• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1612-1618
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• 2021

The telegraph controller is a device used to control the speed of a ship, and it is a device that has a very direct effect on the safety of the crew. Accordingly, ship owners demand very high reliability of the telegraph controller, and the classification trend is to introduce HILS (hardware in loop system) test as a method to verify reliability. Therefore, in this paper, an electric propulsion ship was modeled to perform the HILS test of the Telegraph controller. For modeling, the specifications of the electric propulsion tug boat were defined, and the battery parts, propulsion motor parts, and ship model parts were modeled. In addition, various operation scenarios were defined and the Telegraph controller was modeled accordingly. Finally, the results of the integrated model were confirmed through simulation.

• The Journal of Korean Physical Therapy
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• v.33 no.2
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• pp.91-96
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• 2021

Purpose: This study investigated the effects of cryotherapy on the ankle joint muscle strength and balance ability in stroke patients with ankle joint muscles. Methods: In this study, 20 patients with chronic stroke were recruited from a rehabilitation hospital. The patients were divided into two groups: a cryotherapy group (10 patients) and a control group (10 patients). The cryotherapy group performed sit-to-stand training for 15 minutes and then cryotherapy for the minutes. In the control group, after sit-to-stand training for 15 minutes, blocked cryotherapy was provided for three minutes. In both groups, the interventions were provided five times a week for three weeks. The strength of the ankle joint muscles was measured before and after the training using the Biodex systems 3. The static balance ability was measured using balancia software, and the dynamic balance ability was measured by performing the sit-to-stand test (FTSST) five times. Results: After the training periods, the cryotherapy group showed significant improvement in the ankle dorsiflexor strength, ankle plantarflexor strength, weight distribution of the affected side, and FTSST compared to the control group (p<0.05). Conclusion: Based on these results, cryotherapy could be considered an effective method to improve the strength of ankle joint muscles. Cryotherapy improves muscle strength as it increases the motor neuron excitability. Therefore, cryotherapy may be considered to improve the strength of the ankle joint muscles of stroke patients.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.109-117
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• 2009

This paper presents a linear air bearing stage with compensated motion errors by active control of preloads generated by magnetic actuators with combination of permanent and electromagnets. A 1-axis linear stage motorized with a linear motor with 240mm of travel range is built for verifying this design concept and tested its performances. The three motions of the table are controlled with four magnetic actuators driven by current amplifiers and a DSP based digital controller. Three motion errors were measured combined method with laser interferometer and two-probe method with $0.085{\mu}m$ of repeatability for straightness error. The measured motion errors were modeled as functions of the stage position, and compensation were carried out with feedforward control because the characteristics of the motion control with magnetic actuators are linear and independent for each degree-of-freedoms. As the results, the errors were reduced from $1.09{\mu}m$ to $0.11{\mu}m$ for the vertical motion, from 9.42 sec to 0.18 sec for the pitch motion and from 2.42 sec to 0.18 sec for roll motion.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.93-98
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• 2022

The purpose of this paper was to propose a method for improving the performance of the open-loop control of single-phase permanent magnet synchronous motor (SP-PMSM), based on a square wave voltage injection. Generally, the SP-PMSM driving systems cmprise a full-bridge inverter and asymmetric air-gap structure of magnetic circuit, because a zero torque occurs on the symmetrical air-gap. As a result, it cannot be started at a specific rotor position. Thus, it is possible to cause the start-up failure at an open-loop control for sensorless operation of SP-PMSM. In this paper, the method with square wave voltage injection considering the nonlinearity of the inverter is presented to resolve the problem. The effectiveness of the proposed algorithm is verified through several experiments.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.17-25
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• 2011

This paper aims to find the optimal control gain for enhancing the convenience of electric walking frames and design a control algorithm. With the recent advances in medical technology, there has been a rapid increase in the aging population and a variety of mobile walking frames have been developed for improvement of the quality of life. However, the manual walking frames of such mobile aids don't have any electric motor which helps facilitate elderly users' walking and thus are not efficient enough for the old people of weak strength to use especially when moving on uneven surfaces such as slopes or thresholds. The types of electric walking frames have been developed to overcome such inefficiency. Electric walking frames require users' control operations for motor driving unlike manual frames. Therefore, when they are not properly handled, it causes considerable inconvenience to their users. The present study compared the electric walking frames with manual ones in terms of operational convenience and attempted to improve the user convenience of walking frames varying the control value for user convenience based on certain standards. This paper presented a haptic sensor designed to recognize the will to walk and measure the degree of convenience and proposed a control algorithm for improvement of convenience. For user convenience, this paper evaluated the relative convenience of walking frames in view of changing differences between the center of vehicle (COV) and the center of position (COP). With the employment of an electric walking frame and a new measuring method, all the processes were experimentally tested and validated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.1
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• pp.74-81
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• 1998

It is not good joint that today's traffic control system that the course of traffic volume increase tendency is followed, in the traffic volume is approched into the time of my car. Accordingly when we analyzed the existing traffic signal control system, the traffic signal system is developed from the machine type that the motor was centered, to get up to date, to the intelligence electron signal control system. But yet, when we have a test and a A/S on the control circuit, the circuit that is designed to the center IC and ROM are complicated. Also, the time of pass lamp that the car line stream is going, can not extended automatically a time till the traffic volume is decreased to the same direction. This theme must be a real time intelligence control system that the time of pass lamp can extend aumatically. The circuit of sequence ladder diagram on the traffic signal control of a crossroads that is desinged, can be satisfied the complicated vehicle order. Therefore when the circuit is changed, the new developed system is economical with that dosen't needs any of components to require the circuit equipment, and the time is saved with needlessness of the circuit wiring again, and have a much trustworthy. The control method of pass signal lamp in the car line stream connecting among PLC and Relay and Temp Sensor, can be changed to hand operation and to semi-automation and to all-automation. New intelligence traffic signal system is composed with all-together system of T Sensor + Video Camera + IBM PC that is able to guiding the establishment of traffic order.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.475-478
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• 2001

In performing the three-level SVPWM, it is nearly impossible to control the neutral-point potential exactly to the half of the dc-link voltage at all times. Therefore the inverter would produce an erroneous output voltage by this voltage unbalance. So the voltage unbalance has to be compensated in doing PWM, when the voltage unbalance occurs whether it is small or large, to make the inverter output voltage follow the reference voltage exactly the same. In this paper, a new compensating method for the neutral-point potential variation in a three-level inverter space vector PWM (SVPWM) is presented. By using the proposed method, the output voltage of the inverter can be made same as the reference voltage and thus the current and torque ripple of the inverter driven motor can be greatly improved even if the voltage unbalance is quite large. The proposed method is verified experimentally with a 3-level IGBT inverter.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.71-77
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• 2019

This study proposes a circulating current reduction method that uses high-frequency voltage compensation when carrier phase difference occurs between two inverters in MSIS. In MSIS, inverters are configured in parallel to increase power capacity and to increase efficiency by using inverters only as needed. However, in the parallel inverter structure, circulating current is inevitably generated. Circulating current increases the stress on the switch, adversely affects the current control performance, and renders load sharing difficult. The proposed method compensates for the output voltage reference of the slave module by using the high-frequency voltage so that the switching pattern of each module is matched even in asynchronous carriers. The validity of the proposed method is verified by simulations and experiments with 600 W IPMSM.

• Journal of Power Electronics
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• v.19 no.3
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• pp.727-743
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• 2019

This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.364-371
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• 2021

A magnetic flux saturation model of Synchronous Reluctance Motors (SynRMs) and a parameter estimation method are proposed at standstill. The proposed magnetic flux model includes the nonlinear relationship between the current and the magnetic flux for self-saturation and cross-saturation. Voltage is injected at standstill to estimate the magnetic flux saturation model. Voltages are injected into the d-axis and q-axis to obtain data on self-saturation. Subsequently, voltages are simultaneously injected into the d-q axis to obtain data on cross-saturation. On the basis of the measured current and the calculated magnetic flux, the parameters of the proposed model are estimated using the least square method (LSM). Simulation and experiment were performed on a 1.5-kW SynRM to verify the proposed method. The proposed model can be used to create a high-efficiency operation table, a sensorless algorithm, and a current controller to improve the control performance of a motor.