Stable Roll Research Articles

Modeling and Methods for Improving Anti-Rolling Abilities of Autonomous Surface Manipulator Systems

An autonomous surface manipulator system (ASMS) is a novel intelligent system consisting of a robotic manipulator and an unmanned surface vehicle (USV). Due to the waves and the motions of the manipulators, ASMSs experience rolling while performing tasks, reducing their stability and working accuracy. Hence, two methods are proposed for improving the anti-rolling abilities of ASMSs based on their mathematical models. The first method is to solve the inverse kinematics issues of the manipulator with the objective of minimizing the moment between the manipulator and its base, and to design angle-time curves for each joint using seven-order polynomials. Experiment results demonstrate that the motion optimization of manipulators can reduce the maximum and stable roll angles of the USV by over 40%. The second method involves assembling a moving-mass system into the ASMS and controlling the motion of the moving mass using a dual-loop PID controller. The moving-mass system can significantly reduce the roll angle of USV caused by waves and the operations of manipulators, as validated by simulation on a proposed accurate dynamic model. The research work can greatly enhance the operation stability of ASMSs.

Attitude stability control for 6WID unmanned ground vehicle during steering: A collaborative controller considering minimizing tire slip energy loss

The instability of vehicle attitude and wheel slippage during turning on complex roads are key factors affecting the operational efficiency and accuracy of a variable wheelbase six-wheel independent drive unmanned ground vehicle (6WID UGV), posing a serious threat to driving safety. This article proposes a hierarchical coordinated controller to improve the attitude stability of a 6WID UGV equipped with interconnected active hydro pneumatic suspension (IAHPS) and reduce tire slip energy loss. Firstly, an integral sliding mode controller with adaptive high-order coupling factor (AHOCF-ISMC) is designed to determine the active anti roll torque required for stable roll attitude. An adaptive high-order coupling factor is introduced in the controller framework to couple physical components with different properties, avoiding overshoot and oscillation caused by integral saturation of the controller. Secondly, based on satisfying the stability of the roll attitude, the lateral stability and longitudinal traction characteristics of the vehicle are constrained and controlled. An optimization function was established to minimize tire slip energy loss within the feasible range of wheel torque determined by lateral and longitudinal control objectives. Thirdly, the particle swarm optimization algorithm was improved (IPSO) by designing adaptive weighting factors and learning factors, and is used to optimize the wheel torque distribution scheme under composite constraint conditions. Finally, the effectiveness of the coordinated controller was tested and validated in different scenarios. The results show that the designed controller has good control performance and robustness without the need to establish an accurate mathematical model, and performs well in terms of economic benefits and application prospects.

Flow reversal and multiple states in turbulent Rayleigh–Bénard convection with partially isothermal plates

This paper examines turbulent Rayleigh–Bénard convection in a two-dimensional square cavity with partially isothermal conducting plates on the horizontal walls. The study reveals that controlling the relative locations of the partially isothermal plates can accelerate or completely suppress the reversals of large-scale circulation. The heat transfer efficiency, which is characterised by the time-averaged Nusselt number, is generally higher than that of the traditional Rayleigh–Bénard convection, and can be further enhanced when the reversal is fully suppressed. The reversal in our cases is mainly caused by the competition between the two alternately growing ‘corner’ vortices, fed by the detaching plumes from the hot/cold plates. This differs from those reported in traditional Rayleigh–Bénard convection. Fourier mode decomposition of the kinetic energy, reflecting the diverse contributors, in the reversing cases further emphasises the distinction between the current system and traditional Rayleigh–Bénard convection. In addition, multiple states were observed where the conducting plates were positioned at specific relative locations and had different initial conditions. It has been observed that the difference in Nusselt numbers between the anticlockwise and clockwise states increases linearly with the distance between the upper cold and lower hot plates. Moreover, the analysis of the buoyancy moment and the stability of the primary roll structure suggests that the higher heat transfer efficiency between the two states is strongly linked to a more stable primary roll structure. This study presents a new approach for controlling flow reversal and improving heat transfer efficiency by modifying the non-global conducting boundary and initial conditions.

Calculation of Lateral Stability of Tank Trucks and its Relationship with Filling Rate

To investigate a theoretical algorithm model of the lateral stability of tank trucks and its relationship with the liquid filling rate, the shifting of the liquid centroid during non-full loading is considered. The deformation of the suspension and tires under load is assumed to exhibit a linear relationship. Using the principle of moment balance, a calculation model for the maximum stable roll angle and rollover critical acceleration of tank trucks based on the “liquid–tank–vehicle” tri-coupling is established, and the relationship between the maximum stable roll angle and rollover critical acceleration of tank trucks is analyzed and compared. Based on the result and a specific tank truck model, the effects of the liquid filling rate on the maximum stable roll angle, rollover critical acceleration, and tank tilt angle of tank trucks are investigated using numerical analysis methods. A comparison with the lateral stability of ordinary trucks loaded with solid goods is performed to further examine the effect of the liquid filling rate on the lateral stability of tank trucks. The results show that the maximum stable roll angle and rollover critical acceleration are consistent indicators for evaluating the lateral stability of tank trucks; the lateral stability of tank trucks decreases owing to the shift in the liquid centroid inside the tank; as the liquid filling rate increases, the lateral stability of the tank trucks deteriorates slightly.

Accidentally light scalars from large representations

In models with spontaneous symmetry breaking by scalar fields in large group representations, we observe that some of the scalar masses can be loop-suppressed with respect to the naive expectation from symmetry selection rules. We present minimal models — the SU(2) five-plet and SU(3) ten-plet — with such accidentally light scalars, featuring compact tree-level flat directions lifted by radiative corrections. We sketch some potential applications, from stable relics and slow roll in cosmology, to hierarchy and fine-tuning problems in particle physics.

Modeling and stability analysis for autonomous surface manipulator systems

An Autonomous Surface Manipulator System (ASMS) is a versatile system with a robotic manipulator installed onto an Unmanned Surface Vehicle (USV), which can bring important technological innovations and efficiency improvements to various ocean applications. To develop a high-performance ASMS, an accurate model of the ASMS is required. However, existing models have limitations, such as neglecting the dynamic coupling between manipulators and USVs and not being suitable for stability analysis of ASMS. Hence, this paper proposed a modeling method for ASMS considering the dynamic coupling between the manipulator and the USV and performed stability analysis of the ASMS with the proposed model. Firstly, a six-degree-of-freedom ASMS model is introduced using the Newton-Euler equations. Then, an ASMS prototype is developed to validate the model, with its parameters identified through experiments. Subsequently, the motions of the USV are measured and compared with the calculated values under various motions of the manipulator. The accuracy of the proposed ASMS model is validated by the calculated errors of maximum roll angles and stable roll angles of the USV, which are less than 2deg and 1.1deg, respectively. Finally, a stability indicator is proposed, and the stability of the ASMS is analyzed.

Stability of Periodic Orbits and Bifurcation Analysis of Ship Roll Oscillations in Regular Sea Waves

Response, stability, and bifurcation of roll oscillations of a biased ship under regular sea waves are investigated. The primary and subharmonic response branches are traced in the frequency domain employing the Incremental Harmonic Balance (IHB) method with a pseudo-arc-length continuation approach. The stability of periodic responses and bifurcation points are determined by monitoring the eigenvalues of the Floquet transition matrix. The primary and higher-order subharmonic responses experience a cascade of period-doubling bifurcations, eventually culminating in chaotic responses detected by numerical integration (NI) of the equation of motion. Bifurcation diagrams are obtained through the period-doubling route to chaos. Solutions are aided with phase portrait, Poincaré map, time history and Fourier spectrum for better clarity as and when required. Finally, the same ship model is investigated under variable excitation moments that may result from different wave heights in regular seas. The biased ship roll model exhibits primary and subharmonic responses, jump phenomena, coexistence of multiple responses, and chaotically modulated motion. The stable, periodic, and steady-state roll responses obtained by the IHB method are validated by the NI method. Results obtained by both methods are found to agree very well.

μ(J)-Rheology-based depth-averaged dynamic model for roll waves in granular–fluid avalanches

A depth-averaged two-dimensional mathematical model of granular-fluid avalanches is proposed based on the μ(J) rheology. In the model, a depth-averaged deviatoric viscous stress of granular-fluid mixture is formulated and the corresponding depth-integration term is linearly proportional to the flow depth, which is different from the 1.5th-power law for dry granular avalanches. A basal resistance on the granular-fluid mixture, composed of a Coulomb friction term and a viscous shear term, is adopted in the model. Based on the model, a critical Froude number of 1/2 is obtained for the linear instability of steady-uniform granular-fluid mixture flows. The model is capable of capturing the cutoff frequency for the spatial growth rate of perturbation in the mixture flows. The proposed model is applied to simulate the evolution of imposed perturbations in steady granular-fluid avalanches on an inclined chute. The intensification of imposed perturbations and the generation of final stable roll waves are captured. A parameter sensitivity analysis is conducted to investigate the effects of the depth-averaged in-plane deviatoric viscous stress and the basal resistance on the final stable roll waves. Further, a preliminary analytical solution for the crest/trough heights of the stable roll waves is proposed to verify the numerical findings.

Numerical Design Studies on the Roll Stability of a Multi-Delta-Wing Configuration

The current investigations look at the vortical flow physics and aerodynamic performance of a generic sharp leading-edge multi-delta-wing configuration. This work is part of the DLR project Diabolo looking at technologies and design requirements for next-generation fighter aircraft. The core of the investigation is a common planform geometry to demonstrate the design capability needed. Based on the initial planform, several design tasks in different domains have to be conducted. The present paper is dealing with the aerodynamic task to evaluate the effect of vortex interaction over the configuration progressing from the forebody, strakes, and main wing at asymmetric on flow conditions. The focus is on the roll stability at medium to high angle of attack. The aim is to find a planform and control surface setup which effects the vortex interaction on the main wing in a way to provide a stable aerodynamic roll without taking vertical and horizontal tail planes into consideration at this stage.

Analysis of coiling stable roll of hot-dip galvanized strip

The coiling stable roll of hot-dip galvanized is a defect formed in the galvanizing process. The zinc slags and floating foreign matters in the zinc pot will directly or indirectly adhere to the roll surface of the stabilizer roll with the flow of zinc liquid. When the strip steel contacts the stabilizer roll, the zinc slag will extrude and deform the iron base plate and form pits. In this paper. The causes of the defects were analyzed. There were two methods to eliminate the coiling stable roll, that is, to reduce the generation and accumulation of zinc slags in the zinc pot. The main measures are first to control the temperature of the strip entering the zinc can plate and the temperature of the molten zinc, and then control the amount of residual bottom residue before the zinc pot goes online. Another is to ensure the cleanliness of the steel strip before it enters the molten zinc. Based on this, the main measures implemented are: improving the cleaning ability of the cleaning section and improving the reducing ability during annealing to inhibit the formation and accumulation of zinc powder in the furnace head area.

Numerical study of free convection in a thin layer between coaxial horizontal cylinders

We consider free convection in 2D and 3D horizontal cylindrical layers with the inner hot and outer cold boundary at Ra (Rayleigh number) in range (4∙103 ÷ 4∙105) and the ratio δ ≈ 1:20 of the layer width to inner radius. Prandtl number was 0,71, fluid properties were taken for air at 293 K.It was shown that the flow in a 2D cylindrical layer can be divided into three regions. Stable symmetric convective rolls are formed in the layer’s upper part; regions with the transient flow appear at the lateral sides; transitional regions between the upper and the lateral regions have convective rolls of an unusual asymmetric shape.The flow in a 3D cylindrical layer in the upper part is organized into a spatially stable convective roll pattern. With increase of the Rayleigh number (Ra), roll pattern becomes suppressed by a transient plume pattern.The global Nu (the Nusselt number) is proportional to 0,0019∙Ra0,567 for the 2D case and to 0,22∙Ra0,192 for the 3D case. The 2D problem provides a reasonable estimation of the Nusselt number for Rayleigh number up to 4∙104 and overestimates Nu for higher Rayleigh number, which agrees with Lyapunov exponent values.

Privacy-preserving state estimation with unreliable channels

A co-design problem of privacy-preserving encoding and filtering is concerned in this paper. A remote legal user estimates states of a dynamic system by the received innovation messages. However, the communication channel is neither reliable nor secure. The messages may be missing during the transmission and have a risk of being intercepted by an eavesdropper. Therefore, in this work, an encoding scheme together with an MMSE estimation algorithm are designed for preserving information privacy and meanwhile guaranteeing estimation performance. We introduce a novel encoding approach using a weighted innovation with a public key to achieve privacy security as well as low computational expense. A filtering algorithm is designed under such an encoding mechanism. And the performance of the filter and the encoding method is analyzed. The feasibility of the encoding approach and the filtering algorithm is illustrated through numerical examples of an unstable system and a stable ballistic roll rate estimation system.

Experimental validation and numerical simulation of flexible and microscale roll gap control technology

This paper proposes a new flexible and microscale roll gap control technology to obtain a stronger strip flatness control ability. According to the principle of microscale roll gap control technology, an electromagnetic control rolling mill with the function of roll profile control and large diameter ratio rolling is designed and built. To analyze the flatness control ability, a comprehensive finite element model (FEM) is established, and an indentation experiment and a rolling experiment are carried out. The simulation results show that under different rolling forces and tensions, the average quadratic crown control ability is more than 40 μm, and the average quartic crown control ability is more than − 3 μm. The control ability increment of the quadratic crown is greater than that of the quartic crown. In the indentation experiment, a stable roll profile can be achieved by PID control after reaching the target roll profile. Increasing the regulation amount can change the strip crown from positive to negative. Even under high rolling force conditions, microscale roll gap control technology can also realize a strip crown adjustment of 19.5 to 0.5 μm. Moreover, this technology can adjust the strip shape from edge waves to non-waves and middle waves in the rolling experiment. In this paper, the feasibility of using this technology to adjust the roll gap shape has been verified, and we demonstrate that the roll gap control goal of uniform transverse size distribution can be achieved.

Correction-Efficiency-Coefficient-Based Trajectory Optimization for Two-Dimensional Trajectory Correction Projectile

Based on the lift-to-drag ratio of a two-dimensional trajectory correction projectile, in this paper, a novel correction efficiency coefficient model has been proposed for the trajectory optimization of a two-dimensional trajectory correction projectile, and research on the influence a correction efficiency coefficient has on the flight parameters of correction trajectory is carried out. A series of results are obtained through theoretical analysis and simulation calculations, indicating that, the smaller the value of the correction efficiency coefficient is, the stronger the correction ability of the projectile reserves. The trajectory and canard geometry of the correction section of the two-dimensional trajectory correction projectile are optimized by the Gauss pseudo-spectral method and correction efficiency coefficient, and, after taking the correction efficiency coefficient into account, the projectile can accurately hit the target and effectively eliminate the swing phenomenon of the projectile’s lateral trajectory. Meanwhile, a stable roll control command is obtained. When the diameter aspect ratio of the canard is 0.4, both the flight state quantity of the optimized projectile and the roll control command are more stable, and, when the canard shape is trapezoidal, the correction efficiency coefficient is smaller, the result of trajectory optimization is more stable, and the stability of the output roll control command is better. The research results of this paper can provide certain references for both the designs of the two-dimensional trajectory correction projectile’s trajectory and the canard geometry.

Energy-conserving model of hexagonal pattern in Rayleigh-Bénard convection

We have constructed an energy-conserving 16 mode dynamical system to model hexagonal pattern in Rayleigh-Bénard convection of Boussinesq fluids with symmetric stress-free thermally conducting boundaries. The model shows stable roll pattern at the onset of convection. Hexagon is found to appear in the system via sausage and (or) stationary rhombus patterns. Both up and down hexagons arise periodically or chaotically with roll, sausage and rhombus patterns. Hexagonal pattern exists for all values of the Prandtl number, explored here. However, the pattern is more prominent for small Pr and , where k denotes the wave number. The plot of Nusselt number matches with previous theoretical result. In dissipationless limit, the total energy and the unavailable energy are constants though the kinetic energy, the potential energy and the available energy vary with time. The derived model does not diverge for large values of Rayleigh number Ra.

Human Vehicle Dynamics Coupling of Miniature Electric Vehicle Roll Stability: Effects of Driver Weight, Wheel Base and Track Width

As a continuation of the previous research, influences of human vehicle dynamics coupling (HVDC) on miniature electric vehicle (MEV) roll stability are studied by varying driver weight, wheel base and track width. A multi-body dynamics model is developed for the human-vehicle system by ADAMS/Car software considering driver’s dynamics and is validated theoretically. Simulation results show that the MEV roll stability is decreased by the HVDC; the influences become greater with an increase in the proportion of the driver weight to curb weight of the MEV in both time and frequency domain; with the decrease of wheel base, the differences caused by the HVDC exhibit an increasing trend in the maximum value and overshoot; and the differences in the steady stable roll angle and phase lag at 0.6 Hz indicate an increasing tendency with the decrease of track width.

Design of stable controller attachable Anti Roll System (ARS) for vehicles

The most common problem which will be faced in hilly areas or in inclined roads is rolling back of vehicle when it has to be start up and move forward. There are numbers of accident reports happens in hilly regions caused due to rolling back of vehicle. Mostly drivers from the plane areas have to face this type of problem while driving in hilly areas. So we have designed a system which will avoid the rolling back of a vehicle and it will not stop the vehicle from accelerating forward. This function can be achieved by using the ratchet & pawl mechanism. In costly SUVs & automatic cars there is a feature available called “HILL HOLD ASSIST” to overcome this problem but in which it will require number of sensors, it can hold the vehicle only for 2to 3 seconds then after it will start rolling back and again it have to be activated and all the breaking system have to be modified and manufactured from the factory itself increasing its price and so it is available only in expensive cars. But our designed system is fully mechanical without any involvement of any sensors making it simple, cheap and can be attached additionally in any normal vehicles having disc brake system and there is no time limit in our designed system once it is activated it will remain activated unless the driver will not deactivate it. This system will allow the freedom to the driver while driving in inclined road; once the system is activated there will be no rolling back of vehicle and no need of applying breaks while starting it.

From zonal flow to convection rolls in Rayleigh–Bénard convection with free-slip plates

Abstract

Marangoni instability in the iodate–arsenous acid reaction front

Horizontally propagating chemical fronts leading to the formation of a single stable convection roll are investigated in the iodate-arsenous acid reaction with arsenous acid stoichiometrically limiting, leaving the surface active iodine present in the product mixture. In sufficiently thin solution layers with open upper surface, the contribution of Marangoni instability is significantly enhanced. Acting in the same direction as buoyancy driven instability, it distorts the entire tilted reaction front that becomes 50% more elongated. The corresponding three-dimensional calculations based on the empirical rate-law of the reaction corroborate the experimental findings.

Aligned natural inflation in string theory

The authors discuss type IIB string theory realizations of Kim-Nilles-Peloso (KNP) multiple axion inflation, which provides a super-Planckian effective axion decay constant, necessary for UV stable realistic slow roll inflation.