Instantaneous Stochastic Optimal Control of Seismically Excited Structures Based on Time Domain Explicit Method

2013 ◽  
Vol 790 ◽  
pp. 215-218
Author(s):  
Xue Ping Li ◽  
Chao Yu ◽  
Jie Yang Zhang ◽  
Jing Jie Zhou ◽  
Lin Ming Zhang
Keyword(s):  
Optimal Control ◽  
Time Domain ◽  
Stochastic Optimal Control ◽  
The State ◽  
Control Force ◽  
Building Structures ◽  
Explicit Method ◽  
Plane Shear ◽  
Shear Structure

A new instantaneous stochastic optimal control (ISO) for the linear building structures subjected to non-stationary random excitations is proposed. A plane shear structure is taken as the example to illustrate the proposed method. The main advantage of the method is that the control force is easy to be calculated because the expression of the control force is independent of the state of the system.

Near-Optimal Time-Domain Control of Small Buoys in Irregular Waves

2014 ◽  
Author(s):  
Umesh A. Korde ◽  
R. Cengiz Ertekin
Keyword(s):  
Optimal Control ◽  
Impulse Response ◽  
Time Domain ◽  
The Body ◽  
Irregular Waves ◽  
Single Frequency ◽  
Impulse Response Functions ◽  
Control Force ◽  
Response Functions ◽  
Absorbed Power

Within the linear theory framework, smooth optimal control for maximum energy conversion in irregular waves requires independent synthesis of two non-causal impulse response functions operating on the body oscillations near the free surface, and one non-causal impulse response function relating the exciting force to the incident wave profile at the body. Full cancellation of reactive forces and matching of radiation damping thus requires knowledge or estimation of device velocity into the future. As suggested in the literature, the control force can be synthesized in long-crested waves by suitably combining the ‘full’ impulse response functions with wave surface elevation information at an appropriately determined distance up-wave of the device. This paper applies the near-optimal control approach investigated earlier by one of the authors (Korde, UA, Applied Ocean Research, to appear) to small floating cylindrical buoys. Absorbed power performance is compared with two other cases, (i) when single-frequency tuning is used based on non-real time adjustment of the reactive and resistive loads to maximize conversion at the spectral peak frequency, and (ii) when no control is applied with damping set to a constant value. Time domain absorbed power results are discussed.

An active vibration control model for coupled flexible systems

2008 ◽  
Vol 222 (11) ◽  
pp. 2087-2098
Author(s):  
J C Niu ◽  
A Y T Leung ◽  
C W Lim ◽  
P Q Ge
Keyword(s):  
Optimal Control ◽  
Vibration Control ◽  
State Space ◽  
Power Flow ◽  
Passive Control ◽  
Flexible Structures ◽  
Coupled System ◽  
The State ◽  
Coupled Systems ◽  
Control Force

This paper presents a novel general model for complex flexible coupled systems. In this model, parallel structures of force actuators and passive spring isolators are installed between the machine and the foundation, and some moment actuators such as piezoelectric patches are installed on the flexible foundation whose vibration cancellation feature is the key object of vibration control. This model combines active and passive control, force and moment control into a single unit to achieve the efficient vibration control of flexible structures by multiple approaches. The state-space governing equations of the coupled system are deduced. Based on the description of the state-space equation of the coupled system, the transmission paths for the power flow transmitted into the foundation are discussed in the frequency domain, and then combined into a single function. The function includes two parts: the passive and active terms, which can be conveniently employed in an optimal control strategy to achieve power flow control. The transmission characteristics of the power flow by optimal control are discussed in detail. Numerical simulations are presented to show that both force and moment controls in the analytical model can achieve substantial vibration cancellation.

Maximum Principle for the Optimal Control of a Hyperbolic Equation in Two Space Dimensions

1996 ◽  
Vol 2 (1) ◽  
pp. 3-15 ◽  
Author(s):  
I.S. Sadek ◽  
J.M. Sloss ◽  
S. Adali ◽  
J.C. Bruch
Keyword(s):  
Optimal Control ◽  
Maximum Principle ◽  
Hyperbolic Equation ◽  
Vibration Suppression ◽  
Control Function ◽  
Time Derivative ◽  
The State ◽  
Control Force ◽  
The Maximum Principle ◽  
Two Space Dimensions

A maximum principle is developed for a class of problems involving the optimal control of a damped parameter system governed by a not-necessarily separable linear hyperbolic equation in two space dimensions. An index of performance is formulated, which consists of functions of the state variable, its first and second order space derivatives and first order time derivative, and a penalty function involving the open-loop control force. The solution of the optimal control problem is shown to be unique using convexity arguments. The maximum principle given involves a Hamiltonian, which contains an adjoint variable as well as an admissible control function. The state and adjoint variables are linked by terminal conditions leading to a boundary/initial/terminal value problem. The maximum principle can be used to compute the optimal control function and is particularly suitable for problems involving the active control of two-dimensional structural elements for vibration suppression.

Fuzzy Control of Structure for Semi-Active Friction Damper Using GA

2006 ◽  
Author(s):  
Hong-Nan Li ◽  
Dahai Zhao
Keyword(s):  
Optimal Control ◽  
State Space ◽  
Control Strategy ◽  
Fuzzy Model ◽  
The State ◽  
Effective Control ◽  
Control Law ◽  
Control Force ◽  
Friction Damper ◽  
Active Friction

The motion of friction dampers, either passive or semi-active, involves sticking and slipping phases. The idea for increasing the performance of semi-active friction damper is to maintain its motion in the slipping phase as much as possible, since energy is dissipated during the slipping phase rather than the sticking phase. The effectiveness of semi-active friction damper depends on the control strategy used. Because of nonlinear characteristic of the friction damper, the establishment of an effective control strategy is a challenging effort. In optimal control theory, the bang-bang is a class of classical control laws. However, when applied to real structure control, it will produce some problems. One of disadvantages is that differential equation has to be solved on-line during the control process, which will lead to time delay and instability to the control system. The other is that the undesirable spikes will emerge near the origin of the state space due to high speed switching of the control force. In this paper, a new strategy based on the T-S fuzzy model and modified bang-bang algorithm is proposed. First, the theory of the T-S fuzzy model is briefly introduced. Next, the modified bang-bang control law is reviewed. Then, the implementation procedure of the proposed control method is detailed for description, and the optimal control force in the consequent part of the T-S model is achieved by the genetic algorithm. Finally, on the establishment of the semi-active control law, the approach here is applied to the vibration control of a three story building with a semi-active friction damper. Numerical simulation results indicate that the proposed control strategy not only effectively reduce the chattering effect as the responses of the structure cross through the zero points in the state space but also is adaptive to varying excitations from weak and strong earthquakes.

Experimental Determination of the Two-Dimensional State of Stress and the Orthotropic Elasticity Coefficients for Coatings

1990 ◽  
Vol 203 ◽  
Author(s):  
Richard J. Farris ◽  
M. A. Maden ◽  
K. Tong
Keyword(s):  
Elastic Constants ◽  
Physical Property ◽  
The State ◽  
Normal Stresses ◽  
Free Standing ◽  
Vibrationally Excited ◽  
Plane Shear ◽  
Plane Normal ◽  
State Of Stress ◽  
The One

ABSTRACTThe state of stress for a uniform coating away from the edges reduces to that of plane stress, two in-plane normal stresses, and an in-plane shear stress. For this state, the interface between the coating and the substrate is totally stress free. Since the substrate and the coating are not interacting mechanically, an internal section of the substrate can be removed creating a tensioned drum-like membrane without altering the stress state. Holographic interferometry of vibrationally excited membranes is used to evaluate the stress. Using this technique, up to thirty vibrational modes can be obtained. This high degree of redundancy enables one to determine the one shear and two normal stresses that act in the plane of the coating. The only physical property requires is the coating density. The density is obtained from commonly reported literature values. Simple variations on the membrane vibration scheme, e.g., cutting the membrane to create a uniaxially tensioned ribbon, enables one to determine the in-plane Poisson's ratio and shearmodulus.In separate but related experiments on commercially made free-standing films with residual orientation, the above techniques, combined with special free and axially constrainedcompressibility experiments should enable all of the Poisson's ratios and elasticmoduli for an orthotropic material (nine elastic constants) to be determined. Methods for measuring the state of stress and the elastic constants are required to predict the state of stress in complex coating geometries.

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