The 2D-Signorini contact problem with Tresca and Coulomb friction is discussed in infinitedimensional Hilbert spaces. First, the problem with given friction (Tresca friction) is considered. It leads to a constraint non-differentiable minimization problem. By means of the Fenchel duality theorem this problem can be transformed into a constrained minimization involving a smooth functional. A regu...

The interfacial structure/property relationships of a representative composite system consisting of SIC (SCS-6) fibers in a T&Al + Nb intermetallic alloy have been investigated. Two samples were fabricated at 1040°C with different exposure times in order to vary the amount of fiber-matrix reaction. This resulted in samples with reaction zone thicknesses (S) of 1.1 and 1.7pm, while ensuring roug...

The use of Coulomb’s friction law with the principles of classical rigid-body dynamics introduces mathematical inconsistencies. Specifically, the forward dynamics problem can have no solutions or multiple solutions. In these situations, compliant contact models, while increasing the dimensionality of the state vector, can resolve these problems. The simplicity and efficiency of rigid-body model...

A globally exponentially stable speed observer for mechanical systems was recently reported in the literature, under the assumptions of known (or no) Coulomb friction and no disturbances. In this note we propose and adaptive version of this observer, which is robust vis–à–vis constant disturbances. Moreover, we propose a new globally convergent speed observer that, besides rejecting the disturb...

In this paper, the effects of friction compensation, including exact compensation, undercompensation and overcompensation, in PD controlled 1DOF mechanical systems are investigated. The friction force that is acting on the mechanical system and the friction compensation term in the feedback loop are described by a class of discontinuous friction models consisting of static, Coulomb and viscous ...

This article describes the detailed friction modeling of the Genera1 Electric GP132 industrial robot. Friction is an area whose importance is often discounted in the development of control systems because it is thought to be insignificant or unmodelable. This work demonstrates that friction does have a predictable structure, and that significant performance improvement can be realized through i...

The dynamics of charged Coulomb grains in a plasma is numerically and analytically investigated. Analogous to recent experiments, it is assumed that the grains are trapped in an external parabolic field. Our simulations are based on a Langevin model, where the grain-plasma interaction is realized by a velocity-dependent friction coefficient and a velocity-independent diffusion coefficient. In a...

Practical problems like regulating robot grippers critically rely on accurately predicted friction forces. Qualified methods are derived and discussed subsequently. Special attention is paid to the question of solution existence. A time-stepping scheme which supports Coulomb friction and inelastic impacts is implemented and the numerical results are analyzed. The approach proofs to be stable, a...