Integration of Reactive, Torque-Based Self-Collision Avoidance Into a Task Hierarchy

Reactively dealing with self-collisions is an important requirement on multidegree-of-freedom robots in unstructured and dynamic environments. Classical methods to integrate respective algorithms into task hierarchies cause substantial problems: Either these unilateral safety constraints are permane...

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Bibliographic Details
Published in:IEEE transactions on robotics 2012-12, Vol.28 (6), p.1278-1293
Main Authors: Dietrich, A., Wimbock, T., Albu-Schaffer, A., Hirzinger, G.
Format: Article
Language:English
Subjects:
Algorithm design and analysis
Algorithms
Applied sciences
Collision avoidance
Collisions
Computer science
control theory
systems
Control system synthesis
Control systems
Control theory. Systems
Damping
Exact sciences and technology
Force control
Hierarchies
Humanoid robots
Redundancy
redundant robots
Robotics
Robots
self-collision avoidance
task hierarchy
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Summary:Reactively dealing with self-collisions is an important requirement on multidegree-of-freedom robots in unstructured and dynamic environments. Classical methods to integrate respective algorithms into task hierarchies cause substantial problems: Either these unilateral safety constraints are permanently active, unnecessarily locking DOF for other tasks, or they get activated online and result in a discontinuous control law. We propose a new, reactive self-collision avoidance algorithm for highly complex robotic systems with a large number of DOF. In particular, configuration-dependent damping is imposed to dissipate undesired kinetic energy in a well-directed manner. Moreover, we merge the algorithm with a novel method to incorporate these unilateral constraints into a dynamic task hierarchy. Our approach both allows us to specifically limit the force/torque derivative to comply with physical constraints of the real robot and to prevent discontinuities in the control law while activating/deactivating the constraints. No redundancy is wasted. No comparable algorithms have been developed and implemented on a torque-controlled robot with such a level of complexity so far. The implementation of our generic solution on the multi-DOF humanoid Justin clearly validates the performance and demonstrates the real-time applicability of our synthetic approach. The proposed method can be used to contribute to whole-body controllers.
ISSN:1552-3098
1941-0468
DOI:10.1109/TRO.2012.2208667