H4 parallel robot: modeling, design and preliminary experiments

This paper first recalls the concept of H4 parallel mechanism, and the kinematic models necessary for real-time control are derived. A simple and efficient control system based on a combination of Windows NT and RTX is used to demonstrate its performances. Results prove the efficiency of H4 serving as a high-speed pick-and-place robot.

1. Introduction

In the late 80's, after the first ideas of parallel mechanisms proposed by Gough [1] or Stewart [2], Clavel proposed the famous Delta structure [3] as a base for a “family” of parallel machines dedicated to high-speed applications. As far as industrial use is concerned the Delta robot is definitely a success, and this is not so common among the large number of different structures proposed by Academic researchers in the last 20 years. Indeed, only the so-called “hexapod” built with 6 U-P-S chains in parallel (U-P-S: Universal-Prismatic-Spherical) has been also used intensively in industry (see [4] and [5] for an extensive coverage of this issue). This may be seen as a result of, on one hand, the exceptional simplicity of the Delta 3-dof solution, and on the other hand, the enormous research effort dedicated to the so-called “hexapod”.