• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.171-178
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• 1998

This paper proposes a new overmodulation strategy to give a better voltage utilization by tracking voltage vector along hexagon sides. This strategy enables the inverter to control both magnitude and angle of current. Therefore, the vector control using this strategy can lead to better output torque dynamics compared to the conventional slip frequency control with six-step voltage, which is widely used in the traction drive. In this strategy, the d-axis output voltage of a current controller to control the flux is conserved and the q-axis output voltage to control the torque is controlled to place the voltage vector on the hexagon boundary In case of overmodulation. The limited q-axis voltage is used for anti-windup of q-axis current controller. This paper also presents a new field weakening scheme which incorporate the proposed overmodulation strategy. In this scheme, the flux level is selected by both required current limit and the available maximum voltage along hexagon sides. The validity of the proposed overall scheme is confirmed by the computer simulations for a typical traction drive with a 210[㎾] induction motor.

• 드라이브 ㆍ 컨트롤
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• 제17권2호
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• pp.28-37
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• 2020

It is difficult to analytically derive the relationship among volumetric displacement, flowrate, torque, and rotation speed regarding an instantaneous position of gerotor hydraulic pumps/motors. This can be explained by the geometric shape of the rotors, which is highly complicated. Herein, an analytical method for the instantaneous torque, rotation speed, flowrate, and volumetric displacement of a pump/motor is proposed. The method is based on two physical concepts: energy conservation and torque equilibrium. The instantaneous torque of a pump/motor shaft is determined for the posture of rotors from the torque equilibrium. If the torque equilibrium is combined with the energy conservation between the hydraulic energy of the pump/motor and the mechanical input/output energy, the formula for determining the instantaneous volumetric displacement and flowrate is derived. The numerical values of the instantaneous volumetric displacement, torque, rotation speed, and flowrate are calculated via the MATLAB software programs, and they are illustrated for the case in which inner and outer rotors rotate with respect to fixed axes. The degrees of torque fluctuation, speed fluctuation, and flowrate fluctuation can be observed from their instantaneous values. The proposed formula may provide a better understanding of the design or analysis process of gerotor pumps/motors.

• 한국정밀공학회지
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• 제33권4호
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• pp.309-316
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• 2016

In this study, we described the design of a three-axis force/torque sensor for measuring the force and torque in a lower-limb rehabilitation robot. The three-axis force/torque sensor is composed of Fx force sensor, Fz force sensor and Tz torque sensor. The sensing element for Fx force sensor and Tz torque sensor is used in a two-step parallel plate beam, and that of Fz force sensor is used in a parallel plate beam. The rated loads of Fx force sensor, Tz torque sensor and Fz force sensor are 300 N, 15 N m and 100 N, respectively. The three-axis force/torque sensor was designed using the finite element method, and manufactured using strain-gauges. The three-axis force sensor was further characterized. As a result, the interference error of the three-axis force/torque sensor was < 1.24%, the repeatability error of each sensor was < 0.03%, and the non-linearity was < 0.02%.

• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.453-462
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• 2016

This paper proposes a torque control method for surface mounted permanent magnetic synchronous motor (PMSM) driven by a 2-level voltage source driven inverter, which has fast torque response and small torque ripple. The proposed torque control method follows the finite control set model predictive control (FCS-MPC) strategy. A reference state is derived at each time step for the given time varying torque reference and the cost index is defined so that the tracking error for this reference state should be penalized. The choice of an optimal output voltage vector is made first from the 6 possible active voltage vectors of the 2-level voltage source inverter. Then a modulation factor for the chosen optimal voltage vector is obtained so that the torque ripple can be reduced further. It is shown that the proposed FCS-MPC control method yields fast torque tracking response and small torque ripple through simulation and experiments.

• 한국생산제조학회지
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• 제24권3호
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• pp.320-326
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• 2015

Despite the wide industrial applications of planetary gear trains, the relationship between the design parameters (tooth profile, carrier mass, etc.) and performance (strength, vibration, noise, etc.) remains poorly understood. A significant amount of research has focused on transmission errors, which are measurable performance indicators directly related to the design parameters. Herein, an experimental test rig for a single-stage planetary gear set built using digital angular encoders and gap sensors is described. To study the static and dynamic characteristics of this planetary gear train, the transmission errors and sun gear orbit are analyzed from the data measured under various levels of torque and speed. The transmission errors of the gear train decrease 40% when the speed increases from 30 to 600 rpm with an output torque of 39.2 Nm, and increase 22% when the output torque increases from 19.6 to 39.2 Nm with an input speed of 30 rpm.

• Journal of Magnetics
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• 제22권2호
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• pp.257-265
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• 2017

This paper presents a 2-D analytical method to calculate the back EMF of the axial flux permanent magnet synchronous generator (AFPMSG) with coreless stator and dual rotor having magnets mounted on both sides of rotor yoke. Furthermore, in order to reduce the no load voltage total harmonics distortion (VTHD), the initial model of the coreless AFPMSG is optimized by using a developed analytical method. Optimization using the 2-D analytical method reduces the optimization time to less than a minute. The back EMF obtained by using the 2-D analytical method is verified by a time stepped 3-D finite element analysis (FEA) for both the initial and optimized model. Finally, the VTHD, output torque and torque ripples of both the initial and optimized models are compared with 3D-FEA. The result shows that the optimized model reduces the VTHD and torque ripples as compared to the initial model. Furthermore, the result also shows that output torque increases as the result of the optimization.

• The Journal of Korean Physical Therapy
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• 제10권1호
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• pp.45-52
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• 1998

Since isokinetic concise can give an evaluation of muscle strength with great accuracy and objectively, it is widely used as the one of the important methods for evaluation of muscle performance. The purpose of this investigation was to compare values uncorrected for gravity with values corrected for gravity and to determine the effect of making this correction on knee flexors and extensors at three speeds. This investigation measured values isokinetically at $60^{\circ}/sec,\;120^{\circ}/sec,\;and\;180^{\circ}/sec$ in 14 male and 17 fermale university students. The gravity effect torque(GET) is the torque resulting from the effect of gravity on the combined weight of the leg and dynamometer arm. The GET was added to the measured extensors peak torque and subtraced from the flexors peak torque to yield gravity corrected values. Failure to consider GET greatly underetimated extensors torque and overtestimated flexors torque. Physical therapists must remember the importance of making the gravity correction in patients with reduced torque output where the gravitational torque is a greater percentage of the measured torque to ascertain correctly the relative strength of antagonists inversely affected by gravity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.243-247
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• 2004

The dynamometers which had made in a long time ago could not control the input/output quantity of water minutely and was sensitive to a noise since it was controlled by an analog control method. Therefore, a fully digital controlled system was urgently required to be robust against various noises. In this paper, the new system which can control the amount of circulated water in dynamometer was developed. This system is consisted of an industrial digital type controller and a servo motor. The industrial PLC was used as a main controller for the developed system, and the actuator and servo motor were used to control the inlet and outlet valve independently. The torque signal of load cell was fed back to the main controller to regulate the diesel engines load. Generally, an input/output valve position of the old dynamometer was fixed with a proper situation for an engine output test and the torque was changed according to the time interval. However, the torque value for the dynamometer could not be constantly kept because of the variation of the input water flow and fluid characteristic. Therefore, the automatic control of an inlet and outlet valve should be performed to keep the constant torque. So, the PID control method was applied to solve this problem. Also, the development of a web-based remote control system was described in this paper. This software will give us the convenience of operation, the more efficient operations, and the reduced operator workload for operation of the dynamometer. The application results of the system have been verified at actual diesel engine field.

• 한국산업융합학회 논문집
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• 제20권3호
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• pp.213-220
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• 2017

This paper proposes an optimal current control method for improving efficiency of Brushless Direct Current (BLDC) motor. The proposed optimal current control method is based on the maximum torque point analysis of Finite Element Analysis (FEA). The proposed method can increase the effective voltage at the maximum torque point of BLDC motor and increase the output torque per unit current to increase the efficiency. In order to verify the proposed optimal current control method, have developed the prototype of a 50 [W] class motor drive and experimented by 20 [W] motor using the dynamometer set. This was verified.

• 전력전자학회논문지
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• 제4권5호
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• pp.474-482
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• 1999

본 논문에서는 유도전동기의 전 속도 영역에서 출력토오크를 최대화 할 수 있는 새로운 약계자 제어기를 제시하였다. 전압제한과 전류제한을 모두 고려한 약계자 영역에서의 최적해를 구하였다. 제안된 알고리즘은 자속과 속도를 근거로 하여 변동하는 전압 제한 조건을 만족시키는 전류 기준값을 구하게 된다. 따라서 고정자 전압을 최대한 활용하므로 정상상태 뿐만 아니라 전동기의 자속의 크기가 변화하는 과도상태에서도 최대 출력 토오크와 빠른제어 응답성을 얻을 수 있다. 시뮬레이션 및 실험결과를 통해 제안된 약계자 기법의 효용성을 보였다.