Research On Key Technologies For Electro- Hydraulic Thrust System Of Steep Gradient Tunnel Boring Machine

Full face tunnel boring machine (TBM) is a tunneling machine dedicated to tunnel construction, it can perform excavation, lining, slaging and other procedures for automated tunnel construction. Nowadays, the techniques used in the TBM for ordinary planar tunnel construction are already mature, however, in the construction of steep gradient tunnels, the range of tunneling depth is comparatively larger and the geographical conditions vary much more widely, all these harsh construction conditions pose great challenges for the TBM, and the ordinary planer TBM can not be used any more. This thesis focused on the special requirements on the thrust system of steep gradient tunnel boring machine (SGTBM) proposed by steep gradient tunnel costruction, through the method of 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 situation of TBM in domestic and overseas were introduced. The electro-hydraulic control system of TBM, attitude control algorithm, and special requiremnets proposed by steep gradient tunnel construction were analyzed. The problems of using ordinary planar TBM in steep gradient tunnel construction were pointed out. On this basis, the priciples of pump controlled differential cylinder, the dynamics of variable displacement pump, and the closed loop control algorithms were reviewed. Their problems were pointed out, and the main study work was proposed.In chapter 2, a novel electro-hyraulic control system of the SGTBM thrust system was proposed, and the variable displacemt pump was the key component of the system. The dynamcis of the swashplate variable displacenement axial piston pump were analyzed, the piston kinematic and dynamic equations in the conical cylinder were established, the pressure distribution in the cylinder bore was solved, and the relationship between the swashplate average load torqe and swashplate angle, swashplate angular speed, pump load pressure and the pump input shaft speed was unconvered. On this basis, the dynamics of the pump were simplified for ease of controller design.In chapter 3, the pressure dynamics of the SGTBM thrust system during start and stop stage were analyzed, the switching characteristic, non-minimum phase characteristic, and the large time-varing disturbance were pointed out, which will cause adverse effects on the controller design. To deal with the time-varing disturbance in the pressure dynamics, a disturbance observer was used to estimate the time-varing disturbance, and the estimated disturbance was used in the feedforward controller design to reduce the uncertainties in the system, in addition, the disturbance observer can gurantee the boundness of the disturbance estimation error. To deal with the non-minmum phase characterisitic of the system, the output redefinition method was used to transform the original system, and the transformed system was minimum phase corresponding to the redefined output, in addition, the desired trajectory for the redefined output was designed to guarantee the transient tracking performance. To deal with the switching characteristic in the system, the common Lyapunov method was used to design the feedback controller. Because the switching conditions of the controlled system and the feedforward controller were different, the error dynamics have four subsystems, the common Lyapunov method was used to prove the stability of the controller. Finally, the performance of the designed controller was validated through the simulation analysis and experimental contrast.In chapter 4, the pressure dynamics of the SGTBM thrust system were established, the parameter uncertainties in the system was pointed out, in addition, saturation nonlinearities also existed in the system. To guarantee the dynamic perforamce and stability of the system in the presence of input saturation and parameter uncertainties, command filtered backstepping scheme was introduced in the controller, in which the virtual control signal was used as the input signal of the second order filter, of which the output signal was used as a the actual control input. By this means, the control input would not exceed the predetermined amplitude and velocity limit. In addition, the closed loop system stability can still be guaranteed when the control input was saturated. The command filter was also used to calculate the approximation of the virtual control derivative, which eliminated the analytical derivation of the virtual control input, therefore, the differential explosion problem in the backstepping method was solved. On this basis, a compound adaptive method, which used the tracking error and the prediction error simultaneously to estimate unknown paramters, was used. Finally, the performance of the designed controller was validated through the simulation analysis and experimental contrast.In chapter 5, a cascade controller was used for the velocity control of SGTBM thrust system. In this controller, the outer loop is the velocity controller, and the inner loop is the pressure controller, these two controllers were independent of each other. As a result, the pressure dynamics in the thrust cylinder can be neglected, and the thrust cylinder can be regarded as an ideal force generator. To slove the problem of the unknown load force, a load force disturbance observer was proposed to replace the force sensor, and the estimated load force was used in the feedforward controller, this observer can gurantee the boundedness of the estimation error. The performance of the designed controller was validated through the simulation analysis and experimental contrast.In chapter 6, the present layout solutions for the TBM thrust system were analyzed. To reduce the segment damage, the thrust force uniform distribution performance index was established, a reconfigurable thrust system based on four-group system was established. The reconfigurable thrust system was used for a certain type of TBM thrust system and its geological adaptability was analyzed. Compared with fixed four-group thrust system, the reconfigurable thrust system can guarantee small uneven load confronted with large load torque.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 subjected were presented.