pith. sign in

arxiv: 2605.21031 · v2 · pith:NGPU7NR5new · submitted 2026-05-20 · 💻 cs.RO

Modeling and Control of a Pneumatic Morphing Soft Quadrotor based on the SOFA Framework for Dynamic Soft Robotic Simulation

Pith reviewed 2026-05-25 06:16 UTC · model grok-4.3

classification 💻 cs.RO
keywords soft roboticsquadrotorfinite element methodpneumatic actuationSOFA frameworkmorphingdynamic simulationcontrol
0
0 comments X

The pith

A SOFA-based finite element method models pneumatic morphing soft quadrotor arms while preserving traditional quadrotor dynamics.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper develops a simulation framework for a quadrotor with soft pneumatic arms that can change shape. It applies finite element analysis inside the SOFA environment to represent the arms as meshes whose internal forces come from an elastic material law. The approach keeps the standard physical equations and control laws of rigid quadrotors unchanged. Pneumatic pressure is applied inside arm cavities and a proportional-integral controller is used to drive the arms to target positions. Simulation tests show the model can handle both periodic actuation and closed-loop position commands.

Core claim

The proposed SOFA based finite element method for the soft body modeling preserves the physical interpretability and control structure of traditional quadrotor dynamics, while capturing the complex, time-varying behavior of pneumatically actuated soft arms. In SOFA, the soft pneumatically actuated arms are discretized as a tetrahedral mesh following an elastic material law that produces internal forces adequate to the real dynamic behavior of the body. Pneumatic actuation governed by both periodic and error-based control signals is applied within the internal cavities to analyze the morphing capability. A proportional-integral controller is proposed to study the controlled dynamic behavior.

What carries the argument

SOFA-based finite element discretization of soft arms as tetrahedral meshes under an elastic material law that computes internal forces and accepts pneumatic actuation inputs.

Load-bearing premise

The tetrahedral mesh discretization following an elastic material law produces internal forces adequate to the real dynamic behavior of the pneumatic arms.

What would settle it

Quantitative comparison of simulated arm tip positions and deformation shapes against measurements from a physical pneumatic prototype driven by the same pressure signals.

Figures

Figures reproduced from arXiv: 2605.21031 by B. Vanderborght, F. Labra Caso, G. Nikolakopoulos, J. Haluska, P. Ferrentino, V. Sumathy.

Figure 1
Figure 1. Figure 1: Visualization of the presented morphing pneumatic quadrotor design in SOFA at initial state (b) and during [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Overview of the components in a SOFA scene [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Soft Morphing Quadrotor at initial state (a) and during actuation (b). The Soft Pneumatic Arms connect [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: (a) The different parts of the UAV arm modelled in SOFA. The pneumatic actuator (white), the pneumatic [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Experimental setup of the periodic control for [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Pneumatic actuation effect under the passive [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 8
Figure 8. Figure 8: Experimental setup of the pressure controller [PITH_FULL_IMAGE:figures/full_fig_p006_8.png] view at source ↗
Figure 10
Figure 10. Figure 10: Distributed control signal i.e. individual cavity pressure for every quadrant experiment [PITH_FULL_IMAGE:figures/full_fig_p007_10.png] view at source ↗
read the original abstract

This article presents a novel SOFA based finite element method for the soft body modeling and the corresponding dynamic simulation and control of a pneumatic morphing soft quadrotor. The proposed modeling preserves the physical interpretability and control structure of traditional quadrotor dynamics, while capturing the complex, time-varying behavior of pneumatically actuated soft arms. In SOFA, the soft pneumatically actuated arms are discretized as a tetrahedral mesh following an elastic material law that produces internal forces adequate to the real dynamic behavior of the body. Pneumatic actuation governed by both periodic and error-based control signals is applied within the internal cavities to analyze the morphing capability. Finally, a proportional-integral controller is proposed to study the controlled dynamic behavior and morphing capabilities of the pneumatic arm, wherein the pneumatic actuation to the soft arm is controlled to achieve the desired target position. The simulation results show the effectiveness of the proposed novel modeling framework and the related controller design.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper presents a SOFA-based finite element method for modeling the soft pneumatically actuated arms of a morphing quadrotor as tetrahedral meshes obeying elastic material laws. Pneumatic actuation is applied via periodic and error-based signals inside the cavities; a standard PI controller is used to drive the arms to target positions. The central claim is that this discretization preserves the physical interpretability and control structure of rigid quadrotor dynamics while capturing the time-varying soft-body behavior, with simulation results asserted to demonstrate effectiveness.

Significance. If the tetrahedral-mesh model were shown to reproduce measured pneumatic-arm dynamics, the framework could supply a reusable simulation environment for controller synthesis on soft aerial robots. The retention of conventional quadrotor control structure is a modest conceptual advantage, but the work relies entirely on internal simulation outputs under an unvalidated constitutive law and supplies no quantitative metrics or comparisons.

major comments (2)
  1. [Modeling description] Modeling description (abstract and § on SOFA discretization): the assertion that the tetrahedral mesh with elastic material law 'produces internal forces adequate to the real dynamic behavior of the pneumatic arms' is stated without any supporting evidence. No experimental tip trajectories, force measurements, or parameter-identification procedure from physical prototypes is described; all reported results remain internal to the assumed model.
  2. [Simulation results] Simulation results paragraph (abstract): the statement that 'simulation results show the effectiveness of the proposed novel modeling framework and the related controller design' is unsupported by any quantitative metrics, error norms, convergence times, baseline comparisons (e.g., rigid-body model or alternative soft-body formulations), or statistical measures. This leaves the central claim of demonstrated effectiveness without measurable grounding.
minor comments (1)
  1. [Modeling] Clarify the mesh resolution (number of tetrahedra, element size) and the specific elastic constitutive parameters employed, as these directly affect reproducibility of the reported trajectories.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive feedback on our manuscript. We address each major comment point by point below, indicating planned revisions where appropriate.

read point-by-point responses
  1. Referee: [Modeling description] Modeling description (abstract and § on SOFA discretization): the assertion that the tetrahedral mesh with elastic material law 'produces internal forces adequate to the real dynamic behavior of the pneumatic arms' is stated without any supporting evidence. No experimental tip trajectories, force measurements, or parameter-identification procedure from physical prototypes is described; all reported results remain internal to the assumed model.

    Authors: We acknowledge that the manuscript provides no experimental data, tip trajectories, or parameter identification from physical prototypes to support the claim of adequacy to real dynamic behavior. The tetrahedral discretization follows standard elastic material laws implemented in SOFA, which are established for soft-body approximation in the framework. We will revise the abstract and modeling section to qualify the statement, noting that the model relies on these constitutive laws and that direct experimental validation lies outside the current simulation-focused scope. revision: partial

  2. Referee: [Simulation results] Simulation results paragraph (abstract): the statement that 'simulation results show the effectiveness of the proposed novel modeling framework and the related controller design' is unsupported by any quantitative metrics, error norms, convergence times, baseline comparisons (e.g., rigid-body model or alternative soft-body formulations), or statistical measures. This leaves the central claim of demonstrated effectiveness without measurable grounding.

    Authors: We agree that the current presentation of simulation results lacks quantitative metrics, error norms, convergence times, and baseline comparisons. In the revised manuscript we will expand the results section to include position-tracking error norms, settling times, and direct comparisons against a rigid-body quadrotor model under equivalent actuation, thereby supplying measurable support for the effectiveness claims. revision: yes

standing simulated objections not resolved
  • Absence of experimental validation against physical prototypes, as the work is confined to internal simulation outputs within the SOFA framework.

Circularity Check

0 steps flagged

No significant circularity in derivation chain

full rationale

The paper's core modeling uses standard tetrahedral FEM discretization with elastic material laws inside the external SOFA framework, followed by a conventional PI controller. No equations, parameters, or predictions are shown to reduce by construction to quantities defined within the paper itself (e.g., no fitted inputs renamed as predictions, no self-definitional loops, and no load-bearing self-citations that substitute for independent justification). The assertion that internal forces are 'adequate to the real dynamic behavior' is an unsupported modeling premise rather than a derived result that collapses to the inputs. The derivation chain remains self-contained against external benchmarks and does not exhibit the enumerated circularity patterns.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the domain assumption that the chosen elastic material law and tetrahedral discretization capture real pneumatic arm dynamics; no explicit free parameters or invented entities are stated in the abstract.

axioms (1)
  • domain assumption The tetrahedral mesh discretization following an elastic material law produces internal forces adequate to the real dynamic behavior of the pneumatic arms.
    This premise is invoked directly in the description of the soft-body modeling approach.

pith-pipeline@v0.9.0 · 5721 in / 1215 out tokens · 50427 ms · 2026-05-25T06:16:19.842987+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

25 extracted references · 25 canonical work pages

  1. [1]

    Review of biomimetic approaches for drones.Drones, 6(11):320, 2022

    Saori Tanaka, Abner Asignacion, Toshiyuki Nakata, Satoshi Suzuki, and Hao Liu. Review of biomimetic approaches for drones.Drones, 6(11):320, 2022

  2. [2]

    Land- ing and take-off capabilities of bioinspired aerial ve- hicles: A review.Bioinspiration & Biomimetics, 19(3):031001, 2024

    Ahmad Hammad and Sophie F Armanini. Land- ing and take-off capabilities of bioinspired aerial ve- hicles: A review.Bioinspiration & Biomimetics, 19(3):031001, 2024

  3. [3]

    A soft drone with multi-modal mobil- ity for the exploration of confined spaces

    Amedeo Fabris, Steffen Kirchgeorg, and Stefano Mintchev. A soft drone with multi-modal mobil- ity for the exploration of confined spaces. In2021 IEEE International Symposium on Safety, Security, and Rescue Robotics (SSRR), pages 48–54, 2021

  4. [4]

    F. Ruiz, B. C. Arrue, and A. Ollero. Sophie: Soft and flexible aerial vehicle for physical interaction with the environment.IEEE Robotics and Automa- tion Letters, 7(4):11086–11093, 2022

  5. [5]

    Metamorphic aerial robot capable of mid-air shape morphing for rapid perching.Scientific Reports, 13(1):1297, 2023

    Peter Zheng, Feng Xiao, Pham Huy Nguyen, An- dre Farinha, and Mirko Kovac. Metamorphic aerial robot capable of mid-air shape morphing for rapid perching.Scientific Reports, 13(1):1297, 2023

  6. [6]

    Embodying compliant touch on drones for aerial tactile navigation.IEEE Robotics and Automation Letters, 2024

    Anton Bredenbeck, Cosimo Della Santina, and Salua Hamaza. Embodying compliant touch on drones for aerial tactile navigation.IEEE Robotics and Automation Letters, 2024

  7. [7]

    Hiu Ching Cheung, Ching-Wei Chang, Bailun Jiang, Chih-Yung Wen, and Henry K. Chu. A modular pneumatic soft gripper design for aerial grasping and landing. In2024 IEEE 7th International Conference on Soft Robotics (RoboSoft), pages 82–88, 2024

  8. [8]

    Soft pneumatic helical actuators with programmable variable curvatures.IEEE Robotics and Automation Letters, 2024

    Zefeng Xu, Jiaqiao Liang, and Yitong Zhou. Soft pneumatic helical actuators with programmable variable curvatures.IEEE Robotics and Automation Letters, 2024. 7 ARXIVPREPRINT05-2026

  9. [9]

    Morphing quadrotors: Enhancing versatility and adaptability in drone applications—a review.Drones (2504-446X), 8(12), 2024

    Siyuan Xing, Xuhui Zhang, Jiandong Tian, Chun- lei Xie, Zhihong Chen, and Jianwei Sun. Morphing quadrotors: Enhancing versatility and adaptability in drone applications—a review.Drones (2504-446X), 8(12), 2024

  10. [10]

    Bioinspired hydro- gel actuator for soft robotics: Opportunity and chal- lenges.Nano Today, 49:101764, 2023

    Yunrui Chen, Yabin Zhang, Hongyuan Li, Jie Shen, Fangfei Zhang, Jiajun He, Junzhu Lin, Ben Wang, Shichao Niu, Zhiwu Han, et al. Bioinspired hydro- gel actuator for soft robotics: Opportunity and chal- lenges.Nano Today, 49:101764, 2023

  11. [11]

    Soft robots modeling: A structured overview.IEEE Transactions on Robotics, 39(3):1728–1748, 2023

    Costanza Armanini, Fr ´ed´eric Boyer, Anup Teejo Mathew, Christian Duriez, and Federico Renda. Soft robots modeling: A structured overview.IEEE Transactions on Robotics, 39(3):1728–1748, 2023

  12. [12]

    A concise guide to modelling the physics of embod- ied intelligence in soft robotics.Nature Reviews Physics, 4(9):595–610, 2022

    Gianmarco Mengaldo, Federico Renda, Steven L Brunton, Moritz B¨acher, Marcello Calisti, Christian Duriez, Gregory S Chirikjian, and Cecilia Laschi. A concise guide to modelling the physics of embod- ied intelligence in soft robotics.Nature Reviews Physics, 4(9):595–610, 2022

  13. [13]

    Model-based control of soft robots: A survey of the state of the art and open chal- lenges.IEEE Control Systems Magazine, 43(3):30– 65, 2023

    Cosimo Della Santina, Christian Duriez, and Daniela Rus. Model-based control of soft robots: A survey of the state of the art and open chal- lenges.IEEE Control Systems Magazine, 43(3):30– 65, 2023

  14. [14]

    Control strategies for soft robot systems.Advanced Intelligent Systems, 4(5):2100165, 2022

    Jue Wang and Alex Chortos. Control strategies for soft robot systems.Advanced Intelligent Systems, 4(5):2100165, 2022

  15. [15]

    Decade of bio-inspired soft robots: A review.Smart Materials and Structures, 31(7):073002, 2022

    Faheem Ahmed, Muhammad Waqas, Bushra Jawed, Afaque Manzoor Soomro, Suresh Kumar, Ashraf Hina, Umair Khan, Kyung Hwan Kim, and Kyung Hyun Choi. Decade of bio-inspired soft robots: A review.Smart Materials and Structures, 31(7):073002, 2022

  16. [16]

    An overview of soft robotics.Annual Review of Control, Robotics, and Autonomous Systems, 6(1):1–29, 2023

    Oncay Yasa, Yasunori Toshimitsu, Mike Y Miche- lis, Lewis S Jones, Miriam Filippi, Thomas Buch- ner, and Robert K Katzschmann. An overview of soft robotics.Annual Review of Control, Robotics, and Autonomous Systems, 6(1):1–29, 2023

  17. [17]

    Data-driven methods applied to soft robot modeling and control: A review.IEEE Transactions on Au- tomation Science and Engineering, 2024

    Zixi Chen, Federico Renda, Alexia Le Gall, Lorenzo Mocellin, Matteo Bernabei, Th ´eo Dangel, Gas- tone Ciuti, Matteo Cianchetti, and Cesare Stefanini. Data-driven methods applied to soft robot modeling and control: A review.IEEE Transactions on Au- tomation Science and Engineering, 2024

  18. [18]

    Finite element analysis-based soft robotic modeling: Simulating a soft actuator in sofa.IEEE robotics & automation magazine, 31(3):97–105, 2023

    Pasquale Ferrentino, Ellen Roels, Joost Brancart, Seppe Terryn, Guy Van Assche, and Bram Vander- borght. Finite element analysis-based soft robotic modeling: Simulating a soft actuator in sofa.IEEE robotics & automation magazine, 31(3):97–105, 2023

  19. [19]

    Quasi-static fea model for a multi- material soft pneumatic actuator in sofa.IEEE Robotics and Automation Letters, 7(3):7391–7398, 2022

    Pasquale Ferrentino, Antonio Lopez-Diaz, Seppe Terryn, Julie Legrand, Joost Brancart, Guy Van Ass- che, Ester Vazquez, Andres Vazquez, and Bram Vanderborght. Quasi-static fea model for a multi- material soft pneumatic actuator in sofa.IEEE Robotics and Automation Letters, 7(3):7391–7398, 2022

  20. [20]

    Finite element dynamics of a concentric tube robot motion and in- teraction with environment using sofa-framework

    Katie Zuo, Benjamin Jackson, Ross Henry, Chris- tos Bergeles, and SM Hadi Sadati. Finite element dynamics of a concentric tube robot motion and in- teraction with environment using sofa-framework. Young, 2000(134):77, 2022

  21. [21]

    An open-source user-friendly interface for simulating magnetic soft robots using simulation open framework architec- ture (sofa).arXiv preprint arXiv:2508.10686, 2025

    Carla Wehner, Finn Schubert, Heiko Hellkamp, Julius Hahnewald, Kilian Schaefer, Muhammad Bi- lal Khan, and Oliver Gutfleisch. An open-source user-friendly interface for simulating magnetic soft robots using simulation open framework architec- ture (sofa).arXiv preprint arXiv:2508.10686, 2025

  22. [22]

    Development of a ppo- reinforcement learned walking tripedal soft-legged robot using sofa.arXiv preprint arXiv:2504.09242, 2025

    Yomna Mokhtar, Tarek Shohdy, Abdallah A Has- san, Mostafa Eshra, Omar Elmenawy, Osama Khalil, and Haitham El-Hussieny. Development of a ppo- reinforcement learned walking tripedal soft-legged robot using sofa.arXiv preprint arXiv:2504.09242, 2025

  23. [23]

    Soft pneumatic actuated morphing quadrotor: Design and devel- opment

    Jakub Halu ˇska, Jim V ¨astan¨alv, Andreas Papadim- itriou, and George Nikolakopoulos. Soft pneumatic actuated morphing quadrotor: Design and devel- opment. In2022 30th Mediterranean Conference on Control and Automation (MED), pages 475–480, 2022

  24. [24]

    Sofa: A multi-model framework for interactive physical simulation

    Franc ¸ois Faure, Christian Duriez, Herv´e Delingette, J´er´emie Allard, Benjamin Gilles, St ´ephanie Marchesseau, Hugo Talbot, Hadrien Courtecuisse, Guillaume Bousquet, Igor Peterlik, et al. Sofa: A multi-model framework for interactive physical simulation. InSoft tissue biomechanical modeling for computer assisted surgery, pages 283–321. Springer, 2012

  25. [25]

    Fea-based inverse kine- matic control: Hyperelastic material characteriza- tion of self-healing soft robots.IEEE Robotics & Automation Magazine, 29(3):78–88, 2021

    Pasquale Ferrentino, Seyedreza Kashef Tabrizian, Joost Brancart, Guy Van Assche, Bram Vander- borght, and Seppe Terryn. Fea-based inverse kine- matic control: Hyperelastic material characteriza- tion of self-healing soft robots.IEEE Robotics & Automation Magazine, 29(3):78–88, 2021. 8