Research On Technologies For Thrust And Slurry Balance Of Large-diameter Slurry Shields

The slurry shield is now the preferred equipment for tunnel constructions across rivers.It combines excavation,support,slagging and other procedures together,which greatly improves the tunnel construction efficiency.With the growing demands in traffic,tunnel construction gradually turns to large depth and large diameter.As the preferred equipment to cross rivers and straits,large-diameter slurry shields will embrace a period of rapid development.However,the geological conditions are complicated,and the construction precision requirements are high,which makes the design of large-diameter slurry shields a great challenge.According to the characteristics and requirements of construction with large-diameter slurry shields,this thesis studied the thrust system and slurry balance system,through the method of principle design,mathematical modeling,theoretical derivation,simulation analysis and experimental validation.The main contents of the research are as follows:In chapter 1,the related research background and significance of slurry shields are introduced,including the characteristic,operating principle and development of domestic and overseas.The research status at home and abroad is summarized,including the electro-hydraulic principle and control of thrust systems,the electro-hydraulic control technology and the slurry balance technology.The shortcomings and limitations of existing research work are analyzed.Therefore,the main research contents of this thesis are proposed.In chapter 2,a parallel-control thrust system consisting a proportional variable displacement pump and a proportional servo valve is developed according to the characteristics of large-diameter slurry shields,which takes the dynamic performance,control accuracy,system heating and energy consumption into account.According to the nonlinear mathematical model of the pressure dynamics of the parallel-control thrust system,a parallel-control thrust system pressure controller based on the disturbance observer(DOPVPC)is designed to estimate and compensate the integrated model uncertainties and disturbance.According to the advantages of proportional variable displacement pumps and proportional servo valves,and the reliability in practice,a separate strategy is employed for the two control inputs.DOPVPC is designed based on backstepping method.The stability of the system is proved through Lyapunov theory.Simulation and experimental results show that the proposed DOPVPC can take advantage of the parallel thrust system,reduce the system energy consumption and heating,improve the response and accuracy of pressure control,and attenuate the model uncertainties and disturbance.In chapter 3,according to the nonlinear mathematical model of the velocity dynamics of the parallel-control thrust system,a parallel-control thrust system velocity controller(DDOPVVC)based on radial basis function neural network and extended disturbance observer(RBFNNEDO)is designed to confront the complicated and variable working conditions of large-diameter slurry shields in construction.RBFNNEDO can reconstruct the load force in the construction offline based on the geological prospecting and the previous construction data,and estimate the system’s uncertain parameters and disturbance online,which improves the velocity control accuracy.The velocity controller is designed based on backstepping method,in which the pressure control loop adopts the same disturbance observer in chapter 2.A similar separate strategy is employed for the two control inputs as chapter 2.Stability of the system is proved through Lyapunov theory.Simulation and experimental results show that the proposed DDOPVVC can take advantage of the parallel thrust system,improve the response and accuracy of velocity control,reduce the system energy consumption and heating,and attenuate the model uncertainties and disturbance.In chapter 4,based on DDOPVVC in chapter 3 and fuzzy impedance control,a thrust system pressure velocity composite control strategy(FIPVCC)is designed to meet the requirements of construction accuracy and safety in complicated and variable geological conditions.FIPVCC consists of DDOPVVC and fuzzy impedance control.DDOPVVC helps to achieve accurate velocity control,while fuzzy impedance control is responsible for coordinating pressure and velocity in thrust system.Parameters of impedance control are adjusted by fuzzy rules to achieve a better performance.The stability of the system is analyzed.Both simulation and experimental results show that the proposed FIPVCC can coordinate the pressure and velocity in thrust system.Accurate velocity tracking can be obtained when pressure is in the allowable range.And velocity command will be adjusted when the change of geological condition occurs,which makes the pressure lie close to the desired one to keep safe.The accurate velocity tracking can be achieved again,when geological condition recovers.In chapter 5,the basic principle of slurry balance system is analyzed.Based on the dynamic model of the air chamber,the system in the air chamber is simplified into a mass-spring-damping system,characteristics of which are analyzed.The response of the air chamber to the water pressure fluctuation of the excavation face under different initial slurry level and kerf pressure is analyzed by simulation,which helps to determine the initial slurry level.According to the mathematical model of slurry balance system,a MIMO controller based on dual disturbance observers(DDOC)is designed to estimate and compensate disturbance.The simulation results show that DDOC can obtain accurate and fast control of the slurry level and the kerf pressure,which is beneficial to maintain the stability of the excavation surface and improve the performance of the thrust system.In chapter 6,the main research work of the thesis is summarized.The research conclusions and innovations are elaborated,and suggestions and prospects for further research work on the subject are presented.