Investigation Into Electrohydraulic Control Systems For Shield Tunneling Machine And Simulated Experiment Method

Shield tunneling machine (STM) performs excavation, discharge, erection and other procedures inside a steel cylindrical shield to achieve automation and factorization of tunnel construction. Nowadays, there is a great demand for STM in China for modernization of infrastructure construction. The key technologies of STM include cutters and cutterhead. electrohydraulic power transmission, measurement, control and others. Electrohydraulic systems undertake the tasks of thrusting and excavation, and their performance directly affects safety and energy efficiency. STM goes through unexpected geological strata, so it is difficult to describe its external load and operating process using theoretical model, thus system design and technology development must be carried out by simulated experiment. Therefore, development of test rigs and study of electrohydraulic control systems for thrust and cutterhead through experiments are very significant to support technically to equipment manufacturing industry in China.In the thesis, the force and torque calculation models for the thrust and cutterhead drive systems were proposed. Compared with the empirical formula, many influential factors such as soil properties, penetration, opening ratio and earth pressure have been taken into account in the models. The relationship between thrust force and cutterhead torque was presented and the interactions of the parameters such as thrust force and speed, cutterhead torque and speed were revealed. It was shown in the experimental results for typical types of soils that the calculated and measured loads match closely under uniform geological conditions with a tolerance less than 3%. The models can be used for calculation and prediction of the loads of the thrust and cutterhead drive systems. An energy-saving cutterhead drive system with variable speed hydrostatic control was proposed. Power transmission efficiency of the cutterhead drive system was greatly improved and energy loss resulting from the system normal operating conditions under low speed was reduced. It has been shown in the experimental results that the energy efficiency of the proposed system is increased, irrespective of the geological conditions of clay, sandy and gravel soils. Within the operating speed range from 0.5r/min to 1.25r/min. the energy consumption of the new cutterhead drive system was reduced by nearly 50%. The compliance of a thrust hydraulic system and related values were proposed, by which the compliance of existing systems can be evaluated quantitively. A system design platform based upon compliance was established and a new system for 06.3m STM was designed. It was verified that its compliance is much better than that of existing machines, decreasing a peak load to original 69%. The design method will be helpful to improve reliability and to reduce failure rate of STM. The test rigs for tunneling and electrohydraulic control systems were developed, featuring multifunction, integration, various simulated geological conditions and small boundary effect. Combining physical simulation with semi-physical simulation, the test rigs make up the shortcomings of the previous ones noted for small scale and single function, and provide a good platform for experimental study on electrohydraulic control systems of STM.The major contents are summarized as follows:In chapter 1. the working principle, domestic and overseas development process of shield tunneling machine and its key technologies were introduced. The current research progresses on thrust, cutter head, segment erection control systems and shield simulation test rig were reviewed. The background and content of research subject were presented.In chapter 2, a comprehensive simulation test rig was developed, including a soil box of steel structure with a distributed loading system to simulate the vast majority of geological conditions. aΦ3m shield, an electric control system with 1500 interfaces and points, and a data acquisition system based on real-time database platform. The drive systems were designed in detail.In chapter 3, the thrust force calculation model was proposed. A comparative study of the thrust hydraulic systems with the combination of proportional relief and flow control valves, and proportional reducing valve were compared in terms of the characteristics of pressure and speed control, multi-cylinder synchronous control.In chapter 4. the cutterhead torque calculation model was established and the relationship between operating parameters were analyzed. Comparisons of drive efficiency between the hydraulic systems with variable speed and variable displacement were carried out. The efficiency improvement of the variable speed hydraulic system applied in cutterhead drive was analyzed, studying the cases in clay, sand and gravel soil.In chapter 5, the segment assembly kinematics and dynamics were modelsed. The segment pose error was derived by the perturbation method. The segment speed and position control strategies for assembling actuators were put forward, and a way to optimize the segment assembling route and hereby save energy was proposed.In chapter 6, the compliance of a hydraulic system was defined. The thrust hydraulic systems of four foreign shield machines were evaluated from the perspective of compliance. The design procedures of a compliance based thrust hydraulic system were put forward, considering fluid bulk modulus, structural parameters of pressure valves and other influential factors.In chapter 7. the research work and achievements were concluded, moreover, suggestions and directions for further in-depth study on the subject were provided.