• 제어로봇시스템학회:학술대회논문집
• /
• 1989.10a
• /
• pp.760-765
• /
• 1989

Digital control laws are implemented on an active magnetic bearing system with DSP. The results of tests using a experimental apparatus are (1) in a case that conventional PID, PIDD2 controls are employed, implemention of digital control law has similar characteristics to that of analogue control law. (2)The experiments reveal the results that the dynamic compensation based on the observer may be better than that of the other conventional controllers.

• IE interfaces
• /
• v.6 no.2
• /
• pp.171-181
• /
• 1993

In this study, a process management system is designed that can automatically control the heat treating atmosphere, and a managment software is developed to monitor and control continously the heat treating process using a n interface device. Especially, a communication protocol is developed to control and monitor atmosphere condition, temperature, surrounding gas, and time. The developed interface device, called COMPORT SELECTOR is to send and receive information from PID controllers and PLC via RS-232C communication. This system will reduce manufacturing cost and cycle time, and improve the effectiveness of working process and quality.

• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.2702-2704
• /
• 2001

In this Letter, we propose a comprehensive design methodology of hybri'd Fuzzy controllers (HFC). The HFC comes as a form of a convex combination of a standard PID controller and a fuzzy controller. The design procedure dwells on the use of evolutionary computing (genetic algorithm) and an auto-tuning algorithm. The tuning of the scaling factors of the HFC is an essential component of the entire optimization process. A numerical study is presented and a detailed comparative analysis is also included.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 1993.06a
• /
• pp.814-816
• /
• 1993

Fuzzy controllers still remain ill-accepted in the control community. As a matter of fact, their design relies on a new relation between the material world and the scientists. Whereas some theoritical studies are carried out on this subject, experimentations on processes show what fuzzy techniques can bring to the control theory.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.6
• /
• pp.633-641
• /
• 2015

Several complex processes that are employed in industries, such as shipping, power plants, and the petrochemical industry, involve time-varying behavior as well as strong nonlinear behavior during operation. The fixed-parameter proportional-integral-derivative (PID) controllers have difficulty in dealing with control problems that occur in such processes. In this paper, we propose a method of designing a nonlinear PID controller for industrial processes that exhibit a large number of nonlinearities and time-varying behavior. The gains of the nonlinear PID controller are characterized by a simple nonlinear function of the error and/or error rate depending on the process set-point and output. We tune the user-defined parameters using a genetic algorithm by minimizing the integral of time absolute error (ITAE) index. We verify the effectiveness of the proposed method by performing a comparison of the proposed method and two other nonlinear and adaptive methods that are employed for reference tracking, disturbance-rejection performances, and robustness to parameter changes on a continuously stirred tank reactor.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.2
• /
• pp.46-56
• /
• 1999

A predictive controller is designed based upon stochastic methods for compensation time-delay effect on a system which has inherent time-delay caused by the spatial separation between controllers and actuators. The predictive controller estimates current outputs through linear prediction methods and probability functions utilizing previous outputs, and minimizes the malicious phenomena caused by the time-delay in precision control systems. To demonstrate effectiveness of this control methodology, we applied this algorithm for the control of a tele-operated DC servomotor. The experimental results show that this predictive controller is superior to the PID controller in terms of convergence-characteristics, and show that this controller expands the maximum allowable time-delay for a system maintaining the stability. Since the proposed predictor does not require models of plants - it requires only stochastic information for outputs --, it is a general scheme which can be applied for the control of systems which are difficult to model or the compensator of PID control.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.5
• /
• pp.287-297
• /
• 2017

Novel power system stabilizers (PSSs) have been proposed to effectively dampen low frequency oscillations (LFOs) in multi-machine power systems and have attracted increasing research interest in recent years. Due to this attention, recently, fractional order controllers (FOCs) have found new applications in power system stability issues. Here, a tilt-integral-derivative power system stabilizer (TID-PSS) is proposed to enhance the dynamic stability of a multi-machine power system by providing additional damping to the LFOs. The TID is an extended version of the classical proportional-integral-derivative (PID) applying fractional calculus. The design of the proposed three-parameter tunable TID-PSS is systematized as a nonlinear time domain optimization problem in which the tunable parameters are adjusted concurrently using a modified group search optimization (MGSO) algorithm. An integral of the time multiplied squared error (ITSE) performance index is considered as the objective function. The proposed stabilizer is simulated in the MATLAB/SIMULINK environment using the FOMCON toolbox and the dynamic performance is evaluated on a 3-machine 6-bus power system. The TID-PSS is compared with both classical PID-PSS (PID-PSS) and conventional PSS (CPSS) using eigenvalue analysis and time domain simulations. Sensitivity analyses are performed to assess the robustness of the proposed controller against large changes in system loading conditions and parameters. The results indicate that the proposed TID-PSS provides the better dynamic performance and robustness compared with the PID-PSS and CPSS.

• Journal of Aerospace System Engineering
• /
• v.11 no.1
• /
• pp.14-21
• /
• 2017

A Linear parameterized Sigma-Pi neural network (SPNN) is applied to a tilt-duct unmanned aerial vehicle (UAV) which has a very large longitudinal stability ($C_{L{\alpha}}$). It is uncontrollable by a proportional, integral, derivative (PID) controller due to heavy stability. It is shown that the combined inner loop and outer loop of SPNN controllers could overcome the sluggish longitudinal dynamics using a method of dynamic inversion and pseudo-control to compensate for reference model error. The simulation results of the way point guidance are presented to evaluate the performance of SPNN in comparison to a PID controller.

• Journal of Mechanical Science and Technology
• /
• v.18 no.7
• /
• pp.1062-1073
• /
• 2004

We describe a looper controller design for a hot strip finishing mill in steel plants. The main function of the looper system is to balance the mass flow of the strip by accumulating material in the middle of the stands. Another function is to control the strip tension which influences the width of the strip. To ensure strip quality, it is very important to control the tension of the hot strip finishing mill. However, because there is a mutual interaction between the looper angle and the strip tension, it is difficult to control the looper system. Previous researches examined only the operation of a single stand. But it is not sufficient to examine the operation and effect of whole stands because the operation is wholly interdependent. In this paper, we present a full model of the hot strip finishing mill in order to more effectively control strip tension. We propose several control methods for the full-stand hot strip finishing mill, denoted as conventional PI, PI with cross gain, and coefficient diagram method (CDM) PID control. In the real plants, there are some problems by using higher order controllers such as LQ, LQG and H$\_$$\infty$/. By comparison, the PID controller is very simple and easy to apply to all real plants. To that end, we present our findings on PID controls and their potential use in the hot strip finishing mill.

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