ROTEC: Robust to Early Termination Command Governor for Systems with Limited Computing Capacity

TL;DR

This paper introduces a robust command governor that ensures constraint enforcement in embedded systems with limited computing resources by embedding the optimization into a virtual dynamical system, enabling real-time feasible solutions.

Contribution

It develops a virtual dynamical system approach for command governors that guarantees constraint satisfaction despite early termination due to limited computation time.

Findings

Effective in maintaining constraint satisfaction under early termination.

Suitable for systems with limited computational resources.

Validated through vehicle rollover simulations.

Abstract

A Command Governor (CG) is an optimization-based add-on scheme to a nominal closed-loop system. It is used to enforce state and control constraints by modifying reference commands. This paper considers the implementation of a CG on embedded processors that have limited computing resources and must execute multiple control and diagnostics functions; consequently, the time available for CG computations is limited and may vary over time. To address this issue, a robust to early termination command governor is developed which embeds the solution of a CG problem into the internal states of a virtual continuous-time dynamical system which runs in parallel to the process. This virtual system is built so that its trajectory converges to the optimal solution (with a tunable convergence rate), and provides a sub-optimal but feasible solution whenever its evolution is terminated. This allows the designer to implement a CG strategy with a small sampling period (and consequently with a minimum degradation in its performance), while maintaining its constraint-handling capabilities. Simulations are carried out to assess the effectiveness of the developed scheme in satisfying performance requirements and real-time schedulability conditions for a practical vehicle rollover example.