The objective of this paper is to mitigate the wave-induced vibration of offshore platform with magneto-rheological (MR) damper. The model of the platform coupled with MR damper is established where the external wave force is approximated with a white noise via a designed filter. Based on Linear Quadratic Gaussian (LQG) method, the optimal control force is determined when taking the measurement...

This paper shows how globally attractive limit cycle oscillations can be induced in a system with a nonlinear feedback element. Based on the same principle as the Van der Pol oscillator, the feedback behaves as a negative damping for low velocities but as an ordinary damper for high velocities. This nonlinear damper can be physically implemented with a continuous variable transmission and a spr...

The PSR (Proton Storage Ring) at LANSCE has observed an E-P (electron-proton) instability. A wideband analog feedback damper system was designed and implemented that has shown it is possible to correct this instability. The damper system consists of two 180 degree hybrids, low level amplifiers, a delay line, comb filter, power amplifiers, and adjustable delay lines. The system bandwidth is abou...

A modified skyhook control for the semi-active Macpherson suspension system is considered. A new quarter-car model, which incorporates the rotational motion of the unsprung mass, is introduced. A feedback control law in the form of a modified skyhook control is derived. Two filters to estimate the absolute velocity of the sprung mass and the relative velocity of the rattle space are designed. B...

Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and ways of reducing them are indicated. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e., a wide-band damper of press...

Dampers in mechanical systems provide safety and comfort against dynamical and impact forces transmitted by external profiles. Since dampers are made of diverse elements, have a large range of performance variables. Therefore, analytical solution for predicting damper behavior is difficult. In the absence of analytical models, one of the popular and reliable methods is statistical modeling. In ...

The kinematics of an arresting-hook unit are studied in order to determine, within the limits of the assumption of a perfectly rigid hook unit, the damper force necessary to control hook bounce. The necessity for a smooth deck and the desirability of small trail angle for the hook unit are demonstrated from several aspects. The design requirements for a hook damper unit are discussed in all the...

This paper discusses the identification of nonlinear black-box simulation models for a continuously variable, semi-active damper for a passenger car. Two model classes are considered and compared. While both classes have an output error model structure, the first class applies a polynomial approximation function and the second uses a neural network. The identification procedure automatically se...

the rotational friction dampers can be improved the seismic behavior of the steel structures, and they can be reduced the internal forces in the bracing members, columns and the other structural members. in this research, a simple method for modeling and analysis of braced frames equipped by these dampers is proposed. the proposed model describes seismic behavior of dampers very well and it is ...