Research On Control Method Of Hydraulic Servo System For MDF Continuous Hot Press Based On Fractional Order Sliding Mode

Compared with natural board,medium density fiberboard(MDF)has more uniform structure,less expansion and shrinkage,and is easy to process.At the same time,its excellent mechanical properties and extremely low production cost make it quickly become the favorite of wood-based panel market.In the hot pressing process,the control of the fixed thickness section of MDF slab is a key step to improve the whole production quality.A very important problem is how to ensure that the hydraulic servo system of continuous hot press can achieve stable and accurate position tracking in a short time.The reason why there is a certain degree of difficulty and computational complexity in the design of controller is that the system has the problems of internal parameter uncertainty,internal and external disturbance and control input saturation.In view of the above problems,this paper takes the fractional order sliding mode as the main control algorithm,and uses the adaptive neural network,nonlinear disturbance observer and active disturbance rejection control algorithm.In order to effectively improve the control performance of the system and ensure the accurate thickness of the slab,it is necessary to further study the tracking control problem of the hydraulic servo system of the continuous hot press.The work of this paper is arranged as follows(1)In view of the uncertain parameters and internal and external force disturbance in the hydraulic servo system of MDF continuous hot press,a fractional order integral sliding mode control scheme based on adaptive RBF neural network is proposed.The neural network is used to approach the compound disturbance of the system,and the fractional integral sliding mode controller is designed by using the advantages of fractional order,so that the system can accurately track the position and effectively ensure the stability of the system.In addition,the MATLAB simulation platform can verify the feasibility of the control strategy.(2)Aiming at the input saturation problem of MDF continuous hot press hydraulic servo system in actual production,a fractional order compound integral sliding mode control strategy based on nonlinear disturbance observer is proposed.Firstly,the hyperbolic tangent function is applied.Secondly,the oversaturated part of the system is incorporated into the new compound disturbance,and the nonlinear disturbance observer is used to observe it;A new fractional order compound integral sliding mode controller is designed to compensate the observed results.At the same time,the tracking convergence is accelerated.Finally,the simulation results show that the designed controller has effective control performance.(3)Aiming at some unmeasurable states and unknown modeling problems of MDF continuous hot press hydraulic servo system,and in order to effectively improve the transient performance of the system,a fractional order global fast terminal sliding mode controller based on auto disturbance rejection control(ADRC)strategy is proposed.Firstly,an extended state observer is used to observe and estimate the uncertain compound disturbances.At the same time,in order to improve the convergence rate of the system,a fractional global fast terminal sliding mode controller is designed.Secondly,according to the characteristic that ADRC does not depend on mathematical model,tracking differentiator is introduced to ensure the stability of the system.Finally,the feasibility of the controller design is proved by the modules in the simulation platform.In conclusion,in order to effectively solve the problems of parameter uncertainty,internal and external load disturbance and control input saturation of MDF continuous hot press hydraulic servo system,the corresponding controller is designed based on fractional order sliding mode control algorithm,which fully considers the dynamic performance of the system,improves the robustness of the system and ensures the accurate position tracking of the system,It has certain theoretical research significance and practical engineering value.