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As a cross-cutting field between ocean development and multi-robot system (MRS), the underwater multi-robot system (UMRS) has gained increasing attention from researchers and engineers in recent decades. In this paper, we present a comprehensive survey of cooperation issues, one of the key components of UMRS, from the perspective of the emergence of new functions. More specifically, we categorize the cooperation in terms of task-space, motion-space, measurement-space, as well as their combination. Further, we analyze the architecture of UMRS from three aspects, i.e., the performance of the individual underwater robot, the new functions of underwater robots, and the technical approaches of MRS. To conclude, we have discussed related promising directions for future research. This survey provides valuable insight into the reasonable utilization of UMRS to attain diverse underwater tasks in complex ocean application scenarios.

The objective of the present study was to evaluate the bioequivalence between generic and branded metformin extended‐release (ER) tablets in Chinese subjects. We tested bioequivalence in vitro and in vivo using a comparative dissolution study and a comparative pharmacokinetic trial. Safety assessments were conducted throughout the entire trial period. The dissolution profiles of the generic formulation expressed obvious extended‐release properties, similar to those of the branded formulation (f2> 60.0%). Consistent with the result of the in vitro study, no remarkable differences were found in terms of pharmacokinetic profiles between generic and branded formulations. The 90% confidence intervals of Ln AUC0‐36 h, Ln AUC0‐∞, and Ln Cmaxfrom generic formulation versus branded formulation were 91.4% to 105.0%, 91.3% to 104.7%, and 101.2% to 119.4%, respectively. During the entire trial period, 4 subjects experienced 11 adverse events. All these were mild and spontaneously resolved. The results obtained from the present study suggest that the generic and branded metformin ER tablets were bioequivalent in Chinese subjects.

The objectives of the present study were to evaluate the bioequivalence of 2 tablet formulations of prucalopride, generic and branded, and to investigate relevant pharmacokinetic and safety profiles. This study was designed as a randomized, open‐label, fasting, single‐dose, crossover, and dual‐period trial. After overnight fasting, 12 subjects were given prucalopride tablets via oral administration, and blood specimens were obtained up to 96 hours after dosing. Prucalopride concentrations in plasma were measured using ultraprecision liquid chromatography–tandem mass spectrometry followed by calculation of pharmacokinetic parameters. The safety of prucalopride was assessed throughout the study. The pharmacokinetics of prucalopride can be defined as a 2‐compartment model with a long elimination phase. No significant differences were observed between the pharmacokinetic profiles of the generic and branded prucalopride tablets. Bioequivalence was evaluated using 90%CIs for the ratio test/reference of log area under the concentration‐time curve over 96 hours, log area under the concentration‐time curve to infinity, and log peak concentration from generic and branded tablets, which were 100.06–109.94%, 100.63–110.32%, and 95.84–113.08%, respectively. During administration of the medication, there were 18 adverse events in 6 subjects in the test formulation group and 19 cases of adverse events in 6 subjects in the reference formulation group (P> .05). No severe adverse effects were detected. These results suggest that generic and branded prucalopride tablets are bioequivalent and show similar safety profiles.

To meet the requirements of the adaptive optics systems with high bandwidths and large excursion angles, we propose a fast steering mirror (FSM) with an ultrahigh natural frequency and a large angular range. The proposed FSM is driven by a preloaded piezoelectric ceramic stack actuator (PCSA), which has a higher shear stress limit in the working direction. We describe the structure of the preloading device and analyze the stiffness improvement of the preloaded PCSA. Then we introduce the structure of the proposed FSM and perform theoretical analysis based on the established static model and dynamical model. We also build an experimental setup of the proposed FSM. The experimental results show that the angular range of the proposed FSM is up to 8.4 mrad, and its first natural frequency is 6660 Hz, which surpass the performances of current FSMs.

An autonomous underwater vehicle is able to conduct coverage detections, such as sea terrain mapping and submerged objects detection, using sonar. This work addresses the task of both optimizing and following routes that present a ladder shape. First, a planning method to determine a nearly optimal coverage route is designed. The track spacing is optimized considering the seabed type and the sonar range for the purpose of increasing detection probability. It also adds adaptability to confined water, such as harbors, by decomposing the geometrically concave mission region during the processing of the environmental data. Next, a decoupled and two-layered structure is adopted to design the following controller. The route is followed in the form of sequenced-lines tracking. A proportion–integral–derivative algorithm with fuzzy parameters adjustment is employed to calculate a reference heading angle according to the transverse position deviation in designing the guidance controller. An adaptive nonlinear S-surface law is adopted to design the yaw control. The route following the method is demonstrated with sonar (including side scanning sonar and multi-beam echo sounder) imagery collected in terrain mapping and object detection through sea trials.

This article presents a navigation method for an autonomous underwater vehicle being recovered by a human-occupied vehicle. The autonomous underwater vehicle is considered to carry underwater navigation sensors such as ultra-short baseline, Doppler velocity log, and inertial navigation system. Using these sensors’ information, a navigation module combining the ultra-short baseline positioning and inertial positioning is established. In this study, there is assumed to be no communication between the autonomous underwater vehicle and human-occupied vehicle; thus, to obtain the autonomous underwater vehicle position in the inertial coordinate, a conjecture method to obtain the human-occupied vehicle coordinates is proposed. To reduce the error accumulation of autonomous underwater vehicle navigation, a method called one-step dead reckoning positioning is proposed, and the one-step dead reckoning positioning is treated as a correction to combine with ultra-short baseline positioning by a data fusion algorithm. One-step dead reckoning positioning is a positioning method based on the previous time-step coordinates of the autonomous underwater vehicle.