Trajectory tracking with collision avoidance for a parallel robot with flexible links

Publikationstyp
Journal Article
Date Issued
2021-06
Sprache
English
Author(s)
Morlock, Merlin 
Bajrami, Valmir  
Seifried, Robert  orcid-logo
Institut
Mechanik und Meerestechnik M-13  
TORE-URI
http://hdl.handle.net/11420/9257
Journal
Control engineering practice  
Volume
111
Article Number
104788
Citation
Control Engineering Practice 111: 104788 (2021-06)
Publisher DOI
10.1016/j.conengprac.2021.104788
Scopus ID
2-s2.0-85103694784
End-effector trajectory tracking of a highly flexible three-link parallel robot is combined with collision avoidance in real-time. Typical real-time collision avoidance algorithms issue commands on actuator level which can cause large oscillations within flexible robots. Thus, the needed evasive motion at the points which are about to collide is used to adapt the desired end-effector trajectory of the underactuated system, even for actuator limits and points other than the end-effector. In contrast to existing real-time collision avoidance concepts, which are essentially completely based on rigid models, a dynamic flexible model inversion is then used for tracking. Thereby, output redefinition leads to a minimum phase system. The presented computationally efficient concepts, being actuator limit and obstacle collision avoidance, use sigmoid functions providing smooth trajectories. The former calculates a braking factor for the end-effector when an actuator approaches its limit. The latter avoids external dynamic obstacles based on repulsive vectors. Experiments validate both concepts with a flexible model inversion which clearly outperforms the classical rigid body approach.
Subjects
Collision avoidance
Flexible robot
Parallel robot
Underactuated robot