• Journal of Power Electronics
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• v.16 no.1
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• pp.351-361
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• 2016

Power quality is a critical issue in distribution systems, where a dynamic voltage restorer (DVR) is commonly used to mitigate the voltage disturbances for loads. This paper deals with a nonlinear control for the three-phase four-wire (3P-4W) DVR under a grid voltage unbalance and nonlinear loads in the distribution system, where a novel control scheme based on the feedback linearization technique is proposed. Through feedback linearization, a nonlinear model of a DVR with a PWM voltage-source inverter (VSI) and LC filters is linearized. Then, the controller design of the linearized model is performed by applying the linear control theory, where the load voltages are kept constant by controlling the d-q-0 axis components of the DVR output voltages. To keep the load voltage unchanged, an in-phase compensation strategy is employed, where the load voltages are recovered to be the same as the previous voltage without a change in the magnitude. With this strategy, the performance of the DVR becomes faster and more stable even under unbalanced source voltages and nonlinear loads. The validity of the proposed control strategy has been verified by simulation and experimental results.

• The Journal of Korean Physical Therapy
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• v.31 no.5
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• pp.279-285
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• 2019

Purpose: This study examined the effects of spinal stabilization exercises using visual feedback on the gross motor function and balance of the sitting posture in children with cerebral palsy. Methods: The subjects were 18 children with cerebral palsy aged 8-15 years in the I-III stages of the Gross Motor Function Classification System. The subjects were divided into an experimental group (n=9) and control group (n=9). The experimental group was treated with 30 minutes of neurodevelopmental treatment and 20 minutes of spinal stabilization exercises using visual feedback. The control group was treated with 30 minutes of neurodevelopmental treatment and 20 minutes of spinal stabilization exercises without visual feedback. Both groups participated in the experiment twice a week for eight weeks. The Gross Motor Function Measurement was performed to evaluate the changes between pre- and the post-intervention in gross motor function. The Seated Limit of Stability Surface Area was measured to evaluate the changes in trunk balance. Results: Both experimental and control groups showed a significant increase in the gross motor function and trunk balance (p<0.05). The experimental group showed a significant increase in gross motor function compared to the control group (p<0.05). The experimental group showed a significant increase in the dynamic trunk balance in all directions when measuring the Seated Limit of Stability Surface Area (p<0.05). Conclusion: Spinal stabilization exercises using visual feedback for the neurodevelopmental treatment of children with cerebral palsy can improve their gross motor function and trunk balance when in a sitting posture more effectively.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.6
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• pp.524-529
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• 2005

In this paper, a novel neural network compensation technique for PD like fuzzy controlled robot manipulators is presented. A standard PD-like fuzzy controller is designed and used as a main controller for controlling robot manipulators. A neural network controller is added to the reference trajectories to modify input error space so that the system is robust to any change in system parameter variations. It forms a neural-fuzzy control structure and used to compensate for nonlinear effects. The ultimate goal is same as that of the neuro-fuzzy control structure, but this proposed technique modifies the input error not the fuzzy rules. The proposed scheme is tested to control the position of the 3 degrees-of-freedom rotary robot manipulator. Performances are compared with that of other neural network control structure known as the feedback error learning structure that compensates at the control input level.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.191-202
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• 2013

A control structure that makes possible the integration of a kinematic controller and a fuzzy logic (FL) deadzone compensator for mobile robots is presented. A tuning algorithm is given for the fuzzy logic parameters, so that the deadzone compensation scheme becomes adaptive, guaranteeing small tracking errors and bounded parameter estimates. Formal nonlinear stability proofs are given to show that the tracking error is small. The fuzzy logic deadzone compensator is implemented on a mobile robot to show its efficacy.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.5
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• pp.230-237
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• 2003

Current mode control has been used for DC to DC converters for over twenty years. There are many different control schemes which use the inductor current signal in one way or another to control the DC to DC converter. In this paper, the state space averaging technique is applied for the analysis of flyback type current mode control circuit. We made real converter for the guarantee of stable output characteristic and proper design of feedback circuit. The validity of proposed method is verified from test result. The improvement of stability is confirmed by sinusoidal signal injection method with isolated transformer. It is known that phase margin is sufficient and gain crossover frequency fc is early 1/5 of switching frequency, fs, from the experimental result with frequency response analyzer.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.404-409
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• 2003

This paper discusses how to generate the reference compensation voltages in Dynamic Voltage Restorers (DVR) by use of PQR power theory Sensed three-phase terminal voltages are transformed to PQR coordinates without time delay. Since the reference voltages in PQR coordinates are do values, the voltage controller for DVRs is simple and easy to design. Proposed control method can be implemented by feedforward controllers or by feedback controllers. This paper verified the theory in the feedforward controller of a DVR by experiments.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.8 no.1
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• pp.68-74
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• 2008

In this paper, a novel neural fuzzy control method is proposed to control nonlinear systems. A standard PD-like fuzzy controller is designed and used as a main controller for the system. Then a neural network controller is added to the reference trajectories to form a neural-fuzzy control structure and used to compensate for nonlinear effects. Two neural-fuzzy control schemes based on two well-known neural network control schemes, the feedback error learning scheme and the reference compensation technique scheme as well as the standard PD-like fuzzy control are studied. Those schemes are tested to control the angle and the position of the inverted pendulum and their performances are compared.

• Korean System Dynamics Review
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• v.8 no.1
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• pp.151-171
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• 2007

Without exception, diverse LULU(Locally Unwanted Land Use) facilities have been under the location conflict, especially between the public government units and local residents. In spite of repeated trials-and-errors, literally, the location conflict has shown no sign of improvement over time in Korea. As practical means to tackle these issues, this study focuses on divulging explicit and implicit relationships among key factors derived from the location conflict on the LULU facilities. Here, major research variables cover residents' agreement, residents' perception, compensation expectation, and public opinion. As the location conflict on the LULU facilities could be strengthened or resolved by the dynamic feedback system, it applies basic tools geared toward causal loop diagramming. After repeated experiments, the study highlights the fact that the residents' perception, compensation expectation, and public opinion, individually and collectively, exert significant impact on the residents' agreement ratio.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.488-493
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• 2005

In gun stabilization systems, the torque comes from the unbalance mass of gun and the base acceleration is an important source of disturbance which degrades stabilization performance. Fatigue of gear train is another important factor affecting structural safety problems. In this paper, a feedback control gain is designed by optimal control weighting to difference between motor and gun velocity, and a feedforward controller using FXLMS algorithm is adopted to investigate those problems. Experimental results show that the feedforward compensator based on FXLMS can reduce the disturbance effects. The directional convergence property according to initial conditions of the FXLMS is also shown through experiments.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.294-297
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• 1994

A robust position tracking controller of the BLDDM sensitive to the load torque disturbance and inertia variation is constructed It is consisted of the linear feedback controller and the nonlinear feedforward compensator using the neural network. With effietive feedforward compensation of neural network, the robust position control can be obtained, which is verified by computer simulations.