This study introduces two types of self-oscillating circuits that are frequently found in power electronics applications. Special effort is made to relate the circuits to the analogous mechanical systems of some important scientific inventions: Galileo’s pendulum clock and Coulomb’s friction model. A little touch of related history and philosophy of science will hopefully encourage curiosity, a...

Friction is a nonlinear phenomenon which has destructive effects on performance of control systems. To obviate these effects, friction compensation is an effectual solution. In this paper, an adaptive technique is proposed in order to eliminate limit cycles as one of the undesired behaviors due to presence of friction in control systems which happen frequently. The proposed approach works for n...

The attention towards seismic mitigation using passive control systems has increased significantly over the last few decades to reduce earthquake demands and achieve required performance objectives. Nowadays, friction pendulum bearings have proven efficient in mitigating regular RC structures subjected a wide range of earthquakes. Nonetheless, limited studies were dedicated investigating effici...

OBJECTIVES Wear of total hip replacements has been the focus of many studies. However, frictional effects, such as high loading on intramodular connections or the interface to the bone, as well as friction associated squeaking have recently increased interest about the amount of friction that is generated during daily activities. The aim of this study was thus to establish and validate a three-...

A well known theorem says that the forced pendulum equation has periodic solutions if there is no friction and the external force has mean value zero. In this paper we show that this result cannot be extended to the case of linear friction.

Large-scale tanks are widely used for storing chemicals and fuels. Their failure due to natural (e.g., earthquakes) and/or man-made hazards can lead disastrous consequences. Nonetheless, they often constructed in seismic-prone regions. For this reason, base isolation is the seismic protection of large tanks, aiming “decouple” superstructure from imposed ground motions. In study, a combined opti...

We consider the simple pendulum equation −u′′(t) + f(u′(t)) = λ sinu(t), t ∈ I := (−1, 1), u(t) > 0, t ∈ I, u(±1) = 0, where 0 < ≤ 1, λ > 0, and the friction term is either f(y) = ±|y| or f(y) = −y. Note that when f(y) = −y and = 1, we have well known original damped simple pendulum equation. To understand the dependance of solutions, to the damped simple pendulum equation with λ 1, upon the te...

A second order sliding mode (SOSM) approach is proposed for orbital stabilization of a friction pendulum, operating under uncertain conditions. Only position measurements are assumed to be available. A SOSM velocity observer is developed and included into the closedloop system, driven by the quasihomogeneous controller that provides orbital stabilization of the pendulum. Performance issues of t...

In this paper we present an energy-based algorithm to minimize limit cycles in dynamically balancing wheeled inverted pendulum (IP) machines. Because the algorithm is not based on absolute values of parameters, the performance is robust and accounts for mechanical reconfiguration and wear. The effects of phenomena such as drive-train friction, rolling friction, backlash and sensor bandwidth are...