Added massXu˙=Yv˙X_{\dot{u}}=Y_{\dot{v}}−12.0 kg-12.0\,\mathrm{kg}
Linear dampingXu=YvX_{u}=Y_{v}−65.0 N s m−1-65.0\,\mathrm{N\,s\,m^{-1}}
Yaw dampingNrN_{r}−3.5-3.5 / −0.35 N m s rad−1-0.35\,\mathrm{N\,m\,s\,rad^{-1}}
Combined yaw inertiaJcombJ_{\text{comb}}2.02.0 / 0.20 kg m20.20\,\mathrm{kg\,m^{2}}
Thruster moment armℓ\ell0.25 m0.25\,\mathrm{m}
Thruster command boundFmax⁡F_{\max}25 N25\,\mathrm{N}
Table 1: Vehicle and actuator parameters.
Figure 3: Mapping four control functions into one condensed QP.
Figure 4: Station keeping position error and per-thruster commands.
Figure 5: Measured trajectories for nominal and immediate-detection square experiments.
Figure 6: Per-thruster commands for nominal and immediate-detection square runs.
Figure 7: Measured trajectories for four delayed mid-lap outages.
Figure 8: Per-thruster commands for four delayed mid-lap outages.
Figure 9: Square trajectories for the MPC and cascaded baseline.
Figure 10: Per-thruster commands for the cascaded baseline.
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