Conceptual design and kinetostatic analysis of a modular parallel kinematic machine-based hybrid machine tool for large aeronautic components

Fang

International Journal of Aerospace Engineering

et al. 2019

This paper presents a novel redundantly actuated 2RPU-2SPR parallel manipulator that can be employed to form a five-axis hybrid kinematic machine tool for large heterogeneous complex structural component machining in aerospace field. On the contrary to series manipulators, the parallel manipulator has the potential merits of high stiffness, high speed, excellent dynamic performance, and complicated surface processing capability. First, by resorting to the screw theory, the degree of freedom of the proposed parallel manipulator is briefly addressed with general configuration and verified by Grübler-Kutzbach (G-K) criteria as well. Next, the inverse kinematics solution for such manipulator is deduced in detail; however, the forward kinematics is mathematically intractable. To deal with such problem, the forward kinematics is solved by means of three back propagation (BP) neural network optimization strategies. The remarkable simulation results of the parallel manipulator demonstrate that the BP neural network with position compensation is an appropriate method for solving the forward kinematics because of its various advantages, such as high efficiency and high convergence ratios. Simultaneously, workspaces, including joint space and workspace of the proposed parallel manipulator, are graphically depicted based on the previous research, which illustrate that the proposed manipulator is a good candidate for engineering practical application.

Section: Manipulator Descriptionmentioning

confidence: 99%

Forward Kinematics and Workspace Determination of a Novel Redundantly Actuated Parallel Manipulator

Fang

International Journal of Aerospace Engineering

et al. 2019

“…The 2T2R manipulator organically combines spatial translation and rotation, and is widely used in industry. For example, this manipulator can be combined with linear guide rail to form a five-axis linkage CNC machine tool [6, 7] and can also be used as motion simulator [8], vibration isolation platform [9], and so on. Among which, CNC machine tools have requirements for high accuracy of the manipulator, while the others have certain requirements for high-frequency and high-acceleration characteristics.…”

Section: Introductionmentioning

confidence: 99%

Kinematic and dynamic analysis of a 4-DOF over-constraint parallel driving mechanism with planar sub-closed chains

et al. 2023

In this paper, a new over-constrained parallel driving mechanism (PDM) with planar sub-closed chains is proposed. First, the number of over-constraints on the PDM is calculated. Then, an analysis is conducted as to the kinematics of the hybrid manipulator, including positions, velocities, and accelerations of all bodies. Furthermore, the Newton–Euler approach is taken to deduce the kinematic formula of each link and the formula of inertial force at the center of mass. However, it remains difficult to solve the equation since the number of equations is smaller than that of unknown variables. To solve this problem, the screw theory is applied in the present study to analyze the cause of over-constraints, with the link’s elastic deformation introduced as the supplement of deformation compatibility equations. Moreover, the actuation forces and constrained forces/moments are calculated simultaneously. Finally, the dynamic model is verified through simulation and experimentation. The proposed modeling approach provides a fundamental basis for the structural optimization and friction force computation of the over-constrained PDM.

“…As science and technology progresses, turbine blades, impellers, aircraft structural elements, and other machining parts have gotten increasingly complicated [1]. These parts generally feature complex geometries, large removal rate of materials, high dimensional precision and surface quality, which necessitates the machining equipment's capability of composite angle machining and high-efficiency machining [2,3]. Currently, most of these parts are machined by traditional 5-axis serial machine tools (SMTs).…”

Section: Introductionmentioning

confidence: 99%

A Symmetrical Arrangement Strategy based Real-time Toolpath Planning Method for A 5-DoF Fully Parallel Machining Robot

Wang,

Xie,

Xie

et al. 2023

Preprint

A 5-DoF fully parallel machining robot (PMR) with attitude coupling motion property has the potential to realize the high-efficiency and high-quality machining of complex parts with curved surfaces. From the perspective of mechanism, this kind of 5-DoF fully PMR can achieve no singularity in the workspace after optimum design, so the mobile platform can be adjusted to an arbitrary orientation directly and flexibly. In order to give full play to the above mechanical characteristics, the idea of planning orientation path in unit spherical coordinate system was proposed in our previous work, and then the orientation adjustment efficiency was improved. But the toolpath continuity and calculation simplicity remain to be solved. In light of this concern, the constraint equations to ensure the continuity between two adjacent B-splines are established, and the configuration of control points that can ensure the controllable curvature is derived. On this basis, a symmetrical arrangement strategy that generates shape limits for fitted B-splines to achieve high-order continuity is proposed, and a toolpath planning method is established accordingly. To reduce computational complexity in the feedrate scheduling stage, a linear constraints system is adopted to calculate the feedrate of each point, and the feedrate calculation and interpolation are conducted simultaneously to generate the motion trajectory in real-time. The trajectory planning of S-shaped toolpaths is conducted using the proposed method and the commercial ISG CNC kernel respectively. The comparison results show that the proposed method can effectively improve the motion efficiency, the complexity of calculation, and the fluctuation of feedrate and acceleration. This study provides a more efficient and effective trajectory planning method and is of great significance to the further development of the 5-DoF PMR.