| Energy savings and emission reduction are a prerequisite for sustainable, economic and social development. Transportation is one of the high energy-consuming sectors. A well-established strategy to cut down on fuel consumption and carbon dioxide emissions is to reduce the weight of automobiles. Using the variable gauge sheet has become a key strategy in the production of lightweight vehicles. This thesis, supported by National Nature Science Foundation, will focus on the control strategies and mechanisms during the periodic longitudinal profile strip rolling process. The control system for periodic longitudinal profile strip rolling has been developed and applied to industrial production with excellent results.The main contents are as follows:(1) The control system for rolling periodic longitudinal profile strip has been designed and set up according to the demands of the process. Instrumentation has been allocated and designed to accommodate these requirements. The driving system of the mill has been specifically designed to take account of the cyclical variability characteristics of rolling torque and tension. Level1element automation system control scheme has been designed. HMI, PDA and level2process control systems have also been developed.(2) The control strategies for rolling periodic longitudinal profile strip has been set up. First, based on the strict length and position requirements of the periodic longitude profile strip rolling, we have derived a new rolling micro-track calculation model for the period variable gauge. The micro-tracking processes for gauge control of the compensation algorithm and the rolling of strip length tension elastic compensation algorithm have been derived. High precision micro-tracking strip rolling process in real-time has been performed. The horizontal coordinates are provided to control variations in the speed, gauge and tension. Secondly, horizontal rolling speed must match the speed of the hydraulic cylinder in AGC system, which limits the level of the strip rolling speed in the periodic longitudinal profile strip thickness transition area. To improve rolling efficiency, the periodic longitudinal profile strip variable speed control strategy has been investigated and an algorithm has been determined.(3) The thickness control strategy for rolling periodic longitudinal profile strip has been proposed. First, cycle variables for the roll gap curves in the periodic longitudinal profile strip rolling process were determined. Single-point settings and multi-point dynamic settings have been individually used to control the strip thickness and transition area. The mechanism of multi-point dynamic settings in the thickness transition zone has been extensively investigated. Set point coordinates, which are determined by using a linear constraint equation of the fixed-point division method, are used to define the setting roll gap to the goal as close as possible. Secondly, with the characteristics of cyclical changes for the strip roll gap, we designed the AGC control system of rolling periodic longitudinal profile strip. We also deduced a special feed forward AGC model, a monitor AGC model and a gauge meter AGC model for rolling the periodic longitudinal profile strip.(4) The periodic longitudinal profile strip rolling tension control strategies have been investigated. First, a composite tension control system, combining direct and indirect tension control strategies, has been designed to facilitate fast response ability during variable gauge rolling as well as rapid stabilization during simple rolling. Secondly, a tension model for rolling periodic longitudinal profile strip has been derived. By using the method of querying parameters table, rolling period-variable tension curves have been obtained. Furthermore, during the tension control process, a driving torque model and uncoiled, coiler and main driving velocity matching model have been derived.(5) It provides a way to evaluate a variety of control strategies for the process, by collecting and analyzing PDA curves of rolling periodic longitudinal profile strip on a four high cold mill.In this thesis, the key control technologies of periodic longitudinal profile strip rolling have been shown to be highly practical, successful and stable. The developed control system has been applied to industrial production lines. The above research work provides a firm base for the lightweight of automobiles. |
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