Study On Dynamic Characteristics Of Redundantly Driven Revolving System Of Shield TBM

Shield TBM is a kind of special engineering machine for tunnel excavation, which is widely applied in tunnel constructions such as metro subways and road tunnels. When a domestic-made shield TBM was conducting underground constructions, cutterhead stalls even failures of drive shaft frequently took place in its revolving system. That would lead to the stoppages of the machine and induce great loss. The revolving system of a shield TBM bears the excavation load directly, and so it is usually redundantly driven by multiple motors due to the need of large power and torques, which means the multi-point gear meshing is also employed. The power transmission process of redundant drive and multi-point gear meshing is complex and their dynamic characteristics are different from that of common statically determinated mechanical systems. New problems of the load sharing performance of the drive and transmission system as well as the stability of the revolving system arise. Unevenly load distribution is very inclined to happen in the redundantly driven revolving system of shield TBM, which often leads to catastrophic failures such as some transmission gears broken and even drive shaft failures. Due to the lack of complete and systematic design theories for shield TBMs, most domestic-made ones were still made by directly borrowing ideas from mature designs of foreign ones. Therefore, to study the dynamic characteristics of the revolving system of shield TBM will have great importance on improving its load sharing performance and stability, decreasing unevenly load distribution, preventing shaft failure and ensuring the normal work of shield TBM.This text focuses on the redundantly driven revolving system of shield TBM, aiming at the redundant driven and multi-point gear meshing, investigates the reason of drive shaft failure in virtue of studying the load sharing performance under complicated excavation loads. The study starts from the bending-torsional coupled vibration, and then puts forwards the determination theory of stability of redundantly driven revolving system. Based on that, the analysis method of load sharing performance of the system is established and the mechanism of shaft failure is studied. The dynamic model of the shield TBM, considering all the factors during excavation, is established, firstly. Based on the Floquet-Lyapunov theory, the analysis methods of the dynamic stability and load-sharing performance by calculating the Floquet multiplier and the load sharing factor are proposed. The dynamic characteristics of a typical shield TBM under complex excavation loads are investigated and evaluated. The test rig of the shield TBM revolving system is then built to verify the method. The main contents are listed as follows:(1) Comprehensive dynamic model of shield TBM tunnelingThrough load analysis during excavation, the theoretical dynamic model of the shield TBM has been established, considering the interactions between the redundantly driven revolving system, the hydraulic propulsion system, the shield body and the geologic conditions. Multiple vector-controlled variable frequency electric motors, multi-point gear meshing, dynamic excavation loads are taken into consideration.(2) Dynamic stability conditions of the multi-point gear meshingThe parameter vibration problem due to the time-varying mesh stiffness in the multi-point gear meshing process is analyzed. In virtue of Floquet-Lyapunov theory, the analysis method of dynamic stability of shield TBM revolving system is studied and key parameters'influence on the instability conditions have been deeply investigated.(3) Load sharing performance of the redundantly driven revolving systemThe load sharing performance of the redundantly driven revolving system is studied. Based on the Floquet-Lyapunov theory, the analysis method for load-sharing performance of the redundantly driven revolving system of the shield TBM has been proposed. By calculating the load sharing factor, parameters'influences on the load sharing performance have been studied.(4) Dynamic characteristics of shield TBM revolving system in mixed-face conditionsThe dynamic behavior of a typical shield TBM revolving system has been simulated and evaluated. The results show that, while adjusting the cutterhead reference speed in time could effectively reduce the torque loads and overcome the adverse excavation environments. Reasonable distribution of the pinion gears and drive motors could improve the load sharing performance of the revolving system, and therefore the failure of drive shaft could be avoided.(5) Simulation test of reduandantly driven revolving system of shield TBMIn virtue of similarity theory, the test rig for shield TBM redundant driven revolving system has been set up. Through applying the torque and bending moment loads by load simulating set and measuring the output torque and speed of each driving motor, the influence of key structural parameters on load distribution of driving pinions have been verified. The results show that, under the axial force load and bending moment load, the torque load on each driving motor would be unevenly distributed; by arranging the driving pinions and motors at proper positions could effectively improve the load-sharing performance.Based on the analysis method of dynamic stability and load sharing performance for redundantly driven revolving system established in this text, parameter design and optimization could be carried out on the redundantly driven revolving system of shield TBM. By means of that, the dynamic characteristics would get improved, the shaft failure accident would be prevented and continuous operation of the shield TBM could be realized.