Dynamic Parameter Identification Research Articles

An adaptive hybrid differential evolutionary algorithm for the parameter identification of rotating machinery

An adaptive hybrid differential evolution algorithm for the dynamic parameter identification of rotating machinery is developed in this paper. Genetic algorithm (GA) is first used to reduce the range of the identification parameters to save computational time. Adaptive Cauchy and Gaussian mutations are then applied in a differential evolution algorithm (DEA) and dynamically updated during the evolutionary process according to the identification process, to obtain the global optimal solution more easily and more rapidly. Numerical studies of linear and nonlinear rotor-bearing systems are performed. The results indicate that the genetic algorithm-adaptive hybrid differential evolution algorithm (GA-AHDE) is more effective at identifying the dynamic parameters and faults of the rotor-bearing system compared to other evolutionary algorithms.

Identification of dynamic parameters of active magnetic bearings in a flexible rotor system considering residual unbalances

Active magnetic bearings (AMBs) support rotors using electromagnetic forces rather than mechanical forces. It is necessary to identify the AMB force coefficients (equivalent stiffness and damping) since they play key roles in the rotordynamic analysis. The identification is usually performed by analyzing the unbalance response. However, the presence of unknown residual unbalances reduces the identification accuracy and a rigid rotor model is only valid when the rotating speed is far below the first bending critical speed. Therefore, this paper proposes an identification algorithm to estimate the stiffness and damping parameters for a flexible rotor AMB system in the presence of unknown residual unbalances by using two independent unbalance response data sets. The proposed algorithm is first evaluated by numerical calculation for accuracy and then applied experimentally in the identification of a flexible rotor AMB system operating at speeds ranging from 3,000 rpm (50 Hz) to 30,000 rpm (500 Hz). The identification results are verified in the end.

Monitoring Bridge Dynamic Responses Using Fiber Bragg Grating Tiltmeters.

In bridge health monitoring, tiltmeters have been used for measuring rotation and curvature; however, their application in dynamic parameter identification has been lacking. This study installed fiber Bragg grating (FBG) tiltmeters on the bearings of a bridge and monitored the dynamic rotational angle. The dynamic features, including natural frequencies and mode shapes, have been identified successfully. The innovation presented in this paper is the first-time use of FBG tiltmeter readings to identify the natural frequencies of a long-span steel girder bridge. The identified results have been verified using a bridge finite element model. This paper introduces a new method for the dynamic monitoring of a bridge using FBG tiltmeters. Limitations and future research directions are also discussed in the conclusion.

Low rate error modeling of articulated heavy vehicle dynamics and experimental validation

In the automotive domain, adequate control and diagnosis rely on the use of state observers and parametric identification systems to estimate the dynamics performances of the vehicle. Unfortunately, the simultaneous use of different methods of observation, estimation and identification is not risk-free. The risks can be expressed mathematically through a problem of error accumulation, posing major risks for the vehicle and its driver (errors of detection, errors in the prediction of dangerous driving situations, vehicle instability, etc.). This paper presents a method of observation and estimation of the dynamic state and parameter identification of an articulated vehicle simultaneously at very low error rates. This method is based on the HOSM (High Order Sliding Modes) approach, with the application of the STA (Super-Twisting Algorithm). Towards to this aim, a 5-DOF (Degree Of Freedom) nonlinear dynamic model for an articulated vehicle is proposed. The model is derived by applying Lagrange’s equations. Simulation and experimental results showed that the algorithms generate accurate estimation of articulated vehicle parameters and states dynamics in real driving situations.

Bridges Dynamic Parameters Identification Based On Experimental and Numerical Method Comparison in Regard with Traffic Seismicity

The technical seismicity negatively affects the environment, buildings and structures. Technical seismicity means seismic shakes caused by force impulse, random process and unnatural origin. The vibration influence on buildings is evaluated in the Eurocode 8 in Slovak Republic, however, the Slovak Technical Standard STN 73 0036 includes solution of the technical seismicity. This standard also classes bridges into the group of structures that are significant in light of the technical seismicity – the group “U”. Using the case studies analysis by FEM simulation and comparison is necessary because of brief norm evaluation of this issue. In this article, determinate dynamic parameters by experimental measuring and numerical method on two real bridges are compared. First bridge, (D201 – 00) is Scaffold Bridge on the road I/11 leading to the city of Čadca and is situated in the city of Žilina. It is eleven – span concrete road bridge. The railway is the obstacle, which this bridge spans. Second bridge (M5973 Brodno) is situated in the part of Žilina City on the road of I/11. It is concrete three – span road bridge built as box girder. The computing part includes 3D computational models of the bridges. First bridge (D201 – 00) was modelled in the software of IDA Nexis as the slab – wall model. The model outputs are natural frequencies and natural vibration modes. Second bridge (M5973 Brodno) was modelled in the software of VisualFEA. The technical seismicity corresponds with the force impulse, which was put into this model. The model outputs are vibration displacements, velocities and accelerations. The aim of the experiments was measuring of the vibration acceleration time record of bridges, and there was need to systematic placement of accelerometers. The vibration acceleration time record is important during the under – bridge train crossing, about the first bridge (D201 – 00) and the vibration acceleration time domain is important during deducing the force impulse under the bridge, about second bridge (M5973 Brodno). The analysis was done in the software of Sigview. About the first bridge (D201 – 00), the analysis output were values of power spectral density adherent to the frequencies values. These frequencies were compared with the natural frequencies values from the computational model whereby the technical seismicity influence on bridge natural frequencies was found out. About the second bridge (M5973 Brodno), the Sigview display of recorded vibration velocity time history was compared with the final vibration velocity time history from the computational model, whereby the results were incidental.

Bearing dynamic parameters identification for a sliding bearing-rotor system with uncertainty

Bearing dynamic parameters of a sliding bearing-rotor system are important factors to the vibration absorbing characteristics. It is a valuable method to identify bearing dynamic parameters based on the unbalance response. Nevertheless, in Engineer, the unbalance parameters are uncertain due to the structural complexity and manufacturing or measuring error. Thus, developing an efficient method to estimate the bearing dynamic parameters for the uncertain unbalance parameters seems more important and necessary. This paper presented an inverse method for identifying stably the bounds of bearing dynamic parameters with uncertain unbalance parameters based on dynamic load identification method and the interval analysis .In the method, bearing dynamic parameters identification problem is formulated as the oil film force reconstruction by considering the oil film supports as rotor load boundary conditions; the midpoint oil film force and the first derivative to each uncertain unbalance parameter need be calculated with the interval analysis; the bounds of bearing dynamic parameters can be finally identified based on the interval mathematics. Finally, the efficiency and robustness of the proposed method are verified by a numerical example.

Optimization approach for identification of dynamic parameters of localized joints of aircraft assembled structures

Ground Vibration Test (GVT) is a crucial step in the design process of a new aircraft. The test involves the analysis of different load configurations that helps to understand the real structural behaviour, to certificate some extreme load cases and also to validate and improve the Finite Element (FE) model used in the design. The validation of the FE model is done by making a comparison between Frequency Response Functions (FRF) from the GVT and the FE model at some response points. Ideally, numerical and experimental results should be in agreement. This is certainly true in the case of single components but in the case of assemblies it is common that numerical and experimental results show discrepancies, especially in the case of dynamic analysis. These differences increase as the number of components in the assembly grows, because connections are usually not represented sufficiently well in the FE model. The components of these assembled structures are usually connected at a small number of points, and they can be seen as local sources of stiffness and damping. In the FE model these joints can be represented as lumped spring/damper elements in a simplified way. In this paper a formulation of the dynamic equilibrium equation employing a decoupled approach for the joint mechanical properties of an assembly is presented. Later, an optimization process based on this formulation that involves the joint properties as design variables has been developed in order to identify the joint parameters that improve the adjustment between numerical and experimental FRF in the case of harmonic excitations. The approach has been applied to a FE model that represents the connection between a segment of fuselage and the tail cone and to a real aircraft system where experimental data is available. The results achieved with this procedure are very efficient and promising.

Identification of Structural Dynamic Parameters Using Block Pulse Functions and Recursive Least-Squares Algorithm

System identification in recent years with the development of dynamic testing of structures has become one of the useful methods for structural health monitoring and damage detection and also finite element model updating. Identification of structural dynamic parameters is performed by using excitation–response data and includes physical parameters such as mass, stiffness and damping matrices and/or modal parameters such as natural frequencies, damping ratios and modal shapes. This paper presents a new method to identify the dynamical parameters of shear building based on continuous-time state-space estimation using block pulse functions and least-squares technique. Block pulse functions are a set of orthogonal functions with piecewise constant values and useful tools in analysis, identification and system science. Assuming that the input–outputs data of the original system are known, their block pulse coefficients can be calculated by numerical methods, and using block pulse operational matrix, state-space equations of dynamical system are transformed into block pulse regression equations. Based on these equations, the plant matrix is estimated using least-squares algorithm. Then, the physical and modal parameters of structure are identified based on eigenmode data of the estimated plant matrix. To prove the validity and feasibility of the proposed method, numerical simulation of a shear building which is equipped with sensors on all floors and excited by four different normally distributed random signals and an earthquake is presented. The results reveal the proposed method can be beneficial in structural identification with less computational expenses and high accuracy.

A Method of Dynamic Parameter Identification of the Joint Surface based on Acceleration and its Application

The acceleration sensor is easy to install and can be applied to the measurement of complex mechanical structure. In this paper, a new method for the identification of dynamic stiffness and damping of the unit with acceleration is proposed, the experimental verification of the method is correct, and then the effect of the vibration frequency and the normal pressure on the dynamic stiffness and damping of the joint surface is analyzed. Analytical results show that, the vibration frequency has little effect on the dynamic stiffness of the joint surface, but the damping effect on the surface is relatively strong. As the exciting frequency becomes less, the damping value of the excited frequency is smaller with the increase of the excitation frequency, and the combination with the increase of the vibration frequency and the damping value of the combined surface tends to be flat and has a nonlinear point. The influence of surface pressure on the dynamic stiffness of the joint surface is small, and the damping effect on the joint surface is relatively strong. When the surface pressure is very small, the damping value of the surface pressure is decreased fast with the increase of the vibration frequency; when the surface is with large pressure, the damping value of the combined surface tends to be flat with the increase of the vibration frequency.

Single-camera high-speed stereo-digital image correlation for full-field vibration measurement

A low-cost, easy-to-implement single-camera high-speed stereo-digital image correlation (SCHS stereo-DIC) method using a four-mirror adapter is proposed for full-field 3D vibration measurement. With the aid of the four-mirror adapter, surface images of calibration target and test objects can be separately imaged onto two halves of the camera sensor through two different optical paths. These images can be further processed to retrieve the vibration responses on the specimen surface. To validate the effectiveness and accuracy of the proposed approach, dynamic parameters including natural frequencies, damping ratios and mode shapes of a rectangular cantilever plate were extracted from the directly measured vibration responses using the established system. The results reveal that the SCHS stereo-DIC is a simple, practical and effective technique for vibration measurements and dynamic parameters identification.

A hybrid differential evolution and particle swarm optimization algorithm for numerical kinematics solution of remote maintenance manipulators

In the ITER or the future DEMO reactor systems, due to the neutron activation, the remote handling tasks such as inspection, repair and/or maintenance of in-vessel and ex-vessel components must be carried out using a wide variety of special tailored automatic manipulators. These manipulators can be designed as a pure serial articulated arm or a pure parallel mechanism, but for the sophisticated remote handling tasks requiring large workspace and high payload/weight ratio, it would be designed as a hybrid structure combined by these two mechanisms. The complex structure to obtain special remote operation makes the maintenance very time-consuming. To obtain the forward and/or the inverse kinematics of these manipulators, a global optimization method combined by differential evolution (DE) and modified particle swarm optimization (MPSO), here we call it as DEMPSO, is developed to save solution time. The general case studies focus on serial, parallel manipulators and the 10-DOF hybrid redundant serial-parallel robot designed for ITER vacuum vessel remote maintenance. The results would be extrapolated to solve the kinematic problems of the ITER or the future DEMO remote handling manipulators. The proposed optimization algorithm can also be used for the static and/or dynamic parameter identification in robot calibration systems.

A method for the identification of dynamic constraint parameters in multi-supported flexible structures

In this paper, a new method for identifying the dynamical parameters of local constraining supports such as mass, stiffness, and damping was developed through combining the measured frequency transfer functions and structural modification techniques. Since measurement noise often leads to erroneous identifications, regularization techniques have been implemented to reduce noise amplification in the inverse problem. The developed technique has been validated by numerical tests on a multi-supported flexible structure, which can be seen as an idealized electricity generator rotor shaft. The results are satisfactory for noise-free data as well as under realistic noise levels. The sensitivity of the identified support features to noise levels is asserted through a parametric study

Methods for the vibration determination and parameter identification of spacecraft with flexible structures

Methods for dynamic parameters identification and vibrations estimation of large spacecraft with flexible structures are reviewed. Different approaches to the structural deviation determination and to the vibration frequency identification by processing measurements from the onboard sensors are compared. Measuring devices and sensors for the motion estimation of large nonrigid structures are reviewed.

Identification of Dynamic Metabolic Flux Balance Models Based on Parametric Sensitivity Analysis

This paper deals with robust identification of dynamic metabolic flux model parameters based on parametric sensitivity analysis. First, the parameters in the model are ranked based on a global parametric sensitivity analysis to assess whether a subset of the parameters can be eliminated from further analysis. Then, the remaining significant parameters are identified based on the maximization of an overall parametric sensitivity measure subject to set based constraints that are derived from available data. The proposed method is illustrated on a case study of a model describing the diauxic growth of Escherichia coli in a batch culture.

A Simple Thermal Dynamics Model and Parameter Identification of District Heating Network

The existence of time delay usually results in the mismatch between the heat source output and the users’ heating load. In the research, a dynamic model is built to predict the supply water temperature in the substation and the heat loss from the heat source to the substation by identifying the time delay, α and β. α and β are parameters obtained by Regression. α is determined by the length of pipeline, velocity, heat transfer coefficient, etc., β is determined by outdoor air temperature besides those above elements. In the feasibility and prediction ability analysis of the model, two groups of tested supply water temperature in the substation are fitted well with the predicted supply water temperatures, respectively.Results show that the proposed method can improve the prediction accuracy of the supply water temperature in the heating substation, and the prediction error of the supply line heat loss can be restricted within -10%-2%. This indicates that the model have great ability in the temperature prediction and heat loss calculation.

Fault actuators detection based on inputs-outputs data mapping: application to a robot manipulator

This paper deals with a fault estimation algorithm to reconstruct faulty inputs of a process under actuators faults. This approach is based on a generic model with outputs/inputs data mapping to reconstruct the faulty inputs. The key idea consists on dynamic parameters identification of this generic model in real time for abrupt and intermittent faults. To apply this approach, these dynamic parameters are estimated basing on the recursive least squares solution obtained from the sampling of the dynamic model along a closed loop tracking trajectory. Indeed, the control loop requires information about the state derivative of the outputs system. For this aim, a dynamic gains sliding mode differentiator is introduced. By using measured signals, the proposed approach is validated on a bi-axis robot manipulator to evaluate its usefulness on actuators faults detection.

Fault actuators detection based on inputs-outputs data mapping: application to a robot manipulator

This paper deals with a fault estimation algorithm to reconstruct faulty inputs of a process under actuators faults. This approach is based on a generic model with outputs/inputs data mapping to reconstruct the faulty inputs. The key idea consists on dynamic parameters identification of this generic model in real time for abrupt and intermittent faults. To apply this approach, these dynamic parameters are estimated basing on the recursive least squares solution obtained from the sampling of the dynamic model along a closed loop tracking trajectory. Indeed, the control loop requires information about the state derivative of the outputs system. For this aim, a dynamic gains sliding mode differentiator is introduced. By using measured signals, the proposed approach is validated on a bi-axis robot manipulator to evaluate its usefulness on actuators faults detection.

A Flat Design and a Validated Model for an AUV Reconfigurable Magnetic Coupling Thruster

Reconfigurable Magnetic Coupling Thruster (RMCT) is an enabling technology for achieving vectorial thrust on AUVs. This allows us to dispose of dynamic, compliant, and secure propulsion to enhance their agility for demanding locomotion tasks. RMCT can generate and control a thrust vector by redirecting its propeller through the compliance of the magnetic coupling and therefore achieve thrust vectoring for AUVs. In this paper, a new design of RMCT is presented. This new prototype uses a flat geometry magnetic coupling for a better AUV full integrability. The new design provides some additional advantages with regard to its predecessor (spherical RMCT); namely, construction simplicity and better torque transmission. The first characteristic is derived from its flat shapes, which makes it easier to manufacture (cubic magnets) and to isolate (planar air gap between rotors). The second characteristic is due to the fact that now both parts of the magnetic coupling can store magnets (increasing the maximal transmitted torque). This paper proposes a thruster dynamics model, a magnetic coupling model, and shows the use of a dynamic parameter identification method based on algorithms used for robotic manipulators. The validity of the dynamic model and identified parameters is then analyzed by means of experimental tests.

Efficient model updating of a multi-story frame and its foundation stiffness from earthquake records using a timoshenko beam model

We present a new approach to estimate the dynamic stiffnesses of soil-foundation systems using earthquake-induced response signals recorded on multi-story buildings with sparsely instrumentation. Identification of soil-foundation dynamic stiffness parameters from real-life data, especially earthquake-induced response signals, is arguably one of the most challenging problems in structural/geotechnical earthquake engineering. This is because the said parameters are frequency-dependent, and the non-stationary input excitation is not measurable due to soil-structure interaction effects. It is possible to identify these parameters using recently developed blind source separation techniques, provided that a finite element model of the superstructure is available. However, developing and updating a finite element model is usually a laborious undertaking, and its success strongly depends on the spatial density of measurements. In the present study, we offer a new method that is based on the use of a Timoshenko beam model to represent the superstructure. In this method, key parameters of the Timoshenko beam model – and those of its soil-foundation system – are adjusted through a systematic procedure, until the systems’ overall (flexible-based) modal properties match those identified from real-life data. The proposed method is robust against sensor sparseness, and yields accurate results even if the foundation rocking is not measured. The proposed procedure is first verified using a synthetic problem, and subsequently applied to real-life data recorded at the Millikan Library building, which is located at the Caltech campus in Pasadena, California.

Road and Railway Traffic Seismicity Effect Comparison on Historical Building in Slovakia

The road and the railway traffic generate material and immaterial emissions. The immaterial emission produced by traffic is divided to the noise and the vibrations. All these aspects attacking the environment should to be assessed. For the assessment the national and international standards can be used. This paper contains only the vibration assessment and the comparison of the dynamic parameters influence in this process. The heritage buildings have more conservative criteria as another building. This approach is performed via experimental and numerical study and identification of the basic dynamic parameters. It is presented on two case studies of important historic buildings in Modra and Žilina (Slovakia). For both case studies buildings, the FEM (Finite Element Method) numerical models were created. The modes of the natural vibration and natural frequencies were obtained as the relevant results from numerical models. These parameters are very important for this type of assessment. For the FEM models the Scia Engineer were used as the numerical software system. The experimental measurements were realised for FEM model verification. Also these measurements were used for the assessment according Slovak standards. These models can be tuned based on the experimental measurements. The tuned FEM models can be used for the further extrapolations. The main part of the investigation was to compare traffic seismicity effect on the historical buildings. Both buildings were assed in the frequency and time domain. The comparison of the traffic seismicity effects was realised also in frequency and the time domain. It is necessary to taking to account this assessment for the heritage buildings.