Morelli, Stefano
(2022)

*Optimal pose selection for the calibration of an overconstrained Cable-Driven Parallel Robot.*
[Laurea magistrale], Università di Bologna, Corso di Studio in

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## Abstract

In this project an optimal pose selection method for the calibration of an overconstrained
Cable-Driven Parallel robot is presented. This manipulator belongs to a subcategory
of parallel robots, where the classic rigid "legs" are replaced by cables. Cables
are flexible elements that bring advantages and disadvantages to the robot modeling.
For this reason, there are many open research issues, and the calibration of geometric
parameters is one of them. The identification of the geometry of a robot, in particular,
is usually called Kinematic Calibration. Many methods have been proposed in the past
years for the solution of the latter problem. Although these methods are based on calibration
using different kinematic models, when the robot’s geometry becomes more
complex, their robustness and reliability decrease. This fact makes the selection of
the calibration poses more complicated. The position and the orientation of the endeffector
in the workspace become important in terms of selection. Thus, in general,
it is necessary to evaluate the robustness of the chosen calibration method, by means,
for example, of a parameter such as the observability index. In fact, it is known from the
theory, that the maximization of the above mentioned index identifies the best choice
of calibration poses, and consequently, using this pose set may improve the calibration
process.
The objective of this thesis is to analyze optimization algorithms which aim to calculate
an optimal choice of poses both in quantitative and qualitative terms. Quantitatively,
because it is of fundamental importance to understand how many poses are
needed. Not necessarily a greater number of poses leads to a better result. Qualitatively,
because it is useful to understand if the selected combination of poses actually
gives additional information in the process of the identification of the parameters.

Abstract

In this project an optimal pose selection method for the calibration of an overconstrained
Cable-Driven Parallel robot is presented. This manipulator belongs to a subcategory
of parallel robots, where the classic rigid "legs" are replaced by cables. Cables
are flexible elements that bring advantages and disadvantages to the robot modeling.
For this reason, there are many open research issues, and the calibration of geometric
parameters is one of them. The identification of the geometry of a robot, in particular,
is usually called Kinematic Calibration. Many methods have been proposed in the past
years for the solution of the latter problem. Although these methods are based on calibration
using different kinematic models, when the robot’s geometry becomes more
complex, their robustness and reliability decrease. This fact makes the selection of
the calibration poses more complicated. The position and the orientation of the endeffector
in the workspace become important in terms of selection. Thus, in general,
it is necessary to evaluate the robustness of the chosen calibration method, by means,
for example, of a parameter such as the observability index. In fact, it is known from the
theory, that the maximization of the above mentioned index identifies the best choice
of calibration poses, and consequently, using this pose set may improve the calibration
process.
The objective of this thesis is to analyze optimization algorithms which aim to calculate
an optimal choice of poses both in quantitative and qualitative terms. Quantitatively,
because it is of fundamental importance to understand how many poses are
needed. Not necessarily a greater number of poses leads to a better result. Qualitatively,
because it is useful to understand if the selected combination of poses actually
gives additional information in the process of the identification of the parameters.

Tipologia del documento

Tesi di laurea
(Laurea magistrale)

Autore della tesi

Morelli, Stefano

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Ordinamento Cds

DM270

Parole chiave

Cable-Driven Parallel Robot,calibration,RMSE,Observability Index,Optimal Pose

Data di discussione della Tesi

23 Marzo 2022

URI

## Altri metadati

Tipologia del documento

Tesi di laurea
(NON SPECIFICATO)

Autore della tesi

Morelli, Stefano

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Ordinamento Cds

DM270

Parole chiave

Cable-Driven Parallel Robot,calibration,RMSE,Observability Index,Optimal Pose

Data di discussione della Tesi

23 Marzo 2022

URI

Gestione del documento: