Study On The Modeling And Strategy Of Elongation Control System For A Tension Leveler Of Cold Rolling

Tension Levelers (shortly, TL) are widely and popularly employed in the continuous treating of cold strip lines. Under the combination of tension and bending, the band metallic material takes place deformation for the purpose the treatment. TL is necessary to improve the surface pickling quality and to get the perfect product waviness in the pickling line, that is TL are arranged in the entry section of pickling line to loose the surface layer and to remove the oxide scrap and other particles and to improve the waviness of the treated strip before rolling. While in CGL, TL is also the key equipment to obtain the perfect waviness, eliminate the edge faults, improve the metal isotropy, banish the long yield line, and stop the form of metallic slide.The object of this paper mainly concerns T&B Levelers, equipped at respectively the Pickling and Tandem Cold Mill Unite Line (shortly, PL-TCM) and Continuous hot-deep Galvanizing Line (also shortly, CGL) of the Cold Milling Plant in one Anhui Iron & Steel Company. Firstly, the equipment constitutes, function and employing properties of TL are set forth, from the view of theoretic analysis and jobsite experiences, the detailed check and analysis of the actual problems occurred in the above two levelers are given. And meanwhile, via the detailed analysis of the actual problems, the leveling principles and the real reasons that cause the problems are yielded. Secondly, via the combined analysis of the mechanical and electrical system, and the match relations of torque output of differential gear and velocity are found. Finally, some velocity formula and torque control of CGL's TL are inferred and validating the actual adjustment.The root reason of the appearance of serious "vibrating grain" in the CGL product is the tension fluctuation of the strip and manifests the friction slide between the strip and roll. Three key factors are clear via the theoretical analysis and actual experiments:the tension fluctuation of the entry and exit strip of TL, the diameter and surface condition of the tension rolls and the set-points of the torque motors. And the main reasons that cause the short service life of working rolls and serious wear of tension rolls in the PL-TCM are the unreasonable distribution of torques of rolls and the unbalance of loads. The differential gear of the driving chain inside TL belongs to the group of two freedom organization. View from the driving modes, torque match and compensation are very essential to the concentrating drives. That says the torques should be distributed and compensated in the driving system of tension leveler which employs the form of the concentrating drives. So, the paper, from the opinion of dynamics, establishes the motive differential equation via selecting the available coordinates and adapting the Lagrange equation, and further analyses the torque transmitting regulation of differential wheels in the driving system. So, the basic preconditions for the steady operation of tension leveler are clear. And also, some actual explanations are given under the different operating modes of differential match.The driving system of the two TLs is an open control loop in the production. The goal which set the TL in the line is gain the exact elongation, the two TLs obviously fall short is that it is effected by the TL parts easily and it cause the control system instability and imprecise. So the opening loop control system can't content the process requirement. Based on the above the analysis and the velocity and torque distribution formula of two freedom mixed driving machinery, new control conceive are presented, that is, the direct closed loop of elongation control and closed loop of torque distribution of all tension rolls. And by the help of the computer emulation, the new conceive are put on the PL-TCM's TL, and proved that the new control concept is available. In order to develop the advantages of TL and avoid the appearance of all kinds of problems, this paper is helpful to deepen the reorganization of TL, and also supply the theoretical foundation of possible modification and the introduction of TL.