Three-dimensional Environment Model Research Articles

AUV path planning in a three-dimensional marine environment based on a novel multiple swarm co-evolutionary algorithm

Autonomous underwater vehicles (AUVs) are rapidly advancing in ocean exploration. High-performance path planning techniques are essential for AUVs. Path planning for AUVs is a multi-faceted challenge, necessitating careful consideration of safety, energy consumption and the influence of sea currents to ensure the development of a high-quality trajectory that satisfies all operational criteria. Existing path planning algorithms have problems such as incomplete consideration of influencing factors, computational complexity and weak applicability. Therefore, we propose a swarm intelligence optimisation algorithm based on multiple swarm co-evolution (MCO) to address the issue of AUV path planning in a three-dimensional marine environment. First, a three-dimensional marine environment model and the corresponding path evaluation mechanism are established. Second, the MCO rule is established to ensure that the MCO has balanced exploration and exploitation capabilities. A shared dynamic optimal particle between populations is introduced to ensure information exchange between populations. In addition, the cross-integration mutation strategy has been proposed for promoting the fusion of two populations of superior genes to ensure the inheritance of superior paternal genes to the offspring. Finally, four comparison experiments are designed, and the experiments compare eight commonly used intelligent search algorithms and improved versions. The results of the experiments proved that the MCO has excellent three-dimensional marine environment path planning capability, with robustness and search capabilities superior to other swarm intelligence optimisation algorithms.

Multi-mechanism swarm optimization for multi-UAV task assignment and path planning in transmission line inspection under multi-wind field

Along with the growing size of the power system, the inspection and maintenance of power lines and facilities in complicated environments will be put to a greater test. Currently, more and more research are being done on UAV-based transmission line inspection techniques, of which multi-UAV task assignment and path planning are two important aspects. This paper first generates a three-dimensional inspection environment model while considering and measuring the influence of numerous wind fields in the mountain environment. Next, a multi-indicator hybrid cost function that considers wind field influence is defined for the multi-UAV task assignment problem. An improved Bidirectional Ant Colony and discrete Honey Badger Algorithm (BACOHBA) is proposed to solve it. Then, the multi-UAV path planning problem based on the multi-wind field condition is defined, and an improved Honey Badger-Fruit Fly Algorithm (HBAFOA) is proposed to solve it. Finally, simulation experiments are conducted under different algorithms, which prove that the proposed algorithm has better performance in terms of fast-solving ability, solution accuracy, and optimization stability.

UAV 3D path planning based on improved grey wolf optimization algorithm

In this paper, an improved grey wolf optimization algorithm is proposed for the research of UAV path planning in a complex 3D environment. Firstly, a new nonlinear convergence factor is proposed to balance the performance of global search and local development. Secondly, a cubic chaotic mapping is adopted to initialize the wolf population, diversifying the population while improving the uniformity of the population distribution. Finally, a mutation operation is introduced to mutate the individual gray wolf, which enhances the ability of the algorithm to jump out of the local optimum. Three-dimensional environment model is established by elevation data. The simulation results show that the optimal fitness of the improved algorithm is improved by 2.34% compared with that before the improvement, which proves the effectiveness of the algorithm in this paper.

Multi-Conflict-Based Optimal Algorithm for Multi-UAV Cooperative Path Planning

Multi-UAV cooperative path planning can improve the efficiency of task completion. To deal with the space and time conflicts of multi-UAVs in complex environments, a multi-collision-based multi-UAV cooperative path planning algorithm, multi-conflict-based search (MCBS), is proposed. First, the flight and cooperative constraints of UAV are analyzed, and a three-dimensional environment model is established that incorporates geographical information. Then, hierarchical optimization is used to design collaborative algorithms. In the low-level path design, UAV flight constraints are combined with a sparse A* algorithm, and by improving the cost function, the search space is reduced, and the search time is shortened. In high-level cooperation, the priorities of different conflicts are set, heuristic information is introduced to guide the constraint tree to grow in the direction of satisfying the constraints, and the optimal path set is searched by the best priority search algorithm to reduce the convergence time. Finally, the planning results of the proposed algorithm, the traditional CBS algorithm, and the sparse A* algorithm for different UAV tasks are compared, and the influence of the optimization parameters on the calculation results is discussed. The simulation results show that the proposed algorithm can solve cooperative conflict between UAVs, improve the efficiency of path searches, and quickly find the optimal safe cooperative path that satisfies flight and cooperative constraints.

Effects of oyster aquaculture on carbon capture and removal in a tropical mangrove lagoon in southwestern Taiwan

Blue carbon ecosystems (BCEs) are a promising resource for the mitigation of global warming; however, climate spectrums and anthropogenic activities could influence the fragile balance of BCEs as carbon sinks or sources. We assess how oyster farming affects dissolved inorganic carbon (DIC) and total alkalinity (TA) on CO2 fluxes in a mangrove-dominated lagoon. Water physical, chemical and biological parameters were recorded by in-situ buoys within the lagoon and at its inflow. Structural equation modeling was adopted to clarify the factors/processes controlling the partial pressure of CO2 (pCO2). A three-dimensional environmental model followed by a conceptual DIC model was used to quantify the spatiotemporal patterns of capture and release of DIC and TA by oyster production. The results showed that 49% of TA and DIC released from mangroves was depleted by oyster shell formation. DIC was reduced by algal photosynthesis and algal was served as a food source supporting oyster production. Annual oyster production through phytoplankton photosynthesis accounted for 11% of the atmosphere carbon inflows, suggesting that oyster production served as a significant atmospheric/terrestrial carbon sink in the lagoon. The results indicate that mangroves benefit local oyster production by acting as an important source of DIC and TA, and that the oyster aquaculture contributed to carbon capture in a mangrove-dominated lagoon ecosystem.

Kinematic analysis and motion planning simulation of cooperative robot

Background: With the wide use of robots in electric welding and mechanical manufacturing, we need to reflect their trajectory at work, verify the effectiveness of robotic working principles and prevent unnecessary problems through simulation experiments. In order to meet the requirements of precision and controllable trajectory of robots in the assembly process, we need to model the kinematics of robots, and adopt an interpolation method to improve the kinematic accuracy of robots. Methods: To solve the problems of low accuracy and poor stability of robots in assembly trajectory, a method which combines an optimized Denavit and Hartenberg (D-H) parameter modeling method and interpolation method is presented for the first time in this paper. For this purpose, the configuration and startup files required for robot motion planning are created to configure the corresponding simulation platform of an AUBO-i5 collaborative robot. In order to study the reliability of the proposed method, a three-dimensional environment model of the manipulator is established. Then, the robot’s linear trajectory planning is realized, and thus the position changes of each joint are analyzed. Results: The simulation results show that the improved D-H method effectively improves the stability and accuracy of the motion trajectory of each joint and provides a basis for the robot to realize more flexible motion planning. Conclusions: In the assembly process, we can use the simulation platform for simulation experiments to avoid unnecessary problems. In addition, we can use the improved D-H method and interpolation method to improve the trajectory accuracy of robots. The method presented in the paper can effectively reduce the damage of the robot in the process of use and improve the assembly efficiency of robots.

A meta-heuristic assisted underwater glider path planning method

Path planning is a key technology in underwater glider navigation system, however, due to the complex and time variant ocean environment, the development of underwater path planning faces great difficulties. In this paper, a novel path planner for the underwater glider is proposed. Firstly, a three-dimensional ocean environment model is established, including seabed topographies and ocean currents. Secondly, a novel path parameterization method and a new velocity synthesis method are presented. Besides, the constrained optimization model of the underwater glider path planning is established in detail. To solve the problem, a grey wolf enhanced equilibrium optimizer (GWEEO) is put forward. In GWEEO, a grey wolf search phase is designed to improve the quality of the candidate solutions. Moreover, a well-designed competition mechanism is introduced to accelerate the convergence. In the end, different groups of simulation experiments and corresponding statistical analysis results convincingly demonstrate that the proposed algorithm can plan a satisfactory path for the underwater glider and the comprehensive performance of GWEEO is better than EO, GWO, DE and JADE algorithm.

The impacts of the hydraulic retention effect and typhoon disturbance on the carbon flux in shallow subtropical mountain lakes

A typhoon is extreme weather that flushes terrestrial carbon (C) loads and temporally mixes the entire water columns of lakes in subtropical regions. A C flux varies based on the trophic level associated with the ecological cycle related to hydraulic retention time (residence time). Herein, we sought to clarify how the hydraulic retention time and the disturbance from a typhoon affect the C flux regimes in two subtropical mountain lakes in a humid region of Taiwan with different trophic levels—oligotrophic and mesotrophic. We investigated the meteorological data and vertical profiles of the water temperature, dissolved inorganic carbon (DIC), dissolved organic C (DOC), and chlorophyll a (Chl. a) during the pre-typhoon period (April–July), during the typhoon period (August–November), and the post-typhoon period (December–March) for five years (2009–2010 and 2015–2017). We applied a three-dimensional environmental model (Fantom) to investigate the hydraulic retention effect on the net ecosystem production (NEP) using the residence time in stratified lakes. The results demonstrate that typhoon-induced mixing associated with the hydraulic retention effect plays one of the critical roles in controlling the NEP and C flux in shallow subtropical lakes.

Towards 6G: Paradigm of realistic terahertz channel modeling

Terahertz (THz) communications are envisioned as a key technology for the sixth-generation wireless communication system (6G). However, it is not practical to perform large-scale channel measurements with high degrees of freedom at THz frequency band. This makes empirical or stochastic modeling approaches relying on measurements no longer stand. In order to break through the bottleneck of scarce full-dimensional channel sounding measurements, this paper presents a novel paradigm for THz channel modeling towards 6G. With the core of high-performance ray tracing (RT), the presented paradigm requires merely quite limited channel sounding to calibrate the geometry and material electromagnetic (EM) properties of the three-dimensional (3D) environment model in the target scenarios. Then, through extensive RT simulations, the parameters extracted from RT simulations can be fed into either ray-based novel stochastic channel models or cluster-based standard channel model families. Verified by RT simulations, these models can generate realistic channels that are valuable for the design and evaluation of THz systems. Representing two ends of 6G THz use cases from microscopy to macroscopy, case studies are made for close-proximity communications, wireless connections on a desktop, and smart rail mobility, respectively. Last but not least, new concerns on channel modeling resulting from distinguishing features of THz wave are discussed regarding propagation, antenna array, and device aspects, respectively.

Exploration of Three-dimensional Environmental Supervision Model in China

Exploration of Three-dimensional Environmental Supervision Model in China

Multiple UAVs trajectory generation and waypoint assignment in urban environment based on DOP maps

This paper tackles strategic path planning for a multi-UAV routing problem in low altitude urban environment, where GNSS coverage challenges typically affect navigation performance and thus autonomous flight capabilities. These issues are addressed with a multi-step strategy that includes automated definition of GNSS-challenging volumes based on a georeferenced three-dimensional environment model, derivation of candidate obstacle-free paths between waypoints, waypoint assignment and definition of time-tagged trajectories for all UAVs. In all the steps, attention is paid to limiting the computational burden, thus ensuring applicability in real mission scenarios. Going beyond binary logics which consider GNSS-challenging volumes as obstacles, a discrete number of dilution of precision levels is considered, leading to different three-dimensional maps of the environment defined as “DOP layers”. Then, the basic idea to ensure that the designed trajectories are “flyable” with given positioning accuracy requirements is to take navigation performance into account at waypoint assignment level, using propagated covariance as a metric. The approach thus combines “navigation aware” planning with multi-vehicle task assignment, generating a solution that depends on the sensors embarked onboard the UAVs, and can be naturally extended to account for multi-sensor-based navigation architectures and ground-infrastructure support. The algorithm is tested in simulations based on a real world scenario, considering a wide combination of input parameters in terms of positioning error threshold, maximum UAV velocity, number of UAVs, navigation sensors performance, and mission epoch.

Fast Path Planning for On-Water Automatic Rescue Intelligent Robot Based on Constant Thrust Artificial Fluid Method

In this paper, fast path planning of on-water automatic rescue intelligent robot is studied based on the constant thrust artificial fluid method. First, a three-dimensional environment model is established, and then the kinematics equation of the robot is given. The constant thrust artificial fluid method based on the isochronous interpolation method is proposed, and a novel algorithm of constant thrust fitting is researched through the impulse compensation. The effect of obstacles on original fluid field is quantified by the perturbation matrix, and the streamlines can be regarded as the planned path. Simulation results demonstrate the effectiveness of this method by comparing with A-star algorithm and ant colony algorithm. It is proved that the planned path can avoid all obstacles smoothly and swiftly and reach the destination eventually.

Path planning of UAV for oilfield inspections in a three-dimensional dynamic environment with moving obstacles based on an improved pigeon-inspired optimization algorithm

In recent years, uninhabited aerial vehicles (UAV) have been used for oilfield inspections in many enterprises which can realize oilfield inspections by fewer workers. Path planning is one indispensable element in oilfield inspections through UAVs and it is also a complicated optimal problem. Now, although many researches have been focused on it, they are mainly discussed based on two-dimension planes. In practices, oilfields are complex three-dimensional spaces with many targeted points and moving obstacles between the starting and the ending point, which bring current methods some difficulties. In order to solve this problem, a three-dimensional environment model for oilfields is established for the first time, which includes: a static oil-well equipment, moving obstacles, and so on. Then, a cost function is defined to evaluate the best path, which includes: total length, average height, total time, and total electricity consumption. Finally, an improved pigeon-inspired optimization algorithm is proposed to solve problems about path planning in a three-dimensional dynamic environment of oilfields, which is named PIOFOA. In the PIOFOA, a pigeon-inspired optimization (PIO) algorithm is used to optimize the initial path and a fruit fly optimization algorithm (FOA) is used to continue local optimizations, so as to search the best path after movements of obstacles. Compared with some other methods, simulation results show that the proposed PIOFOA method is more effective.

Numerical modeling of COD transportation in Guangxi coastal bays: A short communication

A three-dimensional numerical model of Guangxi coastal hydro-dynamical environment was constructed based on ECOMSED to study the COD transport with fine grid based on latest coastline and bathymetry data. The experiment results showed that the trace of COD was mainly affected by the flood and ebb tide in coastal regions; The area in Qinzhou Bay with COD concentration exceeding 1mg/L, 3mg/L and 6mg/L on the 31th day was 60.5km2, 14.8km2 and 3.7km2 respectively. The corresponding results at Nanliu river estuary was 64.7km2, 23.1km2 and 0 km2 respectively. The COD-polluted water at the Nanliu river esturay spread more widely but no concentration larger than 6mg/L was found, which could be explained by the different topographic conditions in these two places. The vertical distribution of COD transport was approximately the same as in surface, except that the area exceeding 1mg/L decreased slightly in the middle and bottom layer.

A three-dimensional environmental hydrodynamic model, Fantom-Refined: Validation and application for saltwater intrusion in a meso-macrotidal estuary

Many three-dimensional hydrodynamic models were developed to investigate saltwater intrusion in estuaries. However, the horizontal grid discretization remains a challenge to achieve high accuracy as well as to reduce the cost in grid generation and computation. A three-dimensional hydrodynamic simulator, Fantom-Refined was developed to address this issue. A structured gridding technique which enables a flexible local mesh refinement was used for the horizontal gridding to analyze the multi-resolution phenomena from coastal bay to river upstream. The model is based on a collocated finite-volume method with second or higher-order spatial and temporal numerical schemes. The model was calibrated and validated using the data measured in a meso-macrotidal Chikugo River estuary, Japan. The simulated water level and vertical and longitudinal distribution of salinity were reasonably matched with the measured data. The salinity intrusion length (SIL) and salinity interface gradient (SIG) calculated from measured and simulated results were in good agreement with R2 value of 0.99 and 0.98 respectively. Although there were limited studies that reproduced continuous change in mixing condition from well mixed to salt wedge via partially mixed type, the present study successfully verified the change with intensive observations. The effect of channel meanderings and width on horizontal salinity distribution in the estuary was explained using the model results. Furthermore, the effect of horizontal grid resolution on saltwater intrusion and mixing conditions was investigated with three different grid resolutions and three different bathymetry resolutions. The results showed that both of the horizontal grid and bathymetry resolutions have significant effect on the prediction of the salinity distribution as well as the surface level in the estuary.

Influence Analysis of Typical Objects in Rural Railway Environments at 28 GHz

Millimeter wave (mmWave) is a key to realize high data-rate communication and enable smart railway services. There are more and more research work focusing on the algorithm and system design for railway communications in the mmWave band. A correct understanding of the mmWave channel characteristics for railway scenario is important for the estimation and evaluation of designed technologies. In this paper, the influence of typical objects in rural railway environment to the mmWave propagation channel is analyzed. Based on the channel measurement conducted at 28 GHz with train-to-infrastructure deployment in the rural railway environment, a ray tracing (RT) simulator is calibrated in terms of environment modeling and electromagnetic (EM) calculation. The dominant multipath components of the measurement are tracked and matched with corresponding objects in the propagation environment. Accordingly, dominant propagation mechanisms (direct, penetration, reflection, scattering, etc.) are determined, the three-dimensional environment model and the EM parameters of different objects are calibrated. To overcome the constraints of the measurement and analyze the influence more practically, the measurement campaign is extended to four different environment cases and four T2I deployments. With the predetermined dominant propagation mechanisms and calibrated EM parameters, reliable RT simulations are conducted. The influence of typical objects are analyzed for the considered environment cases and deployments. The analysis of this paper not only helps to understand the important influential factors of propagation channel at the object level, but also can be useful in guiding deployment of mmWave communication system. The provided EM parameters and environment modeling suggestions will enable reliable RT based channel realization in rural railway environments.

Three-Dimensional Route Planning Based on the Beetle Swarm Optimization Algorithm

Swarm intelligence algorithms have better intelligence and adaptation compared with the traditional route planning method. A three-dimensional route planning method based on the beetle swarm optimization (BSO) algorithm was proposed. The iterative updating strategy of the BSO algorithm cooperated with the search mechanism of the beetle monomer and the updating strategy of the particle swarm optimization (PSO) algorithm, thus accelerating iterative convergence and decreasing the probability of trapping in the local optimal solution of the algorithm. The practical engineering problem of three-dimensional route planning was addressed by processing uneven ground barriers using the penalty function, and a smooth route is gained from cubic spline interpolation. In this study, a three-dimensional environmental model was constructed by using actual elevation data from the USGS/NASA SRTM, and a simulation experiment of three-dimensional route planning was performed using the proposed method. The proposed method was compared with other algorithms. Experimental results demonstrated that when the iteration time was set to 50, the route planning length based on BSO algorithm was about 90% of the route planning based on the PSO algorithm. Moreover, the proposed route planning method had high convergence rate and stable convergence result and is applicable to three-dimensional route planning.

Mouse placental scaffolds: a three-dimensional environment model for recellularization

The rich extracellular matrix (ECM) and availability make placenta eligible as alternative biomaterial source. Herein we produced placental mouse scaffolds by decellularization, and structure, composition, and cytocompatibility were evaluated to be considered as a biomaterial. We obtained a cell-free scaffold containing 9.42 ± 5.2 ng dsDNA per mg of ECM, presenting well-preserved structure and composition. Proteoglycans were widespread throughout ECM without cell nuclei and cell remnants. Collagen I, weak in native placenta, clearly appears in the scaffold after recellularization, opposite distribution was observed for collagen III. Fibronectin was well-observed in placental scaffolds whereas laminin and collagen IV were strong expressed. Placental scaffolds recellularization potential was confirmed after mouse embryonic fibroblasts 3D dynamic culture, resulting in massive scaffold repopulation with cell–cell interactions, cell-matrix adhesion, and maintenance of natural morphology. Our small size scaffolds provide a useful tool for tissue engineering to produce grafts and organ fragments, as well as for cellular biology purposes for tridimensional culture substrate.

Methodology for Path Planning with Dynamic Data-Driven Flight Capability Estimation

This paper presents methodology to enable path planning for an unmanned aerial vehicle that uses dynamic data-driven flight capability estimation. The main contribution of the work is a general mathematical approach that leverages offline high-fidelity physics-based modeling together with onboard sensor measurements to achieve dynamic path planning. The mathematical framework, expressed as a constrained partially observable Markov decision process, accounts for vehicle capability constraints and is robust to modeling error and disturbances in both the vehicle process and measurement models. Vehicle capability constraints are incorporated using probabilistic support vector machine surrogates of high-fidelity physics-based models that adequately capture the richness of the vehicle dynamics. Sensor measurements are treated in a general manner and can include combinations of multiple modalities such as that through global positioning system signals, inertial mass unit outputs, and structural strain data of the airframe. Results are presented for a simulated three-dimensional environment and point-mass airplane model. The vehicle can dynamically adjust its trajectory according to the observations it receives about its current state of health, thereby retaining a high probability of survival and mission success.

Terahertz band: Channel modelling for short‐range wireless communications in the spectral windows

The channel in the terahertz (THz) band is extremely frequency selective. This study demonstrates a ray-tracing method for modelling short-range propagation channels at THz band. The propagation response of sounding bandwidth and centre frequency on power delay profile (PDP) is investigated in five spectral windows with relatively low attenuations and higher available bandwidths which could possibly offer terabit-per-second links also. In this approach, a very detailed non-cubic three-dimensional model of an ultra-broadband indoor realistic office environment has been drawn up. Furthermore, the frequency-dependent standard electrical parameters for the common building materials were taken from the literature. The transmitter (Tx) and the receiver (Rx) are 10 m apart in line-of-sight scenario with exactly same height of 1.5 m above the floor. The simulations were performed using 25 dBi horn antennas at the transmitter and receiver sides, respectively, to combat high path loss. These frequency-dependent horn antennas were designed for the respective five spectral windows. Meanwhile, the corresponding channel impulse response of multipath components with spatial and temporal information such as angle of arrival, angle of departure and time of arrival has been captured to derive PDP models. Up to four reflections (i.e. fourth order) have been considered in the modelling process.