Design and kinematic analysis of the four-level rigid trunk mechanism based on 4-SPS/U

Abstract

A four-level rigid trunk mechanism based on 4-SPS/U, with SPS as the driving branch and U pair as the middle constrained driven branch, is innovatively proposed in this paper. Based on the innovative design of this trunk mechanism, it can improve the flexibility of the hexapod mobile robot's posture adjustment and changes in various motion modes such as walking, water propulsion, climbing and rolling. Firstly, the screw theory is adopted to calculate the degree of freedom of the trunk mechanism. Secondly, a combination of closed vector method and the characteristic structure configuration decoupling method has been applied to constructing the inverse kinematics solution, and deriving the velocity and acceleration models as well as analyzing the high posture flexibility in workspace of the trunk mechanism. Thirdly, theoretical simulation data diagram of the movement branch chain displacement, end height, speed and acceleration of the trunk mechanism are calculated through theoretical numerical examples, and the excellent motion characteristics of the 4-SPS/U-based four-level rigid trunk mechanism are analyzed . Finally, a quantitative comparison was made between the theoretical simulation data and the experimental data of the experimental prototype. The error rates of the variation curves of the displacement length, height, velocity and acceleration of the driving branch chain were 0.8%, 0.2%, 0.5% and 0.9%, which verified the correctness and reliability of the theoretical derivation.

KEYWORDS:

• Trunk mechanism
• screw theory
• kinematics modeling
• workspace

Acknowledgments

The authors sincerely thanks to Professor Jizhuang Fan and Mr. Gangfeng Liu of Harbin Institute of Technology for his critical discussion and reading during manuscript preparation.

Funding

Supported by National Natural Science Foundation of China (Grant No.U2013214), Support by Self-Planned Task of State Key Laboratory of Robotics and System (HIT) （NO. SKLRS202001A03）

Data availability statement

The datasets supporting the conclusions of this article are included within the article.

Additional information

Notes on contributors

Yitao Pan

Yitao Pan, born in 1991, is currently a doctoral student at State Key Laboratory of Robotics and System (HIT), Harbin Institute of Technology. E-mail: [email protected]

Gangfeng Liu

Gangfeng Liu, born in 1980, is currently an associate professor at Harbin Institute of Technology, a PhD tutor at State Key Laboratory of Robotics and System (HIT). He received his PhD degree from Harbin Institute of Technology, China. His research interests include configuration design and intelligent control of special operation Robot. E-mail: [email protected]

Jizhuang Fan

Jizhuang Fan, born in 1976, is currently an professor at Harbin Institute of Technology, a PhD tutor at State Key Laboratory of Robotics and System (HIT). He received his PhD degree from Harbin Institute of Technology, China. His research interests include bionic robots and service robots in extreme environments. E-mail: [email protected]

Shuqi Wang

Shuqi Wang, born in 1994, is currently a doctoral student at State Key Laboratory of Robotics and System (HIT), Harbin Institute of Technology. E-mail: [email protected]

Yuan Chen

Yuan Chen, born in 1976, is currently an professor at Shandong University . He received his PhD degree from Harbin Institute of Technology, China. His research interests include robot mechanism and motion control, mechanical engineering test technology. E-mail: [email protected]