The Research Of Four Corners Leveling Control System For FRP Products Press

FRP products press is automation equipment which utilizes hydraulic molding process (SMC/BMC) to produce composite products, such as DMC, SMC, BMC, GMT, LFT-D series FRP fiber reinforced plastic. This kind of hydraulic press contain two main features. First of all, the maximum velocity of slider can reach800mm/s, which is much faster than the ordinary ones. Besides, during the stage of pressing process, the maximum controllable velocity can also be up to40mm/s. Second, in order to improve the processing accuracy, it is much more critical to guarantee the parallelism of slider which must remain within±0.1mm. Considering the above two characteristics of such press, we utilize passive four corners leveling control system to achieve those goals. There are four single rod cylinders that are fixed to the four corners of the lower beam in this leveling control system. What is more, these cylinders do not have any fixed connection with the slider. When the slider enters the stroke of leveling trip (the entire stroke of leveling is80mm), the passive four corners leveling control system starts to work, adjusting the parallelism of slider in real-time.The advantages of using this system are as follows:First, there is not any fixed connection between leveling cylinder and slider, so it is not necessary to worry about the hydraulic stiffness and the stuck problem of leveling cylinder during the rapid downward period of slider. The whole system can reduce the supply of oil and save energy greatly at the same time. Secondly, the passive four corners leveling control system, including the hydraulic and electrical control system, is an optional module throughout press system, which means whether the hydraulic press should include this function or not depends on the actual process requirement. In the meantime, there come the problems that the entire stroke of leveling trip is only80mm, the maximum controllable speed of the slider is40mm/s and the whole table level accuracy should be remained within±0.1mm, so the control method and strategy will be the key point in the paper and carried out with extensive theoretical analysis and simulation. The main contents are as follows:In chapter one, on the basis of referring to a large number of domestic and international associated literatures about FRP products press and corners leveling control system, the characteristics and applications of FRP products, the key technologies of four corners leveling control system for the press and the strategy and algorithm of the leveling control system were summarized. Besides, the related research background and significance of this subject was expounded and the main research work was proposed.In chapter two, a detail analysis of the processes and function of every molding process stage was introduced and the curves of slider position-time and speed-slider position were designed. Besides, combined with the layout of the four corners leveling system, this chapter described the three main functions of this system: pre-acceleration, leveling control, and the process of micro-mold control.In chapter three, according to the main technical parameters of the FRP products press, the whole Electro-hydraulic control system was designed, including hydraulic systems and electronic control systems. Meantime, the overall architecture design of the four corners leveling electro-hydraulic control system was completed.In chapter four, the mathematical model of asymmetrical hydraulic cylinder controlled by servo-valve was established. Then the dynamic characteristic of asymmetric cylinder moved back and forth controlled by symmetric valve was analyzed. Based on that, the mathematical model of the overall model slider movement was also established, getting the state differential equations of the slider movement. In order to simplify and elaborate the complex motion of the slider, the state differential equations can be decomposed into two relatively simple subsystems according to the priority of the subsystem.In chapter five, the co-simulation based on Matlab/AMESim of passive four corners leveling control system was analyzed. The simulation controller was designed, which based on the control strategy of master-slave principle and mean principle. Besides, the whole system was simulated to validate the control strategy.In chapter six, experimental studies of the passive four corners leveling control system were carried out, the test bench and test scheme were introduced, and the control strategy of the system was validated.In chapter seven, the major work of the study was summarized. The conclusions, innovations and insignificance of the study were elaborated and the future study of passive four corners leveling control system was also prospected.