RBF-based supervisor path following control for ASV with time-varying ocean disturbance

1028-1036A robust model-free path following controller is developed for autonomous surface vehicle (ASV) with time-varying ocean disturbance. First, the geometrical relationship between ASV and virtual tracking point on the reference path is investigated. The differentiations of tracking errors are described with the relative motion method, which greatly simplified the direct differential of tracking errors. Furthermore, the control law for the desired angular velocity of the vehicle and virtual tracking point are built based on the Lyapunov theory. Second, the traditional proportional-integral-derivative (PID) controller is developed based on the desired velocities and state feedback. The radial basic function (RBF) neural network taking as inputs the desired surge velocity and yaw angular velocity is developed as the supervisor to PID controller. Besides, RBF controller tunes weights according to the output errors between the PID controller and supervisor controller, based on the gradient descent method. Hence, PID controller and RBF supervisor controller act as feedback and feed forward control of the system, respectively. Finally, comparative path following simulation for straight path and sine path illustrate the performance of the proposed supervisor control system. The PID controller term reports loss of control even in the unknown disturbance

Underwater dual manipulators-Part I: Hydrodynamics analysis and computation

1098-1103This paper introduces two 4-DOF underwater manipulators mounted on autonomous underwater vehicle (AUV) with grasping claws, such that the AUV can accomplish the underwater task by using dual manipulators. Mechanical design of the manipulator is briefly presented and the feature of the simple structure of dual manipulators is simulated by using Solid Works. In addition, the hydrodynamics of the manipulator is analyzed, considering drag force, added mass and buoyancy. Then, hydrodynamic simulations of the manipulator are conducted by using 3-D model with Adams software, from which the torque of each joint is calculated. This paper presents an integrated result of computed torques by combining the theoretical calculation and simulation results, which is instrumental in determining the driving torque of the manipulators

Pilot test of a fermentation tank for producing coal methane through anaerobic fermentation

The development and utilization of clean energy has long been a focus of research. In the coal bed methane field, most coal bed biogenic methane experiments are small static sample tests in which the initial conditions are set and the process cannot be batch-fed elements and microbial strains, and the gas cannot be collected in batches. Although significant results have been achieved in the coal-to-biogenic methane conversion in China, findings are restricted to the laboratory scale. No successful commercialization of coal bed biogenic methane production has been achieved yet. This study used a large-capacity fermentation tank (5 L) to conduct biogenic methane experiments. Results were compared to those from the traditional laboratory test. The gas production rate and gas concentration were higher when the 250 mL methane test volume was increased to a 5 L fermentation volume, increasing by 20.9% and 2.3%, respectively. The inhibition effect of the liquid phase products was reduced in the large fermentation tank, and the microbial activity was extended by batch feeding trace elements (iron and nickel) and methane strains and by semi-continuous collection of the gas. However, the gas conversion rate can be increased by retaining the H2 and CO2 in the intermediate gas products in the fermentation tank. The gas production rate was increased from 17.9 to 24.6 mL/g, increasing by 37.4%. The simulation pilot test can lay a foundation for the transition from a coal bed biogenic methane laboratory static small sample test to a dynamic pilot test, optimizing the process parameters to improve the reaction efficiency and move forward to commercialization test

Underwater dual manipulators-Part II: Kinematics analysis and numerical simulation

1104-1112This paper introduces dual-arm underwater manipulators mounted on an autonomous underwater vehicle (AUV), which can accomplish the underwater handling task. Firstly, the mechanical structure of the dual-arm system is briefly introduced, wherein each 4-DOF manipulator has an additional grasping function. In addition, the kinematics model of the manipulator is derived by using the improved D-H method. Secondly, the working space of the underwater dual-arm system is analyzed, which is obtained by using Monte Carlo method. The cubic polynomial interpolation and the five polynomial interpolation trajectory planning methods are compared in the joint space. Finally, with the help of the Robotics Toolbox software, the numerical test is conducted to verify the functions of the underwater dual-arm manipulator system

On stochastic dynamic analysis and assessment of bistable structures

This paper investigates some basic issues on the stochastic dynamic analysis and assessment of bistable structures from an applications perspective, illustrated with a classical spring–mass–rod structure. A complete Lagrangian-description-based Monte Carlo simulation and an Eulerian-description-based Fokker–Planck equation analysis are implemented, respectively, to capture the evolution process of the physical response probability density function, with special focus on the dynamics under the statistical steady state condition. A comparison of these two methods outlines their capabilities. As a representative example, quantitative counting and statistical analysis of the number and amplitudes of snapping-through of the structure indicate that physical quantities for structural assessment may show certain statistical regularities under the statistical steady state condition, which can be utilized efficiently to reduce the efforts of structural assessment without loss of precision

Correlative study on retinal microvascular changes and sex hormones in male patients with central serous chorioretinopathy

Central serous chorioretinopathy (CSC) is a disease in which the outer retinal barrier is damaged with high incidence in young adult males. We aimed to analyze the correlations between retinal microvascular changes and sex hormone levels. The vascular density of the superficial retinal capillary plexus (SCP), deep retinal capillary plexus (DCP), foveal avascular zone (FAZ) area, choriocapillary blood flow area, and the subfoveal choroidal thickness (SCT) were investigated by optical coherence tomography angiography (OCTA). We also determined the levels of sex hormones (adrenaline (AD), norepinephrine (NE), dopamine (DA), corticosteroids (Cor), aldosterone (ALD), estradiol (E2) and total testosterone (TT)). The relationship between sex hormone levels and OCTA parameters was then determined. We detected significantly higher levels of NE, Cor and TT in serum from the observation group than in the control group (p < 0.05). Significant correlations were identified between SCT and choriocapillary blood flow area in the affected eyes, contralateral eyes and healthy eyes in the control group (p < 0.05). SCT levels of both eyes in the observation group were higher and the choriocapillary blood flow area was smaller than in the control group. The SCT in affected eyes from the observation group were higher than the contralateral eyes (p < 0.05). The choriocapillary blood flow area was significantly smaller than in the contralateral eyes (p < 0.05). Correlation analysis unveiled that NE, Cor and TT levels were positively correlated with SCT in CSC patients and negatively correlated with choriocapillary blood flow area (p < 0.05). The serum levels of sex hormone levels in male CSC patients were different from those in healthy men of the same age. Our findings suggest that the serum levels of NE, Cor and TT levels may influence the pathogenesis of CSC by affecting SCT thickness and choriocapillary blood flow

Characterization and Analysis of Real-Time Capillary Convective PCR Toward Commercialization

Almost all the reported capillary convective polymerase chain reaction (CCPCR) systems to date are still limited to research use stemming from unresolved issues related to repeatability, reliability, convenience, and sensitivity. To move CCPCR technology forward toward commercialization, a couple of critical strategies and innovations are discussed here. First, single- and dual-end heating strategies are analyzed and compared between each other. Especially, different solutions for dual-end heating are proposed and discussed, and the heat transfer and fluid flow inside the capillary tube with an optimized dual-end heating strategy are analyzed and modeled. Second, real-time CCPCR is implemented with light-emitting diode and photodiode, and the real-time fluorescence detection method is compared with the post-amplification end-point detection method based on a dipstick assay. Thirdly, to reduce the system complexity, e.g., to simplify parameter tuning of the feedback control, an internal-model-control-based proportional-integral-derivative controller is adopted for accurate temperature control. Fourth, as a proof of concept, CCPCR with pre-loaded dry storage of reagent inside the capillary PCR tube is evaluated to better accommodate to point-of-care diagnosis. The critical performances of improved CCPCR, especially with sensitivity, repeatability, and reliability, have been thoroughly analyzed with different experiments using influenza A (H1N1) virus as the detection sample. Published by AIP Publishing

Variations in growth traits and wood physicochemical properties among Pinus koraiensis families in Northeast China

This study aimed to explore and improve the different economic values of Pinus koraiensis (Siebold and Zucc.) by examining the variations in 6 growth traits and 9 physicochemical wood properties among 53 P. koraiensis half-sib families. Growth traits assessed included height, diameter at breast height, volume, degree of stem straightness, stem form, and branch number per node, while wood properties assessed included density, fiber length and width, fiber length to width ratio, and cellulose, hemicellulose, holocellulose, lignin, and ash contents. Except for degree of stem straightness and branch number per node, all other traits exhibited highly significant variations (P < 0.01) among families. The coefficients of variation ranged from 5.3 (stem form) to 66.7% (ash content), whereas, the heritability ranged from 0.136 (degree of stem straightness) to 0.962 (ash content). Significant correlations were observed among growth traits and wood physicochemical properties. Principal component analysis identified four distinct groups representing growth traits, wood chemical and physical properties, and stem form traits. Multi-trait comprehensive evaluation identified three groups of elite families based on breeding objectives, including rapid growth, improved timber production for building and furniture materials, and pulpwood production. These specific families should be used to establish new plantations