Vibration Confinement by Minimum Modal Energy Eigenstructure Assignment

2007 ◽  
Author(s):  
Mohammad Rastgaar Aagaah ◽  
Mehdi Ahmadian ◽  
Steve C. Southward
Keyword(s):  
Closed Loop ◽  
Null Space ◽  
Flexible Structures ◽  
Output Feedback Control ◽  
Open Loop ◽  
Loop System ◽  
Eigenstructure Assignment ◽  
Open Loop System ◽  
The Matrix ◽  
Value Decomposition

A novel Eigenstructure Assignment (ESA) method for vibration confinement of flexible structures has been developed. This method is an output feedback control and determines the closed-loop systems that their eigenvectors are orthogonalized to the open-loop eigenvectors. This method is a numerical method and used Singular Value Decomposition (SVD) to find the null space of the closed-loop eigenvectors. The matrix that spans the null space can be used to regenerate the open-loop system as well as the systems that have orthogonal eigenvectors to the regenerated open-loop system. As a result the isolation of vibration is independent of the type of the disturbance. Also in this method, the energy of the closed-loop system is minimized. As an important outcome, the proposed method needs neither to specify the closed-loop eigenvalues nor to define a desired set of eigenvectors.

Effect of the Actuators’ Location on Vibration Suppression Using Minimum Modal Energy Eigenstructure Assignment

2007 ◽  
Author(s):  
Mohammad Rastgaar Aagaah ◽  
Steve C. Southward ◽  
Mehdi Ahmadian
Keyword(s):  
Closed Loop ◽  
Vibration Suppression ◽  
Null Space ◽  
Flexible Structures ◽  
Output Feedback Control ◽  
Open Loop ◽  
Loop System ◽  
Eigenstructure Assignment ◽  
Gain Matrix ◽  
Coefficient Vector

A new Eigenstructure Assignment (ESA) method for vibration confinement of flexible structures has been developed. This method is based on finding an output feedback control gain matrix in such a way that the closed-loop eigenvectors are orthogonal to the open-loop ones. Singular Value Decomposition (SVD) is used for finding the matrix that spans the null space of the closed-loop eigenvectors. It is shown that this matrix has a unique property that can be used to regenerate the open-loop system. This method finds a coefficient vector which leads to a zero gain matrix while several coefficient vectors can be found simultaneously which are orthogonal to the open-loop coefficient vector. As a result, the closed-loop eigenvectors are orthogonal to the open-loop ones. It is shown that the modal energy of the closed loop system is reduced. Moreover, the proposed method needs neither to specify the closed-loop eigenvalues nor to define a desired set of eigenvectors. Also it is shown that if the maximum force of the actuators and the consumed energy of the actuators need to be low, actuators have to be relatively close to input. If the amplitude of vibration in isolated area has to be minimized as much as possible, the actuators need to be relatively closer to isolated area. Also the algorithm of the minimum eigenstructure assignment method has been modified to eliminate the effect of the actuators that are located on the nodes of different vibrational modes.

Orthogonal Eigenstructure Control for Vibration Suppression

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Mohammad Rastgaar ◽  
Mehdi Ahmadian ◽  
Steve Southward
Keyword(s):  
Closed Loop ◽  
Vibration Suppression ◽  
Control Method ◽  
Null Space ◽  
Output Feedback Control ◽  
Open Loop ◽  
Unique Property ◽  
Gain Matrix ◽  
Coefficient Vector ◽  
Value Decomposition

Orthogonal eigenstructure control is a novel active control method for vibration suppression in multi-input multi-output linear systems. This method is based on finding an output feedback control gain matrix in such a way that the closed-loop eigenvectors are almost orthogonal to the open-loop ones. Singular value decomposition is used to find the matrix, which spans the null space of the closed-loop eigenvectors. This matrix has a unique property that has been used in this new method. This unique property, which has been proved here, can be used to regenerate the open-loop system by finding a coefficient vector, which leads to a zero gain matrix. Also several vectors, which are orthogonal to the open-loop eigenvectors, can be found simultaneously. The proposed method does not need any trial and error procedure and eliminates not only the need to specify any location or area for the closed-loop eigenvalues but also the requirements of defining the desired eigenvectors. This method determines a set of limited number of closed-loop systems. Also, the elimination of the extra constraints on the locations of the closed-loop poles prevents the excessive force in actuators.

Accounting for Out-of-Bandwidth Modes in the Assumed Modes Approach: Implications on Colocated Output Feedback Control

1997 ◽  
Vol 119 (3) ◽  
pp. 390-395 ◽  
Author(s):  
R. L. Clark
Keyword(s):  
Output Feedback ◽  
Closed Loop ◽  
Output Feedback Control ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Open Loop System ◽  
Low Frequencies ◽  
Poles And Zeros ◽  
Admissible Functions

Colocated, output feedback is commonly used in the control of reverberant systems. More often than not, the system to be controlled displays high modal density at a moderate frequency, and thus the compliance of the out-of-bandwidth modes significantly influences the performance of the closed-loop system at low frequencies. In the assumed modes approach, the inclusion principle is used to demonstrate that the poles of the dynamic system converge from above when additional admissible functions are used to expand the solution. However, one can also interpret the convergence of the poles in terms of the zeros of the open-loop system. Since colocated inputs and outputs are known to have interlaced poles and zeros, the effect of a modification to the structural impedance locally serves to couple the modes of the system through feedback. The poles of the modified system follow loci defined by the relative location of the open-loop poles and zeros. Thus, as the number of admissible functions used in the series expansion is increased, the interlaced zeros of the colocated plant tend toward the open-loop poles, causing the closed-loop poles to converge from above as predicted by the inclusion principle. The analysis and results presented in this work indicate that the cumulative compliance of the out-of-bandwidth modes and not the modes themselves is required to converge the zeros of the open-loop system and the poles of the closed-loop system.

Multi-Stage System Identification of a Gas Turbine

2017 ◽  
Author(s):  
Amit Pandey ◽  
Maurício de Oliveira ◽  
Chad M. Holcomb
Keyword(s):  
Gas Turbine ◽  
Closed Loop ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop Control ◽  
Input Output ◽  
Open Loop System ◽  
Loop Control ◽  
Multi Stage ◽  
Identification Techniques

Several techniques have recently been proposed to identify open-loop system models from input-output data obtained while the plant is operating under closed-loop control. So called multi-stage identification techniques are particularly useful in industrial applications where obtaining input-output information in the absence of closed-loop control is often difficult. These open-loop system models can then be employed in the design of more sophisticated closed-loop controllers. This paper introduces a methodology to identify linear open-loop models of gas turbine engines using a multi-stage identification procedure. The procedure utilizes closed-loop data to identify a closed-loop sensitivity function in the first stage and extracts the open-loop plant model in the second stage. The closed-loop data can be obtained by any sufficiently informative experiment from a plant in operation or simulation. We present simulation results here. This is the logical process to follow since using experimentation is often prohibitively expensive and unpractical. Both identification stages use standard open-loop identification techniques. We then propose a series of techniques to validate the accuracy of the identified models against first principles simulations in both the time and frequency domains. Finally, the potential to use these models for control design is discussed.

Modelling and Control of HSFDs for Active Control of Rotor-Bearing Systems

1994 ◽  
Author(s):  
A. El-Shafel ◽  
J. P. Hathout
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Transient Behavior ◽  
Pressure Control ◽  
Fast Response ◽  
Open Loop ◽  
Loop System ◽  
Squeeze Film ◽  
Open Loop System ◽  
Loop Control

This paper summarizes the development of hybrid squeeze film dampen (HSFDs) for active control of rotor vibrations. Previously, it was shown both theoretically and experimentally that HSFDs can be used for controlling rotor vibrations (El-Shafei, 1993). This is done by controlling the flow in a squeeze film damper through movable end seals, thus achieving the ability to change the damper from a short damper to a long damper and vice versa. However, the control of the HSFD was manual. In this paper, an automatically controlled circuit is developed for the HSFD, incorporating a pressure control servovalve for controlling the pressure in the scaling chambers. A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. The transient behavior of the system, including the sealing ring dynamics, illustrates that the open-loop system exhibits well behaved, stable, and fast response. In addition it is shown that the HSFD can achieve any amount of damping between the short and long damper modes through the accurate positioning of the sealing rings. The simulation results illustrate that the automatically controlled HSFD can be a very useful device for the active control of rotors. A closed loop control strategy with feedback on rotor speed is also investigated both from the points of view of steady state and transient behaviors. It is shown that this closed loop strategy results in a much improved behavior of the rotor system.

Water Hammer Pressure Transients in a Closed Loop System

Volume 3 ◽  
2004 ◽  
Author(s):  
Robert A. Leishear ◽  
Jeffrey H. Morehouse
Keyword(s):  
Method Of Characteristics ◽  
Closed Loop ◽  
Water Hammer ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Open Loop System ◽  
Trapped Air ◽  
Closed Loop Systems ◽  
Fluid Transients

The effects of fluid transients, or water hammer, in closed loop systems are somewhat different than those observed in open ended systems. The open loop system has received much attention in the literature, not so for the closed system. The generally accepted method of characteristics (MOC) technique was applied herein to investigate closed loop systems. The magnitudes of the pressures during fluid transients were investigated for examples of rapid valve closures, and the operations of parallel pumps. The effects of trapped air in the system were also considered for these examples. To reduce the pressures caused by the transients, the installation of slow closing valves were evaluated for different conditions.

The Application of Fractional Order Calculus in Closed-Loop System Control

2012 ◽  
Vol 442 ◽  
pp. 315-320
Author(s):  
Yun Fang Feng
Keyword(s):  
Closed Loop ◽  
Design Method ◽  
Open Loop ◽  
Loop System ◽  
System Control ◽  
Closed Loop System ◽  
Open Loop System ◽  
System Robustness ◽  
Fractional Controller ◽  
Frequency Phase

A design method of fractional controller has been developed to meet the five different specifications, including for the closed-loop system robustness. The specifications of cross frequency, phase to get financing ϕ meters and robustness and complete performance curve based on level off the stage of open loop system, ensure damping is worse reaction time of model uncertainty gain change.

Remarks on the Modelling of Active Structures With Colocated Piezoelectric Actuators and Sensors

1995 ◽  
Author(s):  
N. Loix ◽  
A. Preumont
Keyword(s):  
High Frequency ◽  
Closed Loop ◽  
Transfer Functions ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Local Effects ◽  
Open Loop System ◽  
Active Structures ◽  
Modelling Techniques

Abstract This paper aims to attract the attention of the designers of active structures on the importance of evaluating properly the feedthrough component of the open-loop transfer functions. It is shown that overlooking the feedthrough component can change significantly the location of the zeros of the open-loop system and, as a result, alter drastically the performance of the closed-loop system. The feedthrough term may result from the quasi-static contribution of the high frequency modes or from local effects that are neglected by over-simplified modelling techniques (e.g. plate or beam instead of shell). The problem is illustrated with a cantilever beam provided with strain actuators.

A Biological Feedback Control System with Electronic Input: The Artificially Closed Femur-Tibia Control System of Stick Insects

1986 ◽  
Vol 120 (1) ◽  
pp. 369-385 ◽  
Author(s):  
G. WEILAND ◽  
U. BÄSSLER ◽  
M. BRUNNER
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Closed Loop ◽  
Stick Insect ◽  
Open Loop ◽  
Loop System ◽  
Chordotonal Organ ◽  
Closed Loop System ◽  
Open Loop System ◽  
Stick Insects

An experimental arrangement was constructed which is based on the open-loop femur-tibia control system of two stick insect species (Carausius morosus and Cuniculina impigra). It could be artificially closed in the following way: the position of the tibia was measured by an optical device and this value was used to drive a penmotor which moved the receptor apodeme of the femoral chordotonal organ in the same way as in intact animals. This arrangement allows direct comparison of the behaviour of the open-loop and the closed-loop system as well as introducing an additional delay. The Carausius system has a phase reserve of only 30°-50° and the factor of feedback control approaches 1 between 1 and 2 Hz. This agrees with the observation that an additional delay of 70–200 ms produces long-lasting oscillations of 1–2 Hz. The Cuniculina system has a larger phase reserve and consequently a delay of 200 ms produced no oscillations. All experiments show that extrapolation from the open-loop system to the closed-loop system is valid, despite the non-linear characteristics of the loop. Consequences for servo-mechanisms during walking and rocking movements are discussed.

Emotional Modularization

2015 ◽  
Author(s):  
Shuichi Fukuda
Keyword(s):  
Closed Loop ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Open Loop System ◽  
Flexible Tool ◽  
Customer Expectations

This paper points out that in order to provide emotional satisfaction to the customer, hardware products should be modularized not only with functions or shapes, but with more meanings such as adaptability, etc. Thus, a network-structured modularization is called for more than a tree-structured one to cope with diverse customer expectations. The emerging field of material digitalization, which can be compared to physical FEM, is expected to provide a versatile and flexible tool for this purpose and it will change our design from the current open loop system to the closed loop system so that it will provide us with the capability of managing deterioration and that of adaptability to the frequently and widely changing situations.

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