In recent years, cord-shaped soft mechanisms have been studied for medical and pipe-inspection applications due to their features such as safety and shape applicability. Some of these mechanisms use actuators based on McKibben-type artificial muscles [1][2]. The artificial muscle consists of a rubber tube and fibers forming a sleeve; half of the fibers are arranged spirally in a clockwise direction, and the other half in a counterclockwise direction. When air pressure is applied, the actuator expands and contracts in the axial direction. Additionally, by arranging a restraining material axially, a curved actuator is created, and by removing the fibers in either the clockwise or counterclockwise direction, a torsional actuator is fabricated. By combining these actuators with different motions in series, soft mechanisms with multiple degrees of freedom (DOF) can be realized. However, the manufacturing process is complex because each actuator is generally manufactured individually and then combined manually.

In this study, we propose a simple fabrication method of soft mechanisms that uses a braider machine. The braider machine has multiple bobbins with fibers set in them. Half of the bobbins rotate clockwise, and the other half rotate counterclockwise, crossing each other. In the center of the machine, the fibers are braided into a helical shape. Therefore, a McKibben-type artificial muscle is realized by setting a rubber tube in the center and driving the machine. The braider machine can also composite fibers in the axial direction, making it possible to realize a curved-type artificial muscle.

In this report, we fabricated a 2-DOF soft mechanism with combined twisting and curving motions. For realizing it, half of the fibers on bobbins are water-soluble fibers, and the other half of fibers are non-soluble fibers, and one plastic fiber is set for restricting material axially. By driving the braider, the rubber tube is covered with them. Twisting part can be realized by solving the water-soluble fibers by soaking them in water and removing the plastic fiber. On the other hand, for the curving part, no procedure needs.

The fabricated soft mechanism has a diameter of 5 mm and a total length of 105 mm, with 33.7 mm dedicated to a twisting part and 71.3 mm to a curving part. Basic experiments have shown that the developed soft mechanism enables independent movement of each part. The maximum twisting and curving angles are 350°and 100°at 300kPa of pneumatic pressure.

We realized the simple fabrication process of cord-shaped soft mechanisms by using the braider, and 2 DOF soft mechanism with twisting motion and curving motion was fabricated. We have plan to apply the mechanism to the medical endoscope in the future.

[1] Guan, Q.; Sun, J.; Liu, Y.; Wereley, N.M.; Leng, J. Novel Bending and Helical Extensile/Contractile Pneumatic Artificial Muscles Inspired by Elephant Trunk. Soft Robot. 2020, 7, 597–614.

[2] Polygerinos, P.; Wang, Z.; Galloway, K. C.; Wood, R. J.; Walsh, C. J. Soft Robotic Glove for Combined Assistance and At-Home Rehabilitation. Robot. Auton. Syst. 2015, 73, 135–143.

Acknowledgments

This study was partly supported by JKA through its promotion funds from KEIRIN RACE.

A lysimeter-soil retriever (LSR) is a device that facilitates the efficient and non-disruptive retrieval of soil from lysimeters, streamlining the sampling of intact soil layers. This tool proves particularly advantageous when sampling a substantial quantity of lysimeters, as it simplifies and accelerates the process. Existing LSR designs are complex and better suited for large monolithic field lysimeters. However, these designs are unnecessary for retrieving soil from mini or small lysimeters. Therefore, a simple LSR was fabricated using a linear actuator to retrieve soil from mini or small lysimeters. This paper focuses on the optimization of voltage applied to a linear actuator to control the incremental stopping of soil blocks at heights of 5 and 10 cm. Additionally, performance loss measurements were conducted after soil retrieval from 80 lysimeters. To optimize speed, voltages ranging from 24 to 19 V were applied, and the linear actuator speed and soil block heights were measured. The maximum force and time required to complete a full stroke were also measured before and after the retrieval of 80 lysimeters to assess performance loss. The results showed a linear decrease in linear actuator speed with increasing voltage. Additionally, there was a significant (P<0.05) increase in soil block heights as the voltage increased. The desired soil block heights were achieved at 19 V, corresponding to an actuator speed of 11.6 mm/s. Therefore, 19 V was determined to be the optimum voltage for this study. Furthermore, after the retrieval of 80 lysimeters, there were no significant changes in the maximum force and time required for a full stroke, which were recorded as 43 s and 530 N, respectively. These findings demonstrate that the linear actuator is a suitable alternative to a hydraulic piston as a force applicator in the LSR design.

This paper explores the design, development and testing of a tailless, two-winged robotic hummingbird, named COLIBRI. The current version of our robot has a total mass of around 22 gr, a wingspan of 21cm and a flapping frequency of around 20Hz. The primary objective is to enhance its flight autonomy and stability. The control system incorporates two attitude reconstruction algorithms: a Complementary filter and a full state dynamic observer implemented as a Kalman filter. Both of them were designed to filter out the noise caused by the rapid flapping of the wings, ensuring accurate and reliable attitude estimation. They are implemented on a newly developed control board with enhanced performance and reduced weight. Experimental results demonstrate successful attitude stabilization and improve station keeping, despite significant flapping noise. Notably, the gear-based prototype achieved a maximum flight time of 4 minutes and 45 seconds, highlighting the effectiveness of the design improvements in extending flight duration.

Additive manufacturing has garnered significant attention due to its ability to replace conventional casting methods, resulting in cost reduction while meeting the increased demands for performance and cost-effectiveness in hydraulic valve bodies within the industry. Binder jet print (BJP), an additive manufacturing technique applicable to metal materials, presents new opportunities for innovating valve system production methods. This approach also allows for the redesign of electro-hydraulic systems traditionally limited by casting processes. Conventional methods often struggle to fabricate multifunctional parts without compromising functional performance or requiring additional supporting structures for manufacturability. However, the advancement of additive manufacturing technologies enables integrated actuator design and manufacturing, liberating them from these conventional constraints. These technologies facilitate the achievement of enhanced performance and multifunctional requirements for actuators, merging design and manufacturing into a cohesive domain where material and structure considerations are integrated.

In this research, we propose a compact valve system supporting body structure, considering material properties, functionality, limitations of binder jet print, dimensions, and manufacturing shrinkage. Binder jet print offers the possibility of replacing two die-casting parts with a single additive manufacturing part, necessitating the rearrangement of the possible spacer plate. Additionally, spool valves and pilot solenoids are redesigned to fit the new valve body housing. To streamline the assembly process and mitigate the drawbacks of BJP technology, spool valve sleeves are innovatively introduced into the transmission valve body design. The newly designed spool valves, assembled in the BJP valve body, aim to deliver equal or superior static response performance. This research also discusses special designs for additional components such as pressurized vents, check ball valves, and mounting parts.

This study represents a pioneering attempt to apply binder jet print to the complex industrial valve body system, with the goal of redesigning a lighter, smaller, and more cost-effective valve body. The valve actuator supporting shell is redesigned for one-step molding, and the hydraulic path is reconfigured while preserving functionality. Material considerations for the valve actuator supporting shell are addressed to mitigate deformation caused by post-processing, which may lead to the leakage issues arising from the porosity of the valve body shell. By integrating all orifices into spool valve sleeves, we achieve the same or improved pressure drop control.

Moreover, the application of binder jet print in valve body manufacturing provides an opportunity to explore new material compositions and structural designs that were previously infeasible with traditional casting methods. This flexibility allows for the incorporation of advanced features such as optimized fluid flow channels, enhanced thermal management, and reduced weight, all of which contribute to the overall efficiency and performance of the hydraulic system. The integration of these features is critical for meeting the demanding operational requirements of modern industrial applications, where reliability and precision are paramount.

To validate the feasibility and advantages of the binder jet print valve body, this research includes a comprehensive comparative analysis of the static response performance. Additionally, we explore the potential for further enhancements in valve body design through iterative testing and optimization, paving the way for future advancements in the field of hydraulic valve systems.

In conclusion, this research demonstrates the significant potential of binder jet print as an innovative manufacturing method for hydraulic valve bodies. By addressing the limitations of conventional casting and offering new design possibilities, binder jet print stands to revolutionize the production of hydraulic components, leading to more efficient, cost-effective, and high-performance systems. This work lays the foundation for future studies and applications of additive manufacturing in the industrial sector, highlighting the transformative impact of this technology on traditional manufacturing processes.

Vector hydrophones play an important role in underwater acoustic detection systems. In response to the low bandwidth problem of traditional piezoelectric ceramic based single-sided fixed cantilever beam structure hydrophones and the difficulty in miniaturization of compression type hydrophones, this paper proposes a double-sided fixed common mass block vector hydrophone based on the relaxation ferroelectric single crystal shear vibration mode. The vector hydrophone proposed in this article achieves higher receiving sensitivity due to the use of high-performance relaxor ferroelectric single crystals. The design structure using shear vibration mode is more conducive to miniaturization, and the double-sided fixed common mass block design is used to obtain higher working receiving frequency bandwidth. Simulation results show that the first-order resonant frequency of the double-sided fixed common mass block type vector hydrophone proposed in this article is 47 kHz, which is more than twice the first-order resonant frequency of the single-sided fixed vector hydrophone. The vector hydrophone proposed in this article is beneficial for the integration of underwater acoustic detection systems and the broadening of information sources.