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Spotlight Poster

Input-to-State Stable Coupled Oscillator Networks for Closed-form Model-based Control in Latent Space

Maximilian Stölzle · Cosimo Della Santina

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Thu 12 Dec 4:30 p.m. PST — 7:30 p.m. PST

Abstract:

Even though a variety of methods (e.g., RL, MPC, LQR) have been proposed in the literature, efficient and effective latent-space control of physical systems remains an open challenge.A promising avenue would be to leverage powerful and well-understood closed-form strategies from control theory literature in combination with learned dynamics, such as potential-energy shaping.We identify four fundamental shortcomings in existing latent-space models that have so far prevented this powerful combination: (i) they lack the mathematical structure of a physical system, (ii) they do not inherently conserve the stability properties of the real systems, (iii) they are too high-dimensional. Furthermore, (iv) these methods do not have an invertible mapping between input and latent-space forcing.This work proposes a novel Coupled Oscillator Network (CON) model that simultaneously tackles all these issues. More specifically, (i) we show analytically that CON is a Lagrangian system - i.e., it presses well-defined potential and kinetic energy terms. Then, (ii) we provide formal proof of global Input-to-State (ISS) stability using Lyapunov arguments.Moving to the experimental side, (iii) we demonstrate that CON reaches SoA performance when learning complex nonlinear dynamics of a continuum soft robot directly from images.An additional methodological innovation contributing to achieving this third goal is an approximated closed-form solution for efficient integration of network dynamics, which eases efficient training.We tackle (iv) by approximating the forcing-to-input mapping with a decoder that is trained to reconstruct the input based on the encoded latent space force.Finally, we leverage these four properties and show that they enable latent-space control. We use an integral-saturated PID with potential force compensation and demonstrate high-quality, out-of-the-box regulation performance of soft robots using raw pixels as the only feedback information.

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