cs.ROOct 8, 2026

A Reconfigurable Fabric Based Pneumatic Actuator with Button Fastened Constraint Modules for Multi Mode Actuation

Authors: Kentaro Kimura, Hiroki Ishizuka, Yusuke Sakaue, Sei Ikeda, Osamu Oshiro

Organizations: Graduate School of Engineering Science, Osaka University, Osaka 560-0043, Japan

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Abstract

Soft pneumatic actuators are widely used in soft robotics. However, their actuation modes are typically fixed by internal chamber designs or reinforcements, making post fabrication reconfiguration difficult. This paper presents a reconfigurable fabric-based pneumatic actuator that enables rapid, tool free, and reusable switching among multiple actuation modes by attaching constraint fabric modules to a buttoned textile sleeve. By rearranging low-stretch constraint parts on a single actuator body, the proposed system realizes four actuation modes isotropic expansion, contraction, bending, and twisting without redesigning or disassembling the actuator.We further introduce an attachable capacitive fabric-based tactile sensor module that can be mounted at arbitrary locations on the actuator surface for task dependent contact sensing. Experiments demonstrated an elongation ratio of 1.2, a maximum bending angle of approximately 60 degrees, and a twisting angle of approximately 90 degrees at 24 kPa, while achieving blocking forces exceeding 10 N across all modes. The tactile sensor exhibited a monotonic, force-dependent increase in capacitance with low hysteresis (approximately 12%) and stable cyclic responses under preload. Finally, we constructed soft robotic arms composed of multiple actuators and demonstrated in situ motion reconfiguration for grasping by changing the attached constraint patterns. These results indicate that the proposed modular constraint and sensing framework improves the functional adaptability of fabric-based soft robots while preserving a simple, robust actuator structure.

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Fig. 1: Deformation of a fabric-based pneumatic actuator can be designed by taking into consideration stretchability. (a) A fabric-based pneumatic actuator expands nearly uniformly when not constrained. (b) A fabric-based pneumatic actuator contracts when all its sides are constrained. (c) A fabric-based pneumatic actuator bends when one of its sides is constrained. (d) A fabric-based actuator twists when spiral constraints are applied.
Fig. 2: Fabrication process of the fabric-based pneumatic actuator. The internal silicone rubber body for the pneumatic actuator was formed using resin molds (Upper). The external fabric skin was a fabricated stretchable textile (Bottom). Finally, the silicone rubber body was covered with the fabric skin (Right).
Fig. 3: Photographs of fabric-based pneumatic actuator and its components. (a) A silicone rubber bladder is used inside the actuator. (b) A non-elastic deformation constraint part. (c) An actuator made of highly elastic fabric and a button for attaching a constraint part. (d) (e) (f) Constraint patterns for each actuator.
Fig. 4: Fabric-based tactile sensor and its principle. (a) Sensor structure and principle. (b) Overall view of the tactile sensor. (c) Silicone rubber was used as a dielectric layer.
Fig. 5: Experimental setup to evaluate a fabric-based pneumatic actuator. The fabric-based pneumatic actuator was actuated by pneumatic pressure, and its motion was recorded with a video camera. The actuation was analyzed using image processing.
Fig. 6: Experimental setup to evaluate the blocking force of a soft pneumatic actuator. A test stand was used to fix the actuator, and the blocking force was measured using a force gauge.
Fig. 7: Experimental setup to evaluate a capacitive fabric-based tactile sensor. A three-axis table robot was used to apply force to the fabric-based tactile sensor, and the sensor output was measured using an LCR meter.
Fig. 8: Fabric-based pneumatic actuators under constraints actuated as designed. (a) Without constraints, the fabric-based pneumatic actuators expanded in all directions. Approximate increase in elongation ratio in the longitudinal direction was 20%. (b)The fabric-based pneumatic actuators contracted to approximately 96% of the initial length. (c) The fabric-based pneumatic actuators performed bending actuation, approximately 60 degrees. (d) Under helical constraints, the fabric-based pneumatic actuators achieved a twist angle of 90 degrees. (e),(f) Experimental photographs: The left and right images show the initial state and the state when maximum pressure was applied, respectively.
Fig. 9: Blocking force for each constraint pattern increased with the applied pneumatic pressure. At low pressures, the blocking force remained small, likely because most of the pneumatic energy was consumed in expanding the actuator rather than being converted into external force. (a) No constraint. (b) Contraction. (c) Bending. (d) Twisting.
Fig. 10: The soft force sensor’s output increased with increasing force, as designed. (a), (b), and (c) show the results for the tactile sensor we fabricated. High linearity and reproducibility were confirmed.
Fig. 11: As an application, we constructed two soft robotic arms and conducted object-grasping experiments. (a) Each soft robotic arm consisted of two soft pneumatic actuators. By altering the constraint pattern on the actuator surface, the motion of the soft robotic arms could be reconfigured. (b) We confirmed that reconfiguring the motion enabled adjustment of the grasping position.
Fig. 12: By altering the constraint patterns of the soft robotic arms as designed, we were able to alter the grasping position. (a)–(c) The upper actuators were configured for contraction, while the lower actuators were configured for bending, enabling the soft robotic arms to grasp an object located directly beneath them. (d)–(f) By configuring all actuators for bending, the soft robotic arms were able to grasp an object located in front of the arm. These results demonstrate that the arm motion can be reconfigured solely by changing the surface constraint patterns, without disassembling the soft robotic arms.
Fig. 13: Sensor outputs during object grasping with the soft robotic arms. (a) Sensor output when grasping an object located directly beneath the soft robotic arms. (b) Sensor output when grasping an object located in front of the soft robotic arms.
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