Investigation Into Stiffness Analysis And Design Method Of A TBM Gripping-Thrusting-Regripping Mechanism

Closely combined with China’s urgent demand for independent research and development of TBM(Tunnel Boring Machine),the topological structure,force/stiffness modeling and forward design method of the open TBM’s GTRM(Gripping-Thrusting-Regripping Mechanism)are studied in this paper with a goal to provide an important technical foundation for the theoretical design and engineering application of such mechanisms.The following contributions have been made.In the aspect of topological structure and kinematics,the number and type of DOF(Degree of Freedom)of GTRM are analyzed and determined.The design criteria of mechanism topology structure satisfying the requirements of tunneling operation under complex geological conditions are proposed.The position inverse solution model which reflects the mapping relationship between the pose of the cutter head and the length and attitude of cylinders is established.The mapping relationship between the micro displacement of the cutter head and the deformation of each chain is analyzed.The above work lays a mathematical foundation for the force and stiffness modeling and analysis of the mechanism.In the aspect of force analysis,the static of the mechanism can be established by constructing the constraining wrench of the cutterhead-mainbeam-saddle combination and projecting the static force equilibriums of the saddle and the gripper cylinder to the appropriate direction and other means.The established static model has concise form and clear physical meaning.It can be used to calculate the thrust of the cylinder required to resist the tunneling load,and calculate the tunneling load by measuring the cylinder thrust,which can provide important theoretical basis for the design and control of the mechanism.In the aspect of stiffness modeling,a semi-analytical stiffness model is formulated by means of the micro-displacement jacobian matrix of the mechanism,which takes into account the elastic contribution of all chains and the mian beam.The model takes into account the stiffness of the mechanical system,the hydraulic system and the contact stiffness of surrounding rock,and can accurately reflect the stiffness characteristics of the mechanism.The stiffness coefficient of each chain and main beam is solved by means of elastic mechanics and finite element simulation.The variation law of the mechanism’s anisotropic stiffness with the pose in the working space and its main influencing factors are revealed by an example.In the aspect of mechanism design method,the corresponding performance index parameters are put forward according to the construction requirements of GTRM,and the design idea of the mechanism is clarified.The design criteria of main parts such as driving cylinder and main beam are given and the key design parameters are selected.By means of response surface modeling and sensitivity analysis,the influence of design parameters on the performance parameters of the mechanism is revealed.The hierarchical design method and process are put forward,and the parameter design of a prototype is completed.By comparing with Robbins engineering prototype,it is found that the mechanism designed in this paper meets the relevant design requirements.The research results have been used to guide the design of two TBM engineering prototypes,which has important theoretical significance and practical value for advancing the engineering application of relevant technology of TBM.