The aim of this thesis is the feasibility study of a long-light robotic arm designed with a continuum-kinematic joint and inflatable links. The aim of the manipulator presented is the structural inspection in space applications. In space weight and volume are very relevant cost drivers: the use of inflatables reduces both up to 50%, impacting on the cost of space missions. Despite the use of inflatables has been widely explored during the past decades for high volume functional elements such as such as antennas, solar panels and sails, this technology has never been exploited for a fully-inflatable robotic arm. Following this purpose, a final modular 3-meter-long manipulator, consisted of 3 segment of 1 meter each, was designed and then assembled. In order to work in a microgravity environment, Helium was used as inflating gas of the links, balancing the weight of the structure with the lift force given by the noble gas until achieving the neutral buoyancy condition. At the end, the design and mathematical model were verified testing three prototypes, respectively consisting in one, two and three segments, measuring for each prototype accuracy and repeatability values. Compared with previous examples of long-light robotic arms, the prototype presents a constant and wider movable angle range, which is independent on the length of the arm, and a reliable buoyancy condition both achieved thanks to the modular design. Moreover, modularity allows to increase the length of the manipulator without changing the design of the structural elements from which it is composed, besides it guarantees ease of maintenance and replacement of spare parts. The experimental tests performed on the prototype validate the theoretical designing steps of the robot and confirms the potential of the use of inflatables structures as robotic arms for a structural inspection employment. Finally a non-parametric compensation was designed, implemented and experimentally measured with the aim of improving the accuracy of the robot.
Scopo di questa tesi è lo studio di fattibilità di un braccio robotico lungo e leggero, progettato con dei giunti a cinematica continua e link gonfiabili. Il manipolatore in studio è progettato per compiere ispezioni strutturali in applicazione spaziali. Nell’ambiente spaziale, peso e volume sono due importanti indici di costo: l’uso di strutture gonfiabili riduce entrambi fino al 50% impattando sui costi delle missioni spaziali. Nonostante l’uso di strutture gonfiabili sia stato ampiamente sperimentato durante le decadi precedenti per elementi funzionali di grande volume come antenne, pannelli e vele solari, questa tecnologia non è ancora stata pienamente sfruttata per l’uso di un braccio robotico completamente gonfiabile. A tale scopo, un manipolatore modulare lungo tre metri, costituito da tre segmenti lunghi un metro ciascuno, è stato progettato e assemblato. Per lavorare in condizioni di micro-gravità, l’elio è stato usato come gas riempitivo dei link, bilanciando il peso della struttura con la forza di galleggiamento data dal gas nobile fino al raggiungimento di una condizione di neutralità. Infine, il design e il modello matematico sono stati verificati testando tre prototipi costituiti rispettivamente da uno, due e tre segmenti, ricavando per ogni prototipo i valori di ripetibilità e accuratezza. Rispetto ai precedenti esempi di lunghi bracci robotici ultra-leggeri, il prototipo studiato presenta per ogni giunto un angolo di movimento maggiore, costante nel range, indipendente dalla lunghezza del braccio stesso e un galleggiamento neutrale stabile garantiti dalla modularità del design. Inoltre, il progetto modulare del braccio permette di aumentare la lunghezza dello stesso senza cambiare il design degli elementi strutturali e garantisce una semplice manutenzione e reperibilità delle parti di ricambio. I test sperimentali effettuati sul prototipo avvalorano le fasi teoriche di progettazione del robot e confermano il potenziale dell'uso di strutture gonfiabili come bracci robotici per un impiego di ispezione strutturale. Infine un algoritmo di compensazione non parametrica è stato progettato, implementato e misurato sperimentalmente con lo scopo di migliorare l’accuratezza della macchina.
Feasibility study of a continuum-joint robotic arm with inflatable links for structural inspection in space applications
GIANI, ELISA ROSALINDA;CEDERLE, MARCO
2017/2018
Abstract
The aim of this thesis is the feasibility study of a long-light robotic arm designed with a continuum-kinematic joint and inflatable links. The aim of the manipulator presented is the structural inspection in space applications. In space weight and volume are very relevant cost drivers: the use of inflatables reduces both up to 50%, impacting on the cost of space missions. Despite the use of inflatables has been widely explored during the past decades for high volume functional elements such as such as antennas, solar panels and sails, this technology has never been exploited for a fully-inflatable robotic arm. Following this purpose, a final modular 3-meter-long manipulator, consisted of 3 segment of 1 meter each, was designed and then assembled. In order to work in a microgravity environment, Helium was used as inflating gas of the links, balancing the weight of the structure with the lift force given by the noble gas until achieving the neutral buoyancy condition. At the end, the design and mathematical model were verified testing three prototypes, respectively consisting in one, two and three segments, measuring for each prototype accuracy and repeatability values. Compared with previous examples of long-light robotic arms, the prototype presents a constant and wider movable angle range, which is independent on the length of the arm, and a reliable buoyancy condition both achieved thanks to the modular design. Moreover, modularity allows to increase the length of the manipulator without changing the design of the structural elements from which it is composed, besides it guarantees ease of maintenance and replacement of spare parts. The experimental tests performed on the prototype validate the theoretical designing steps of the robot and confirms the potential of the use of inflatables structures as robotic arms for a structural inspection employment. Finally a non-parametric compensation was designed, implemented and experimentally measured with the aim of improving the accuracy of the robot.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/142812