Multipoint Contact Research Articles

Haptic rendering and interactive simulation using passive midpoint integration

We propose a novel framework of haptic rendering and interactive simulation, which, by exploiting midpoint time integration, that is known for its superior energy-conserving property but has not yet been adopted for haptics and interactive simulation, can enforce discrete-time passivity of the simulation effectively in practice, while retaining real-time interactivity due to its being non-iterative. We derive this passive midpoint integration (PMI) simulation for mechanical systems both in maximal coordinates (i.e. in SE(3)) and in generalized coordinates (i.e. in ), with some potential actions as well to implement joint articulation, constraints, compliance, and so on. We also fully incorporate multi-point Coulomb frictional contact into them via the PMI-LCP (linear complementarity problem) formulation. The proposed PMI-based simulation framework is applied to some illustrative examples to demonstrate its advantages: (1) haptic rendering of a peg-in-hole task, where very light/stiff articulated objects can be simulated with multi-point contact; (2) haptic interaction with a flexible beam, where marginally stable/lossless behavior (i.e. vibration) can be stably emulated; and (3) under-actuated tendon-driven hand grasping, where mixed maximal-generalized coordinates are used with very light/stiff fingers.

Structural and functional characterization of the PNKP-XRCC4-LigIV DNA repair complex.

Non-homologous end joining (NHEJ) repairs DNA double strand breaks in non-cycling eukaryotic cells. NHEJ relies on polynucleotide kinase/phosphatase (PNKP), which generates 5΄-phosphate/3΄-hydroxyl DNA termini that are critical for ligation by the NHEJ DNA ligase, LigIV. PNKP and LigIV require the NHEJ scaffolding protein, XRCC4. The PNKP FHA domain binds to the CK2-phosphorylated XRCC4 C-terminal tail, while LigIV uses its tandem BRCT repeats to bind the XRCC4 coiled-coil. Yet, the assembled PNKP-XRCC4–LigIV complex remains uncharacterized. Here, we report purification and characterization of a recombinant PNKP–XRCC4–LigIV complex. We show that the stable binding of PNKP in this complex requires XRCC4 phosphorylation and that only one PNKP protomer binds per XRCC4 dimer. Small angle X-ray scattering (SAXS) reveals a flexible multi-state complex that suggests that both the PNKP FHA and catalytic domains contact the XRCC4 coiled-coil and LigIV BRCT repeats. Hydrogen-deuterium exchange indicates protection of a surface on the PNKP phosphatase domain that may contact XRCC4–LigIV. A mutation on this surface (E326K) causes the hereditary neuro-developmental disorder, MCSZ. This mutation impairs PNKP recruitment to damaged DNA in human cells and provides a possible disease mechanism. Together, this work unveils multipoint contacts between PNKP and XRCC4–LigIV that regulate PNKP recruitment and activity within NHEJ.

Computation of wheel–rail contact force for non-mapping wheel–rail profile of Translohr tram

ABSTRACTTranslohr tram has steel wheels, in V-like arrangements, as guide wheels. These operate over the guide rails in inverted-V arrangements. However, the horizontal and vertical coordinates of the guide wheels and guide rails are not always mapped one-to-one. In this study, a simplified elastic method is proposed in order to calculate the contact points between the wheels and the rails. By transforming the coordinates, the non-mapping geometric relationship between wheel and rail is converted into a mapping relationship. Considering the Translohr tram’s multi-point contact between the guide wheel and the guide rail, the elastic-contact hypothesis take into account the existence of contact patches between the bodies, and the location of the contact points is calculated using a simplified elastic method. In order to speed up the calculation, a multi-dimensional contact table is generated, enabling the use of simulation for Translohr tram running on curvatures with different radii.

Soft Nanocomposite Based Multi-point, Multi-directional Strain Mapping Sensor Using Anisotropic Electrical Impedance Tomography

The practical utilization of soft nanocomposites as a strain mapping sensor in tactile sensors and artificial skins requires robustness for various contact conditions as well as low-cost fabrication process for large three dimensional surfaces. In this work, we propose a multi-point and multi-directional strain mapping sensor based on multiwall carbon nanotube (MWCNT)-silicone elastomer nanocomposites and anisotropic electrical impedance tomography (aEIT). Based on the anisotropic resistivity of the sensor, aEIT technique can reconstruct anisotropic resistivity distributions using electrodes around the sensor boundary. This strain mapping sensor successfully estimated stretch displacements (error of 0.54 ± 0.53 mm), surface normal forces (error of 0.61 ± 0.62 N), and multi-point contact locations (error of 1.88 ± 0.95 mm in 30 mm × 30 mm area for a planar shaped sensor and error of 4.80 ± 3.05 mm in 40 mm × 110 mm area for a three dimensional contoured sensor). In addition, the direction of lateral stretch was also identified by reconstructing anisotropic distributions of electrical resistivity. Finally, a soft human-machine interface device was demonstrated as a practical application of the developed sensor.

A simple and efficient numerical model for dynamic interaction of high speed train and railway structure including derailment during an earthquake

A simple and efficient numerical model to solve the dynamic interaction of a high-speed train and railway structure including derailment and post-derailment during an earthquake is given. Mechanical model to express contact-impact behaviours between wheel and rail before derailment and between wheel and track structure after derailment is discussed. A contact model based on multipoint contact springs on the contact surface between wheel and the track structure after derailment is given. An efficient contact element to express contact-impact behaviour between the car body of the train and the railway structure during and after derailment is also given where the contact stiffness is described as a nonlinear function of the contact displacement.The motion of the train with nonlinear springs and dampers is modelled in multibody dynamics. The railway structure is modelled with various finite elements. The modal reduction is applied to equations of motion of the train and railway structure. A robust time integration using the exact time integration has been developed in the modal coordinate to solve the radical dynamic interaction including derailment during an earthquake to avoid the round-off error which normally appears in the numerical time integration for very small time increments. Numerical example is demonstrated.

An analysis of the train–turnout interaction

A distinctive feature of the application proposed in this work is the occurrence of simultaneous contact patches on a single wheel, i.e., the multi-point contact case. A difficulty in the study of this phenomenon is that the contact areas depend on the deformation of the bodies, whereas these deformations are functions of the contact loading and the contact area. This is contrary to what is usually the case in finite element analysis, where the load and displacement are prescribed at different (fixed) parts of the boundary.

Numerical analysis of the effect of track parameters on the wear of turnout rails in high-speed railways

In this study, a numerical procedure is developed to predict the wear of turnout rails, and the effect of track parameters is investigated. The procedure includes simulation of the dynamic interaction between the train and the turnout, the rolling contact analysis, and the wear model. The dynamic interaction is simulated with the validated commercial software Simpack that uses a space-dependent model of a railway turnout. To reproduce the actual operating conditions of a railway turnout, stochastic variations in the input parameters are considered in the simulation of the dynamic interaction. The rolling contact is analyzed with the semi-Hertzian method and improved FASTSIM algorithm, which enable the contact model to deal with situations of multipoint contact and nonelliptic contact. Based on the Archard’s wear law, the wear model requires the calculation of normal/tangential stresses and a relative slide on the contact patches. The numerical procedure is performed for the selected sections of the vehicle, which runs through the railway turnout in the diverging route. By using the numerical procedure, the effect of track parameters (track gage, rail inclination, and friction coefficient) on the wear of turnout rails is analyzed. The results show that the wear of the front wheelset is more serious than the wear of the rear wheelset for a single vehicle. The degree of wear of switch rails is more severe than that of the stock rails and the difference is more obvious for the front wheelset of the switch rails. The wear of switch rails is mainly concentrated on the rail gage corner, while the wear of stock rails is mainly concentrated on the rail crown. For the analysed CN60-1100-1:18 turnout and the high-speed vehicle CRH2 in China, the rail wear rate could be slowed down by increasing the track gage and decreasing the rail inclination. Alternatively, the rail wear rate could be slowed by decreasing the friction coefficient; however, the variation of wear depth is quite small for friction coefficients that are larger than 0.3.

Multipoint contact modeling of nanoparticle manipulation on rough surface

In this paper, the atomic force microscopy (AFM)-based 2-D pushing of nano/microparticles investigated on rough substrate by assuming a multipoint contact model. First, a new contact model was extracted and presented based on the geometrical profiles of Rumpf, Rabinovich and George models and the contact mechanics theories of JKR and Schwartz, to model the adhesion forces and the deformations in the multipoint contact of rough surfaces. The geometry of a rough surface was defined by two main parameters of asperity height (size of roughness) and asperity wavelength (compactness of asperities distribution). Then, the dynamic behaviors of nano/microparticles with radiuses in range of 50–500 nm studied during their pushing on rough substrate with a hexagonal or square arrangement of asperities. Dynamic behavior of particles were simulated and compared by assuming multipoint and single-point contact schemes. The simulation results show that the assumption of multipoint contact has a considerable influence on determining the critical manipulation force. Additionally, the assumption of smooth surfaces or single-point contact leads to large error in the obtained results. According to the results of previous research, it anticipated that a particles with the radius less than about 550 nm start to slide on smooth substrate; but by using multipoint contact model, the predicted behavior changed, and particles with radii of smaller than 400 nm begin to slide on rough substrate for different height of asperities, at first.

A method for modelling contact between circular and non-circular shapes with variable radii of curvature and its application in planar mechanical systems

Contact impact has been widely found in the operation of various mechanical systems. These mechanical systems include the type of mechanism typically characterised by circular–non-circular geometric contact. They consist of the mechanisms of the cam with a roller follower, a Geneva wheel with intermittent motion, a cog belt drive with circular-arc teeth, a cycloidal-pin wheel gear, and a roller chain drive. For the two components in contact, one component needs to have an ideal circular shape, while the other is characterised by its non-circular geometry, that is, the contact shape may present varying radii of curvature. Taking this kind of contact mechanical system as a research object, this work proposes a general method for analysing the problems concerning contact impact on this circular–non-circular geometry. This method discretises continuous non-circular geometries to acquire a series of discrete points. Then, the contact areas of components are determined by repeatedly judging the relationships between the positions for various discrete points and the circular geometric centres thereof. In the contact areas, the maximum depth of the contact is measured, and the positions of the contact points between components, in a direction along the maximum contact depth, are determined. Finally, the normal contact force and tangential friction force between contacting components are established at the contact points. This method can be applied to analyse the problems concerning single contact and multi-point contact among various contact components. To verify the validity of this method, this work takes an offset translational roller follower disc cam mechanism (with a single contact) and a cycloidal-pin wheel gear mechanism (with multi-point contact) as examples and investigates the dynamic characteristics of the contact impact for the aforementioned mechanical systems, respectively.

Maximally dense random packings of intersecting spherocylinders with central symmetry

The packing of rod-like particles has arisen in a variety of scientific and industrial applications. For the factors that attribute to the packing properties of such particles, elongation effect is one of the most important. However, rod-like particles can be easily assembled into non-convex shapes, in which the effects of non-convex deformations should be concerned. In this paper, the dense random packings of identical intersecting spherocylinders with central symmetry are numerically simulated through an analytical model and the relaxation algorithm. The maximally dense random packing (MDRP) states of 2D and 3D intersecting spherocylinders with various aspect ratios are determined from the order maps. In the MDRP states, the specific volume V, defined as the reciprocal of the packing density ϕ, shows a highly linear correlation with the aspect ratio (w≥1.0), which is similar to the monophasic packing of spherocylinders. This indicates that the elongation effect is the main shape factor that attributes to the packing density. Consequently, the explicit formulas to predict the packing densities of 2D and 3D intersecting spherocylinders are built as single-variable functions of the aspect ratio. The dense random packing density of 2D intersecting spherocylinders equals to that of identical spherocylinders when w=1.25. This suggests that a balance exists between the relative excluded volume effect and the multi-point contact effect to the packing density of non-convex particles.

Dynamic modeling and contact analysis of a cycloid-pin gear mechanism with a turning arm cylindrical roller bearing

A method for analyzing the contact dynamics of the multi-tooth meshing in a cycloidal-pin gear transmission was proposed considering the influences of the turning-arm cylindrical roller bearing. The dynamic model of the cycloidal-pin gear transmission was established within the framework of the dynamic theory of multi-body system. As for the contact model of the multi-tooth meshing in the cycloidal-pin gear transmission, the tooth profile curve of the cycloid gear was dispersed as a series of points firstly. Then, by cyclically judging whether these points and each pin tooth meet the contact condition, the contact region, the maximum contact depth and the contact load were calculated in sequence. Additionally, the turning-arm cylindrical roller bearing with multi-point contact was modeled using a non-linear contact force system, with consideration of the influence of the bearing kinetic characteristics. The results show that the fluctuations in the kinematic response, the cycloidal-pin teeth contact forces and the bearing roller-raceway contact forces are mainly affected by the multi-tooth meshing characteristics of the cycloidal-pin wheel transmission system. The theoretical model and the analytical results were verified through numerical example and a virtual prototype simulation based on multi-body dynamics theory.

Mutual Forbearance and Competition Among Security Analysts

Research in industrial organization and strategic management has shown that rivals competing with each other in multiple markets are more willing to show each other mutual forbearance, i.e., compete less aggressively, within their spheres of influence, i.e., the markets in which each firm dominates. Sell-side equity analysts typically cover multiple stocks in common with their rivals. We examine the impact of this “multipoint contact” for mutual forbearance on two key dimensions of competition among security analysts: forecast accuracy and information leadership (issuing earnings forecasts or stock recommendations that influence rival analysts). We find that multipoint contact is associated with analysts exerting greater information leadership on stocks within their own spheres of influence. We also find greater forbearance related to information leadership under Regulation Fair Disclosure (Reg FD). In contrast, multipoint contact was not associated with greater forecast accuracy on stocks within analysts’ spheres of influence, either before or under Reg FD. Our analysis is among the first to consider mechanisms of competition among securities analysts and also adds to the literature on Reg FD by demonstrating that the increased workload imposed on analysts after Reg FD fostered mutual forbearance as a response. This paper was accepted by Mary Barth, accounting.

Experimentally Validated Combustion and Piston Fatigue Life Evaluation Procedures for the Bi-Fuel Engines, Using an Integral-Type Fatigue Criterion

A relatively complete procedure for high cycle fatigue life assessment of the engine components is outlined in the present paper. The piston is examined as a typical component of the engine. In this regard, combustion process and transient heat transfer simulations, determination of the instantaneous variations of the pressure and temperature in the combustion chamber, kinematic and dynamic analyses of the moving parts of the engine, thermoelastic stress analyses, and fatigue life analyses are accomplished. Results of the simulation are compared with the test data to verify the results. The heat transfer results are validated by the experimental results measured by the Templugs. The nonlinear multipoint contact constraints are modeled accurately. Results of the more accurate available fatigue criteria are compared with those of a fatigue criterion recently proposed by the first author. These results are also evaluated by comparing them with the experimental durability tests. The presented procedure may be used, e.g., to decide whether it is suitable to convert a gasoline-based engine to a bi-fuel one. Results of the various thermomechanical fatigue analyses performed reveal that the piston life decreases considerably when natural gas is used instead of gasoline.

Collision Avoidance Using Contact Information with Multiple Objects by Multi-Leg Robot

[abstFig src='/00280001/02.jpg' width=""300"" text='Optimized multi-point contacting walking' ]In robotics, a walking through motion is complex because of the presence of multipoint contact objects in the working environment of a robot. To simplify the walking through motion of a robot, a virtual impedance field is implemented to the contact points of the robot and an object so that the robot avoids the object passively. The traveling direction of the robot is altered by a virtual repulsive force obtained from the position of the estimated obstacle and the virtual impedance field. The resulting action depends on the parameter of virtual impedance coefficients. Because a combination of parameters includes many things, reinforcement learning is employed to obtain an optimal motion. The optimization of the multipoint contact walking through motion of a robot is finally achieved by evaluating the walking motion while encountering complex obstacles in a dynamic simulator. The motion is implemented on a hexapod robot, and the results demonstrate the effectiveness of the proposed method.

非伸縮分岐腱により把持形態が適応的に変化する3指ロボットハンドの開発

Human can pinch and grasp an object using his finger or fingertip with multiple contact points. The multiple-point contact increases stability while the object is grasped and controlled. We developed the anthropomorphic robotic finger with non-elastic branching tendon mechanism in order to realise the reaching motion with less actuators in our previous work. However, it was difficult to accomplish the grasping with multipoint contact. Thus, we develop a new robot hand system equipped branching tendons which realizes multiple-point contact while it grasps the object using with the whole fingers or finger-tips. In this paper, we introduce the developed robotic hand and show the reason why the robotic hand can realize the multiple-point contact.

Rivalry Deterrence and Performance in Multimarket Competition: Host Country Contingency Effects

Empirical results have shown that multipoint contact diminishes interfirm competition, based on mutual forbearance hypothesis. However, multinational corporations (MNCs) often face the pressure of ...

A Constitutive Model of Metal Rubber for Hysteresis Characteristics Based on a Meso-Mechanical Method

Based on the typical mesoscopic structural characteristics of metal rubber, the mesoscopic physical mechanism was revealed through analyzing the spatial configuration and the contact mode of wire helixes for its compression deformation process. The mesoscopic structure unit based on the curved beam of variable length and the model of the contact interaction between curved beams were proposed. Combined with the distribution law of frictional contact points, a new constitutive model of metal rubber for hysteresis characteristics was established, which included its basic structure parameters such as the diameter and the elastic modulus of wire, the diameter of wire helix, and the relative density of metal rubber. The model could describe the restoring force curves of metal rubber in initial loading, unloading and repeated loading phases, and theoretically explained its elastic characteristics and dry friction damping characteristics of multipoint contact. To verify the theory model, a comparison was made between the theoretical results and the experimental results for metal rubber specimens with different relative densities. The results show that theoretic calculations are consistent with the experimental data, which will provides a theoretical basis for predicting the stiffness and damping of metal rubber and guiding its design.

The influence of incident angle on physical properties of a novel back contact prepared by oblique angle deposition

In this paper, oblique vacuum thermal evaporation and direct current (DC) magnetron sputtering technique are used to produce a novel back contact electrode (BCE) of CuInS2 solar cell. These novel back contact electrodes (BCEs) are based on a layered structure of Mo/Ag/Mo (MAM). The influence of vapor source incidence angle θ on optical-electrical properties of novel BCE is investigated by X-ray Diffraction (XRD), Surface Profiler, Atomic Force Microscope (AFM), UV-vis-IR Spectrometer, and Four-point Probe Method. According to the analysis of AFM images of BCEs, the variation tendencies of surface roughness and uniformity are closely related to the incidence angle θ. The surface roughness increases with the increase of incidence angle θ, but the uniformity becomes poor at same time. This phenomenon can be attributed to the variation of interlayer Ag films (the density and inclined angle of Ag nanorods). The results of four-point probe test show that the novel BCE deposited by vapor source incidence angle θ equal to 45° owns the lowest resistance value of 3.71×10−8Ωm, which is probably due to a loose and multi-point contact interface between Ag layer and top layer (Mo2). The reflectance of novel BCEs deposited by incident angle less than 45° is higher than that of normal bi-layer Mo (Mo12) BCE. As a result, the efficiency of corresponding solar cell may be upgraded.

Origin of Stereodivergence in Cooperative Asymmetric Catalysis with Simultaneous Involvement of Two Chiral Catalysts.

Accomplishing high diastereo- and enantioselectivities simultaneously is a persistent challenge in asymmetric catalysis. The use of two chiral catalysts in one-pot conditions might offer new avenues to this end. Chirality transfer from a catalyst to product gets increasingly complex due to potential chiral match-mismatch issues. The origin of high enantio- and diastereoselectivities in the reaction between a racemic aldehyde and an allyl alcohol, catalyzed by using axially chiral iridium phosphoramidites PR/S-Ir and cinchona amine is established through transition-state modeling. The multipoint contact analysis of the stereocontrolling transition state revealed how the stereodivergence could be achieved by inverting the configuration of the chiral catalysts that are involved in the activation of the reacting partners. While the enantiocontrol is identified as being decided in the generation of PR/S-Ir-π-allyl intermediate from the allyl alcohol, the diastereocontrol arises due to the differential stabilizations in the C-C bond formation transition states. The analysis of the weak interactions in the transition states responsible for chiral induction revealed that the geometric disposition of the quinoline ring at the C8 chiral carbon of cinchona-enamine plays an anchoring role. The quinolone ring is noted as participating in a π-stacking interaction with the phenyl ring of the Ir-π-allyl moiety in the case of PR with the (8R,9R)-cinchona catalyst combination, whereas a series of C-H···π interactions is identified as vital to the relative stabilization of the stereocontrolling transition states when PR is used with (8S,9S)-cinchona.

A large LNG tank technology system “CGTank®” of CNOOC and its engineering application

LNG tanks are complex in design and building process and high in costs, so LNG tank technology is one of the most advanced ones in the field of energy, which has been monopolized by foreign companies for a long time. In order to work out LNG tank technology domestically, China National Offshore Oil Corporation (CNOOC for short), the largest LNG importer in China, develops a LNG tank technology system “CGTank®” successfully in reference to the design and construction experience of domestic and foreign companies, after years of scientific research in tackling difficult problems. This system presents four traits as follows. First, a set of calculation software is developed independently by CNOOC, and the tanks in all operating conditions are calculated after 3D hologram and multi-point contact model of fluid-solid coupling effect is built up. Second, earthquake effect research and inner tank check research are improved innovatively by means of response spectrum analysis after European standards are introduced. Third, it is put forward for the first time that the stress strength discrimination standard is based on the principal stress which is obtained by means of the maximum shearing failure theory. And fourth, a large LNG full-capacity tank technology package with completely independent intellectual property right is established. The “CGTank®” system was first applied in the Tianjin LNG demonstration project, which has passed all indicator tests and is now in operation smoothly. The project is provided with the core tank design technology by CNOOC Gas and Power Group and with the EPC by CNOOC Engineering Co., Ltd. The independent LNG tank technology can be applied in a wide scope and it is favorable for impelling domestic production of LNG industry completely.