In this paper, we propose an axially reinforced toroidal mechanism capable of transferring delicate cell sheets. Several soft grippers based on inflatable membranes have been proposed using elastic rubber materials. However, due to their high compliance, force transmission is insufficient, making it difficult to achieve stable tip eversion for peeling and releasing cell sheets. To address this issue, we develop a toroidal balloon mechanism reinforced in the axial direction using inextensible fibers. The fabrication method is presented, and the stress–strain characteristics of the reinforced membrane are experimentally evaluated. Furthermore, a basic grasping experiment is conducted to demonstrate the effectiveness of the proposed mechanism.

In this article, we propose a novel, fixture-free, three-dimensional (3-D) sewing system. In 3-D sewing, the fabric parts are sewn together along seams that are defined separately for the upper and lower fabrics. To sew the fabrics along their respective seams, the upper and lower fabrics must be manipulated independently. Our proposed mechanism uses a conical roller with “conchospiral” ridges to manipulate each fabric around the sewing needle, generating biaxial anisotropic friction between the roller and the fabric. First, we discuss the design of the conical roller with the conchospiral ridges. Then, we evaluate the biaxial anisotropic friction characteristics of the proposed rollers with different design parameters. The experimental results demonstrate how the traction of the roller with different fabrics is affected by the offset angle of the roller. Finally, we conduct sewing experiments using an automated 3-D sewing system with the proposed mechanism. These experiments demonstrate the effectiveness of using the conical roller with conchospiral ridges for 3-D sewing, achieving a level of sewing accuracy that is sufficiently high compared to that observed in real car seats.

Multi-degree of freedom (DOF) robotic systems, particularly those with seven or more DOFs similar to the human arm, have the potential to significantly expand the functional range and versatility of robotic manipulators. The spherical gear mechanism, known as Active Ball Engagement Mechanics (ABENICS), serves as a novel joint element that enables the integration of multiple rotational axes at a single point, resulting in a more compact structure with increased degrees of freedom. This study focuses on the design and validation of a miniaturized spherical gear mechanism, featuring a spherical gear with a module of 1.5 mm and an outer diameter of 51 mm. The study discusses its mechanical design, operational performance, and manipulability-based motion control strategy for effective singularity avoidance. Furthermore, a driving gear-based angular feedback system utilizing hall-effect sensors is introduced for homing, demonstrating improved performance and reliability compared to the previously implemented IMU-based homing approach. Experiments were conducted to assess the mechanism’s motion range, positional error, singularity avoidance, and homing performance, all of which were successfully validated. The results confirm the potential of this miniaturized mechanism to enable more compact, efficient, and functional robotic systems. Finally, the study demonstrates the application of the developed mechanism as a wrist joint attached to a robotic arm, capable of carrying a 250 g payload during a pick-and-place task.

Magnetic bacteria utilize environmental forces to control their posture. Focusing on this property, we devised an "underwater-driven torus-type buoyancy control mechanism" that minimizes self-energy consumption. By employing a torus-shaped actuator, we expect that the cross-sectional area will not change during actuation, thereby preventing an increase in fluid resistance. Furthermore, its ability to extend and retract from the torus tip suggests potential applications for sample collection beneath sea ice. This paper describes ensuring airtightness for the torus's underwater operation and verifying this airtightness via the liquid immersion method. We also confirmed the buoyancy generated by this mechanism through physical experiments. The measured buoyancy indicates that desired buoyancy adjustment may be achievable by varying the membrane diameter and axial extension amount in the design.

Drone docking stations promote efficient operations of drones, but they usually support only one vehicle, and are accessible primarily through vertical landing. These limitations hinder multi-drone operations and result in challenges for fast, precise docking, particularly under severe wind conditions. This study assesses the EAGLES port, which uses a horizontal landing approach to address these challenges, and makes a performance comparison between horizontal and vertical landing through analysis of wind tunnel data. Results show that horizontal landing decreases the average landing duration by 35.58%, and can achieve 59.67% faster docking compared to vertical landing in optimal conditions. The system also provides near-zero position error at docking, and supports multiple drones. These advantages stem from improved flight stability, quicker alignment with landing targets, and a 2.8 times higher average velocity compared to vertical landing. These results indicate that vertical landing is better suited for missions with wider landing zones and where delays in landing have mild consequences, whereas horizontal landing excels in scenarios where rapid accurate landings are critical.

This paper proposes an axially extension-constrained micro tube mechanism that integrates force transmission and fluid supply to achieve minimal actuation system design. By embedding fibers within a coated wire, the proposed structure simultaneously functions as a transmission element and a pneumatic supply channel, addressing interference issues in conventional dual-system configurations. Prototypes were developed and evaluated through actuation, fluid supply, and durability experiments. The results demonstrate effective force transmission and tunable fluid delivery characteristics. Furthermore, the proposed concept enables compact multi-axis actuation systems and suggests potential applications in soft robotic mechanisms and wire-driven manipulators.

Slender robots are essential for search-and-rescue operations in disaster sites. While actively articulated slender robots can achieve follow-the-leader motions suitable for confined spaces, they are difficult to miniaturize and lighten. Conversely, soft robots with passive joints offer simpler structure but often suffer from low durability and poor self-weight compensation. This study proposes a novel design approach for slender robots utilizing passive joints with preload torque. By designing a monotonic torque distribution, stable push-driven insertion is achieved through environmental contact. This mechanism enables sequential unilateral bending, where bending propagates from the tip to the base without buckling, facilitating wall-following propulsion without the need for active control. A static model was formulated to derive the necessary conditions for this motion, demonstrating that preload torque must increase monotonically from the tip to the base. Power-law and exponential distributions were found to satisfy these requirements within specific parameter ranges. Quasi-static simulations in both single- and multiple-contact environments validated these theoretical predictions. Furthermore, prototype experiments demonstrated contact-based propulsion, confirming that a power-law torque distribution capable of compensating for self-weight ensures stable performance. The proposed method reduces actuator requirements while maintaining high operational stability, offering a promising approach for exploring confined spaces.

Visual markers are widely used for pose estimation and information retrieval. However, commonly used monochrome markers, such as ArUco markers and QR codes, are typically designed to support either pose estimation or information storage, but not both simultaneously. A previously proposed method, HueCode, addressed this gap by constructing a composite marker that combined multiple individually functional markers within a single marker region using color. However, it relied on specialized detection algorithms and pre-trained systems, which limited its applicability in general use cases. To address these limitations, this study introduces Universal HueCode, a framework that embeds additional markers within a conventional monochrome marker. The proposed framework combines an optimized color scheme, designed to preserve primary monochrome marker readability with standard readers, with a training-free recognition pipeline that reconstructs the embedded marker through color clustering within the detected marker region. Experiments conducted under varying light output and correlated color temperature demonstrated that Universal HueCode achieved the highest decoding success for both the primary and embedded markers among the compared composite-marker baselines, while preserving primary-marker readability close to that of standalone monochrome markers and enabling real-time operation under our settings.

This paper proposes a deployable mechanism that can be stored compactly and extended using torsional deformation while maintaining high structural stiffness when deployed to its extended position. The core concept is to make a structure that has low stiffness only in torsion, while exhibiting high stiffness in compression, bending, and shear. This anisotropic stiffness allows the structure to be compressed to a stowed configuration by twisting and to maintain stiffness when under deployed configuration. Based on this principle, a deployable mechanism named "D-spine" was designed and prototyped. In this paper, the proposed structure is developed, keeping the total length to 1 meter. To evaluate for the desired characteristics, various experiments were performed, and the behavior of the structure was observed to evaluate the stiffness of the structure under shear, bending, compression, and torsional loads. The experimental results indicate that the structure exhibits relatively high stiffness under both bending and shear loads, demonstrating strong resistance to lateral deformation. However, compression testing revealed the need for a critical load threshold to prevent structural instability and collapse. In contrast, torsional experiments confirmed that the structure can be effectively extended and collapsed when subjected to sufficient torque. Overall, the results validate the anisotropic stiffness characteristics of the proposed mechanism and demonstrate the feasibility of achieving both a high extension ratio and structural rigidity using a simple torsion-based actuation approach.

Omnidirectional drive mechanisms enable mobile robots to move in any direction without changing their orientation, allowing holonomic motion and smooth directional transitions. Among these mechanisms, spherical drives provide continuous ground contact and rapid directional response, making them attractive for mobile robotic platforms. However, many existing spherical friction-driven mechanisms typically apply non-uniform and unregulated contact forces to the spherical wheel, resulting in uneven torque transmission, increased slippage, and accelerated mechanical wear. In addition, some designs suffer from kinematic limitations that restrict stable and continuous motion control. To address these issues, this paper proposes a friction-driven spherical omnidirectional mechanism based on a multi-disk configuration. The system employs sliding screws attached to the disks to regulate the normal force applied by each disk to the spherical wheel, enabling controllable friction-based torque transmission. A prototype is developed and experimentally evaluated using a force measurement setup. The results demonstrate that the transmitted torque can be effectively controlled by adjusting the disk–sphere contact conditions, and an optimal contact position for maximum torque transmission is identified. Furthermore, directional motion can be achieved by coordinating the force distribution among multiple disks, leading to reduced slippage and improved overall system efficiency.

In recent years, variable-stiffness mechanisms that combine flexible structures for deformation with rigid structures for resisting external loads have attracted increasing attention in the field of soft robotics. Conventional friction-based serial variable-stiffness mechanisms using spherical joints generally rely on frictional locking, which limits their load-bearing capacity under external loads. To overcome this limitation, this study proposes a novel variable-stiffness linear mechanism with inclined rotational joints, which achieves high holding force by constraining the degrees of freedom of the modules. The proposed mechanism is a hybrid locking mechanism that combines frictional locking with geometric support. The tension of an internal steel wire passing through serially connected modules generates inter-module friction, while inclined surface structures between adjacent modules provide additional geometric support against external loads. This dual-support principle is expected to improve the resistance of the mechanism to external loads and enhance posture-holding stability. To validate the proposed joint structure, a preliminary experiment was conducted using a pair of inclined-joint modules. The maximum holding force of the module pair was measured under external loading from different directions in the locked state. The experimental results show that the proposed inclined-joint structure can sustain external loads in multiple loading directions by combining frictional locking with geometric support. These results demonstrate the basic feasibility of the proposed joint structure as a fundamental unit for variable-stiffness linear mechanisms.

This paper proposes a novel helical propulsion mechanism using an open-ended hyperboloidal helix with an inclined rotation axis for interaction with net-like structures. When a conventional cylindrical helix is inclined, the intersection points between the helix and the net surface become distorted, producing unwanted lateral interactions and increased resistance. To address this problem, this study introduces a helix defined on a hyperboloid of one sheet, which enables the penetration points between the helix and the net to remain aligned along straight lines even under a specified inclination angle. First, the geometric modeling is formulated, and the parametric representation of the hyperboloidal helix is derived. Next, a power transmission mechanism based on a pair of meshing hyperboloidal gears is proposed to drive the open-ended hyperboloidal helix. A prototype propulsion system consisting of the hyperboloidal helix, transmission mechanism, and actuator is constructed. Finally, a proof-of-concept demonstration shows continuous and smooth linear propulsion. These results indicate that the proposed structure provides a promising foundation for mobile robots and material handling applications involving reticular environments.

In large-scale shipbuilding, welding tasks represent a significant portion of all tasks, requiring automated robot operation. However, current welding robots are not automated for high and narrow spaces because they cannot pull heavy welding cables, causing deviations from the intended path and reducing the welding accuracy. This paper proposes a cable-towing stabilization method considering factors such as the self-weight of multiple vehicles, magnetic adhesion force, and force necessary to hold the cables. The proposed approach integrates welding robots, which perform welding tasks, with towing robots, which alleviate the load imposed by welding cables and wire feeders. Cable-towing on walls requires reducing excessive distances between vehicles, as well as their excessive acceleration, in addition to maintaining the mechanical stability of each vehicle. Therefore, the optimal positions and postures of the towing vehicles are sequentially calculated using an optimization problem. The proposed method was evaluated through simulations and real-world experiments, confirming stable cable-towing on a wall surface of approximately 3x1.5 m. The findings of this research enhance the safety and efficiency of managing deformable linear objects with robots, focusing on mechanical safety while expanding the operational range from single-vehicle wall-mounted operations to cooperative multi-vehicle wall-mounted tasks, thereby increasing applicability to various wall-towing scenarios.

In this paper, we further develop the concept of a tolerable-based actuation robot mechanism that we have been investigating. Specifically, we propose and physically realize a novel omnidirectional edge-bending mechanism. Through experiments conducted using the fabricated prototype, we evaluate the fundamental effectiveness of the proposed principle and identify remaining challenges.

Jamming grippers and actuators are gaining popularity in soft robotics application. The ideal material for such applications should include properties like wide range of stiffness variation, high degree of self-restoration, good deformation and extensibility, and ability of shape adoption. Current working materials like fluids, elastomers, granular materials have a part of this set of properties. However, these materials have their own shortcomings. Here, we propose a new material which incorporates all the aforesaid properties but excludes any other undesirable characteristics, which pose as hindrances. By combining the concept of space-filling curves with granular materials, the desired properties have been produced. In this paper, we have studied the fluid characteristics of this material to confirm the existence of deformability, extensibility, and shape adaptability properties of the prototype.

This paper proposes a circular cross-section crawler mechanism with a high coverage ratio for omnidirectional mobility in uneven environments. Conventional crawlers provide a large ground contact area and good terrain adaptability; however, they rely on skid steering, which causes wear on both the tracks and the ground surface and makes precise positioning in narrow spaces difficult. To address these limitations, we propose a crawler configuration that increases the coverage ratio while enabling omnidirectional motion. To prevent interference between neighboring and internal tracks, two types of crawler units with different tread patterns are alternately arranged. In addition, a differential mechanism is introduced to distribute power to multiple tracks and realize continuous omnidirectional motion using two input shafts. A prototype robot was developed, achieving a coverage ratio of approximately 78%. Experimental results demonstrate that the proposed mechanism enables track driving, unit rotation, and continuous omnidirectional locomotion.

Load-adaptive gravity balancing mechanisms (LA-GBMs) have attracted considerable attention in practical applications involving the handling of variable payloads under gravity. Among them, the development of fully passive load-adaptive gravity balancing mechanisms (FLA-GBMs), which achieve the entire load-adaptation process without any external intervention such as manual adjustment, is an important research challenge with the potential to significantly expand the applicability of LA-GBMs. Despite their potential benefits, no practical realization of an FLA-GBM has yet been reported, and even the feasibility of such mechanisms remains unclear. In this study, the behavior of LA-GBMs is formulated as an affine function of the payload. Based on this formulation, it is theoretically proved that FLA-GBMs cannot exist under quasi-static processes. The affine formulation is derived from the conservation law of mechanical energy and reveals further fundamental limitations of LA-GBMs. In particular, it suggests that admissible-motion constraints are essential for the implementation of LA-GBMs, and that FLA-GBMs remain difficult to realize even when dynamic state transitions are exploited. These findings clarify fundamental properties underlying the design of LA-GBMs and provide useful guidelines for their future development.

This paper proposes a complementary tensioner mechanism that enables belt-driven motion along curved paths. In belt drive systems, when the driving edge moves along a curved trajectory, the belt path length varies, causing fluctuations in belt tension and drive stiffness. The proposed mechanism compensates for this variation by moving a tensioner unit along a complementary curve designed with respect to the driving curve, thereby maintaining a constant belt circumference. A design theory and a numerical algorithm for generating complementary curves are developed. In addition, a floating unit composed of a timing pulley and a spur gear is introduced to reduce the spatial size of the complementary curve using a reduction ratio. Torque measurement experiments with a prototype mechanism demonstrate that torque fluctuations are significantly suppressed compared with a conventional spring-based tensioner, indicating that the belt tension remains nearly constant during curvilinear motion.

This study proposes a flame-resistant soft actuator designed for use in robotic systems operating in fire-disaster environments. Two types of actuators were developed: a pouch-type actuator constructed from flame-retardant sheet materials, and a spiral-type extendable actuator for thermal shielding. Prototypes were fabricated and experimentally validated under direct flame exposure, demonstrating structural integrity and repeatable actuation. Mechanical performance was further evaluated using tensile tests. These results confirm the feasibility of lightweight, fire-resistant actuation mechanisms for search and rescue robots. Future work includes system integration for mobile robots and exploration of flame-resistant sensors and power sources.