• Journal of Power Electronics
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• v.16 no.3
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• pp.1110-1121
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• 2016

The mathematical model of a three phase PWM converter under the stationary αβ reference frame is deduced and constructed based on a Proportional-Resonant (PR) regulator, which can replace trigonometric function calculation, Park transformation, real-time detection of a Phase Locked Loop and feed-forward decoupling with the proposed accurate calculation of the inductance voltage vector. To avoid the parallel resonance of the LCL topology, the active damping method of the proportional capacitor-current feedback is employed. As to current vector error elimination, an optimized PR controller of the inner current loop is proposed with the zero-pole matching (ZPM) and cancellation method to configure the regulator. The impacts on system's characteristics and stability margin caused by the PR controller and control parameter variations in the inner-current loop are analyzed, and the correlations among active damping feedback coefficient, sampling and transport delay, and system robustness have been established. An equivalent model of the inner current loop is studied via the pole-zero locus along with the pole placement method and frequency response characteristics. Then, the parameter values of the control system are chosen according to their decisive roles and performance indicators. Finally, simulation and experimental results obtained while adopting the proposed method illustrated its feasibility and effectiveness, and the inner current loop achieved zero static error tracking with a good dynamic response and steady-state performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11C
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• pp.957-964
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• 2010

In this paper, we propose an indoor positioning algorithm based on 3 points near field angle-of-arrival estimation without side information. The conventional angle-of-arrival based positioning scheme requires the distance between the listener and the center of two points which is obtained by a received signal strength based range estimation. However, a received signal strength is affected by structure of room, placement of furniture, and characteristic of signal, these effects cause a large error to estimation of angle. In this paper, the proposed positioning scheme based on near field angle-of-arrival estimation can be used to estimate the position of listener without a prior distance information, just using time-difference-of-arrival information given from 3 points microphones. The performance of the proposed scheme is shown by cumulative distribution function of root mean squared error.

• Smart Structures and Systems
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• v.30 no.4
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• pp.339-351
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• 2022

Evaluating the current condition of existing structures is of primary importance for economic and safety reasons. This can be addressed by Structural System Identification (SSI). A reliable static SSI depends on well-designed sensor configuration and loading cases, as well as efficient parameter estimation algorithms. Static SSI by the Measurement Error-Minimizing Observability Method (MEMOM) is a model-based deterministic static SSI method that could estimate structural parameters from static responses. In the current state of the art, this method is only applicable when structures are subjected to one loading case. This might lead to lack of information in some local regions of the structure (such as the null curvatures zones). To address this issue, the SSI by MEMOM using multiple loading cases is proposed in this work. Observability equations obtained from different loading cases are concatenated simultaneously and an optimization procedure is introduced to obtain the estimations by minimizing the discrepancy between the predicted response and the measured one. In addition, a Genetic-Algorithm (GA)-based Optimal Sensor Placement (OSP) method is proposed to tackle the OSP problem under multiple static loading cases for the very first time. In this approach, the Fisher Information Matrix (FIM)'s determinant is used as the metric of the goodness of sensor configurations. The numerical examples of a 3-span continuous bridge and a 13-story frame, are analyzed to validate the applicability of the extended SSI by MEMOM and the GA-based OSP method.

• Journal of Trauma and Injury
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• v.29 no.4
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• pp.129-138
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• 2016

Purpose: Due to recent advances in internal fixation techniques, instrumentation and orthopedic implants there is an increasing number of humeral shaft fracture treated operatively. As a consequence, an increased number nonunion after operative fixation are being referred to our center. The aim of this study is to report the common error during osteosynthesis that may have led to nonunion and present a systematic analytical approach for the management of aseptic humeral shaft nonunion. Methods: In between January 2007 to December 2013, 20 patients with humeral shaft nonunion after operative procedure were treated according to our treatment algorithm. We could analysis x-rays of 12 patients from initial treatment to nonunion. In a subgroup of 12 patients the initial operative procedure were analyzed to determine the error that may have caused nonunion. The following questions were used to examine the cases: 1) Was the fracture biology preserved during the procedure? 2) Does the implant construct have enough stability to allow fracture healing? Results: In 19 out of 20 patients have showed radiographic evidence of union on follow up. One patient has to undergo reoperation because of the technical error with bone graft placement but eventually healed. There were 2 cases wherein the treatment algorithm was not followed. All patients had problems with mechanical stability, and in 13 patients had biologic problems. In the analysis of the initial operative fixation, only one of 12 patients had biologic problems. Conclusion: In our analysis, the common preventable error made during operative fixation of humeral shaft fracture is failure to provide adequate stability for bony union to occur. And with these cases we have demonstrated a systematic analytic management approach that may be used to prevent surgeons from reproducing the same fault and reduce the need for bone grafting.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.324-327
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• 1996

This paper describes the robust controller design methods applied to the problem of an automatic system for tow-vehicle/trailer combinations. This study followed an inverse Linear Quadratic Regulator(LQR) approach which combines pole assignment methods with conventional LOR methods. It overcomes two concerns associated with these separate methods. It overcomes the robustness problems associated with pole placement methods and trial and error required in the application of the LQR problem. Moreover, a Kalman filter is used as the observer, but is modified by using the loop transfer recovery (LTR) technique with modified transmission zero assignment. The proposed inverse LQG,/LTR controllers enhances the forward motion stability and maneuverability of the combination vehicles. At high speeds, where the inherent yaw damping of the vehicle system decreases, the controller operates to maintain an adequate level of yaw damping. At backward moton, both 4WS (2WS tow-vehicle, 2WS trailer) and 6WS (4WS tow-vehicle, 2WS trailer) control laws are proposed by using inverse LQG/LTR method. To evaluate the stability and robustness of the proposed controllers, simulations for both forward and backward motion were conducted using a detailed nonlinear model. The proposed controllers are significantly more robust than the previous controllers and continues to operate effectively in spite of parameter perturbations that would cause previous controllers to enters limit cycles or to loose stability.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.236-248
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• 2017

A direct stator flux vector control scheme in discrete-time domain is proposed in this paper for the interior permanent magnet synchronous motor (IPMSM) drive to remove the proportional-integral (PI) controller from the direct torque control (DTC) scheme applied to IPMSM and to obtain faster dynamic response and lower torque ripple output. The output of speed outer loop is used as the desired torque angle instead of the desired torque in the proposed scheme. The desired stator flux vector in dq coordinate is calculated with a given amplitude. The state-space equations in discrete-time for IPMSM are established, the actual stator flux vector is estimated in deadbeat manner by a full-order state observer, and then the closed-loop control is achieved by the pole placement. The stator flux error vector is utilized to calculate the reference stator voltage vector. Extracting the angle position and amplitude from the estimated stator flux vector and estimating the output torque are eliminated for the direct feedback control of the stator flux vector. The proposed scheme is comparatively investigated with a PI-SVM DTC scheme by experiment results. Experimental results show the feasibility and advantages of the proposed control scheme.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1998.10a
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• pp.407-410
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• 1998

Configuration is a set of building block processes, a series of selection and combining parts or components which composes a whole thing. A whole thing could be such a configurable object as manufacturing product, network system, financial portfolio, system development plan, project team, etc. Configuration problem could happen during any phase of product life cycle: design, production, sales, installation, and maintenance. Configuration has long been one of cost and time consuming work, because only high salaried technical experts on product and components can do configuration. Rework for error adjustments of configurations at later process causes far much cost and time, so accurate configuration is required. Under the on-line electronic commerce environment, configuration problem solving becomes more important, because component-based sales should be done automatically on the merchant web site. Automated product search, order placement, order fulfillment and payment make that manual configuration is no longer feasible. Automated configuration means that all the constraints among components should be checked and confirmed by configuration engine automatically. In addition, technical constraints and customer preferences like price range and a specific function required should be considered. This paper gives an brief overview of configuration problems: characteristics, representation paradigms, and solving algorithms and introduce CRSP(Constraint and Rule Satisfaction Problem) method. CRSP method adopts both constraint and rule for configuration domain knowledge representation. A survey and analysis on web sites adopting configuration functions are provided. Future directions of configuration for EC is discussed in the three aspects: methodology itself, companies adopting configuration function, and electronic commerce industry.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.308-313
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• 2012

Robust tuning rules of the motion profile are proposed to minimize the residual vibration. For asymmetric S-curve profile, tuning rules are analytically formulated using Laplace-domain approach. When the system modeling is known exactly, by placing a single zero of the motion profile on the pole of the system, the residual vibration can be perfectly eliminated under undamped system. However, if there are some amounts of the modeling errors, the residual vibration significantly increases. To track this issue, the robust tuning rules against modeling error are discussed. One of the proposed robust tuning rules is placing the multiple zeros of the motion profile on the pole of the system, and the other is placing the zeros of the motion profile around the pole of the system. Thanks to the proposed robust tuning rules, motion profile becomes more robust to modeling errors while minimizing the residual vibration. By simulation, the effectiveness of the proposed robust tuning rules is verified.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.3
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• pp.124-130
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• 1990

This paper presents a new layout language, HAN-LALA (HANyang LAyout LAnguage), to automate the LSI/VLSI layout design. HAN-LALA is a C extension, which is easy to describe the layout. As HAN-LALA is directly compiled with no preprocessor, it renders easy debugging and short design time. For the technology independent layout design, the design rules and the process technologies are organized into seperate modules. The related objects are grouped and the placement is performed on the groups. Also the various routing modules including a river routing module and the one which can consider the forbidden regions make the layout design error-free without detailed descriptions of the layout.

• Advances in aircraft and spacecraft science
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• v.6 no.6
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• pp.497-513
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• 2019

A wind tunnel test was conducted that measured surface fluctuating pressures aft of a ramp at transonic speeds. Dynamic pressure test data was used to perform a study to determine best locations for streamwise sensor pairs for shocked and unshocked runs based on minimizing the error in root-mean-square acceleration response of the panel. For unshocked conditions, the upstream sensor is best placed at least 6.5 ramp heights downstream of the ramp, and the downstream sensor should be within 2 ramp heights from the upstream sensor. For shocked conditions, the upstream sensor should be between 1 and 7 ramp heights downstream of the shock, with the downstream sensor 2 to 3 ramp heights of the upstream sensor. The shock was found to prevent the passage coherent flow structures; therefore, it may be desired to use the shock to define the boundary of subzones for the purpose of loads definition. These recommendations should be generally applicable to a range of expansion corner geometries in transonic flow provided similar flow structures exist. The recommendations for shocked runs is more limited, relying on data from a single dataset with the shock located near the forward end of the region of interest.