Research Article
Controlling Hybrid Machine Tools concerning Error
Compensation of Chain Elements
Khanh Duong-Quoc ,
1
Thuy Le-Thi-Thu ,
1
Long Pham-Thanh ,
1
and Ngoc Nong-Minh
2
1
Division of Mechatronics, Faculty of Mechanical Engineering, ai Nguyen University of Technology,
ai Nguyen 24100, Vietnam
2
ai Nguyen University, ai Nguyen 24100, Vietnam
Correspondence should be addressed to uy Le-i-u; hanthuyngoc@tnut.edu.vn
Received 13 December 2021; Accepted 10 February 2022; Published 7 April 2022
Academic Editor: Yaoyao Wang
Copyright © 2022 Khanh Duong-Quoc et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
is paper introduces a methodology for controlling parallel robots in case they are used as a kind of specialized fixture to expand
the technological capabilities of machines. e parallel robot is mounted on the workbench to extend the number of degrees of
freedom. However, there are always measurable kinematic errors of the workbench which will be eliminated by the robot’s
motion. e actual working motion of the robot is then still performed by its active joints. erefore, the displacement of each
movable joint is now decided by two sources, one is due to the error compensation motion of the workbench, the other is the
required work movement. According to the superposition principle, these two motions are combined into a single displacement
characteristic curve to control the robot. e base exchange technique to determine the error compensation motion of the
workbench, the technique of solving the inverse kinematics problem by the generalized reduced gradient (GRG) method, and the
principle of joint motion combination are then introduced in detail in the paper. Finally, an example with the hexapod is
presented. e obtained results, which use the robot itself to generate error-compensated movements of the workbench by means
of the base exchange technique, will open up the possibility of intervening in hybrid machine systems to ensure the desired
forming accuracy without no hardware intervention required.
1.Introduction
Since their first appearance for more than two decades,
parallel robots have been expected to replace conventional
Computer Numerical Controlled (CNC) machines with
serial kinematics. However, there are many unresolved
problems existed, especially in machining applications that
require precision, rigidity, dexterity, and large workspaces
[1].
To improve the problem of limited working space while
preserving the characteristics such as high rigidity, high
precision, and high speed of parallel robots, many scholars
have researched, designed, and applied a combination of
chain mechanisms (such as CNC machines) and parallel
robots, called hybrid mechanisms. Hybrid mechanisms are
mainly used in machine tools [2]. Zhu et al. [3] considered
the 3-TPS hybrid machine tool (In there, the parallel has
three legs, each leg has three joints: T-Twisting joint,
P-Prismatic joint, and S- Spherical joint). e research has
solved the problem of selecting motor parameters and
mechanism design. Zhang et al. [4] presented a novel parallel
manipulator with one translational and two rotational de-
grees of freedom (DOF). is 5 DOF hybrid kinematic
machine tool is used in the aerospace field for large het-
erogeneous complex structural component machining. In
this research, a three-degree-of-freedom 2PRU-PRPS par-
allel manipulator is proposed to increase stiffness (P denotes
the Prismatic active joint, R denotes the Rotational joint, and
U denotes the Universal joint). Song et al. [5] performed
kinematic modal characteristic analysis on the 4PRR-P
Hindawi
Journal of Robotics
Volume 2022, Article ID 4366888, 9 pages
https://doi.org/10.1155/2022/4366888