Research On Dynamic Modeling And Sliding Mode Control Methods Of Casting Overhead Crane

The casting overhead crane is an extremely important lifting and handling equipment in the metallurgical industry.Its main task is to quickly and accurately move the payload to the specified position,and avoid the swing of the payload as far as possible in the transportation process.In addition,the casting overhead crane often transports liquids,so the payload also needs to suppress the shaking of the liquid in the container during transportation.However,due to the underactuated characteristics of the casting overhead crane,people can only control the motion of the trolley to indirectly control the swing of the payload and the liquid in the container,so it is very difficult to achieve the triple control objectives of fast positioning,payload anti-sway and liquid anti-sloshing.Therefore,based on the previous research,this thesis mainly focuses on the dynamic model and sliding mode control method of casting overhead crane.The main work is as follows:(1)Dynamic model of casting overhead crane.In this thesis,two dynamic models of casting overhead crane are established based on analytical mechanics method.First,the payload is equivalent to an ideal center of mass,and Lagrange equation is used to establish the three-dimensional single pendulum dynamics model of the common casting crane.The second is to analyze the sloshing characteristics of the liquid in ladle,and establish an equivalent model of n-order mass spring of casting overhead crane based on liquid-solid coupling motion by using linear potential flow theory and equivalent mechanics theory.Finally,the accuracy of the dynamic model is verified on the experimental platform.(2)A sliding mode control method based on smooth start of casting overhead crane.To solve the problem that the payload and the liquid in the container are easy to shake violently due to inertia when casting overhead crane is started,an adaptive time-varying sliding mode controller with smooth start is proposed.Firstly,an integral time-varying sliding mode surface is designed in this thesis,which makes the control force of sliding mode controller rise steadily from zero and has global robustness.Then,an adaptive mechanism which can adjust the coupling characteristics of multiple parameters online is constructed to solve the problem that the traditional control method is sensitive to the parameters of the casting crane.Finally,simulation and experimental results show that the proposed method has excellent performance in anti-swing positioning,smooth startup and system parameter self-adaptation.(3)A sliding mode control method for casting overhead crane based on liquid-solid coupling motion.Aiming at the problems of weak robustness and obvious shaking due to insufficient utilization of state coupling characteristics in existing sliding mode control methods,a global proportional differential sliding mode controller with enhanced coupling is proposed based on the equivalent model of n-order mass spring of casting bridge crane system.Firstly,a time-varying sliding mode surface with enhanced coupling is designed to improve the transient performance of the control system.Then a new switching function which can adjust the switching speed is used to replace the symbol function in the traditional sliding mode control law,which can effectively eliminate the system shaking phenomenon.Finally,simulation results demonstrate the effectiveness of the proposed method and its robustness to uncertain perturbations.