• Journal of Power Electronics
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• v.10 no.5
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• pp.518-527
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• 2010

This paper presents a new technique for directly designing a linear digital controller for a single-phase pulse width modulation (PWM) converter systems, based on closed-loop identification. The design procedure consists of three steps. First, obtain a digital current controller for the inner loop system by using the error space approach, so that the power factor of the supply is close to one. The outer loop is composed of a voltage controller, a current control loop including a current controller, a PWM converter, and a capacitor. Then, all the components, except the voltage controller, are identified by a discrete-time equivalent linear model, using the closed-loop output error (CLOE) method. Based on this equivalent model, a proper digital voltage controller is then directly designed. It is shown through PSim simulations and experimental results that the proposed method is useful for the practical design of PWM converter controllers.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.335-339
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• 1998

This paper presents a closed loop identification algorithm in time domain. This algorithm can be used for identification of unstable system and for model validation of system which is difficult to derive analytical model. In time domain, projection filter, which projects a finite number of input output data of a system into its current space, is used to relate the state space model with a finite difference model. Then recursive relations between the Markov parameters and the ARX model coefficients are derived to identify the system, controller and Kalman filter Markov parameters recursively, which are finally used to identify the system, controller and Kalman filter gains. The NASA LAMSTF is used to validate the algorithms developed.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.493-498
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• 2000

The magnetic bearing systems are intrinsically unstable, and need the feedback control of electromagnetic forces with measured displacements. So the controller design plays an important role in constructing high performance magnetic bearing system. In case of magnetic bearing systems, the order of identified model is high because of unknown dynamics included in closed loop systems - such as sensor dynamics, actuator dynamics-and non-linearity of magnetic bearings itself. "Identification for control" - joint optimization of system identification and controller design- is proposed to get the limited-order model which is suited for the design of high-performance controller. We applied the joint identification/controller design scheme to MIMO rigid rotor system supported by magnetic bearings. Firs, we designed controller of a nonlinear simulation model of MIMO magnetic bearing system with this scheme and proved its feasibility. Then, we performed experiments on MIMO rigid rotor system supported by magnetic bearings, and the performance of closed-loop system is improved gradually during the iteration.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1166-1171
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• 2001

The method for output disturbance estimation is proposed. In this method, output disturbance is estimated from the closed loop system dynamics using the output and control input signals. In the closed-loop output-disturbance estimator, precise system identification is required to reduce estimation error. The realization of estimator was done by the DSP board (DSPl103), and disturbance estimation in various environments was performed： change of rotation speed, media feature and spindle motor with (or without) auto-ball balancing system (ABS). From these experiments, the disturbance characteristics of ODD under various conditions are analyzed, and the desirable servo loop configuration based these results is proposed.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.654-667
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• 2003

This paper presents a consequence of the systematic approach to identify the aerodynamic parameters of an unmanned aerial vehicle (UAV) equipped with the automatic flight control system. A 3-2-1-1 excitation is applied for the longitudinal mode while a multi-step input is applied for lateral/directional excitation. Optimal time step for excitation is sought to provide the broad input bandwidth. A fully automated programmed flight test method provides high-quality flight data for system identification using the flight control computer with longitudinal and lateral/directional autopilots, which enable the separation of each motion during the flight test. The accuracy of the longitudinal system identification is improved by an additional use of the closed-loop flight test data. A constrained optimization scheme is applied to estimate the aerodynamic coefficients that best describe the time response of the vehicle. An appropriate weighting function is introduced to balance the flight modes. As a result, concurrent system models are obtained for a wide envelope of both longitudinal and lateral/directional flight maneuvers while maintaining the physical meanings of each parameter.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.24-34
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• 2007

Closed-loop active twist control of integral helicopter rotor blades is investigated in this paper for reducing hub vibration induced in forward flight. A four-bladed fully articulated integral twist-actuated rotor system has been designed and tested successfully in wind tunnel in open-loop actuation. The integral twist deformation of the blades is generated using active fiber composite actuators embedded in the composite blade construction. An analytical framework is developed to examine integrally twisted helicopter blades and their aeroelastic behavior during different flight conditions. This aeroelastic model stems from a three-dimensional electroelastic beam formulation with geometrical-exactness, and is coupled with finite-state dynamic inflow aerodynamics. A system identification methodology that assumes a linear periodic system is adopted to estimate the harmonic transfer function of the rotor system. A vibration minimizing controller is designed based on this result, which implements a classical disturbance rejection algorithm with some modifications. Using the established analytical framework, the closed-loop controller is numerically simulated and the hub vibratory load reduction capability is demonstrated.

• Journal of Power Electronics
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• v.17 no.2
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• pp.442-452
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• 2017

This paper deals with the input-output modeling of a vector controlled PMSM drive system and design of a simple multiple model adaptive control (MMAC) scheme with desired transient responses. We present a discrete-time modeling technique using closed-loop identification that can experimentally identify the equivalent models in the d-q coordinates. A bank of linear models for the equivalent plant of the current loop is first obtained by identifying them at several operating points of the current to account for nonlinearity. Based on these models, we suggest a simple q-axis MMAC combined with a fixed d-axis controller. After the current controller is designed, another equivalent model including the current controller in the speed control loop shall be similarly obtained, and then a fixed speed controller is synthesized. The proposed approach is demonstrated by experiments. The experimental set up consists of a surface mounted PMSM (5 KW, 220V, 8 poles) equipped with a flywheel load of 220kg and a digital controller using DSP (TMS320F28335).

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2687-2689
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• 2000

In many cases the systems are so complex that it is not possible to obtain reasonable models using physical insight. Also a model based on physical insight contains a number of unknown parameters even if the structure is derived from physical laws. These problems can be solved by system identification. In this paper, Arago's disk system which has both stable and unstable regions is selected as an example for identification and a state-space model is identified using tailor-made model structure of this system. In stable region, a state-space model of Arago's disk system is identified through open loop experiment and a state-space model of unstable region is identified through closed loop experiment after using fuzzy controller to stabilize unstable system.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.2
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• pp.203-208
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• 1998

This paper presents an adaptive fuzzy controller using an neural network and adaptation algorithm. Reference-model following neuro-fuzzy controller(RMFNFC) is invesgated in order to overcome the difficulty of rule selecting and defects of the membership function in the general fuzzy logic controller(FLC). RMFNFC is developed to tune various parameter of the fuzzy controller which is used for the discrete nonlinear system control. RMFNFC is trained with the identification information and control closed loop error. A closed loop error is used for design criteria of a fuzzy controller which characterizes and quantize the control performance required in the overall control system. A control system is trained up the controller with the variation of the system obtained from the identifier and closed loop error. Numerical examples are presented to control of the discrete nonlinear system. Simulation results show the effectiveness of the proposed controller.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.1-4
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• 1995

We propose a new design method for a generalized predictive control (GPC) system based on the parametrization of two-degree-of freedom control systems. The objective is to design the GPC system which guarantees the stability of the control system for a perturbed plant. The design procedure of our proposed method consists of three steps. First, we design a basic controller for a nominal plant using the LQG method and parametrize a whole control system. Next, we identify the deviation between the perturbed plant and the nominal one using a closed-loop identification method and design a free parameter of parametrization to stabilize the closed-loop system. Finally, we design a feedforward controller so as to incorporate GPC technique into our controller structure. A numerical example is presented to show the effectiveness of our proposed method.