Estimation of maximum drift of multi‐degree‐of‐freedom shear structures with unknown parameters using only one accelerometer

2021 ◽  
Author(s):  
Kangqian Xu ◽  
Akira Mita
Keyword(s):  
Degree Of Freedom ◽  
Unknown Parameters ◽  
Shear Structures

scholarly journals Modeling And Parameter Identification Of Vibrations Of A Double Torsion Pendulum With Friction

2015 ◽  
Vol 9 (4) ◽  
pp. 204-212 ◽  
Author(s):  
Ernest Czerwiński ◽  
Paweł Olejnik ◽  
Jan Awrejcewicz
Keyword(s):  
Angular Displacement ◽  
Degree Of Freedom ◽  
Torsion Pendulum ◽  
State Variables ◽  
Unknown Parameters ◽  
Linear Harmonic Oscillator ◽  
Frictional Forces ◽  
Free Body ◽  
Set Up ◽  
Double Torsion

Abstract The purpose of this paper is to investigate a double torsion pendulum with planar frictional contact. The single torsion pendulum with one-degree-of-freedom is an angular equivalent of the linear harmonic oscillator. The second degree of freedom has been obtained by adding a free body to the inverted single torsion pendulum. The free body’s angular displacement is caused by frictional forces appearing in the interface (contact zone) between the free body and the pendulum column’s head kinematically excited at its base by a mechanism with torsion spiral spring. An experimental station has been set up and run to find most unknown parameters of the pendulum from the time series of state variables taken as inputs to the Nelder-Mead method of identification. The obtained results proved significant usability of the identification method in the case of numerical simulation of the pendulum’s dynamical model. It has not been satisfactorily proved in the case of time characteristics coming from a real system that exhibits also some unrecognized physical effects.

Stationary Response Probability Distribution of SDOF Nonlinear Stochastic Systems

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
Lincong Chen ◽  
Jun Liu ◽  
Jian-Qiao Sun
Keyword(s):  
Stochastic Systems ◽  
Gaussian White Noise ◽  
Accurate Solution ◽  
Degree Of Freedom ◽  
Unknown Parameters ◽  
Nonlinear Stochastic Systems ◽  
General Technique ◽  
Trial Solution ◽  
Weighted Residuals ◽  
Mdof Systems

There has been no significant progress in developing new techniques for obtaining exact stationary probability density functions (PDFs) of nonlinear stochastic systems since the development of the method of generalized probability potential in 1990s. In this paper, a general technique is proposed for constructing approximate stationary PDF solutions of single degree of freedom (SDOF) nonlinear systems under external and parametric Gaussian white noise excitations. This technique consists of two novel components. The first one is the introduction of new trial solutions for the reduced Fokker–Planck–Kolmogorov (FPK) equation. The second one is the iterative method of weighted residuals to determine the unknown parameters in the trial solution. Numerical results of four challenging examples show that the proposed technique will converge to the exact solutions if they exist, or a highly accurate solution with a relatively low computational effort. Furthermore, the proposed technique can be extended to multi degree of freedom (MDOF) systems.

scholarly journals Particle swarm optimization–based adaptive super-twisting sliding mode control design for 2-degree-of-freedom helicopter

2019 ◽  
Vol 52 (9-10) ◽  
pp. 1403-1419 ◽  
Author(s):  
Amjad J Humaidi ◽  
Alaq F Hasan
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Lyapunov Theory ◽  
Degree Of Freedom ◽  
Unknown Parameters ◽  
Controlled System ◽  
Mode Control ◽  
Sliding Mode Controllers ◽  
Adaptive Control Algorithm ◽  
Novel Design

This paper presents a novel design of adaptive super-twisting sliding mode controller for two-axis helicopter with model uncertainties. The high-order super-twisting sliding mode control strategy is used to guarantee that the sliding surface can reach the equilibrium point in a shorter time and to avoid the chattering problem. The adaptive control algorithm has been developed based on Lyapunov theory to estimate the unknown parameters of 2-degree-of-freedom helicopter such that the global stability of the controlled system based on adaptive super-twisting sliding mode is guaranteed. A comparison study between conventional and adaptive super-twisting sliding mode controllers is made and the effectiveness of the proposed scheme is verified via computer simulation.

Approximating power for significance tests with one degree of freedom.

1997 ◽  
Vol 2 (2) ◽  
pp. 186-191 ◽  
Author(s):  
William P. Dunlap ◽  
Leann Myers
Keyword(s):  
Degree Of Freedom ◽  
Significance Tests
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