Liu Yanwei, China Metallurgical Changtian International Engineering Co., Ltd., Changsha, Hunan 410007, China. Finally, the feasibility of this control method in energy saving was verified by an example.
In industrial production, compressed air is an important source of power. In scientific experiments, compressed air is also an important simulation condition, such as widely used pneumatic machinery, wind tunnel tests required for aircraft design. The principle of compressed air system and the system composition itself are not complicated, but in practice, there are problems such as unstable pressure and high energy consumption, and the control level is generally not high. Under the conditions of actual production and scientific research, it is a frontier topic in this field to study the energy conservation of air compression systems. Scholars at home and abroad have made many explorations on this issue. The results of practice and research show that the control of the air compression system largely determines the efficiency of the system. Intelligent control technology has also been gradually researched and applied in the energy saving of air compression systems. In this paper, we will focus on this issue, aiming at the energy saving of air compression systems, and explore the use of intelligent control methods to achieve energy savings in the system.
In terms of system composition, a compressed air system generally consists of a compressed air generation system, a consumption system, a cooling system, and a drying system. Among the above four basic subsystems, the compressed air consumption subsystem is the main link in energy consumption. In this subsystem, there are many control elements involved, and the working effect of these components has an important influence on the total energy consumption of the system.
Second, the compressed air system also has its own unique characteristics that require attention before the study. Although the pneumatic device of the compressed air system has a simple structure, high reliability and longevity, the action speed of the pneumatic component is closely related to the load change, and is directly affected. In addition, the stability of the cylinder at low speeds is reduced due to the influence of friction.
The control of the compressed air system is different from the common control system solution, which is mainly reflected in the following two aspects. First, the generation of compressed air has a certain hysteresis and is directly controlled by the intake valve. Under the premise of the compressor starting, compressed air will only be generated when the intake valve is opened, and when the AC asynchronous motor is running, the production of compressed air must be stopped only after the intake valve is closed. Therefore, there is a significant hysteresis in the control object of the compressed air system, which may be the most important problem in the control of compressed air systems.
3 Compressed air system fuzzy control scheme design In the compressed air control system, the main parameters considered are the main control signals of system gas pressure, temperature and flow, and the main control object is gas pressure. In this system, the quantity of interest in determining the state of the system is the pressure change in the compression system and the corresponding rate of change, and is primarily the start-stop state of the compressor when determining the system action. U1 represents the upper pressure limit, U2 represents the lower pressure limit, EU represents the pressure error, and EUC represents the rate of change of the pressure error.
The fuzzification of the input quantity and the output quantity is based on the fuzzy control requirement, and the input and output of the control system need to be fuzzified to make it into the amount of fuzzy operation. According to the habit of fuzzy control, the basic domain of the pressure difference of the compressed air system is taken as the change rate of the flow deviation. The corresponding fuzzy linguistic variables are negative, negative, negative, zero, positive, medium, and positive. The level code corresponding to the fuzzy linguistic variable is also taken as 1PB, PM, PS, U according to the fuzzy control habit. , NS, NM, then. The control output is expressed in U and there are only two states: "0" and "1", which correspond to "off" and "on" of the compressor.
In theory, the membership function can have a variety of choices, such as bell-shaped, trapezoidal, etc. In practical applications, the most simple triangle membership function is generally selected to calculate, and basically can meet the needs of operational precision. For the above pressure difference and pressure error rate of change, a triangular membership function is used, as shown in .
The EUC membership function can be seen from the previous analysis. The fuzzy control system uses a dual input-single output control mode, that is, the output is determined by the input of EU and EUC. The output in the compressed air control system corresponds to two states, that is, the switching state of the compressor. According to the usual practice, the "off" and "on" of the compressor are represented by "0" and "1". According to the usual IFAANDBTHENC reasoning form, and these control rules are based on the summary of the actual control experience. For example, when the pressure error is negative and the pressure error changes to negative, the compressor should be started. Write the following control rules: IFEU=NBANDEUONB THENU=l. By summarizing the above control experience, 49 fuzzy control rules can be obtained. Due to space limitation, only the first 14 control rules are listed: (1) IFEU=NMANDEUC=NBTHENU=1 Go to page ll3) 4 should establish a centralized and unified work information platform to achieve digital and information management. In accordance with the needs of land reserve management, the city has jointly researched and developed the land reserve management transaction information system with the Liaoning University of Engineering and Technology: Land Reserve Trading subsystem: responsible for the management of the formulation and implementation of the land reserve plan, including the management of the land reserve, and the annual land. Prepared plan management, annual temporary land reserve plan, annual land reserve implementation library, annual land reserve supply bank, acquisition of enterprise and institution acquisition, residential house and commercial network house collection, relocation progress fund allocation, land planning information management, enterprise file Information management: the pre-project subsystem of the land, responsible for the consolidation and pre-use of the land reserve, including the expenditure management of the land leveling and the reconstruction of the infrastructure such as electricity and heat supply: the cost measurement subsystem, responsible for the relocation entities The compensation fee review work includes concrete land review management, collection and compensation review work summary management, and proposed land parcel review management: land financing subsystem, which is responsible for project fund management, including loan fund borrowing funds, financial allocation, project funds, Lending money, repayment management, etc.: The transaction management subsystem is responsible for the transfer management of the land parcels, preparing for the listing of the land, and forming an annual trading library, including the annual transfer plan library management, annual transaction database management, and Listed land preparation table management.
Each subsystem module in the land reserve trading system is completed by the relevant staff to input (or import), modify, delete, query, etc., realize the flow of data between each module and complete the automatic calculation and total of all kinds of data. Such functions, intuitive management, and clear objectives play an important role in land acquisition and storage, and financial management of funds.
Land storage risk prevention analysis The land collection and storage in the land reserve plot risk, financing risk, expected benefit risk, industry coordination management risk, etc., the city's land collection and storage work from planning, cost auditing to specific implementation, from macro The management has clearly defined the work flow and the responsibilities of the various government departments. From the specific management, the cost audit, the cost package and the information management system have passed the practice test, and the practices and measures are appropriate and awkward. Work efficiency, effective prevention and reduction of land acquisition and storage risks.
In short, the land storage and storage work is a comprehensive work involving the functions of the government's various functional departments and the interests of the state, the collective, and the individual. The complexity requires that a reasonable storage and storage procedure, scientific measurement methods, and necessary audit and inspection systems must be established. . Doing a good job in risk prevention and risk estimation of land acquisition and storage projects plays an important role in regulating the land market and promoting urban construction and economic development.
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