| Low relaxation pre-stressed strand is widely used in highway,railroad,long-span bridges,hydroelectric dams and other infrastructure areas because of its good elongation,high tensile strength,low relaxation rate,good fatigue resistance,the steel soft,medium-section and strong binding power.Especially in recent years,low relaxation pre-stressed strand is generally used in many fields,and its domestic industry has also flourished.Nevertheless,how to further improve the strand production technology in order to improve product quality,optimize production line systems,reduce energy consumption and improve production efficiency is still worth studying.The thesis introduces the production process and all procedures of its technological process of low-relaxation pre-stressed strand,whereby it designs the control part,driving part,and feedback part of the production line respectively,and analyzes the coordination and the control principle among all major electric motors,and then figures out the preliminary electrical control scheme.In terms of the steel strand stabilization process,the thesis studies the control strategies without using tension sensors.It first analyses and calculates the equivalent elastic modulus under variable temperature states between the double tension wheels structure.According to the results as well as the experimental data,it calculates the desired speed of the second electric motor,and transforms the tension control into the electric motor speed control with the aid of the Hooke law,and then designs the fuzzy control strategies of the two sheets of speed control.In addition,it also designs the control strategies of other winding tensions in the production line.The thesis takes the actual production line as an example by making the hardware selection,the PLC programming,the HMI design and then putting the control system into actual production line on the basis of the electrical control scheme,and eventually accomplishes commissioning induction heating device and the entire production line running.It also analyzes the tension value,the tension wheel speed and other data in production trials so as to demonstrate a certain degree of practicality in the analysis and calculation of the equivalent elastic modulus,and a certain degree of improvement in the accuracy and stability of the system control strategies.After its installation and commissioning,the control system has been put into running a domestic enterprise.It has been testified that the system can achieve the stability and reliability,and meet requirements of the product performance indicators. |
