Dynamic Contact Model Research Articles

Investigation on Dynamic Responses of Manipulator with Multiple Clearance Joints

The existence of clearance in joints of manipulator system is inevitable and the movements of the real manipulator are deflection from the ideal manipulator for the clearances. In this study, the effects of clearance on dynamic responses of real manipulator system with multiple clearance joints are investigated using a computational methodology. By applying the nonlinear continuous contact force model, the contact dynamics model in joint clearance is established and the friction effect is considered with the help of Coulomb friction model. Then the dynamics simulation is carried out and the dynamic characteristics of manipulator system with multiple clearance joints are investigated. The results show that the clearance leads to degradation of dynamic performance of the real manipulator system.

Transient response model of standing wave piezoelectric linear ultrasonic motor

A transient response model for describing the starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor was presented. Based on the contact dynamic model, the kinetic equation of the motor was derived. The starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor according to different loads, contact stiffness and inertia mass were described and analyzed, respectively. To validate the transient response model, a standing wave piezoelectric linear ultrasonic motor based on in-plane modes was used to carry out the simulation and experimental study. The corresponding results showed that the simulation of the motor performances based on the proposed model agreed well with the experimental results. This model will helpful to improve the stepping characteristics and the control flexibility of the standing wave piezoelectric linear ultrasonic motor.

Modeling of Multiteeth Contact Meshing Gear Dynamics with Backlash and Coincidence Degree

In the present paper, a multiteeth meshing gear contact dynamics model is proposed by introducing a modified robotic contact model. The inertial property, backlash of gear teeth and coincidence degree of gear meshing are considered into the model. In addition, the proposed model is used to simulate discontinuous meshing gear contact. Simultaneously, the gear meshing contact dynamical finite element model is also simulated using the Ansys/LS-DYNA software to demonstrate the rationality of the proposed model.

Volumetric Modeling and Experimental Validation of Normal Contact Dynamic Forces

A volumetric contact dynamics model has been proposed for the purpose of generating reliable and rapid simulations of contact dynamics. Forces and moments between bodies in contact can be expressed in terms of the volume of interference between the undeformed geometries. This allows for the modeling of contact between complex geometries and relatively large contact surfaces, while being computationally less expensive than finite element methods. However, the volumetric model requires experimental validation. Models for simple geometries in contact have been developed for stationary and dynamic contact, and an apparatus has been developed to experimentally validate these models. This paper focuses on validation of the normal contact models. Measurements of forces and displacements will be used to identify the parameters related to the normal force, i.e., the volumetric stiffness and hysteretic damping factor for metallic surfaces. The experimental measurements are compared with simulated results to assess the validity of the volumetric model.

An extended bristle friction force model with experimental validation

Bristle friction force models have been used by many as a preferred method for modeling friction forces. The original bristle friction force model is one-dimensional. It represents the physical reality for some practical application cases but does not accurately represent the friction phenomenon of a general contact between two 3D objects because the friction force vector is possibly rotating in the time-varying common tangential plane of the contacting surfaces. In this research the original integrated bristle friction model is extended to a 3-dimensional model. With such an extension, the resulting friction force model can be used to compute friction forces in both sticking and sliding regimes for general contact dynamics modeling. Simulation examples are presented to demonstrate the application of the model. Experiments were designed and performed to validate the new model. The presented validation exercise demonstrated that the extended bristle friction model can well duplicate experimental results including typical frictional behaviors such as sliding, sticking and stick-slip.

A new method for modelling and simulation of the dynamic behaviour of the wheel-rail contact

This paper presents a new method for modelling and simulation of the dynamic behaviour of the wheel-rail contact. The proposed dynamic wheel-rail contact model comprises wheel-rail contact geometry, normal contact problem, tangential contact problem and wheelset dynamic behaviour on the track. This two-degree of freedom model takes into account the lateral displacement of the wheelset and the yaw angle. Single wheel tread rail contact is considered for all simulations and Kalker's linear theory and heuristic non-linear creep models are employed. The second order differential equations are reduced to first order and the forward velocity of the wheelset is increased until the wheelset critical velocity is reached. This approach does not require solving mathematical equations in order to estimate the critical velocity of the dynamic wheel-rail contact model. The mathematical model is implemented in Matlab using numerical differentiation method. The simulated results compare well with the estimated results based on classical theory related to the dynamic behaviour of rail-wheel contact so the model is validated.

Real-Time Identification of Hunt–Crossley Dynamic Models of Contact Environments

Real-time estimates of environment dynamics play an important role in the design of controllers for stable interaction between robotic manipulators and unknown environments. The Hunt-Crossley (HC) dynamic contact model has been shown to be more consistent with the physics of contact, compared with the classical linear models, such as Kelvin-Voigt (KV). This paper experimentally evaluates the author's previously proposed single-stage identification method for real-time parameter estimation of HC nonlinear dynamic models. Experiments are performed on various dynamically distinct objects, including an elastic rubber ball, a piece of sponge, a polyvinyl chloride (PVC) phantom, and a PVC phantom with a hard inclusion. A set of mild conditions for guaranteed unbiased estimation of the proposed method is discussed and experimentally evaluated. Furthermore, this paper rigorously evaluates the performance of the proposed single-stage method and compares it with those of a double-stage method for the HC model and a recursive least squares method for the KV model and its variations in terms of convergence rate, the sensitivity to parameter initialization, and the sensitivity to the changes in environment dynamic properties.

Electrical contact resistance and dynamic contact stiffness for a cluster of microcontacts: cross-property connection in the low-frequency range

An explicit cross-property connection for a rough interface between the electrical contact resistance and dynamic contact stiffness has been established in the low-frequency limit. The present analysis is based on the first-order asymptotic model of multiple dynamic contact between small flat-ended indenters on an elastic half-space, which is a dynamic analogue of the quasi-static Greenwood model. The obtained results can be used in developing a vibration method for measuring the interface contact stiffness in tribological systems, and in estimating the surface-roughness effect in oscillation indentation tests.

An Investigation into the Influence of Damping on the Earthquake Response Analysis of a High Arch Dam

Two input models of seismic excitation, the nonlinear contact characteristics of contraction joints, were presented. The influence of the damping ratio on the seismic response of a high arch dam was then investigated. A new element (the viscous-spring boundary element capable of reflecting the radiation damping effects of an infinite foundation), the external source wave input subroutine, and the dynamic contact models, including the characteristics of normal opening-closing and radial sliding, were developed in this paper. The nonlinear contact behavior of contraction joints was simulated using a nonlinear exponential dynamic contact model, and the radial nonlinear characteristic was simulated using the Mohr-Coulomb criterion. Linear elastic and nonlinear seismic response analyses for a 300-m high concrete arch dam under construction were performed. The results showed that the damping ratio greatly influenced the seismic response of a high arch dam using a massless foundation model, and the damping ratio between 3–5% resulted in a conservative seismic response. The results of the viscous-spring boundary input model were in good agreement with those given by the massless foundation model when a damping ratio of 10% was used, but the openings of joints near the crown cantilever varied significantly. The effects of radiation damping of the foundation on the seismic response could be simplified to some extent by increasing the material damping of the dam in this study.

Three-DOF dynamic model with lubricant contact for thermal fly-height control nanotechnology

A three-degree-of-freedom dynamic contact model with friction and lubricant contact is introduced for thermal fly-height control of a near-contact flying slider. The proposed model addresses the issue of contact with a molecularly thin lubricant layer and includes a third degree-of-freedom, roll. Neither lubricant contact nor roll has been accounted for in previous models of the head–disk interface. Roll angle rotations allow for possible contact at other slider features such as the contact pads, which may induce destabilizing moments to the slider motion and lead to unwanted slider–disk contact. While roll is important primarily during operational shock, the inclusion of lubricant contact is found to be an important determinant of the severity of steady contact while lubricant properties are shown to affect the transient properties of the jump-to- and out-of-contact slider behaviour for near- and light-contact operation. The model's validity is examined using available experimental and simulation data that predict flying height gain due to air bearing stiffening as well as significant vibration zones before and after steady-state contact.

A damping term based on material properties for the volume-based contact dynamics model

The Gonthier et al. volume-based contact dynamics model addressed many different phenomena that influence the force of contact between two objects. This work extends Gonthier et al.'s work by proposing an alternate damping model based on material properties. The normal contact force based on volumetric interference information is derived using principles of mechanics of materials. The volume of interference and its rate of change are shown to be analogues to the material deformation and deformation rate. Simulations of the free direct central impact between two identical spheres are run using the proposed model, the Hunt–Crossley model and the Gonthier et al. model; these are compared to experimental data from the literature. This is followed by a discussion of those models.

Contact Dynamics Modeling for Snare Wire Type of End Effector in Capture Operation

Contact Dynamics Modeling for Snare Wire Type of End Effector in Capture Operation

Simulation of the three-dimensional motion of a cricket ball using a volumetric contact model

In this paper, a modeling and computational framework is presented to simulate the three-dimensional motion of a cricket ball. The framework is based on a volumetric contact dynamic model implemented in a modular and component-oriented commercial simulation tool. Aerodynamic drag forces, Magnus forces, and contact forces and torques are included in this model. The presented model has excellent portability and expandability. A volumetric contact model is used to evaluate the ground reactions and friction forces acting on the ball during the contact. The model parameters are tuned to match the characteristics of actual cricket ball impacts. Experimental data available from existing literature is used for this purpose. A few typical deliveries are simulated and analyzed to showcase the capability and effectiveness of this simulation model for cricket.

Rendering Virtual Tumors in Real Tissue Mock-Ups Using Haptic Augmented Reality.

Haptic augmented reality (AR) is an emerging research area, which targets the modulation of haptic properties of real objects by means of virtual feedback. In our research, we explore the feasibility of using this technology for medical training systems. As a possible demonstration example, we currently examine the use of augmentation in the context of breast tumor palpation. The key idea in our prototype system is to augment the real feedback of a silicone breast mock-up with simulated forces stemming from virtual tumors. In this paper, we introduce and evaluate the underlying algorithm to provide these force augmentations. This includes a method for the identification of the contact dynamics model via measurements on real sample objects. The performance of our augmentation is examined quantitatively as well as in a user study. Initial results show that the haptic feedback of indenting a real silicone tumor with a rod can be approximated reasonably well with our algorithm. The advantage of such an augmentation approach over physical training models is the ability to create a nearly infinite variety of palpable findings.

Control Strategy of Hardware‐in‐the‐Loop Simulator EPOS 2.0 for Autonomous Docking Verification

AbstractThis paper briefly describes the hybrid simulator system called European Proximity Operation Simulator (EPOS 2.0) and the development of the hardware‐in‐the‐loop (HIL) docking simulation concept. A critical requirement for the docking simulation of this HIL simulator is that the 6‐DOF robots in the loop have to exactly mimic the dynamic response of the two satellites during a contact operation. The main challenges to meet this requirement are in the stiffness of the robots, which is unlike that of the satellites, as well as the time delay in the HIL simulator. The paper mainly presents the impedance parameter identification concept for matching the impedance between the satellites impact model and the EPOS robots. Finally it presents the preliminary results and future work. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Model reduction of contact dynamics simulation using a modified Lyapunov balancing method

Finite element models are often used to simulate impact and contact dynamics responses of multibody dynamical systems. However, such a simulation remains very inefficient because very small integration time step must be used when solving the involved differential equations, especially when the involved contact stiffness is high. Although many model reduction techniques have been available to improve the efficiency of finite element based simulations, these techniques cannot be readily applied to contact dynamics simulations due to the high nonlinearity of the contact dynamics models. This paper presents a model reduction approach for finite-element based multibody contact dynamics simulation, based on a modified Lyapunov balanced truncation method. An example is presented to demonstrate that, by applying the model reduction the simulation process is significantly speeded up and the resulting error is bounded within an acceptable level. The performance of the method with respect to some influential factors such as element size, shape and contact stiffness is also investigated.

Modelling of condensed flexible bodies considering non-linear inertia effects resulting from gross motions

Besides various other application fields, flexible multi-body dynamics simulation is used in particular during the development process of internal combustion engines and power units. Problems such as crankshaft and engine dynamics, radial slider bearing dynamics or noise, vibration, and harshness can be investigated using this methodology. Any specific engine component, called body, can be represented by different methods. Besides beam-mass representations and structured modelling, finite element models are commonly used. As these imply a large number of degrees of freedom, they cannot be applied directly to multi-body dynamics ensuring computational performance. Therefore, condensation methods need to be applied which result in a reduced model with equivalent dynamical properties. This is particularly important if detailed, highly non-linear contact dynamic models, for instance the well-known Reynolds equation, are considered. Typically, condensation methods are applied to structural matrices of bodies which perform only vibration motions without any global motions. This study outlines a floating frame of reference formulation for condensed components, which perform global motions in addition to the vibration motions. For this purpose, non-linear inertia terms of the reduced body, which result from the global motions need to be computed considering the applied reduction strategy. Both the theoretical background of the formulation and some application examples of the method will be discussed.

Van der Waals cohesion in nonsmooth contact dynamics: application to powder mixtures

This work aims to introduce van der Waals forces, and more generally cohesive forces, in a nonsmooth contact dynamics (NSCD) model for studying dense particle systems. The contact dynamics method is based on the relative velocities of interacting bodies. On the other hand, the van der Waals force considers only distance between the bodies. Consequently, we developed a theoretical argument for reconciling velocity and position aspects. As an illustration of our numerical method, we investigated the mixing of different granular species in a rotating drum. We consider large (100 μm radius) and small (5 μm radius) spheres. For these latter, the cohesion forces are larger than their weight. This subject is of great interest in powder handling. We prove that the NSCD approach is suited to modeling dense particle systems such as cohesive powders.

Research on Dynamic Wear of Revolution Joint with Clearance for Mechanical System

In order to study the dynamic wear of revolution joint with clearance in mechanical system, the dynamic model of mechanical system with joint clearance is presented. The clearance model is established based on clearance vector model. The contact dynamic model in joint clearance is established using the nonlinear equivalent spring-damp model and the friction effect is considered by using correction Coulomb friction model. And then the models are incorporated into dynamics simulation software ADAMS, the dynamics model of mechanical system with joint clearance is established based on ADAMS and the simulation is made. Furthermore, the contact dynamics parameters are drawn and calculate the wear volume of joint clearance based on Archard’s wear model. Finally, a crank follower mechanical system is used to perform the simulation and the dynamic wear characteristics are analyzed.

Meniscus and Viscous Forces during the Nanoscale Separation of Sphere-on-Sphere Contact Surfaces

When two surfaces are brought into contact or at small separations, the liquid between them forms meniscus, which contributes to adhesion and friction. The increased adhesive force and friction are always the substantial cause leading to micro/nanodevices’s failure. In this study, a dynamic contact model of sphere-on-sphere surfaces during nanoscale separation is presented. A numerical analysis of meniscus and viscous forces based on the dynamic contact model has been carried out. During the separation process, the effects of separation distance, initial meniscus height, surface wettability and separating time on meniscus and viscous forces between the contact surfaces are investigated. The results of numerical solution revealed the adhesion mechanism of sphere-on-sphere surfaces during the separation with liquid mediated. The analyses provide a fundamental understanding of the separating process of two sphere surfaces. It is also useful for the design of the de-wetting and antisticking micro/nanoscale surfaces in various devices.