Research On Key Technologies For The Electro-Hydraulic Control System Of Diaphragm Wall Trench Cutter

The development of the diaphragm walling technique has changed civil engineering significantly and become a construction technique of great worth for its superior property.The trench cutter(TC)is now the most advanced construction machinery used for diaphragm walling,and it is developed to construct the diaphragm walls in deep space under hard geological conditions.In the construction of diaphragm walls,the range of cutting depth is extremely large and the geographical conditions vary widely.All these harsh construction conditions present great challenges for electro-hydraulic control system design of TC.However,the research on TC in our country is still at a preliminary stage and its electro-hydraulic control system with high precision and fast response is lagging behind other monopoly developed countries which regard TC as technical confidentiality.This thesis focused on the special requirements on the electro-hydraulic control system of TC proposed by diaphragm walling construction,through the method of principle design,theoretical modeling,simulation analysis and experimental validation.The main contents of the study are as follows:In chapter 1,the operating principle and the general development history and current situation of diaphragm wall and TC were introduced.The related technologies for the cutter feeding system(CFS)and cutting system were stated.On this basis,the particular characteristics of the electro-hydraulic control system for TC were pointed out,and the necessity and innovation of this topic research were analyzed.The hydraulic principles of CFS,the feeding pressure control algorithms,pressure compensating of the cutting system,and the rotational velocity control of pump controlled cutting system were reviewed.Then the main research constents were proposed.In chapter 2,a cutter feeding electro-hydraulic control system based on servo valve controlled hydraulic motor was designsed in order to satisfy the performance and operating requirements of TC.The simplified mathematical model of CFS was established.The feeding pressure control of CFS is subjected to the unknown load characteristics of rock or soil,in addition,the geological condition is time-varying.Due to the complex load characteristics of rock or soil,the feeding velocity is related to geological conditions,cutting velocity,et al.What's worse,its dynamic model is unknown.To deal with the particular characteristics of CFS,fuzzy control was introduced into this multiple disturbance system and a novel adaptive fuzzy integral sliding mode control(AFISMC)algorithm was proposed specially for TC.In addition,AFISMC was successfully applied to the feeding pressure control system in accordance with the pressure dynamics of CFS.Finally,the performance of AFISMC was validated on the MATLAB/Simulink-AMESim co-simulation platform.In chapter 3,the feeding pressure control experiments were conducted on a hydraulic simulated test bench with the AFISMC and PI controller under different operating conditions.The hydraulic components used in the test bench were the same as the practical CFS to ensure the facticity and value of the experiments.The quantitative comparison of the feeding pressure tracking errors were obtained,and the experimental results demonstrated that the proposed AFISMC feeding pressure controller for CFS gived a superior and robust pressure tracking performance.In chapter 4,a novel pressure compensator based on air damping component for the transmission system of TC cutter in the deep mud environment was designed.The severe vibration of the cutter during the working process and the mud pressure oscillation due to the small internal cavity volume made the air damping component essential to the pressure compensator.The working principle and detailed structure of the pressure compensator was stated,and the static and dynamic mathematical models were established.The pressure dynamics were analyzed thoroughly and simplified by linearization techniques,and the major structural parameters were optimized.The simulation results demonstrated that the air damping component was effective against the pressure oscillation,and the impacts of design parameters on the compensator performance were analyzed.In chapter 5,the remote cutting velocity control of the cutting system was realized by an open-loop pump controlled motor hydraulic system.Due to the complex force conditions and the unknown load characteristics existing in the cutting velocity control system,the AFISMC algorithm designed specially for TC was used for cutting velocity control of the cutting system.The AFISMC cutting velocity controller combined the robust characteristics of an integral sliding mode controller and the adaptive adjusting characteristics of an adaptive fuzzy controller.A self-tuning fuzzy system through an adaptive mechanism was designed to approximate the unknown dynamics of the controlled plant.In addition,an integral sliding mode controller was used to compensate for approximation error of the adaptive fuzzy system.The AFISMC cutting velocity controller was synthesized using the backstepping technique,and the adaptive laws were chosen to adjust the fuzzy output and the switching gain of the sliding mode controller on-line.The stability of the whole system including the fuzzy inference system,integral sliding mode controller and the cutting system is proven using Lyapunov theory.Finally,the performance of the designed controller was validated through the simulation analysis and experimental contrast.In chapter 6,a novel electro-hydraulic cutting system of TC based on a pump controlled variable displacement motor system was proposed to solve the problem that the large volume in the long hydraulic pipelines between the power source and actuators of TC would severely affect the dynamic performance of the cutting system.The cutting velocity and the supply pressure of the cutting system were controlled by changing the pump and the motor displacement simultaneously.A MIMO nonlinear controller based on disturbance observer was designed to realize the simultaneous control of cutting velocity and supply pressure.First,a disturbance observer was proposed to estimate the disturbances acting on the actuator.Based on the estimation,a nonlinear controller was then designed to track the desired cutting velocity and supply pressure with a feedforward controller and a feedback controller which was implemented to stabilize the system.In addition,sliding mode control was used to compensate for disturbance estimation error.The stability of the whole system is proved using Lyapunov theory.Finally,the effectiveness of the proposed controller is verified through simulation results.In chapter 7,the major research work of the study was summarized.The conclusions and innovations of the study were elaborated and suggestions for further study on the subject were presented.