Research Article
A novel second subproblem for
two arbitrary axes of robots
Haixia Wang
1,2
, Xiao Lu
1,2
, Ziye Zhang
3
, Yuxia Li
1,2
,
Chunyang Sheng
2
and Li Gao
4
Abstract
The Paden–kahan subproblem is a simple and flexible method to solve the closed-forminverseresolutionbut
limited by the geometrical structure of robots, which is very d ifficult to be kept because of processing and
installation. Therefore, a closed-form solution on arbitrary confi gurations is an important issue in the field of robotic
inverse kinematics. A novel second subproblem is firstly proposed in this study based on the product-of-
exponentials model adapting to the two arbitrary axes without geometric constraints (parallel, vertical, disjoint,
and so on). Furthermore, the algebraic methods involving the basic properties of the screw theory and Rodrigues’
rotation formula are employed for the solution, which makes the constraint equations of the second subproblem
solvable for arbitrary configurations. This methodology can be applied to the inverse solutions of 5-degree-of-
freedom robots t hat satisfies the Pieper criterion and can express the inverse solutions via tw o common for-
mulas. Finally, the simulation and the real-world experiment demonstrated the accuracy of the method and the
validity, respectively.
Keywords
Inverse kinematics, closed-form resolution, POE model, screw theory, Rodrigues’ rotation formula
Date received: 31 March 2017; accepted: 30 January 2018
Topic: Robot Manipulation and Control
Topic Editor: Andrey V Savkin
Associate Editor: Jayantha Katupitiya
Introduction
The mapping relationship between the end effector and the
joint angles of robots, referred to as a robot kinematics
model, is very important in robot applications.
1
This rela-
tionship can be defined as forward or inverse kinematics,
wherein the forward kinematics is to build the relationship
in terms of the position and orientation of the end effector
from the joint angles and can be easily determined by the
link parameters and joint variables of a robot. Conversely,
inverse kinematics (IK), which resolves the jo int angles
from the model based on the position and orientation of
the end ef fector, is a nonlinear and configuratio n-
dependent problem that may have multiple solutions.
2
As solving the IK problem is significantly complicated,
a closed-form inverse solution is desirable because it offers
1
Key Laboratory for Robot and Intelligent Technology of Shandong
Province, Shandong University of S cience and Technology , Qingdao,
China
2
College of Electrical Engineering and Automation, Shandong University
of Science and Technology, Qingdao, China
3
College of Mathematics and Systems Science, Shandong University of
Science and Technology, Qingdao, China
4
College of Mechanical and Electronic Engineering, Shandong University
of Science and Technology, Qingdao, China
Corresponding author:
Haixia Wang, Key Laboratory for Robot and Intelligent Tec hnology of
Shandong Province, College of Electrical Engin eerin g and Automation,
Shandong University of Science and Technology, Qingdao 266590, China.
Email: hxwang@sdust.edu.cn
Internation al Journal of Advanced
Robotic Systems
March-April 2018: 1–7
ª The Author(s) 2018
DOI: 10.1177/1729881418769194
journals.sagepub.com/home/arx
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