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, attitudemaintenance control was conducted. Results show that the proposed system can maintain the vehicle's horizontal attitude during motion of the manipulators.
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.
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.
We examined the correlation between jump distance and the maximum flexion angle of the knee joint during jumping to evaluate whether healthy men adjust to jump distance by changing the angle of the knee joint. Fourteen subjects jumped 3 times with their eyes closed to each of what they thought was 25%, 50%, and 75% of their maximum jump distance, a total of 9 jumps for both the vertical and standing broad jump. We measured the knee joint flexion angle at the time of the motion and examined the correlation between jump distance and knee joint flexion angle. The results show a relationship between jump distance and knee joint flexion angle for both the vertical and standing broad jump. We determined that jump distance is controlled by knee joint flexion angle in healthy men. Thus, a factor of jump control was clarified in this study.
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