Parallel Robots with Unconventional Joints to Achieve Under-Actuation and Reconfigurability

150 Pages·2016·6.79 MB·English

by  Patrick Grosch

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the name of the author
UNIVERSITAT POLITÈCNICA DE CATALUNYA
Doctoral Programme
AUTOMATIC CONTROL, ROBOTICS AND COMPUTER VISION
Ph.D. Thesis
P R U
ARALLEL OBOTS WITH NCONVENTIONAL
J A U -A
OINTS TO CHIEVE NDER CTUATION AND
R
ECONFIGURABILITY
Patrick Grosch
Advisor:
Federico Thomas
June 2016

Parallel Robots with Unconventional Joints
to Achieve Under-Actuation and Reconfigurability
by Patrick Grosch
A thesis submitted to the Universitat Politècnica de Catalunya for the degree of Doctor of
Philosophy
Doctoral Programme:
Automatic Control, Robotics and Computer Vision
This thesis has been completed at:
Institut de Robòtica i Informàtica Industrial, CSIC-UPC
Advisor:
Federico Thomas
Dissertation Committee:
Prof.
Prof.
Prof.
Prof.
Prof.
Thelatestversionofthisdocumentisavailableathttp://www.iri.upc.edu/people/grosch.

PARALLEL ROBOTS WITH UNCONVENTIONAL JOINTS TO ACHIEVE
UNDER-ACTUATION AND RECONFIGURABILITY
Patrick Grosch
Abstract
The aim of the thesis is to define, analyze, and verify through simulations and practical im-
plementations, parallel robots with unconventional joints that allow them to be under-actuated
and/or reconfigurable. The new designs will be derived from the:
1. 6SPS robot (alternatively 6UPS or 6SPU, depending on the implementation) when
considering the spatial case (i.e., robots with 3 degrees of freedom of rotation and 3
degrees of freedom of translation).
2. S-3SPS robot (alternatively S-3UPS or S-3SPU, depending on the implementation)
when considering spherical robots (i.e., robots with 3 degrees of freedom of rotation).
In both cases, we will see how, through certain geometric transformations, some of the
standardjointscanbereplacedbylockableornon-holonomicjoints. Thesesubstitutionspermit
reducing the number of legs (and hence the number of actuators needed to control the robot),
withoutlosingtherobot’sabilitytobringitsmobileplatformtoanypositionandorientation(in
caseofaspatialrobot),ortoanyorientation(incaseofasphericalrobot),withinitsworkspace.
The expected benefit of these new designs is to obtain parallel robots with:
1. largerworkingspacesbecausethepossibilityofcollisionsbetweenlegsisreduced,andthe
number of joints (with their intrinsic range limitations) is also reduced;
2. lower weight because the number of actuators and joints is reduced; and
3. lower cost because the number of actuators and controllers is also reduced.
The elimination of an actuator and the introduction of a motion constraint reduces in one the
dimension of the space of allowed velocities attainable from a given configuration. As a result,
it will be necessary, in general, to plan maneuvers to reach the desired configuration for the
moving platform. Therefore, the obtained robots will only be suitable for applications where
accuracy is required in the final position and a certain margin of error is acceptable in the
generated trajectories.
i

Acknowledgements
I would like to thank my supervisor, Federico Thomas, for their valuable guidance and constant
support.
I am grateful and indebted to Raffaele Di Gregorio (University of Ferrara, Italy) who wel-
comed me to work with him during a fruitful stay in Ferrara.
My gratitude also goes to Krzysztof Tchon´ and Janusz Jakubiakand (Wroclaw University of
Technology, Poland).
I very much appreciate the advice, assistance and encouragement that I received from my
colleagues at IRI.
Finally, I would also like to acknowledge the support of the Spanish Ministry of Education and
Science, under the I+D project DPI2007-60858, Explora and by Italian MIUR funds during my
visit to the University of Ferrara.
iii

Contents
Abstract i
Acknowledgements iii
List of Figures ix
List of Tables xiii
Nomenclature xv
1 Introduction 1
1.1 Motivation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Reconfigurable robots with lockable joints . . . . . . . . . . . . . . . . . . 5
1.1.2 Sub-actuated robots with non-holonomic joints . . . . . . . . . . . . . . . 7
1.2 Previous work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.1 Precursors of robots with lockable joints . . . . . . . . . . . . . . . . . . . 8
1.2.2 Precursors of robots with non-holonomic joints . . . . . . . . . . . . . . . 10
1.3 Organization of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2 Full-mobility with only one continuous actuator 17
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Manipulator architecture and operation . . . . . . . . . . . . . . . . . . . . . . . 19
2.3 Kinetostatics and constraints on the T-path . . . . . . . . . . . . . . . . . . . . . . 21
2.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3 Parallel robots with lockable revolute joints 25
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2 Kinematics of the 2RPS-2UPS parallel robot . . . . . . . . . . . . . . . . . . . . 27
3.2.1 Position analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.2.2 Singularities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.3 Maneuvers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.4 Path planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.4.1 Generating the roadmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.4.2 Finding a path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.5 Hardware implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.6 Software implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4 Parallel robots with non-holonomic joints 41
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.2 Generation of under-actuated manipulators . . . . . . . . . . . . . . . . . . . . . 42
4.3 Implementation of non-holonomic joints . . . . . . . . . . . . . . . . . . . . . . . 45
4.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
v