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Machine Theory
Mechanism and Machine Theory 43 (2008) 984–995
ate/mechmt
A type synthesis method for hybrid robot structures
Alexandre Campos *, Christoph Budde, Ju¨rgen Hesselbach
Institute of Machine Tools and Production Technology, Technical University of Braunschweig, Langer Kamp 19 B,
D-38106 Braunschweig, Germany
Received 11 May 2006; received in revised form 30 April 2007; accepted 11 July 2007
Available online 24 October 2007
Abstract
In this paper a new methodology to synthesize hybrid robots as a whole structure is presented. The method is based on
Assur groups as the simplest basic blocks to build kinematic chains. Criterions like symmetry and low inertia are consid-
ered in the design process. The method results in hybrid robots whose structures are as simple as possible. The closed
chains of some of them are known parallel structures, however one of them is a new hybrid structure.
Ó 2007 Published by Elsevier Ltd.
Keywords: Hybrid robot; Synthesis method; Assur groups
1. Introduction
Hybrid bine the advantages of parallel and serial chains, . stiffness and manipulability [1–
6]. Most robots designed are either built up of serial or in-parallel connected kinematic chains. Serial robots
consist of a series of active joints connecting the base to the end effector and feature large workspaces and high
dexterity but they suffer from lack of stiffness and from relatively large positioning errors due to their canti-
lever type of kinematic arrangement. On the other hand, parallel manipulators consist of a set of parallel legs
each with active and passive joints required to maintain the system mobility and controllability. They connect
the base to the moving platform resulting in structures able to achieve high stiffness and high force-to-weight
ratio. However, parallel manipulators are known for a restricted workspace and low dexterity.
Aiming to merge the advantages of serial and parallel ro