Friction Force Model Research Articles

햅틱 복강경 수술 시뮬레이터의 마찰력 및 중력 보상

Laparoscopic surgery is being used in various surgical fields because it minimizes scarring. Laparoscopic operations require practical hand skills, so surgeons train on animals and via surgery training tool sets. However, these tool sets do not give the surgeon the sensation of touching real organs. A recently developed laparoscope simulator has a high friction force along the translational axis and a high gravity force along the pitch axis, and therefore it does not permit the operator to control his or her hands delecately. In the paper, the friction force along the axes is auumed to depend on the veolcity, and the gravity force on the angle and distance. We develop a compensation model that combines the gravity and friction force models.

Stick-slip algorithm in a tangential contact force model for multi-body system dynamics

Contact force of Multi-body dynamics (MBD) system can be classified two parts. First is a normal force and the other is a tangential force called friction force. And the friction force can be represented by two states such as stick and slip. The stick-slip phenomenon is simply described as a simple contact model which is a rigid body contacted on a sloped surface. If the calculated friction coefficient between the body and sloped surface is less than the static friction coefficient, the body should be stuck. If the calculated friction coefficient is greater than the static friction coefficient, the body will be sliding along the surface. The phenomenon is called as stick and slip state of friction, respectively. Usually many researchers and commercial MBD software used a coulomb friction force model which is defined with an only function of relative velocity. This kind of friction force model will be called a conventional friction force model in this paper. A big problem of the conventional model can not describe a stick state of friction phenomenon. In the case of conventional friction force model, the body will be sliding even though friction state is stick. Because, the relative velocity must have a non-zero value in order to generate the friction force. To solve this kind of problem, we propose a stick-slip friction force model including a spring like force. In the case of stick-slip friction force model, the body can be stuck on the sloped surface because the friction force will be a non-zero value, even though the relative velocity approaches zero. We defined a relative displacement variable called stiction deformation. In this paper, the stick-slip friction model is proposed and applied in the contact algorithm of MBD system. And then two friction models are compared with numerical examples. With the proposed stick-slip friction model, more realistic results are achieved.

Vibration Isolation with Semi-Active Friction Damping

This study explores the effect of semi-active friction damping on vibration isolation systems by means of numerical simulation. Since the Lugre friction model can describe many phenomena observed in laboratories, it is chosen to provide accurate friction force model for the analysis and simulations. The drawback of the passive friction damping system is that it decreases the resonance response at the cost of worsening the performance for high frequencies. A semi-active control method (skyhook method) is used to tune the normal force so that the energy dissipated by the friction force is maximized. Such semi-active friction damping system is simple but efficient, and it can achieve result almost as good as that of active systems. Results from numerical simulations show that compared with passive system, semi-active control method decreases the response significantly for both low and high frequencies, with harmonic and random excitations.

ICONE19-43287 TWO-PHASE WALL AND INTERFACIAL FRICTION FORCES FOR ANNULAR FLOWS IN A 2X1 RODS CHANNEL SIMPLIFYING BWR

Most of recent subchannel analysis codes are based on a multi-fluid model, and accurate evaluation of the constitutive equations in the model is essential. In order to get accurate ones of the wall and the interfacial friction forces and validate them, experimental data on these forces have been obtained from the pressure drop and the void fraction data for air-water annular flows in 2×1 rods channel simplifying a BWR fuel rod bundle geometry. In order to know the effects of liquid properties on the data, water temperature was changed from 18 to 50℃. The wall and interfacial friction forces data determined are compared with the existing correlations reported in literatures. As a result, correlations of NASCA code and RELAP5/MOD2 code, and homogeneous flow model with McAdams' viscosity model for the wall friction force, and Fukano and Furukawa's correlation for the interfacial friction force show the best prediction against the present data.

Study on Friction Force Distribution on Silicon Wafer Surface in CMP Process

The friction force on wafer surface plays an important role in removing material of wafer surface and the friction force on wafer surface may have a direct influence on non-uniformity of material removal in wafer CMP process. In this paper, models of friction force on wafer surface were built according to the CMP process. It is proved that the model of the friction force on the wafer surface is correct by the silicon wafer CMP Friction experiment. Then the data fitting of friction model has been done with the experimental data. By the friction force model, the within wafer nonuniformity (WIWNU) of friction force distribution on wafer surface has been obtained with different rotational speed of wafer and polishing pad. The research of this paper is helpful to further understanding the material removal mechanism in wafer CMP.

Erratum to: “Friction-Force Model for a Ball with Predisplacement of Rolling on a Rough Surface”

Erratum to: “Friction-Force Model for a Ball with Predisplacement of Rolling on a Rough Surface”

Modeling of directional friction on a fully lubricated surface with regular anisotropic asperities

The modern surface technology now promises to fabricate surfaces with regular asperities. The regular asperity means that asperities, which are related to surface roughness in a conventional tribology, have similar shape and size, and their distribution over the surface is controllable. The regular asperity surface technology may have transformative impact to contemporary tribology. In this paper, we present a study of friction on the surface with regular anisotropic asperities (RAA) in a fully lubrication status. By anisotropic asperity, it is meant that the geometry of the asperity presents different to different motion directions, which is further speculated to have different friction behaviors along different motion directions. The primary goal of the study was to develop a model of friction force on the RAA surface in a fully lubrication status. The secondary goal was to exhibit the directional friction behavior based on our model. We employed Computational Fluid Dynamics (CFD) software to assist in the modeling and used the published data in the literature to validate our model. As a result, accuracy of our model was shown much better than that of the model reported in the current literature. With our model, we successfully demonstrated several interesting directional friction behaviors on the fully lubricated RAA surface.

Friction-force model for a ball with predisplacement of rolling on a rough surface

Friction-force model for a ball with predisplacement of rolling on a rough surface

ACTIVE CONTROL OF ROLLING MANOEUVRES OF A ROBOTIC FINGER WITH HEMISPHERICAL TIP

In this paper we are concerned with the problem of sensory motor coordination of a robotic finger in order to evoke rolling maneuvers in a force-positioning task on a flat rigid surface. We use two different approaches to modeling the reaction of the soft fingertip with the contacted surface. Firstly, we assume that the environment imposes a purely kinematic rolling constraint on the end-effector motion in the tangent direction of the contacted surface. This implies no energy transfer or dissipation between the fingertip and the environment due to frictional forces. On the other hand, we assume that it is feasible for the fingertip to slip in which case pure rolling motion could be disturbed. The two different models are subsequently used to show by simulation that control laws, which have been designed on a rolling constraint dynamic model for frictional forces, fail to perform rolling in various environments. An extra control input that uses a reference rolling trajectory that is state dependent is proposed, which, if superimposed on a conventional force-position control law, can achieve rolling even on a surface with low friction characteristics. The proposed feedback signal does not utilize the modeling information in the control formulation, and thus permits easy implementation. Finally, the total controller is shown to achieve asymptotic convergence to the desired force-positioning task by simultaneously evoking pure rolling motion for the fingertip.

Modified Burridge–Knopoff model with state dependent friction

A modified version of the Burridge–Knopoff model including a simple model for state dependent friction force was derived. The friction model describes a velocity weakening of friction between moving blocks and an increase of static friction during stick periods. It provides a simplified but qualitatively correct stability diagram for the transition from smooth sliding to stick-slip behavior as observed in various tribological systems. Attractor properties of the model dynamic equations were studied under a broad range of parameters for 1- and 2-dimensional systems.

Teleoperated 3-D Force Feedback From the Nanoscale With an Atomic Force Microscope

In this study, 3-D experimental teleoperated force feedback during contact with nanoscale surfaces is demonstrated using an atomic force microscope (AFM) on the slave side and a haptic device on the master side. To achieve 3-D force feedback, coupling between one of the horizontal forces and the vertical force is a crucial bottleneck. To solve this coupling issue, a novel force decoupling algorithm is proposed. This algorithm uses local surface slopes, an empirical friction force model, and the haptic device motion angle projected onto the surface to estimate the friction value during experiments. With this estimation, it is possible to decouple the three orthogonal forces acting on the tip of the AFM cantilever. Moreover, using an adaptive observer, parameters of the friction model can be changed online, removing the necessity to calibrate the friction model initially. Finally, a modified passivity-based bilateral control is used to reflect the scaled nanoscale forces to the master side and the operator. The performance of the system is demonstrated on experimental results for flat and non-flat, and hard and soft surfaces.

A New Modeling Method for Mechanical Friction Based on Data Mining

Modeling of friction force has been a challenging task in mechanical engineering. Traditional way, such as mathematical modeling approaches, was found quite difficult to achieve satisfactory performances due to some immanent nonlinearity and uncertainties in systems. This paper aims to develop fuzzy modeling techniques to characterize the friction dynamics. The proposed fuzzy modeling approach has two folds, that is, extraction of fuzzy rules using data mining techniques; setup of static model based on the fuzzy rules. The results obtained demonstrate that our proposed method in this paper has good potential in many mechanical systems with unknown nonlinear friction.

A comparative study on the control of friction-driven oscillations by time-delayed feedback

We perform a detailed study of two linear time-delayed feedback laws for control of friction-driven oscillations. Our comparative study also includes two different mathematical models for the nonlinear dependence of frictional forces on sliding speed. Linear analysis gives stability boundaries in the plane of control parameters. The equilibrium loses stability via a Hopf bifurcation. Dynamics near the bifurcation is studied using the method of multiple scales (MMS). The bifurcation is supercritical for one frictional force model and subcritical for the other, pointing to complications in the true nature of the bifurcation for friction-driven oscillations. The MMS results match very well with numerical solutions. Our analysis suggests that one form of the control force outperforms the other by many reasonable measures of control effectiveness.

Finite-temperature vortex dynamics in Bose-Einstein condensates

We study the decay of vortices in Bose-Einstein condensates at finite temperatures by means of the Zaremba Nikuni Griffin formalism, in which the condensate is modelled by a Gross Pitaevskiiequation, which is coupled to a Boltzmann kinetic equation for the thermal cloud. At finite temperature, an off-centred vortex in a harmonically trapped pancake shaped condensate decays by spiralling out towards the edge of the condensate. This decay, which depends heavily on temperature and atomic collisions, agrees with that predicted by the Hall Vinen phenomenological model of friction force, which is used to describe quantised vorticity in superfluid systems. Our result thus clarifies the microscopic origin of the friction and provides an ab initio determination of its value.

Effect of Friction on the Performance of an Octostrut Vibration Isolation Platform

To improve the dynamic environment of a spacecraft, an octostrut vibration isolation platform is designed to replace the payload attach fitting, which can significantly attenuate the vibration transmitted to payload except that an extra isolation frequency is introduced. However, it is found from the experimental results that when the excitation amplitude is lower than a certain level, the first resonance occurs at a higher frequency (i.e., the isolation frequency). This is caused by the nonlinearity that is a result of the friction existing in every actuator. Therefore, in this paper, the friction force of the single actuator is taken into account and is described by a bilinear hysteresis model. With this friction force model, a new nonlinear model of the octostrut vibration isolation platform is established. Meanwhile, the harmonic balance method is used to solve the nonlinear equations. The theoretical and experimental results indicate that the friction plays an important role in the performance of the platform. It is identified from the study that to ensure the performance of an isolator, in its design, either the maximum friction force or the minimum excitation should be restricted.

Friction Force Measurements and Modeling in Hard Disk Drives

Friction in a head disk interface (HDI) is investigated considering the surface energy of the lubricant and the type of carbon overcoat (COC). Perfluoropolyether Z-Tetraol lubricant with A20H additive is applied on two types of COC (type-A and type-B) with lubricant thicknesses in the range of 11-19 A. The polar and dispersive components of the surface energy are measured from contact angle experiments. For each case, friction is measured using actual hard disk drives, and they are compared with the measured surface energy values of the disk samples. As the lubricant thickness increases, both the surface energy and friction decrease. Comparing friction and surface energy values for the two types of COC disks, type-A disks are found to exhibit lower surface energy and higher friction at all lubricant thicknesses. This is attributed to the effects of surface roughness, surface energy of the COC film, and lubricant interactions.

Translational Joints With Clearance in Rigid Multibody Systems

A computational methodology for dynamic description of rigid multibody systems with translational clearance joints is presented and discussed in this work. Over the past years, extensive work has been done to study the dynamic effect of the revolute joints with clearance in multibody systems, in contrast with the little work devoted to model translational joints with clearance. In a joint with translation clearance, there are many possible ways to set the physical configuration between the slider and guide, namely: (i) no contact between the two elements, (ii) one corner of the slider in contact with the guide surface, (iii) two adjacent slider corners in contact with the guide surface, and (iv) two opposite slider corners in contact with the guide surfaces. The proposed methodology takes into account these four different situations. The conditions for switching from one case to another depend on the system dynamics configuration. The existence of a clearance in a translational joint removes two kinematic constraints from a planar system and introduces two extra degrees of freedom in the system. Thus, a translational clearance joint does not constrain any degree of freedom of the mechanical system but it imposes some restrictions on the slider motion inside the guide limits. When the slider reaches the guide surfaces, an impact occurs and the dynamic response of the joint is modeled by contact-impact forces. These forces are evaluated here with continuous contact force law together with a dissipative friction force model. The contact-impact forces are introduced into the system’s equations of motion as external generalized forces. The proposed methodology is applied to a planar multibody mechanical system with a translational clearance joint in order to demonstrate its features.

Existence and analytical predictions of periodic motions in a periodically forced, nonlinear friction oscillator

The grazing bifurcation, stick phenomena and periodic motions in a periodically forced, nonlinear friction oscillator are investigated. The nonlinear friction force is approximated by a piecewise linear, kinetic friction model with the static force. The total forces for the input and output flows to the separation boundary are introduced, and the force criteria for the onset and vanishing of stick motions are developed through such input and output flow forces. The periodic motions of such an oscillator are predicted analytically through the corresponding mapping structure. Illustrations of the periodic motions in such a piecewise friction model are given for a better understanding of the stick motion with the static friction. The force responses are presented, which agreed very well with the force criteria. If the fully nonlinear friction force is modeled by several portions of piecewise linear functions, the periodically forced, nonlinear friction oscillator can be predicted more accurately. However, for the fully nonlinear friction force model, only the numerical investigation can be carried out.

Simulation of two-phase flows in vertical tubes with the CTFD code FLUBOX

The computational two-fluid dynamics (CTFD) code FLUBOX is developed at GRS for the multidimensional simulation of two-phase flows. The single-pressure two-fluid model is used as basis of the simulation. A basic mathematical property of the two-fluid model of FLUBOX is the hyperbolic character of the advection. The numerical solution methods of FLUBOX make explicit use of the hyperbolic structure of the coefficient matrices. The simulation of two-phase flow phenomena needs, apart from the conservation equations for each phase, an additional transport equation for the interfacial area concentration. The concentration of the interfacial area is one of the key parameters for the modeling of interfacial friction forces and interfacial transfer terms. A new transport equation for the interfacial area concentration is in development. It describes the dynamic change of the interfacial area concentration due to mass exchange and a force balance at the phase boundary. Results from FLUBOX calculations for different experiments of two-phase flows in vertical tubes are presented as part of the validation.

Multibody dynamics simulation of planar linkages with Dahl friction

It is well-known that classical Coulomb dry friction model does not portrays important physical phenomena occurring in the contact between mating surfaces. Moreover, the discontinuity of force at zero velocity has many drawbacks during numerical simulations. In the attempt of exploring alternatives to Coulomb friction model, this paper presents the application of the Dahl friction model in a multibody dynamics formulation. The analysis herein presented includes also the modeling of friction forces in lower pairs and some hints on the efficient computation of Lagrange parameters during the fixed-point iteration process. Two numerical examples are offered.