| In the fields of textile machinery,automobile diesel engines,light industrial equipment,and aerospace industry,non-circular contour turning has its application scenarios.The shape accuracy of non-circular contour parts will directly affect the transmission accuracy and efficiency of the mechanism system where it is located.Compared with the traditional fixed tool on the turning tool system,the real-time variable tool angle compensation processing scheme makes up for the problem of periodic changes in cutting pressure angle and cutting linear velocity during its processing.Existing non-circular contour turning research is mainly focused on improving the positioning accuracy of fast radial servo drives,while ignoring the shape accuracy deviation caused by the compound motion of all feed drives.This paper proposes a novel control structure that takes shape error as a direct target and compensates it.In order to improve the turning precision of non-circular contours with variable angles,shape error estimation and online compensation strategies are proposed here.In this paper,the mechanical structure of the self-developed non-circular contour turning machining platform is modeled,and the kinematics analysis of the turning machining platform based on the DH method is carried out.,That is,the kinematics between the two solutions.In addition,this article also illustrates the variable tool angle machining mechanism of the noncircular contour turning machining platform,which is the key to ensure that the turning angle is constant at zero during the machining process.At the same time,the shape error during processing is defined,and the corresponding compensation strategy is proposed.It is theoretically proved that the position of the projection point of the actual tool tip point on the ideal contour can be calculated by the Newton-Raphson iterator,and it is proved that as the compensation gain becomes larger,the shape error of online compensation will be reduced according to the derived mathematical formula small.However,due to the existence of the jury criterion,the compensation gain cannot be very large,otherwise it will cause the dynamic system of the non-circular contour turning platform to lose stability.In order to actually verify the online compensation algorithm of the shape error of the noncircular contour turning platform,it is necessary to adjust the servo parameters of the main shaft,the tool axis and the linear point motor axis to keep its tracking error small and stable.In this paper,the pseudo-random binary torque excitation signal is used as input,and the unbiased least squares is used as the identification method to obtain the rotational inertia of the main shaft and the tool shaft,so as to adjust the servo parameters before verifying the error compensation experiment.The error compensation verification experiment adopts a star profile and divides three groups of different turning speeds.Compares the shape error size in the two cases with or without online compensation.The final analysis shows that: in the process of real-time variable tool angle machining method,if online estimation is added and The algorithm to compensate the shape error,then the shape error of non-circular contour turning will be significantly reduced. |
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