EvoGymCM: Harnessing Continuous Material Stiffness for Soft Robot Co-Design

TL;DR

This paper introduces EvoGymCM, a benchmark for soft robot co-design that incorporates continuous material stiffness as a key variable, enabling more realistic and high-performing robot designs.

Contribution

It establishes a new benchmark with continuous material stiffness, proposing co-design paradigms for both programmable and traditional materials, advancing soft robot design capabilities.

Findings

Continuous material optimization improves robot performance.

Synergy between morphology, material, and control enhances design outcomes.

The benchmark supports diverse tasks with high-dimensional coupling.

Abstract

In the automated co-design of soft robots, precisely adapting the material stiffness field to task environments is crucial for unlocking their full physical potential. However, mainstream platforms (e.g., EvoGym) strictly discretize the material dimension, artificially restricting the design space and performance of soft robots. To address this, we propose EvoGymCM (EvoGym with Continuous Materials), a benchmark suite formally establishing continuous material stiffness as a first-class design variable alongside morphology and control. Aligning with real-world material mechanisms, EvoGymCM introduces two settings: (i) EvoGymCM-R (Reactive), motivated by programmable materials with dynamically tunable stiffness; and (ii) EvoGymCM-I (Invariant), motivated by traditional materials with invariant stiffness fields. To tackle the resulting high-dimensional coupling, we formulate two Morphology-Material-Control co-design paradigms: (i) Reactive-Material Co-Design, which learns real-time stiffness tuning policies to guide programmable materials; and (ii) Invariant-Material Co-Design, which jointly optimizes morphology and fixed material fields to guide traditional material fabrication. Systematic experiments across diverse tasks demonstrate that continuous material optimization boosts performance and unlocks synergy across morphology, material, and control.