• Korean Journal of Chemical Engineering
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• v.36 no.3
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• pp.356-367
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• 2019

This work presents an advanced and systematic approach to analytically design the optimal parameters of a two parameter second-order internal model control (IMC) filter that satisfies operational constraints on the output process, the manipulated variable as well as rate of change of the manipulated variable, for a first-order plus dead time (FOPDT) process. The IMC parameters are designed to minimize a control objective function composed of the weighted sum of the error between the process variable and the set point, and the rate of change of the manipulated variable, and to satisfy the desired constraints. The feasible region of the constrained IMC control parameters was graphically analyzed, as the process parameters and the constraints varied. The resulting constrained IMC control parameters were also used to find the corresponding industrial proportional-integral controller parameters of a Smith predictor structure.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.439-440
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• 2023

본 논문에서는 차량의 상태를 실시간으로 모니터링하고, 중요한 정보를 운전자에게 효과적으로 제공하는 시스템을 제안한다. 본 논문에서 개발한 차량 운행 정보시스템은 블루투스 OBD2 커넥터를 통해 차량의 PID 값을 식별 및 수집하고, 이를 라즈베리파이와 7인치 터치 디스플레이를 이용하여 운전자에게 한눈에 보일 수 있는 형태로 정보를 제공한다. 수집된 데이터는 실시간으로 SD 카드에 저장되며, 차량에 이상이 생겼거나 사고가 발생했을 때, 이를 입증하기 위한 참고자료로 활용될 수 있을 것으로 기대된다.

• Journal of Drive and Control
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• v.12 no.4
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• pp.60-70
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• 2015

A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within $1^{\circ}$ and a mean of delayed times of ~ 0.8s when the step input of $+20^{\circ}$ was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.565-570
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• 2011

In this paper, the analytical tuning rules of the proportional-integral-derivative (PID) controller have been derived for a broad class of stable, integrating, and unstable processes without time delay. On the basis of the renowned internal model control (IMC) design principles and the two-degree-of-freedom (2DOF) control structure, the proposed method can be effectively used for obtaining the enhanced performances of both the disturbance rejection as well as the set-point tracking problems, since the design scheme is simple, straightforward, and can be easily implemented in the process industry. Several processes without time delay are employed to demonstrate the improved closed-loop performance of the proposed controller design in compared with the other well-known design methods in terms of the same degree of robustness.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.1-8
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• 2011

This paper describes a new method for a digital gas metal arc welding (GMAW) system. The GMAW system is an arc welding process that incorporates the GMAW power source (PS-GMAW) with a wire feed unit (WFU). The PS-GMAW requires an electric power of constant voltage. A constant magnitude is maintained for the arc current by controlling the wire-feed speed of the WFU. A mathematical model is derived, and a self-tuning fuzzy proportional-integral-derivative (PID) controller is designed and applied to control the welding current. The electrode wire feeding mechanism with this controller is driven by a DC motor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. By accurately maintaining the output welding current and welding voltage at constant values during the welding process, excellent welding results can be obtained. Simulation and experimental results are shown to prove the effectiveness of the proposed controller.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.3 no.2
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• pp.113-119
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• 1999

The quality of the effluent from an activated sludge aeration tank can deteriorate when the substrate removal rate decreases due to an abrupt reduction in the DO concentration, which is affected by such operating conditions as the loading rate, temperature, wastewater composition, and so on. In this research, a DO control system that includes a PI (proportional-integral) controller/Hiraoka controller was developed and applied to a pilot-scale activated sludge process, then its acceptability was estimated. The applicability of the respiration rate to DO control was also estimated. The respiration rate indicated a variety of input organic loading rates, which is the main disturbance to the DO concentration in an aeration tank. When the influent concentration incrementally decreased and increased between CODcr 1,000 mg/l and 100 mg/l, the control system with a PI controller exhibited a good llperformance-the average DO concentrations were 2.00$\pm$0.14 mg/l and 1.88$\pm$0.15 mg/l (set value was 2.0 mg/l), respectively, and the settling time was just 10 minites. When the control system was operated for 4 days, the DO concentration was 1.99$\pm$0.18 mg/l and 32.6% of the air flowrate was saved. However, the fluctuations in the respiration rates and air flowrates were severe, which could be harmful to the stability of the biomass and mechanical stability of the blower. A possible approach to solve this problem may be the simultaneous control of the loading rate and DO concentration.

• Journal of Biosystems Engineering
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• v.31 no.3 s.116
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• pp.203-208
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• 2006

This study was conducted to improve the control performance of a current variable-rate controller for granular fertilizers. Simulation model was developed. Optimized proportional, integral and derivative gains were determined by simulation model using 2nd order PID gain learning algorithm, and these control gains were evaluated through the field tests. Important results of this study are as follows; 1. Principles of pre-existing variable-rate application of granular fertilizers were investigated. 2. Simulation model of a PID controller that could simulate the control system was developed by using Matlab/Simulink program. The program was to determine PID control coefficients through the simulation model and 2nd order PID gain learning algorithm. 3. PID control coefficients obtained from the simulation were applied to the developed model. When the step input was given, Maximum overshoot were 1.96%, rise time were 0.05 sec, settling time were 0.06 sec and steady state error were 0.21 % respectively. 4. The simulation model was verified through field tests. The errors of maximum overshoot were 10%, rise time were 0.11 sec, settling time were 0.40 sec and steady state error were 8% because of loads and noises. Rise time was decreased to one third of that of the pre-existing system. 5. If the speed of a fertilizing machine is $0.3{\sim}0.6\;m/s$ and the maximum rotation speed of a discharging roller is 64 rpm, rise time would be 0.26 sec and fertilizing machine would cover the distance of $0.07{\sim}0.15\;m$ with settling time of 0.4 sec, fertilizing machine would cover the distance of $0.12{\sim}0.24\;m$.

• Journal of IKEEE
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• v.24 no.1
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• pp.154-160
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• 2020

This paper presents a grid current control algorithm for a grid connected inverter (GCI) system in a stationary reference frame. When a Proportional Integral (PI) controller at a stationary reference frame is used in a GCI system, steady state error and phase lags are presented because AC signals are controlled at a stationary reference frame. In this paper, a feedforward controller is applied to the PI controller to compensate the steady state error and phase lags by improving command tracking performance. In addition, disturbance rejection control is applied to the PI controller to protect the GCI system by eliminating disturbance, grid voltage in a GCI system, when a grid fault such as line-to-line fault, happens. The proposed GCI current control algorithm is analyzed in a frequency domain and a simulation model of the proposed GCI current control system is developed for verification of the performance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.290-294
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• 2014

PID(Proportional, Integral, Derivative) controller is the most popular process controllers in nuclear power plants. The optimized parameter setting of the process controller contributes to the stable operation and the efficiency of the operating nuclear power plants. PID parameter setting is tuned when new process control systems are installed or current process control systems are changed. When the nuclear plant is shut down, a lot of PID tuning methods such as the Trial and Error method, Ultimate Oscillation method operation, Ziegler-Nichols method, frequency method are used to tune the PID values. But inadequate PID parameter setting can be the cause of the unstable process of the operating nuclear power plant. Therefore the results of PID parameter setting should be simulated, optimized and finally verified. This paper introduces the simulation method of PID tuning to optimize the PID parameter setting and confirms them of the actual PID controller in the operating nuclear power plants. The simulation method provides the accurate process modeling and optimized PID parameter setting of the multi-loop control process in particular.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.12
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• pp.782-790
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• 2011

Typical temperature control methods of a cooler for machine tools are hot-gas bypass and compressor variable speed control. The hot-gas bypass system has been widely used to control the cooler temperature in many general industrial fields. On the contrary, the compressor variable speed control is focused on special fields such as aerospace and high precision machine tools which need high precision control. The variable speed control system usually has two control variables such as target temperature and superheat. In other words, the variable speed control system is basically multi-input multi-output(MIMO) system. In spite of MIMO system, the proportional integral derivative(PID) feedback control methodology that based on single-input single-output (SISO) system is generally used for designing the variable speed control system. Therefore, it is inevitable to describe transfer functions for dynamic behaviors of every controlled variables and decide the PID gains with tremendous iteration process. Moreover, the designed PID gains do not provide optimum system performances. To solve these problems, high performance controller design method based on a state space model is suggested in this paper. An optimum controller is designed to minimize both control errors and energy inputs. This method was more simple to describe dynamic behaviors and easier to design the cooler controller which is MIMO system.