Improved static model for pneumatic artificial muscle based on virtual work and bladder radial deformation work losses

Pipan, Miha (author), Debevec, Mihael (author), Herakovič, Niko (author)

Existing pneumatic artificial muscle (PAM) static geometrical models based on the principle of virtual work provide only approximate force predictions since they neglect the effects of volume change and radial bladder deformation work loss. In this study, we propose an improved geometrical static model called the Accurate Volume and Bladder Deformation Loss (AVBDL) model. This model introduces a physically consistent calculation of muscle volume at different contractions and pressures and incorporates a new way of describing work losses due to radial deformation of the bladder. The hyperelastic properties of the bladder were experimentally characterized and modeled using the Mooney–Rivlin formulation. The AVBDL model was validated against experimental data from four types of pneumatic muscles and compared with three established analytical models. Results show that the AVBDL model significantly improves force prediction accuracy, achieving a normalized root mean square (NRMS) error of 6.7–16.4%, compared to 20–68% for existing models. Due to its analytical transparency, reduced error, and broad applicability, the AVBDL model provides a robust basis for accurate simulation and control of pneumatic artificial muscles.

• Language: English
• Keywords: pneumatic artificial muscle, geometrical model, virtual work, hyperelasticity, volume deformation, Mooney–Rivlin model
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 17 str.
• Numbering: Vol. 14, issue. 11, art. 560
• PID: 20.500.12556/RUL-176063
• UDC: 621.86.062
• ISSN on article: 2076-0825
• DOI: 10.3390/act14110560
• COBISS.SI-ID: 257963779
• Publication date in RUL: 20.11.2025

Record is a part of a journal

• Title: Actuators
• Shortened title: Actuators
• Publisher: MDPI
• ISSN: 2076-0825
• COBISS.SI-ID: 522943513

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: pnevmatična mišica, geometrijski model, virtualno delo, hiperelastičnost, volumenska deformacija, Mooney–Rivlinov model