• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.665-673
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• 2017

This paper proposes a field weakening control method for operating an induction motor with a variable DC input voltage condition. In the variable DC voltage condition such as a battery, the field weakening method are required for the maximum output power. The conventional field weakening control methods can be used for operating the induction motor over the rated speed in a constant DC-link voltage condition. However, the conventional methods for operating the motor with the variable DC voltage is not suitable for the maximum output power. To overcome this problem, this paper proposes the optimized field weakening control method to extend the operating range of the induction motor with a rated power in a limited thermal and a wide DC input voltage conditions. The optimized d-axis and q-axis current equations are derived according to the field weakening region I and II to extend the operating region. The experimental results are presented to verify the effectiveness of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1909-1914
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• 2004

Passive velocity field control (PVFC) was previously developed for fully mechanical systems, in which the motion task was specified behaviorally in terms of a velocity field, and the closed-loop was passive with respect to a supply rate given by the environment input. However the PVFC was only applied to a single manipulator, the proposed control law was derived geometrically, and the geometric and robustness properties of the closed-loop system were also analyzed. In this paper, we propose a method to apply a decentralized control algorithm to cooperative 3-wheeled mobile robots whose subsystem is under nonholonomic constraints and which convey a common rigid object in a horizontal plain. Moreover it is shown that multiple robot systems ensure stability and the velocities of augmented systems convergence to a scaled multiple of each desired velocity field for cooperative mobile robot systems.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.881-882
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• 2008

For the interior permanent magnet synchronous motor(IPMSM) drive to operate above the base speed in the constant horsepower region, the field weakening control is applied. However, the field weakening control was not almost applied to sensorless control of the interior permanent magnet synchronous motor. In this paper, the field weakening control is applied to the sensorless control of IPMSM based on the fuzzy controller. The effectiveness of the proposed system is verified by the experimental results.

• Proceedings of the KIEE Conference
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• summer
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• pp.926-928
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• 2004

For the permanent magnet synchronous motor(PMSM) drive to operate above the base speed in the constant horsepower region, field weakening control is applied. But field weakening control was not almost applied to sensorless control of the permanent magnet synchronous motor. In this paper, field weakening control is applied to the sensorless control of PMSM based on an instantaneos reactive power. And the effectiveness of the proposed system is verified by the experimental results.

• Journal of Haehwa Medicine
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• v.8 no.1
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• pp.559-592
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• 1999

It has been known that Ki(氣) energy is very effective on many adult diseases. Oriental Medicine has acknowledged Ki as an existing reality and investigated its effects on the body. However, the existence of Ki has not been fully explained. In order to find a conclusive evidence on the existence of Ki, this experiment was done to study the mutual relationship of Ki with a magnetic field and BEP (biological energy projector). The BEP apparatus was irradiated under the magnetic field on rats in the hyperlipidemic induced state. Following criterias were measured in this experiment: weight change, weight of the visceral organs, serum, hepatic lipid peroxide, bleeding time, tissue factor, and etc. The following results were obtained in this study: 1. The weight of rat significantly decreased in the magnetic field treated group and radically reduced in the group treated with both magnetic field and BEP. 2. The weight of liver, heart, and kidney increased in both the magnetic field treated group and magnetic field+BEP group compared to the normal group, but decreased in comparison to the control group. No changes were witnessed in the weight of spleen. 3. Serum and hepatic total cholesterol, total lipid, and lipid peroxide level significantly decreased in both magnetic field treated group and magnetic field+BEP treated group, while lipase activity has increased noticeably. 4. Serum HDL showed a significant increase in both magnetic field treated group and magnetic field+BEP treated group compared to the control group, while LDL and VLDL level decreased significantly. 5. A bleeding time significantly increased in both magnetic field treated group and magnetic field+BEP treated group compared to the control group. A tissue factor value of the lung decreased in the magnetic field treated group and magnetic field+BEP treated groups while increased in the control group. 6. Serum and hepatic lipid peroxide and glutathione level were significantly decreased in the magnetic field treated group and magnetic field+BEP treated group, while hepatic glutathione level was significantly increased compared to the control group. 7. A significant increase was found in the serum hydroxyl radical and SOD activity in the dietary hyperlipidemic rats, and significant decrease was found in the serum lipid peroxide content and superoxidase activity. 8. Hepatic cytosolic enzyme xanthine oxidase and aldehyde oxidase showed a significant decrease in the magnetic field treated group and magnetic field+BEP treated group. Through the above experimental results, one can suggest that the magnetic field with BEP can suppress hyperlipidemia and boost lipid metabolism and restructuring a lipid in liver, which increases the function of liver. To conclude, BEP is considered to show more potent effects under the exposure of magnetic field because magnetic field seems to increase the flow of Ki in the body.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.3
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• pp.5-11
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• 1978

Since 1970, herbicides have been widely used in the crop production, especially in paddy field in Korea. In 1978, both preemergence and postemergence type herbicides are applied in the approximately 70% of total paddy field and 15% of upland to control weeds. Most herbicides control annual weeds effectively, but perennials have been problems in the paddy field. Under upland conditions, effectiveness of herbicides varies depending on many environmental conditions (soil moisture, soil physical properties, temperature, etc.) as well as uniform application of appropriate amounts of herbicides. In Korea, many research works have been concentrated on the screening of new herbicides in terms of herbicide effectiveness and yield or phytotoxicity of crops, and especially on the paddy field. However, physiological aspects of herbicidal action in plant and interaction of herbicides with the environments have not been studied approximately. Therefore, researches on the uptake of herbicides and the influence of herbicides on the physiological phenomena such as photosynthesis, respiration, nutrient uptake etc., to control troublesome perennial weeds in the paddy field are needed in future. Also some researches are needed to improve effectiveness of herbicirdes under upland conditions.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.30-32
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• 2005

In this paper, voltage control strategy for maximum torque operation of stator flux-oriented induction machine drive in the field-weakening region is proposed. In a conventional stator flux-oriented (SFO) induction machine drive system of the maximum torque capability cannot be obtained. The field-weakening method is used to vary the stator-flux reference in proportion to the inverse of the rotor speed. The proposed algorithm, based on the voltage control strategy, ensures the maximum torque operation over the field-weakening region. The proposed algorithm, voltage control strategy for maximum torque operation of capability, which is insensitive to the variation of machine parameters In the field-weakening region. The proposed algorithm is verified by simulation.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.3
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• pp.170-184
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• 2024

With the advancement of autonomous navigation technology in maritime domain, there is an active research on swarming Unmanned Surface Vehicles (USVs) that can fulfill missions with low cost and high efficiency. In this study, we propose a formation control algorithm that maintains a certain shape when multiple unmanned surface vehicles operate in a swarm. In the case of swarming, individual USVs need to be able to accurately follow the target state and avoid collisions with obstacles or other vessels in the swarm. In order to generate guidance commands for swarm formation control, the potential field method has been a major focus of swarm control research, but the method using the potential field only uses the position information of obstacles or other ships, so it cannot effectively respond to moving targets and obstacles. In situations such as the formation change of a swarm of ships, the formation control is performed in a dense environment, so the position and velocity information of the target and nearby obstacles must be considered to effectively change the formation. In order to overcome these limitations, this paper applies a method that considers relative velocity to the potential field-based guidance law to improve target following and collision avoidance performance. Considering the relative velocity of the moving target, the potential field for nearby obstacles is newly defined by utilizing the concept of Velocity Obstacle (VO), and the effectiveness and efficiency of the proposed method is verified through swarm control simulation, and swarm control experiments using a small scaled unmanned surface vehicle platform.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.227-230
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• 1993

Recently, the development of novel control methodology enables us to improve the performance of AC-machine drives by using pulse width modulation (PWM) technique. Usually, the dynamic characteristic of induction motor (IM) has been represented by the 5-th order nonlinear differential equation. This dynamics, however, can be reduced to 3-rd order dynamics by applying direct control of IM input current. This methodology concludes that it is much easier to control IM by means of the field-oriented methods employing the current controller. Therefore a precise current control is crucial to achieve a high control performance both in dynamic and steady state operations. This paper presents an adaptive fuzzy current controller with artificial neural network (ANN) for field-oriented controlled IM. This new control structure is able to adaptively minimize a current ripple while maintaining constant switching frequency. Especially the proposed controller employs neuro-computing philosophy as well as adaptive learning pattern recognizing principles with respect to variations of the system parameters. The proposed approach is applied to the IM drive system, and its performance is tested through various simulations. Simulation results show that the proposed system, compared among several known classical methods, has a superb performance.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.391-393
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• 2005

Automatic guided vehicle(AGV) in the factory has an important role to advance the flexible manufacturing system. In this paper, we propose a novel object-transportation control algorithm of cooperative AGV systems to apply decentralized control scheme based on virtual-passivity. It is shown that the cooperative AGV systems ensure stability and the convergence to scaled multiple of each desired velocity field for multiple AGV systems. Finally, the application of proposed virtual passivity-based decentralized control algorithm via system augmentation is applied to be the tracking a circle. Also. the simulation results for the object-transportation by two AGV systems illustrate the validity of the proposed control scheme.