# Shape Change and Control of Pressure-based Soft Agents

arXiv: https://arxiv.org/abs/2205.00467 · HTML: https://mlsanity.com/paper/2205.00467/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 10 of its 44 references that are in the map.
- First posted on arXiv 1 May 2022.

## Builds on (most cited first, 10 of 10)

- [The CMA Evolution Strategy: A Tutorial](https://mlsanity.com/paper/1604.00772/) (2016)
- [Evolution Gym: A Large-Scale Benchmark for Evolving Soft Robots](https://mlsanity.com/paper/2201.09863/) (2022)
- [How morphological development can guide evolution](https://mlsanity.com/paper/1711.07387/) (2017)
- [Automated shapeshifting for function recovery in damaged robots](https://mlsanity.com/paper/1905.09264/) (2019)
- [Challenges in High-dimensional Reinforcement Learning with Evolution Strategies](https://mlsanity.com/paper/1806.01224/) (2018)
- [A soft robot that adapts to environments through shape change](https://mlsanity.com/paper/2008.06397/) (2020)
- [Seeking Quality Diversity in Evolutionary Co-design of Morphology and Control of Soft Tensegrity Modular Robots](https://mlsanity.com/paper/2104.12175/) (2021)
- [Scale invariant robot behavior with fractals](https://mlsanity.com/paper/2103.04876/) (2021)
- [Bio-inspired Tensegrity Soft Modular Robots](https://mlsanity.com/paper/1703.10139/) (2017)
- [Robots: the Century Past and the Century Ahead](https://mlsanity.com/paper/2204.13331/) (2022)

## Abstract (arXiv)

Biological agents possess bodies that are mostly of soft tissues. Researchers have resorted to soft bodies to investigate Artificial Life (ALife)-related questions; similarly, a new era of soft-bodied robots has just begun. Nevertheless, because of their infinite degrees of freedom, soft bodies pose unique challenges in terms of simulation, control, and optimization. Here we propose a novel soft-bodied agents formalism, namely Pressure-based Soft Agents (PSAs): they are bodies of gas enveloped by a chain of springs and masses, with pressure pushing on the masses from inside the body. Pressure endows the agents with structure, while springs and masses simulate softness and allow the agents to assume a large gamut of shapes. Actuation takes place by changing the length of springs or modulating global pressure. We optimize the controller of PSAs for a locomotion task on hilly terrain and an escape task from a cage; the latter is particularly suitable for soft-bodied agents, as it requires the agent to contort itself to squeeze through a small aperture. Our results suggest that PSAs are indeed effective at those tasks and that controlling pressure is fundamental for shape-changing. Looking forward, we envision PSAs to play a role in the modeling of soft-bodied agents, including soft robots and biological cells. Videos of evolved agents are available at https://pressuresoftagents.github.io.