In this study, we propose a new robot system consisting of a mobile robot and a snake robot. The system works not only as a mobile manipulator but also as a multi-agent system by using the snake robot's ability to separate from the mobile robot. Initially, the snake robot is mounted on the mobile robot in the carrying mode. When an operator uses the snake robot as a manipulator, the robot changes to the manipulator mode. The operator can detach the snake robot from the mobile robot and command the snake robot to conduct lateral rolling motions. In this paper, we present the details of our robot and its performance in the World Robot Summit.

The movement capabilities of snake robots allow them to be applied in a variety of applications. We realized a snake robot climbing in crowded pipes. In this paper, we implement a sinusoidal curve control method that allows the snake robot to move faster. The control method is composed of a hybrid force–position controller that allows the snake robot to move more stably. We conducted experiments to confirm the effectiveness of the proposed method. The experimental results show that the proposed method is stable and effective compared to the previous control method that we had implemented in the snake robot.

An operator feels a burden when he/she controls a rescue robot remotely because he/she has to keep watching camera images to find the target object. We think that this burden can be reduced by the combination of Head Mounted Display (HMD) and object recognition by deep learning. In the first half part of this study, we examine the effect that how presentation method by You Only Look Once (YOLO), a deep learning algorithm, and its recognition results to an operator wearing HMD. In the experiment, three methods of presentation were set: no display of object recognition, display only one object recognition result, and display 80 kinds of object recognition results. Under each presentation method, we measured the time it took for the operator to operate the robot and complete the given task. Additionally, we ask a questionnaire for each experiment. The results of the questionnaire showed that the method to present only one object recognition result was useful. In the second half part of this study, we develop a system to present 3D images with YOLO added, to further ease the burden of object search. Furthermore, we numerically prove that this system represents depth. In the experiment, two methods of displaying were set up: 2D images with Bounding Box (BB) by YOLO and 3D images with BB by YOLO. For each method of presentation, the operator operated the robot and recorded the number of objects found within a time limit. Additionally, we asked a questionnaire at the end of the search in each condition and at the end of all the experiments. The results of the questionnaire suggested points that need to be improved. Furthermore, we consider the flicker of the image found in the experiment.

When a snake robot explores a collapsed house as a rescue robot, it needs to move through various obstacles, some of which may be made of soft materials, such as mattresses. In this study, we call mattress-like environment as a soft floor, which deforms when some force is added to it. We focused on the central pattern generator (CPG) network as a control for the snake robot to propel itself on the soft floor and constructed a CPG network that feeds back contact information between the robot and the floor. A genetic algorithm was used to determine the parameters of the CPG network suitable for the soft floor. To verify the obtained parameters, comparative simulations were conducted using the parameters obtained for the soft and hard floor, and the parameters were confirmed to be appropriate for each environment. By observing the difference in snake robot’s propulsion depending on the presence or absence of the tactile sensor feedback signal, we confirmed the effectiveness of the tactile sensor considered in the parameter search.

This study describes a method for applying an extended Kalman filter to a snake robot, which moves through a pipe using a helicoidal rolling motion. The filter estimates the helix radius, amount of twisting, and helix pitch to adapt to changes in the diameter inside the pipe. Additionally, offset values are added to these estimated values to propel the snake robot along the pipe autonomously. In particular, we experimentally demonstrated the effect of helix pitch on friction force and proposed a parameter-setting strategy that accounts for the range of motion of the joints. Finally, we validated the results of the proposed method through experiments on an actual robot.

Soft actuators capable of flexible motion have been actively studied and developed. Soft actuators that can extend and bend have been developed; however, soft rotary actuators have rarely been reported. In our previous studies, a soft rotary actuator (SRA) that generates rotational motion by constraining extension-type soft actuators (EFPAs) in a spiral shape was developed. However, the SRA had the limitation of rotating only in one direction, either clockwise or counterclockwise. In this paper, we aim to develop a symmetric bidirectional soft rotary actuator (SB-SRA) that achieves comparable rotational performance in both clockwise and counterclockwise directions while maintaining the flexibility of polymeric materials, such as rubber, and allowing static hysteresis adjustment. In particular, arranging several EFPAs so that they do not interfere with each other during extension enables the SRA to generate both clockwise and counterclockwise rotational motion. Unlike previously reported unidirectional soft rotary actuators, and unlike rigid antagonistic bidirectional joints that require bearings and a dedicated brake, the proposed SB-SRA achieves symmetric bidirectional rotation with a bendable rotational axis and enables static hysteresis compensation using only the opposing actuators. The results show that the maximum rotation angle and torque of the SB-SRA are approximately 105° and 0.51 Nm, respectively, under an input pressure of 500 kPa. The maximum directional differences between clockwise and counterclockwise operation were 3.3% for the rotation angle and 2.4% for the torque, demonstrating approximately symmetric output characteristics. In addition, static hysteresis adjustment can be achieved by varying the supply pressures applied to the opposing EFPAs.