Practical Identification Method Research Articles

A New Method for Identification and Modeling of Process Damping in Machining

Although process damping has a strong effect on cutting dynamics and stability, it has been mostly ignored in chatter analysis as there is no practical model for estimation of the damping coefficient and very limited data are available. This is mainly because of the fact that complicated test setups were used in order to measure the damping force in the past. In this study, a practical identification and modeling method for the process damping is presented. In this approach, the process damping is identified directly from the chatter tests using experimental and analytical stability limits. Once the process damping coefficient is identified, it is related to the instantaneous indentation volume by a coefficient which can be used for different cutting conditions and tool geometries. In determining the indentation coefficient, chatter test results, energy, and tool indentation geometry analyses are used. The determined coefficients are then used for the stability limit and process damping prediction in different cases, and verified using time-domain simulations and experimental results. The presented method can be used to determine chatter-free cutting depths under the influence of process damping for increased productivity.

Nonlinear Model Identification for Temperature Control in Single Wafer Rapid Thermal Processing

Single wafer rapid thermal processing (RTP) has become one of the key technologies in semiconductor manufacturing due to its faster wafer processing with reduced thermal budget and precise control of processing conditions. As the standard size of the silicon wafer grows and integration of integrated circuits increases, better control to improve the processing time, uniformity, and repeatability of processing is required. In RTP, identification and control are complicated because of high nonlinearity, drift, and time varying nature of the wafer dynamics. Physical models for the wafer dynamics have been available, but they are not utilized fully for identification and control. Here, based on a physical model of wafer, a practical identification method and an analytic linearizing control method are proposed.

Identification of the Linear Part of a Plant Having Input Nonlinearity Using a Limit Cycle Test

This paper presents a practical identification method of the linear part of a plant which has nonlinearity in its input. A Hammerstein-type model is used for the plant model and only the linear dynamic part is identified independently of the input nonlinear element by restricting the manipulated variable to take only two values during the identification experiment. The identification signals are generated using a kind of limit cycle test modified to produce fractional harmonic components in the signals. A second order lag plus an all-pass filter is used for the linear model and its parameters are calculated to fit the model frequency responses to the ones obtained by the limit cycle test at two frequencies. A numerical example is presented and adequateness of the model structure is discussed.

Process Identification by Using a Limit Cycle Test with Fractional Harmonics

A limit cycle test is discussed from the viewpoint of the plant identification, and a practical identification method using the modified limit cycle test is proposed. The limit cycle test is a convenient way to estimate some information of the plant dynamics but only few characteristics are obtained by the conventional way. In this work, the limit cycle test is modified so that the manipulated variable and the process value may contain fractional harmonics, and the plant model is estimated with those fractional harmonic components as well as the basic components. The use of the fractional components enables us to identify the plant model accurately in a noise environment and to handle more sophisticated model: a second order lag plus all-pass filter type one. An experimental example of a thermal plant is illustrated to show the effectiveness of the proposed method where an LQI controller is designed with the identified model of the plant.

System Identification, Modelling and Control of an Autonomous Underwater Vehicle

Autonomy of an underwater vehicle is in the main attributable to the design of a suitable guidance and control system. Generally, the control system is developed and tested first in simulation studies using a model of the vessel to gain confidence in the approach being adopted. Therefore, plant identification is imperative to gain insight about the system. This paper is concerned with a practical system identification (SI) method in order to obtain a model of an autonomous underwater vehicle (AUY) using input output data as opposed to painstaking mathematical modelling techniques. A model of the AUV is developed using SI and tested in simulations using a linear quadratic Gaussian (LQG) controller. Modelling and simulation results are presented.

Traveling-Wave Modal Identification Based on Forced or Self-Excited Resonance for Rotating Discs

Modal testing of rotating systems, such as a rotating disc interacting with a stationary restraint, is considered in this paper. A practical and effective identification method called the artificial damping method (ADM) is proposed to identify the traveling-wave modes for rotating discs based on forced or self-excited resonant responses measured using two displacement probes. The ADM procedure can handle extremely noisy systems and does not require excitation information. The method is suitable for the detection of self- excited modes that may occur during operation. Additionally, this procedure can be effectively used to identify modal parameters for large-scale structures and other rotating systems with a relatively low level of excitation energy

A concept of designing cheater identification methods for secret sharing

A new concept of designing cheater identification methods for secret sharing is proposed in this paper. System constructors can apply digital signature algorithm under this proposed concept to construct a practical cheater identification method which is both efficient and simple. It is convenient for a system which already contains a digital signature algorithm and needs to detect or identify cheaters. The security of the constructed method is dependent on the selected digital signature algorithm. The bit length of the public value of the cheater identification method which follows the proposed concept is independent on the total number of the participants in the secret sharing scheme. System constructors do not need to change the public value when he wants to include new participants into the system or to remove certain participants from the system. There exist efficient and secure commercial products for digital signature algorithm such as RSA. The proposed concept can be implemented in computer systems.

Identification of Pneumatic Actuator Using Wavelet Transform.

Signal processing of multifrequency channel decompositions should be possible in the near future because signal processing for each frequency channel is easy. However, a difficult problem, i.e., aliasing, exists when the signal is reconstructed. The wavelet transform technique has a special property, i.e., that the signal can be reconstructed uniquely after multifrequency channel decompositions. In this study, a new practical identification method, in which the wavelet transform technique is used, is proposed. This proposed method is used to identify a one degree of freedom pneumatic robot which is developed in this study. The applicability of the proposed method is confirmed by the experimental results.

New Measurement Method for Motion Accuracy of NC Machine Tools by Link Mechanism. 2nd Report. Identification Method for Errors of Measurement Instrument.

For application of the LM measurement device proposed in our first report which has a high measurement accuracy throughout the working sphere, it is necessary to identify the errors of the LM device itself and compensate for the influence of these errors on the measurement results. In this paper, a simple and practical identification method for this purpose is developed. First, an accurate model containing the effects of the mechanism and the sensor errors in the LM measurement instrument is developed and a simple approximation equation with sufficient accuracy for application is derived from this model. Next, the identification method is proposed based on the approximation equation. The experimental results of identification and measurement for several motion trajectories with a machining center are shown. The validity of the proposed method is well confirmed by these results.

Identification of Model Uncertainty using Decimation with Application to Large Space Structure

In this paper, a new and practical identification method for the model uncertainty is proposed. The identification method is based on the ordinary least-squares identification method in cooperation with the decimation. The key idea of the proposed method is a frequency division by the decimation. The frequency band of the identification object is divided into two parts, that is, one corresponds to the nominal model and the other corresponds to unmodeled dynamics. Effectiveness of the method is examined through actual data that is collected by identification experiments of a ground-based test model for a large space structure (LSS).

Parameter expressiop for modelling and inverse dynamics problems of manipulators

For improving the ability of manipulators or developing CAD systems for manipulators, it is necessary to develop a practical identification method for manipulators and an effective computational method for inverse dynamics problems. We have already developed a practical identification method for serial manipulators, and Luh et al. have proposed an effective algorithm for inverse dynamics problems, called Luh's algorithm in this paper. However, our method cannot be coupled with the inverse dynamics algorithm because the parameter expressions which suit our method are different from those which suit Luh's algorithm. Therefore, we must treat the above problems as different problems. In this paper, we introduce the concept of virtual parameters in order to treat both problems in a unified manner. First, we discuss the parameter form suited for each problem. Then we define the virtual parameters using the results of the identification problem to solve the inverse dynamics problem.

Comparative protein patterns of three thermophilic nonpathogenic Naegleria isolates and two Nageleria fowleri strains by isoelectric focusing

The protein composition of the soluble cellular extracts of 5 different strains of thermophilic Naegleria, comprising 2 pathogenic N. fowleri and 3 nonpathogenic Naegleria isolates, have been studied by isoelectric focusing on polyacrylamide gels. The two pathogenic N. fowleri strains, although originating from very different sources, show an identical protein pattern, and are easily differentiated by several characteristic bands from the group of thermophilic nonpathogenic Naegleria sp. The latter, closely related to one another, correspond to the new species N. lovaniensis. Besides being a practical identification method for Naegleria fowleri, isoelectric focusing seems to be an excellent method for investigating the taxonomy of the genus Naegleria.

Successive Identification of Volterra Type Nonlinear Multi-Input-Output System and Its Application to Parameter Estimation

A simpler practical identification method of nonlinear system represented by discrete Volterra functional series is proposed. Discrete Volterra kernels, divided into group corresponding to each sampling time, are determined from a set of simultaneous linear equations. The sets of simultaneous linear equations are solved one by one, applying the solution of each step to solve the next set of equations having a larger number of unknowns. Thus, each identification procedure reduces the size of matrix to be dealt with and assures an accurate system identification with the combination of least squares estimation method in the presence of noise on output signals. Furthermore, as its application, a parameter estimation method using a part of the solution of linear equations is proposed.

New Methods of Controlling Nonlinear System Represented by Discrete Volterra Functional Series

New methods of controlling nonlinear system represented by discrete Volterra functional series are proposed. These methods make it possible to eliminate the effect of disturbance on the desired output by using .explicit input terminals, whose values can be easily set. For this purpose, the system is first identified by a simpler practical recurrent identification method and its inverse system is synthesized to reproduce input functions. Then, the control systems with inverse system and dynamical compensator are built to eliminate the contribution of the disturbance to the output and realize the desired output.

An Identification Method for a Combined Wiener-Hammerstein Filter Describing the Encoding Part of the Cochlear System

The encoding part of the cochlear system can be described by a Wiener-Hammerstein network in which the nonlinear part is a nomemory nonlinearity. If a cross-correlation function is measured across this system by using a zero mean Gaussian test signal, the impulse response of the combined linear parts of the system will be found. This property has been used to develop a practical identification method suitable to determining the static characteristic of the nonlinearity. In addition, the parameters of the linear parts of the network can be determined if the order of one is a priori known. The method is simple and the nonlinearity can easily be determined interactively. Moreover, some further aspects of the problem will be discussed: the application of cross-regression functions to determine directly the parameters of the system and a criterion function based on cross-dispersion functions in order to find the shape of the nonlinearity automatically.