Document Detail

Winching up heavy loads with a compliant arm: a new local joint controller.
MedLine Citation:
PMID:  18414891     Owner:  NLM     Status:  MEDLINE    
A closed kinematic chain, like an arm that operates a crank, has a constrained movement space. A meaningful movement of the chain's endpoint is only possible along the free movement directions which are given implicitly by the contour of the object that confines the movement of the chain. Many technical solutions for such a movement task, in particular those used in robotics, use central controllers and force-torque sensors in the arm's wrist or a leg's ankle to construct a coordinate system (task frame formalism) at the local point of contact the axes of which coincide with the free and constrained movement directions. Motivated by examples from biology, we introduce a new control system that solves a constrained movement task. The control system is inspired by the control architecture that is found in stick insects like Carausius morosus. It consists of decentral joint controllers that work on elastic joints (compliant manipulator). The decentral controllers are based on local positive velocity feedback (LPVF). It has been shown earlier that LPVF enables contour following of a limb in a compliant motion task without a central controller. In this paper we extend LPVF in such a way that it is even able to follow a contour if a considerable counter force drags the limb away along the contour in a direction opposite to the desired. The controller extension is based on the measurement of the local mechanical power generated in the elastic joint and is called power-controlled relaxation LPVF. The new control approach has the following advantages. First, it still uses local joint controllers without knowledge of the kinematics. Second, it does not need a force or torque measurement at the end of the limb. In this paper we test power-controlled relaxation LPVF on a crank turning task in which a weight has to be winched up by a two-joint compliant manipulator.
Axel Schneider; Holk Cruse; Josef Schmitz
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-04-15
Journal Detail:
Title:  Biological cybernetics     Volume:  98     ISSN:  0340-1200     ISO Abbreviation:  Biol Cybern     Publication Date:  2008 May 
Date Detail:
Created Date:  2008-04-18     Completed Date:  2008-07-08     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7502533     Medline TA:  Biol Cybern     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  413-26     Citation Subset:  IM    
Mechatronics of Biomimetic Actuators, Faculty of Technology, University of Bielefeld, P.O. Box 10 01 31, 33501 Bielefeld, Germany.
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MeSH Terms
Computer Simulation
Equipment Design
Extremities / physiology*
Joints / physiology*
Models, Biological*
Weight-Bearing / physiology*

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