Analysis of peak resistance and water stability of wheeled amphibious vehicles with initial trim angle

BACKGROUND: amphibious wheeled transport and technological complexes (AWTTC) are critically important for rescue and other special operations, but their speed on water is limited due to high wheel resistance and suboptimal hydrodynamics. Existing studies do not take into account the planing mode in a comprehensive manner. AIMS: the objective of this work is to develop a mathematical model of the movement of an amphibious vehicle on water in the planing mode, which takes into account not only hydrostatic forces, but also hydrodynamic ones. MATERIALS AND METHODS: equations for determining excess pressure on the hull surface are derived based on the Cauchy-Lagrange integral, a calculation scheme for the interaction of a flat-bottomed hull with the water surface is developed. Analytical expressions for the lifting hydrodynamic force, resistance force, and hydrodynamic moment are obtained. An analysis of the stability of motion is carried out taking into account the position of the center of gravity, the magnitude of the traction force of the watercraft propeller, and the trim angle. RESULTS: it was found that at Froude numbers Fr 3.0, hydrodynamic forces provide 95-97% of maintaining the AKTT afloat. The criteria for the stability of motion are obtained: with a negative arm of the propeller force, the stability depends on the magnitude of the thrust, with a positive arm, the critical speed of motion is determined. It was found that the thickness of the "reverse jet" is proportional to the angle of attack, the resistance force has a quadratic dependence on the speed, the arm of the hydrodynamic moment is linearly dependent on the trim angle. CONCLUSIONS: the developed mathematical model allows analyzing the motion of the AKTT in the planing mode taking into account key hydrodynamic factors. The obtained results create a theoretical basis for the design of high-speed amphibious vehicles and require further experimental validation.

The control surface is an effective apparatus for improving the performance of planing boats and is considered an important element in the design of planing boats. Trim-tabs are placed at the transom to give better trim angle in order to diminish the resistance. In this paper, algorithm genetic (GA) is applied to find the trim, resistance and dearrise angle using Savitsky’s formulas. The input data are all boat dimensions, including trim-tab data. The output results are trim angle, longitudinal center of gravity (lcg) and deadrise angle (β) and minimum resistance.

Design of multimodal transformable wheels for amphibious robotic vehicles

The attributes of a high-speed vessel depend on various factors, such as trim angle, speed, center of gravity, and deadrise angle. The ship's trim angle will affect the ship's drag performance. Attempts to control trim have been made by adding stern appendages and modifying the hull. This study aims to analyze the performance of deep-V planing-hull ship drag by modifying the ship's stern. The stern modification investigation was carried out by adding length to the stern based on angles of 100, 200, and 300. This investigation evaluates resistance, trim, and heave while ignoring changes in ship displacement. The prediction of resistance and ship movements was simulated using the Reynold Averaged Navier-Stokes (RANS) equations to solve the problem. Numerical simulation applied the Computational Fluid Dynamics (CFD) based on finite volume method with an overset of techniques. Validation studies ensured numerical simulations have good accuracy based on comparisons with experimental model tests conducted by previous researchers. The pressure distribution caused by the extended stern affected the ship's drag, further demonstrating a better trim control. The results of the stern modification simulation revealed that the resistance was reduced at Fr 0.58–0.87. Extended sterns with an angle of 30° indicated the best results, with a resistance reduction percentage of 26% at Fr 0.58. However, drag increased at Fr speeds > 1.45 as the ship's speed increased.

<div class="section abstract"><div class="htmlview paragraph">In response to the complex shore slope road conditions and the switching of water–land environments during the amphibious vehicle’s landing process, a landing drive force control strategy for amphibious vehicles is proposed. First, based on the shore slope gradient, buoyancy effect, and amphibious vehicle acceleration, the drive force of the front and rear wheels of the amphibious vehicle is pre-allocated. Then, referring to the road parameters of common road types, the road adhesion coefficient and optimal slip ratio of the current road surface where the amphibious vehicle is located are identified based on the principle of fuzzy control. Subsequently, with the slip ratio difference as the control target, the drive motor is controlled based on the sliding mode control algorithm to achieve tracking of the optimal slip ratio. A joint simulation is carried out using CarSim and Simulink, and the results are compared with those without control. The simulation results show that the drive force control strategy proposed in this paper can reduce the water-to-land time by 9.1 s and quickly reduce the wheel slip ratio to below 0.2, controlling it near the optimal slip ratio, thereby improving the vehicle’s power and stability.</div></div>

Three-wheeled motor vehicles have been around for close to a half a century now, but they have largely remained in the realm of recreational or concept vehicles. Due to increasing fuel prices and an emphasis on fuel efficient design, the automotive industry is exploring the three-wheeled option now more than ever as a mainstream daily-use vehicle. The trend is evident from the Automotive X-Prize which featured six teams with three-wheeled vehicle designs to meet the fuel efficiency target [1]. A three-wheeled vehicle design offers vast potential for improvement in overall fuel efficiency over their four wheeled counterparts, as it lends itself to a tear-drop shape which is highly aerodynamic and is also likely to be lighter and have lower rolling resistance. These factors have considerable impact on improving fuel efficiency, but such a design also presents challenges in terms of vehicle stability and can be susceptible to roll-over or spin out in certain scenarios. The primary factor that determines the stability of a three-wheeled vehicle is its center of gravity (CG). This paper uses a model-based approach to explore the CG position limits for stable operation of a front wheel drive three wheel vehicle and aims to give an empirical basis for deciding CG position limits for future three wheel vehicle design. ADAMS/Car is used to model the vehicle and the model is validated using test data from a commercially available three-wheeled vehicle. The performance of the model is then studied for various CG positions and the limits of safe operation are established for this particular model.

The paper proposes a method for determining a vehicle stopping distance based on a braking rate and a coefficient of using an adhesion force by an automated control system for regulating a braking force on the example of a multi-axle vehicle. The aim of the study is to calculate parameters of the braking efficiency of a multi-axle wheeled vehicle equipped with an automated braking force control system based on the adhesion between a tire and a supporting surface. A peculiarity of the considered method is the use of the calculated braking coefficient of the vehicle and the coefficient of use of adhesion forces during the operation of automated system for regulating the braking force. The presence of new mathematical relationships between the position of the coordinate of the vehicle’s gravity center, realized by the clutches of its wheels, and the braking coefficient of the vehicle makes it possible to simulate the change in the deceleration of a wheeled vehicle in various braking modes of its motion. The terms describing the interaction of an elastic tire with a supporting surface in the braking mode of a wheeled vehicle have been substantiated. Equations are written that permit to calculate: a position of the coordinate of gravity center of a multi-axle wheeled vehicle relative to its front and rear axles; a braking coefficient value of a multi-axle wheeled vehicle based on the coordinates of the position of its gravity center, clutches that are realized between its tires and a supporting surface; load distribution between the respective front and rear axles of the vehicle. To calculate the stopping distance of a wheeled vehicle, it is proposed to take a coefficient value of use of the adhesion force equal to 0.83, regardless of the change in weather and climatic conditions in which the vehicle is operated (a calculation error under an accepted assumption is not more than 5 %). In a graphical form, a design diagram of the coordinate position of a gravity center of a multi-axle wheeled vehicle is presented, which gives a general idea about the redistribution of masses between front and rear axles of the vehicle. Scientific publications on the change in the value of the realized adhesion between the tire and the supporting surface in the braking mode of the automobile wheel under various factors have been analyzed in the paper. The proposed concept for determining parameters of the braking efficiency of a multi-axle wheeled vehicle clarifies some provisions in the theory of vehicle motion, in particular, it allows to apply the calculated method for determining the deceleration of a vehicle in the problem of increasing vertical loads on the axles of a multi-axle wheeled vehicle in the braking mode. The given method for calculating coefficients of weight distribution between adjacent front or rear axles of a multi-axle wheeled vehicle increases an accuracy of determining the amount of deceleration of the vehicle by the calculation method.

In this paper, the road performance and mechanism of cement-phosphogypsum-red clay (CPRC) under dry and wet cycling were systematically investigated using 5% cement as curing agent, the mass ratio of phosphogypsum: red clay = 1:1, and 5% SCA-2 as water stabilizer. The road performance of dry and wet cycle mix was verified with the National Highway G210 Duyun Yangan to Yingshan Highway Reconstruction and Expansion Project as a test road to provide a scientific basis for the application of cement-phosphogypsum-red clay on roads. The results show that the cement-phosphogypsum-red clay unconfined compressive strength decreases with the increase of the number of wet and dry cycles, with a larger decay in the first three times and leveling off thereafter. The CBR value meets the requirements of roadbed fill on highway and Class I roads as stipulated in the Design Code for Highway Roadbeds (JTG D30-2015). SCA-2 water stabilizer reduces the strength of the mixture, but significantly improve the water stability performance of the mixture, the reason SCA-2 water stabilizer active ingredients and mixing particles of physicochemical reaction, the content of ettringite in the mixture is lower than the content of the mixture not mixed with water stabilizers, the generation of quartz, white mica, and kaolinite and other hydrophilic poor material increases, the surface of the cementitious material increases, the seepage channel is reduced, so the strength is reduced, and water stability performance is improved. The roadbed of the test road was smooth and dense, with no scouring, peeling or cracking. The settlement of the roadbed is less than the requirement of "Highway Roadbed Design Specification" (JTGD30-2015). Cement-phosphogypsum-red clay (cement 5%, phosphogypsum 47.5%, red clay 47.5%, SCA-2 water stabilizer 5%) can be used as filler for road bed on highway and primary road base.

In this paper, the road performance and mechanism of cement-phosphogypsum-red clay (CPRC) under dry and wet cycling were systematically investigated using 5% cement as curing agent, the mass ratio of phosphogypsum: red clay = 1:1, and 5% SCA-2 as water stabilizer. The road performance of dry and wet cycle mix was verified with the National Highway G210 Duyun Yangan to Yingshan Highway Reconstruction and Expansion Project as a test road to provide a scientific basis for the application of cement-phosphogypsum-red clay on roads. The results show that the cement-phosphogypsum-red clay unconfined compressive strength decreases with the increase of the number of wet and dry cycles, with a larger decay in the first three times and leveling off thereafter. The CBR value meets the requirements of roadbed fill on highway and Class I roads as stipulated in the Design Code for Highway Roadbeds (JTG D30-2015). SCA-2 water stabilizer reduces the strength of the mixture, but significantly improve the water stability performance of the mixture, the reason SCA-2 water stabilizer active ingredients and mixing particles of physicochemical reaction, the content of ettringite in the mixture is lower than the content of the mixture not mixed with water stabilizers, the generation of quartz, white mica, and kaolinite and other hydrophilic poor material increases, the surface of the cementitious material increases, the seepage channel is reduced, so the strength is reduced, and water stability performance is improved. The roadbed of the test road was smooth and dense, with no scouring, peeling or cracking. The settlement of the roadbed is less than the requirement of “Highway Roadbed Design Specification” (JTGD30-2015). Cement-phosphogypsum-red clay (cement 5%, phosphogypsum 47.5%, red clay 47.5%, SCA-2 water stabilizer 5%) can be used as filler for road bed on highway and primary road base.

In order to verify the characterization degree of water stability, research selects some clay content aggregate retrieved from road engineering field to produce rubber asphalt mixture and carry out the water stability test. Test results show that clay content in aggregate has a significant influence on the water stability of rubber asphalt mixture. When the content of clay in aggregate less than 1%, the influence on water stability is smaller; when the clay content exceeds 2%, the decay rate on water stability performance and long term properties obviously speed up, resulted in serious water damage.

One- and three-degree-of-freedom dynamic stability balances were used in supersonic and hypersonic wind tunnels to measure the trim angles of attack of a 10° cone with small asymmetries. The asymmetries, tested independently, were a flare section near the base of the model and a misalignment of the principal axes with respect to the geometric axes. The test hardware, techniques, and results are described. Numerical simulations are compared with the wind tunnel results and full-scale flight data. The comparisons show that the trim angles determined with these techniques permit accurate prediction of flight performance. asymmetry and an inertia asymmetry. The aerodynamic asymmetry was a small wedge (flare section) located at the aft end of the vehicle. The inertia asymmetry was generated by rotating two of the vehicle's principal axes with respect to the geometric axes. In both cases, the asymmetries were designed to provide a reference out-of-plane trim angle of 0.5° during the initial portion of the flight (Moo « 4.2). The asymmetries were combined with an offset center of gravity so that the induced trim angle would produce a roll torque. Success of these flights depended to a large degree on the accuracy with which the trim angle, induced by either type of asymmetry, could be predicted. During the planning phases of the flights, it was apparent that experimental determination of the trim angles, in a wind tunnel, would be advisable. The type of data desired, together with the small magnitude of the trim angles to be measured, required that new test hardware and procedures be developed. This paper presents the results of a study conducted to measure the trim angle of attack of a 10° cone with small asymmetries. Details of the experimental techniques, comparisons of experimental results with analytical and numerical predictions, and comparisons with flight data are presented in the follow- ing sections.

Porpoising instability may occur in high-speed amphibious vehicles with certain hull shapes and structural properties, resulting in speed limitations and severe safety risks. This study analysed the causes and inhibition of porpoising instability by theoretical and numerical methods. The pitch-heave-coupled model of amphibious vehicles was established based on the linear hydrodynamics assumption. After obtaining the hydrodynamic coefficients of forced pitching and heave, the Routh–Hurwitz criterion and eigenvalue extraction method were then employed to assess the stability of the vehicle’s longitudinal motion. The result of the linear stability analysis was compared with numerical simulation and experiments, showing good agreement. Research manifested that trim angle is a crucial factor affecting porpoising instability. Once the instability is mitigated, the resistance will also be decreased. This indicated the great significance of restraining porpoising instability for the comprehensive behaviour of high-speed amphibious vehicles.

Analysing correlations among resistance at Froude number F∇ (= V/√∇1/3g) =3.5, trim angles at F∇=2.5 through 3.5, by using model test data in still water of the high speed craft, the clear correlation was found to exist between resistance at F∇=3.5 and trim angle at F∇=2.5.Therefore, the sequential unconstrained minimization technique was first applied to get the smallest total resistance hull form for each 30 minutes interval of trim angle change, and then followed the discussion concerning deviations arisen and resistance performance due to obtained hull form parameters. Using diagrams related to the total resistance at F∇=3.5 and the trim angle at F∇=2.5, we clarified finally the influence of the unit trim angle on the total resistance coefficient within high speed range.

In order to analysis controllability and stability of wheeled vehicle, virtual model of 8×8 wheeled vehicle was constructed by ADAMS/Car. Doing snakelike test for virtual model by use of appraise method for controllability and stability of vehicle, according to the appraise and scoring for average steering wheel angle and average yaw velocity peak value at basic speed at last, the analysis result shows the better controllability and stability of the model, which provide the basis for further study of the entire vehicle dynamics.

Currently, great attention is paid to the development issue of the shelf’s fuel and energy resources foremost in the oil-gas fields of the Caspian Sea. The problem solution requires the studying of great majority of scientific-technical issues. One of the significant problems is the lead-out of steel jacket from the offshore platform as a major element of oil-gas field hydro-technical facilities meant for the operation in the deep water. The calculations for the execution of operations with steel jacket of deep stationary platform from the block with the detailed chara- cteristics by the mass and gravity center coordinates alongside line data have been carried out with “SACS” and “STAAD.PRO” software programs. The steel jacket is pushed astern with the push-pull equipment on the barge. Due to the shift of gravity centre the jacket changes the trim in the stern. Through the elevation of trim angle brought in alignment with the friction ration between the jacket and barge, the jacket slides further itself. Herewith, the trim increases until the gravity centre of steel jacket on the barge is not in alignment with rotation centre of the large rocker arms. The studies helped to fix the position of the jacket’s gravity centre from the aft perpendicular, the trim moment, the trim of the barge, the draft with the bow and stern and the trim angle as well.