For the high carrying capacity of the human-carrying walking chair robot, in this paper, 2-UPS+UP parallel mechanism is selected as the leg mechanism; then kinematics, workspace, control, and experiment of the leg mechanism are researched in detail. Firstly, design of the whole mechanism is described and degrees of freedom of the leg mechanism are analyzed. Second, the forward position, inverse position, and velocity of leg mechanism are studied. Third, based on the kinematics analysis and the structural constraints, the reachable workspace of 2-UPS+UP parallel mechanism is solved, and then the optimal motion workspace is searched in the reachable workspace by choosing the condition number as the evaluation index. Fourth, according to the theory analysis of the parallel leg mechanism, its control system is designed and the compound position control strategy is studied. Finally, in optimal motion workspace, the compound position control strategy is verified by using circular track with the radius 100 mm; the experiment results show that the leg mechanism moves smoothly and does not tremble obviously. Theory analysis and experiment research of the single leg mechanism provide a theoretical foundation for the control of the quadruped human-carrying walking chair robot. 1. Introduction Walking aids have been a research hot point for several years [1]. The human-carrying walking chair robot, which is one of walking aids, could help the elderly and the lower limb disabled walk freely in the outside and navigate on uneven ground. The human-carrying walking chair robot, which is different from the wheeled robot and the ordinary legged robot, not only needs to steadily walk by using leg mechanism as supporting point [2, 3], but also needs to bear weight from itself and different passengers [4]. These put forward higher requirements for performance of the leg mechanism of the walking chair robot. At present, most of human-carrying walking chair robots for the elderly and the lower limb disabled are implemented by selecting serial mechanism as leg mechanism [5–9], such as the I-Foot robot, the Hubo FX-1 robot, and the Hyperion4 robot. Using the serial mechanism as the leg mechanism, the whole volume and weight of the robot are bigger and the carrying capacity is smaller. For instance, the robot I-Foot is 200？kg in mass and can carry a person with 60？kg; Hubo FX-1 is 150？kg in mass and can bear the load of 100？kg. Compared with the serial mechanism, parallel mechanism (PM) can make up for the deficiencies of the serial mechanism and form the complementary
References
[1]
W. Ping, X. M. Dun, and W. D. Chen, “The general overview of research on assistant robot,” Robot Technique and Application, no. 1, pp. 31–34, 2009.
[2]
J. Liu, X.-G. Zhao, and M. Tan, “Legged robots: a review,” Robot, vol. 28, no. 1, pp. 81–88, 2006.
[3]
J. H. Zhang, X. J. Zhang, M. L. Zhang, and F. H. Guo, “Eight wheel-legged mobile robot platform design and kinematic analysis,” Chinese Journal of Machine Design, vol. 29, no. 8, pp. 35–39, 2012.
[4]
C. Y. Zheng, Q. F. Zhao, P. S. Ma, H. Q. Zhang, and Z. Gou, “Mechanism design of a biped walking-chair robot,” Robot, vol. 28, no. 3, pp. 297–302, 2006 (Chinese).
[5]
K. Stefan, “On the anticipation of ethical conflicts between humans and robots in Japanese Mangas,” International Review of Information Ethics, vol. 6, no. 12, pp. 63–68, 2006.
[6]
J.-H. Kim, J.-Y. Kim, and J.-H. Oh, “Adaptive walking pattern generation and balance control of the passenger-carrying biped robot, HUBO FX-1, for variable passenger weights,” Autonomous Robots, vol. 30, no. 4, pp. 427–443, 2011.
[7]
S. Nakajima and E. Nakano, “Adaptive gait for large rough terrain of a leg-wheel robot (Fifth report: integrated gait),” Journal of Robotics and Mechatronics, vol. 21, no. 13, pp. 419–426, 2009.
[8]
K. Yoneda, “Light weight quadruped with nine actuators,” Journal of Robotics and Mechatronics, vol. 19, no. 2, pp. 160–165, 2007.
[9]
J. Tang, Q. Zhao, and R. Yang, “Stability control for a walking-chair robot with human in the loop,” International Journal of Advanced Robotic Systems, vol. 6, no. 2, pp. 115–120, 2009.
[10]
Y. Sugahara, G. Carbone, K. Hashimoto, M. Ceccarelli, H. O. Lim, and A. Takanishi, “Experimental stiffness measurement of WL-16RII biped walking vehicle during walking operation,” Journal of Robotics and Mechatronics, vol. 19, no. 3, pp. 272–280, 2007.
[11]
Y. Rong and Z.-L. Jin, “Dynamic modeling of 3-DOF parallel mechanical leg and peak prediction of servo motor,” Optics and Precision Engineering, vol. 20, no. 9, pp. 1974–1983, 2012.
[12]
H. Wang, Z. Qi, Z. Hu, and Z. Huang, “Application of parallel leg mechanisms in quadruped/biped reconfigurable walking robot,” Chinese Journal of Mechanical Engineering, vol. 45, no. 8, pp. 24–30, 2009.
[13]
L. W. Tsai and S. Joshi, “Kinematics and optimization of a spatial 3-UPU parallel manipulator,” Journal of Mechanical Design, vol. 122, no. 4, pp. 439–446, 2000.
[14]
Z. H. Guo, S. S. Sun, X. Q. Hao, G. D. Niu, and L. S. Li, “Position analysis and simulation of 3-PUU translation parallel manipulator,” China Mechanical Engineering, vol. 17, no. 17, pp. 1787–1789, 2006.
[15]
Q. Li, Z. Chen, Q. Chen, C. Wu, and Z. Huang, “Structural condition for [PP]S parallel mechanism without parasitic motion,” Journal of Mechanical Engineering, vol. 46, no. 15, pp. 31–35, 2010.
[16]
A. Kuma and K. J. Waldron, “The workspace of a mechanical mechanism,” ASME Journal of Mechanical Design, vol. 103, pp. 665–672, 1981.
[17]
T. Huang, J. Wang, C. M. Gosselin, and D. J. Whitehouse, “Kinematic synthesis of hexapods with specified orientation capability and well-conditioned dexterity,” Journal of Manufacturing Processes, vol. 2, no. 1, pp. 36–47, 2000.
[18]
H. Yu, L.-N. Sun, P.-K. Liu, and H.-G. Cai, “Study on the workspace and parameter of novel 6-HTRT parallel robot,” Robot, vol. 24, no. 4, pp. 293–299, 2002.
[19]
Y. Cao, Y. Zhang, and Y. Ma, “Workspace analysis and parameter optimization of 6-RSS parallel mechanism,” Chinese Journal of Mechanical Engineering, vol. 44, no. 1, pp. 19–24, 2008.
[20]
X. J. Liu, L. J. Zhang, and F. Gao, “Geometrical determination of workspace for 6-dof parallel manipulators based on AutoCAD platform,” Robot, vol. 22, no. 6, pp. 457–465, 2000.
[21]
Y. Lu, P. Wang, Z. Hou, B. Hu, C. Sui, and J. Han, “Kinetostatic analysis of a novel 6-DoF 3UPS parallel manipulator with multi-fingers,” Mechanism and Machine Theory, vol. 78, pp. 36–50, 2014.
[22]
I. A. Bonev and C. M. Gosselin, “Geometric algorithms for the computation of the constant-orientation workspace and singularity surfaces of a special 6-RUS parallel manipulator,” in Proceedings of the ASME International Conference on Design Engineering Technical, Computers and Information in Engineering, vol. 10, pp. 1–10, ASME, Montreal, Canada, 2002.
[23]
G. Cheng, J. Yu, X. Yuan, Y. Pang, and P. Xu, “Study on workspace optimization of 3SPS+1PS parallel hip joint simulator,” Journal of Mechanical Engineering, vol. 49, no. 23, pp. 88–95, 2013.
[24]
Z. Huang, Y. S. Zhao, and T. S. Zhao, Advanced Spatial Mechanism, Higher Education Press, Beijing, China, 2006.
