Zoffoli, Filippo
(2022)

*Feedback control of underactuated cable-driven parallel robots.*
[Laurea magistrale], Università di Bologna, Corso di Studio in

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## Abstract

In this work an Underactuated Cable-Driven Parallel Robot (UACDPR) that operates in the three dimensional Euclidean space is considered. The End-Effector has
6 degrees of freedom and is actuated by 4 cables, therefore from a mechanical point
of view the robot is defined underconstrained. However, considering only three controlled pose variables, the degree of redundancy for the control theory can be considered one. The aim of this thesis is to design a feedback controller for a point-to-point
motion that satisfies the transient requirements, and is capable of reducing oscillations
that derive from the reduced number of constraints. A force control is chosen for the
positioning of the End-Effector, and error with respect to the reference is computed
through data measure of several sensors (load cells, encoders and inclinometers) such
as cable lengths, tension and orientation of the platform. In order to express the relation between pose and cable tension, the inverse model is derived from the kinematic
and dynamic model of the parallel robot. The intrinsic non-linear nature of UACDPRs systems introduces an additional level of complexity in the development of the
controller, as a result the control law is composed by a partial feedback linearization,
and damping injection to reduce orientation instability. The fourth cable allows to satisfy a further tension distribution constraint, ensuring positive tension during all the
instants of motion. Then simulations with different initial conditions are presented
in order to optimize control parameters, and lastly an experimental validation of the
model is carried out, the results are analysed and limits of the presented approach are
defined.

Abstract

In this work an Underactuated Cable-Driven Parallel Robot (UACDPR) that operates in the three dimensional Euclidean space is considered. The End-Effector has
6 degrees of freedom and is actuated by 4 cables, therefore from a mechanical point
of view the robot is defined underconstrained. However, considering only three controlled pose variables, the degree of redundancy for the control theory can be considered one. The aim of this thesis is to design a feedback controller for a point-to-point
motion that satisfies the transient requirements, and is capable of reducing oscillations
that derive from the reduced number of constraints. A force control is chosen for the
positioning of the End-Effector, and error with respect to the reference is computed
through data measure of several sensors (load cells, encoders and inclinometers) such
as cable lengths, tension and orientation of the platform. In order to express the relation between pose and cable tension, the inverse model is derived from the kinematic
and dynamic model of the parallel robot. The intrinsic non-linear nature of UACDPRs systems introduces an additional level of complexity in the development of the
controller, as a result the control law is composed by a partial feedback linearization,
and damping injection to reduce orientation instability. The fourth cable allows to satisfy a further tension distribution constraint, ensuring positive tension during all the
instants of motion. Then simulations with different initial conditions are presented
in order to optimize control parameters, and lastly an experimental validation of the
model is carried out, the results are analysed and limits of the presented approach are
defined.

Tipologia del documento

Tesi di laurea
(Laurea magistrale)

Autore della tesi

Zoffoli, Filippo

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Indirizzo

CURRICULUM MECCANICA DELL’AUTOMAZIONE E ROBOTICA

Ordinamento Cds

DM270

Parole chiave

underactuated, cable, driven, parallel, robot, feedback, control, point-to-point, motion, regulator, mechanics, machines, automation, industry, wires, manipulator

Data di discussione della Tesi

7 Ottobre 2022

URI

## Altri metadati

Tipologia del documento

Tesi di laurea
(NON SPECIFICATO)

Autore della tesi

Zoffoli, Filippo

Relatore della tesi

Correlatore della tesi

Scuola

Corso di studio

Indirizzo

CURRICULUM MECCANICA DELL’AUTOMAZIONE E ROBOTICA

Ordinamento Cds

DM270

Parole chiave

underactuated, cable, driven, parallel, robot, feedback, control, point-to-point, motion, regulator, mechanics, machines, automation, industry, wires, manipulator

Data di discussione della Tesi

7 Ottobre 2022

URI

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