| Shield machine, which is specializing in the use of digging tunnel, is special large high-tech construction equipment. It has many merits, such as high speed, high quality, safety, economy and so on. And now it is being developed to the direction of intelligent and integration of mechanical, electrical, hydraulic and control technology. Shield machine technology, which includes manufacture technology, computer technology, new material technology, automation and information technology, and administration technology, shows the scientific and technology level of one country.Since circular-section shield machine was used in digging tunnel in 1865, it has been used widely because circular section has many advantages, such as uniform force in each radial direction, less internal force, being made simply and controlled easily during construction. In following 100 years, because of its good construction performance, circular-section shield machine had been nearly used in all shield runnels.With the developing and utilizing of ground space, new requirements and demands is given to the section of tunnel. However, it is found that there are many disadvantages when digging special-section tunnel with circular-section shield machine, such as low efficiency, space wasted, etc. If special-section shield machine is used in digging special-section tunnel, it will reduce digging area; reduce the amount of dug soil, dealt residue soil and backfilled soil. And therefore working efficiency and space utilizing ratio is advanced. In order to realize this object, it is very important to research and develop new special-section shield machine. Above all the urgent problem is to study on the core component, cutting mechanism. In this paper, this is studied and presented.1. The internal stress status of soil before cutting head of working shield machine is analyzed in the paper. According to Coulomb Equality, when soil body is on limit balance status, the relationship between big stress and little stress is studies. And earth-retaining wall theory is simply introduced. Meanwhile, two methods of compuating maximum torque of shield machine cutting head, resistance torque computating method and experienced computating method, are introduced. Maximum torque of cutting head will be determined by comprehensive dealing of these two methods. 2. It is firstly been brought forward to select two deformed types of traditional five-role mechanism as model of cutting mechanism of special section shield machine and to use hybrid drive mechanical system as control mechanism of two-degree-of-freedom closed-loop five-role mechanism. Meanwhile, RTNA (Real Time Non-Adjustable) and RTA (Real Time Adjustable) are used as its power source. RTNA is mainly used to provide power for cutting mechanism and RTA is mainly used to adjust motion. These two input motions can produce any required output motion by a two-degree-of-freedom closed-loop mechanism. The pathway of its output can be of random style, such as ellipse, rectangle, arched-type and so on. And therefore it can be used to cut tunnel with any kind of section. Simple structure, abundant section, easy control, and good stress are all its merits.3. The condition of moving of cutting mechanism is analyzed. Basing on analysis result of five-pole mechanism limit positions, the condition of existing crank of plane two-degree-of-freedom five-role mechanism is drawn. Working space of two kinds of cutting mechanism is analyzed and there working range is also drawn.4. The condition of singularity of cutting mechanism is analyzed. Through analysis of two models, condition of two singularity positions of cutting mechanism is drawn. At these two positions, there will be dead point inevitably when cutting mechanism is running. The method of avoiding dead point is given out in this paper.5. Kinematics of cutting mechanism is studied. The motion of five-role mechanism's two kinds of deformed types as cutting mechanism of shield machine is compressively analyzed. Working position equality, velocity equality and acceleration equality are also deduced. Mathematical model of kinematics of two kinds of cutting mechanism is brought forward.6. Negative kinematics of cutting mechanism is studied. The negative motion of five-role mechanism's two kinds of deformed types as cutting mechanism of shield machine is compressively analyzed in this paper. Known motion disciple of output point 'P' and motion disciple of main motor will deduce the input parameters of servomotor. Working position equality, velocity equality and acceleration equality are also deduced. Mathematical model of negative kinematics of two kinds of cutting mechanism is brought forward.7. Mathematical model of kinetics of two kinds of cutting mechanism is brought forward basing on analysis on kinematics and negative kinematics. D'Alembert's principle is used to analyze second-level-role-group and mathematical model of kinetics of two kinds of cutting mechanism is therefore brought forward. This provide necessary mathematical model for control mode of hybrid drive mechanical system.8. Working point of cutter head and layout style of driving apparatus and five-rod mechanism is brought forward in this paper. It is very useful for selecting best layout diagram in actual structure design. Then according to different mode of hybrid drive, four kind s of exploratory scheme design of overall structure is done in the paper. And cutter head is improved and innovated to meet requirement of cutting in radial and axial direction at the same time.When the average five-role mechanism and its deformed type are used to dig tunnel with different special sections, such as rectangle, arc+ rectangle, ellipse, and so on, four examples are given out to study the effect of role length. According to examples, average five-role mechanism as cutting mechanism of shield machine is feasible, but its workspace is limited. Five-role mechanism's two kinds of deformed types as cutting mechanism of shield machine is more superiority than average five-role mechanism in versatility, agility, workspace, and so on. The cutting pathway and workspace is more plentifulness because of flexible combination of different poles of deformed five-role mechanism. It has obvious merits and widely applying foreground. It is more suitable to engineering practice.9. The software pakage of analysis and simulation of deformed five-role mechanism is developed in this paper by using C language. In addition, preliminary analysis and study about elliptical section tunnel is performed. The motion principle ofθp and rod l4 are obtained, and meanwhile the ellipse orbit can be output with the simulation software. Some characteristic curves ofθp andθ4 are obtained through the analysis. The greater the difference value of the major axis a and the minor b is, the greater the values of the angular displacementθ4, the angular velocity (θ|·)4 and the angular acceleration (θ|¨)4 near C1 and C5 on rod 4 are. The smaller the difference value is, the values ofθ4 and (θ|·)4 and (θ|¨)4 decrease more rapidly.
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