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Mechanism-Environment Integrated Modeling Of Thrust System And Grouping Method Of Shield Machine

Posted on:2018-07-22Degree:DoctorType:Dissertation
Country:ChinaCandidate:W T GuoFull Text:PDF
GTID:1362330590455197Subject:Mechanical design and theory
Abstract/Summary:PDF Full Text Request
Thrust system is a typical mechanical system with super-redundant controllable inputs in the shield machine.The operation efficieny of the thrust system depends on the reasonable grouping of the super-redundant inputs,namely thrust grouping.As a carrier to move forward,turn and correct the tunnel line,the design of the thrust grouping determines not only the quality of the tunnel construction,but also the tunneling energy consumption,efficiency and cost of the project.To effectively support the grouping design of the thrust system and satisfy the need of smart equipments and automatic driving,this project will investigate basic problems including the grouping principle,grouping mechanism,modeling method,performance indexing,solution algorithm of the thrust forces,configuration of thrust forces,adaptive planning of the thrust travels,grouping optimization and adaptive grouping as well as its physical solution.The specific results of this research are as follows:(1)This paper introduced the concept of passive limb from parallel mechanism and proposed a novel method that can effectively express the environmental constraint of the earth pressure while the shield excavating.This method considered the thrust system and the environmental constraints as one integrated system by synthesized perspective.An equivalent mechanism model that can describe the kinematic and static of the shield-constraints system is established.Sucessfully explain the contradiction between the singularity of the current model of the thrust system and the normal function of the shield machine.Modified the type synthesis approaches for the parallel mechanisms with passive limbs allocated the wrenches among both active limbs and passive limbs.Introduced the wrench graph method to analyse the singularity of the equivalent model of thrust system and derived the singularity conditions.(2)A universal kinematical modeling and analyzing method of the shield-constraints equivalent mechanism with both active limbs and passive limbs was proposed.The relationships between the rotation center and the earth constraints was unraveled through this kinematical analysis.The accurate quantity relationships between the earth constraints and the passive limbs was derived too.The deviation principle of the shield motion was discovered according to the position parameter of the rotation center in the kinematic model of the thrust system.An self-adaptive-deviation-correcting thrust strategy was proposed according to the dynamic position of rotation center.The viability and the engineering value of the self-adaptive-deviation-correcting thrust strategy was proved by case study.(3)A universal statical model of the shield-constraints equivalent mechanism was established.The mutual relationships between the active thrust forces and the passive constraining forces was analyzed.The influence between the thrust behavior and the surrounding earth environment was then unraveled.A group-adjustable thrust hydraulic system was proposed in order to reallocate the cylinders into different group.The uniformity index of the thrust forces was established and the self-adaptive grouping thrust strategy of the shield thrust system was proposed.The numerical simulation was performed in the case study to prove the viability of the self-adaptive grouping thrust strategy.(4)An experiment prototype of the grouped thrust system was produced after considering shield-constraints mutual influence based on the theoretical modeling and analyzing.The passive limbs were designed to simulate the earth constraints exerted on the shield while the it excavating.A rope-mass mechanism was added into the prototype to simulate the external loads of the shield machine.A pose-copy mechanism was designed to record the pose of shield for multi-rings of thrust.A series experiment was performed to simulate the practical thrust.The position of the rotation center was verified to be effective to the control accuracy of the shield motion.The the grouped thrust forces were measured in a series experiments and the uniformity were then calculated after each experiments.The improvement of the thrust effiency was proved for the the self-adaptive grouping thrust strategy by a comparison experiment.The experiments accurately simulated the motions and forces of the thrust system as it works in real tunnel engineering.The experiment prototype also verified the correctness and validity of the established equivalent model and grouping theory of the shield thrust system.
Keywords/Search Tags:shield machine, thrust system, environmental constraint modeling, performance indexing, self-adaptive grouping
PDF Full Text Request
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