Model Predictive Control for Signal Temporal Logic Specifications with Time Interval Decomposition

TL;DR

This paper presents a novel MPC framework for STL specifications that improves computational efficiency by decomposing the task into smaller sub-formulae with disjoint time horizons, enabling faster control synthesis.

Contribution

The paper introduces a time interval decomposition method within MPC for STL tasks, reducing computational load while maintaining formula satisfaction and recursive feasibility.

Findings

Significant reduction in computation time demonstrated in case study.

Effective terminal constraints ensure STL satisfaction across sub-formulae.

Framework applicable to complex STL specifications with large horizons.

Abstract

In this paper, we investigate the problem of Model Predictive Control (MPC) of dynamic systems for high-level specifications described by Signal Temporal Logic (STL) formulae. Recent works show that MPC has the great potential in handling logical tasks in reactive environments. However, existing approaches suffer from the heavy computational burden, especially for tasks with large horizons. In this work, we propose a computationally more efficient MPC framework for STL tasks based on time interval decomposition. Specifically, we still use the standard shrink horizon MPC framework with Mixed Integer Linear Programming (MILP) techniques for open-loop optimization problems. However, instead of applying MPC directly for the entire task horizon, we decompose the STL formula into several sub-formulae with disjoint time horizons, and shrinking horizon MPC is applied for each short-horizon sub-formula iteratively. To guarantee the satisfaction of the entire STL formula and to ensure the recursive feasibility of the iterative process, we introduce new terminal constraints to connect each sub-formula. We show how these terminal constraints can be computed by an effective inner-approximation approach. The computational efficiency of our approach is illustrated by a case study.