Trajectory compensation for multi-robot coordinated lifting system considering elastic catenary of the rope

The multi-robot coordinated lifting system is an unconstrained system with a rigid and flexible coupling.The deformation of the flexible rope causes errors in the movement trajectory of the lifting system.Based on the kinematic and dynamic analysis of the lifting system,the elastic catenary mod-el considering the elasticity and mass of the flexible rope is established,and the effect of the deform-ation of the flexible rope on the position and posture of the suspended object is analyzed.According to the deformation of flexible rope,a real-time trajectory compensation method is proposed based on the compensation principle of position and posture.Under the lifting task of the low-speed move-ment,this is compared with that of the system which neglects the deformation of the flexible rope.The trajectoy of the lifting system considering the deformation of flexible rope.The results show that the mass and elasticity of the flexible rope can not be neglected.Meanwhile,the proposed trajectory compensation method can improve the movement accuracy of the lifting system,which verifies the ef-fectiveness of this compensation method.The research results provide the basis for trajectory plan-ning and coordinated control of the lifting system。

Theoretical coupling longitudinal-transverse model and experimental verification of transverse vibration of rope for multi-rope friction hoisting system

Using the mass of time-varying length balance rope focused on the hoisting conveyance, the coupling longi- tudinal-transverse model of mine friction hoist was established by using of the Hamilton＇s principle. The modified Galerkin＇s method was used to discretize partial differential Eqs. The mine hoisting system was used to the example to analysis the relation between the load, velocity and transverse vibration of rope. The in situ tests were illustrated to evaluate the proposed mathematical model. The results showed that the modeling method can well represent the transverse vibration of rope.

Consecutive Impact Loading and Preloading Effect on Stiffness of Woven Synthetic-Fiber Rope

We studied consecutive impact loading on woven high-modulus polyethylene rope, which is used in robotics fields. An impact tester was developed to conduct the experiments. Five consecutive impact loads (five drops) were applied to the rope and the stiffness of the loading part that corresponds to each drop was evaluated. The stiffness of the woven ropes was affected strongly by consecutive impact loading. The change in stiffness is undesirable in some applications such as in robotic fields. Therefore, we have proposed a method that can optimize changes in stiffness by applying a preload before impact testing (preload treatment). The experimental results show that preload is an efficient way to reduce changing rope stiffness. We have also proposed an empirical equation that can estimate the rope stiffness after arbitrary preload treatment, and this equation is a function of the number of drops and the static preload level. The equation can be used to determine the preload treatment conditions to stabilize the stiffness of the woven ropes before they are used in engineering fields.

解剖型锁定钢板联合TightRope内固定治疗锁骨远端骨折的效果

目的:探讨解剖型锁定钢板联合Tight Rope内固定治疗锁骨远端骨折的效果。方法:回顾分析常熟市第二人民医院创伤骨科2015年4月—2021年6月收治的93例锁骨远端骨折患者,按其治疗方式分对照组(n=46)和观察组(n=47)。对照组接受锁骨钩钢板内固定治疗,观察组接受解剖型锁定钢板联合Tight Rope内固定治疗。比较两组患者围手术期指标、肩关节功能、骨形成蛋白-2(BMP-2)、凝血指标、并发症发生率。结果:两组术中出血量比较,差异无统计学意义(P>0.05);观察组手术时间长于对照组,但骨折愈合时间、术后住院时间均短于对照组,差异均有统计学意义(P<0.05)。术后1、3个月,观察组肌力、肩关节活动度、日常活动、疼痛评分均高于对照组,差异均有统计学意义(P<0.05)。术后1周,观察组BMP-2、凝血酶原时间(PT)均高于对照组,纤维蛋白原(FIB)、D-二聚体(D-D)均低于对照组,差异均有统计学意义(P<0.05)。观察组并发症发生率(4.26%)低于对照组(21.74%),差异有统计学意义(P<0.05)。结论:相比于锁骨钩钢板内固定术,解剖型锁定钢板联合Tight Rope内固定术治疗锁骨远端骨折的效果更理想,在患者术后肩关节功能恢复、骨折愈合、并发症控制等方面均有明确优势。

The siphonic energy transfer between hot solar wind and cold martian ionosphere through open magnetic flux rope

A mechanism for energy transfer from the solar wind to the Martian ionosphere through open magnetic flux rope is proposed based on the observations by Mars Atmosphere and Volatile EvolutioN(MAVEN).The satellite was located in the dayside magnetosheath at an altitude of about 70o km above the northern hemisphere.Collisions between the hot solar wind protons and the cold heavy ions/neutrals in the subsolar region can cool the protons and heat the heavy ions.As a result,the magnetosheath protons are siphoned into the ionosphere due to the thermal pressure gradient of protons and the heated heavy ions escape along the open magnetic field lines.Although direct collisions in the lower-altitude region were not detected,this physical process is demonstrated by MAVEN measurements of enhanced proton density,decreased proton temperature and oppositely directed motions of hot and cool protons within the flux rope,which are very different from the observational features of the flux transfer events near the Earth's magnetopause.This mechanism could universally exist in many contexts where a collisionless plasma region is connected to a collisional plasma region.By reconstructing the magnetic geometry and the cross-section of the flux rope using the Grad-Shafranov technique,the ion loss rates are quantitatively estimated to be on the order of 1023 s-l,which is much higher than previously estimated.

BIOGEOGRAPHIC RELATIONS OF THE JURASSIC PECTINOIDA AND OSTREOIDA (BIVALVIA) BETWEEN TANGGULA AND OTHER AREAS

There are abundant Bajocian—Tithonian bivalves in the main ridge of the Tanggula Mountains of northern Qinghai—Xizang Plateau, China. After figuring the common and coeval species between Tanggula and other areas (Fig. 1), and tracing the temporal and spacial historical distribution of the bivalves very capable of dispersion, some Jurassic bivalve biogeographic items, particularly the biogeographic relations, have been lit up. In the known 21 taxa of the Jurassic Pectinoida and Ostreoida from the main ridge of the Tanggula Mountains, there are 12 (57%) common and coeval species in northern Tethys, 13 (62%) common and coeval species in southern Tethys and 12 (57%) in Kachchh—southern Xizang area. It has demonstrated that there existed intermigration of bivalves between Tanggula and various parts of Tethys. Although there is no coeval species between Tanggula and western Australia, in these two areas there exist 6 (29%) close range common species of which 4 (19%) coevaity existed in western Australia and India Plate. Tanggula fauna is, therefore, still very close to that of western Australia. However, there are 15 (71%) common and 14 (67%) coevality species between the main ridge of the Tanggula Mountains and northwestern Europe, among the common species, 8 (38%) ones have lower limitation (first occurrence) in northwestern Europe but only 2 (10%) taxa are older in the main ridge of the Tanggula Mountains. It is very clear that pectinite and ostrea fauna of Tethys, particularly the main ridge of the Tanggula Mountains and Europe had very close relation and most Tanggula’s or northern Tethyan taxa migrated from northwestern Europe.

Exploration of the mechanism of cavitation vortex rope and vortex development in the draft tube of tubular turbine units

Draft tube vortex rope is considered a special cavitation flow phenomenon in tubular turbine units.Cavitation vortex rope is one of the most detrimental factors affecting the safety of hydraulic turbines.In this study,ANSYS CFX software was utilized to numerically simulate the internal cavitation flow of a hydraulic turbine draft tube.The evolution of the cavitation vortex core was characterized by vortex line distribution and vorticity transport equation.The shape and number of blades influenced the revolving direction and distribution characteristics of the vortex close to the runner cone,which formed a counterclockwise-clockwise-counterclockwise distribution pattern.Simultaneously,there were many secondary flows in the draft tube.Mutual cancellation and dissipation between the flows was one of the reasons for reduction in vorticity.When the cross-sectional shape of the draft tube was changed,the vorticity was distributed from the center of the vortex rope to all parts of the cross-sectional draft tube,with extreme values at the center and at the walls.The vortex stretching and dilatation terms played a major role in the change in vorticity,with the baroclinic torque having an effect at the center of the vortex rope,this study is helpful to understand the flow of water in the draft tube and guide the design and optimization of the draft tube in engineering application.

Distribution of wire deformation within strands of wire ropes

Using ANSYS software, we developed a modeling program for several kinds of wire ropes with metal cores and built a geometric model for the 6×19 IWS wire rope. Through proper grid partitioning, a finite element model for calculating the deforma-tion of wire rope was obtained. Completely constraining one end of the wire rope and applying an axial force to the other end, we established the boundary conditions for solving the model. In addition, we numerically simulated the stress and deformation of the wire, obtaining the deformation distribution of each wire within the wire rope under different laying directions. At the end, a tensile test of the 6×19 IWS wire rope was carried out and the results of simulation and experiment compared.

Effect of Tension on Friction Coefficient Between Lining and Wire Rope with Low Speed Sliding

In order to obtain the exact friction coefficient between lining and wire rope, the tension of wire rope is studied as a factor which affects this coefficient. A mechanical model of a wire rope subjected to axial load was established to determine the torque of the wire rope. The contact motion between lining and wire rope was regarded as a screw rotation and the axial force of the lining resulting from the torque of the wire rope was analyzed. Theoretical formulas relating tension of the wire rope and the friction coefficient was obtained. Experiments between lining and wire rope with low sliding speed were carried out with friction tester made by us. Experimental results show that increment of the friction coefficient is proportional to that of the tension of the wire rope with a low sliding speed. The experimental results agree with the theoretical calculation; the errors are less than 6%, which oroves the validity of the theoretical model.

Analysis and control of vibration of ropes in a high-rise elevator under earthquake excitation

In this research, the vibration of elevator ropes, including the main rope and compensation rope are investigated simultaneously in a high-rise elevator system under earthquake excitation. Moreover, the paper presents a new control method to restrain the sway of both ropes. This study considers varying rope lengths during elevator operation which cause other system parameters such as natural frequency, and damping ratio to be time-variant variables. The dynamics of the ropes are analyzed by solving the governing non-stationary, nonlinear equation numerically. In order to mitigate the vibration of ropes in several motion conditions, particularly upwards movement, downward movement, stopped at the lowest position, and stopped at the highest position, an active equipment is installed at the compensation sheave. The stability of the system using the controller is analyzed at four states: without disturbance and static car, without disturbance and mobile car, including disturbance and static car, and including disturbance and mobile car. The efficiency of the controller used for dampening the vibration of elevator ropes is validated by numerical simulation results.

Preparation and Characterization of Resistive Strain Sensor Based on Braided Skin-Core Rope

This study proposed a new yarn-like strain sensor on the basis of the braided skin-core rope,and investigated the effect of braiding structures on the sensing properties of sensors.The morphology and electromechanical properties of the strain sensor with different braiding structures were compared and evaluated.The results show that the sensing performance of the sensor from a braided skin-core rope depends on both the number of yarns in braiding and the metallized process of braided rope.Generally,the present stretchable skin-core rope-based sensor provides a basis for the formation of a highly sensitive sensing structure.

Numerical investigation of the seismic response of a UHV composite bypass switch retrofitted with wire rope isolators

An ultra-high voltage(UHV)composite bypass switch(BPS)faces increasing seismic challenges when UHV projects extend to high seismic intensity areas.The UHV composite BPS still generates excessive stress at the bottom section although hollow composite insulators with high flexural strength are adopted.Since the standard retrofitting strategy by using stiffer supports cannot reduce stress responses,wire rope isolation is introduced.The optimal design of isolation considers both stress and displacement responses since the slenderness and composite material of insulators contribute to significant displacement.The results show that properly designed isolation can significantly reduce stress without excessive displacement responses.A larger radius configuration helps to improve the applicability of small stiffness isolators under high winds.When the isolation still cannot satisfy the requirement,smaller stiffness isolators with a larger radius,or isolators with increased loops and smaller radius,can be introduced to gain better energy dissipation capacity and effectiveness in response mitigation.Accordingly,a three-step design procedure is proposed to increase the damping force but fix the rotational stiffness of isolation.Hence,the application of wire rope isolation can be extended to UHV composite BPS with a low natural frequency,but conductors with enough redundancy should be used.

The finite element modeling of spiral ropes

Accurate understanding the behavior of spiral rope is complicated due to their complex geometry and complex contact conditions between the wires.This study proposed the finite element models of spiral ropes subjected to tensile loads.The parametric equations developed in this paper were implemented for geometric modeling of ropes.The 3D geometric models with different twisting manner,equal diameters of wires were generated in details by using Pro/ENGINEER software.The results of the present finite element analysis were on an acceptable level of accuracy as compared with those of theoretical and experimental data.Further development is ongoing to analysis the equivalent stresses induced by twisting manner of cables.The twisting manner of wires was important to spiral ropes in the three wire layers and the outer twisting manner of wires should be contrary to that of the second layer,no matter what is the first twisting manner of wires.

Coronal Magnetic Flux Rope Equilibria and Magnetic Helicity

Using a 2.5-dimensional (2.5-D) ideal MHD model, this paper analyzes the equilibrium properties of coronal magnetic flux ropes in a bipolar ambient magnetic field. It is found that the geometrical features of the magnetic flux rope, including the height of the rope axis, the half-width of the ropes and the length of the vertical current sheet below the ropes are determined by a single magnetic parameter, the magnetic helicity, which is the sum of the self-helicity of the rope and the mutual helicity between the rope field and the ambient magnetic field. All the geometrical parameters increase monotonically with increasing magnetic helicity. The implication of this result in solar active phenomena is briefly discussed.

Swing Suppression and Accurate Positioning Control for Underactuated Offshore Crane Systems Suffering From Disturbances

Offshore cranes are widely applied to transfer largescale cargoes and it is challenging to develop effective control for them with sea wave disturbances. However, most existing controllers can only yield ultimate uniform boundedness or asymptotical stability results for the system's equilibrium point, and the state variables' convergence time cannot be theoretically guaranteed. To address these problems, a nonlinear sliding mode-based controller is suggested to accurately drive the boom/rope to their desired positions. Simultaneously, payload swing can be eliminated rapidly with sea waves. As we know, this paper firstly presents a controller by introducing error-related bounded functions into a sliding surface, which can realize boom/rope positioning within a finite time, and both controller design and analysis based on the nonlinear dynamics are implemented without any linearization manipulations. Moreover, the stability analysis is theoretically ensured with the Lyapunov method. Finally, we employ some experiments to validate the effectiveness of the proposed controller.

Morphology controllable growth of CaO/amorphous carbon ropes by a hydrothermal approach

A versatile hydrothermal strategy for the growth of a centimeter-sized CaO/amorphous carbon rope was introduced in this article. It is demonstrated that the centimeter-sized rope is composed of abundant amorphous carbon ＂belt＂ and ＂stick＂ with small polygonal CaO particles in the size of 3.0-5.0 nm embedded in the ＂belt＂ and ＂stick＂ framework. With the increase in NaOH amount, polygonal Ca（OH）2 particles in the size of 0.5-3.0 μm are found, instead of the CaO/amorphous carbon rope. This morphology evolution results from the competition of structure-directing and hydrothermal-carbonizing of organic agents during hydrothermal reaction. These results may give good suggestions for the controllable growth of newly unique morphological micro/nano architectures in solution phase reactions.

小切口复位Tight Rope纽扣钢板内固定治疗RockwoodⅢ型肩锁关节脱位的效果观察

目的:探讨小切口复位Tight Rope纽扣钢板内固定治疗RockwoodⅢ型肩锁关节脱位的效果。方法:选取89例RockwoodⅢ型肩锁关节脱位患者,按照随机数字表法将其分为两组。对照组44例,采用锁骨钩钢板内固定术,观察组45例,采用小切口复位Tight Rope纽扣钢板内固定术,观察两组手术相关指标、肩关节功能、疼痛程度、创伤应激指标及并发症发生率。结果:观察组手术相关指标优于对照组,术中出血量少于对照组,差异有统计学意义(P<0.05);术后1 d,观察组CMS各维度得分高于对照组(P<0.05);术后1 d、3 d、7 d,观察组VAS评分均低于对照组(P<0.05);术后,两组Cor、ACTH均升高,且观察组低于对照组(P<0.05);观察组并发症发生率6.67%低于对照组20.45%(P<0.05)。结论:小切口复位Tight Rope纽扣钢板内固定治疗RockwoodⅢ型肩锁关节脱位,减少手术创伤,缩短手术时间,减轻疼痛,安全性较好。

On the Thermal Conductivity of Single-Walled Carbon Nanotube Ropes

Recently measured thermal conductivity in single-walled carbon nanotube ropes in the temperature range 8 - 350 K has been explained using an anisotropic dynamical model which not only takes into account the quasi two-dimensional nature of the folded graphene sheets that forms the nanotubes, but also the intertube coupling, in addition to the phonon frequency and dimensionality dependent relaxation time of phonon-phonon scattering and interaction.

CONDITION MONITORING AND FAULT DIAGNOSIS FOR TENSION UNBALANCE OF ROPES IN MULTI-ROPE FRICTION WINDER

This paper analyzes the reasons of the tension unbalance of the ropes in multi-rope fric-tion winder, introduces the method of an on-line monitoring rope tensions with a testing device de-veloped by authors, and proposes the criteria of the fault diagnosis and the method of adjustment for the tension unbalance of the ropes, which is important to the theoretical study on the tension unbalance of the ropes and the maintenance of multi-rope winder.

Know the Ropes

A good sailor knows all about ropes and how to tie theminto knots.From that we have this idiom,and it means toknow all there is about a job,a hobby,a business or a method.“You’ll never get to know the ropes if you continue to day-