Research And Design Of Weighing System For Concrete Mixing Plant

As China’s infrastructure construction continues to improve and urbanization progresses,the demand for commercial concrete in society is steadily rising.As the main facility for producing concrete nowadays,upgrading concrete mixing plant to ensure concrete production quality and production efficiency is the right thing to do to keep the concrete production industry developing.As the core module of concrete mixing plant,the performance of weighing system directly determines the production level of the plant.The design and development of a weighing system with stable control,high weighing accuracy and high automation level is of great significance to improve the production capacity of concrete mixing plant and guarantee the quality of concrete.This thesis starts from the study of the batching accuracy of the weighing system.After understanding the production process of concrete,it aims to improve the accuracy of powder batching and the control accuracy and stability of the weighing system.After the main research object is determined,the weighing equipment and powder conveying equipment are studied and analyzed,and the calculation formula of screw conveyor conveying capacity is determined.Subsequently,this thesis researches the problems affecting the accuracy of powder batching weighing,and takes the problem of weighing error caused by the air residue in the process of batching weighing as the research direction.According to the research objective and research direction,this thesis analyzes the powder dropping process,establishes the corresponding mathematical model,and gets the calculation method of the air residue during powder dropping.The overall control structure of the weighing system was designed in order to achieve the objective of the study,and the overall control structure of "dosage controller + upper computer control software" was determined.Based on the overall control structure and the actual production situation of the concrete mixing plant,the functional design of the batching controller was carried out with the objective of improving the control capability and control stability.According to the functional requirements,the hardware selection of the weighing system is carried out and the overall circuit design of the system is completed.According to the previous design content,through the study of different concrete mixing plant requirements for the weighing system,a modular combination type batching controller structure is designed,which can be modularly combined according to the actual production requirements of concrete mixing plant,improving the applicability and economy of the lower unit batching controller of the weighing system.After finishing the overall control structure design and system hardware circuit design of the weighing system,in order to improve the control stability and accuracy of the weighing system,the control scheme of the dosage weighing process is optimized by combining the actual production process and production environment.The optimized control scheme divides the dosage process into two stages: coarse dosage process and fine dosage process.In the control optimization scheme,the coarse dosage process adopts fuzzy PID control,and the fine dosage process adopts PID type iterative learning control,through the study of control scheme and algorithm,the control scheme is implemented by combining the actual process of dosage weighing.Using MATLAB simulation and analysis software,the two control schemes are simulated separately to verify the feasibility and superiority of the optimized control scheme.After completing the hardware design and circuit design of the weighing system,this thesis conducts a functional analysis of the weighing control system to achieve the control of the whole production process of the weighing system.Combining functional analysis,the upper computer control software is designed,and the control software interface is developed and designed using the USART HMI development software.The software function commissioning test is carried out to verify the feasibility of the control software.Finally,this thesis takes the weighing system as the research object and conducts the weighing system control function test through the instrumentation test bench.Firstly,the test plan is designed,and according to the test plan,the test method is selected for test verification.Through the verification results,it is proved that the designed control function of the weighing system can be realized normally and the weighing system has stability and reliability.