Dynamic analysis and control of a stewart platform manipulator

TLDR

The Stewart platform is a six‑axis parallel robot with a force‑to‑weight ratio and positioning accuracy far exceeding conventional serial‑link arms, while its stiffness and accuracy rival machine tools and its workspace dexterity matches conventional manipulators. This study investigates the dynamic equations of the Stewart platform and aims to transform the milling station into a semi‑autonomous robotic tool that requires operator interaction yet possesses its own intelligence. The authors derive the platform dynamics in a step‑by‑step algorithm similar to Nguyen and Pooran, design a stiffness‑control scheme for milling, and discuss path‑planning that accounts for singularities and task requirements to enable semi‑autonomous operation. The derived equations yield compact coefficient expressions that provide insight into the platform’s dynamics, are valuable for control design, and facilitate natural interfacing with part delivery and higher‑level tasks.

Abstract

Abstract The Stewart platform is a six‐axis parallel robot manipulator with a force‐to‐weight ratio and positioning accuracy far exceeding that of a conventional serial‐link arm. Its stiffness and accuracy approach that of a machine tool yet its workspace dexterity approaches that of a conventional manipulator. In this article, we study the dynamic equations of the Stewart platform manipulator. Our derivation is closed to that of Nguyen and Pooran because the dynamics are not explicitly given but are in a step‐by‐step algorithm. However, we give some insight into the structure and properties of these equations: We obtain compact expressions of some coefficients. These expressions should be interesting from a control point of view. A stiffness control scheme is designed for milling application. Some path‐planning notions are discussed that take into account singularity positions and the required task. The objective is to make the milling station into a semiautonomous robotic tool needing some operator interaction but having some intelligence of its own. It should interface naturally with part delivery and other higher‐level tasks.