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The prediction of the wave load on a hovercraft is essential for the design of the hull structure and safety. However, theoretical methods for the prediction of wave loads are still not mature enough due to the unique and complex nature of the air cushion structure, and numerical modeling and simulation are challenging due to the complexity of the gas-solid-liquid three-phase coupling, so the study of wave loads on hovercrafts still relies on experimentation. In this study, we aim to analyze the wave load response characteristics of a four-chamber hovercraft by conducting a wave load model test under medium/low sea states. The load components and amplitude-frequency response characteristics were thoroughly analyzed based on the acquired data of the cushion pressure, acceleration, and bending moment. The main characteristics of the wave-induced response of the hovercraft were described in detail, and an analytical relationship between the cushion pressure and hull acceleration was derived. The reliability of the experimental results was confirmed through a comparison with the derived results. The relationship between the cushion pressure and cushion volume was investigated in terms of the observed geometric volume of the air chamber, and the relationship between the cushion pressure and flow rate was analyzed to validate the derivation of the theory of wave loads on hovercrafts. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The prediction of the wave load on a hovercraft is essential for the design of the hull structure and safety. However, theoretical methods for the prediction of wave loads are still not mature enough due to the unique and complex nature of the air cushion structure, and numerical modeling and simulation are challenging due to the complexity of the gas-solid-liquid three-phase coupling, so the study of wave loads on hovercrafts still relies on experimentation. In this study, we aim to analyze the wave load response characteristics of a four-chamber hovercraft by conducting a wave load model test under medium/low sea states. The load components and amplitude-frequency response characteristics were thoroughly analyzed based on the acquired data of the cushion pressure, acceleration, and bending moment. The main characteristics of the wave-induced response of the hovercraft were described in detail, and an analytical relationship between the cushion pressure and hull acceleration was derived. The reliability of the experimental results was confirmed through a comparison with the derived results. The relationship between the cushion pressure and cushion volume was investigated in terms of the observed geometric volume of the air chamber, and the relationship between the cushion pressure and flow rate was analyzed to validate the derivation of the theory of wave loads on hovercrafts.

Fractional terminal and super-twisting as two types of fractional sliding mode controller are addressed in the present paper. The proposed methodologies are planned for both the nonlinear fractional-order chaotic systems and the nonlinear factional model of Hovercraft. The suggested procedure guarantees the asymptotic stability of fractional-order chaotic systems based on Lyapunov stability theorem, by presenting a set of fractional-order laws. Compared to the previous studies that concentrate on sliding mode controllers with unwanted chattering phenomena, the proposed methodologies deal with chattering reduction of terminal sliding mode controller/super twisting to converge to desired value in finite time, consequently. The main advantages of the offered controllers are 1) closed-loop system stability, 2) robustness against external disturbances and uncertainties, 3) finite time zero-convergence of the output tracking error, and 4) chattering phenomena reduction. Finally, the simulation results show the performance of the approaches both on the chaotic and Hovercraft models. [ABSTRACT FROM AUTHOR]

Copyright of Yıldırım Beyazıt Law Review (YBLR) is the property of Ankara Yildirim Beyazit University Law School and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

On account of the external disturbances and difficult maneuverability of a hovercraft, this paper devises a safety-guaranteed, robust, nonlinear, path-following control strategy of a hovercraft targeted for unknown dynamics, unavailable velocity, and unknown external ocean disturbances. Firstly, for the sake of accurately observing unavailable lumped disturbances and unavailable velocity measurements, a finite-time extended state observer (FTESO) is proposed. Secondly, a line-of-sight (LOS) guidance law constructed with a bounded-gain-forgetting (BGF) adaptive estimator is devised to follow the desired path while considering external environmental disturbances accurately, in which the tracking errors and the parameter estimation are both proven to be bounded. In addition, for the sake of safety, a safety-guaranteed auxiliary system that can constrain the drift angle during the hovercraft's navigation is proposed. Thirdly, the robust, nonlinear, path-following controllers achieved high tracking performance with the constructed safety-guaranteed compensation backstepping method. Finally, according to the Lyapunov and homogeneous theories, the observation error can be guaranteed to zero and the tracking error can converge to an arbitrarily small region near zero in finite time. Numerical simulations illustrate the effectiveness for the proposed robust, nonlinear, path-following scheme. [ABSTRACT FROM AUTHOR]

The measurements of airborne and underwater noise radiated by a Griffon BHT130 hovercraft were conducted in the Ural-Caspian Channel and in the North Caspian Sea. This type of hovercraft is being used for all-season cargo and crew transportation to oil and gas platforms within the environmentally sensitive area of the Ural River estuary known for its abundant bird and fish fauna. Several field campaigns were organized from 2017 to 2022 to measure and analyze acoustic noise levels simultaneously in the air and underwater at various sites and hovercraft speeds. Airborne noise levels were estimated according to ISO 2922:2020, 2021. Underwater noise study included not only acoustic pressure recordings but also particle velocity measurements with a self-designed pressure gradient sensor (PGS), which is important since the hearing of the majority of fish perceives the sound in terms of particle motion. This study is the first to report the particle velocity levels formed underwater during hovercraft passages. The minimum levels of underwater noise, 100 dB re 1 µPa (pressure), 45 dB re 1 nm/s (particle velocity), and airborne noise, 93 dBA re 20 µPa (pressure), normalized to a distance of 25 m were observed for the hovercraft passages at a cruising speed of 7–15 m/s. Thus, this speed interval can be recommended as an optimum to minimize an acoustic impact on ornitho- and fish fauna. The directivity of the hovercraft noise was estimated for the first time and utilized for noise mapping of the Ural-Caspian Channel. The possible hydrodynamic effect of a passing hovercraft is discussed. [ABSTRACT FROM AUTHOR]

In this study, a Lyapunov-based model predictive control (LMPC) method is developed to address the trajectory tracking problem of autonomous hovercrafts subjected to unknown complex disturbances from ocean environments and practical constraints of marine surface vessels, such as actuator increment limitations and saturation. Initially, the novel LMPC algorithm is applied to enhance tracking performance through rolling optimization and online optimization. Subsequently, a nonlinear disturbance observer is designed to estimate external disturbances caused by wind and dynamics uncertainties. Furthermore, to theoretically ensure control stability, contraction constraints are established using the nonlinear backstepping control method. This approach provides the essential conditions for the system's robustness and stability. Finally, the superiority and robustness of the designed LMPC trajectory tracking method are demonstrated through numerical simulations conducted in a marine environment. • Applying the LMPC algorithm to significantly enhance the hovercraft trajectory tracking performance and robustness under complex constraints. • A novel demonstration of closed-loop stability and recursive feasibility is provided for the LMPC controller design without local linearization. • Rolling optimization is applied to derive the final solution, improving control performance of the optimal solution, given the underactuated characteristics during high-speed manoeuvres of hovercrafts. [ABSTRACT FROM AUTHOR]

Considering the lumped disturbances and initial conditions limit for prescribed performance, this paper addresses a state-constrained safety trajectory tracking control scheme for a hovercraft. Firstly, model of hovercraft will be introduced. Then, adaptive prescribed-time extended state observer (APESO) is proposed to handle lumped disturbances. Secondly, considering position errors with prescribed performance relying on the initial conditions, for the sake of eliminating the dependence, a composite error transformation technique based on a continuously differentiable time-varying function is introduced. Initial errors of the hovercraft position can be compressed to a definable range. Then, virtual velocity control laws are obtained by a prescribed performance function (PPF) combined with a sliding mode. Thirdly, in order to solve problems of velocity safety constraints, an improved unified barrier function (IUBF) is introduced to limit hovercraft velocities within the asymmetric safety constraints. In addition, combined with auxiliary systems, a command filter will be introduced to reduce complex derivative calculation burden in hovercraft system controller design and avoid the phenomenon of "differential explosion". Total system states are ultimately uniformly bounded according to stability theories for cascade system. Finally, simulations illustrate the effectiveness of the proposed controller of the hovercraft. • By comparison with existing researches, aim to eliminate the dependence, a composite error transformation technique based on a continuously differentiable time-varying function is introduced. Initial position errors can be compressed to a definable set. Aim to avoid sudden compression to zero regardless of the actual value, the proposed function maximizes the initial error's original information and gently compresses it. Ignoring initial condition of position in PPC expands the application scenarios of trajectory tracking tasks for hovercraft. • Considering state constraints, aim to ensure velocities be restrained into asymmetric boundaries, a new safety controller based on IUBF is designed. Compared with previous works [62–65], the presented controller can eliminate the feasibility condition. On the other hand, compared with (Zheng et al., 2023; Wang et al., 2024c), the IUBF can be adopted to handle the systems with and without constraint concurrently and uniformly. Therefore, it is convenient for drivers to operate and expands the application scenarios of trajectory tracking tasks for hovercraft. • Aim to estimate lumped disturbances with good performance, an APESO is presented for a hovercraft. No matter what initial conditions mentioned, a design parameter can strictly prescribe the upper bound of settlement time. Compared with aforementioned finite-time ESOs (FTESOs) (Gu et al., 2019; Liu et al., 2020; Wang et al., 2021b; Yu et al., 2021) and fixed-time ESOs (FXESOs) (Zhang et al., 2019, 2020; Gu et al., 2021; Wang et al., 2022), the proposed observer has more superior. [ABSTRACT FROM AUTHOR]

ObjectivesThe operation principle of a hovercraft is different from those of conventional ship, with special stresses and much higher speeds than conventional ships. At present, the simplified fatigue strength calculation method proposed by major classification societies is not fully applicable to hovercraft, so it is necessary to put forward a suitable simplified method.MethodsAccording to the special structure and sailing mode of hovercraft, and combined with mainstream specifications, experiments and related research, this paper analyzes the working conditions, load calculations, cumulative damage derivation and other aspects, and puts forward a simplified method suitable for the fatigue analysis of hovercraft structures using a specific hovercraft as an example for calculation.ResultsThe simplified calculation results show that the fatigue life of typical longitudinal nodes meets the requirements of fatigue strength, and the analysis results of the example show that this method has certain applicability.ConclusionsThe simplified method proposed in this paper can be used as a reference for the development, design and verification of hovercraft.

On account of the external disturbances and difficult maneuverability of a hovercraft, this paper devises a safety-guaranteed, robust, nonlinear, path-following control strategy of a hovercraft targeted for unknown dynamics, unavailable velocity, and unknown external ocean disturbances. Firstly, for the sake of accurately observing unavailable lumped disturbances and unavailable velocity measurements, a finite-time extended state observer (FTESO) is proposed. Secondly, a line-of-sight (LOS) guidance law constructed with a bounded-gain-forgetting (BGF) adaptive estimator is devised to follow the desired path while considering external environmental disturbances accurately, in which the tracking errors and the parameter estimation are both proven to be bounded. In addition, for the sake of safety, a safety-guaranteed auxiliary system that can constrain the drift angle during the hovercraft’s navigation is proposed. Thirdly, the robust, nonlinear, path-following controllers achieved high tracking performance with the constructed safety-guaranteed compensation backstepping method. Finally, according to the Lyapunov and homogeneous theories, the observation error can be guaranteed to zero and the tracking error can converge to an arbitrarily small region near zero in finite time. Numerical simulations illustrate the effectiveness for the proposed robust, nonlinear, path-following scheme.

This paper presents a novel Constrained Backstepping Reinforcement Learning (CBRL) approach designed for path tracking of hovercraft. The approach addresses the challenges posed by complex modeling, multiple constraints, and large sideslip angles during high-speed maneuvers of underactuated hovercraft. Initially, a unique state constraint function is formulated, incorporating constraint boundaries related to navigation speed and path curvature. Additionally, transformations are applied to the yaw angular velocity and virtual yaw control law, ensuring that the yaw angular velocity remains within safety limits. Subsequently, a data-driven backstepping reinforcement learning optimal approach, coupled with a line-of-sight guidance law, is employed to guide the hovercraft along the intended path by regulating its yaw angle. Simultaneously, the backstepping reinforcement learning optimal control scheme is used to regulate the surge speed of the hovercraft above the resistance peak speed, thereby preventing excessive sideslip angles during path tracking. Neural network observers are integrated into the design process of both the yaw and surge controllers to monitor system dynamics in the presence of interference. Through simulation, the effectiveness and feasibility of the proposed CBRL algorithm are demonstrated. • A novel non-dependent constraint function has been introduced to limit the yaw angular velocity in relation to the speed and path curvature of the hovercraft. • A constrained backstepping reinforcement learning approach is proposed to optimize each step of yaw controller and surge speed controller. • Introducing data-driven neural network observers to monitor the comprehensive dynamics and external disturbances of the system. [ABSTRACT FROM AUTHOR]

The measurements of airborne and underwater noise radiated by a Griffon BHT130 hovercraft were conducted in the Ural-Caspian Channel and in the North Caspian Sea. This type of hovercraft is being used for all-season cargo and crew transportation to oil and gas platforms within the environmentally sensitive area of the Ural River estuary known for its abundant bird and fish fauna. Several field campaigns were organized from 2017 to 2022 to measure and analyze acoustic noise levels simultaneously in the air and underwater at various sites and hovercraft speeds. Airborne noise levels were estimated according to ISO 2922:2020, 2021. Underwater noise study included not only acoustic pressure recordings but also particle velocity measurements with a self-designed pressure gradient sensor (PGS), which is important since the hearing of the majority of fish perceives the sound in terms of particle motion. This study is the first to report the particle velocity levels formed underwater during hovercraft passages. The minimum levels of underwater noise, 100 dB re 1 µPa (pressure), 45 dB re 1 nm/s (particle velocity), and airborne noise, 93 dBA re 20 µPa (pressure), normalized to a distance of 25 m were observed for the hovercraft passages at a cruising speed of 7–15 m/s. Thus, this speed interval can be recommended as an optimum to minimize an acoustic impact on ornitho- and fish fauna. The directivity of the hovercraft noise was estimated for the first time and utilized for noise mapping of the Ural-Caspian Channel. The possible hydrodynamic effect of a passing hovercraft is discussed.

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The course control problem of hovercraft with yaw rate constraint is studied under the system uncertainty caused by model parameter uncertainties and external disturbances. Firstly, a sliding mode observer is proposed to estimate the system uncertainty, which effectively compensates the influence of uncertainty in the process of course control. Secondly, the direct method and indirect method are used to constrain the yaw rate while designing the controller with the backstepping sliding mode. The auxiliary dynamic system is used to adjust the control input in the direct method, while the auxiliary dynamic system is used to constrain the virtual yaw rate, at the same time, the barrier Lyapunov function is used to limit the yaw rate error in the indirect method. Finally, simulation results verify the effectiveness of the method proposed in the terms of uncertainty estimation and yaw rate constraint of hovercraft. It also shows that the indirect method is better than the direct method to strictly constrain the yaw rate.

This article presents the hardware requirements and the functionality of the hovercraft vehicle designed by the A-Team for the 9th "Hungarians on Mars" student competition. The article focuses on the electronic and hardware development of the vehicle as well as the design of the hovercraft controller. The article provides a detailed description of the structure of the hovercraft, and We introduce the basic mechanical model for the hovercraft. When we show the mechanical structure we collect the actuators and we would like to introduce the electric hardware which able to control these actuators. The main controller of the hovercraft is the FPGA embedded SoC (System on Chip) development board. This board provides the control signal to the electric hardware and it can move this vehicle. Finally, we introduce the own-built hovercraft created for the 9th "Hungarians on Mars". [ABSTRACT FROM AUTHOR]

Hovercraft is a modern air-cushion vehicle (ACV) that has the ability to move on a variety of surfaces, such as water and land. The distinguishing feature of the hovercraft and other vessels is that the hovercrafts are deployed on a layer of air and then propelled, which is a major factor in the faster movement of them. In fact, this is a unique feature of the hovercraft, which makes it possible to use various military, recreational, transportation, and, research limitations/implications and so on. In this paper, the numerical study of the incompressible turbulent air flow in a steady state of the hovercraft suspension system is discussed. For this purpose, hovercraft is modeled in CATIA software. After transferring to the Ansys-Fluent software and applying the boundary conditions, and solving the equations governing the problem, the results are presented as pressure, velocity and curve of the lift force. In this research, we have tried to observe the effect of changing the profile of the flow transfer part and air channel on the distribution of pressure and velocity as well as the lift force applied to the substructure. Finally, the most suitable form for the distribution of the pressure and the amount of lift force from the presented profiles was the flow transfer part profile with a gradient of 8 degrees, which showed improvement in the result from the initial profile. It was also found that the deformations applied to the channel sectional profile did not improve the rate of initial lift force of the hovercraft.

Unmanned Aerial Vehicles are extensively exploited for diverse applications importantly surveillance, defence and military, photography. Development of unmanned amphibious vehicle with integrating features of hovercraft principles and multirotor to navigate along and above the water surface, land surface and flying in the air is challenging demand. This article presents conceptual design of amphibious vehicle for the payload capacity of 7 kg with an endurance of 20 minutes and provision for mounting water sampler to collect water samples in remote water bodies. Structural strength characteristics of each part of the amphibious vehicle and integrity of same are analysed by Finite Element Analysis. FEA results indicated that the designed amphibious vehicle structure is well within the stress limit and minimal displacement is obtained. Based on structural analysis materials for various parts of the amphibious vehicle are determined and integrated structure is analysed.

Designing a controller to stabilize maneuvering hovercrafts is an important challenge in amphibious vehicles. Hovercrafts are implemented in several applications, such as military missions, transportation, and scientific tasks. Thus, to improve their performance, it is crucial to control the system and compensate uncertainties and disruptions. In this paper, both classic and intelligent approaches are combined to design an observer-based controller. The system is assumed to be both controllable and observable. An adaptive neural network observer with guaranteed stability is derived for the nonlinear dynamics of a hovercraft, which is controlled via a nonsingular super-twisting terminal sliding-mode method. The main merits of the proposed method are as follows: (1) the Lyapunov stability of the overall closed-loop system, (2) the convergence of the tracking and observer errors to zero, (3) the robustness against uncertainties and disturbances, and (4) the reduction of the chattering phenomena. The simulation results validate the excellent performance of the derived method. [ABSTRACT FROM AUTHOR]

This paper addresses a trajectory tracking control scheme based on a unified barrier function for hovercraft subject to asymmetric dynamic safety constraints. Firstly, a non-affine model of hovercraft has been built and aims to estimate the lumped disturbance, an extended state observer is utilized. Secondly, for the sake of position constraints, virtual velocity control law is obtained by utilizing a unified barrier function (UBF). Thirdly, a constraint control scheme according to UBF is presented to address asymmetric safety constraint problems of hovercraft. The proposed method can transform the original constrained hovercraft control into an equivalent "non-constrained" one and guarantee the three velocities of hovercraft within asymmetric boundaries with requirements of safe performance during motion respectively. In addition, aims to handle the issue of the virtual control law's differential explosion, and considering that the output torque of the controller should be limited to a certain range, a bioinspired neurodynamic model (BNDM) is adopted. The total system is ultimately uniformly bounded (UUB) via Lyapunov stability theories and the stability lemma of the cascade system. Finally, obtained simulation results prove the effectiveness of the proposed control scheme. • The unified barrier function-based method can eliminate this assumption of feasibility conditions and unknown virtual control coefficient. • Aim to satisfy the safety requirements when turning at high speed, yaw angular velocity is limited and will not violate safety boundaries. • To simplify design the process of control laws, a bioinspired neurodynamic model is introduced. The whole hovercraft trajectory tracking control scheme can be used as a cascade system. [ABSTRACT FROM AUTHOR]

A hovercraft can adapt to an ice area, open water, land and other environments, owing to its unique hull structure. It also plays an important role in transporting supplies, rescuing people, breaking ice and conducting other tasks. Ice load prediction is very important for structural safety and navigation of a polar ship, especially in design of air cushion icebreakers or ice breaking platforms. In this paper, based on a simplified circumferential icebreaking pattern, the icebreaking force of the hovercraft operating on the ice sheet at low speed is simulated in a numerical way. Numerical analysis of the icebreaking process with different ice thicknesses and bending strengths are performed. The numerical results are compared with model test data in a time domain for three operating cases. By analyzing the average ice force, the errors between numerical simulation results and model test measurements are less than 30%. The present study is significant for the preliminary design of new icebreaking hovercraft and it assists the operation possibility for existing hovercraft.

This paper addresses the problem of velocity tracking control for various fully-actuated robotic vehicles. The presented method, which is based on transformation of equations of motion allows one to use, in the control gain matrix, the dynamical couplings existing in the system. Consequently, the dynamics of the vehicle is incorporated into the control process what leads to fast velocity error convergence. The stability of the system under the controller is derived based on Lyapunov argument. Moreover, the robustness of the proposed controller is shown too. The general approach is valid for 6 DOF models as well as other reduced models of vehicles. Simulation results on a 6 DOF indoor airship validate the described velocity tracking methodology.

In this paper, we address the tasks of trajectory tracking (TT) and path following (PF) for a hovercraft vehicle in the presence of uncertain parameters and unknown external disturbances. Building on the backstepping technique, the proposed TT (PF) control laws are able to drive a hovercraft toward and stay within a neighborhood of a reference trajectory (path), achieving global practical stability. Moreover, the devised control strategies also guarantee that the actuations remain bounded with respect to the position error. The controller is made robust to constant external disturbances and uncertain model parameters by the introduction of dynamic estimators for the disturbance and friction coefficients. A projection operator is used to ensure the estimates remain within prescribed bounds and are sufficiently smooth to be backstepped. In order to validate the efficacy and performance of the proposed controllers, we present and analyze both simulation and experimental results. [ABSTRACT FROM AUTHOR]

A simpli!ed model of the hovercraft is used having three degrees of freedom and the control is considered as having two inputs. This paper addresses the control law problem by reformulating the problem in terms of a direct Lyapunov approach whose derivation is performed using the symbolic manipulation program Maple. The proposed solution for this controller design formulation uses the control law instead of inverse dynamics to determine the coordinate histories for the unspeci!ed axes, and represents a novel approach for the control of the underactuated system such that the control law could stabilize both the actuated and underactuated axes. Simulation of the model is carried out in the MATLAB/Simulink environment, bringing a new effective method to solve the control problem of the hovercraft, which is a dif!cult system to control because its movement is subjected to nonholonomic constraints.

This paper proposes a robust coupled multiple sliding-mode control (CMSMC) method for tracking control of underactuated hovercraft systems with nonholonomic constraints and external disturbances. First, a friction model for the hovercraft, one of the main disturbance factors, is proposed by considering viscosity, and its validity is demonstrated through experiments. Second, a disturbance model in the actual hovercraft system is estimated using a least-square-estimation-based disturbance observer. Third, pseudo forces and pseudo heading direction angle for tracking control and disturbance compensation are proposed considering the characteristics of underactuated hovercraft systems. Fourth, coupled multiple sliding surfaces (CMSSs) are newly introduced in terms of the tracking errors between the pseudo control variables and actual ones, and then, a CMSMC-based controller is proposed so that the CMSSs converge to zero within finite time in the case of zero disturbance estimation errors. In this way, three posture variables of the hovercraft converge to reference ones using only two control inputs. Finally, stability analysis and verification by simulations and experiments show that both the pseudo control tracking errors and posture tracking errors are ultimately bounded and asymptotically converge to zero when disturbance estimation errors become zero. [ABSTRACT FROM PUBLISHER]

This paper presents an integrated parameter estimator and trajectory tracking controller for a hovercraft. A generic parameter estimator for time-varying systems linear in the parameters is derived and then particularized for the dynamic model of the vehicle at hand. A trajectory tracking controller is proposed for the nonholonomic hovercraft, which renders the tracking error system exponentially stable and its zero dynamics stable. The interconnection of the estimator and the controller is proven to be locally asymptotically stable. Experimental results attesting the performance and robustness of the controller and its interconnection with the estimator are presented. [ABSTRACT FROM AUTHOR]

Many protected wetlands and (especially) fen peatlands in Poland require vegetation management to restore and maintain them as breeding areas for endangered bird species. The current practice of harvesting, baling and transporting grasses, reeds and other vegetation using tracked snow groomers and wheeled farm tractors can conflict with the nature conservation goals for these sites through disturbance of the ground surface and accidents leading to spillage of oil. To address these problems, the Industrial Institute of Agricultural Engineering (PIMR) is developing new-generation agricultural machinery that will also be applicable in formal paludiculture. This article describes an innovative method for towing large bales of harvested biomass across wetlands that minimises ground pressure using any vehicle, and the development of amphibian tracked (ATV) and hovercraft vehicles for biomass harvesting operations in wetlands.

Physical sampling of sea ice, the water mass, and subbottom geology in the Arctic Ocean is carried out from icebreakers or temporary ice camps deployed and supported by aircraft. Here, we consider an air-cushion vehicle as an alternative polar research platform to achieve self-contained operation and mobility at low operating cost. We report on five seasons of operating a hovercraft equipped as a polar research vessel with the capability to acquire geological samples and take geophysical and oceanographic measurements along with underway measurements of ice thickness. Long-distance mobility over first-year ice in the Transpolar Drift was put to the test in 2012. Considering only the time spent driving, we maintained a speed of 5–7 knots and had to travel a distance that was 1.3 times the great circle route, with an effective hover height of 0.5 m. Ice surface contrast is critical to efficient hovercraft operations in the polar pack ice. A research hovercraft can operate autonomously, serve as a temporary ice drift station, or operate jointly with an icebreaker. The fuel budget for a full year of daily hovercraft operation is consumed in a single day by a diesel-driven icebreaker.

China Undergraduate Physics Tournament is a tournament for undergraduate, is takes the team competition model. Facing on the teaching model of innovative physical experiment based on the current teaching condition, we attempt to further improve the teaching system of physics experiment in university by adopting the advanced ideas and unique pattern of this tournament. The effects of this tournament for undergraduate are explored by five stages, i. e., analyzing the question, making experimental apparatus, building theoretical model, experimental investigation, and discussion. Teaching experiment indicates that the innovative experiment based on tournament can stimulate participate enthusiasm of undergraduates, cultivate the ability of independent and systematical problem-solving for undergraduates, improve practical ability and cooperative ability for undergraduates, accelerate the process of cultivating innovative personnel. [ABSTRACT FROM AUTHOR]

In this research, a hovercraft was developed as a transportation tool to carry an I-Bylogical Enzyme (I-BE) biosensor. The main function of the biosensor is to measure the level of dangerous chemical materials from factory's liquid waste. Hence, fiber and acrylic materials, that widely known for its resistance to chemical reaction, are needed to build the hovercraft. By using Atmega 8535 microcontroller and Arduino Uno board, a remote control was choosen to navigate hovercraft's movement with support of 6 channels Transmitter Receiver. As a result, after series of tests that were carried out, indicate that the hovercraft's prototype was found to meet design and requirements expectation. [ABSTRACT FROM AUTHOR]

This paper introduces a methodology for the design, testing and assessment of incipient failure detection techniques for failing components/systems of an autonomous vehicle masked or hidden by feedback control loops. It is recognized that the optimum operation of critical assets (aircraft, autonomous systems, etc.) may be compromised by feedback control loops by masking severe fault modes while compensating for typical disturbances. Detrimental consequences of such occurrences include the inability to detect expeditiously and accurately incipient failures, loss of control and inefficient operation of assets in the form of fuel overconsumption and adverse environmental impact. We pursue a systems engineering process to design, construct and test an autonomous hovercraft instrumented appropriately for improved autonomy. Hidden fault modes are detected with performance guarantees by invoking a Bayesian estimation approach called particle filtering. Simulation and experimental studies are employed to demonstrate the efficacy of the proposed methods.

Unmanned aerial vehicles (UAVs) have gained significant attention in recent times due to their suitability for a wide variety of civil, military, and societal missions. Development of an unmanned amphibious vehicle integrating the features of a multi-rotor UAV and a hovercraft is the focus of the present study. Components and subsystems of the amphibious vehicle are developed with due consideration for aerodynamic, structural, and environmental aspects. Finite element analysis (FEA) on static thrust conditions and skirt pressure are performed to evaluate the strength of the structure. For diverse wind conditions and angles of attack (AOA), computational fluid dynamic (CFD) analysis is carried out to assess the effect of drag and suitable design modification is suggested. A prototype is built with a 7 kg payload capacity and successfully tested for stable operations in flight and water-borne modes. Internet of things (IoT) based water quality measurement is performed in a typical lake and water quality is measured using pH, dissolved oxygen (DO), turbidity, and electrical conductivity (EC) sensors. The developed vehicle is expected to meet functional requirements of disaster missions catering to the water quality monitoring of large water bodies.

This study investigates the design of a trajectory tracking constraint control method for hovercraft non-affine formulations via neural network approximation. The tracking scheme comprises an outer closed-loop of attitude and an inner closed-loop of velocity (double-loop). First, a performance function is devised to constrain the attitude errors and then a transformed error function is introduced to simplify it into an equivalent unconstrained control system. Next, an improved asymmetric integral barrier Lyapunov function is designed to address asymmetric velocity constraint problems, which can guarantee the safe turning motion or performance required at high speed. Furthermore, neural networks are employed to estimate the unknown terms of each subsystem, which solve system uncertainties and non-affine dynamics problems. The double closed-loop control system is ultimately uniformly bounded by utilizing the Lyapunov stability principle. Finally, simulation results are presented to verify the tracking performance and effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper addresses the trajectory tracking control problem of a hovercraft with asymmetrical time-varying multiple state constraints in the presence of unmodeled dynamics and external disturbances. By using the four-degree-of-freedom vector mathematical model of hovercraft, an extended state observer is adopted to provide the lumped disturbance estimation. Then, the virtual surge velocity and yaw angular velocity control laws are obtained by using a regular log-type barrier Lyapunov function to stabilize the position and yaw errors. In addition, compared with the traditional symmetric integral barrier Lyapunov function, a new asymmetric integral barrier Lyapunov function is introduced to the design process in this paper to address asymmetric state constraint problems. The surge velocity and yaw angular velocity to the inside of the boundary are analyzed to guarantee the safe turning motion or performance required at high speed, and the tracking errors of the closed-loop system are ultimately uniformly bounded by using the cascade system's stability lemma. The effectiveness of the proposed control scheme is shown via numerical simulations. • Based on practice, we not only consider the instability of surge speed below the resistance peak, but also consider the safety of high-speed navigation. Then, the surge speed is constrained bilaterally by a new asymmetric integral barrier Lyapunov function. • The yaw angular velocity is constrained to inside the asymmetrical safety limits to guarantee a safe turning motion at high speed and prevent the tail swing phenomenon caused by the drift angle and the large yaw rate. • A cascade system is formed by the proposed controller and the finite-time extended state observer. All the error signals of the whole closed-loop control system can converge into a small neighborhood around zero. [ABSTRACT FROM AUTHOR]