• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.9
• /
• pp.935-939
• /
• 2015

This paper describes sensorless speed control of brushless DC motors by using direct torque control. Direct torque control offers fast torque response, robust specification of parameter changes, and lower hardware and processing costs compared to vector-controlled drives. In this paper, the current error compensation method is applied to the sensorless speed control of a brushless DC motor. Through this control technique, the controlled stator voltage is applied to the brushless DC motor such that the error between the stator currents in the mathematical model and the actual motor can be forced to decay to zero as time proceeds, and therefore, the motor speed approaches the setting value. This paper discusses the composition of the controller, which can carry out robust speed control without any proportional-integral (PI) controllers. The simulation results show that the control system has good dynamic speed and load responses at wide ranges of speed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.8
• /
• pp.905-912
• /
• 2011

In order to protect equipment such as controllers, it is important to improve the driving stability of $6{\times}6$ skidsteering vehicles driven on rough roads. The estimation and improvement of the driving stability should be based on the vertical acceleration, roll acceleration, and pitch acceleration. These variables will be used to achieve multivariable control and increase the vehicle driving stability. In this study, to improve vehicle stability by reducing the vertical acceleration, roll angular acceleration, and pitch angular acceleration, the skyhook control method is employed to control MR(Magnetorheological) dampers equipped with the vehicle. The proposed control system is tested in multibody dynamic simulation.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.20 no.1
• /
• pp.109-115
• /
• 2010

A main technology of opening and closing a sluice gate is accurate synchronous and position control for the two cylinders when they are moving with the sluice gate together over 10[m]. Since the supply flow and supply pressure of cylinders are not constant and a nonlinear friction force of the piston in cylinders exists, a difference will be made between the displacement of two cylinders. This difference causes the sluice gate to deform and abrade, and even it may be out of order. In order to solve this problem we design two kinds of fuzzy PI controllers. The former is for a position control of two cylinders, the latter is for their synchronous control. We show some simulation results compare the performance of fuzzy PI controller to the conventional PID controller.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.24 no.3
• /
• pp.330-336
• /
• 2014

Many industrial processes such as continuous stirred tank reactors(CSTRs), desalination plant, distillation columns, pH neutralization processes and so on exhibit highly nonlinear characteristic and time-varying behavior during operation. The control of such processes has been challenging to control engineers. Hence, a variety of forms of PID controllers and their tuning rules for industrial processes have been developed to guarantee the best performance. In this paper, a scheme that designs the practical PID controller with an anti-windup strategy incorporating with an evolutionary algorithm(EA) is presented for the concentration control of a nonisothermal CSTR. EA is used to tune the parameters of the overall PID control process with anti-windup by minimizing the integral of absolute error(IAE). Simulation works for reference tracking and disturbance rejecting performances and robustness to parameter changes show the feasibility of using the proposed method.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.24 no.3
• /
• pp.279-284
• /
• 2014

This paper proposes a optimum design method for the Fuzzy PID controller of magnetic levitation-based Rail-Guided Vehicle(RGV). Since an attraction type levitation system is intrinsically unstable, it is difficult to completely satisfy the desired performance through the methods designed by conventional controllers. In the paper, the Fuzzy PID controller with fixed parameters are applied and then the optimum parameters of fuzzy PID controller are selected by genetic algorithm. For the fitness function of genetic algorithm, the performance index of PID controller is used. To verify the performance of the proposed method, we used Matlab/simulink model of Maglev and compared the proposed method with the performance of PID controller. The simulation results show that the proposed method is more effective than conventional PID controller.

• Journal of Drive and Control
• /
• v.15 no.1
• /
• pp.28-37
• /
• 2018

When the wind speed rises above the rated wind speed, the produced power of the wind turbines exceeds the rated power. Even more, the excessive power results in the undesirable mechanical load and fatigue. A solution to this problem is pitch control of the wind turbines. This paper presents a systematic design method of a collective pitch controller for the wind turbines using a discrete fuzzy Proportional-Integral (PI) controller. Unlike conventional PI controllers, the fuzzy PI controller has variable gains according to its input variables. Generally, tuning the parameters of fuzzy PI controller is complex due to the presence of too many parameters strongly coupled. In this paper, a systematic method for the fuzzy PI controller is presented. First, we show the fact that the fuzzy PI controller is a superset of the PI controller in the discrete-time domain and the initial parameters of the fuzzy PI controller is selected by using this relationship. Second, for simplicity of the design, we use only four rules to construct nonlinear fuzzy control surface. The tuning parameters of the proposed fuzzy PI controller are also obtained by the aforementioned relationship between the PI controller and the fuzzy PI controller. As a result, unlike the PI controller, the proposed fuzzy PI controller has variable gains which allow the pitch control system to operate in broader operating regions. The effectiveness of the proposed controller is verified with computer simulations using FAST, a NREL's primary computer-aided engineering tool for horizontal axis wind turbines.

• Journal of Korea Multimedia Society
• /
• v.13 no.5
• /
• pp.771-779
• /
• 2010

Sketch-based interface is used more and more in developing animation contents. Particularly, there has been a system where the user's sketch inputs are interpreted and presented as live motions. In this study¸ it is to design an animated flight learning system using sketch-based interface. Most of the flights include movements in three-dimensional space and have unique and complex flight patterns. In other words, the actual flight movements not only include acceleration and deceleration, rising and falling, straight or circular flying, but also may include combinations of two or more movements as they simultaneously occur such as accelerating while falling, or slowing down while rising, and so forth. And, currently existing flight learning animation system cannot present such complex flight patterns to the pilots of aircrafts or to those personnel for air-traffic controllers. Hence, it is to be shown in this study that unit-path sketch animation method can support quicker ways to create animations to present those complex flight movements, and requires lesser inputs compared to the existing frame-based animation method. Also, the flight learning system suggested uses the flight-route realization tasks to reflect complex flight patterns, and therefore creates animations close to real as possible.

• Journal of Advanced Navigation Technology
• /
• v.11 no.2
• /
• pp.137-145
• /
• 2007

The flight test of ADS-B is to demonstrate operational benefits to air traffic controllers and pilots when other aircraft data including the aiming altitude is displayed on CDTI. Additionally, This ADS-B study is to provide first operational experience of ADS-B in ATCS environment of South Korea and provide practical information to ATCS before deployment of ADS-B in South Korea is considered. Participation in the flight test has been limited to 2 Aircraft of H University which are installed ADS-B equipment and the ground station has installed in Tae-An airport. This test have been experimented according to the pre-arranged flight procedures of Tae-An airport. As a result of the test, it has shown that the number of radio transmitting and the time of radio occupied between controller and pilot are remarkably reduced. Besides, as both pilot and air traffic controller are able to see the traffic information in the vicinity of the aircraft, the test has demonstrated that it is possible for ADS-B not only to decline the controller's workload, but also to enhance pilot situational awareness in the near future.

• Journal of Advanced Navigation Technology
• /
• v.22 no.5
• /
• pp.367-374
• /
• 2018

A trajectory-based scheduling system is proposed for air traffic management using next generation aviation data communication link. Based on the service concept of 4-dimensional trajectory data link (4DTRAD) using air traffic serveices (ATS) datalink Baseline 2, a procedure for trajectory-based operation of an en-route flight is established and described in detail. To mitigate air traffic controllers' workload which might be caused by various and complicated data utilization, a prototype of the scheduling system, which predicts the aircraft trajectory based on the flight intents received by air traffic service system and provides advisory information for air traffic control, was developed. The simulation environment for trajectory based operation was built to validate the scheduling functionality of the prototype.

• Investigative Magnetic Resonance Imaging
• /
• v.19 no.1
• /
• pp.1-9
• /
• 2015

Purpose: Several morphometric studies have been performed to investigate brain abnormalities in congenitally deaf people. But no report exists concerning structural brain abnormalities in congenitally deaf adolescents. We evaluated the regional volume changes in gray matter (GM) using voxel-based morphometry (VBM) in congenitally deaf adolescents. Materials and Methods: A VBM8 methodology was applied to the T1-weighted magnetic resonance imaging (MRI) scans of eight congenitally deaf adolescents (mean age, 15.6 years) and nine adolescents with normal hearing. All MRI scans were normalized to a template and then segmented, modulated, and smoothed. Smoothed GM data were tested statistically using analysis of covariance (controlled for age, gender, and intracranial cavity volume). Results: The mean values of age, gender, total volumes of GM, and total intracranial volume did not differ between the two groups. In the auditory centers, the left anterior Heschl's gyrus and both inferior colliculi showed decreased regional GM volume in the congenitally deaf adolescents. The GM volumes of the lingual gyri, nuclei accumbens, and left posterior thalamic reticular nucleus in the midbrain were also decreased. Conclusions: The results of the present study suggest that early deprivation of auditory stimulation in congenitally deaf adolescents might have caused significant underdevelopment of the auditory cortex (left Heschl's gyrus), subcortical auditory structures (inferior colliculi), auditory gain controllers (nucleus accumbens and thalamic reticular nucleus), and multisensory integration areas (inferior colliculi and lingual gyri). These defects might be related to the absence of general auditory perception, the auditory gating system of thalamocortical transmission, and failure in the maturation of the auditory-to-limbic connection and the auditorysomatosensory-visual interconnection.