Mizuho Shibata

Rolling tensegrity driven by pneumatic soft actuators

In this paper, we describe the rolling of a tensegrity robot driven by a set of pneumatic soft actuators. Tensegrity is a mechanical structure consisting of a set of rigid elements connected by elastic tensional elements. Introducing tensegrity structures, we are able to build soft robots with larger size. Firstly, we show the prototype of a six-strut tensegrity robot, which is driven by twenty-four pneumatic McKibben actuators. Second, we formulate the geometry of the tensegrity robot. We categorize contact states between a six-strut tensegrity robot and a flat ground into two; axial symmetric contact and planar symmetric contact. Finally, we experimentally examine if rolling can be performed over a flat ground for individual sets of the actuators and discuss the strategy of rolling.

Crawling by body deformation of tensegrity structure robots

In this paper, we describe the design of a deformable robot with a tensegrity structure that can crawl and we show the results of experiments showing the ability of these robots to crawl. We first describe a tensegrity structure, composed of struts and cables, and its characteristics. We next explain the principle of crawling by robot body deformation, followed by a classification of the methods by which a body can be deformed and the contact conditions of the robot through the cable-graph of the tensegrity structure. We also describe topological transition graphs that can visualize crawling from each initial contact condition. We then discuss the characteristics of the proposed robot in terms of design freedom. Finally, we show experimentally that the prototype of a tensegrity robot can crawl.

Development of a human-sized ROV with dual-arm

In this paper, we describe the development of a human-sized remotely operated vehicle (ROV) with dual-arm. The developed ROV was designed to perform biological researches, geological researches and archaeological explorations in Lake Biwa, the biggest lake in Japan. This ROV has two distinguishing characteristics: one is a dual-manipulator system and the other is an attitude control system. The size of the manipulators is related to the size of a human arm so that the ROV can do work that human divers usually do using the arms. The attitude control system is capable of keeping the vehicle in a horizontal plane, and purposely changing the vehicle attitude angle. Additionally, we developed a new master-slave controller system for this ROV. Some fundamental experiments in a diving pool were performed in order to test the capabilities of the developed ROV. After those experiments, a field trial was conducted in Lake Biwa and the ROV carried out some works at a depth of about 10–20 meters.

An attitude control system for underwater vehicle-manipulator systems

As described in this paper, we propose an attitude control system for underwater vehicle/manipulator systems (UVMSs) based on control of the position of the center of buoyancy with respect to the center of gravity. Control of the center of buoyancy is accomplished using movable float blocks. The attitude control system is useful to control the pitch angle of UVMSs to enhance their performance and to improve their efficiency of underwater operations. A UVMS that has two 5-degree-of-freedom (DOF) manipulators was developed to verify the effectiveness of the proposed attitude control system. This paper presents a numerical study and some experimental results obtained using the UVMS with the attitude control system. We experimentally confirmed that the proposed system can change the pitch angle of the vehicle between −120 and +105 deg. In another experiment, attitude-maintenance control was conducted. Results show that the proposed system can maintain the vehicles horizontal attitude during motion of the manipulators.

Rolling Locomotion of Deformable Tensegrity Structure

In this paper, we propose that a deformable robot with a tensegrity structure can crawl and describe its performance in practical experiments and a gait description. We apply Miller index in crystallography to describe the gait of a prototype, and then classify two contact conditions of the prototype. We demonstrate rolling of a six-strut tensegrity to confirm the movement of the prototype from each contact condition.

Active shaping of a tensegrity robot via pre-pressure

This paper describes active shaping of a tensegrity robot by pre-pressure applied to pneumatic actuators that drive the robot. The pre-pressure helps to reduce unevenness of deformation properties of pneumatic actuators. We experimentally examined if transitions among contacts can be performed under pre-pressure using our prototype of a six-strut tensegrity robot. Based on the experimental results, we have found that all transitions between two neighboring contacts can be performed by activating one of twelve actuator pairs.

Development of an Underwater Robotic Inspection System using Mechanical Contact

This paper reports the development of a robotic inspection system using a mechanical contact mechanism that enhances the positioning stability of a small and lightweight underwater robot to take clear images of underwater targets and to work with manipulators for inspections under external disturbances. As described in this paper, first we perform a two-dimensional numerical analysis based on force and moment acting on an underwater robot with a contact mechanism. Second, we experimentally investigate the friction coefficients of several soft and high friction materials for the contact points of a prototype contact mechanism to enhance the positioning stability of the robot. Based on the results of numerical analysis and the experimental investigation, we design and develop a prototype contact mechanism for an underwater robot. Moreover, we experimentally test the stability of the underwater robot with the contact mechanism in a test tank. Finally, a ship hull inspection is conducted as a field test in a port using the robot with the developed contact mechanism. The experimentally obtained results indicate that the proposed contact mechanism is a useful tool for underwater visual inspections and manipulator tasks of a small and lightweight underwater robot.

Fabrication of a fish-like underwater robot with flexible plastic film body

A portable underwater robot that has a high pressure resistance is required for easy observations in wide area. In this manuscript, we discuss the fabrication and design of a fish-like underwater robot that the outer body is composed by a flexible thin plastic film. Force generated by the differential pressure between inside and outside of the robot is zero due to the flexibility. Therefore, the plastic film of the robot does not ideally break under high pressurized environment. The entire body of the robot is fabricated by a vacuum packaging machine. We call this fabrication robot packaging. The design guide of our fish-like robot depends on the density of insulating fluid containing within the body. Even the fluid is lighter or heavier than water, we can construct the fish-like robot that is at neutral buoyancy Graphical Abstract

Preliminary experiments of a human-portable underwater gripper robot for dexterous tasks

This paper reports the development and experiments of an underwater 6-DOF gripper robot. The developed gripper robot is a human-portable remotely operated vehicle (ROV) that weighs approximately 31 kg in air. The most important feature of this robot is that it can grasp cylindrical objects of 50-500 mm diameter, and handle them in 6 DOF. We also developed a dedicated operating device to use the gripper robot effectively. To reduce the operator burden during underwater tasks, several software functions of the operating device are provided, such as thrust allocation, depth control, and pitch angle control. Experiments in a test tank demonstrated the motion performance of the developed robot and the effectiveness of the operating device.

Design and development of an attitude control system for a human-sized ROV

In this paper, we present the design and development of an attitude control system for a human-sized ROV (Remotely Operated Vehicle) with a dual-manipulator system. The main operations of the ROV are sampling operations for biological researches, geological researches and archaeological explorations in Lake Biwa, the biggest lake in Japan. In order to achieve these operations, we propose an attitude control system and explain the availability of the proposed system in this paper. For the design of the attitude control system, simulation analysis was conducted. Based on the analysis, a pitch angle control system was designed and developed as the prototype of the attitude control system. An experiment was conducted in a test tank to demonstrate the effectiveness of the proposed system. The result shows that the developed system is useful for pitch angle control of the ROV.