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14 pages, 6986 KB

Open AccessArticle

A Biomimetic Soft Robot for In-Pipe Inspection: Design, Development, and Experimental Validation

by Leonarda Došen, Jan Pelić, Goran Gregov and Ervin Kamenar

Actuators 2026, 15(8), 435; https://doi.org/10.3390/act15080435 - 11 Aug 2026

Viewed by 422

Abstract

Soft robots are particularly suitable for in-pipe inspection, where locomotion must be achieved within confined, curved, and geometrically constrained environments without damaging the pipe wall. In this context, structural compliance is not only a safety feature but also a functional design principle, enabling [...] Read more.

Soft robots are particularly suitable for in-pipe inspection, where locomotion must be achieved within confined, curved, and geometrically constrained environments without damaging the pipe wall. In this context, structural compliance is not only a safety feature but also a functional design principle, enabling the robot to adapt to the pipe geometry, maintain distributed contact, and generate locomotion through controlled anchoring and extension–contraction cycles. This study presents the design, fabrication, and experimental validation of an earthworm-inspired soft pneumatic robot for in-pipe inspection. The robot uses inflatable anchoring elements for alternating radial anchoring and pneumatic bellows actuators for extension–contraction cycles, enabling locomotion while maintaining stable contact with the pipe wall. A laboratory-scale prototype was fabricated using additive manufacturing and evaluated with a dedicated pneumatic and control system. Experiments were conducted to determine locomotion performance, operating pressures, actuation timing, friction characteristics, bend negotiation, and load capacity. The optimal anchoring pressure was only 0.1 bar, demonstrating that reliable contact with the pipe wall can be achieved at a very low pneumatic pressure. The robot achieved average locomotion speeds of 21.07 mm/s in horizontal and 20.59 mm/s in vertical PVC pipes, successfully traversed a 90° pipe bend, and demonstrated a maximum vertical load capacity of 1.2 kg. These results demonstrate the feasibility of the proposed biomimetic soft robotic concept for in-pipe inspection and provide a basis for future development toward autonomous operation and industrially relevant testing. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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26 pages, 13074 KB

Open AccessArticle

A Wearable Lower-Limb Exoskeleton with Sensor-Driven Neuro-Fuzzy Control for Monoplegia Rehabilitation

by Paraskevi Zacharia, Kyriakos Deliparaschos, Vasileios D. Sagias and Constantinos Stergiou

Actuators 2026, 15(7), 359; https://doi.org/10.3390/act15070359 - 30 Jun 2026

Cited by 1 | Viewed by 361

Abstract

This study presents the design and development of a wearable lower-limb exoskeleton system aimed at supporting motion assistance in monoplegia-related conditions. The proposed approach integrates a simplified sensing configuration with a data-driven neuro-fuzzy control framework based on an Adaptive Neuro-Fuzzy Inference System (ANFIS). [...] Read more.

This study presents the design and development of a wearable lower-limb exoskeleton system aimed at supporting motion assistance in monoplegia-related conditions. The proposed approach integrates a simplified sensing configuration with a data-driven neuro-fuzzy control framework based on an Adaptive Neuro-Fuzzy Inference System (ANFIS). Motion data are acquired from the healthy limb using bend flex sensors and are used to generate control signals for the actuation of the impaired limb through an Arduino-based embedded platform. The mechanical structure is developed using a lightweight 3D-printed design combined with high-torque DC motors and gear transmission mechanisms. Experimental evaluation conducted under controlled conditions demonstrates that the system is capable of capturing and reproducing fundamental motion patterns, with the ANFIS model providing a consistent mapping between sensor inputs and actuator responses. The obtained results indicate a satisfactory level of performance for motion pattern reproduction, particularly in terms of temporal behavior and transition between movement states. The presented system emphasizes low-cost implementation, computational efficiency, and practical implementation, making it suitable as a proof-of-concept framework for wearable assistive technologies. While the results demonstrate the feasibility of the proposed approach for motion reproduction, further studies involving extended testing and user-specific adaptation are required to assess its potential applicability in real-world scenarios. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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17 pages, 6796 KB

Open AccessArticle

Design and Modeling of a Bidirectional Origami-Inspired Soft Pneumatic Actuator

by Alireza Keramati, Alireza Mohammadi, Ying Tan, Peter Choong and Denny Oetomo

Actuators 2026, 15(6), 320; https://doi.org/10.3390/act15060320 - 6 Jun 2026

Viewed by 484

Abstract

Soft pneumatic actuators (SPAs) are widely used in applications requiring safe and compliant interaction; however, achieving bidirectional motion within a compact and predictable architecture remains a key challenge. Existing approaches typically rely on antagonistic actuator pairs or multi-chamber designs, which increase system complexity [...] Read more.

Soft pneumatic actuators (SPAs) are widely used in applications requiring safe and compliant interaction; however, achieving bidirectional motion within a compact and predictable architecture remains a key challenge. Existing approaches typically rely on antagonistic actuator pairs or multi-chamber designs, which increase system complexity and control requirements, while single-chamber solutions often lack robust analytical models to predict their mechanical response. In this work, a Bidirectional Origami-Inspired Soft Pneumatic Actuator (Bi-OSPA) is proposed to achieve both elongation and contraction within a single-chamber structure, where the direction of motion is governed solely by the applied pressure (vacuum or positive). The actuator leverages origami-inspired geometry, allowing deformation to be primarily described through folding kinematics, which facilitates analytical modeling. An analytical framework is developed to predict actuator deformation as well as the corresponding elastic and output forces based on geometric parameters and pressure input, and is validated experimentally, showing good agreement across the displacement range. Furthermore, the effects of key design parameters on displacement and force output are investigated and characterized. The proposed Bi-OSPA combines structural predictive capability and bidirectional functionality, providing a foundation for the design and optimization of soft actuators. Its versatility is further demonstrated through applications in achieving pure twisting when integrated with a Kresling origami unit and as an actuation unit for a one-degree-of-freedom robotic finger enabling flexion and extension. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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20 pages, 13174 KB

Open AccessArticle

A Hybrid Gripper with Passive Jamming Fingers and Cable-Driven Joints for Enhanced Payload Capacity and Misalignment Tolerance

by Douglas See Zheng Yu, Wai Tuck Chow and Bin Zhu

Actuators 2026, 15(6), 318; https://doi.org/10.3390/act15060318 - 5 Jun 2026

Viewed by 1225

Abstract

Inspired by the human hand, this work presents a hybrid rigid–soft gripper that achieves passive adaptability through a self-resetting granular jamming pouch integrated onto a 3-DOF cable-driven rigid skeleton. Seven fingertip configurations (rigid tip, different jamming particles, and TPU-only) were evaluated across five [...] Read more.

Inspired by the human hand, this work presents a hybrid rigid–soft gripper that achieves passive adaptability through a self-resetting granular jamming pouch integrated onto a 3-DOF cable-driven rigid skeleton. Seven fingertip configurations (rigid tip, different jamming particles, and TPU-only) were evaluated across five object geometries. The jamming pouch configurations showed a clear advantage over rigid fingertips and a modest improvement over TPU-only fingertips when grasping flat or smoothly curved surfaces, while demonstrating substantially superior performance for objects with sharp protrusions, lips, undercuts, or deformable edges, where enhanced conformability and geometric interlocking markedly improved payload capacity and lateral offset tolerance. The passive self-reset mechanism remained reliable over 1000 cycles. These results demonstrate that the hybrid design effectively combines the advantages of rigid and soft grippers, achieving superior overall grasping performance while balancing adaptability and payload without pneumatic actuation, with strong potential for applications in logistics, food handling, and mobile robotics. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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12 pages, 2129 KB

Open AccessArticle

Biomechanical Evaluation of a Biomimetic Stand-Assist Toilet Seat for Older Adults: A Synchronized AI-Kinematic and Kinetic Analysis

by Shan-Ju Yeh, Shu-Yu Yang, Li-Chi Chao and Yu-Sheng Yang

Actuators 2026, 15(6), 316; https://doi.org/10.3390/act15060316 - 3 Jun 2026

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Abstract

Many older residential toilet designs may pose substantial biomechanical demands for older adults with reduced lower-extremity strength, as standard seat heights often require increased joint range of motion (ROM) and compensatory upper-limb support during sit-to-stand (STS) transfer. This exploratory, repeated-measures biomechanical study evaluated [...] Read more.

Many older residential toilet designs may pose substantial biomechanical demands for older adults with reduced lower-extremity strength, as standard seat heights often require increased joint range of motion (ROM) and compensatory upper-limb support during sit-to-stand (STS) transfer. This exploratory, repeated-measures biomechanical study evaluated the effects of a biomimetic Stand-assist Toilet Seat (BSTS) designed to facilitate STS movement through a forward-and-upward curvilinear lifting trajectory. Thirty community-dwelling older adults were stratified into high-, moderate-, and low-functioning groups according to normative 30 s Chair Stand Test performance. Participants completed repeated STS trials under conventional and BSTS-assisted seating conditions in randomized order. A synchronized multimodal assessment integrating MediaPipe Pose-based motion tracking for sagittal-plane kinematic analysis was used to quantify lower-limb kinematics and upper-limb kinetics. Mixed-design ANOVA revealed significant main effects of seating condition on hip and knee ROM (all p < 0.001, η²p > 0.70), indicating reduced lower-limb joint motion requirements under the BSTS condition. Significant reductions were also observed in peak arm-support force (F (1,27) = 14.57, p = 0.001, η²p = 0.35) and arm-support impulse (F (1,27) = 20.21, p < 0.001, η²p = 0.42), demonstrating decreased upper-limb loading during STS transfer. No significant interaction effects between seating condition and functional group were identified. These findings suggest that the BSTS modified STS movement patterns and reduced upper-limb loading demands in community-dwelling older adults. The combined kinematic and kinetic assessment approach may provide a practical method for biomechanical evaluation of assistive seating technologies in rehabilitation and aging-related applications. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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16 pages, 6859 KB

Open AccessArticle

Preload-Dependent Protective Reaction Latency in a Pneumatic Artificial Muscle-Actuated Humanoid Joint

by Dávid Kóczi and József Sárosi

Actuators 2026, 15(5), 277; https://doi.org/10.3390/act15050277 - 19 May 2026

Viewed by 465

Abstract

Humanoid robots operating near humans require short protective reaction times in physical human–robot interaction (pHRI). Safety standards distinguish between quasi-static and transient contact. This paper quantifies the reaction timing of a compliant pneumatic artificial muscle (PAM) mechanism under controlled preload conditions. Measurements were [...] Read more.

Humanoid robots operating near humans require short protective reaction times in physical human–robot interaction (pHRI). Safety standards distinguish between quasi-static and transient contact. This paper quantifies the reaction timing of a compliant pneumatic artificial muscle (PAM) mechanism under controlled preload conditions. Measurements were performed at 10 N, 50 N, and 100 N preload using synchronised load-cell force, PAM pressure, actuator position, and force-sensitive resistor (FSR) signals. Reaction timing was evaluated relative to the FSR-defined contact onset, at which the controller issued the pressure-release command. The force trace reached its first post-contact peak within 15–20 ms after onset, while the pressure peak occurred within 5–15 ms. A 90% recovery of the post-contact force excursion was achieved within 40–50 ms, whereas the corresponding pressure excursion required 155–180 ms. These timing results quantify reaction latency in PAM-actuated humanoid joints and support multi-modal sensing for robust onset localisation and mitigation monitoring in both ISO/TS 15066 contact types. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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15 pages, 3629 KB

Open AccessArticle

Dual-Layer Flexible Capacitance Sensor with Wide Range and High Sensitivity

by Benyuan Fu, Zipei Wang, Kun Chen, Zebing Mao, Hao Wang, Benxiang Ju and Yanhong Peng

Actuators 2025, 14(5), 251; https://doi.org/10.3390/act14050251 - 16 May 2025

Cited by 3 | Viewed by 2015

Abstract

Flexible pressure sensors have attracted great attention due to their extensive applications in human–computer interaction and health monitoring. So far, the development of flexible pressure sensors that balance high sensitivity and a wide measurement range remains a challenge. Herein, a double-layer dielectric structure [...] Read more.

Flexible pressure sensors have attracted great attention due to their extensive applications in human–computer interaction and health monitoring. So far, the development of flexible pressure sensors that balance high sensitivity and a wide measurement range remains a challenge. Herein, a double-layer dielectric structure with a surface convex structure is reported for the preparation of flexible capacitive pressure sensors. The double-layer dielectric structure, which is composed of a silicone rubber-based conductive elastomer with a surface micro-convex structure and a PVA-H-based conductive elastomer, balances the advantages and disadvantages of the two conductive elastomer dielectrics. It can form a complete micro-capacitive network under relatively large pressures, enabling the sensor to have high sensitivity at different stages (1.7 kPa⁻¹, 0–104 kPa; 19.14 kPa⁻¹, 104–140 kPa), thus achieving a dual enhancement of sensitivity and sensing range. Additionally, the sensor has been successfully applied to scenarios such as monitoring of human breathing, speaking, and movement, as well as mouse clicks, demonstrating its great potential in the fields of health monitoring and human–computer interaction applications. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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Other

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40 pages, 2184 KB

Open AccessSystematic Review

Fault Detection, Sensing, and Intelligent Control in Soft Wearable Actuators for Rehabilitation and Motor Assistance: A Systematic Review

by Cristina Floriana Pana, Daniela Maria Pătrașcu-Pană, Camelia Adela Maican and Virginia Maria Rădulescu

Actuators 2026, 15(8), 431; https://doi.org/10.3390/act15080431 - 7 Aug 2026

Viewed by 555

Abstract

Soft wearable actuators offer compliant, lightweight assistance for rehabilitation and motor support, but their translation beyond controlled laboratories depends on reliable sensing, fault management, and adaptive control. This systematic review maps the evidence across three linked domains: fault detection and diagnosis (FDD), sensing, [...] Read more.

Soft wearable actuators offer compliant, lightweight assistance for rehabilitation and motor support, but their translation beyond controlled laboratories depends on reliable sensing, fault management, and adaptive control. This systematic review maps the evidence across three linked domains: fault detection and diagnosis (FDD), sensing, and intelligent control. Owing to marked heterogeneity in actuator types, validation settings, and reported outcomes, the evidence was synthesised narratively and described using publication counts and proportions rather than pooled performance estimates. The study-level supplementary appraisal covers all 106 publications included in the review. Four normative standards were retained within this total as normative context and were marked as not applicable for empirical methodological appraisal; they were not subtracted from the corpus count. Across the 106 included records, 40 were classified as direct, 57 as adjacent, five as indirect, and four as normative context. The FDD subset was especially limited: nine records provided adjacent evidence and five were indirect under the strict soft-wearable rehabilitation criterion. The review therefore identifies soft-actuator-specific FDD benchmarks, multimodal health-state estimation, and fault-aware control as actionable priorities, while distinguishing these structural gaps from constraints expected in a technologically young field. The completed review was retrospectively registered in the OSF Registries on 21 July 2026 using the Open-Ended Registration template. Full article

(This article belongs to the Special Issue Bioinspired Intelligence for Soft Actuators: Learning, Control, and Embodied Design)

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