Traction Velocity Research Articles

Adaptive Robust Autonomous Obstacle Traversal Controller for Novel Six-Track Robot

The separate control method of flippers and the movement of the mass center makes the active articulated tracked robot unable to realize higher-level motion and difficult to adapt to rough and complex obstacle terrain. In this paper, a new design method of distributed autonomous obstacle traversal controller for the novel six-track robot is proposed. The controller establishes a unified control framework that includes all degrees of freedom of the robot so that the center of mass tracking error and flipper motion tracking error can converge simultaneously to achieve obstacle traversal independently of specific terrain or tasks. First, the forward kinematics model and differential kinematics model of tracked robot are established to generate 3D motion, including flipper angular velocity and body traction velocity. Then, the differential drive robot model is extended into the differential kinematic model to eliminate the slip effect during obstacle traversal. Finally, the feedback control law of the control system and the optimal solution for the singular position of the robot structure are established. In addition, several simulation experiments and physical prototype experiments in different obstacle terrains are executed. In the virtual simulation experiment, the average trajectory error of the flipper is about 0.029 m. In the physical prototype experiment, compared to the manual remote controller and the prior art controller, the average error norm of the center of mass is reduced by 40.7% and 13.5%, respectively; the maximum slip norm is reduced by 34.6% and 19.9%, respectively; and the obstacle crossing time is reduced by 21.3% and 9.3%, respectively, and they validate the accuracy and effectiveness of the designed controller.

Simulation and Analysis of the Working Process of Soil Covering and Compacting of Precision Seeding Units Based on the Coupling Model of DEM with MBD

In precision seeding, the final displacements of the seeds are determined as a working result of the profiling mechanism, opener, seed-metering device, covering apparatus and compacting machine. For a better understanding of the disturbance of seed displacement during soil covering and compaction in the actual working process, experiments and simulations have been performed. In this paper, a type of soybean seeding monomer was taken as the research object, and a soil bin test of soil covering and compacting was executed. The experimental results showed that the traction velocity and the open angle of the covering discs had a significant influence on the changes in the horizontal and vertical displacements of seeds during the soil covering processing. With an increasing traction velocity, the vertical displacements of seeds increased after soil covering; in contrast, the horizontal displacements decreased. When the covering apparatus had a larger open angle it had a smaller disturbance influence on the soil. Therefore, with an increase in the opening angle, the changes in the vertical and horizontal displacements of seeds showed a decreasing trend. Inversely, in the process of compacting, the forward velocity had little effect on the three-dimensional displacement change in the seeds after compacting. The analysis model of the precision seeding unit was established based on the coupling model of the DEM (discrete element method) with MBDs (multi-body dynamics). The process of soil covering and compacting was simulated and analyzed. The comparison between the experimental results and the simulated results showed that the trend was similar, and the two results were close. Thus, the feasibility and applicability of the coupling method were verified. It also provided a new method for the design and optimization of covering and compacting components of a precise seeding monomer.

The Effectiveness of Conventional and Accelerated Methods of Orthodontic Traction and Alignment of Palatally Impacted Canines in Terms of Treatment Time, Velocity of Tooth Movement, Periodontal, and Patient-Reported Outcomes: A Systematic Review.

The objective of the current review was to evaluate the effectiveness of traditional and accelerated methods of palatally impacted canine's (PIC) traction in terms of treatment duration, velocity, periodontal, and patient-reported variables.An electronic search for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) published between January 1990 and October 2021 was conducted in nine databases. Five major orthodontic journals were hand searched for additional studies. The participants were patients with unilateral or bilateral PICs who received conventional or accelerated orthodontic treatment with fixed appliances. Cochrane’s risk of bias tool (RoB 2 tool) for RCTs and ROBINS-I tool for CCTs were used to assess the risk of bias. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) guidelines were used to assess the overall quality of the evidence.Nine articles (eight RCTs and one CCT) were included in this review (371 patients). There was no clarity in most studies about the possible effect of the mechanical traction method on treatment outcomes. The treatment duration decreased (about three to six months) when the open surgical method was used with traditional techniques and the traction velocity increased significantly (about 1-1.5 mm/month) when acceleration methods were used. No significant differences were found between the conventional intervention groups, as well as between the traditional and accelerated groups, in terms of most periodontal variables (p > 0.005).No significant differences were found in the pain levels associated with traditional PICs' traction when comparing different exposure methods in the short-term follow-up (1-10 days), while contradictory results were found in the pain incidence between these methods. The relationship between the pain/discomfort levels and the type of mechanical traction method was not evaluated. According to the GRADE, the quality of evidence supporting these findings ranged from low to very low.The combination of the open surgical technique with various designs of either superelastic wires or elastic traction means can lead to a reduction in the orthodontic treatment duration of PICs. The use of direct anchorage by miniscrews to move the PICs away from the adjacent teeth roots can lead to a reduction in root resorption and shorten the treatment duration. The evidence supporting these findings ranged from low to very low. The use of different types of mechanical means for conventional PICs' traction, with the use of open or closed traction techniques, does not lead to significant differences in periodontal outcomes between intervention groups. Contradictory results exist regarding the severity of the perceived pain in relation to the surgical exposure type, and the relationship between this variable and the mechanical traction method is still unclear. The use of accelerated methods for PICs' traction can lead to an increase in the velocity of traction movement with no significant differences in periodontal outcomes between accelerated and conventional methods. The evidence supporting these findings ranged from low to very low. More high-quality randomized CCTs are needed to establish good evidence in this field.The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42021274476) during the first stages of this review.

A study of wheel wear on a high-speed railway motor car

Wheel/rail wear is one of the key issues in the safe operation of a high-speed railway motor car. This paper analyzes and predicts the wheel wear evolution of motor car during the long-term operation process. Firstly, the detailed motor car with gear transmission systems and trailer car of the high-speed train, which take into account various non-linear factors such as dampers, bump stops, wheel/rail contact relation, etc., are developed to obtain interaction force between wheel and rail. Secondly, according to the tread update strategy based on fixed travel distance, a novel wheel wear prediction model integrating the Archard wear model and previous dynamics system is established. In order to more accurately obtain the dynamic responses of the motor car, the comprehensive gear transmission system coupling with motor bogie is also built, which considers the time-varying mesh stiffness and gear shift coefficient. And the corresponding traction characteristic curve is also applied to the gear transmission system. Finally, the wheel wear evolution in one re-profiling cycle is simulated to verify the developed model, and the wheel wear mechanism is investigated in detail. Furthermore, the influence of traction velocity on wheel wear is also investigated. The simulation shows that the cumulative wear amount of both two cars increases gradually and the wear rate decreases gradually with traveling mileage, but the wear rate of the trailer car decreases faster than that of the motor car due to larger longitudinal creepage and longitudinal creep force induced by traction torque. Moreover, the max wheel wear depth and wear bandwidth for motor car gradually increase with traction velocity. While the discrepancies of the max wheel wear depth and wear bandwidth for trailer car are small under different speeds.

Research on the traction dynamic of shearer based on the pose analysis

The high reliability traction of the shearer is the key to realize safe and efficient coal mining. However, with the popularity of high-power and high-speed shearer, the drawback of frequent failure of traction unit is increasingly apparent. Therefore, to improve the traction reliability of the shearers, a dynamic model of double traction units of the shearer was established. Based on the pose analysis, the dynamic properties of the traction unit were studied, and the effects of constraint state, traction velocity, coal seam dip, depression mining angle and drum steering were discussed. The results show that the dynamic difference between the two traction units is significant affected by the shearer pose. The x-axis swing of the shearer increases the support load of the walking wheel, the y-axis swing intensifies the unbalance of the lateral force of the guide slipper, and the z-axis swing aggravates the fatigue wear of the right support slipper and the impact wear of the left. The load uniform quality of the guide slipper decreases with the increase of velocity and coal seam dip. And the inward contra-rotating of the drum and appropriately increasing the depression angle can improve the load uniform characteristics of the support slipper. The results provide a reference for improving the traction reliability of the shearer and optimizing mining technology.

Dynamic Analysis of Shearer Traction Unit Considering the Longitudinal Swing

Shearer traction failure occurs frequently, which seriously restricts the safe and efficient mining of coal. However, the influence of the shearer’s posture on traction has not been fully considered in the existing research. To improve traction reliability: the dynamic model of the traction unit is established considering longitudinal swing; the walking characteristics of the shearer and the dynamics of the traction unit are analyzed; and the influences of traction velocity, drum load cutting arm angle, and depression angle are discussed. The results show that the longitudinal swing is reciprocating and the positive swing is more serious. With the increase of the traction velocity, the walking stability of the shearer decreases while the contact force increases, especially the support slipper. The longitudinal swing increases with the increase of lateral load, but the supporting force of the support slipper decreases with the increase of cutting load. The forces of the walking wheel and the support slipper show an increasing trend with the increase of cutting arm angle. When the depression angle is 5–10°, the load distribution of the contact components of the traction unit is more balanced. The results provide a reference for the structure optimization of the shearer and the layout of coalface.

The Effects of Traction Velocity on the Gas-assisted Extrusion Forming and Traditional Extrusion Forming of Plastic Microtubes

The effects of traction velocity on gas-assisted extrusion (GAE) and traditional extrusion (TE) of plastic micro-tubes (PMTs) were numerically studied in this paper. Under same 3D geometric model, boundary conditions setting and constitutive parameters, the extrudate profile change and swell ratios of GAE and TE were all obtained. The radial and axial flow velocities, shear stress and first normal stress difference distributions of melt under different traction velocities were also gotten and compared. Results show that with the increase of traction velocity, the swell ratio increases first and then decreases. When the traction velocity is less than the axial velocity of melt, the radial velocity of melt outside of die increases, which demonstrates the generation of radial swell. When traction velocity is larger than that of the melt, the negative radial velocity of melt generates, which demonstrates the generation of shrinkage phenomenon. In addition, the changes of shear stress values and first normal stress difference values are not large, and the sudden increase of stresses always generates at the outlet die for the TE. However, the stresses of melt are well removed at the outlet of die, which demonstrates that extrudate swell and melt fracture problems are well eliminated by the GAE during the extruded PMTs dragged by traction velocity.

Simulation and Experiment on Extrusion Molding of Five-Lumen Medical Catheter

We choose the optimal cross-sectional shape of the polymer five-lumen catheter products as the goal, and the simulation and experiment of extrusion process parameters were carried out. Firstly, the effect of gas injection pressure and extrusion rate on the extrusion expansion ratio, and the influence of gas injection pressure, extrusion rate and traction speed on the cross-section size, was studied by using Polyflow software; The effects of gas injection pressure, extrusion rate and traction velocity on the five-lumen catheter were studied, the experimental results are compared with the numerical simulation results. The optimal combination of the parameters of the extruded five-lumen catheter is obtained by orthogonal experiment, I.e., the head temperature T = 210 °C, injection pressure P = 4515Pa, the extrusion rate v = 4.5mm / s, pulling speed vp = 33.83mm / s; The corresponding relative error is: Primary lumen relative error Y1 = 3.46%, secondary lumen relative error Y2 = 3.33%, the minimum relative error lumen Y3 = 1%, the outer contour relative error Y0 = 0.61%.

Termination of atrial spiral waves by traction into peripheral non 1:1 conducting regions – A numerical study

Atrial ablation has been recently utilized to treat atrial fibrillation (AF) by isolation or destruction of arrhythmia drivers. In chronic or persistent AF patients these drivers often consist of one or few rotors at unknown locations, and several ablations are commonly conducted before arrhythmia is terminated. However, the irreversible damage done to the tissue may lead to AF recurrence. We propose an alternative strategy to terminate rotor activity by its attraction into a non 1:1 conducting region. The feasibility of the method was numerically tested in 2D models of chronic AF human atrial tissue. Left-to-right gradients of either acetylcholine (ACh) or potassium conductance were employed to generate regions of 1:1 and non 1:1 conduction, characterized by their dominant frequency (DF) ratios. Spiral waves were established in the 1:1 conducting region and raster scanning was employed using a stimulating probe to attract the spiral wave tip. The probe was then linearly moved towards the boundary between the two regions. Successful attraction of spiral waves to the probe was demonstrated when the probe was <8mm from the spiral wave tip. Maximal traction velocity without loss of anchoring increased in a non-linear way with increasing values of ACh. Success rate of spiral wave termination was over 90% for regional DF ratios of as low as 1:1.2. Given that normally much higher ratios are measured in physiological atrial tissues, we envision this technique to provide a feasible, safer alternative to ablation procedures performed in persistent AF patients.

Experimentations on the adaptive sliding mode control for a trajectory tracking applied on a bi-steerable car

Chattering is known as the most important drawback of sliding mode control (SMC). The latter is robust against external perturbations and model incertitude. The objective of this paper is to provide adaptive SMC laws allowing control of a complex system while avoiding or reducing chatter effects. The controlled system is called Robucar, it is a four wheel mobile robot car in double steering mode also called a bi-steerable car (Bis-Car). It is a non-holonomic, non-linear and under-actuated system. A robust adaptive SMC law is designed to reduce the chatter effect while keeping the robustness properties. The robustness and the applicability of the control laws are shown in simulation tests first, and then in experimental tests where perturbations are considered by introducing errors on the initial position, the traction velocity and the steering angle.

Symmetry relations in viscoplastic drag laws.

The following note shows that the symmetry of various resistance formulae, often based on Lorentz reciprocity for linearly viscous fluids, applies to a wide class of nonlinear viscoplastic fluids. This follows from Edelen's nonlinear generalization of the Onsager relation for the special case of strongly dissipative rheology, where constitutive equations are derivable from his dissipation potential. For flow domains with strong dissipation in the interior and on a portion of the boundary, this implies strong dissipation on the remaining portion of the boundary, with strongly dissipative traction-velocity response given by a dissipation potential. This leads to a nonlinear generalization of Stokes resistance formulae for a wide class of viscoplastic fluid problems. We consider the application to nonlinear Darcy flow and to the effective slip for viscoplastic flow over textured surfaces.

B-18 スキー滑走時動摩擦に高次の機械力学的振動がスキー板に及ぼす影響(スキー)

The purposes of this study was to develop a simulator generating a ski board vibration in actual skiing and to clarify the relationship between ski board vibration and a coefficient of kinetic friction. In the simulator developed in this study, the surface on the bottom of the ski was assumed as to be a snowy slope and a mass of snow (snow pack) assuming a skier had slid on this ski bottom surface. A ball vibrator connected to a large-sized compressor was installed onto the ski panel in order to vibrate a ski board. The compressed air from the compressor rotated a steel ball in the vibrator at high speed, causing vibration on the ski. A dynamic friction force (F) was detected by the digital force gauge when the snow pack was sliding on the surface in isokinetic condition using a traction device. A traction velocity was controlled automatically using controller. A coefficient of kinetic friction was calculated using this dynamic friction force. The experiment using this simulator was carried out in the low temperature laboratory conditions. On experimental result, in this study, the higher vibration was, the lower the coefficient of kinetic friction was. From these results, it is clarified that the high frequency of the mechanical dynamic vibration reduces the coefficient of kinetic friction.

J2310103 スキー滑走時動摩擦に200Hzのスキー板の振動が及ぼす影響([J231-01]スポーツ工学(1))

The purposes of this study was to develop a simulator generating a ski board vibration in actual skiing and to clarify the relationship between ski board vibration and a coefficient of kinetic friction. In the simulator developed in this study, the surface on the bottom of the ski was assumed as to be a snowy slope and a mass of snow (snow pack) assuming a skier had slid on this ski bottom surface. A ball vibrator connected to a large-sized compressor was installed onto the ski panel in order to vibrate a ski board. The compressed air from the compressor rotated a steel ball in the vibrator at high speed, causing vibration on the ski. A dynamic friction force (F) was detected by the digital force gauge when the snow pack was sliding on the surface in isokinetic condition using a traction device. A traction velocity was controlled automatically using controller. A coefficient of kinetic friction was calculated using this dynamic friction force. The experiment using this simulator was carried out in the laboratory conditions. On this experimental result, the relationship between the coefficient of kinetic friction and sliding velocity in non-vibration (0Hz) condition was not significant statistically. On the other hand, the coefficient of kinetic friction decreased with increasing in sliding velocity in vibration (253Hz) condition and both relationship was significant statistically. From these results, it is clarified that the mechanical dynamic vibration reduces the coefficient of kinetic friction with increasing in the sliding velocity.

球による動力伝達機構を用いたアクティブキャスタの運動解析と機構設計

This paper presents a new wheel mechanism for the active-caster drive system. The active-caster provides omnidirectional mobility with no using free rolling mechanism. The original active-caster equips with an absolute encoder to detect a wheel orientation and two motors for driving wheel and steering axis independently. A computer system needs to detect an absolute wheel orientation and coordinate velocity components for wheel and steering drive to provide wheel motion in an arbitrary direction. To simplify the wheel control system, a new active-caster mechanism is proposed. A proposed active-caster system includes a ball transmission to distribute a traction velocity to wheel and steering axis mechanically without using an angle sensor or coordinated motor control. In this paper, kinematics of the proposed wheel mechanism is analyzed and mechanical condition for realizing the caster motion is derived. A kinematic model of the proposed active-caster mechanism with a ball transmission is analyzed and a mechanical condition for realizing caster motion is derived. Based on the kinematic model and the mechanical condition, computer simulations of the mechanism are performed. In the simulations, the active-caster shows successful caster motions with no sensor or computer system.

Force transmission in migrating cells

During cell migration, forces generated by the actin cytoskeleton are transmitted through adhesion complexes to the substrate. To investigate the mechanism of force generation and transmission, we analyzed the relationship between actin network velocity and traction forces at the substrate in a model system of persistently migrating fish epidermal keratocytes. Front and lateral sides of the cell exhibited much stronger coupling between actin motion and traction forces than the trailing cell body. Further analysis of the traction-velocity relationship suggested that the force transmission mechanisms were different in different cell regions: at the front, traction was generated by a gripping of the actin network to the substrate, whereas at the sides and back, it was produced by the network's slipping over the substrate. Treatment with inhibitors of the actin-myosin system demonstrated that the cell body translocation could be powered by either of the two different processes, actomyosin contraction or actin assembly, with the former associated with significantly larger traction forces than the latter.

Hidden order in crackling noise during peeling of an adhesive tape

We address the longstanding problem of recovering dynamical information from noisy acoustic emission signals arising from peeling of an adhesive tape subject to constant traction velocity. Using the phase space reconstruction procedure we demonstrate the deterministic chaotic dynamics by establishing the existence of correlation dimension as also a positive Lyapunov exponent in a midrange of traction velocities. The results are explained on the basis of the model that also emphasizes the deterministic origin of acoustic emission by clarifying its connection to stick-slip dynamics.

Effect of Directional Solidification Rate on Preferred Orientation, Microstructure and Magnetostriction of (Tb0.3Dy0.7)Fe1.95 Alloys

The effect of solidification rate on the preferred orientation, microstructure and magnetostriction of (Tb0.3Dy0.7)Fe1.95 alloys was investigated using a new “one-step” process. The functional relation between the crystal growth rate and the traction velocity was determined by the analysis of heat transfer. Results demonstrate that the crystal grows synchronously with the traction velocity as the traction velocity U≤360 mm/h. When the thermal gradient GL≈100°C/cm and the solidification rate V=70 mm/h, samples with a <110> preferred orientation can be obtained. Samples with the <110> preferred orientation show a large low-field magnetostriction and an apparent compressive stress effect. With an increase in solidification rate, the crystal growth mode will transform gradually from the cellular and primary dendrite morphology into the developed dendrite morphology. Crystals growing in the cellular morphology have a <110> preferred orientation. In the primary dendrite, the preferred orientation is <113>. However, a poor magnetostrictive performance and failed preferred orientation are observed in the developed dendrite.

Fracture toughness in fibrous materials.

In the present paper, a fiber bundle model in (1+1) dimensions that simulates the rupture process of a fibrous material pulled by an uniaxial force F is analyzed. In this model the load of a broken fiber is shifted in equal portions onto the nearest unbroken fibers. The force-displacement diagram is obtained for several traction velocities v and temperatures t. Also, it is shown how the fracture toughness K(c) changes with the traction velocity v and with the temperature t. In this paper it is shown that the rupture process is strongly dependent on temperature t and on velocity v.

Self-Organized Criticality in a Model for Fracture on Fibrous Materials

We investigate the existence of self-organized criticality on a model to describe the failure process in fibrous materials. This model consists of identical parallel fibers which are pulled with constant velocity. The rupture probability of each fiber depends on the elastic energy of the fiber and on the number of unbroken neighboring fibers. In the brittle-ductile transition, we have observed a power law behaviour on the number of cracks versus its size. This indicates that, in this region, the model shows self-organized criticality and the fracture pattern can be a fractal. The power law exponent is not universal, but depends on the temperature and traction velocity.

A model of feeding currents in encrusting bryozoans shows interference between zooids within a colony

A potentially important consequence of colony morphology in colonial suspension feeders such as bryozoan colonies is the hydrodynamic interaction between modules (zooids). In this paper, a detailed numerical model of water flow through an encrusting bryozoan colony is developed, using the theory of flow around slender bodies in slow flow (low Reynolds number), which calculates flow properties everywhere within a colony. Ciliated tentacles are represented by an extension of previous slender body theory to include cylinders with a “traction velocity” at their surfaces. The traction velocity, which is tangent to the cylinder surface, represents the macroscoic flow induced by ciliary action. This modeling approach makes it possible to calculate the self-induced flow through a complex geometry—in this case a colony of up to 121 zooids—which would be computationally difficult using mesh-based methods. Calculations of flow through model colonies indicate that there are strong, negative hydrodynamic interactions between zooids in a colony of this type. Zooids interfere with one another because areas of high shear beneath the lophophores cause viscous resistance to excurrent flow, resulting in high pressure in the interior of colonies. The ability of interior zooids to pump water through the lophophores is thereby greatly reduced. In contrast, a linear arrangement of zooids, as found in less-integrated and stoloniferous colonies, greatly reduces interference. Strong hydrodynamic interference between zooids suggests that there must exist other functional factors which enable highly-integrated colonies to compete successfully with arborescent and stoloniferous forms.