Interaction Forces and Internal Loads in Parallel Manipulators with Actuation Redundancy

2026-04-29

AI Summary

This study addresses the ambiguity and inaccuracies in existing definitions of interaction forces and internal loads in redundantly actuated parallel mechanisms, which have led to erroneous force analyses and control deviations. To resolve this issue, the work rigorously clarifies these two concepts and proposes a unified dynamic modeling framework based on null-space torque decomposition and joint torque vector synthesis. The resulting formulation provides a clear and unambiguous analytical foundation specifically tailored for such mechanisms. Validation through representative case studies demonstrates that the proposed method effectively corrects erroneous results reported in the literature and significantly enhances force control accuracy in both balancing and manipulation tasks for redundantly actuated parallel mechanisms.

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.

Problem

• parallel manipulators
• actuation redundancy
• interaction forces
• internal loads
• null-space wrench

Innovation

• actuation redundancy
• parallel manipulators
• interaction forces
• internal loads
• null-space wrench