• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1052-1057
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• 1993

A scara type Direct Drive Arm(DDA) with two degrees-of-freedom is designed and implemented. The direct drive motor is used to furnish large torque to reduce the modeling error by the gear and chains. To control the DDA, a multiprocessor control structure with multirate dynamic control algorithm is designed. In the control algorithm, the dynamics of system is used to calculate the nominal control torque and the feedback controls are calculated with a parallel processing algorithm for each joint. The laboratory experiments on Hong-Ik DDA by dynamic control algorithm are presented and compared to that of PID control algorithm. This result shows that the proposed controller guarantees small trajectory error and stability. With this research, Hong-Ik DDA is expected to be utilized as A basic tool for robotics and control engineering.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.428-433
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• 1994

This investigates the feasibility of applying fuzzy ogic controllers to the motion tracking control of a direct drive robot manipulator to deal with highly nonlinear and time-varying dynamics associated with robot motion. A fuzzy logic controller with narrow shape of membership functions near zero and wide shape far away zero is analyzed. Simulation and experimental studies have been conducted for a 2 degree of freedom direct drive SCARA robot to evaluate control performances, Fuzzy logic controllers have shown control performances that are often better, or at least, as good as those of conventional PID controllers. Furthermore, the control performance of fuzzy logic controllers can be improved by selecting membership functions of narrow shapes near zero and wide shapes far away zero.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.507-514
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• 2001

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the classical controller is designed using the analytical Bode method.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1391-1396
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• 2009

The direct drive motor used in a precision motion rotate at about 1/10 speed and high torque comparing with general rotary motor. Excessive heating of the coils cause an exacerbating the heat problems and reducing the performance of motor. Because the rotation speed of the rotor and surrounding air is low, the motor can not be inefficiently cooled, the thermal analysis in the motor is very important. As the variations of rotation speed and torque, the temperature of several parts is measured and the features of the heat transfer is analyzed and improved.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.3
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• pp.14-19
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• 2004

The Direct Drive Valve used in this study contains a pressure-feedback-loop in itself, then it can eliminate nonlinearity such as the square-root-term in flow rate calculation and the change of bulk modulus of hydraulic oil. In this study, assuming that the dynamic characteristic of the DDV is modelled as a first order lag system, an parameter identification method using the input data and the output data is applied to obtain DDV's mathematical model. Then, a state feedback controller was designed to implement the force control of hydraulic system, and the control performance was evaluated.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.337-342
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• 2005

Direct torque control (DTC) was originally developed for induction machine drives, and, more recently has been applied to permanent magnet brushless AC (BLAC) drives. In this paper, the performance of DTC controlled brushless DC (BLDC) drives is compared with that of PWM current controlled BLDC drives, both with and without current shaping. Both simulation and experimental results are presented, as well as the analysis of the resulting torque waveforms. It is shown that, in addition to exhibiting a fast torque response, a DTC controlled BLDC drive has a significantly lower low-frequency torque ripple than the PWM current controlled BLDC drive without current shaping, and that it is easier to implement than PWM current control with current shaping.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.136-136
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• 2000

The direct drive servo valve(DDV) is composed of a DC rotor, link, valve spool and displacement sensor(LVDT) where the spool is directly coupled to the DC motor through the link. Since the DDV is a kind of one-stage valve, the robust controller is required to overcome the flow force effect on the spool motion. The mathematical equations are derived and the stability, accuracy and response speed of a DDV are investigated analytically using a linearized system block diagram. Proportional control, PID control. Time-Delay control, Sliding Mode control, and Proportional control using the load pressure are applied to DDV to find which one shows the best control performance. The digital computer simulation results show that the proportional control using the load pressure satisfies the design requirement of response speed and steady state error regardless of the variation of load pressure,

• Journal of Magnetics
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• v.16 no.4
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• pp.379-385
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• 2011

This paper presents an optimal design of a direct-drive permanent magnet synchronous generator for a small-scale wind energy conversion system. An analytical model of a small-scale grid-connected wind energy conversion system is presented, and the effects of generator design parameters on the payback period of the system are investigated. An optimization procedure based on genetic algorithm method is then employed to optimize four design parameters of the generator for use in a region with relatively low wind-speed. The aim of optimization is minimizing the payback period of the initial investment on wind energy conversion systems for residential applications. This makes the use of these systems more economical and appealing. Finite element method is employed to evaluate the performance of the optimized generator. The results obtained from finite element analysis are close to those achieved by analytical model.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1860-1865
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• 2008

The propulsion for locomotive application has changed from the DC motor system to the induction motor system. Although the induction motor system has almost reached the stage of maturity, this system also needs to be changed to the PM motor system for the direct drive without using reduction gear. Thus, the IPMSM(Interior buried Permanent Magnet Synchronous Motor) has been adopted to meet the locomotive driving specification. In this paper, the design of IPMSM satisfying driving specifications for the direct drive has been performed using the advanced F.E.M.

• Journal of Industrial Technology
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• v.18
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• pp.329-334
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• 1998

The purpose of this study is to design and manufacture a vibration exciter, which can be used in the education and research for the vibration engineering. For this purpose, a direct drive type vibration exciter is developed, which consists of a motor, an inverter, eccentric rotating sleeves and two excitation plates. Developed exciter is tested on some dynamic characteristics to evaluate its excitation performance. Test results show that the developed machine can excite bodies on the horisontal vibrating plates in x,y direction by the constant displacement amplitude in the frequency range below 50Hz, which confirm that the exciter can be used as a vibration testing machine in the low frequency range.