Interaction Forces and Internal Loads in Parallel Manipulators with Actuation Redundancy

TL;DR

This paper analyzes null-space wrench components in redundant parallel manipulators, clarifies their definitions, and introduces explicit methods for synthesizing joint torques, validated through a case study.

Contribution

It identifies gaps in existing literature, clarifies the concepts of interaction forces and internal loads, and proposes new synthesis methods for joint torques in redundant systems.

Findings

Resolved ambiguities in defining interaction forces and internal loads.

Provided explicit methods for synthesizing joint torque vectors.

Validated methods with a case study correcting previous errors.

Abstract

This paper discusses null-space wrench components in parallel manipulators. We examine the adaptation of the two most common characterizations of these components in grasp-like systems, namely, interaction forces and internal loads, to parallel manipulators with actuation redundancy. We identify critical oversights in the existing literature on the subject, resolve ambiguities related to the definitions of interaction forces and internal loads, and provide explicit methods for synthesizing equilibrating and manipulating joint torque vectors. A case study is also provided to justify the validity of our novel methods and correct erroneous results reported in the literature.