Dynamic error of multiaxis machine tools considering position dependent structural dynamics and axis coupling inertial forces

Proceedings of the Institution of Mechanical Engineers, Part B:

Lü

Zhang

et al. 2022

Due to high stiffness and quick response, dual-drive feed machines (DDFMs) are widely used in many precision CNC machines. The tracking errors of the two feed drives directly determine the machines’ accuracy. The performance of the position accuracy can be easily affected by the difference in the friction dynamic characteristics of the two axes. This paper proposes the state-dependent friction compensation (SFC) as an improved DDFMs error compensation method that can achieve better accuracy under unequal friction on the two feed drives. It is theoretically analyzed the influence of friction on the transmission stiffness of DDFMs. Moreover, the effects of time-varying factors (feed rates and mechanical structures) on the friction of dual axes are discussed. The innovation of the paper is that the SFC can adaptively take into account the influence of the variable dual-drive structure and feed rate on DDFMs’ position accuracy, and the compensation method combined with cross-coupled strategy is suitable for general dual-drive structure. Simulation and experiment results show that the proposed method can effectively improve the synchronization accuracy and tracking accuracy in a variety of feed operations (different feed rates, starting, and reversing).

Section: Parameter Identification Of State-dependent Friction Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A method to improve position accuracy for the dual-drive feed machines by state-dependent friction compensation

Proceedings of the Institution of Mechanical Engineers, Part B:

Lü

Zhang

et al. 2022

“…Over the past decades, many researchers have done a great quantity of researches on the mechanism of generation and transmission of geometric errors of numerical control (NC) machine tools and made important contributions to the modeling and compensation of geometric errors. The homogeneous transformation matrix (HTM) [7][8][9][10] based on the theory of rigid multibody kinematics [11][12][13] is used to establish the error transmission between cutter location and tool orientation. Multi-body system theory 14 based on the mathematical algorithm of the HTM broadens its application scenarios and convenience.…”

Section: Introductionmentioning

confidence: 99%

Interaction analysis of geometric tolerance of multi-axis machine tools based on kinematic Jacobian-Torsor model

Chen

Proceedings of the Institution of Mechanical Engineers, Part B:

Tian

et al. 2022

For the purpose that the multi-axis machine tools can machine workpieces flexibly and accurately, it is important to ensure that each axis of the machine tool can be linked with each other, and the geometric tolerances are within their required range. However, each tolerance is not only related to its own kinematic axis, but also affected by the comprehensive influence of other kinematic axes, which brings great difficulties to the modeling of geometric tolerances. This paper focus on developing a modeling methodology to describe the relationship between the range of machining geometric tolerance and the motional domain of machine tool axe based on an improved Jacobian-Torsor theory. General formulas for the expression of the geometric tolerances are derived. Experiments are carried out on five four-axis machine tools, type CNC-SH50, to verify the effectiveness of the proposed kinematic Jacobian-Torsor model in dealing with the interaction analysis of geometric tolerances.

“…Moreover, the lateral vibration of the screw significantly affects the lateral dynamic error. 26 The lateral dynamic error is an important part of the outside servo loop dynamic error, 27 which is coupled into the tracking error and contour error through the topological structure of the machine tools. 28 Therefore, this paper pays more attention to the evolution of lower-order lateral vibration and axial vibration of the SBSFS, on the basis of an elastodynamic model with a 6 DOFs end-effector.…”

Section: Introductionmentioning

confidence: 99%

Evolution of lower-order vibration mode of the slender ball screw feed system

Wang

Zhao

Proceedings of the Institution of Mechanical Engineers, Part B:

et al. 2022

Dynamic performance characterized by lower-order natural frequency and lower-order vibration mode is vital for the dynamic positioning accuracy of the ball screw feed system. This paper focuses on the evolution between the lateral vibration mode and the axial vibration mode of the slender ball screw feed system (SBSFS). Firstly, it is proved the first-order vibration mode transformation of the SBSFS is subject to the position of the nut based on an elastodynamic model. This model is established using substructure synthesis method considering the axial, torsional, and lateral deformation of the screw simultaneously through dealing with the screw as Timoshenko Beam elements. By comparing with the experimental results, the validity and accuracy of the established dynamic model are verified. The effects of the stiffness of the kinematic joints on the dynamic performance of SBSFS are then analyzed. The results demonstrate that the dynamic behavior evolution of the SBSFS undergoes the coupling effects from the kinematics joints’ stiffness. Furthermore, a dynamic index ( RSP) is proposed considering the evolution of the first-order vibration mode. On the basis of RSP, three optimization schemes are illustrated. The results show that the RSP can be used to evaluate the dynamic performance of the SBSFS considering the vibration mode.