Beyond the Control Equations: An Artifact Study of Implementation Quality in Robot Control Software

TL;DR

The paper addresses the gap between control-theoretic guarantees and their software implementations in robot controllers. It analyzes 184 controller implementations from 141 ROS-based repositories to characterize applications, implementation practices, and verification approaches. Findings show widespread ad hoc discretization, timing uncertainties, and superficially applied testing, undermining real-time reliability and theoretical guarantees. The work emphasizes the need for explicit discretization strategies, timing contracts, rigorous V&V, and better tooling to bridge theory and practice in robotics control software.

Abstract

A controller -- a software module managing hardware behavior -- is a key component of a typical robot system. While control theory gives safety guarantees for standard controller designs, the practical implementation of controllers in software introduces complexities that are often overlooked. Controllers are often designed in continuous space, while the software is executed in discrete space, undermining some of the theoretical guarantees. Despite extensive research on control theory and control modeling, little attention has been paid to the implementations of controllers and how their theoretical guarantees are ensured in real-world software systems. We investigate 184 real-world controller implementations in open-source robot software. We examine their application context, the implementation characteristics, and the testing methods employed to ensure correctness. We find that the implementations often handle discretization in an ad hoc manner, leading to potential issues with real-time reliability. Challenges such as timing inconsistencies, lack of proper error handling, and inadequate consideration of real-time constraints further complicate matters. Testing practices are superficial, no systematic verification of theoretical guarantees is used, leaving possible inconsistencies between expected and actual behavior. Our findings highlight the need for improved implementation guidelines and rigorous verification techniques to ensure the reliability and safety of robotic controllers in practice.

Figures (2)

• Figure 1: The different perspectives of control and software engineers and the associated challenges.
• Figure 2: Visualization of a control loop as a block diagram