Production Management Control System Of Concrete Mixing Plant

The concrete mixing plant is the typical product of Electromechanical unifinication .it is the whole set of equipment which measures the stocks such as aggregate,cement,fly`ash, water and additive according to concrete prescription and produces qualified concrete . Through the system research to the production management control system of the mixing plant,it has the vital significance to the development of the production management control system , at the same time to the similar control system,like the stabilizer soil ingredient control system and so on the similar system,it also has the vital significance. The concrete mixing plant is compose of the stock storage, the stock ships, the measurement system,the mixing system and the control system . The measurement system and the control system are the key of the concrete quality control. The key of control system lies in the accuracy of weighing, the precision of the aggregate is most difficult to control. Through carring on the analysis to the controlled member,we establish the physical model of aggregate weighing system ,take the weighing hopper as a two steps springs damped oscillation system to carry on the discussion .The control system has the following characteristic: (1) The controlled process is irreversible, therefore the output result cannot be adjusted immediately through be over performs . (2)The controlled process has the random characteristic,because the property of the massive material flow and the current capacity are unsteady . (3)Because the control is discontinuous, the controlled process is unable to adjust the delivery rate by the process control. (4)The fine weighing is main,the gross weighing only saves the weighing time. According to this kind of characteristic,with the pure time delay mathematical model as the foundation,we carry on the estimate and the computation to the dropping variance,and realize the automatic correction to the dropping variance. The working conditions of mixing plant is bad .the mixing plant has many large power motors , In order to guarantee the Anti-interference ability of the control system , the control system uses the industry control computer which is produced by the Advantech Technologies Co.,LTD,and the PD650D weighing indicator which is produced by ChiMei Co.,LTD. The industry computer uses the ISA standard,and has the facilitates to carry on the internal module expansion.Along with the development of the industry computer, its stability is more and more high, we can effectively save the development cycle. The revises to control mode is merely the software revision, so the control flexibility has been enhanced .The digital input and output card has isolated function, and has effectively isolated influence to the computer system which comes from the undulation of the electrical network voltage and the electric current . In order to achieve the enough measuring accuracy, we must use the computer real_time control system to carry on the measurement control and the sequential control. The real_ time computer system makes the response to the external event in the definition time internal , This is the key characteristics that the real_time contrll system distinguishes the common computer system . The control software is compose of weighing module , data communication, data inquiry and so on ,the Delphi7 is choosen as the developing tool, the Delphi7 is a visual integration development kit,delivery from the company of Borland ,based on the Pascal language. the Delphi7 can be used to develop each kind of software of Windows9.x and NT etc.quickly and efficiently .the project is compose of the main control platform , registers module, public variable, public database connection object, channel establishment and inspection and data inquiry module. The PD650D weighing indicator is multipurpose ,as a part of the weighing system ,it transforms the signal comed from various weighting sensor for the weight value , the weight value is transmited to the industry computer. The communication is achieved with Mscomm module beteween the weighing indicator and the industry computer, each serial port is corresponding in one individual module.the module is to respond and get the data in buffering area when incident occurs mainly. The digital input and output card is used to expand the computer's performance .the Dynamic Link Library, given by the manufacter ,is used to control the input and ouput of card .The database uses the Access database, through the establishment public database connection object, other modules acheive the connection to the database, the controlled process visits the database through ADO(Active Data Objects), according to the system function design request as well as the function module division ,the thesis has listed the data item and the construction of data . The weighting ,unloading , transporting ,mixing of various materials is to be acheived with the Delphi's Timer module ,the real_time control is achieved to guarantee the weighing precision. While mixer unloading , The formula data and the customer data are saved into historical data sheet HistData , According to the input time interval, the data inquiry module inquiries history data ,and print the preview historical data . To lead and backup the database can also acheived. The main surface menu mainly includes the control mode, the manual input, the system maintenance, the historical data, the help and so on, the tool fence including the channel establishment, starts,stop, choice formula, historical inquiry and so on. The main surface simulate the production process , on the identical screen , the formula value, the actual value ,the gross weight and the material name may be seen . The control procedure adopts the multi_task control way, while weighing , may choose the next task.the on_line revision can be achieved to all parameters ,the formula and mixing time .The aggregate scale unloading and the middle bin unloading can be forbidden . Thus facilitates the system the man_machine interactive as far as possible .while a wrong occurs ,the system could eject an exception , Exceptions are handled within try...except statements. After connecting PD650D weighing indicator,the communication module can correctly display the weighing valve, also can correctly process the overload and the communication wrong .According to assigned speed ,the weighing module change the weighing valve. According to assigned formula ,the technical process can be achieved .The input switch valve can be received ,The periphery load can be accurately carried on .The weighing precision can satisfy the technical specification , The data can correctly store the database, successfully has carried on the inquiry test to the historical data. It is important to maintain the software in the practice , and itis necessary to processing the problems effectively, which possibly ocurrs in the practice ,and it is a long_time work to enhance the stability of software .This system waits for improves, the maintainance, and further consummation in the practice .