Emulation of biological motor primitives in an artificial system: the generation of static force fields

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We have used observations of posture and movements in biological limbs to derive a controller for an artificial mechanism. The controller architecture emulates some of the known relations between spinal cord circuitry and the musculoskeletal system of vertebrates and, specifically, of the rat. This work relates to recent experiments suggesting that the neural circuitry of the spinal cord may be partitioned into a small set of functional modules. Activation of these modules, each connected to a set of limb muscles, resulted in force fields that have been measured at the endpoint of a limb. These force fields map each position of the foot into a corresponding static force vector. The force fields have been found to converge toward equilibrium positions located inside the leg's workspace. The experimental observation that vector fields induced by multiple stimulations add vectorially, suggested that convergent force fields form a system of building blocks (or 'primitives') for the generation of stable postures and movements. To emulate this biological mechanism in the control of an artificial two-joint limb, we established relationships among three hierarchical levels - spinal modules, muscles, and actuators - by deriving the mappings among the respective output fields. These mappings are used in combination with an inverse model of the actuators to calculate the actuator commands that generate a desired force field. We tested the ability of this control system to reproduce the force fields generated by the leg muscles of the rat and a set of force fields with significant geometrical features. Our results show that we can successfully and reliably transfer to our artificial system the features of muscle force fields. In addition, we exploited the same principle of vector summation observed in the biological system to combine these muscle fields into a variety of force field patterns, including the gradients of Gaussian potentials and locally parallel fields. We consider this a first step in the generation of a biomorphic motor control system. This work is supported by ONR grant N00014-95-1-0571 and NIH grant MH48185.

Original languageEnglish (US)
Title of host publicationAmerican Society of Mechanical Engineers, Dynamic Systems and Control Division (Publication) DSC
PublisherASME
Pages897-905
Number of pages9
Volume67
ISBN (Print)0791816346
StatePublished - Dec 1 1999
EventDynamic Systems and Control Division - 1999 (The ASME International Mechanical Engineering Congress and Exposition) - Nashville, TN, USA
Duration: Nov 14 1999Nov 19 1999

Other

OtherDynamic Systems and Control Division - 1999 (The ASME International Mechanical Engineering Congress and Exposition)
CityNashville, TN, USA
Period11/14/9911/19/99

ASJC Scopus subject areas

  • Software
  • Mechanical Engineering

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