Aerial Underwater Vehicle Research Articles

Optimization of water-entry and water-exit maneuver trajectory for morphing unmanned aerial-underwater vehicle

In this study, the problem of time-optimal trans-media maneuver trajectory design for the morphing unmanned aerial-underwater vehicles (MUAUVs) is considered. A the three-degree MUAVU dynamic model to plan the optimal flight and navigation trajectory is established. To solve the trajectory optimization model, the improved Radau pseudospectral method (RPM) is used to transform the optimal control model into a nonlinear programming problem (NLP). A double-layer hybrid solver based on the improved grey wolf algorithm and sequential quadratic programming (IGWO-SQP) is designed to solve the NLP under complex constraints. The outer layer employs an improved grey wolf optimization algorithm based on scouting strategy and the inner layer adopts a gradient-based SQP algorithm, which overcomes the disadvantage of sensitive initial value of traditional algorithm. The simulation results demonstrated that the proposed method is effective and feasible to solve the trajectory optimization of MUAUVs. A comparative study between air-water and water-air trans-media optimal trajectory verifies the proposed method which is usually applied to the aircraft is feasible to solve the underwater navigation trajectory of the MUAUV.

Nezha-Mini: Design and Locomotion of a Miniature Low-Cost Hybrid Aerial Underwater Vehicle

The distinct design concepts of the vehicles operating in air and water is one of the tremendous challenges that constrain the development of the hybrid aerial underwater vehicle (HAUV). This incompatibility consequently results in the enlarging volume and weight of the existing prototypes, as well as the unmatched maneuvering characteristics in both domains. This letter presented a novel miniaturized and lightweight HAUV, “Nezha-mini,” which weighs 953 g and is only A4-scaled. Besides, the low cost and high modularity allow the convenient repair and remanufacturing. Nezha-mini reconciles the complete multi-domain maneuverability within 50 m aerially and 6 m underwater whilst sufficing for the rapid and stable cross-domain locomotion, which benefits from the selection and unique layout of the propulsion system, as well as our proposed multi-modal control strategy and the cross-domain triggering mechanism. The results of the field experiments are in good agreement with the dynamics simulation, demonstrating the performance of multi-domain locomotion in real environments. The preliminary exploration in this letter provides a referential solution for the miniaturization of the highly maneuverable HAUVs for practical applications and creates a feasible platform for the future clustering and networking of HAUVs.

GA and RBFNN based PID for altitude-depth control of the multirotor Hybrid Aerial Underwater Vehicles

Multirotor Hybrid aerial underwater vehicle (HAUV) is the vehicle which could operate both in air and underwater powered by multi-rotors. The water-air trans-domain process is very changeling for the change of the floatage and added mass and ‘ground effect’. This paper researched on the effect of the intelligent algorithms on the trans-media control. And the genetic algorithm (GA) based and radial basis function (RBFNN) based proportional-integral-derivative (PID) controllers are developed for the trans-domain process. Then simulations and conclusions are made for these two controllers. It shows that the GA based PID controller is suitable for the trans-domain process. The RBFNN based PID controller could even do better work with the repeated optimized PID parameters value of GA. But one must pay attention to that the RBFNN-PID is very sensitive with the initial PID values. The initial values of PID parameters must be repeated optimized with GA to guarantee the better effect of the RBFNN-PID.

Experimental study on trans-media hydrodynamics of a cylindrical hybrid unmanned aerial underwater vehicle

This paper presents the experimental investigation of the hybrid unmanned aerial underwater vehicle (HAUV) hydrodynamics during the water-air trans-media process. A novel experimental platform that can control the water-air transition profile of HAUV with different velocities, accelerations, and attitudes is firstly developed with the capability of measuring the precise hydrodynamic forces of the vehicle. This technique makes it possible to perform a series of constrained model experiments to obtain the hydrodynamic forces of HAUV during the water-air transition. The hydrodynamic forces on the HAUV changing with the velocity, acceleration, and attitude of the vehicle during the transition are measured. Analysis of the test data shows that when the velocity is more than 0.1 m/s, the suction force caused by the free surface effect increases first and then remains constant with the velocity increasing. The maximum value of the suction force is about 10% of gravity. At low accelerations, less than 0.15 m/s2, the vertical force is approximately proportional to the square of time. When the attitude is less than 15°, the hydrodynamic moment first decreases and then increases to a certain value. When the attitude increases, the hydrodynamic moment decreases directly to a certain value. The influence of the moment caused by hydrodynamic forces other than time-varying buoyancy cannot be ignored. These results contribute to the design, theoretical modeling, numerical simulation, and control of HAUV.

Takeoff and Landing Control of a Hybrid Aerial Underwater Vehicle on Disturbed Water’s Surface

This article proposes a disturbance observer-based nonlinear control strategy for the accurate takeoff and landing control of a novel hybrid aerial underwater vehicle, Nezha III, subjected to wave and wind. The approach consists of the dynamic surface controller (DSC) and the nonlinear disturbance observers (NDOs). The problem is first modeled with full consideration of diverse external forces, including the capsizing buoyant moment, the added mass effect, and wave and wind loads. The DSC forms the base of the controller and benefits the tracking behavior by handling the nonlinearity of the system. Meanwhile, the integrated NDOs enhance the robustness of the closed-loop system by estimating the unmeasurable external forces. The proposed method is proved theoretically to stabilize the vehicle when it tracks the reference trajectory across different media in the presence of environmental disturbances. Finally, the proposed controller is tested numerically by challenging it under the wind and wave disturbances. The results show the controller makes Nezha III achieve successful takeoff and landing on the disturbed water’s surface in spite of the hazardous environment, which strongly evidence the outstanding performance of the proposed method.

Lifting‐principle‐based design and implementation of fixed‐wing unmanned aerial–underwater vehicle

AbstractThis paper presents the implementation of a novel proof‐of‐concept design of a fixed‐wing unmanned aerial–underwater vehicle (UAUV). The UAUV is designed on the basis of the lifting principle and has an overall density between those of water and air. During air flight, fixed‐wings are deployed to create lift to overcome gravity, similar to ordinary fixed‐wing aircraft. Moreover, the fixed‐wings generate sufficient downward lift to overcome the large net buoyancy (FB), allowing the vehicle to dive during underwater cruising. Owing to the lack of buoyancy regulation and emergency load rejection systems, the proposed UAUV is relatively simpler than those of ordinary autonomous underwater vehicles or other UAUVs. Water exit of the proposed UAUV is driven by a combination of inertial and tractor propellers in conjunction with FB, which allows smooth maneuverability during water‐to‐air transition. A series of successful water‐exit tests are used to demonstrate that the proposed UAUV can rapidly exit from water with a wide range of pitch angles, indicating strong survival capability in the future bad sea condition. This paper presents the proof‐of‐concept, including the lifting‐based principle, general design, avionics and propulsion systems, and field tests in both air and water. The vehicle performance for endurance, duration, flight speed, attitudes during water‐to‐air transitions, and landing on the water surface are also analyzed and discussed.

Dynamics and control of hybrid aerial underwater vehicle subject to disturbances

Hybrid aerial underwater vehicle (HAUV) has attracted increasing interest for its potential of operating in two distinct mediums, air and underwater. However, stable transition between medi-ums in realistic environment remains a challenge. This paper presents the dynamic model and control strategies of a quadcopter-like HAUV to enable cross-domain locomotion under ocean disturbances. An integrated model considering the complete hydrodynamic changes (added mass, inertia and damping) through the loss coefficients is formulated for the first time, which is suitable for aerial flight, underwater locomotion, and transition. Then a propulsion model about aerial propellers working at the water-air interface is established. Disturbance considered in this work was periodic wave force acting on the fuselage and instantaneous impact on propellers, the latter of which includes the impact force and the ambient density change of the propellers. Second-order sliding mode controller (SMC) is developed for the cross-domain trajectory track-ing control and is compared with the cascade proportional-integral-derivative controller (PID). Simulation results show that both controllers can track the trajectory of water egress and wa-ter ingress. However, the proposed Second-order SMC achieves faster convergence speed and greater robustness. A set of representative simulations were run to analyze the performance of these controllers with the effects of ascending speed and wave properties during the transition. The results demonstrate the inherent superiority of the proposed Second-order SMC in enabling a stable and accurate aerial-aquatic locomotion for the HAUV. Detailed analysis of several typ-ical cases illustrates the referential conditions for smooth cross-domain processes.

Trajectory Planning for Hybrid Unmanned Aerial Underwater Vehicles with Smooth Media Transition

In the last decade, a great effort has been employed in the study of Hybrid Unmanned Aerial Underwater Vehicles, robots that can easily fly and dive into the water with different levels of mechanical adaptation. However, most of this literature is concentrated on physical design, practical issues of construction, and, more recently, low-level control strategies. Little has been done in the context of high-level intelligence, such as motion planning and interactions with the real world. Therefore, we proposed in this paper a trajectory planning approach that allows collision avoidance against unknown obstacles and smooth transitions between aerial and aquatic media. Our method is based on a variant of the classic Rapidly-exploring Random Tree, whose main advantages are the capability to deal with obstacles, complex nonlinear dynamics, model uncertainties, and external disturbances. The approach uses the dynamic model of the HyDrone, a hybrid vehicle proposed with high underwater performance, but we believe it can be easily generalized to other types of aerial/aquatic platforms. In the experimental section, we present simulated results in environments filled with obstacles, where the robot is commanded to perform different media movements, demonstrating the applicability of our strategy.

Trans-Media Kinematic Stability Analysis for Hybrid Unmanned Aerial Underwater Vehicle

In recent years, hybrid unmanned aerial underwater vehicles (HAUVs), which are capable of air–water trans-media motion, have been increasingly developed. For most HAUVs, air–water trans–media motion is a relatively dangerous and difficult process. Therefore, it is of great significance to study the particular process. This paper presents the first study on the kinematic stability of the air–water trans–media motion of HAUVs. First, a simplified dynamic model of HAUVs is proposed, including the hydrodynamic forces and the time–varying buoyancy. Then, based on the proposed model and the Hurwitz method, this paper derives the air–water trans–media kinematic stability criterion for HAUVs. This criterion can be applied to most air–water trans–media motions that satisfy the assumptions in this paper. Finally, this paper takes “Nezha”, a novel HAUV, as an example to analyze its air–water trans–media kinematic stability. The results show that the proposed criterion is effective in judging the vehicle’s design, including the geometry and thruster power, which are important factors in the performance of the trans–media process.

Toward a gliding hybrid aerial underwater vehicle: Design, fabrication, and experiments

AbstractThe hybrid aerial underwater vehicle (HAUV) merges the best of unmanned aerial vehicle (UAV) and unmanned underwater vehicle into one platform makes it possible to operate in both the air and water. Various possible applications of HAUV have aroused much research on it. However, the underwater endurance and operation depth of current HAUVs are still limited. This hinders the application and popularization of HAUV in rugged environments. This paper presented the design, fabrication, and testing of a novel concept HAUV, Nezha III. It is featured by its piston‐driven underwater glide strategy and combination of an underwater glider and fixed‐wing vertical takeoff and landing aircraft. In‐depth design and evaluation of the amphibious wings with tradeoffs between aerodynamic and hydrodynamic performance in both fluids was conducted. The vehicle prototype was built, and field experiments, including domain transitions and underwater operations, were conducted in Qiandao Lake, China. Due to the experiment site constraints, the computational fluid dynamics technique evaluated horizontal flight performance with fixed wings. The experimental results show that the prototype can realize rotor flight and stable domain transitions. Moreover, this piston‐driven underwater glide strategy extended the HAUV's underwater endurance over 24 h and operational depth to 25.5 m. To the best of our knowledge, Nezha III possesses the most extended underwater endurance among existing HAUVs.

Configuration Design and Trans-Media Control Status of the Hybrid Aerial Underwater Vehicles

Hybrid aerial underwater vehicles (HAUV) are newly borne vehicle concepts, which could fly in the air, navigate underwater, and cross the air-water surface repeatedly. Although there are many problems to be solved, the advanced concept, which combines the integrated multidomain locomotion of both water and air mediums is worth exploring. This paper presents the water–air trans-media status of the HAUV from the perspective of the configuration and trans-media control. It shows that the multi-rotor HAUV is relatively mature and has achieved a stable water–air trans-media process repeatedly. The morphing HAUV is still in its exploration stage, and has achieved partial success.

Modeling, characterization and control of a piston-driven buoyancy system for a hybrid aerial underwater vehicle

This paper proposed the design and stability analysis of a piston variable buoyancy system (PVBS) with integration to a hybrid aerial underwater vehicle (HAUV). The HAUV must be lightweight and maneuverable to have sufficient endurance and reliability of operating in both underwater/air environments. To meet this crucial requirement, we designed a highly compact and lightweight PVBS to regulate the vehicle orientation and depth while operating underwater. A nonlinear motion model is firstly formulated to study the stability and control strategy of the PVBS.Frequency response analysis shows that the PVBS is inherently unstable. Therefore, a computationally affordable PID controller with a preset piston position is further developed to improve its phase response and hence make the PVBS more stable with anti-interference loss. Performance comparison between PID controllers with and without a preset piston position was conducted with simulations based on the nonlinear motion model. The effectiveness of the controller on gliding motion with different linear actuator speed are discussed based on extensive simulations. Field experiments of the designed PVBS with application to a novel HAUV named Nezha III are conducted. Results illustrate that, with the PVBS, Nezha III is able to maintain a desired vehicle pitch and heave velocity, as well as perform stable sawtooth gliding motion.

Multi-Domain Informative Coverage Path Planning for a Hybrid Aerial Underwater Vehicle in Dynamic Environments

Hybrid aerial underwater vehicles (HAUV) are a new frontier for vehicles. They can operate both underwater and aerially, providing enormous potential for a wide range of scientific explorations. Informative path planning is essential to vehicle autonomy. However, covering an entire mission region is a challenge to HAUVs because of the possibility of a multidomain environment. This paper presents an informative trajectory planning framework for planning paths and generating trajectories for HAUVs performing multidomain missions in dynamic environments. We introduce the novel heuristic generalized extensive neighborhood search GLNS–k-means algorithm that uses k-means to cluster information into several sets; then through the heuristic GLNS algorithm, it searches the best path for visiting these points, subject to various constraints regarding path budgets and the motion capabilities of the HAUV. With this approach, the HAUV is capable of sampling and focusing on regions of interest. Our method provides a significantly more optimal trajectory (enabling collection of more information) than ant colony optimization (ACO) solutions. Moreover, we introduce an efficient online replanning scheme to adapt the trajectory according to the dynamic obstacles during the mission. The proposed replanning scheme based on KD tree enables significantly shorter computational times than the scapegoat tree methods.

Publish and Subscribe-Based Formation and Containment Control of Heterogeneous Robotic System with Actuator Time Delay

This paper addresses the problem of controlling a heterogeneous system composed of multiple Unmanned Aerial Vehicles (UAVs) and Autonomous Underwater Vehicles (AUVs) for formation and containment maintenance. The proposed approach considers actuator time delay and, in addition to formation and containment, considers obstacle avoidance, and offers a robust navigation algorithm and uses a reliable middleware for data transmission and exchange. The methodology followed uses both flocking technique and modified L1 adaptive control to ensure the proper navigation and coordination while avoiding obstacles. The data exchange between all the agents is provided through the data distribution services (DDS) middleware, which solves the interoperability issue when dealing with heterogeneous multiagent systems. The modified L1 controller is a local controller for stabilizing the dynamic model of each UAV and AUV, and the flocking approach is used to coordinate the followers around the leader or within the space delimited by their leaders. Potential Field (PF) allows obstacle avoidance during the agents’ movement. The performance of the proposed approach under the considerations mentioned above are verified and demonstrated using simulations.

Propulsion performance and wake transitions of a customized heaving airfoil

The application of a flapping wing mechanism offers a vast range of development possibilities for unmanned aerial vehicles (UAVs) and autonomous underwater vehicles (AUVs). The influence of wake transitions on flapping wing mechanism’s capabilities is not fully understood particularly at low Reynolds numbers. The numerical investigation of a symmetric airfoil performing sinusoidal heaving oscillations is performed to explore the wake transitions. The influence of heaving parameters on wake transitions when exposed to a constant velocity flow is investigated. The existence of reverse von Karman vortex street, deflected wake and chaotic wake is observed. The wake deflection is found to switch its direction before transforming into a chaotic wake. The coherent structures and its evolution with the flow are presented using proper orthogonal decomposition (POD). The underlying structures and their interactions for different wake situations are identified. Correlations for the nondimensional maximum velocity in the wake in terms of frequency and amplitude is proposed. The wake dynamics is found to depend significantly on the leading edge vortices. The time-varying velocity fluctuations in the flow field are presented and discussed in detail. The velocity fluctuation contours are used to identify the regions of momentum transfer. The transient nature of the flow field is studied using the phase plot. A transition route from the periodic to chaotic regime though a quasi-periodic regime is established using time series analysis. The wake transitions are observed to be more sensitive towards heaving frequency than the heaving amplitude.

Multi-objective optimization of dive trajectory for morphing unmanned aerial-underwater vehicle

A well-planned dive trajectory is the key for the trans-media maneuver and flight control of morphing unmanned aerial-underwater vehicles (MUAUVs). The main focus of this paper is the application of a watch-based multi-objective grey wolf optimizer (MOGWO) to dive trajectory optimization problems. A multi-objective trajectory optimization model considering the change of sweep angle and static moment is developed and parameterized by the Gauss pseudospectral method, and a multi-objective nonlinear programming problem is constructed. To overcome the defect that, in the MOGWO, the rest wolves blindly follow the best wolves, the watch strategy is introduced, which provides the wolves with the ability of independent exploration. Subsequently, the watch-based MOGWO is employed to generate the Pareto front, which is compared with that obtained through other multi-objective techniques. The simulation results demonstrated that the proposed method is more reliable and can obtain more widely distributed non-dominated solutions, indicating that the watch-based MOGWO is effective and feasible in dealing with multi-objective trajectory optimization problems with complex constraints. In addition, comparative studies on optimal trajectories demonstrated that the maneuverability and gliding ability of the MUAUV are improved through cooperation between the angle-of-attack, bank angle, and sweep angle.

Беспилотная техника для целей лесного комплекса и мониторинга состояния водных объектов

Military-industrial complexes of many countries have invested billions of dollars in the industry over 120 years of development and have achieved significant progresses in the creation of surface, water and underwater equipment. Groups of military unmanned vehicles include unmanned aerial vehicles (UAVs), deck-based UAVs, water, underwater and hybrid unmanned vehicles (UAVs). Their purpose is intelligence, surveillance, strategic research projects, and military transport purposes. As for the civilian use of unmanned vehicles, this is a young industry, it is 15 years old. The beginning of the era of non-military unmanned aerial vehicles (UAVs) and then unmanned floating vehicles (UAVs) is considered to be 2006, when the US Federal Aviation Administration allowed the flights of small custom drones. At the same time, they were given a definition: a device that is remotely controlled by an operator; a device that moves along a pre-planned route. Unmanned vehicles the use of which for the purposes of the forest complex of our country is carried out or is planned to begin in the near future must meet some special requirements that are discussed in this article.

Design, fabrication, and characterization of a multimodal hybrid aerial underwater vehicle

Hybrid aerial underwater vehicle is a novelty able to fly and swim, which is extensively suitable for missions like water sampling, observing semi-submerged structure, and underwater exploration, etc. Motivated by the efficiency of fixed-wing unmanned aerial vehicles (UAVs) and underwater gliders in their own specific environments and the maneuverability of rotary-wing UAVs, this paper presents an improved design of a multimodal HAUV capable of level and vertical flight, hovering, and underwater glide. Specially, to balance flight payload and weight under water, an innovative configuration is proposed, which includes a newly developed lightweight pneumatic buoyancy system and excludes the linear actuator commonly used for pitch control of gliders. Moreover, motor arms can fold for better hydrodynamics. All these tradeoffs demand an adequate match between the fuselage aerodynamics and propulsion property, and special management of buoyancy and weight to guarantee predicted performances. Therefore, key design principles are proposed and elaborated. Based on the principles, a prototype, named Nezha III, was fabricated and tested. The prototype’s performance characterization in the regions of underwater, flight, and water/air transition are presented. The results demonstrate the desired performance of the prototype under different modes, and notably prove its outstanding capability of diving to 50 m depth.

Constrained adaptive backstepping take-off control for a morphing hybrid aerial underwater vehicle

This paper studies the inclined take-off control for a kind of morphing hybrid aerial underwater vehicles. At the initial stage, the hybrid aerial underwater vehicle could not achieve trim condition for the low speed. Then the altitude could have an obvious decrease during the take-off process. This could lead the vehicle to crashing into water. To escape from the unbalanced stage, an adaptive backstepping controller is designed to track the target angle of attack and the thrust is opened to maximum within limitation. The radial basis function Neural Networks and parameter adaption are employed in order to deal with the time-varying nonlinear variable sweep dynamics of the vehicle. Bisides, the control input of the elevator deflection is easy to be saturated for the low initial velocity. This is taken into account in the design of a constraint adaptive backstepping controller to prevent aggressive adaptions and to provide reliable input commands. Simulations are presented to varify the proposed controller.

Predictive and sliding mode cascade control for cross-domain locomotion of a coaxial aerial underwater vehicle with disturbances

This paper presents the system design, dynamic model of a novel coaxial aerial underwater vehicle, and proposes an improved cascade control strategy to enable cross-domain locomotion of the vehicle in disturbance environments. The proposed aerial underwater vehicle merges the design of the coaxial rotor system and the foldable propeller for operating effectively in both mediums and transitioning between them. The vehicle’s continuous dynamics model is formulated based on the Newton-Euler equation considering time-varying environmental disturbances. Then, a predictive and sliding mode cascade control is developed and applied for motion control of the vehicle to perform cross-domain transitions, especially compensating for the effect of buoyancy variance with feedforward control. Finally, the feasibility and robustness of the proposed control scheme are verified by comparative simulation results with the PID controller.