Morse Graphs: Topological Tools for Analyzing the Global Dynamics of Robot Controllers

TL;DR

This paper introduces Morse graphs, a topological method for analyzing the global dynamics of robot controllers, enabling better understanding, safety, and synthesis of hybrid controllers through a combinatorial state space representation.

Contribution

It presents a novel topological framework using Morse graphs to analyze robot controller dynamics, outperforming existing methods in accuracy and efficiency.

Findings

Outperforms analytical and machine learning methods in estimating regions of attraction.

Provides detailed insights into global dynamics at discretization resolution.

Enables synthesis of improved hybrid controllers and identification of physical limitations.

Abstract

Understanding the global dynamics of a robot controller, such as identifying attractors and their regions of attraction (RoA), is important for safe deployment and synthesizing more effective hybrid controllers. This paper proposes a topological framework to analyze the global dynamics of robot controllers, even data-driven ones, in an effective and explainable way. It builds a combinatorial representation representing the underlying system's state space and non-linear dynamics, which is summarized in a directed acyclic graph, the Morse graph. The approach only probes the dynamics locally by forward propagating short trajectories over a state-space discretization, which needs to be a Lipschitz-continuous function. The framework is evaluated given either numerical or data-driven controllers for classical robotic benchmarks. It is compared against established analytical and recent machine learning alternatives for estimating the RoAs of such controllers. It is shown to outperform them in accuracy and efficiency. It also provides deeper insights as it describes the global dynamics up to the discretization's resolution. This allows to use the Morse graph to identify how to synthesize controllers to form improved hybrid solutions or how to identify the physical limitations of a robotic system.