Haptic shared control is a framework in which automation and the human pilot utilize the same operational input terminals to control a system. Both of their responses to automation failures are important. This paper describes the concept of adjusting the stiffness of the control stick based on the reliability of sensor systems. This helps human pilots perceive when to intervene and when to follow (just put their hand lightly on the stick) by changing the stiffness of the control stick. First, the haptic feedback design for changing the stiffness of a joystick is explained. Then, in the experiment, participants perform the task of keeping a remotely operated underwater vehicle stationary in front of a target in water stream using a joystick with three different haptic feedbacks: ours, constant high stiffness, and constant low stiffness. The experimental results indicate that our strategy increases control accuracy without increasing the human pilot's workload while allowing the human pilot to understand whether the human pilot or the automation should be currently in control of the task or action being performed. As the unexpected underwater environment adversely affects the sensor systems, our findings can be expected to play an important role in improving the control performance in the sea. Furthermore, it may inform the design of haptic feedback systems for low sensor visibility scenes.

In this study, we investigate the effectiveness of haptic shared control (HSC) for underwater vehicle operation. Underwater vehicles such as remotely operated vehicles (ROVs) and autonomous underwater vehicles are widely used for underwater maintenance and inspection. In general, ROV operators need sophisticated skills as they have to control the position and orientation of an ROV using only limited information. To improve the path tracking performance of an ROV and support its operators, we propose applying HSC by incorporating haptic feedback in a control device. We conducted a pilot experiment in a water tank using an ROV. Subjects were instructed to operate the ROV from a start line to a goal line along a desired path while watching the video image sent from the ROV camera. They were also instructed to answer questions about the colors of objects on the desired path while controlling the ROV. The results suggested that the HSC decreased their mental workload, and increased their subjective feelings of concentration on the monitor and maneuverability of the ROV while no significant difference was found in the control performance.

This manuscript describes a robot fish, the surface of which is composed of a flexible thin plastic film. Its internal mechanism, including an actuator (e.g. a servomotor), is encapsulated in the plastic film by a vacuum packaging machine. This plastic film has electromagnetic wave-transmitting properties, allowing sensors, wireless charging modules, and communication devices to be arranged within the device. To simplify the waterproofing and pressure resistance properties of the robot, the inner portion of the robot fish is filled with insulating fluid, such as industrial oil. The transmission performances of these devices, which utilize electromagnetic waves, may worsen due to the tendency of water or insulating fluids to attenuate the electromagnetic waves. This study therefore experimentally investigated the transmission performance of these devices, while taking into account the effects of water or insulating fluid. These devices were subsequently applied to our fish robot; enabling us to verify its performance by using infrared sensors to assess its autonomous locomotion.

This paper presents an image-based position measurement of underwater objects using a low-cost maritime mobile robot with a monocular camera. Visual recognition of distant underwater objects is possible in the water with high transparency, for example, in the coastal sea area of Okinawa prefecture, Japan. In this paper, we apply the proposed method to estimate the position of an old anchor that is at a deep of 30 [m] and is estimated to be hundreds-of-years-old in an archaeological site in Ishigaki Island. We explain the measurement principle of the proposed method and the developed system. Moreover, we describe the experiment conducted off the coast of Ishigaki Island and show the experimental results of the proposed method.

In this paper, we propose a pitch and roll control system based on a float-shift mechanism for small underwater robots. The proposed system presented here takes advantage of the restoring moment generated by the gravity force and the buoyancy force. The proposed system can maintain the attitude of a robot in its desired orientation. In previous works, we developed a prototype system that only controls the pitch angle of a robot. This paper extends the control system to provide roll and pitch control. In this paper, we explain the static model of the proposed system and how to control the pitch and roll angles of an underwater robot. Next, we conduct numerical analysis in order to investigate the performance of the proposed system. Lastly, we show that the proposed system is able to change the pitch and roll angles of an underwater robot though several experiments in a test tank.

Autonomous underwater vehicles are increasingly replacing the prevalent remotely operated vehicle-manipulator systems. Most current generation AUVs are not fitted with manipulators and hence are mainly limited to underwater surveying and surveillance tasks because of the difficulty in the coordinated control of the resulting underwater vehicle-manipulator systems. While several researchers have proposed various techniques for control of AUVs, there is still much research to be done on the precise control of underwater manipulators. This paper presents an intelligent control method for underwater manipulators based on the neuro-fuzzy approach. The controller is composed of fuzzy PD control with feedback gain tuning by linguistic rules. A neural network compensator approximates the dynamics of the multiple degrees of freedom manipulator in decentralized form. The proposed controller has advantages of simplicity of implementation due to decentralized design, precision, and robustness to payload variations and hydrodynamic disturbances. It has lower energy consumption compared to the conventional PD control method. The effectiveness of the proposed controller is illustrated by experimental results for a three degrees of freedom underwater manipulator.

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.

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 vehicle's horizontal attitude during motion of the manipulators.

A new method to analyze the dynamics of underwater robot manipulators is proposed in this paper. In the proposed method, hydrodynamic terms such as added mass, drag and buoyancy in dynamics of underwater robots are obtained by iterative learning control and time-scale transformation. The advantage of the proposed method is not to use parameter estimation of the dynamics. In this paper, we explain that the proposed method can be applied to hardware design, motion control and motion planning of underwater robots. Moreover, the experimental results using a 1-DOF and a 3-DOF manipulator demonstrate the effectiveness of the proposed method.