Reconstruction of the Dynamic Rail-Wheel Contact Forces

2003 ◽  
Author(s):  
Svenja Kirchenkamp ◽  
Dirk So¨ffker
Keyword(s):  
Contact Force ◽  
Normal Force ◽  
Elastic Beam ◽  
Contact Forces ◽  
Force Estimation ◽  
Measurement Device ◽  
Tangential Contact ◽  
Proportional Integral ◽  
First Time ◽  
Displacement Measurements

This contribution introduces a virtual measurement device for the reconstruction of the in practice unmeasureable railwheel contact forces. For this aim the Proportional-Integral (PI)-Observer is used. Then, the concept of a measurement sleeve at the axle bearing is shown. With the displacement measurements resulting from the sleeve using the PI-Observer, an estimation of the tangential contact force and the dynamic normal force is possible. Using the simulation of the rail-wheel contact, the feasibility of the estimation of the contact force behavior is shown. As an outlook for further applications of the PI-Observer in the context of rail-wheel contact force estimation, the reconstruction of contact forces by using acceleration measurements is demonstrated by an example of an elastic beam for the first time.

Contact Force Estimation for an Elastic Beam Using Optimal High-Gain Disturbance Observer

2010 ◽  
Author(s):  
Yan Liu ◽  
Dirk So¨ffker
Keyword(s):  
Contact Force ◽  
Disturbance Observer ◽  
Elastic Beam ◽  
High Gain ◽  
Contact Forces ◽  
Force Estimation ◽  
Input Estimation ◽  
System States ◽  
Unknown Input Estimation ◽  
Noisy Measurements

This contribution presents a contact force estimation approach based on an optimal high-gain disturbance observer for an elastic beam using noisy measurements. The reconstruction of contact forces as an example for unknown input estimation represents a class of typical mechanical engineering problems related to the estimation of unknown effects for disturbance rejection or accommodation or fault diagnosis and isolation. The high-gain disturbance observers applied here is able to estimate estimate unknown external inputs together with system states. But choosing observer gains is a difficult task because of the influence of measurement noise. The important advantage of the proposed approach in comparison with classical high-gain disturbance observer is the self adjustment of the observer gains according to the actual estimation situation. Estimation results based on real measurements from known high-gain disturbance observer and the proposed optimal one are compared. It can be shown that the proposed algorithm allows optimized disturbance observer gains calculation, being able to be situatively adapted.

Contact Force Distribution and Induced Anisotropy in Granular Materials under Biaxial Test

2012 ◽  
Vol 446-449 ◽  
pp. 1927-1934
Author(s):  
Min Yun Hu ◽  
Qiao Hao Chen ◽  
Ying Shen ◽  
Xiao Wu Tang
Keyword(s):  
Contact Force ◽  
Normal Force ◽  
Microscopic Analysis ◽  
Contact Forces ◽  
Force Chain ◽  
Particle Flow Code ◽  
Biaxial Compression ◽  
Biaxial Test ◽  
Induced Anisotropy ◽  
Structural Anisotropy

A 2-dimensional granular assembly, subjected to isotropic consolidation and biaxial compression, is simulated by applying discrete element method and the particle flow code of PFC2D. The contact force network and distribution are examined and compared to an analogous photoelastic experiment carried out by other studies. The current study shows that the assembly undergoes dilatation and strain-softening after peak strength, and the coordination number (average contact number of particles) increases a little in the initial stage of strain hardening followed by a sharp dropping before the onset of softening. This is correlated with the contact force chain establishment and the evolution of structural anisotropy. The distribution of the normal force and the ratio of tangential to normal force for both the isotropically compressed and sheared stages indicates that the strong normal contacts are crucial for the force chain transmitting stress through assembly. The angular distribution of the contact forces supported this point and could help visualizing the induced anisotropy. These issues are vital for gaining a deeper understanding of the macroscopic behavior of granular material from microscopic analysis.

Robust contact force estimation for robot manipulators in three-dimensional space

2006 ◽  
Vol 220 (9) ◽  
pp. 1317-1327 ◽  
Author(s):  
J Jung ◽  
J Lee ◽  
K Huh
Keyword(s):  
Contact Force ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Contact Forces ◽  
Robust Estimator ◽  
Force Sensors ◽  
Force Estimation ◽  
Estimation Algorithms

Information on contact forces in robot manipulators is indispensable for fast and accurate force control. Instead of expensive force sensors, estimation algorithms for contact forces have been widely developed. However, it is not easy to obtain the accurate values due to uncertainties. In this article, a new robust estimator is proposed to estimate three-dimensional contact forces acting on a three-link robot manipulator. The estimator is based on the extended Kalman filter (EKF) structure combined with a Lyapunov-based adaptation law for estimating the contact force. In contrast to the conventional EKF the new estimator is designed such that it is robust to the deterministic uncertainties such as the modelling error and the sensing bias. The performance of the proposed estimator is evaluated through simulations of a robot manipulator and demonstrates robustness in estimating the contact force. The estimation results show that it can be potentially used to replace the expensive force sensors in robot applications.

Shape Optimal Design of Contact Springs of Electronic Connectors

2002 ◽  
Vol 124 (3) ◽  
pp. 178-183 ◽  
Author(s):  
Yeh-Liang Hsu ◽  
Yuan-Chan Hsu ◽  
Ming-Sho Hsu
Keyword(s):  
Contact Force ◽  
Printed Circuit Boards ◽  
Normal Force ◽  
Optimization Techniques ◽  
Contact Forces ◽  
Design Parameters ◽  
Original Design ◽  
Insertion Force ◽  
Element Analysis ◽  
Normal Contact

An electronic connector provides a separable interface between two subsystems of an electronic system. The contact spring is probably the most critical component in an electronic connector. Mechanically, the contact spring provides the contact normal force, which establishes the contact interface as the connector is mated. However, connector manufacturers have a basic struggle between the need for high normal contact forces and low insertion forces. Designing connectors with large numbers of pins that are used with today’s integrated circuits and printed circuit boards often results in an associated rise in connector insertion force. It is possible to lower the insertion force of a connector by redesigning the geometry of the contact spring, but this also means a decrease in contact normal force. In this paper, structural shape optimization techniques are used to find the optimal shape of the contact springs of an electronic connector. The process of the insertion of a PCB into the contact springs of a connector is modeled by finite element analysis. The maximum insertion force and the contact normal force are calculated. The effects of several design parameters are discussed. The geometry of the contact springs is then parameterized and optimized. The required insertion force is minimized while the normal contact force and the resulting stress are maintained within specified values. In our example, the insertion force of the final contact spring design is reduced to 68.3% of that of the original design, while the contact force and the maximum stress are maintained within specified values.

scholarly journals Closed-Form Equations for Contact Force and Moment in Elastic Contact of Rough Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Closed Form ◽  
Half Plane ◽  
Contact Force ◽  
Normal Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Compressive Load ◽  
Angular Misalignment ◽  
Tangential Contact ◽  
Applied Forces

It is reasonable to expect that, when two nominally flat rough surfaces are brought into contact by an applied resultant force, they must support, in addition to the compressive load, an induced moment. The existence of a net applied moment would imply noneven distribution of contact force so that there are more asperities in contact over one region of the nominal area. In this paper, we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment, and thereby contact moment is derived. Through this scheme, it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force, however, is shown to be of a much smaller order than the contact normal force. Approximate closed-form equations are found for contact force and moment for the contact of rough surfaces.

scholarly journals Stator-Rotor Contact Force Estimation of Rotating Machine

Automation ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 83-97
Author(s):  
Mark Spiller ◽  
Dirk Söffker
Keyword(s):  
Contact Force ◽  
Dry Friction ◽  
Nonlinear Filtering ◽  
Friction Model ◽  
Contact Forces ◽  
Elastic Behavior ◽  
Force Estimation ◽  
Severe Problem ◽  
Suggested Approach ◽  
System States

In turbomachines, dry friction resulting from stator–rotor contacts is a severe problem that may degrade lifetime of the machine or even lead to complete failure. Knowledge about the system states and contact forces is beneficial for system monitoring or to prevent contacts through, e.g., active magnetic bearings. In this paper, a nonlinear model is derived that describes the lateral rotor vibrations in the case of contact and no contact. The elastic behavior of the shaft is modeled based on the finite-element method. The contact is described by a dry friction model. An augmented system description is formulated that allows estimation of rotor displacements and contact forces by means of nonlinear filtering approaches like an extended Kalman filter. A simulation study was conducted that explicitly considered the hazardous backward whirl. The suggested approach shows suitable estimation performance related to both state and contact force estimation.

Evaluation of Friction Damping in Dovetail Root Joints Based on Dissipation Energy on Contact Surfaces

2009 ◽  
Author(s):  
Kunio Asai ◽  
Shigeo Sakurai ◽  
Takeshi Kudo ◽  
Norihiko Ozawa ◽  
Taizo Ikeda
Keyword(s):  
Contact Force ◽  
Contact Stiffness ◽  
Relative Displacement ◽  
Contact Angles ◽  
Forced Response ◽  
Contact Forces ◽  
Friction Damping ◽  
Normal Contact ◽  
Tangential Contact ◽  
Contact Surfaces

It is necessary to increase and estimate friction damping at contact interfaces to reduce vibratory stresses in turbines. The hysteresis behavior between tangential contact force and relative displacement should be precisely estimated to improve the accuracy of fiction-damping estimates. There is a difficulty in establishing a general model of hysteresis because tangential contact stiffness depends on many parameters, such as normal contact force, contact geometry, surface roughness, and wear status. We discuss a procedure to empirically calculate friction damping in dovetail root joints using the tangential contact stiffness estimated from measured natural frequencies and the micro-slip model whose coefficients were experimentally obtained from special fretting tests. Instead of the multi-harmonic balance methods, we calculated the friction damping on the basis of the energy dissipation at contact surfaces to discuss the effects of the tangential contact stiffness on several physical values, i.e., tangential and normal contact forces, natural frequency, and micro-slip. In our model, the linear forced response analysis was conducted by taking into consideration the non-linearity between the tangential contact force and the relative displacement by defining the actual and imaginary tangential contact stiffness. We confirmed that the numerically calculated damping ratios are quantitatively in very good agreement with the measured ones under different contact angles, input gravity levels, and contact forces. This indicates that if the tangential contact stiffness is accurately estimated, friction damping with our method can be precisely estimated under different test conditions. We also showed that the estimated tangential contact stiffness for dovetail root joints are smaller than those obtained by the fretting tests at high input gravity. This is probably because the contact interface partially separates during a cyclic loading in the former case; this results in the decrease of the contact area and contact stiffness.

Contact Moment and Friction Force in Elastic Contact of Two Rough Surfaces

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Friction Force ◽  
Half Plane ◽  
Contact Force ◽  
Normal Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Compressive Load ◽  
Angular Misalignment ◽  
Tangential Contact ◽  
Applied Forces

It is reasonable to expect that when two nominally flat rough surfaces are brought into contact by an applied resultant force, they must support, in addition to the compressive load, an induced moment. The existence of a net applied moment would imply non-even distribution of contact force so that there are more asperities in contact over one region of the nominal area. In this paper we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment and through this contact moment is derived. Through this scheme it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force however is shown to be of a much smaller order than the contact normal force.

Nonintrusive Measurement of Contact Forces During Vibration Dominated Impacts

2004 ◽  
Vol 126 (3) ◽  
pp. 489-497 ◽  
Author(s):  
Satwinder Jit Singh ◽  
Anindya Chatterjee
Keyword(s):  
Contact Force ◽  
Tikhonov Regularization ◽  
Strain Gauge ◽  
Initial Conditions ◽  
Contact Point ◽  
Electrical Contact ◽  
Contact Forces ◽  
Force Estimation ◽  
Contact Duration ◽  
Gauge Data

Impact force estimation is done indirectly through, e.g., strain measurements away from the contact point, because inserting a force transducer between the contacting objects changes the force. Most prior contact force measurements involved a single contact interval. Here we study transverse impacts of a slender beam and a clamped-free plate; contact occurs more than once within one impact. Strain gauge data, electrical contact detection, and a dynamic model of the beam are used to estimate the contact force. The problem of force estimation from strain gauge data is ill-posed, and Tikhonov regularization fails initially. A reduced-order model is then developed using symmetry, and better initial conditions are estimated using a Kalman filter. Subsequently, Tikhonov regularization gives excellent force estimates, empirically supported by the contact duration measurements. Two other methods that explicitly use the contact duration measurements are also given. The first uses Tikhonov regularization within each contact interval, followed by Kalman filtering during noncontact to get initial conditions for the next contact. The second uses truncated Fourier sine series in each contact interval and is, computationally, the simplest. All three methods provide consistent force estimates. Our work complements recent work by Inoue and coworkers where the impulse response of the colliding object was measured separately using a Hopkinson bar, and electrical contact was not monitored.

Contact of Rough Surfaces: Combined Elastic and Rate-Dependent Effects

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Half Plane ◽  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Approximation Error ◽  
Tangential Velocity ◽  
Contact Forces ◽  
Tangential Contact ◽  
Force Components ◽  
Approximate Equations

Approximate closed form equations are found for normal and tangential contact forces of rough surfaces in dry friction. Using a viscoelastic asperity behavior, mathematical formulae are derived for normal and tangential components of the contact force that depend not only on the separation of the two surfaces but also the rate of approach and relative sliding. The tangential force over a half-plane, corresponding to the moving direction, is found accounting for the directionality of the tangential component of asperity forces. A statistical approach is forwarded in which dependence of the asperity normal and tangential contact force on relative tangential velocity of two asperities can presented as corrective factors in the mathematical description of normal and tangential force components. These are force directionality corrective coefficient and force-velocity directionality corrective coefficient. Two sets of approximate equations are found for each of the normal and half-plane tangential force components. The simplest forms of the approximate equations achieve accuracy to within five (5) percent error, while other forms yield approximation error within 0.2 percent.

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