• International Journal of Control, Automation, and Systems
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• v.6 no.5
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• pp.677-688
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• 2008

In this paper, the general problem of impedance control for a robotic manipulator with a moving flexible base is addressed. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base mobile manipulator is rather new and is being considered for first time using singular perturbation and new sliding mode control methods by authors. Initially slow and fast dynamics of robot are decoupled using singular perturbation method. Slow dynamics represents the dynamics of the manipulator with rigid base. Fast dynamics is the equivalent effect of the flexibility in the base. Then, using sliding mode control method, an impedance control law is derived for the slow dynamics. The asymptotic stability of the overall system is guaranteed using a combined control law comprising the impedance control law and a feedback control law for the fast dynamics. As first time, base flexibility was analyzed accurately in this paper for flexible base moving manipulator (FBMM). General dynamic decoupling, whole system stability guarantee and new composed robust control method were proposed. This proposed Sliding Mode Impedance Control Method (SMIC) was simulated for two FBMM models. First model is a simple FBMM composed of a 2 DOFs planar manipulator and a single DOF moving base with flexibility in between. Second FBMM model is a complete advanced 10 DOF FBMM composed of a 4 DOF manipulator and a 6 DOF moving base with flexibility. This controller provides desired position/force control accurately with satisfactory damped vibrations especially at the point of contact. This is the first time that SMIC was addressed for FBMM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.39-49
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• 2003

The delta operator approach and the singular perturbation technique are introduced. The former reduces the round-off error in the numerical computation. The latter reduces computing time by decoupling the original system into the fast and slow sub-systems. The aircraft dynamics consists of the Phugoid and short-period motions whether its model is longitudinal or lateral. In this paper, an approximated solutions of lateral dynamic model of Beaver obtained by using those two methods in compared with the exact solution. For open-loop system and closed-loop system, and approximated solution gets identical to the exact solution with only one iteration and without iteration, respectively. Therefore, it is shown that implementing those approaches is very effective in the flight dynamic and control.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.3
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• pp.247-255
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• 2013

The flight control of re-entry vehicles poses a challenge to conventional gain-scheduled flight controllers due to the widely spread aerodynamic coefficients. In addition, a wide range of uncertainties in disturbances must be accommodated by the control system. This paper presents the design of a roll channel controller for a non-axisymmetric reentry vehicle model using the trajectory linearization control (TLC) method. The dynamic equations of a moving mass system and roll control model are established using the Lagrange method. Nonlinear tracking and decoupling control by trajectory linearization can be viewed as the ideal gain-scheduling controller designed at every point along the flight trajectory. It provides robust stability and performance at all stages of the flight without adjusting controller gains. It is this "plug-and-play" feature that is highly preferred for developing, testing and routine operating of the re-entry vehicles. Although the controller is designed only for nominal aerodynamic coefficients, excellent performance is verified by simulation for wind disturbances and variations from -30% to +30% of the aerodynamic coefficients.

• Journal of Digital Convergence
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• v.14 no.11
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• pp.201-224
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• 2016

The main objective of this study is to identify and analyze the factors affecting technology innovation of the innovative IT SMEs. A research model is established based on the previous studies on the technology innovation of SMEs. The model consists of independent variables (Adhocracy culture, R&D capability, IT capability, Leadership, and Appraisal & Reward), an intermediate variable (Knowledge management), and dependent variables (product/service innovation and process innovation). Major research results can be summarized as follows: IT SMEs pursuing technology innovation should: (1) pay attention to innovation oriented culture, IT capability, and evaluation & compensation systems of the company; (2) recognize that knowledge management is an essential activity performed by the company; (3) strengthen the R&D capabilities of the company by not only exerting internal efforts but establishing cooperative network with various parties; and (4) resolve the decoupling problem of the evaluation & compensation system.

• 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.

• Journal of Korea Water Resources Association
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• v.44 no.6
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• pp.429-438
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• 2011

In order to simulate a free surface flow in a trench channel, a three-dimensional incompressible unsteady Reynolds-averaged Navier-Stokes (RANS) equations are closed with the ${\kappa}-{\epsilon}$ model. The artificial compressibility (AC) method is used. Because the pressure fields can be coupled directly with the velocity fields, the incompressible Navier-Stokes (INS) equations can be solved for the unknown variables such as velocity components and pressure. The governing equations are discretized in a conservation form using a second order accurate finite volume method on non-staggered grids. In order to prevent the oscillatory behavior of computed solutions known as odd-even decoupling, an artificial dissipation using the flux-difference splitting upwind scheme is applied. To enhance the efficiency and robustness of the numerical algorithm, the implicit method of the Beam and Warming method is employed. The treatment of the free surface, so-called interface-tracking method, is proposed using the free surface evolution equation and the kinematic free surface boundary conditions at the free surface instead of the dynamic free surface boundary condition. AC method in this paper can be applied only to the hydrodynamic pressure using the decomposition into hydrostatic pressure and hydrodynamic pressure components. In this study, the boundary-fitted grids are used and advanced each time the free surface moved. The accuracy of our RANS solver is compared with the laboratory experimental and numerical data for a fully turbulent shallow-water trench flow. The algorithm yields practically identical velocity profiles that are in good overall agreement with the laboratory experimental measurement for the turbulent flow.

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.819-825
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• 2006

The objective of the present study is to verify the validity of a new truss model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. The new truss model is based on the relationship between shear and bending moment in a beam subjected to combined shear and bending. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. On the basis of the analytical results, the contribution by the web to shear resistance can be constant and have an excellent linear correlation with the web reinforcement ratio. The present decoupling approach may provide a simple way for the assessment of the role of each parameter or mechanism that affects the ultimate shear behavior of reinforced concrete beams.

• Progress in Superconductivity and Cryogenics
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• v.26 no.2
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• pp.9-18
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• 2024

The current study deals with the possible interplay between superconductivity and spin density wave in two band model high temperature iron based superconductor (FeBSC) Ba_1-xNa_xFe₂As₂. The electron and hole bands in the presence of the inter-band interaction between the two bands is becoming a vital issue to deal with the high temperature physics of the iron-based superconductors. In this research work, a model Hamiltonian appropriate for the system under consideration has been developed and the temperature dependent Green's function technique has been employed to get the solution for the equations of motion constructed for the two band model high temperature FeBSC Ba_1-xNa_xFe₂As₂. By making use of the decoupling procedure, the equations of motion for the dependence of superconducting transition temperature (T_C) on spin density wave(SDW) order parameter (Δ_SDW) in the electron intra-band (Δ_sc(e)) , hole intra-band (Δ_sc(h)) and inter-band (Δ_sc(eh)) for Ba_1-xNa_xFe₂As₂ have been obtained. We have also obtained the expression for the dependence of spin density wave transition temperature(T_SDW) on Δ_SDW for Ba_1-xNa_xFe₂As₂. Using some plausible approximations and appropriate experimental values for the parameters in the obtained equations of motion, phase diagrams of T_C versus Δ_sc(e), Δ_sc(h) and Δ_sc(eh) are plotted. Furthermore, a phase diagram of T_SDW versus Δ_SDW is plotted for the material under consideration. Finally, using the above mentioned phase diagrams, the interplay between superconductivity and spin density wave in the two band model high temperature FeBSC Ba_1-xNa_xFe₂As₂ has been demonstrated to be a very distinct possibility. The agreement of the current finding with the experimental observations is quite commendable.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.495-507
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• 2005

Measuring the end-to-end available bandwidth in the Internet is a useful tool for distributedapplication services or QoS (Quality-of-Service) guarantee. To measure the end-to-end available bandwidth, Single-hop Gap model-based packet train measurement techniques are well-known. However, the error of packet train output gap can happen by network topologies. This error of the output gap causes the inaccuracy of the available bandwidth measurement. In this paper, we propose a new end-to-end available bandwidth measurement technique with accurate capacity measurement and fast convergence methods. To solve the erroneous capacity measurement problem of the back-to-back packet train transmission, we propose a new available bandwidth measurement method by decoupling the capacity measurement with the initial gap of the packet train. Also, we propose a new technique to predict the proper initial gap of the packet train for faster convergence. We evaluate our proposed method by the simulation in various topologies comparing with previous methods.

• Korean Journal of Social Welfare
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• v.65 no.3
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• pp.265-289
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• 2013

The purpose of this study is to analyse the reality and dynamics of transition of work-family reconciliation policy and gender regime in Germany to focus on recent introduction of parents benefit by applying meta path analysis. There is made of 'layering' in work-family reconciliation policy area. Because political barrier has alleviated they can introduce parents benefit, but cannot help stick to child care benefit because of internal barrier. But because parents benefit has activated by 'differential growth', German gender regime has suffered core transition of complementation that dominant structure has changed from 'sequential reconciliation' to 'concomitant reconciliation'. On the other hand, by 'purposeful decoupling' of gender area, core activists have attempted to cut the possibility of weakening of coordination relationship on main institutional areas of German model.