This paper presents an active, model-based FTC (fault tolerant control) method for the dynamic positioning of underwater vehicles with thruster redundancy. Unlike conventional appraoches that rely heavily on state and parameter estimation, the proposed scheme directly utilizes the vehicle’s motion control error (MCE) to construct a residual for detecting thruster faults and failures during the steady state operation of the control system. One of the primary challenges in thruster fault identification is the unavailability of the actual control input under fault conditions. However, by conducting a detailed and rigorous analysis of the MCE variation trends associated with thruster faults, valuable information about this unknown control input can be extracted. This insight forms the foundation of the proposed FTC strategy. As for control reconfiguration, it’s straightforward since the thrust losses can be directly estimated through the fault identification process. Numerical studies with the real world vehicle model are carried out to validate the effectiveness of the proposed method.

We propose a novel whole-body multi-modal semiautonomous teleoperation framework for mobile manipulator systems, which consists of: 1) Motion capture and whole-body motion mapping to allow the operator to intuitively teleoperate the mobile manipulator without being constrained by the master interface while also fully exploiting whole-body dexterity; 2) Slave robot autonomous control to allow the mobile manipulator to optimally track the operator's whole-body command, while taking into account the user-slave kinematic dissimilarity (slave robot's joint limit, joint velocity limit, and singularity); and 3) Visuo-haptic-vestibular feedback with HMD (Head Mounted Display) for 3D visual information, wearable cutaneous haptic device for manipulation force feedback, and actuated chair for vestibular feedback to reduce HMD-induced motion sickness. Performance of the proposed framework is validated with simulation of a ROV (remotely operated vehicle) manipulator system and some preliminary user studies.

Recently, offshore plants are demanded to secure natural resources more and more and it is strongly required unmanned ones for safety of human operators and less running costs. In this paper, a practical multi-user teleoperation system is proposed for monitoring, inspection, operation, and maintenance of the unmanned offshore plants. The proposed system is developed to control mobile manipulator in a cooperative way among multiple human operators for better performance. For this, two control schemes, hand-eye coordination and disjoint axes were introduced for easier intuitive control of the mobile manipulator and for better cooperative control among multi-user, respectively. A well-known passivity-based approach, the time-domain passivity approach was, in addition, adopted to maintain system stability. And then, the proposed multi-user teleoperation system was evaluated via a human-centered method with several quantitative metrics regarding task completion time and interaction forces. Experimental results showed that the proposed multi-user teleoperation system has the benefit in tasks requiring less task completion time and interaction forces.