Air Cushion Vehicle Research Articles

Design of ACV Controller by Using the Image Information of Two Cameras

A kind of an air cushion vehicle (ACV) is known as a hovercraft which carries out a cruise by blowing off the air from the bottom of the body. The ACV has many advantages, such as amphibian vehicle, large payload, and so on. However, the ACV has drawbacks such as its drivability and controllability are bad. An improvement of the drivability is effective for the control of the ACV and the disturbance rejection performance of the controller is very significant. In this research, the position of the ACV is estimated with the image information of two cameras. When the ACV runs on the straight line, the ACV is kept on the line by the designed controller. The usefulness of the designed controller is confirmed through the simulation and an experiment.

Four-degree-of-freedom course stability of an air cushion vehicle

A four-degree-of-freedom mathematical model was established to investigate the course stability of an air cushion vehicle (ACV). The forces of aerodynamic, propeller and rudder were obtained by wind tunnel experiments. A series of constrained model experiments with horizontal-planar-motion-mechanism (HPMM) were conducted to determine the hydrodynamics. The ACV’s course stability was analyzed by using Hurwitz determination method with differential equation of perturbation, and the four-degree-of-freedom course stability was then checked by simulated calculation. The analysis and simulation results show that the course stability of four-degree-of-freedom is applicable to ACV and is stricter than that of two-degree-of-freedom.

352 二台のカメラ画像情報を利用したACVコントローラの設計(アクチュエータ,軌道計画,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

A kind of an air cushion vehicle (ACV) is known as a hovercraft which carries out a cruise by blowing off the air from the bottom of the body. The ACV has many advantages, such as amphibian vehicle, large payload, and so on. However, the ACV has a defect that drivability is bad, and it is difficult to control. An improvement of the drivability is effective for the control of the ACV and the influence reduction of the disturbance is very significant. In this research, the position of the ACV is estimated with the image information of two cameras. The usefulness of the designed controller is confirmed through the simulation and an experiment.

Load distribution for an intelligent air-cushion track vehicle based on optimal power consumption

This study incorporates the computation of load distribution for an intelligent air-cushion track vehicle (IACTV) based on optimal power consumption (PC). A novel design auto adjusting air-cushion system has been designed and developed to minimise the PC. Focusing on optimising total PC, three main issues were studied in this paper. First, a theoretical model is developed for optimising total PC of the vehicle and the effects of load distribution on total PC. Second, a fuzzy expert system (FES) is used to control the swamp tracked vehicle's intelligent air cushion system and thus minimise the PC. Third, an artificial neural network (ANN) model has been developed which has been trained to predict the total PC for IACTV and to provide illustration how FES might play an important role in the prediction of PC of the vehicle's intelligent air-cushion system.

Practical Evaluation of Steady Flow Resulting from a Free-Surface Pressure Patch

The linearized potential flow resulting from a distribution of pressure that advances at constant speed along a straight path at the free surface of calm water, of effectively infinite depth and lateral extent, is considered. A practical method for evaluating the free-surface elevation caused by the moving free-surface pressure patch—which can be used to model steady flows of air-cushion vehicles, high-speed planing boats, surface-effect ships, and some types of hybrid ships—is given. The key ingredient of this method is a highly simplified analytical approximation to the local-flow component in the expression for the Green function associated with the classic Michell-Kelvin linearized free-surface boundary condition.

GENERALITY ON AIR CUSHION VEHICLE DESIGN AND APPLICATIONS

This paper aims at an introduction of an hybrid- marine vehicle - hovercraft or air cushion vehicle. Due to its original principle of operating, lightly different to the classical displacement ship, some remarks on the design and building are dicussed. The abilities for the exploitation of this type of vehicle is then mentioned taking into account the feasible design, ship registration and new building (prototype).

A study of maneuvering control for an air cushion vehicle based on back propagation neural network

A back propagation (BP) neural network mathematical model was established to investigate the maneuvering control of an air cushion vehicle (ACV). The calculation was based on four-freedom-degree model experiments of hydrodynamics and aerodynamics. It is necessary for the ACV to control the velocity and the yaw rate as well as the velocity angle at the same time. The yaw rate and the velocity angle must be controlled correspondingly because of the whipping, which is a special characteristic for the ACV. The calculation results show that it is an efficient way for the ACV’s maneuvering control by using a BP neural network to adjust PID parameters online.

Sea keeping analysis of air cushion vehicle with different wave angles under the operation resistance

The air cushion vehicle (ACV) sea keeping characteristic under different wave directions with the operation resistance is discussed with the couples of the heave, pitch roll motion and the pressure of the cushion. In previous researches, only wave and cross wave direction were discussed. Then a Matlab program is made to calculate the united frequency responses of heave, pitch and roll amplitude of the craft, under different wave frequencies and different wave directions. The results of the research depict some dangerous situations under which the sympathetic vibration happens in heave, pitch and roll motion and the amplitudes are extremely higher than those under the ordinary conditions. These results will be helpful in ACV design and operation.

Nonlinear FEM Simulation of Air Cushion Vehicle (ACV) Skirt Joint Under Tension Loading

AbstractThe mechanical properties of an air cushion vehicle (ACV) skirt cloth, which is a nonlinear rubber‐coated fabric, are tested on a Series IX 4465 electron tension machine manufactured by Instron Company. Compared with the Mooney–Rivlin and Ogden form, the second‐order Mooney–Rivlin form agrees with the model test result better. The ultimate bearing capacity of an ACV skirt joint structure is tested on a mechanical tension machine and the ultimate load is recorded manually. Then, considering the contact effect of each assembly and the large‐displacement of skirt elements, a nonlinear finite element method (FEM)‐based simulation process of an ACV skirt joint structure under tension loading is presented. The simulation process comprises three steps: assembly of parts, bolts' tightening, and tensioning the skirt cloth. Under these loadings, the stress distribution and deformation of the skirt cloth, and the cloth broken locations and directions are obtained. These results agree well with the test results. As for the ultimate bearing capacity of the skirt joint, the simulation result is slightly smaller than the test result. Thus, this FEM‐based simulation method is proven to be reliable and relatively conservative.

Pitch Control for a Semi-track Air-cushion Vehicle Based on Optimal Power Consumption

Pitch Control for a Semi-track Air-cushion Vehicle Based on Optimal Power Consumption

The computing of the optimal power consumption for semi-track air-cushion vehicle using hybrid generalized extremal optimization

A new stochastic method named hybrid generalized extremal optimization (HGEO) is proposed in this paper. It combines genetic algorithms (GAs) and generalized extremal optimization (GEO). In order to extend GEO’s mutation operator to accelerate convergence speed and be easily incorporated into HGEO, the real coded GEO is first developed to population-base GEO (PGEO), and then incorporated into the HGEO in the paper. Constraints consideration for using the HGEO and the effects of related operators are also investigated. Finally, the performance of the HGEO is fully investigated compared with other related algorithms to find the optimal power consumption for the semi-track air-cushion vehicle (STACV). The results show that the HGEO has better performance than GAs or other related simpler algorithms.

공기부양선의 추진 및 부양축계 횡진동 해석에 관한 연구

공기부양선의 추진 및 부양축계 횡진동 해석에 관한 연구

Wave resistance of an air-cushion vehicle in unsteady motion over an ice sheet

Unsteady rectilinear motion of an air-cushion vehicle over an ice sheet at various speeds is considered. Ice is modeled by a viscoelastic ice plate. The effects of the basin depth, the thickness and relaxation time of ice, vehicle length, acceleration, deceleration, and speed of uniform motion on the wave resistance of the vehicle are analyzed. Maneuvering methods for increasing or lowering the wave resistance of the vehicle are proposed.

Complete flow field computation around an ACV (air-cushion vehicle) using 3D VOF with Lagrangian propagation in computational domain

In this study an algorithm and a 3D solver is developed to solve the flow field around air-cushion vehicles (ACV) in vicinity of free surface. A single set of dimensionless equations is derived to handle both liquid and air phases in viscous 3D incompressible free surface flows in general curvilinear coordinates. The momentum equations are solved using the SIMPLE method in a staggered grid. The Lagrangian approach in the computational domain is also applied in the context of the VOF method to resolve the free surface. To demonstrate the robustness and versatility of the code, an application of this method on the impact problem of a circular cylinder is presented that is compared to experimental, theoretical and other computational results. In a 3D problem, the gravity-fill test is solved in both Cartesian and randomly generated curvilinear grid system. Comparison of results with the available experimental data and other numerical results is presented as well. At last, the code is applied to solve the two and three dimensional air and water flow field around an ACV and the effects of several parameters including the under skirt pressure distribution, initial air gap and effect of Fr. number on the wave elevation and wave making drag are investigated. It is shown that the presented method and the code are, robust and accurate enough to produce complicated 3D flow fields around ACV’s.

공기부양선의 추진 및 부양축계 종진동 해석에 관한 연구

In this study, axial vibration analysis has been conducted on a propulsion and lift shafting system for an air cushion vehicle using ANSYS code. The shafting system is totally flexible multi-elements system including wood composite material of air propeller, aluminum alloy of lift fan and thin walled shaft with flexible coupling. The analysis calculated the axial natural frequencies and mode shapes of the shafting system taking into account an equivalent mass-elastic model for shafting system as well as the three-dimensional models for propeller blade and fan impeller. Such a flexible shafting system has very intricate vibrating characteristics and especially, axial natural frequencies of flexible components such as propeller blade and impeller of lift fan can be lower to the extent that causes a resonance in the range of operating revolution. The results for axial vibration analysis are presented and compared with the results of axial vibration test for lift fan conducted during Sea Trial.

Load distribution control system design for a semi-track air-cushion vehicle

This paper describes the design principle for a semi-track air-cushion vehicle working on soft terrain. A novel structure, i.e., a flexible joint mechanism is designed for the semi-track air-cushion vehicle suspension system. Focusing on optimizing the total power consumption of the vehicle, three main issues were studied in this paper. First, a theoretical model for minimizing the total power demand of the vehicle is developed. The effects of load distribution on total rolling resistance and total power requirement are calculated which are compared with the prototype experiment data. Second, the optimization procedure is presented. Third, a control scheme is proposed to minimize the power consumption by using a self-tuning PID fuzzy controller and the feasibility was examined by the simulations performed in Matlab/Simulink software environment.

공기부양선의 추진 및 부양축계 비틀림진동 해석 연구

A propulsion and lift shafting system in an air cushion vehicle is flexible multi-elements system which consists of two aeroderivative gas turbines with own bevel gears, four stage lift fan reduction gear, two stage propulsion reduction gear, air propellers and high capacity of lifting fans. In addition, the system includes the multi-branched shafting with multi-gas turbine engines and thin walled shaft with flexible coupling. Such a branched shafting system has very intricate vibrating characteristics and especially, the thin walled shaft with flexible couplings can lower the torsional natural frequencies of shafting system to the extent that causes a resonance in the range of operating revolution.<BR> In this study, to evaluate vibrational characteristics some analytical methods for the propulsion and lift shafting system are studied. The analysis, including natural frequencies and mode shapes, for five operation cases of the system is conducted using ANSYS code with a equivalent mass-elastic model.

Variation in the wave resistance of an amphibian air-cushion vehicle moving over a broken-ice field

The nonstationary rectilinear motion of an amphibian air-cushion vehicle (AACV) on a water surface covered with finely broken ice is considered for various modes of velocity variation. The influence of the water depth, flotation parameters, and mode of motion on the wave resistance of the vehicle is analyzed. Maneuvering methods for increasing or decreasing the wave resistance of AACVs are proposed.

DESIGN AND ANALYSIS ON APRON STRUCTURE OF AIR-CUSHION VEHICLES

The effects of aprons on an air-cushion vehicle are presented in brief and several different types of aprons used in air-cushion vehicles are compared based on the specialties of certain prototype vehicles. And the folding angle finger apron is chosen in this type of vehicle. The structure and geometry parameters of the apron are designed and analyzed in order to imp-ve the travelling performance of the vehicle, maneuverability, anti-avulsion and anti-turnover characteristics of apron structure. The distortion corresponding conditions of the apron structure are acquired according to the theorem of energy equivalence. The structure parameters of the apron are confirmed through the method of finding points by four lines, which can avoid imprecision of traditional experiential design methods and gets the good effect in the test.

Fundamental Study on Deformation Monitoring of Vibrating Seals in Air Cushion Vehicles by Using Fiber-Optic Sensors

We verified the applicability of a fiber-optic sensor to deformation monitoring of the seal equipped with an air cushion vehicle such as a surface effect ship (SES). The seal is a membrane structure made of an elastomeric material. It is difficult to measure deformation or vibration of the membrane structures by using a sensor which is fixed on it. In laboratory tests, we could measure strain-rate of the seal material subjected to cyclic loading by using the fiber-optic sensor adhered to it. Then, in monitoring tests of a small model of the seal with the sensors, frequency or amplitude of vibration was changed according to the velocity of water flow or the length of the bottom in water. In this paper, we described the results of these tests and showed the good applicability of the fiber-optic sensor to measure the response of membrane structures which have elastomeric properties.