• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.131-136
• /
• 1988

This study is a research on the dynamic characteristics of non-linear dynamic vibration absorber in which harmonic motion is applied to the foundation of the main system. The amplitude ratio of the system with non-linear dynamic vibration absorber was obtained by harmonic balance methods and the unstable region was determined by stability analysis. As a result of study, the amplitude ratio decreases as mass ratio increases.

• Proceedings of the KIEE Conference
• /
• 2002.06a
• /
• pp.79-82
• /
• 2002

Non-linear loads are the sources of power systems harmonics, and the power quality is influenced by harmonics, Recently, the requirements of power quality is important. For the power quality problems. it is very important that the development of power measurement circuit for non-linear load. In this paper, it is discoursed on that high speed sampling circuit and efficient power analysis algorithms. The sampling circuit is implemented using FPGA. Since the power measurement circuit system is composed by FPGA and efficient power algorithms. it is practicable application that accurate power measurement, stable protection relaying, and low cost system configuring.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.4
• /
• pp.567-575
• /
• 2016

This paper proposed the voltage control of stand-alone inverter for power quality improvement under unbalanced and non-linear load. The 3-phase DC-AC inverter controls CVCF(Constant Voltage Constant Frequency) and selective harmonic eliminate method in stand-alone mode by PR controller, and the stand-lone inverter supplies stable sinusoidal voltage to balanced, unbalanced and non-linear loads. The total harmonic distortion(THD) of line-to-line load voltage($V_{LL}$) is 1.2% in the balanced load. THD of $V_{LL}$ is reduced from 5.2% to 1.4% and 6.7% to 3.5%, respectively unbalanced and non-linear load. The stand-alone inverter can be supplies sinusoidal balanced voltage to unbalanced load because the voltage unbalanced factor(VUF) of $V_{LL}$ is reduced from 5.2% to 1.4% in the unbalanced load. Feasibility of control method for a stand-alone inverter will be verified through 30kW stand-alone inverter system.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.10
• /
• pp.181-186
• /
• 2012

In this paper, we describe the synthesis of robust and non-fragile Kalman filter design for a class of uncertain linear system with polytopic uncertainties and filter gain variations. The sufficient condition of filter existence, the design method of robust non-fragile filter, and the measure of non-fragility in filter are presented via LMIs(Linear Matrix Inequality) technique. And the obtained sufficient condition can be represented as PLMIs(parameterized linear matrix inequalities) that is, coefficients of LMIs are functions of a parameter confined to a compact set. Since PLMIs generate infinite LMIs, we use relaxation technique, find the finite solution for robust non-fragile filter, and show that the resulting filter guarantees the asymptotic stability with parameter uncertainties and filter fragility. Finally, a numerical example will be shown.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.15 no.5
• /
• pp.72-78
• /
• 2006

The paper proposes reference model error feedback control scheme for motion control system with hard non-linear components as like saturation and dead-zone in plant input part. Additionally, the plant has the system uncertainty effected by plant model parameter deviation and disturbance. The control algorithm uses the reference model to apply additional feedback loop with the error between reference model output and actual output effected by disturbance and non-linear components. And the stability evaluation based on Popov stability and controller design method are formulated to be performed. The effectiveness of the proposed scheme is examined by simulations. The results are proven by reasonable performances following reference model responses with good disturbance rejection performance without over-tuning of controller.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.9
• /
• pp.1612-1617
• /
• 2008

Since most disturbance observer (DOB) approaches have been limited to minimum-phase systems (or systems having no zero dynamics), we propose a new DOB structure that can be applied to non-minimum phase systems. The new structure features an additional system, which is called as V-filter, whose role is to yield a minimum phase system when connected with the plant in parallel. In order to design the V-filter systematically we first consider a class of linear systems that can be stabilized via PID controller. By inverting the controller's transfer function, we can simply construct the filter. A convenient way of designing V-filter is presented by using an iterative linear matrix inequality (LMI) algorithm. With an illustrative example the simulation result shows that substantial improvement in the performance has been achieved compared with the control system without the DOB.

• Proceedings of the KIEE Conference
• /
• 2004.05a
• /
• pp.13-15
• /
• 2004

In this paper, we propose a novel stability criterion and a guideline of controller design for switched linear systems. Unlike existing criterions such as Lie algebraic method and multiple Lyapunov functions method, the proposed criterion can be applied to each individual system without considering an overall system. By applying the proposed criterion to each individual system separately, a state feedback controller can be easily designed. Stability of the overall system is proved by developing a rule to determine non-increasing Lyapunov functions recursively at each switching instant. An illustrative example is given.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.1 s.139
• /
• pp.43-49
• /
• 2005

in this paper a dolphin-fender moored pontoon-type floating structure in shallow water depth is studied focusing on mooring force. The pontoon-type floating structure is 500m long, 300m wide. The structure has partially non-uniform drafts of 2.0m and 3.0m. The employed mooring system is a guyed frame type dolphin-fender system. The 1/125 scale model fender system is made of rubber tube to have hi-linear load deflection characteristics. A series of model tests has been conducted focusing on motion and fender force responses in regular and irregular waves at KRISO's ocean engineering basin Non-linear numerical simulation of fender reaction force has been carried out and the results are compared with those of model tests. The simulated rigid body motion and mooring forces also have been compared with the test results.

• International Journal of Control, Automation, and Systems
• /
• v.1 no.4
• /
• pp.503-510
• /
• 2003

This paper describes the synthesis of robust and non-fragile $H^{i~}$state feedback controllers for linear varying systems with time delay and affine parameter uncertainties, as well as static state feedback controller with structural uncertainty. The sufficient condition of controller existence, the design method of robust and non-fragile $H^{i~}$static state feedback controller, and the region of controllers satisfying non-fragility are presented. Also, using some change of variables and Schur complements, the obtained conditions can be rewritten as parameterized Linear Matrix Inequalities (PLMIs), that is, LMIs whose coefficients are functions of a parameter confined to a compact set. We show that the resulting controller guarantees the asymptotic stability and disturbance attenuation of the closed loop system in spite of time delay and controller gain variations within a resulted polytopic region.

• Journal of KSNVE
• /
• v.9 no.4
• /
• pp.849-855
• /
• 1999

Neural Networks have shown potential to become an attractive alternative to classic methods for identification and control of non-linear dynamic systems. The purpose of this paper is to present an application of neural networks, that is a neural reconstruction of the input signal of a non-linear unknown system. This basic methodology could be used for practical purpose in several engineering fields. Clearly applications of the proposed scheme can be of interest for physical systems where a complete network of sensors measuring system inputs is not available. It should also be emphasized that the application of the reconstruction scheme is of little or no interest when the analyzed system works and operates at nominal conditions. In fact, only when failures and/or system anomailes occur, leasing to performance degradation and/or shutdown, the application of this scheme is of interest. The paper presents the results of the methodology applied to unknown non-linear dynamic systems and the robustness of the scheme to white and colored system noise was evaluated.