• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.4
• /
• pp.365-371
• /
• 2012

This paper presents robust control performance of a direct current(DC) motor with brake system adopting a giant electrorheological(GER) fluid, whose distinguished feature is an extremely high value of yield stress. As a first step, Bingham characteristics of the GER fluid is experimentally investigated using the Couette type electroviscometer. A cylindrical type of ER brake is then devised based on the Bingham model, and its braking torque is evaluated. Structural analysis of ER break is performed using ANSYS. After formulating the governing equation of motion for the DC motor with ER brake system, a sliding mode control algorithm, which is very robust to external disturbances and parameter uncertainties, is synthesized and experimentally realized in order to achieve desired rotational speed trajectories. The tracking responses of the control system are then evaluated and verified by presenting speed control performance.

• Journal of Multimedia Information System
• /
• v.6 no.4
• /
• pp.185-190
• /
• 2019

For future autonomous cars, it is necessary to recognize various surrounding environments such as lanes, traffic lights, and vehicles. This paper presents a method of speed sign recognition from a single image in automatic driving assistance systems. The detection step with the proposed method emphasizes the color attributes in modified YUV color space because speed sign area is affected by color. The proposed method is further improved by extracting the digits from the highlighted circle region. A sequential cascade AdaBoost classifier is then used in the recognition step for real-time processing. Experimental results show the performance of the proposed algorithm is superior to that of conventional algorithms for various speed signs and real-world conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.12 no.3
• /
• pp.29-36
• /
• 1998

In this paper, We are proposed a design method of the digital PID controller based on the model following method which minimized the error integral of the step response between the control system and the reference model. And we are applied it by a speed control of the current type inverter induction motor. The dynamic characteristic of the system was expressed by the step response, and then the optimal parameter of the PID controller can be easily obtained by the matrix computation. The derived algorithm can be implemented through a simple and systematic design procedure. Finally, We have shown the result with a computer simulation by the present method which proposed the speed control system and stable operation and fairly transient performance. And then tt was found results by experimental process.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.529-538
• /
• 2015

Due to the high efficiency and compact mechanical structure, direct drive variable speed generators are used for power conversion in wind turbines. The wind energy conversion system (WECS) considered in this paper consists of a permanent magnet synchronous generator (PMSG), uncontrolled rectifier, dc-dc boost converter controlled with maximum power point tracking (MPPT) and adaptive hysteresis controlled voltage source inverter (VSI). For high utilization of the converter's power capability and stabilizing voltage and power flow, constant DC-link voltage is essential. Step and search MPPT algorithm which senses the rectified voltage ($V_{DC}$) alone and controls the same is used to effectively maximize the output power. The adaptive hysteresis band current control is characterized by fast dynamic response and constant switching frequency. With MPPT and adaptive hysteresis band current control in VSI, the DC link voltage is maintained constant under variable wind speeds and transient grid currents respectively.

• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.655-659
• /
• 2004

This paper proposes a fuzzy logic based vector control for the gearless traction machine drive systems using a permanent-magnet synchronous motor (PMSM). The performance of the proposed Fuzzy Logic Control(FLC)-based PMSM drive are investigated and compared to those obtained from the conventional PI controll-based drive system. We have confirmed theoretically and experimentally at different dynamic operating conditions such as step change in command speed, step change in load, etc. The comparative experimental results show that the FLC is more robust and, hence, found to be a suitable replacement of the conventional Pl controller for the high-performance elevator drive system.

• The Journal of Korean Physical Therapy
• /
• v.34 no.4
• /
• pp.181-186
• /
• 2022

Purpose: This study was to applied to stretching plantar flexor and invertor at the same time to observe the effect of balance and walking ability. Methods: Subjects were instructed patients with ankle limited of motion, 6 months after stroke. We classified 20 subjects into two groups (experimental group: stretching plantar flexor and invertor at the same time, control group: only stretching plantar flexor). each group included 10 subjects and applied ankle stretcher for 20 minutes, 5 times/week during 4 weeks (total 20 times). Results: Both experimental group and control group showed significant increases in static balance, however, the significantly increases in step length and gait speed was observed only in the experimental group. There was no significant increases in step length and gait speed in the control group. Conclusion: Simultaneous stretching of ankle invertor and plantar flexion is effective in improving balance and walking ability in chronic stroke patients.

• Proceedings of the KIEE Conference
• /
• 1997.07b
• /
• pp.696-698
• /
• 1997

The marine diesel engine have been widely applied with a mechanical hydraulic governor to control the ship speed for long time. But it was recently very difficult for the mechanical hydraulic governor to control the speed of engine under the condition of low speed and low load because of jiggling by rough fluctuation of rotating torque and hunting by dead time of diesel engine. In order to analyze the speed control system the transfer function was converted from z to w transformation. The author proposed velocity control system with feedback loop by PID controller in order to stabilize for unstable area. The influence of dead time was discussed by Nichols chart and unit step response curve. It was confirmed through computer simulation that the performance improvement of a mechanical hydraulic governor can be obtained by PID controller.

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.538-541
• /
• 2005

Most realistic control systems contain nonlinearities of some form. One nonlinearity commonly found in control systems is a saturating element. If integral control is applied to such a system to eliminate steady state error, an undesired side effect known as integrator windup may occur when lage setpoint changes are made. This effect leads to a characteristic step response with a large overshoot and a very high settling time. To avoid this situation, many different anti-windup strategies have been suggested. But existing strategies remain over shoot and high settling time. This paper proposes a new anti-windup strategy for PI speed controllers. When the speed control system is changed P controller to PI controller. Integrator has an appropriate initial value. This value results over shoot and high settling time. The SIMULINK/MATLAB-based comparative simulation results and experiment results of speed controller have shown its superior control performance to that of a proposed anti-windup speed controller.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1118-1119
• /
• 2007

Switched Reluctance Motor has advantages such as simple structure, low cost and so on compared with induction motor. Efficiency is higher than induction motor, so there is beneficial cost. Also torque character has essential character of superiority step motor and a DC motor character that depends on variable speed. This paper presented the research of speed and current control system of SRM using the DSP. At first, a simulation model on Matlab/simulink was performed. SRM speed control algorithm investigated the control method. Then driver and control system developed to do experiment.

• Journal of Power Electronics
• /
• v.18 no.3
• /
• pp.714-722
• /
• 2018

This paper presents a wide-range speed control scheme of brushless DC (BLDC) motors based on a hall sensor with separated low- and normal-speed controllers. However, the use of the hall sensor signal is insufficient to detect motor speed in the low-speed region because of low sensor resolution and time delay. In the proposed method, a micro-stepping current control method according to the torque angle variation is presented. In this mode, the motor current frequency and rotating angle are determined by the reference speed without the actual speed fed by the hall sensor. The detected torque angle is used to adjust the current value in a limited band to control the current value in accordance with the load. The torque angle is detected exactly at the changing point of the hall sensor signal. The rotor can follow the rotating flux with the variable torque angle. In a normal speed range, the conventional vector control scheme is used to control the motor current with a PI speed controller using the hall sensor. The torque characteristics are analyzed on the basis of the back EMF and current shape. To adopt the vector control scheme, the continuous rotor position is estimated by the measured speed and hall sensor position. At the mode changing point between low and normal speed range, the proper initial current command and reference rotor position are calculated. The calculated current command can reduce the torque ripple during transient mode. The proposed method is simple but effective in extending the speed control range of a conventional BLDC motor with hall sensor without the need for a high-resolution encoder. The effectiveness of the proposed method is verified by various experiments on a practical BLDC motor.