Mobile Formation Coordination and Tracking Control for Multiple Non-holonomic Vehicles

This paper addresses forward motion control for trajectory tracking and mobile formation coordination for a group of non-holonomic vehicles on SE(2). Firstly, by constructing an intermediate attitude variable which involves vehicles' position information and desired attitude, the translational and rotational control inputs are designed in two stages to solve the trajectory tracking problem. Secondly, the coordination relationships of relative positions and headings are explored thoroughly for a group of non-holonomic vehicles to maintain a mobile formation with rigid body motion constraints. We prove that, except for the cases of parallel formation and translational straight line formation, a mobile formation with strict rigid-body motion can be achieved if and only if the ratios of linear speed to angular speed for each individual vehicle are constants. Motion properties for mobile formation with weak rigid-body motion are also demonstrated. Thereafter, based on the proposed trajectory tracking approach, a distributed mobile formation control law is designed under a directed tree graph. The performance of the proposed controllers is validated by both numerical simulations and experiments

Arbitrary Configuration Stabilization Control for Nonholonomic Vehicle with Input Saturation:a c-Nonholonomic Trajectory Approach

This paper addresses the saturated stabilization control problem for nonholonomic vehicles with a novel c-nonholonomic trajectory approach on SE(2), with applications to automatic parking. Firstly, by defining the cnonholonomic configuration, a c-nonholonomic trajectory is obtained which provides a novel approach to design stabilization controller to reach an arbitrary configuration. Secondly, a global discontinuous time-invariant feedback controller with input saturation is proposed which does not involve time signal information, and its convergence is illustrated by a Lyapunov function approach. Thereafter, the motion trajectory of the proposed controller is analyzed, and the application scenario in automatic parking with the approximate desired trajectory is demonstrated. Finally, the performance of the proposed controller is validated by both numerical simulations and experiments.</p

Full state tracking and formation control for under-actuated VTOL UAVs

In this paper, a coupled-attitude based trajectory tracking scheme is proposed to track both the position and attitude of under-actuated unmanned aerial vehicles, and its application on formation control is further demonstrated. An intermediate attitude which is composed of the desired attitude and position information is designed in a two-stage framework, wherein the first stage is the controller design of a translational subsystem and the second stage is that of an attitude subsystem. By virtue of the intermediate attitude, trajectory tracking which includes both attitude and position is realized. The proposed intermediate attitude can be viewed as a bridge connecting the position and attitude motion, and it is a new approach for both single and multiple under-actuated rigid bodies’ control. Based on the approach of coupled-attitude-based trajectory tracking, both the set point stabilization and formation tracking tasks for under-actuated vertical takeoff and landing vehicles over a directed acyclic graph can be achieved. The performances of the proposed control laws are illustrated through numerical simulations.Published versio

Robust noncooperative attitude tracking control for rigid bodies on rotation matrices subject to input saturation constraint

This paper addresses the noncooperative attitude tracking control problem for rigid bodies whose dynamics evolves on the rotation matrix (Formula presented.). First, based on the relative attitude measurement, a saturated angular velocity input is designed by a proposed saturated nonlinear function. Thereafter, the attitude tracking control torque for rigid body's dynamics with input saturation constraint and active disturbance rejection is developed by a modified dynamic surface control approach which can avoid large torque in practice. Furthermore, by using only relative attitude measurements, two types of velocity-free attitude control laws are considered, respectively. In contrast to those control schemes that require that the desired angular velocity is available to the rigid body, the proposed scheme is able to solve the attitude control in noncooperative scenarios, where the desired angular velocity and acceleration are not accessible. Since the attitude described by rotation matrix (Formula presented.) enables the controller to use local measurements in the body-fixed frame rather than global measurements in an inertial frame, the proposed robust noncooperative control schemes with input saturation constraint are easier to implement in practice. Finally, numerical simulations and SimMechanics experiments are provided to illustrate the effectiveness of the proposed theoretical results

Mobile Formation Coordination and Tracking Control for Multiple Nonholonomic Vehicles

This article addresses forward motion control for trajectory tracking and mobile formation coordination for a group of nonholonomic vehicles on SE(2). First, by constructing an intermediate attitude variable which involves vehicles' position information and desired attitude, the translational and rotational control inputs are designed in two stages to solve the trajectory tracking problem. Second, the coordination relationships of relative positions and headings are explored thoroughly for a group of nonholonomic vehicles to maintain a mobile formation with rigid-body motion constraints. We prove that, except for the cases of parallel formation and translational straight line formation, a mobile formation with strict rigid-body motion can be achieved if and only if the ratios of linear speed to angular speed for each individual vehicle are constants. Motion properties for mobile formation with weak rigid-body motion are also demonstrated. Thereafter, based on the proposed trajectory tracking approach, a distributed mobile formation control law is designed under a directed tree graph. The performance of the proposed controllers is validated by both numerical simulations and experiments

MgAl-Layered-Double-Hydroxide/Sepiolite Composite Membrane for High-Performance Water Treatment Based on Layer-by-Layer Hierarchical Architectures

One of the major challenges in the removal of organic pollutants is to design a material with high efficiency and high flux that can remove both cationic and anionic dyes, oil-in-water (O/W) emulsion and heavy metal ions. Herein, we constructed novel chemically stabilized MgAl-layered-double-hydroxide/sepiolite (MgAl-LDH/Sep) composite membranes via 3D hierarchical architecture construction methods. These membranes were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD), etc. Benefiting from the presence of hydrophilic functional groups on the surface of the film, the membranes show an enhanced water flux (~1200 L&#183;m&#8722;2 h&#8722;1), while keeping a high dyes rejection (above 99.8% for anionic and cationic dyes). Moreover, the CA membrane coupled with MgAl-LDH/Sep exhibits a multifunctional characteristic for the efficient removal of mesitylene (99.2%), petroleum ether (99.03%), decane (99.07%), kerosene (99.4%) and heavy metal ion in water due to the layer-by-layer sieving. This hierarchical architecture is proved to have excellent environmental and chemical stability. Therefore, the membrane has potential in the treatment of sewage wastewater

Towards Personalized Intervention for Alzheimer’s Disease

AbstractAlzheimer’s disease (AD) remains to be a grand challenge for the international community despite over a century of exploration. A key factor likely accounting for such a situation is the vast heterogeneity in the disease etiology, which involves very complex and divergent pathways. Therefore, intervention strategies shall be tailored for subgroups of AD patients. Both demographic and in-depth information is needed for patient stratification. The demographic information includes primarily APOE genotype, age, gender, education, environmental exposure, life style, and medical history, whereas in-depth information stems from genome sequencing, brain imaging, peripheral biomarkers, and even functional assays on neurons derived from patient-specific induced pluripotent cells (iPSCs). Comprehensive information collection, better understanding of the disease mechanisms, and diversified strategies of drug development would help with more effective intervention in the foreseeable future

eDNA Metabarcoding Analysis of the Composition and Spatial Patterns of Fish Communities in the Sanbanxi Reservoir, China

The construction of a reservoir dam alters the environment within its basin, including composition of the fish community, fish biodiversity, and the river ecosystem itself. This study was conducted in the Sanbanxi Reservoir and used eDNA metabarcoding technology comprising eDNA capture and extraction, PCR amplification, sequencing and database comparison analysis, and other environmental DNA metabarcoding standardized analysis processes to characterize the composition and diversity of fish communities and assess their current status. A total of 48 species of fish were detected. Previously, 68 species of fish were screened and identified in this reservoir based on the reports of Dai and Gu. The results for fish community composition showed that species of the order Cypriniformes are still the most dominant in the Reservoir with 38 species of cyprinids, accounting for 90.81% of all OTUs. Carp were no longer the dominant species, and Spinibarbus denticulatus, Homalopteridae, Cobitidae, and Sisoridae were not detected, with the exception of Misgurnus anguillicaudatus (Cobitidae). These families have the common characteristic of being adapted to survive in fast-water, sandstone substrate habitats. The results also show that two of the sampling sites, sbx03 and sbx10, significantly differed from other sampling sites due to their geographical environment. The impact of the construction of reservoirs on freshwater fish communities is extreme, since the transformation from a lotic to a lentic habitat contributes to habitat destruction and constrains fish in movement. The change in the aquatic environment before and after the storage of water in the Sanbanxi Reservoir has reduced the number of fish species found in the reservoir, and species characteristically found in fast moving, rapids habitats are virtually absent. The profound change in the aquatic environment from that of a lotic to a lentic habitat leads to changes in the composition of fish populations in the reservoir and to a certain extent a reduction in the ecological stability and species diversity within the reservoir. Therefore, the protection of fish diversity in the reservoir is of great significance to the stability of the ecosystem

Uncovering the hidden threat: The widespread presence of chromosome-borne accessory genetic elements and novel antibiotic resistance genetic environments in Aeromonas

ABSTRACTThe emergence of antibiotic-resistant Aeromonas strains in clinical settings has presented an escalating burden on human and public health. The dissemination of antibiotic resistance in Aeromonas is predominantly facilitated by chromosome-borne accessory genetic elements, although the existing literature on this subject remains limited. Hence, the primary objective of this study is to comprehensively investigate the genomic characteristics of chromosome-borne accessory genetic elements in Aeromonas. Moreover, the study aims to uncover novel genetic environments associated with antibiotic resistance on these elements. Aeromonas were screened from nonduplicated strains collected from two tertiary hospitals in China. Complete sequencing and population genetics analysis were performed. BLAST analysis was employed to identify related elements. All newly identified elements were subjected to detailed sequence annotation, dissection, and comparison. We identified and newly designated 19 chromosomal elements, including 18 integrative and mobilizable elements (IMEs) that could be classified into four categories: Tn6737-related, Tn6836-related, Tn6840-related, and Tn6844a-related IMEs. Each class exhibited a distinct pattern in the types of resistance genes carried by the IMEs. Several novel antibiotic resistance genetic environments were uncovered in these elements. Notably, we report the first identification of the blaOXA-10 gene and blaVEB-1 gene in clinical A. veronii genome, the first presence of a tetA(E)–tetR(E) resistance gene environment within the backbone region in IMEs, and a new mcr-3.15 resistance gene environment. The implications of these findings are substantial, as they provide new insights into the evolution, structure, and dissemination of chromosomal-borne accessory elements