Share Email Print

Proceedings Paper

A self-adjusting negative feedback joint controller for legs standing on moving substrates of unknown compliance
Author(s): Axel Schneider; Holk Cruse; Björn Fischer; Josef Schmitz
Format Member Price Non-Member Price
PDF $17.00 $21.00

Paper Abstract

Some recent robot controllers for hexapod walking have been developed based on investigations of stick insects. These animals live in an unpredictable environment that consists of twigs and leaves. Supports like twigs, leaves and branches induce a considerable amount of movement to the legs and their elastic joints. Earlier studies proposed negative feedback PD-controllers to regulate the angles of the knee joints to handle this situation. Recent studies suggest that the behaviour of the joint controller depends on the compliance of the substrate the insect is standing on. On highly elastic substrates (e.g. leaves) the joint controller exhibits an I-characteristic. Deviations from the original position are compensated completely. On moderately elastic substrates (e.g. twigs) the joint controller comprises a P-characteristic. The leg attains a resting position that differs from the original position through application of a specific compensation force. On stiff substrates the knee joint seems to be controlled by a D-controller. If the leg endpoint is forced away from the original position by an external disturbance (e.g. a moving branch), the controller compensates this deviation by activation of the according muscle which results in a counter force. After some time the controller seems to "give up." The force decreases to zero. To model these results, we propose a self-adjusting joint controller that changes its own setpoint in dependance of the substrate stiffness. The substrate stiffness is determined by means of a correlator circuit that compares (superimposed) movement commands with the actual responses of the leg joint. The new controller can be used for the control of legged robots.

Paper Details

Date Published: 22 May 2007
PDF: 11 pages
Proc. SPIE 6592, Bioengineered and Bioinspired Systems III, 65920M (22 May 2007); doi: 10.1117/12.721723
Show Author Affiliations
Axel Schneider, Univ. of Bielefeld (Germany)
Holk Cruse, Univ. of Bielefeld (Germany)
Björn Fischer, Univ. of Bielefeld (Germany)
Josef Schmitz, Univ. of Bielefeld (Germany)

Published in SPIE Proceedings Vol. 6592:
Bioengineered and Bioinspired Systems III
Paolo Arena; Ángel Rodríguez-Vázquez; Gustavo Liñán-Cembrano, Editor(s)

© SPIE. Terms of Use
Back to Top