System Identification Software Research Articles

The Method for Analyzing the Pitching Motion Pattern of a New Surface Unmanned Wing-sliding Boat

In this paper, a new surface unmanned wing skate (NUSV) is taken as the research object, and the free decay model test under different drafts and different initial pitch angles is completed. In the case of specially selected regular waves, typical swaying tests against waves and waves were carried out. Four mathematical models for system identification of pitch motion modes are established. Based on the system identification theory and the programming idea of the improved genetic algorithm, the NUSV pitch motion mode system identification software is written in C# language. The system identification software is developed based on experimental technology and an analysis method of ship motion patterns is developed based on the optimization theory. This paper completed the following: (1) compared and calculated the mathematical models of system identification based on four-pitch motion modes and determining their motion modes, (2) based on the results of pitch motion mode identification, the predicted values and the test results are in good agreement, which verifies the rationality of the method and the reliability of the self-compiled software, (3) analyzed the variation law of the relative value of each moment that affects the NUSV pitch decay motion with the draft and initial pitch angle, (4) analyzed the influence of the NUSV in the regular wave. The variation law of each moment of the rocking motion with the draught, wave height, and encounter period, and (5) proposed the idea of establishing a rocking motion pattern map based on the rocking test and optimal identification theory. The method and research results proposed in this paper can provide a reliable motion model for the pitch motion control of this type of boat, and provide technical support for its effective regulation of the adverse effect of the pitch on the boat’s stability. It also provides a reference for the seakeeping of this type of boat and the optimization design of the subsequent boat type. The system identification software written can also be used for system identification of the rocking motion mode of this type of unmanned boat in other directions.

Mathematical model derivation of an unmanned circulation control aerial vehicle UC2AV

This paper presents a system identification method to derive accurate mathematical models for an unmanned circulation control aerial vehicle (UC2AV) that account for the effects of circulation control (CC) on the vehicle dynamics. The X-plane flight simulator and the CIFER system identification software are utilized to first derive simulation models to verify and validate the proposed system identification methodology. This is followed by flight tests to derive mathematical models and stability derivatives for the aircraft with CC-on and CC-off. Flight tests indicate a nose down pitching moment effect induced by CC, which in turn alter the UAV trim values and dynamics. Analysis of the two sets of mathematical models reveal that CC changes the longitudinal trim values and improves the lateral maneuverability of the UAV. Verification experiments indicate an acceptable match between the derived models and UAV dynamics by calculating root mean square (RMS) error values and by quantifying the model predictive ability through calculating the Theil inequality coefficient (TIC).

Research on the Rolling Motion Mode of a SWATH-USV

This paper takes a SWATH-USV as the research object, and carries out a series of static water roll attenuation tests under different drafts and different initial roll angles. In order to study the roll motion mode of the SWATH-USV, we have established three mathematical models of the roll motion mode, and written the system identification software in C# language, based on the system identification theory and the genetic programming algorithm. Firstly, by calculating the predicted values of angular velocity under different drafts and different initial roll angles, the error between the test value and the fitted value was analyzed, and the consistency between the predicted value and the test result was found to be good, which proves the reliability of the system identification software. Secondly, through the further processing of the test data, the variation law of the torque coefficient affecting the rolling motion with the draft and the initial roll angle is preliminarily analyzed. Finally, the polynomial response surface method is applied to fit the equation containing the rolling hydrodynamic torque coefficient and the recovery moment coefficient, and the equation is found to be applicability. The analysis results and methods can provide reference for the study of the wave resistance of such USV, and provide important technical support for the subsequent optimization of the boat type.

Experimental performance analysis of an inverse dynamics CNC compensation scheme for high-speed execution of curved toolpaths

Experimental results from the implementation of an inverse dynamics compensation scheme on a three-axis CNC mill with an open-architecture software controller are presented. The scheme amounts to imposing a continuously variable displacement on the commanded toolpath, which compensates for the physical limitations (inertia and damping) of each machine axis, producing accurate execution of the prescribed toolpath. Numerical values for the dimensionless parameters that characterize the second-order inverse dynamics model are determined by feeding input and output data from machine runs into a system identification software tool. For a basic P-type controller, exact a priori solutions for the modified path geometry are possible, allowing implementation by simple alterations to the real-time interpolator. The experimental results based on a P-type controller indicate that the inverse dynamics scheme is highly effective in suppressing both feed (lag/lead) error and contour error (deviation from the desired path), even at high feedrates along strongly curved toolpaths. The scheme thus provides a practical means of achieving smooth and accurate execution of free-form paths, without appealing to more complicated “active” control strategies.

Sightline Jitter Minimization and Shaping Using Nonlinear Friction Compensation

Friction-induced sightline jitter significantly degrades the image resolution and detection range of a stabilised optical system. Therefore, any controller that can reduce jitter levels in the stabilisation sub-system will have a significant impact on overall electro-optic system performance. This article presents the results of an investigation into several friction compensation models applied to the validated model of an in-service electro-optic turret. The turret test harness, system identification software and friction measurement techniques used in the validation procedure–experimental transfer function analysis–are presented. A worst-case approach was used in setting the sensor noise and base motion acceleration levels. This test data was then used to validate a mathematical model of the turret elevation axis for use in off-line design and tuning of six friction compensation controllers. Three types of friction compensator model were investigated; a linear Kalman filter, an extended Kalman filter with a static friction model and an extended Kalman filter using a dynamic friction model. Additionally, two controller architectures were used. All six controllers were shown to significantly reduce jitter levels overall, but a new controller architecture was shown to also further reduce image degradation due to smearing.

Diagnostic system to determine the in-service life of dry vacuum pumps

A diagnostic system for dry pumps is proposed. It predicts future pump motor current from time-series in-situ measurements. The prediction system has been constructed using a data acquisition system with an online system identification software algorithm. A field test on a low pressure chemical vapour deposition (LPCVD) system for the silicon nitride process predicted large values of motor current, some of which correlated well with actual motor currents as the pump became clogged. The combined use of the predicted motor current and the stability criteria shows promise in predicting the actual service life of a dry pump.

Identifying linear models from time domain simulations

Traditionally, the linear analysis of a power system is performed by first computing a state space model, followed by the application of a suitable analysis method. However, the applicability of this approach is restricted by several practical limitations: typical power systems are represented by very large state matrices that require specialized large-scale eigen analysis programs; the program where the power system models reside does not include linearization capabilities; only time domain data is available. This article illustrates the applicability of a new system identification software program, SYSID, developed to circumvent these limitations. The program incorporates several identification techniques that allow for the computation of equivalent linear models, suitable for control design applications, from time domain simulation data. The program has been used to calculate equivalent models from simulations performed with standard stability programs, as well as from the Electromagnetic Transient Program (EMTP) simulations of detailed three-phase power systems. The equivalent systems are small and retain the modal characteristics of the original system. The identification techniques are based on various algorithms including Prony's method, transfer function fitting, and Hankel matrices. In addition to the identification algorithms, the program also includes signal processing, plotting, modal analysis functions, and basic control design capabilities to assess closed loop system performance.

Dynamic characteristics of five tall buildings during strong and low‐amplitude motions

AbstractThe objectives of this paper are to present (1) a comparison of dynamic characteristics of five buildings determined from recorded strong‐motion response data and from low‐amplitude (ambient vibration) tests, and (2) a description of the low‐amplitude ambient testing and PC‐based data‐acquisition approach that is integrated with the permanent strong‐motion instrumentation in the five buildings. All five buildings are within the San Francisco Bay area and the strong‐motion dynamic characteristics are extracted from the October 17, 1989 Loma Prieta earthquake response records. Ambient vibration tests on the same five buildings were conducted in September 1990. Analyses of strong‐motion response and low‐amplitude test data have been performed by many investigators. The present study differs from numerous previous investigations because (1) in this study, accelerometers in the five permanently‐instrumented buildings were used during the low‐amplitude testing, and (2) rapid screening of the strong‐motion response data was achieved with a concerted use of system identification software. The results show for all cases that the fundamental periods and corresponding percentages of critical damping determined from low‐amplitude tests are appreciably lower than those determined from strong‐motion response records. The data set collected during this study is a useful contribution to the data base of dynamic characteristics of engineered structures and reconfirms the differences between the dynamic characteristics identified from strong‐motion records and from low‐amplitude tests.