Double Closed-loop Control Strategy Of Four-axis Leveling System For Composite Press

Composite material products which have good mechanical properties and light weight and high strength are widely applied to aerospace,submarines,automobiles and other high-tech fields.Composite material forming equipment is the key equipment for composite materials.With the high requirement of the molding precision of the composite material,the demand of the large tonnage and high precision composite molding equipment is becoming stronger and stronger.The key to the precision of the composite material is the precise control of the slider in the pressing process.Due to the bias load characteristics of the system,it cann't meet the requirements of composite material with high shape and complex shape under the pressure of thousands of tons.By installing the four-axis leveling system,the unbalanced load characteristics are balanced.But it is not clear about the bias load mechanism of the system and the parameters of the electro-hydraulic servo control system.Therefore,this article proposes a control strategy based on double closed loop,which is based on the passive four-axis leveling hydraulic system and the control characteristics are studied.First of all,the article analyzes the operation process of the composite hydraulic press and acquires the function of the four-axis leveling system.Based on the mechanism of the load and the static and dynamic parameters of the composite hydraulic press,the hydraulic and control system of the four-axis leveling hydraulic cylinder is designed.And a double closed loop control structure is constructed to realize the horizontal control of the movable beam,which is that the inner ring is a pressure ring and the outer ring is a multi cylinder synchronous position closed loop.Secondly,the mathematical model of servo proportional valve controlled asymmetric cylinder is established and its frequency response is analyzed.Then the influence of key parameters on the pressure control characteristics is studied.And based on the AMESim pressure closed loop simulation model,the theoretical analysis of the key parameters of the pressure control system is verified to be correct.Then,based on the closed-loop control characteristics of the pressure,the design idea of feedforward compensation and closed-loop feedback controller is proposed.Combined with the fuzzy PID controller and the parameter optimization of the genetic algorithm,the inner loop precise pressure closed-loop control is realized.Through the simulation of AMESim and MATLAB/Simulink module,compared with the traditional PID control,the superiority of the optimization algorithm in the control performance is obtained.At the same time,the semi-physical simulation platform based on xPC Target is designed to verify the simulation results.Finally,based on the state space equation of the slider,a sliding mode variable structure control algorithm is designed.Combined with.the four cylinder force distribution algorithm,the target leveling force of the four-cylinder is obtained in order to achieve high precision control of the slider.The effectiveness of the proposed algorithm is simulated by MATLAB/Simulink module.And the data acquisition system based on Lab VIEW is applied to provide data support for the adjustment of the composite hydraulic press and the four-axis leveling system.The validity of the proposed algorithm is verified by experiments.The innovation of this article is that Aiming at the characteristics of nonlinear,coupling and over driving of the passive four-axis leveling system,a new method based on double closed loop control strategy is designed to simplify the design of the controller.And the optimal control algorithm is applied to improve the response speed and robustness of the system.The theoretical modeling and numerical analysis are carried out to obtain the influence of the key parameters on the performance of the system.It is helpful to the optimization design and performance improvement of the leveling system.Finally,the effectiveness of the control strategy and algorithm is verified by experiments.