• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.1
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• pp.7-14
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• 2015

To implement an automatic picking system (APS) in distribution center with high precision and high dynamics, this paper presents a high gain observer-based robust speed controller design for a linear induction motor (LIM) drive. The force disturbance as well as the mechanical parameter variations such as the mass and friction coefficient gives a direct influence on the speed control performance of APS. To guarantee a robust control performance, the system uncertainty caused by the force disturbance and mechanical parameter variations is estimated through a high gain disturbance observer and compensated by a feedforward manner. While a time-varying disturbance due to the mass variation can not be effectively compensated by using the conventional disturbance observer, the proposed scheme shows a robust performance in the presence of such uncertainty. A Simulink library has been developed for the LIM model from the state equation. Through comparative simulations based on Matlab - Simulink, it is proved that the proposed scheme has a robust control nature and is most suitable for APS.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.4
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• pp.106-117
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• 2021

In Korea, interest in truck platooning is increasing because most cargo transportation is done by road. Truck platooning is the operation of two or more trucks in a row to form one platoon, which can increase road capacity and improve fuel efficiency. In this study, to analyze the effect of truck platooning on traffic flow, scenarios were created according to traffic conditions and truck platooning operating conditions. In order to understand the effect of the truck platooning operating conditions, correlation analysis was conducted with the average travel speed, the number of lane change disturbance, and the number of disturbance in the entry/exit section. As a result, the number of trucks in the platoon, the spacing of trucks in the platoon, and the spacing between platoons were found to have an effect on the average speed and the number of lane change disturbance In addition, the truck platooning ratio was found to have a strong correlation with the average travel speed and the number of lane change disturbance regardless of the LOS.

• International Journal of Control, Automation, and Systems
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• v.1 no.2
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• pp.171-177
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• 2003

In this paper, we investigate a robust $H_{\infty}$ state feedback control technique for continuous time bilinear systems with an additive disturbance input. The nonlinear robust $H_{\infty}$control for bilinear systems requires a solution to the state dependent algebraic Riccati equation (SDARE). We present a new robust $H_{\infty}$control technique based on the successive approximation method for solving the SDARE by converting bilinear systems into time-varying linear systems. The proposed control method guarantees robust stability for closed loop bilinear systems. The proposed algorithm is verified by numerical examples.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.660-663
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• 1997

In recent manufacturing process, the increase of productivity is required by reducing machining time with the increase of cutting force. However, the excessive increase of cutting force can cause tool breakage, and have a bad effect on both the manufacturing machine and the workpiece. Thus, it is necessary to estimate and control cutting force in real time during the process. In this study, use of disturbance observer is proposed for the indirect cutting force estimation. The estimated cutting force is used for the real time control of feedrate, making the actual cutting force follow the reference force command. Since the suggested method does not need an expensive sensor like a dynamometer, the method is expected to be used practically. By reducing the machining time resulting from making the actual cutting force follow the reference force, the increase of productivity are also expected, and the quality of cutting surface has been improved due to the adjusted feedrate. Besides, an actual constant cutting force guarantees the prevention of tool breakage. To show the effectiveness of the suggested cutting force control method, an experimental setup has been made without the force sensor, applied to several workpieces. Experiments show that the suggested method is superior to the conventional method operated by constant feedrate.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.700-703
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• 1997

A robust controller for a 6 DOF magnetically levitated fine manipulator is presented. The proposed controller consists of following two parts : a model reference controller (MRC) and a H$_{\infty}$ controller (HIC). First, the MRC stabilizes the motion of the manipulator. Then, the motion of the manipulator follows that of the reference model. Second, the HIC minimizes errors generated from the MRC due to noise and disturbance since the HIC is a kind of robust controller. The experiments of position control and tracking control are carried out by use of the proposed controller under the conditions of free disturbances and forced disturbances. Also, the experiments using PID controller are carried out under the same conditions. The results from above two controllers are compared to investigate the control performances. As the results, it is observed that the proposed controller has similar position accuracy but better tracking performances comparing to the PID controller as well as good disturbance rejection effect due to the robust characteristics of the controller. In conclusion, it is verified that the proposed controller has the simple control structure, the good tracking performances and good disturbance rejection effect due to the robust characteristics of the controller..

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.438-443
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• 2003

In this paper, we propose a control algorithm for two-wheel mobile robot that can move the rider to his or her command and autonomously keep its balance. The control algorithm is based on a mixed $H_2/H_{\infty}$ control scheme. In this control problem the main issue is to move the rider while keeping its balance in the presence of disturbances and parameter uncertainties. The disturbance force caused by uneven road surfaces and the uncertainty due to different rider's heights are considered. To this end we first consider a state feedback controller as a basic framework. Secondly, we obtain the state feedback gain $K_2$ minimizing the $H_2$ norm and the state feedback gain $K_{\infty}$ minimizing the $H_{\infty}$ norm over the whole range of parameter uncertainty. Finally, we select mixed $H_2$/$H_{\infty}$ state feedback controller K as the geometric mean of $K_2$ and $K_{\infty}$. Simulation results show that the mixed $H_2/H_{\infty}$ state feedback controller combines the effects of the optimal $H_2$ state feedback controller and robust $H_{\infty}$ controller state feedback controller efficiently in the presence of disturbance and parameter uncertainty.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.627-634
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• 1998

This paper proposes an algorithm which improves capacity of a state observer and low speed driving characteristics of a induction motor by inertia moment identification. In induction motet driving systems, it is difficult to obtain the accurate speed information by a low resolution encoder because the encoder pulses are very few in a low speed range. To improve this problem, state observer based on the Gopinath' theory which estimates speed and disturbance was designed, and disturbance rejection control was realized by application of the observer. Also, inertia moment of the motor was estimated and the nominal inertia of the observer was identified to minimize the error of estimated speed and disturbance. From the simulation and experimental results, it is showed that the proposed observer improved the transient response characteristics in low speed region below 6［rpm］.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1555-1561
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• 2018

Tracking and detecting targets by the millimeter wave seeker is affected by movement of platform. Stabilization equipments use an inertial sensor to compensate for disturbance of stabilizing gimbal or platform. In the direct line of sight stabilization system, an inertial sensor is mounted on inner gimbal to compensate the disturbance directly, so the performance is excellent and the implementation method is simple. However gimbal design requires somewhat larger volume. Since an inertial sensor is mounted on gimbal base in the indirect line of sight stabilization system, additional space of gimbal is not required for the gimbal design. However, this method does not directly compensate for the disturbance of the line of sight stabilization axis, which can degrade performance. In order to perform the tracking performance, two methods are analyzed for line of sight stabilization performance based on direct and indirect of a 2-axis gimbaled servo system for millimeter wave seeker in this study. The simulation and experimental results validate the performance comparison of two methods.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.4-9
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• 1999

A new control method for precision robust position control of a brushless DC (BLDC) motor using asymptotically stable adaptive load torque observer is presented in the paper. Precision position control is obtained for the BLDC motor system approximately linearized using the field-orientation method Recently, many of these drive systems use BLDC motors to avoid backlashe. However, the disadvantages of the motor are high cost and complex control because of nonlinear characteristics. Also, the load torque disturbance directly affects the motor shaft. The application of the load torque observer is published in [1] using fixed gain. However, the motor flux linkage is not exactly known for a load torque observer. There is the problem of uncertainty to obtain very high precision position control. Therefore a model reference adaptive observer is considered to overcome the problem of unknown parameter and torque disturbance in this paper. The system stability analysis is carried out using Lyapunov stability theorem. As a result, asymptotically stable observe gain can be obtained without affecting the overall system response. The load disturbance detected by the asymptotically stable adaptive observer is compensated by feedforwarding the equivalent current which gives fast response. The experimenta results are presented in the paper.

• Ocean Systems Engineering
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• v.8 no.2
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• pp.167-182
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• 2018

RTI (Rayleigh-Taylor instability) is investigated by a multi-liquid MPS (Moving Particle Semi-implicit) method for both viscous and inviscid flows for various density differences, initial-disturbance amplitudes, viscosities, and surface tensions. The MPS simulation can be continued up to the late stage of high nonlinearity with complicated patterns and its initial developments agree well with the linear theoretical results. According to the relevant linear theory, the difference between inviscid and viscous fluids is the rising velocity at which upward-mushroom-like RTI flow with vortex formation is generated. However, with the developed MPS program, significant differences in both growing patters and developing speeds are observed. Also, more dispersion can be observed in the inviscid case. With larger Atwood (AT) number, stronger RTI flows are developed earlier, as expected, with higher potential-energy differences. With larger initial disturbances, quite different patterns of RTI-development are observed compared to the small-initial-disturbance case. If AT number is small, the surface tension tends to delay and suppress the RTI development when it is sufficiently large. Interestingly, at high AT number, the RTI-suppressions by increased surface tension become less effective.