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Anomaly detection is important in many fields. Especially when dealing with large-scale, complex and dynamic data, traditional methods based on fixed rules or thresholds are often inadequate. In order to improve the accuracy and reliability of anomaly detection, this paper proposes an improved soft computing anomaly detection model based on independence criterion and maximum entropy clustering algorithm. Through experimental analysis, the average adjusted Rand index of MDMEC on Iris data set reached 0.92, which was 0.61, 0.54 and 0.43 higher than that of FCM, DiFCM and MFCA algorithms, respectively. In addition, in the standardized mutual information comparison, the MDMEC algorithm also showed a higher value of 0.91, while the FCM, DiFCM and MFCA algorithms showed 0.57, 0.88 and 0.62, respectively. In terms of parameter sensitivity, the MDMEC exhibited the highest sensitivity with an average accuracy value of over 0.8, indicating its ability to be accurately applied in soft computing anomaly detection. The innovation of this research lies in the combination of the independence criterion and the maximum entropy clustering algorithm to construct a new anomaly detection model. By adjusting the model parameters, the model can better adapt to different data sets and practical application requirements, and improve the practicality and scalability of the model. Compared with other similar anomaly detection techniques, the research method not only considers the data independence, but also makes use of the advantages of cluster analysis to provide a more comprehensive and accurate solution for anomaly detection. The main contribution of the research is to construct a new anomaly detection model by combining the independence criterion with the maximum entropy clustering algorithm. This study comprehensively considers the independence of data and uses cluster analysis to provide a more comprehensive and accurate solution for anomaly detection.

For PM motor with external rotor, the electromagnetic force wave acting on the surface of the permanent magnet by the air gap magnetic field is the main cause of its electromagnetic vibration. In this paper, an optimization method based on parameter sensitivity for electromagnetic force wave of fractional slot surface-mounted PM motor with external rotor is proposed. Firstly, taking a fractional slot surface-mounted PM motor with external rotor as the research object, Latin Hypercube Design (LHD) is carried out with six structural parameters as design variables, including pole arc coefficient, notch width, air gap length, permanent magnet thickness, tooth width and slot depth, and the parameter sensitivity of different design variables to the average torque and the main radial electromagnetic force wave amplitude is analyzed. Secondly, based on the experimental results of Latin Hypercube Design, a mathematical approximation model is established by using radial basis function neural network method. Then, with the aim of improving the average torque and reducing the amplitude of the main radial electromagnetic force wave, neighborhood cultivation genetic algorithm is applied to optimize the structure of the motor. Finally, the optimized motor scheme is simulated by finite element simulation to verify the feasibility and accuracy of the proposed method.

A dual-excited synchronous generator (DESG) with two field windings on the rotor has better dynamic characteristics and high stability. However, the realization of the function needs a reasonable excitation control strategy. In this article, a power tracking excitation control (PTEC) is proposed to improve the operating performances of the DESG. The dynamic processes of a 300-MW DESG with the PTEC are calculated after the disturbance of the torque and reactive power by the time-stepping finite element model, and the results are superior to those adopting the traditional dual-channel excitation control. To further improve the dynamic characteristic of the DESG, the sensitivities of the control parameters of the PTEC to the dynamic characteristic indices are studied. The fuzzy control rules are built based on the sensitivity analysis results and the control parameters are optimized by the fuzzy control method. It revealed the variation laws of the optimized control parameters along with the active and reactive power deviations and their variable rates. The results show that the DESG adopting the optimized control parameters has better dynamic characteristics. The study can provide the theoretic basis for enhancing the system damping effect and suppressing the system oscillation. [ABSTRACT FROM AUTHOR]

The performances of heuristic algorithms are highly dependent on the parameters used, and usually difficult to determine subjectively. Thus, how to balance the relations between the qualities of the solutions and the values of the parameters has been a hot and lasting topic in the field of optimization research. This article presented a statistical method to estimate the efficient parameter values of three alternative neighborhood search techniques of simulated annealing when applied to forest spatial harvest scheduling problems, as an example. The neighborhood search techniques included: the conventional version of simulated annealing (Method1), and the swapping version (Method2) and the changing version (Method3) of 2-element optimization (2-opt) moves. Results indicated that the performances of different neighborhood search strategies highly depended on the problem size, in which the superiorities of Method2 increased from about 10% for smaller cases (400 units) to approximately 80% of larger cases (>3600 units) when compared the objective function values with Method1 and Method3. The efficient parameter values of the cooling rate (CR), the number of iterations per temperature (Ntem), and the number of iterations used for generating initial solution (Nsol) could be estimated using polynomial functions with the number of units, while the initial temperature (IT) should be estimated using exponential function, where the determination coefficient ($R^{2}$ ) of the fitted functions were all larger than 0.60 [except for Nsol and CR of Mehod1 ($R^{2}=0.32$ and 0.42), CR of Method2 ($R^{2}=0.20$ )]. The number of satisfactory solutions all increased linearly ($R^{2} > 0.85$ ) with the number of units, while the solution efficiency decreased linearly ($R^{2} > 0.30$ ). The verifications of two extra grid datasets indicated that the parameter optimization methods were valid.

Ethylene epoxidation reactor is a kind of critical equipment in an oxidation unit. Due to the complex coupling effect of the extreme operating environment of high temperature, high pressure and potential risk factors, the reactor tends to work abnormally under the impact of parameter fluctuation, and temperature runaway incident may occur and cause severe loss. For studying the influence of parameter fluctuation on ethylene epoxidation reaction process and preventing temperature runaway accidents, physical modeling is performed firstly in this paper to acquire the chemical reaction mechanism therein and confirm the operation parameters which should be focused. The unsteady simulation of the operation process under normal situation has been performed. On such basis, a test of single-factor effect is performed to analyze the impact of parameter fluctuation on the temperature balance and operation efficiency of the reactor. Comparison analysis has been carried out between the simulation data acquired according to the established model and real production data, and it was found that the result is consistent. The analysis result indicates: higher ethene concentration, oxygen concentration, feed flux, feed temperature, drum temperature, operating pressure or smaller porosity may improve bed temperature and accelerate reaction rate; therein, ethene concentration, oxygen concentration, drum temperature, and porosity are operation parameters that need special monitoring. Based on the risk analysis of the ethylene epoxidation reactor and the simulation of the impact of parameter fluctuation, this paper studies the cause of the reactor's temperature runaway to provide a technical basis for the forecast of reactor's temperature runaway, early warning, and high-efficient operation of equipment. Model established based on abnormal condition parameters fluctuation, can contribute to early warning reactor temperature runaway, revealing the influence mechanism of parameter fluctuation for the reaction system, monitoring reaction process, eliminating temperature runaway in the bud, and providing theoretical and technical basis for petrochemical equipment fault diagnosis, accident prevention and control and safely long-time running.

This article presents a general-purpose full-speed sensorless control scheme for interior permanent magnet synchronous motors (IPMSMs). By applying a quadratic extended back electromotive force (QBEMF) model, the injection-based and model-based position estimations can be combined into a universal sensorless control strategy for the full-speed operation. At low speed, the QBEMF model acts as a self-demodulator that can extract position information from arbitrary high-frequency currents without using digital filters. Therefore, it is suitable for any type of injection signals and can eliminate the adverse effect of filters. When the injection is removed at high speed, the same QBEMF model can still be used for position estimation, thereby solving the conventional transition issue from low-speed to high-speed sensorless control. In consequence, a unified algorithm is designed to achieve arbitrary injection for low-speed sensorless control and seamless transition across full-speed region. The proposed scheme is hence simpler and more effective compared to conventional full-speed sensorless methods. Finally, the feasibility of the proposed estimation algorithm is verified for a 15-kW IPMSM drive. [ABSTRACT FROM AUTHOR]

There is a strong demand for the research of electric vehicles (EVs) in automotive industry, because of an increased concern of the energy depletion and environmental pollution problems caused by oil-fueled automotive. The traction motor drive system is one of the core components of EVs, and a motor with superior dynamic performance and high efficiency could significantly reduce energy consumption and improve riding comfort of EVs. Therefore, in order to achieve high dynamic performance and high efficiency of permanent magnet synchronous motor (PMSM), a multi-objective optimization design method for PMSM based on the artificial bee colony algorithm was proposed in this paper. First, based on the magnetic field analytical model of PMSM, the analytical expressions of the key parameters were deduced, namely, mechanical time constant and electrical time constant. Second, the efficiency and electrical and mechanical time constant were defined as optimization objectives. Third, the efficiency and dynamic performance of the original motor and optimized motor were compared applying the finite-element analysis. Furthermore, one prototype machine was manufactured according to the results of optimization. The dynamic performance and efficiency of the prototype had been tested. The experiments show confident results that the efficiency increased about 1% and the mechanical time constant reduced to 31.4% of initial value.

A new form of nonlinear control scheme is presented in this brief where the concepts of feedback linearization and adaptive control schemes are combined together to design an adaptive partial feedback linearizing controller. The newly proposed scheme is exercised on a single machine infinite bus (SMIB) power system in order to design its excitation controller in order to eliminate the parameter sensitivity problems of the feedback linearization scheme. The SMIB system is first linearized using the partial feedback linearization technique and the parameters appearing in the feedback linearized model are estimated using the adaptive control scheme. The proposed adaptive partial feedback linearizing excitation controller of the SMIB system uses the estimated values of parameters. The stability of the SMIB system is also analyzed using the Lyapunov stability theory while using the proposed scheme. Simulation studies are carried out to demonstrate the effectiveness of the proposed control scheme over an existing partial feedback linearizing scheme. [ABSTRACT FROM AUTHOR]

Identifying the air-gap flux is a prerequisite for realizing the decoupling control between the air-gap flux and torque in an electrically excited synchronous motor (EESM) vector control system. For the nonlinear problem of EESM, the frequency response function method is introduced to analyze the air-gap flux voltage and current models’ sensitivity to the motor parameters in this article. A dynamic air-gap current model for EESM based on the equivalent reaction inductance is proposed to solve the parameter dynamic-variant problem caused by the nonlinear magnetic distribution of the EESM. Meanwhile, the comparative analysis of effectiveness caused by linear and nonlinear flux identification errors in the hybrid air-gap flux model of vector control system is carried out. The effectiveness of the nonlinear dynamic model has been verified by simulation and experimental results, which shows its excellent control performance. [ABSTRACT FROM AUTHOR]

A robust model-predictive direct-speed control (MP-DSC) for the surface-mounted permanent-magnet synchronous motor (SPMSM) drives is proposed in this article. First, MP-DSC based on direct voltage-selection cost function is introduced. Then, a sliding-model full parameter disturbances and load observer (FPLO) that can simultaneously estimate electrical parameter disturbances, mechanical parameter disturbances, voltage reconstruction error, motor speed, and load torque is proposed. Thus, the load torque observer in the conventional MP-DSC method is eliminated. Then, the MP-DSC+FPLO method is presented, in which the output of the proposed FPLO is used to compensate for the predicted reference voltage error. The simulation and experimental results show that the proposed method is robust to the disturbance of parameters and load. [ABSTRACT FROM AUTHOR]

A position sensorless operation of a doubly-fed induction generator (DFIG) is desired from considerations of cost, maintenance, cabling, and reliability. This article proposes two stator flux based model reference adaptive observers (SF-MRAOs) for the estimation of the rotor speed and position in a stand-alone DFIG. The cross product of the reference and estimated stator flux linkage vectors is fed as controller input in the existing method, thereby, making the observer model nonlinear. The first proposed method, which is based on notch filtering, offers a performance comparable to that of the existing method while reducing the number of voltage and current sensors required. The second proposed method linearizes the error input to the controller, making the controller design straight forward, and also leading to superior performance than the existing methods. The linearized SF-MRAO is shown to work successfully with good dynamic performance in vector control of a stand-alone DFIG. This article also shows that the proposed linearized SF-MRAO can be employed for obtaining the rotor current angle in direct voltage control of a stand-alone DFIG. Simulation and experimental results are presented from a laboratory prototype of a 10-hp DFIG coupled to a squirrel-cage induction motor. The sensitivity of the performance of the proposed linearized SF-MRAO to variations in machine parameters is also studied theoretically and experimentally. [ABSTRACT FROM AUTHOR]

This article presents an ac voltage controller that can operate under a wide range of loads, thanks to its high robustness to plant-model variations. A robust voltage controller is required in a droop-controlled inverter that operates connected to a grid or in island mode with other generators. In such modes of operation, the voltage source converter can experience large load-impedance variations depending on the number of parallel generators or the grid impedance value. Concerning the controller performance, the transient response is improved by selectively minimizing the output impedance of the system at the frequencies that typically contain the largest components of the output current. Complete harmonic control is achieved due to its zero output impedance at a set of design-selected frequencies. The proposed controller only measures the output voltage, and it contains a single-loop structure that uses all available bandwidth. In addition, a fast converter-current estimator provides protection against faults and inrush output currents. The design process only requires, as input parameters, the LC filter values, the sampling frequency, and a set of harmonics where load-current circulation is expected. [ABSTRACT FROM AUTHOR]

For early risk assessment in the design of cabling in an aircraft, as well as cable bundle optimization, efficient crosstalk estimations, and dependency of crosstalk with respect to designable parameters are required. A low-frequency technique for analyzing crosstalk in multiconductor transmission lines is presented. The result of this analysis is a closed-form expression for crosstalk in a specific cabling configuration. The technique has been validated via measurements and is used in two examples comprising two wire pairs close to a ground plane and in free space. Low-frequency closed-form expressions for near-end crosstalk are derived for both situations, which directly relate any designable parameter to crosstalk levels. Moreover, these expressions clearly show differences between the cases with and without a ground plane. Specifically, with the ground plane, the decrease in crosstalk when doubling the separation distance is 24 dB for pairs close to the ground, while it is 12 dB in free space. The closed-form expressions are utilized to create an overview of sensitivities of crosstalk to all designable parameters for both configurations. Finally, the low-frequency approximations of the chain parameters are applied to more complex nonuniform transmission lines, yielding more than 20 times faster computations when compared with complete MTL simulations. [ABSTRACT FROM AUTHOR]

For field-oriented control (FOC) of induction motors, accurate estimation of flux is important. Among the various flux estimation methods, the voltage model flux observer exhibits superior performance in situations where there is detuning of rotor parameters, such as rotor resistance and mutual inductance, because this model is robust to the detuning of these parameters. However, it is difficult to implement the voltage model, which includes pure integration, because of the dc saturation and dc drift problems. A number of methods have been developed to overcome this problem, including the Gopinath model flux observer, which can completely solve these problems. However, this model has a critical weakness in terms of parameter sensitivity in the mid-speed region because of the property of its characteristic function. In this paper, an analysis of parameter sensitivity of existing flux observers is discussed. A method for a voltage model flux observer design based on the Gopinath model is presented. Through an analysis of the characteristic function of the observer, the voltage model is designed. Finally, the operation of the proposed method is proven by simulations and experiments. [ABSTRACT FROM AUTHOR]

Due to its special partitioned stator structure and multi-excitation with two different types of permanent magnet, a new double-stator multi-excitation flux-switching machine (DSME-FSM) has advantages of high torque density, wide speed range, and low cost. For this kind of machine with complex structure, in order to realize the optimization accurately and efficiently, a multi-objective comprehensive optimal design method considering the different weights of the design objectives is presented based on parameters sensitivity analysis and genetic algorithm optimization in this paper. The parametric model of the machine is built up, and a trade-off objective function considering the different weights of the design objectives is defined. The key size parameters with strong sensitive are selected through parameters sensitivity analysis and then optimized by using the genetic algorithm method. The performance comparison between the initial and the optimized machines verifies the proposed optimization method. The anti-demagnetization property and the flux-weakening capability for a wide-speed range operation are also analyzed, which further confirms the DSME-FSM an interesting candidate for EV propulsion. [ABSTRACT FROM AUTHOR]

Conventional resonant controllers (RCs) are commonly used in the current control of grid-tied converters with LCL filter due to their advantages, such as zero steady-state error at both fundamental sequences, easy design process, and straightforward implementation. Nevertheless, these traditional solutions do not permit to place the closed-loop poles of the system in convenient locations when dealing with a fourth-order plant model such as the LCL filter plus the computation delay. Therefore, the reference tracking and the disturbance rejection are deficient in terms of transient behavior and depend on the LCL filter. Furthermore, an additional active damping method usually has to be designed in order to ensure stability. This paper presents an enhanced current RC with stable and fast response, negligible overshoot, good disturbance rejection, and low controller effort for grid-tied converters with LCL filter. The developed solution uses a direct discrete-time pole-placement strategy from the classical control theory (using transfer functions), involving two extra filters, to enhance the performance of the RC. In this manner, the complexity of state-space methods from modern control theory is avoided. Simulation and experimental results are provided to verify the effectiveness of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

While having various desired merits of high structural robustness and thus reliability, high thrust density, low fabrication cost, and so on, the stator-magnet moving-iron transverse-flux linear oscillatory machine suffers from high consumption of rare-earth magnetic material (high material cost) and heavy flux leakage at the stator outer region (underutilization of permanent magnets). To mitigate the demerits, a novel stator-magnet moving-iron transversal-flux hybrid-flux-path linear oscillatory machine (SMTHLOM), with additional back iron and auxiliary radially magnetized ferrite magnets, is proposed in this paper. The topology and operational principle of the proposed SMTHLOM are explained in detail. The 3-D finite-element analysis is introduced to investigate the sensitivities of main structural parameters, which enables the selection of optimal dimensions. Based on a set of comparison rules, a comprehensive comparison was conducted between these two topologies on various key indicators, such as the back electromotive force, thrust, and thermal distribution. The simulation results show that the SMTHLOM is low cost and small stator outer flux leakage, and thus is more suitable for some applications, e.g., fridge compressors, requiring low cost and high thrust density. [ABSTRACT FROM AUTHOR]

Traditionally, the current control of grid-tied converters with LCL filter is based on proportional-resonant or proportional-integral controllers, which often need an additional active damping method to achieve stability. These solutions do not permit to place the closed-loop poles in convenient locations when dealing with such high-order plants. This constraint results in degraded reference-tracking and disturbance-rejection responses. On the other hand, the existing methods based on direct pole placement or other modern control strategies, do not control with zero steady-state error both positive and negative sequences of the grid current, but only the positive one. This limitation is undesirable under unbalanced grid conditions. This paper presents a current controller for grid-tied converters with LCL filters based on direct discrete-time pole placement. The proposed controller makes it possible to control both positive and negative sequences of the grid-side current with zero steady-state error. Contrarily to the classical resonant controllers, the closed-loop poles can be placed in convenient locations, yielding a fast response with negligible overshoot and low controller effort. Moreover, no additional damping methods of the resonance are necessary to achieve stable operation, regardless of the switching frequency and LCL filter used. Simulation and experimental results that validate the proposal are presented. [ABSTRACT FROM PUBLISHER]

This paper proposes a simple model predictive direct power control (MP-DPC) of single-phase pulsewidth-modulated rectifiers with constant switching frequency using modulation function optimization. The instantaneous active and reactive power theory for single-phase converters is discussed, on the basis of a second-order generalized integrator. The modulation function is resolved from the cost function of the MP-DPC scheme. The relationship between the instantaneous powers and ac-side inductance mismatch is discussed. The inductance mismatch has an effect on the reactive power, but not effect on active power. The quantitative expression of reactive power caused by inductance mismatch is shown and verified in the experimental test. An inductance parameter online estimation scheme is proposed to eliminate its effect on reactive power. Compared with the conventional proportional-integral-based instantaneous current control scheme and finite-control-set MP-DPC scheme, the proposed MP-DPC can provide these advantageous features: lower current harmonics and total harmonic distortion components, faster dynamic response, fewer adjusted parameters, and zero steady-state error. In addition, the proposed MP-DPC is free of the weighting factor selection in cost function. The effectiveness of the proposed MP-DPC scheme is verified by experimental results. [ABSTRACT FROM AUTHOR]

This paper is dedicated to exploring real-time parameter identification approaches and their integration with deadbeat-direct torque and flux control (DB-DTFC) without additional torque ripple. Using the voltage model at medium- and high-speed ranges, DB-DTFC is insensitive to parameters. Performance degrades at low speeds with the rotor time constant errors, because the current model is utilized for flux linkage estimation. Two different real-time parameter estimation approaches are developed, including a flux observer-based model reference adaptive system (MRAS) and a pulsating flux injection-based method. Both are experimentally evaluated for how well they mitigate DB-DTFC performance degradation at low speed. For the MRAS-based method, the fundamental components are used for parameter convergence, which does not induce additional torque ripple. For the injection-based method, traditional d-axis pulsating voltage vector injection used in indirect field-oriented control (IFOC) yields significant torque ripple, particularly at high speed. The proposed pulsating flux injection scheme used in DB-DTFC excites the same magnitude of current harmonics and induces no additional torque ripple over a wide speed range. [ABSTRACT FROM PUBLISHER]

This paper proposes a computationally efficient technique for estimating the composite load model parameters based on analytical similarity of parameter sensitivity. When the model parameters are updated in the optimization procedure to best fit the actual load dynamics, i.e., measurements, parameters of similar sensitivity representation in the given mathematical model structure are updated in the same manner at every iterative step. This research allows for practically reducing the number of load model parameters to be identified in the estimation process and the overall computational cost while preserving the desired complexity and accuracy of the original model. This approach consequently facilitates the parameter estimation in the optimization process and helps manage increased number of parameters often criticized for adopting the dynamic composite load model via measurement-based approach. Case studies for the real power system demonstrate the computational efficiency and intact accuracy of the proposed method with reference to the existing methods of estimating all the parameters of the given composite load model independently. [ABSTRACT FROM AUTHOR]

State-space current control enables high dynamic performance of a three-phase grid-connected converter equipped with an LCL filter. In this paper, observer-based state-space control is designed using direct pole placement in the discrete-time domain and in grid-voltage coordinates. Analytical expressions for the controller and observer gains are derived as functions of the physical system parameters and design specifications. The connection between the physical parameters and the control algorithm enables automatic tuning. Parameter sensitivity of the control method is analyzed. The experimental results show that the resonance of the LCL filter is well damped, and the dynamic performance specified by direct pole placement is obtained for the reference tracking and grid-voltage disturbance rejection. [ABSTRACT FROM PUBLISHER]

There are many parameters that can affect the launching efficiency of the induction coil launcher (ICL), but which parameter is the most important factor to the launching efficiency still needs further study. Taking the 82-mm caliber ICL, for instance, eight parameters of the ICL were chosen to analyze based on orthogonal experimental method, and then the tables of the parameter level and orthogonal experiment were built, respectively. After that a simulation model of the ICL was built and each experiment scheme in the orthogonal table was analyzed by simulation, and then the launching efficiency of each experiment scheme was obtained. Furthermore, the range analysis method was used to analyze the parameter sensitivity of the ICL. The research results show that the parameter sensitivity of the ICL from high to low for the analysis instance above is as follows: external radius of driving coil, trigger position, capacitance, driving coil turns, armature length, charge voltage of capacitor, driving coil length, and armature inner radius, which is useful to the parameter optimization and the design of the ICL. After that, four ICLs with different parameters were designed, with which the experiments were taken and the research results obtained from the orthogonal experimental method were verified. [ABSTRACT FROM PUBLISHER]

The goal of the North American Land Change Monitoring System (NALCMS) is to provide annually updated land cover maps for the North American continent using satellite information and automated data processing. Current activities of the project aim at the development of an automated algorithm to detect areas of change using 250 m MODIS data. This paper shows the methodology developed for Mexico and demonstrates the resulting change map between the years 2005 and 2010. A data-driven algorithm that builds upon the spectral differences of monthly image composites was developed and critical parameters were defined. Results show that only extreme values of difference images indicate change and that change has to be mapped in at least 25% of all features. The total area of change detected between 2005 and 2010 was 702,331 ha (0.36% of the country) which is in line with other change detection studies in Mexico. Accuracy assessment using higher spatial resolution images accounts for the change fraction in the reference data. The overall accuracy of the change/no change mask is approximately 80%. This is similar to decision tree-based change classification that was developed in other studies and applied to Mexico and significantly better than post-classification change detection. The main limitation is the coarse spatial resolution considering the small-patch landscape structure for large portions of the country, which results in a high omission error (50%) but only 20% commission error for change. [ABSTRACT FROM PUBLISHER]

This paper presents a state-space current control method for active damping of the resonance frequency of the LCL filter and setting the dominant dynamics of the converter current through direct pole placement. A state observer is used, whereupon additional sensors are not needed in comparison with the conventional L filter design. The relationship between the system delay and instability caused by the resonance phenomenon is considered. Nyquist diagrams are used to examine the parameter sensitivity of the proposed method. The method is validated with simulations and experiments. [ABSTRACT FROM AUTHOR]

A real-time soil parameter estimation method for wheel motion control of a planetary rover is proposed. In this method, dominant soil parameters are updated in real time to compensate the error of the other parameters that are fixed by empirical typical values. Sinkage exponent and internal friction angle are the dominant characteristic parameters of wheel-soil interaction, because they dominate the normal stress and sheer stress that constitute the interaction forces on the contact surface. To estimate these two parameters in real time, a robust extended Kalman filter with error-tolerant switch (ETS-REKF) is proposed in this paper. The developed ETS switches filtering mode between robust and optimal, which is triggered when the magnitude of the sum of system errors reaches a certain threshold that is controlled by an error-tolerant factor (ETF). The proposed filtering algorithm can follow soil-type change quickly and in the meantime provide smooth parameter estimation without being sensitive to the inherent error of the empirical wheel-soil interaction model. From a sufficient condition of the filter stability, the range of the ETF is derived. In addition, a trigonometric approximation method is provided to simplify the original wheel-soil model for convenient utilization of the filtering algorithm. Simulation and experiment results have demonstrated that the proposed ETS-REKF has the advantages of both optimality of the EKF and robustness of the usual robust EKF, working efficiently in the presence of soil-type change and inaccuracy of the empirical wheel-soil model. [ABSTRACT FROM AUTHOR]

Heating, ventilation and air conditioning (HVAC) units are one of the major resources providing demand response (DR) in residential buildings. A DR program requires a large population of units to make a significant impact on power grid services like peak shaving and balancing. This paper investigates the importance of various HVAC physical parameters and their distributions that affect the aggregate response of a population of units to DR signals. This is a key step to the construction of HVAC models with DR functionality, given insufficient data, to predict the DR capacity available for dispatch. The HVAC model parameters include the size of floors, insulation efficiency, the amount of solid mass in the house, and efficiency. These parameters are usually assumed to follow Gaussian or Uniform distributions over the population. The impact of uncertainty in parameter distributions are quantified through the following steps: 1) Simulate the response of an HVAC population during the transient phase and during steady state for a given DR signal; 2) Use a quasi-Monte Carlo sampling method with linear regression and Prony analysis to evaluate the sensitivity of the DR output to the uncertainty in the parameter distributions; and 3) Identify important parameters based on their impact to the aggregate HVAC response. Utilities or DR providers can use this analysis as guidance in the collection of data to derive an effective DR model. [ABSTRACT FROM PUBLISHER]

In this paper, L-band microwave observations were assimilated using the ensemble Kalman filter to improve root-zone soil moisture (RZSM) estimates from a coupled soil vegetation atmosphere transfer (SVAT)-vegetation model linked to a forward microwave model. Simultaneous state-parameter updates were performed by assimilating both synthetic and field observations during a growing season of sweet corn every three days, matching the temporal coverage of observations from the Soil Moisture and Ocean Salinity and Soil Moisture Active Passive missions. The sensitivities of parameters to the states were investigated using the information-theoretic measure of conditional entropy. Among the soil parameters, the pore-size index (λ) was the most sensitive to brightness temperatures (TB) during the early and midgrowth stages, while porosity (φ) was the most sensitive to TB during the reproductive stage. In the microwave model, the soil roughness parameters, root mean square (RMS) height (r), and correlation length (l) were the most sensitive during the early and mid stages, while the vegetation regression parameter (b) was the most sensitive during the reproductive stage. In the synthetic experiment, assimilation of TB provided RMS error reductions in RZSM estimates of 70% compared to open loop estimates. Minimal variations in performance were observed across different stages of the season during the synthetic experiment. However, when field observations of TB were assimilated, significant differences in RZSM estimates were observed during different growth stages. Maximum RMS difference (RMSD) reductions in RZSM estimates of 33.3% were observed compared to open loop estimates during the early stages, while improvements of 4.8% and 16.7% were observed in the mid- and reproductive stages, respectively. Further analyses of assimilation with field observations also suggest some improvements in the SVAT model are needed for moisture transport immediately following the precipitation/irrigation events. In the microwave model, the linear vegetation formulation for estimating canopy opacity, parameterized by b, was inadequate in capturing the complexities in TB during stages of high vegetative and reproductive growth rates. [ABSTRACT FROM AUTHOR]

This paper presents a new method to calculate stray capacitance of coil turns of magneto flux cumulative generator. The proposed method depends on the coil geometrical properties. The presented analysis in this paper is based on the calculation of capacitance between two adjacent turns and capacitance between the coil turns and the central cylindrical liner of the generator for a single-layer coil with N series turns having an integrated round cross section. Moreover, the effects of the insulating coating of winding, winding pitch, distance of coil turns to the central cylindrical liner on the stray capacitance, and the sensitivity analysis of effective parameters in the creation of stray capacitance between coil turns and also between coil turns and the central cylindrical liner are considered in this paper. Simulation results show that the proposed method is very useful for the designing geometrical structure of the magneto cumulative generator coil. [ABSTRACT FROM AUTHOR]

In this paper, a speed-adaptive reduced-order observer for sensorless vector control of doubly fed induction generators (DFIGs) is proposed. The observer is a simulation of the rotor current dynamic model with feedback of the estimation error and a speed-adaptation loop. Feedback and adaptation gains are designed based on the closed-loop observer model. A parameter sensitivity analysis reveals that this observer is robust against machine parameter variations in the normal operating regions. Simulation results demonstrate desired steady-state and dynamic performance of this sensorless control approach for DFIG-based variable-speed wind turbines. [ABSTRACT FROM AUTHOR]

Fiber tracking of Diffusion Tensor Imaging (DTI) data offers a unique insight into the three-dimensional organisation of white matter structures in the living brain. However, fiber tracking algorithms require a number of user-defined input parameters that strongly affect the output results. Usually the fiber tracking parameters are set once and are then re-used for several patient datasets. However, the stability of the chosen parameters is not evaluated and a small change in the parameter values can give very different results. The user remains completely unaware of such effects. Furthermore it is difficult to reproduce output results between different users. We propose a visualization tool that allows the user to visually explore how small variations in parameter values affect the output of fiber tracking. With this knowledge the user cannot only assess the stability of commonly used parameter values but also evaluate in a more reliable way the output results between different patients. Existing tools do not provide such information. A small user evaluation of our tool has been done to show the potential of the technique. [ABSTRACT FROM AUTHOR]

This paper studies measurement uncertainty propagation and parameter sensitivity based on a torque-estimation model for induction machines. The model is based on the equation that describes the interaction of rotor flux and rotor currents. Contrary to classical schemes for induction motor control, this is an open-loop scheme; however, the model still requires different machine parameters. Therefore, the parameter sensitivity of the model is performed. For validation, the model is implemented in the real-time environment dSPACE, and a test induction machine is subjected to different combinations of speed and torque profiles. The identified model can be used to replace mechanical torque-measurement devices or as a backup for a low-cost torque sensor. [ABSTRACT FROM AUTHOR]

In this paper, two relevant computational aspects related to the design of nonlinear oscillators are considered: sensitivity to electrical parameter variation and sensitivity to small-amplitude injected signals. First, the analysis of the perturbation induced by parameter fluctuation is theoretically investigated, and a set of formal equations is deduced that allows us to correctly decompose amplitude and period variations. Second, the analysis of the perturbation induced by a generic weak signal is considered. This analysis is based on a well-consolidated approach that employs the Floquet eigenvector v1 (t) to project perturbation into the phase domain. It is shown that the same system of equations that formalizes the parameter-sensitivity problem can be exploited to calculate the v1 (t) projection vector. An efficient and reliable numerical implementation of a formal perturbation analysis is then proposed that allows the oscillator designer to evaluate both parameter sensitivity and signal-injection sensitivity in a homogeneous frame. [ABSTRACT FROM AUTHOR]

In this paper, we present two methods, direct simulation (DS), and conditional expectation estimation (CEE), for estimating the unreliability, transient unavailability, steady unavailability, mean time to failure (MTTF), mean time between failure (MTBF), and their parameter sensitivities of consecutive-k-out-of-n: F repairable systems with (k - 1)-step Markov dependence. After an expression of the likelihood ratio estimator of parameter sensitivity is introduced, the direct estimators, and conditional expectation estimators are derived. The analytical results in a study by Lam & Ng were used to verify the algorithms presented in this paper. Numerical examples of highly reliable linear, and circular C (4, 50: F), and C (4,100: F) systems were illustrated to compare the algorithm efficiencies of DS, and CEE and CEE was found to be remarkably more efficient than DS. [ABSTRACT FROM AUTHOR]