Rolling Motion Research Articles

Remarkable lubricity of CNTs microspheres as additives in oil lubricant for ceramic components

Severe wear was often caused by adhesive wear and tribo-chemical reaction for ceramic components. In view of this situation, potentials of carbon nanotubes (CNTs) used as oil additives were explored for lubrication of ceramic/steel tribo-components. Microscopic morphology and dispersion stability of the prepared CNTs were characterized. CNTs microspheres were formed and this might because of their aggregation that also lead to the weak dispersion stability. Additionally, nano-fluids containing various concentration of CNTs microspheres were prepared for exploring the optimum concentration, where their lubricating behavior for ceramic/steel tribo-components was investigated to determine the relation between CNTs microspheres and tribological properties. The results indicated that the optimum concentration was 0.2 wt%, where 53.1 % of friction reduction and 50.7 % of wear resistance were achieved at high contact stress of 1.35 GPa. The superior lubricity of CNTs microspheres might be attributed to their rolling movement and formation of protective film.

Study on the influence of car-body flexibility on passengers’ ride comfort

A 3D rigid-flexible human-seat-vehicle-track coupling model is proposed to analyze high-speed train ride comfort. The seated human model is built based on the multi-body dynamic method. The human multi-axis excitation measurement data determines the model parameters. The detailed FE (finite element) car body model is built, and the model is calibrated by laboratory modal tests. The dynamic behavior of the high-speed train, running on both straight and curved tracks, is analyzed by using the rigid-flexible human-seat-vehicle-track coupling model. Then, the effect of the seat support parameters on the ride comfort of the high-speed train is analyzed, when the train travels on curved tracks. The results show that using the rigid car body model can overestimate the ride comfort of the high-speed train. The lateral and rolling motion of the car body, induced by curves can worsen the lateral dynamic performance of the passenger seats. At the different seat positions and for the different configurations of seats (three-abreast and two-abreast), selecting proper stiffness of the seat-floor and seat-sidewall supports can achieve comfort for the passengers.

Dynamics modelling and vibration characteristics of urban rail vehicle axle-box bearings with the cage crack

The cage crack changes the structural stiffness on different components, and therefore affects its relative contact forces. Furthermore, the crack may cause the fault characteristics on the urban rail vehicle axle-box bearing. Despite all this, there is still a lack of discussion and summary on the dynamics modelling and vibration characteristics analysis of axle-box bearings with the cage crack. For filling this gap, two cage crack models are proposed, which are respectively constructed when the crack generates in the cage bridge or arm. Then, these models are coupled to the axle-box bearing model in a vehicle-track coupling model. Thereinto, the friction force and the motion of rollers are considered, and the cage is decentralized into several segments for facilitating the study of the force between adjacent cage segments. At last, the dynamic characteristics of axle-box bearings with the cage crack are investigated, and the changes in contact forces due to the cage crack are also analyzed. This study can provide valuable information for axle-box bearing condition tracking and monitoring.

Polymorphism and Light-Driven Forward Movement of TPE Derivative Micro-Crystal due to ArH-pi Interactions Difference.

Aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) are two classes of opposite luminescence phenomena. It is almost impossible to show both AIE and ACQ effect simultaneously by the same molecule. However, here we report that a simple TPE derivative TAP-TPE grows into both AIE crystals and ACQ ones. It is found that equatorial, contact distance-longer and weak ArH-π interactions exist in AIE crystals while vertical, contact distance-shorter and strong ArH-π interactions appear in ACQ crystals. Theoretical calculation of electron density on the interaction atoms unveils that ACQ crystals have much larger change in electron density than AIE ones, suggesting that the intermolecular electron transfer aroused by the strong ArH-π hydrogen bonds leads to ACQ phenomenon. This result provides a new insight into the emission mechanism in aggregation state. Interestingly, due to the ArH-pi interactions difference, only one of five kinds of crystals shows rapid photochromism, and can act as multimode anti-counterfeiting materials. Very exceptionally, for the first time we find that the photochromic micrometric rod-like crystal even makes forward rolling movement as it repeatedly bends and straightens by responding to on and off of the ultraviolet light irradiation, displaying potential for photo-actuator and light-driven micro-vehicle.

Topological Optimization of Vehicle ISD Suspension under Steering Braking Condition

Anti-roll and anti-pitch are important directions in the comprehensive research of automobiles. In order to improve the anti-roll and anti-pitch performance of the vehicle, an inerter was applied to the vehicle suspension system, and a 14 DOF vehicle nonlinear dynamics model was established. The influence of the change in inertance in the eight kinds of improved ISD (Inerter-Spring-Damper) suspension structures on the RMS (root mean square) value of performance indexes of roll, vertical, and pitch motion of the vehicle was studied. Based on this, the vehicle’s ISD structure with better performance was selected, and the NSGA-Ⅱ algorithm was adopted to optimize the selected structural parameters. The simulation results showed that the four kinds of suspension hadbetter comprehensive performance, and their structureswere, respectively, excluding the supporting spring in parallel, (1) an inerter in series with a spring and a damper in parallel, (2) a damper in series with a spring and an inerter in parallel, (3) an inerter and a damper in series, and (4) the damper in parallel with a spring and an inerter in series. The ISD suspension structure had better comprehensive performance under step steering braking, which was obviously better than the passive suspension, and effectively improved the vehicle ride comfort, anti-roll and anti-pitch performance. Under the hook steering braking, the lateral load transfer rate was used to evaluate the vehicle’s anti-rollover ability. The results showed that the ride comfort and anti-rollover ability of ISD suspension were better than those of passive suspension. Under the condition of taking into account the anti-pitching ability, the suspension consists of a supporting spring in parallel with an inerter, and a damper in series was better.

Experimental and numerical study of the hydrodynamics of a flapping fin at zero speed

The flapping fins can be used as effective actuators of roll stabilizers at zero speed. They provide anti-roll torques to reduce the roll motion of ships in waves. The effects of roll amplitude, flapping frequency and aspect ratio on the hydrodynamic forces and moments at zero speed have been studied through experiments and numerical simulations. It is found that the forces and moments can be described using the added mass forces and damping forces respectively. Empirical formulas to calculate the forces and moments have been derived. The flapping frequency has no significant effects on the force coefficients and moment coefficients. The drag coefficients can be described by an exponential function of KC number, the added mass coefficients are the function of roll amplitude and aspect ratio due to the 3D flow separation.

Control and evaluation of a humanoid robot with rolling contact joints on its lower body.

In this paper, we introduce a new teen-sized humanoid platform dubbed DRACO 3, custom-built by Apptronik and altered for practical use by the Human Centered Robotics Laboratory at The University of Texas at Austin. The form factor of DRACO 3 is such that it can operate safely in human environments while reaching objects at human heights. To approximate the range of motion of humans, this robot features proximal actuation and mechanical artifacts to provide a high range of hip, knee, and ankle motions. In particular, rolling contact mechanisms on the lower body are incorporated using a proximal actuation principle to provide an extensive vertical pose workspace. To enable DRACO 3 to perform dexterous tasks while dealing with these complex transmissions, we introduce a novel whole-body controller (WBC) incorporating internal constraints to model the rolling motion behavior. In addition, details of our WBC for DRACO 3 are presented with an emphasis on practical points for hardware implementation. We perform a design analysis of DRACO 3, as well as empirical evaluations under the lens of the Centroidal Inertia Isotropy (CII) design metric. Lastly, we experimentally validate our design and controller by testing center of mass (CoM) balancing, one-leg balancing, and stepping-in-place behaviors.

An active suspension system for enhancing running safety of high-speed trains under strong crosswind

The running safety of trains subjected to strong crosswinds has become a major concern for the high-speed railways passing through complicated mountain areas. This paper reports an active secondary suspension system to improve the operation stability and running safety of high-speed trains under strong crosswind. The goal of the active suspension system is to regulate the lateral, yaw, and roll motion attitudes of high-speed train carbody, in which a controller is designed by combining with a disturbance observer and the sliding mode control method. To further verify the proposed active suspension strategy, a crosswind-vehicle-track coupled dynamics model is established, where the unsteady aerodynamic loads and random track irregularity excitations are considered. The results show that the proposed active suspension system has the efficient potential to regulate the carbody motion attitudes and enhance the anti-rolling performance of high-speed trains. In comparison to a quasi-static control strategy of active suspension, the use of the proposed active suspension system has led to a significant reduction in both wheel-load reduction ratios and derailment risks of high-speed trains.

Normal variation in pelvic roll motion pattern during straight-line trot in hand in warmblood horses

In horses, hip hike asymmetry, i.e. left–right difference in hip upwards movement during hind limb protraction in trot, is a crucial lameness sign. Vertical hip movements are complex, influenced by both pelvic roll and pelvic vertical motion. Veterinarians find it challenging to identify low-grade lameness, and knowledge of normal variation is a prerequisite for discerning abnormalities. This study, which included 100 clinically sound Warmblood horses, aimed to describe normal variation in pelvic roll stride patterns. Data were collected during straight-line trot in hand using optical motion capture. Stride-segmented pelvic roll data, normalised with respect to time (0–100% of the stride) and amplitude (± 0.5 of horse average stride range of motion), were modelled as a linear combination of sine and cosine curves. A sine curve with one period per stride and a cosine curve with three periods per stride explained the largest proportions of roll motion: model estimate 0.335 (p < 0.01) and 0.138 (p < 0.01), respectively. Using finite mixture models, the horses could be separated into three groups sharing common pelvic roll characteristics. In conclusion, pelvic roll motion in trot follows a similar basic pattern in most horses, yet there is significant individual variation in the relative prominence of the most characteristic features.

Strong fixed-time dynamic inverse adaptive LQR integrated control strategy for dynamic positioning of ship

To ensure compositive capacities for dynamic positioning ship, a dynamic inverse adaptive linear quadratic regulator (DI-ALQR) control strategy is proposed for dynamic positioning ship based on strong fixed-time prescribed performance function (SFPPF) and cascaded fixed-time extended state observer (CFESO). Firstly, a high-fidelity four degree of freedom ship motion model including roll motion is constructed, and an inverse system of the ship is proposed to realize decoupling of variables and pseudo linearization of control systems. Next, the SFPPF is employed to ensure prescribed performance with predefined convergence. The DI-ALQR control strategy is presented to achieve integrated control of position, roll and heading of ship considering the balance between energy consumption and control accuracy. Simulation results and analysis prove that the proposed control strategy makes the position, roll and heading of ship reach in predefined-time and maintain the desired values, which ensures prescribed performance.

Muscle-inspired soft robots based on bilateral dielectric elastomer actuators

Muscle groups perform their functions in the human body via bilateral muscle actuation, which brings bionic inspiration to artificial robot design. Building soft robotic systems with artificial muscles and multiple control dimensions could be an effective means to develop highly controllable soft robots. Here, we report a bilateral actuator with a bilateral deformation function similar to that of a muscle group that can be used for soft robots. To construct this bilateral actuator, a low-cost VHB 4910 dielectric elastomer was selected as the artificial muscle, and polymer films manufactured with specific shapes served as the actuator frame. By end-to-end connecting these bilateral actuators, a gear-shaped 3D soft robot with diverse motion capabilities could be developed, benefiting from adjustable actuation combinations. Lying on the ground with all feet on the ground, a crawling soft robot with dexterous movement along multiple directions was realized. Moreover, the directional steering was instantaneous and efficient. With two feet standing on the ground, it also acted as a rolling soft robot that can achieve bidirectional rolling motion and climbing motion on a 2° slope. Finally, inspired by the orbicularis oris muscle in the mouth, a mouthlike soft robot that could bite and grab objects 5.3 times of its body weight was demonstrated. The bidirectional function of a single actuator and the various combination modes among multiple actuators together allow the soft robots to exhibit diverse functionalities and flexibility, which provides a very valuable reference for the design of highly controllable soft robots.

Strength Analysis of an Open Car Body with Honeycomb Elements during Ro-Ro Transportation

This article presents the determination of the bearing structure loads of an open car during ro-ro transportation. A special solution for an open car is the application of elastic, viscous honeycomb panels in the frame. This engineering solution can decrease the load of the bearing structure of an open car during interactions with multiple-use lashing devices. This article presents the mathematic modelling of the dynamic load of an open car during ro-ro transportation. This calculation is based on the most popular load diagrams for the bearing structure of an open car applied for sea transportation, namely the rolling motion and the turning motion of a train ferry approaching a dock. It was found that the application of honeycomb panels can decrease the dynamic load of a rail car in comparison to a standard structure by about 25%. The results of the strength calculation of the bearing structure of an open car demonstrated that the maximum equivalent stresses do not exceed the allowable values and are 30% lower than the stresses that emerging in the standard structure. The conducted research can be used by engineers who are concerned about safe and environmentally friendly transportation via train ferries and more efficient ro-ro transportation.

Analysis of Convergence Behavior for the Overset Mesh Based Numerical Wave Tank in openfoam

Abstract This paper presents a solution verification and validation study for an overset mesh based numerical wave tank in openfoam, which considers the coupling between a free-surface hydrodynamic flow model, a rigid body motion model, and an overset mesh. The coupling between the rigid body motion solver and the free-surface flow solver was achieved in a segregated manner. Free decay of roll motion of a barge was modeled using the numerical wave tank, and the damping coefficient was selected as the target quantity for solution verification. The least-square based solution verification procedure was adopted, where one of the four types of error estimators was fit to the data in the least-square sense. Both structured and unstructured mesh were tested, and their effects on the convergence order, numerical uncertainty, and error were carefully investigated. From the numerical tests, it is found that the numerical wave tank exhibits a very good convergence property for the floating body problems with structured mesh, i.e., nearly second order in space and first order in time. However, when switching the body-fitted mesh to unstructured mesh, the grid convergence is reduced to first order. Unstructured mesh does not significantly affect the convergence order in time domain, but results in a larger uncertainty due to data scattering.

Validation of a novel bicycle simulator with realistic lateral and roll motion

Bicycle simulators have been the subject of considerable research, however, few of these attempts have integrated direct balance control and realistic freedom of motion to deliver a real-world dynamic cycling experience. This study presents the BIKE (Bicycle Intrinsic Kinematics Emulator) system, a kinematic bicycle simulator, developed with the purpose of letting its users experience realistic steer, roll, yaw and sway motions. Motion is provided with Carvallo–Whipple bicycle model-based control of sway and yaw combined with passive steer and roll. This study validates the BIKE simulator by comparing cycling behaviour and subjective evaluation for the simulator with and without motion to outdoor tests with an instrumented bicycle. 15 participants of varying age and mass, performed straight-line cycling, at low ( 5 km/h ) to high ( 40 km/h ) velocities and zig-zag manoeuvres. Results show that users can successfully rely on existing cycling skills to use the simulator with motion. Objectively, in the kinematic sense, the simulator with motion performs similarly to an outdoor bicycle. Subjectively, the simulator performs better with motion and is experienced by riders as close to real outdoor cycling.

Seakeeping Behaviour of a Flettner Rotors-Propelled Catamaran in Beam Waves

This paper deals with the seakeeping of a catamaran propelled by Flettner rotors. The case study is an energy ship. The prediction of the roll motion of such a ship is of particular interest since she will mostly sail in beam seas. We used a numerical model based on the boundary element method to deal with the interactions of the ship with waves. It is supplemented by a model for the aerodynamic damping effect due to the rotors, the gyroscopic effects from the rotors and by the ITTC correction for roll damping. In the present study, it has been assumed that the Flettner rotors can be modelled as a distribution of elementary airfoils whose lift and drag depend on the local apparent wind speed. Interaction effects between the rotors and between the hull and rotors have been neglected. Regular waves have been investigated. For the considered case study, it is found that the Flettner rotors can have a small destabilizing effect or a small stabilizing effect on the ship motion depending on the ship speed and the rotors’ rotational speed.

Effects of roll motion on linear and nonlinear gap resonances in a moonpool excited by various incident-wave heights

The linear and nonlinear gap resonances in a free-rolling moonpool are investigated using a two-dimensional in-house code based on the constrained interpolation profile method. This study primarily focuses on the effects of roll motion on hydrodynamic characteristics, taking into account both the linear gap resonance and the nonlinear process-driven gap resonances. The analysis of the incident-wave height is conducted to illustrate the relationship between higher-order harmonics and nonlinear gap resonances. Numerical results demonstrate that the resonant frequency is insensitive to the roll motion. However, the roll response plays an important role in influencing the vertical wave loads on the barges and affecting the energy conversion pattern in the fluid field. According to the analysis of the incident-wave height parameter, the magnitudes of resonance at the linear and nonlinear resonant points are approximately in sub-linear and superlinear relationships with the incident-wave height, respectively. Moreover, the vortex shedding modes around the entrance of the free-rolling moonpool gradually transit from being dominated by the pairs of vortices to being dominated by the single vortex as the gap resonance changes from linear to quartic.

CFD-based Numerical Analysis of Amphibious Vehicle Hydrodynamics during Turning Motion

Amphibious vehicle has blunt bow and multi appendage structure, and its flow field characteristics are very complicated during maneuvering. In this paper, a simplified model of amphibious vehicle with propulsion device is established, and the thrust volume force model is introduced to consider the pumping and water jet propulsion of the water effects jet propulsion device. The technique of overlapping grid is used to deal with the six-degree-of-freedom large-scale hull motion problem, and study the turning motion of amphibious vehicle under different rudder angles. The results of numerical simulation show that the amphibious vehicle will enter a stable turning state when turning on the water surface, but the heel angle is large, the draft depth and the speed drop are significant. The state of water baffle has a significant influence on vehicle trim and roll motion. Larger vehicle pitching motion amplitude will increase the risk of overturning.

Eksperimentalno istraživanje o učinku položaja ljuljne kobilice na desantnim pomoćnim brodovima

The issue of energy efficiency in using fossil fuels and reducing the effects of greenhouse gas emissions is an urgent problem. So fuel-saving measures, including in the marine transportation sector, are needed, even if only by a small percentage. Landing Craft Utility (LCU) is a type of sea transport for defense matters that requires the addition of a rolling motion stabilizer for the safety and comfort of the ship, cargo, and passengers. The use of roll-damping devices can affect the increase in the resistance value of the ship and cause an increase in fuel consumption. The bilge keel is a roll-damping device that is suitable for LCU vessels. The experimental study roll decay tests and resistance tests were carried out to determine the effect of the bilge keel placement on roll damping and additional ship resistance. The flow around the vessel’s surface was observed with a paint smear test to determine the placement position. The bilge keel installed in the transitional position between the bottom and side hull has the highest total roll damping coefficient, up to 28.57%, compared to the bare hull condition. However, this placement has increased the average resistance up to 8.84%. Alternately, placement close to the draft line has a fairly good roll-damping coefficient of up to 21.27%, increasing the resistance to only 3.66%.

Cytological and microbiotic aspects of the diagnosis of otitis externa in dogs

The purpose of the study was to compare cytological samples from two consecutive swabs obtained from ear canals of dogs with otitis externa and to determine the minimum number of samples required to obtain up-to-date information on the degree of microbiological contamination of the affected ear canals. Samples were obtained using sterile applicators with a cotton tip, which were sequentially inserted into ear canal until slight resistance (the junction between vertical and horizontal parts of ear canal), after making a circular motion, the applicator was removed and the material from the tip was applied to the glass slide with rolling movements so that on each slide there were four single parallel smears - two from each ear of the dog. The slides were air dried for one hour and stained using the standard Diff-Quick method. The actual counting was carried out at 1000 magnification (at a high magnification field). Bacteria were differentiated according to their shape into cocci and bacilli. The numbers of bacteria and fungi in the two samples were compared using the Wilcoxon matched pair test. Qualitative agreement between two consecutive swabs was determined using the k-test. Among the studied animals, a breed predisposition to otitis externa was revealed in Cocker Spaniels and French Bulldogs, and an anatomical predisposition in animals with drooping auricles. There was no significant difference in the number of microorganisms present in two ear cytology samples taken consecutively from the same ear at the same site in the external auditory canal, and there was significant agreement between the results of two consecutive smears for the presence of cocci and rods. For yeast, the agreement was only moderate. The data obtained indicate that in cases of otitis externa in dogs, reproducibility of cytological pattern with a single sample of material, as a rule, reflects current stage of pathogenesis of the disease and provides the best opportunity to detect local proliferative activity of opportunistic microbiota and corresponding inflammatory response of the macroorganism.

Numerical analysis on flow distribution of nuclear reactor core inlet under ocean conditions

The high consumption of traditional energy is difficult to support the development of marine resources. Floating Nuclear Power Plant (FNPP) can be used for energy supply due to their advantages such as high power and low cost. Considering that ocean conditions can seriously cause flow fluctuations at the core inlet, this paper establishes a Reactor Pressure Vessel (RPV) model that includes a porous medium core model for numerical analysis. The momentum source is added to the control equation to achieve introduction of ocean conditions, which solves the problem of plane data errors in dynamic mesh method. Therefore, the flow distribution at the core inlet can be obtained under ocean conditions and the local flow characteristics in the lower chamber can be comprehensively observed. The results shown that nonlinear motion can promote more uniform flow distribution at the core inlet, enhancement of the additional force in motion can effectively suppress vortices. In the early stages of motion, rolling motion will cause inlet flow of most fuel assemblies to be too high or too low, it is necessary to adjust the reactor power output accordingly. In linear motion, surging motion does not improve the non-uniformity of flow distribution at the core inlet, but it can increase the stability of coolant flow in the lower chamber and reduces the number of vortices. Heaving motion has very little impact on flow distribution at the core inlet due to it is consistent with the mainstream direction. Coupled motion can enhance the uniformity of core inlet flow compared to single degree of freedom motion and more attention should be paid to adjusting initial reactor power output.