The Research on the System of Double-Holding Water Tank Liquid Level Control with the PID Control

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland The Research on the System of Double-Holding Water Tank Liquid Level Control with the PID Control Miao Yu 1, a, Hong-li Jia 2,b and Pan-jie Chen 3,c 1,2,3 Harbin institute of petroleum,harbin,china a @qq.coml, b @qq.com, c @qq.com Keywords: water level control; hysteresis control; PID setting; response curve Abstract. Double tank level control system is the combined control with the host computer and basic instrument, and it realizes the communicative function through monitoring and management. The object of this topic is mainly on double-tank system, then gets the theoretical parameters PID through measuring the characteristic curves of the water level, and finally use MCGS configuration software on PC, for further interaction interface to the parameters tuning of double-holding water tank system and to set the parameters. After reaching the expected target, on the base of routine control PID, we can improve the system function by forming the double loop system and control the liquid level of the water bank better. The two tank liquid level control is made as the core control system by computer and as one kind of fashionable trends. Introduction The process control is directly involved in the case in the absence of human, but involved in the case of the control device, on the production process, process parameters, objectives and requirements for the automatic adjustment and control, which can meet the requirements of the index according to the expected target[1]. With the development of computer control devices based on the control instruments, the methods of automation control is also more and more abundant, and they are widely used in industrial field, such as the intelligent digital instruments control system, the intelligent instrument and computer configuration software control system, the system computer DDC control system, the PLC control system, the DCS distributed feeder control system, and the FCS field bus control system etc. THJ-2 advanced process control experimental system will be the base to design the control system and engineering realization in the design of liquid level cascade control system. Although the method of traditional cascade PID control is adopted, intelligent instrument, data acquisition module and the computer control will be used to realize the control system, so as to make the system have good static performance and improve the dynamic performance of the system. Two step tuning method adjusting instrument parameters PID[2] The main regulator ratio is at 100%, in stable condition, and main loop closes the main and auxiliary regulator in the pure proportional loading conditions, to get the secondary regulator proportion and operation cycle with a damping oscillation of single loop control system tuning. To put the Deputy regulator proportion in (1) values of the request, the vice loop as a part of the main loop, using the same method of tuning circuit, and calculating the main loop proportion and operation cycle. According to the above requested data, the main and auxiliary regulator ratio can be calculated by single loop system damping oscillation tuning formula, numerical value of integral time and calculus time. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-05/03/16,21:15:12)

2 2560 Advances in Manufacturing Science and Engineering V According to first vice principal, proportion integral, adding differential setting program, properly, setting the main and auxiliary regulator parameters, observing recovery curve, and make appropriate adjustments when necessary, until the system reaches the best quality. Designing steps Process of control analysis: If the level rises, the measured value increases, and the controller output reduces. For the actuator is positive the valve opening become smaller, and the input reduces and the liquid level drops. Conversely, if the level drops, the measured value decreases, controller output increases. For the actuator is positive, the valve opening become bigger, the input increases, the liquid level rises. Control flow chart Fig.1 Instrument selection[3] Fig.1 The control box Inverter: we selected Mitsubishi inverter FR-S500 in the design; electric control valve. Liquid level transmitter: the selected model for JYB-KO-PAG; Flow transmitters thermal resistance: the platinum thermal resistance Pt100 is selected; Artificial intelligent digital controller: the selected model for AI-818; Host: it mainly plays a role of monitoring, parameter setting, setting the given value, establishing communication, making historical curve and the current process control curve, data report, establishing process and control screen. Parameter setting Ctrl=1,P=0~50,I=0~20,d=0,ctl=5,Sn=33,dIL=0, dih=50,op1=4,opl=0,oph=100,cf=2,addr=1 General control flow[4,5] In the double tank water level control, water first enters the first water tank, then outflows through the second water tank, compared with the first water tank, due to the increase of the water tank, the response controlled by the quantity is backward one step in time, so namely the volume delays, resulting in being difficult to control the process. Double tank water level control is an effective method to improve the dynamic performance of the regulation process. For the control action of the advance, it can greatly overcome the system volume delay.

3 Advanced Materials Research Vols Instructions for the hardware design[6]: Power on the total power and related instruments. After power on, restart your computer, run the MCGS configuration software, into the experimental system. After restarting the computer, four MCGS shortcut icon will appear on the desktop, MCGS environment, MCGS configuration environment, MCGS network configuration environment, online version of MCGS running environment, click the online version of MCGS running environment, into the monitoring system of the control design. Set the regulator for manual operation. First the regulator is arranged on the manual state, according to the regulator of the add / drop, changing its output value, the level of water in a balanced position. Manual output process add / drop regulator, to make the liquid level tank started by the original balance state to begin to change. After a period of time, the level of H2 into a new equilibrium state. Commissioning of instrument process control system[7] According to the design principle of liquid level cascade control system and the controlled process, the main and auxiliary controlled process time constant ratio is about 4.5:1. The working frequency of main and auxiliary circuit and operation of negligible is omitted. So the vice governor in single loop system tuning methods, the vice loop can be as a part of the main loop. By the tuning method of single loop control system, the parameter of tuning the main regulator is setting, instead of considering the effect on the vice loop by the change of the main regulator parameters. The results of the main and auxiliary controller parameters are as the following: the main controller proportional coefficient P=30, integral time I=15, differential time D=0; deputy controller proportional coefficient P=40. The given value of the instrument control system setting tank level is 15 cm, waiting until the system is stable, the step disturbance is decelerated immediately and at this time set the water level for 12 cm from the given value, the output response curve of the water level will be got. Knot theory The monitoring instrument in instrument system is for reaction control mode, when the input increases, the output tends to reduce. Then the parameters are adjusted according to the characteristics of PID control, and then achieve a satisfactory state in the system. By increasing the ratio to overcome the disturbance, the greater the proportional band is, the smaller the magnification times is, the weaker the control ability is, but still there is residual error in the proportional control, so the introduction of integral control is taken in, due to the integral action is a little strong in the system, resulting in slower recovery after rising curve, then by adding the differential effect to reduce the residual error, response speed system get acceleration. Acknowledgements This study was supported by Heilongjiang Provincial Department of Education Science and Technology Research Project( ).

4 2562 Advances in Manufacturing Science and Engineering V References [1] Zhihong Gao. Process Control and instrument and meter automation [M]. Hangzhou: Zhejiang University press, 2006(In chinese) [2] Xinjian Fu. Computer Control System of Process [M]. Xi'an: Northwestern Polytechnical University Press, 1995(In chinese) [3] Yuming Li. Chemical Instrument and Automation [M]. Beijing: Chemical Industry Press, 2004(In chinese) [4] K. J. Astorm, T.Hagglund.Automatic Tuning of PID Controllers. Instrument Society Publisher B. V, 1991 [5] Qinqin Wu. Control Instrument and Device [M]. Beijing: Chemical Industry Press, 2002(In chinese) [6] Yuhua Ling. System Design Principle and Application of Single Chip Microcomputer [M]. Changsha: Central South University press, 2006(In chinese) [7] Huairen Jie, Binyan Yang. Selection Handbook of Petrochemical Instrument Control System [M]. Beijing: Sinopec publishing, 2004(In chinese)

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