| With the rise of tunnel excavation engineering,shield machine technology has been rapidly developed and widely used.Due to the complex underground stratum,the tool will often wear or break.The traditional tool changing technology has the disadvantages of high cost,long cycle and low safety,so the demand of automatic tool changing technology of cutter head is becoming more and more prominent.To this end,the paper designs a modular tool changing robot,through static analysis to verify whether the stiffness and strength meet the requirements.On this basis,kinematics analysis and trajectory planning are carried out to ensure the smooth operation of tool changing process.Considering the existence of systematic errors and random errors,an error model based on screw theory is established to analyze the sensitivity of endpose errors to different systematic errors.According to the clearance characteristics of the rotating joint,a position and attitude error model is established based on the spinor-vector method to analyze the effect of the static pose on the clearance deflection and deviation.Then the contact-friction model is established to analyze the dynamic characteristics of the mechanism with clearance.Finally,the dynamic characteristics of various error parameters are analyzed,and the reliability is analyzed by using the neural network-monte carlo method.The main contents are as follows:(1)Modular design and static analysis of tool changing robot.According to the spatial structure characteristics of shield tunneling machine,the structural design scheme of modular tool changing robot is determined.The overall structure is mainly divided into:base,telescopic and rotating structure,quick changing connection device,end-effector and other modules.The strength and stiffness requirements of the manipulator are verified by the static analysis under the condition that the manipulator is fitted with a large mass tool.(2)Kinematics analysis and trajectory planning of tool changing robot.In order to verify the feasibility of space operation of modular tool changing robot,kinematics calculation is carried out,and the position and space distribution of the robot is analyzed.The results show that the robot meets the requirements of space operation.In order to avoid the singularity phenomenon in the process of joint motion,joint space programming method is used to carry out 3-3-3,5-5-5 and 4-5-5 multi-node multi-curve trajectory planning for the specific path of the robot.Simulation results show that 4-5-5 can get a relatively stable acceleration.It can effectively solve the problems of the step of adding velocity and the big mutation of adding velocity of quintic polynomial in the process of cubic polynomial programming.(3)Accuracy analysis of static position and attitude of tool changing robot.The mathematical models of dimension error and joint Angle transmission error are established by screw theory,and the influence of different errors on the end precision is analyzed by control variable method under specific position and pose.The deflection and deviation of the joint with clearance are quantitatively analyzed by using screw theory and three-dimensional space vector method.(4)Impact and wear analysis of rotary joints with clearance.Based on the contact-friction model of joint clearance,the dynamic characteristics of the mechanism with clearance are analyzed.The end velocity,acceleration and contact force of the joint under different parameters,such as clearance size,rotational velocity and friction coefficient,were obtained by simulation analysis.The wear model was established to predict the wear and reconstruct the surface topography of the rotary joint with clearance.(5)Analysis of kinematic characteristics and reliability of tool changing robot.When considering the factors of robot weight,load and flexible deformation of bar,parameterized modeling is carried out for the tool changing robot.The dynamic simulation analysis of dimension error,joint transmission error and joint clearance error of connecting rod is completed.A rigid-flexible coupling model is established to analyze the variation characteristics of the terminal kinematic parameters.The neural network adaptive learning method and Monte Carlo method are used to calculate the robot motion reliability. |
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