Visual-Aided Shared Control of Semi-Autonomous Underwater Vehicle for Efficient Underwater Grasping

Human intelligence has the advantage for making high-level decisions in the remote control of underwater vehicles, while autonomous control is superior for accurate and fast close-range pose adjustment. Combining the advantages of both remote and autonomous control, this paper proposes a visual-aided shared-control method for a semi-autonomous underwater vehicle (sAUV) to conduct flexible, efficient and stable underwater grasping. The proposed method utilizes an arbitration mechanism to assign the authority weights of the human command and the automatic controller according to the attraction field (AF) generated by the target objects. The AF intensity is adjusted by understanding the human intention, and the remote-operation command is fused with a visual servo controller. The shared controller is designed based on the kinematic and dynamic models, and model parameter uncertainties are also addressed. Efficient and stable control performance is validated by both simulation and experiment. Faster and accurate dynamic positioning in front of the target object is achieved using the shared-control method. Compared to the pure remote operation mode, the shared-control mode significantly reduces the average time consumption on grasping tasks for both skilled and unskilled operators

Design and implementation of adversarial virtual simulation training system

With a view to further enriching the college practical teaching conditions and also for the college teaching being closer to actual combat, a study is made on basis of system demand analysis in the early stage about the internal interface relationship and information/control process of the antagonistic virtual simulation training system with a key technology analysis made to lay a solid foundation for the implementation of the antagonistic virtual simulation training system

Two-Step Adaptive Control for Planar Type Docking of Autonomous Underwater Vehicle

Planar type docking enables a convenient underwater energy supply for irregularly shaped autonomous underwater vehicles (AUVs), but the corresponding control method is still challenging. Conventional control methods for torpedo-shaped AUVs are not suitable for planar type docking due to the significant differences in system structures and motion characteristics. This paper proposes a two-step adaptive control method to solve the planar type docking problem. The method makes a seamless combination of horizontal dynamic positioning and visual servo docking considering ocean current disturbance. The current disturbance is estimated and canceled in the pre-docking step using a current observer, and the positioning error is further compensated for by the vertical visual servo technique in the docking step. Reduced order dynamic models are distinctively established for different docking steps according to the motion characteristics, based on which the dynamic controllers are designed considering the model parameter uncertainties. Simulation is conducted with an initial distance of 10 m in the horizontal direction and 3 m in depth. Stable and accurate dynamic positioning under up to 0.4 m/s of current disturbances with different directions is validated. A 0.5 m lateral positioning error is successfully compensated for by the visual servo docking step. The proposed control method provides a valuable reference for similar types of docking application

Security Risk Assessment Approach for Distribution Network Cyber Physical Systems Considering Cyber Attack Vulnerabilities

With the increasing digitalization and informatization of distribution network systems, distribution networks have gradually developed into distribution network cyber physical systems (CPS) which are deeply integrated with traditional power systems and cyber systems. However, at the same time, the network risk problems that the cyber systems face have also increased. Considering the possible cyber attack vulnerabilities in the distribution network CPS, a dynamic Bayesian network approach is proposed in this paper to quantitatively assess the security risk of the distribution network CPS. First, the Bayesian network model is constructed based on the structure of the distribution network and common vulnerability scoring system (CVSS). Second, a combination of the fuzzy analytic hierarchy process (FAHP) and entropy weight method is used to correct the selectivity of the attacker to strike the target when cyber attack vulnerabilities occur, and then after considering the defense resources of the system, the risk probability of the target nodes is obtained. Finally, the node loads and node risk rates are used to quantitatively assess the risk values that are applied to determine the risk level of the distribution network CPS, so that defense strategies can be given in advance to counter the adverse effects of cyber attack vulnerabilities

Carbonate cementing minerals in rhizoliths from Badain Jaran Desert: Implication for pedo-diagenesis and environment of dune soil

Pedogenic carbonates are a good proxy of soil formation and functioning because the morphology of minerals is directly related with the processes of dissolution–precipitation. Carbonate rhizolith is one type of pedogenetic carbonate forming in modern soils of dunes and loess. The calcite micro-morphology with the sedimentary hydrogeochemical conditions prevailing during their formation remains open. Electron microscopy with an X-ray energy dispersive spectrometer and X-ray diffraction were used to investigate in detail the micro-morphology of carbonate cements of the rhizoliths and obtain paleoenvironmental information in the dune soil of Badain Jaran Desert in Northwest China. Two types of carbonates rhizoliths, primary rhizoliths (PR) and reworked rhizoliths (RR), were found. The PRs are present in situ within dune soils. The RRs are being eroded out from soil, potentially dislocated or transferred, and weathered at the soil surface. PRs displayed homogeneous micritic mass of calcite crystals, with pores, cavities and voids among the mass. RRs displayed various morphologies of calcite crystals (polyhedral, euhedral rhombic, tooth-like, prismatic and pillar), rosettes, short rods, and calcified fungal hyphae. The diagenesis differences at soil depth and surface affected the crystal morphologies. The homogeneous micritic mass of calcite crystals of the PRs were formed during the early diagenesis, preferentially in wet soils with semi-closed and semi-redox conditions. In contrast, the cementing minerals of the RRs became bigger and clearer in the late diagenesis than during early diagenesis due to recrystallization in open, dry and oxidative conditions at the soil surface. Therefore, the cement crystal morphologies of the rhizoliths can reflect the local environmental and climatic conditions. These objects can be used as environmental and pedo-diagenesis proxies in dune soil or sediments, recording the associated conditions of moisture, temperature, wind, erosion, weathering, solar radiation at the soil surface or at depth. Therefore, assessing the micromorphology of pedogenic carbonates has important implications for soil ecology and evolution as well as plant root physiology in deserts

Aerosolization Behaviour of Fungi and Its Potential Health Effects during the Composting of Animal Manure

Compost is an important source of airborne fungi that can adversely affect occupational health. However, the aerosol behavior of fungi and their underlying factors in composting facilities are poorly understood. We collected samples from compost piles and the surrounding air during the composting of animal manure and analyzed the aerosolization behavior of fungi and its potential health effects based on the fungal composition and abundance in two media using high-throughput sequencing and ddPCR. There were differences in fungal diversity and richness between the air and composting piles. Ascomycota and Basidiomycota were the two primary fungal phyla in both media. The dominant fungal genera in composting piles were Aspergillus, Thermomyces, and Alternaria, while the dominant airborne fungal genes were Alternaria, Cladosporium, and Sporobolomyces. Although the communities of total fungal genera and pathogenic/allergenic genera were different in the two media, fungal abundance in composting piles was significantly correlated with abundance in air. According to the analysis on fungal composition, a total of 69.10% of the fungal genera and 91.30% of pathogenic/allergenic genera might escape from composting pile into the air. A total of 77 (26.64%) of the fungal genera and six (20%) of pathogenic/allergenic genera were likely to aerosolize. The influence of physicochemical parameters and heavy metals on the aerosol behavior of fungal genera, including pathogenic/allergenic genera, varied among the fungal genera. These results increase our understanding of fungal escape during composting and highlight the importance of aerosolization behavior for predicting the airborne fungal composition and corresponding human health risks in compost facilities