Consideration of Complex Support Structure Dynamics in Rotordynamic Assessments

2013 ◽  
Author(s):  
Thomas D. Krüger ◽  
Sauro Liberatore ◽  
Eric Knopf ◽  
Alastair Clark
Keyword(s):  
Dynamic Behaviour ◽  
Computation Time ◽  
Degree Of Freedom ◽  
Space Representation ◽  
Lumped Mass ◽  
Support Structure ◽  
State Space Representation ◽  
Prediction Quality ◽  
Theoretical Approaches

In rotordynamic analyses, support structures are commonly represented by lumped mass systems (single-degree-of-freedom, SDOF). This representation is easy to implement using standard rotordynamic tools. However, in reality the dynamic behaviour of the support structure (e.g. pedestals, casings, foundations) are in general much more complex. Only a multi-degree-of-freedom (MDOF) representation provides modelling close to reality. For many applications the dynamic behaviour of the support structure significantly influences the rotordynamic characteristics of the shaft train and therefore needs to be included in the assessment. Due to this impact, a good quality of the dynamic model used for the support structure is imperative. Regarding the rotor itself, the modelling is well understood and the prediction quality is excellent, not least due to the jointless welded rotor design. Numerous theoretical approaches exist for considering the complex dynamic behaviour of the support structure, all coming along with both drawbacks and opportunities. By discussing the characteristics of established approaches for modelling the support structure, the paper particularly presents an advanced theoretical approach based on a state-space representation using modal parameters. A case study of a real shaft train is shown, including a comparison of achieved results using the SDOF and the presented MDOF approach. By validating with experimental results, the excellent prediction quality of the MDOF approach is confirmed. The implementation of this approach enabled to further improve the reliability and the efficiency, which means high accuracy combined with low computation time, in performing rotordynamic assessments.

scholarly journals Study of Error Propagation in the Transformations of Dynamic Thermal Models of Buildings

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Loïc Raillon ◽  
Christian Ghiaus
Keyword(s):  
State Space ◽  
Predictive Control ◽  
Dynamic Behaviour ◽  
Transfer Functions ◽  
Fault Detection And Diagnosis ◽  
Space Representation ◽  
State Space Representation ◽  
Detection And Diagnosis ◽  
Optimal Predictive Control ◽  
Rc Networks

Dynamic behaviour of a system may be described by models with different forms: thermal (RC) networks, state-space representations, transfer functions, and ARX models. These models, which describe the same process, are used in the design, simulation, optimal predictive control, parameter identification, fault detection and diagnosis, and so on. Since more forms are available, it is interesting to know which one is the most suitable by estimating the sensitivity of the model to transform into a physical model, which is represented by a thermal network. A procedure for the study of error by Monte Carlo simulation and of factor prioritization is exemplified on a simple, but representative, thermal model of a building. The analysis of the propagation of errors and of the influence of the errors on the parameter estimation shows that the transformation from state-space representation to transfer function is more robust than the other way around. Therefore, if only one model is chosen, the state-space representation is preferable.

Wavelet-Based Damage Detection of Multi-Degree-of-Freedom Structures

2004 ◽  
Author(s):  
Yuito Hashimoto ◽  
Arata Masuda ◽  
Akira Sone
Keyword(s):  
Wavelet Transform ◽  
Damage Detection ◽  
Structural Model ◽  
Structural Parameters ◽  
Degree Of Freedom ◽  
Space Representation ◽  
State Space Representation ◽  
Damage Location ◽  
Propagation Of Singularities ◽  
Structural Responses

In this paper, a method is proposed to identify the occurrence and the location of damage from the responses of multi-degree-of-freedom (MDOF) structures based on the wavelet transform, which has the capacity to detect discontinuities and singularities. First, the propagation of singularities in responses is investigated qualitatively in order to explain how the structural responses are influenced by sudden changes of structural parameters (stiffness) resulting from damages. Next, in order to confirm the proposed method for complicated models, we evaluate the influence of sudden changes of structural parameters on responses quantitatively, and the relations between the wavelet transform and the damage location by the aid of the state space representation of the MDOF structures. Finally, laboratory-scale experiments are carried out to verify the performance and detectability of the proposed methods in a fourth story structural model installed by additional stiffness members.

Modeling, Actuation, and Control of an Active Fluid Vibration Isolator

1997 ◽  
Vol 119 (1) ◽  
pp. 52-59 ◽  
Author(s):  
M. J. Panza ◽  
D. P. McGuire ◽  
P. J. Jones
Keyword(s):  
Electrical Power ◽  
Fluid Pressure ◽  
Space Representation ◽  
Vibration Isolator ◽  
Mass System ◽  
Integral Control ◽  
Active Fluid ◽  
State Space Representation ◽  
In Series ◽  
And Control

An integrated mathematical model for the dynamics, actuation, and control of an active fluid/elastomeric tuned vibration isolator in a two mass system is presented. The derivation is based on the application of physical principles for mechanics, fluid continuity, and electromagnetic circuits. Improvement of the passive isolator performance is obtained with a feedback scheme consisting of a frequency shaped notch compensator in series with integral control of output acceleration and combined with proportional control of the fluid pressure in the isolator. The control is applied via an electromagnetic actuator for excitation of the fluid in the track connecting the two pressure chambers of the isolator. Closed loop system equations are transformed to a nondimensional state space representation and a key dimensionless parameter for isolator-actuator interaction is defined. A numerical example is presented to show the effect of actuator parameter selection on system damping, the performance improvement of the active over the passive isolator, the robustness of the control scheme to parameter variation, and the electrical power requirements for the actuator.

Non-Destructive Identification of Defects in Power Support Structure Foundations by Means of Acoustic Techniques

2014 ◽  
Vol 606 ◽  
pp. 95-98
Author(s):  
Lukasz Sadowski
Keyword(s):  
Construction Industry ◽  
Support Structure ◽  
Air Voids ◽  
Impact Echo ◽  
Acoustic Techniques ◽  
Location Depth ◽  
Concrete Elements ◽  
Non Destructive ◽  
Made In

Prefabricated power support structure foundations are made in prefabrication plants where concrete is laid in layers in moulds. The quality of the prefabricated units depends mainly on proper concrete mixture compaction, which is usually effected by means of immersion vibrators. It happens that when the vibrator is withdrawn too quickly, defects, in the form of, e.g., air voids and zones of insufficiently vibrated concrete, appear. Modern non-destructive acoustic techniques, which in recent years have been increasingly commonly used in the construction industry, are highly suitable for testing concrete elements, particularly prefabricated concrete units. The non-destructive impact-echo technique is particularly useful for determining defect location depth and for locating defective areas.

Sign in / Sign up

Export Citation Format

Share Document