| Due to external force, thermal stress or the organization stress of rolling orheat treatment, steel pipe will inevitably get bending. For the problem ofbending at pipe ends or large-diameter steel pipe, press straightening is commonsolution. The traditional method is that the workers often determine theparameters by experience taking into account client requirement for steel pipeovality so that press straightening has low precison and efficiency. Automaticpress straightening machine eased this situation, this paper establishesload-deflection mathematical and flattening model model of pressurestraightening for thick-walled steel pipe and controller for hydraulic system ofpressure straightening machine to provide a theoretical basis for thedevelopment of pressure straightening machine for thick-walled steel pipe.The main content of this paper are as follows:1) According to the elastic-plastic theory, considering the case ofcross-section plastic flattening, establish load-deflection mathematical model ofthe pressure straightening process of thick-walled steel pipe. Calculation ofstraightening stroke using this model overcomes the shortage of curvatureequation model. This model reflects straightening thick-walled steel pipedeformation mechanism.2) According to the elastic-plastic theory, establish mathematical model ofcross-section flattening through the analysis of middle cross-section.3) The hydraulic position servo system is the executive mechanism of thesystem.It directly determines the workpiece machining accuracy and machiningefficiency. This paper establishes of fuzzy PID controller of straighteningsystem using error e and error change ec to on-line adjust three parametersk p,k i, andk d. The complex structure of the system is a typical nonlineartime-varying system. Fuzzy PID controller improves accuracy and responsespeed.4) Revise the theoretical calculation model through test data and programthe pressure straightening parameters calculation software. |
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