Disaster response, especially fire-fighting and rescue, is highly risky for firefighters engaged in action. As a result, many robots intended for fire-fighting have been proposed. However, it is difficult for them to directly access fire sources because their mobility is limited. Specifically, existing robots are large and heavy. Therefore, we propose a novel hose-type robot, which can fly directly into the fire source via a water jet. First, to control the reaction force for stable flying, we developed a nozzle module. By combining two nozzles whose outlet direction can be controlled, the resultant reaction force can be controlled. Finally, we developed a robot with a nozzle module and conducted an experiment. The experiment demonstrates that a robot with a length of approximately 2 m can fly stably in the air by leveraging the water jet. In addition, the head direction can also be controlled.

This article presents an active ball joint mechanism (ABENICS) enhanced by interactions of spherical gears. The gear-based joint drives three rotational degrees of freedom (RDoF) without slippage. The capabilities were inspired by the unique interactions between two different innovative gears [the cross spherical gear (CS-gear) and monopole gear (MP-gear)] and the superimposition of those interactions by the CS-gear's quadrature spherical tooth structure. One MP-gear constrains two of the three RDoF of the CS-gear. The driving module which drives the MP-gear converts this “constraint” into a “drive” and drives the CS-gear with two RDoF. The CS-gear orthogonally superimposes the interactions caused by two MP-gears to achieve three RDoF driving forces. The principle was revealed by analyzing an equivalent linkage modeled on the mechanism of ABENICS. The linkage also led to the kinematics and torque equations. The theory and physical characteristics of ABENICS were verified in comprehensive and continuous positioning experiments on manufactured prototypes. The flexibility of the actuator placement was also verified in different configurations of the driving modules. The active ball joint, ABENICS can transmit high torque and reliable positioning in three RDoF without an orientation sensor, which applies to robot joints and orientation control mechanisms.

Aerial robotics is a fast-growing field of robotics and has been successfully used in various applications. Still, it faces many challenges such as dealing with unavoidable obstacles in a cluttered environment. Recently, a flying robot with a protective shell that can rotate passively was introduced. The passive rotating mechanism is intended to reduce the impact force on the attitude of the UAV. However, such a system also has some limitations. Because the shell rotates passively, the ability to physically interact outside the shell is limited, and the onboard camera and other remote sensors are constantly obstructed. In this study, a new idea is introduced in response to the limitations of the previous system, while retaining the protective shell and maintaining some degrees of passive rotation of the shell. It is proposed to position two passive rotating hemispherical shells in each rotor to directly protect the propeller. This paper presents the concept, discusses the design and proof of concept, and validates the concept through experiments. Various experiments are conducted to demonstrate the capabilities of the proposed flying robot, resolve the problem of physical interaction and camera obstruction, and introduce new advantages.

A gripper comprising a jamming membrane was developed with the capability of grasping collapsible, soft, and fragile objects without applying heavy pressure. In disaster sites, it is necessary for robots to grab various types of objects, such as fragile objects. Deformable grippers that contain bags filled with powder cannot handle collapsible or soft objects without excessive pressure. Changing powder density relatively by changing inner volume is one approach to overcome this problem. By expanding the concept and simplifying the variable inner volume of the gripping mechanism, we developed a jamming membrane comprising the following three layers: outer layer and inner layer made of rubber and a powder layer in between the outer and inner rubber layer. This jamming membrane allows collapsible, soft, or fragile objects to be held securely without applying too much pressure. We designed and developed a prototype of the jamming membrane gripper. Our experiments confirmed the validity of the proposed jamming membrane mechanism.

Flexible continuum robots exhibit a strong potential for approaching narrow and intricate spaces. However, such long flexible bodies often experience oscillations, making them unstable. To enhance their performance in order to realize rapid and precise movements, unnecessary vibrations should be suppressed. The authors have proposed a new type of continuum robot, aimed for firefighting; this robot, Dragon Firefighter (DFF), can fly using water jets. The DFF suffers from the same problem of body oscillation. In particular, a more challenging issue for the DFF is the use of limited number of actuators owing to the constraints of weight and water flow. Discrete locations of the actuators on the long body of a robot can generate uncontrollable resonant modes. This letter proposes a mechanical approach to suppress the oscillation passively without actuation control. The proposed mechanism is composed of wires threaded along the body and connected to rotary dampers to restrict the deformation of the body. First, a numerical model to simulate the oscillation and damping behavior was reported. A basic experiment with a 1-m-long flexible tube shows that the damping mechanism suppresses the vibration appropriately, which also corresponds well with the simulation. Second, a stability analysis of the simulation of the flying motion shows that the passive damping mechanism can improve the stability, with the convergence time becoming approximately 2.4 times shorter than that in the case without the mechanism. Finally, we apply the damping mechanism to a 3.6-m-long flying robot. The demonstration shows that the robot can float stably and that the damping mechanism works correctly.

In the soft robotics field, soft structures are required for safe human interactions, adaptive shape grippers, and haptic interfaces. In contrast, rigid structures are necessary for high force transmission devices and precise position control applications. The tunable stiffness mechanism is a crucial technology for such areas, and various methods have been proposed. Fixing the segments of the string by the tension of a tendon has been studied that can stiffen the structure instantly and can constitute them with rigid materials. However, the conventional wire tensioning mechanism has a limitation in the holding torque, and the optimum segment morphology and stiffening performance is not clear. Here we show a new tendon-driven jamming mechanism called a “radial-layer jamming” that has multiple layered joints and can realize high holding torque. Three basic segment structures are presented, and the design method is shown. We measured the holding torque of the joints and compared the torque between three different designs. Our results show that all three structures can control the holding torque by the pulling force of the wire. Also, we found that the radial layer jamming can keep the joints fixed even if it had an extended structure. The holding force of the radial layer jamming did not largely decrease compared to the other structure even if the number of joints increased. These layered approaches can contribute to the performance improvement of various variable stiffness mechanisms that utilize friction.