| The medical manipulator is an important part of the radiotherapy system for tumor.In order to make the radiotherapy have better effect,the medical positioning manipulator system needs to have higher control accuracy and positioning accur acy.In order to improve the control accuracy of the medical positioning manipulator,it is necessary to establish an accurate dynamic model of the medical positioning manipulator and analyze and predict the dynamic characteristics Positioning accuracy and dynamic performance play an important role.Some nonlinear factors contained in the manipulator itself will affect its dynamic characteristics,which should be considered in modeling.Therefore,in this paper,the medical positioning manipulator with flexible arm is taken as the research object.The dynamic model of the coupling of medical positioning manipulator is established,which includes joint friction,meshing clearance,meshing damping,time-varying meshing stiffness and flexible deformation of large and small arms between the central wheel and three planetary wheels in RV Reducer at the joint,and the corresponding dynamic characteristics are analyzed.Finally,the coupling is analyzed The accuracy of the dynamic model is verified by simulation experiments,and some other dynamic characteristics are analyzed.The specific contents and results are as follows:(1)Firstly,the medical positioning manipulator is simplified properly,and the contact force at the joint hinge is obtained by using darlambert's theorem,and the friction torque of the joint is calculated based on the Coulomb friction model.Then,the dynamic model of the manipulator without friction and with joint friction is established based on the Lagrangian equation,and the numerical sol ution of the model is compared and analyzed Influence.(2)In this paper,the force analysis of the RV Reducer,which is the transmission component at the joint,is carried out.The dynamic model of RV Reducer is established considering the meshing clearance,meshing damping and time-varying meshing stiffness between the center wheel and three planetary wheels.The dynamic model of the medical positioning manipulator including RV Reducer is further established.Through the numerical solution analysis,the meshing clearance,meshing damping and time-varying meshing are obtained The closing stiffness makes the output torque at the end of the reducer and the angular acceleration of the mechanical arm fluctuate at a higher frequency.The larger the clearance is,the larger the impact of gear engagement is,the larger the amplitude of the fluctuation is,and the more violent the fluctuation is.(3)Based on the assumed mode method and Lagrange equation,the dynamic model of the medical flexible positioning manipulator is established.Combined with the joint friction and RV Reducer dynamic model established in Chapter 2 and Chapter 3,the coupling dynamic model of the medical positioning manipulator is further established,and the numerical solution analysis is carried out.Under the coupling effect of the nonlinear factors considered,the medical swing is obtained The angular velocity,angular acceleration and joint contact force of the position manipulator fluctuate violently with high frequency.The increase of joint friction can weaken the fluctuation,but it will cause the energy loss of the system,and the values of angular velocity and angular acceleration will decrease accordingly.(4)Two simulation software Matlab and Adams are used to verify the coupling dynamic model of the medical positioning manipulator,which verifies the accuracy of the model.At the same time,the simulation experiments of the end track of the medical positioning manipulator and the angular acceleration under different loads are carried out.It is concluded that the larger the friction is,the larger the deviation is,the greater the end load is,the greater the friction is at the joints,the increase of the energy loss of the system,resulting in the decrease of the fluctuation and amplitude of the angular acceleration. |
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