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Self-protective motion planning for mobile manipulators in a dynamic door-closing workspace

Chuande Liu (Southeast University, Nanjing, China)
Bingtuan Gao (Southeast University, Nanjing, China)
Chuang Yu (ENSTA ParisTech, Palaiseau, France)
Adriana Tapus (ENSTA ParisTech, Palaiseau, France)

Industrial Robot

ISSN: 0143-991x

Article publication date: 14 June 2021

Issue publication date: 16 November 2021




Many work conditions require manipulators to open cabinet doors and then gain access to the desired workspace. However, after opening, the unlocked doors can easily close, interrupt a task and potentially break the operating end-effectors. This paper aims to address a manipulator's behavior planning problem for responding to a dynamic workspace released by door opening.


A dynamic model of the restricted workspace released by an unlocked door is established. As a whole system to treat, the interactions between the workspace and robot are analyzed by using a partially observable Markov decision process. A self-protective policy decision executed as a belief tree is proposed. To respond to the policy, this study has designed three types of actions: stay on guard in the workspace, using an elbow joint to defense the door and linear escape out of the workspace for self-protection by observing collision risk levels to trigger them. Finally, this study proposes self-protective motion controllers based on risk time optimization to act to the planned actions.


The elbow defense could balance robotic safety and work efficiency by interrupting the end-effector's work and using the elbow joint to prevent the door-closing in an active collision way. Compared with the stay and escape action, the advantage of the elbow defense is having a predictable performance to quick callback the interrupted work after the risk was relieved.


This work provides guidance for the safe operation of a class of robot operations and the upgrade of motion planning.



Liu, C., Gao, B., Yu, C. and Tapus, A. (2021), "Self-protective motion planning for mobile manipulators in a dynamic door-closing workspace", Industrial Robot, Vol. 48 No. 6, pp. 803-811.



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