23 research outputs found
A method to improve prosthesis leg design based on pressure analysis at the socket-residual limb interface
No full textThis paper presents a methodology and tools to improve the design of lower limb prosthesis through the measurement of pressure analysis at the interface residual limb-socket. The steps of the methodology and the design tools are presented using a case study focused on a transfemoral (amputation above knee) male amputee. The experimental setup based on F-Socket Tekscan pressure system is described as well the results of some static loading tests. Pressure data are visualized with a colour pressure map over the 3D model of the residual limb acquired using an optical low cost scanner, based on MS Kinect. Previous methodology is useful to evaluate a physical prototype; in order to improve also conceptual design, the Finite Element (FE) Analysis has been carried and results reached so far have been compared with experimental tests. Pressure distributions are comparable, even if some discrepancies have been highlighted due to sensors placements and implemented FE model. Future developments have been identified in order to improve the accuracy of the numerical simulations
Current and Future Manufacturing of Chest Orthoses, Considering the Case of Osteogenesis Imperfecta
No full textDesign and testing of (A)MICO: a multimodal feedback system to facilitate the interaction between cobot and human operator
No full textThe present work describes the design, development and testing of a multimodal feedback system, named (A)MICO, with visual and acoustic feedback designed to facilitate the interaction of workers with collaborative robots (cobots) in production lines. The feedback is designed to make the human operator more aware of the cobot’s ongoing and future activities, and therefore gain more control over the situation. The ultimate goal is to obtain a new intuitive mode for transferring information through the combination of lights and sounds, not only to facilitate the flow of communication from the cobot to the operator, but also to make the interaction more accessible to neurodivergent groups, such as people with autism spectrum disorders. The design process focused on the evaluation of the human–robot interaction to select the situations where additional information is needed, and which is the best way to transfer messages as intuitively as possible. Potential end-users were actively involved during all stages of the design and development process. Five volunteers with high functioning autism participated in a preliminary co-design to identify the issues related to the interaction with the cobot and the logic of the multimodal signals. Then, to assess the system’s adaptability to several needs and the level of usability in providing information, validation tests were carried out involving a wider group of participants with ASD. The results suggest that the adoption of a multimodal communication strategy can be useful for making the workplace accessible and improving the well-being of all workers
A Virtual Design Process to Produce Scoliosis Braces by Additive Manufacturing
No full textThe present work aims to present the current virtual design process of scoliosis braces and propose an improvement by considering the internal geometry. Starting from the external scanning it is possible to apply only corrections that do not consider the interaction with the human body. For this reason we propose to embed the 3D model reconstruction of the skeleton of the patient from the medical images. This would bring to a better virtual design process that could help avoiding the current need for a physical positive mold. The final goal of such a change is to pass from the current thermoforming production to the use of additive manufacturing. In the paper, we briefly analyze the choice of the most convenient 3D printing technology and the selection of a proper material that can be comparable to the ones used for thermoforming. Finally, a case study is presented to test the assumptions regarding both the design and manufacturing processes
Innovation in the production process of custom-made scoliosis braces with additive manufacturing
No full textLa tesi presenta un nuovo processo manifatturiero per la produzione di corsetti personalizzati per il trattamento della scoliosi, utilizzando la tecnologia di stampa 3D. La scoliosi è la problematica più comune riguardo la colonna vertebrale ed il trattamento consiste in una combinazione di terapia fisica e utilizzo di corsetti ortopedici, i quali hanno lo scopo di supportare e aiutare il riallineamento della colonna.
La manifattura attuale si basa sulla termoformatura di una lastra polimerica, richiedendo la produzione di uno stampo in positivo che viene poi scartato tra i rifiuti. Inoltre, la produzione è ancora fortemente basata sulle operazioni manuali eseguite dai tecnici ortopedici, riducendo la ripetibilità del processo. Questa tesi propone l’utilizzo della stampa 3D per la produzione del corsetto, tecnica che può migliorare la ripetibilità delle caratteristiche del prodotto. Il processo complessivo andrebbe modificato anche nella fase di modellazione, che può essere completato nell’ambiente virtuale tramite l’utilizzo degli strumenti CAD. Al fine di ottenere un processo stabile, il lavoro è stato organizzato in differenti fasi: acquisizione della geometria esterna del paziente, creazione dei modelli di corsetto e di scheletro, simulazioni numeriche, analisi delle tecnologie di manifattura additiva e valutazione di materiali stampabili.
Innanzitutto, per acquisire il modello della pelle del paziente sono stati comparati diversi scanner 3D, utilizzando sia oggetti di riferimento standard (piano e sfere), richiesti dalle comuni linee guida, sia alcune parti di un manichino, considerate rappresentative delle possibili applicazioni ortopediche. L’analisi ha incluso anche il test di diversi approcci di movimento degli scanner manuali attorno al busto del manichino. Come risultato generale, gli scanner fissi da laboratorio hanno portato a risultati migliori in termini di qualità della ricostruzione, ma l’acquisizione ha richiesto un periodo di tempo molto lungo. Tuttavia, l’applicazione ortopedica richiede una scansione rapida di circa 30 secondi, il che li rende poco pratici. Gli scanner portatili, d’altra parte, possono compiere una ricostruzione più rapida, potendoli spostare attorno al paziente in pochi secondi. I risultati hanno mostrato che Artec Leo e Structure Sensor sono i più appropriati per i centri ortopedici. Artec Leo ha prodotto una maggiore precisione (circa 0.2 mm), che potrebbe essere richiesta per parti molto dettagliate, mentre lo Structure Sensor può essere utilizzato stabilmente per la modellazione dei corsetti ortopedici, con una accuratezza di circa 0.6 mm.
Successivamente, analizzando gli attuali strumenti CAD per scolpire i modelli tassellati, sono stati identificati i problemi nei diversi pacchetti software, che richiederebbero una futura integrazione. La pecca più rilevante è l’assenza di un modello di scheletro 3D che potrebbe essere utilizzato come riferimento visivo nell’ambiente virtuale 3D. I tecnici sono attualmente limitati all’uso delle immagini radiografiche planari (frontale e laterale) per ipotizzare come il corsetto interagirebbe con il corpo del paziente. Per questo motivo, ho sviluppato un modello di scheletro pseudo-parametrico che può essere trasformato secondo queste due proiezioni ed ottenere così un modello approssimativo dello scheletro del singolo paziente, che può essere usato come riferimento quando si scolpisce il tutore, nella sua formulazione alleggerita con pochi poligoni.
Inoltre, è stata sviluppata una formulazione del modello con superfici NURBS che può essere importata nello strumento di simulazione numerica, permettendo di calcolare l’interazione tra il tutore e il corpo del paziente. è stata eseguita una serie di simulazioni semplificate per verificare l’usabilità del modello sviluppato e la possibilità di ottenere una simulazione numerica relativamente veloce per convalidare il modello di corsetto creato durante la fase di progettazione, prima di passare a stamparlo in 3D. Le simulazioni hanno raggiunto la convergenza, mostrando la possibile analisi delle interazioni, ma richiedendo più di un’ora a causa della non linearità del problema di contatto. Una serie di simulazioni complementari sono state eseguite sul caso più semplice di un’ortesi del polso per testare letecniche di Ottimizzazione Topologica, senza però considerare l’interazione con l’anatomia del paziente. L’ortesi di polso è stata vincolata come una trave a sbalzo sostenuta da un carrello e caricata con una forza posizionata all’estremità del palmo della mano. Questa simulazione ha valutato la fattibilità dell’utilizzo dello strumento di Ottimizzazione Topologica per ridurre il peso di un dispositivo ortesico, con una distribuzione del materiale ottimizzata in contrapposizione alle trame puramente estetiche. La massa è stata ridotta di circa il 25% in 6 minuti, tempo circa 10 volte superiore a quello richiesto dalla sola analisi staticostrutturale. Ciò significa che l’applicazione dell’Ottimizzazione Topologica al caso più complesso del corsetto ortopedico con l’interazione di contatto potrebbe portare ad un incremento esponenziale del tempo richiesto.
Per quanto riguarda la produzione additiva, è stata selezionata la tecnologia di stampa da filamento (FFF) per il miglior compromesso in termini di costi, velocità e volume di stampa. Inizialmente sono stati considerati diversi materiali, ma sono stati analizzati nel particolare solo PLA e PETG e confrontati con il materiale termoformato (PP). I risultati migliori sono stati ottenuti con il PETG, sia per le proprietà meccaniche che per l’adesione tra gli strati, verificata con un’analisi SEM. Questo materiale è stato quindi utilizzato per la stampa 3D di un corsetto completo che è stato testato poi con successo con un paziente volontario. Il feedback positivo ha riguardato non solo il paziente ma anche il medico ortopedico e i tecnici coinvolti nell’esperimento.
La conclusione generale della tesi è che il processo è attualmente fattibile in tutte le diverse fasi, anche se al momento devono essere eseguite separatamente utilizzando diversi pacchetti software. Pertanto, è necessaria un’ulteriore integrazione dei vari strumenti al fine di consentire una più semplice attuazione del processo completo nei centri ortopedici.The work presents a new manufacturing process for the production of patient-specific scoliosis braces by using the 3D printing technology. The scoliosis is the most common spine disorder and the treatment consists on a combination of physical therapy and use of back braces, which are used to support and help realigning the spine. The current manufacturing processes are based on thermoforming a plastic plate, requiring the production of a positive mold to be wrapped, which is then discarded as a waste. Moreover, the production is still very dependent on the technicians manual operations reducing the repeatability of the process. This thesis proposes the use of 3D printing for manufacturing the brace, which could improve the repeatability of its characteristics. The production process should be changed also for the sculpting phase, which can be performed in a virtual environment by means of CAD tools. In order to reach a stable process, the work was organized in different steps: acquisition of patient’s 3D skin, creation of brace and skeleton models, numerical simulations, analysis of additive manufacturing technologies and evaluation of materials.
First of all, to acquire the patient’s 3D skin model, different 3D scanners were compared using both standard reference objects (i.e. flat plane and spheres) required by the common guidelines and also manikin parts, representative of the orthopedic application. The investigation included also the test of different motion approaches around the chest of a manikin for the handheld scanners. As a general result, the fixed scanners performed better in terms of reconstruction quality, but the model has to be acquired over a long time period. However, the orthopedic application requires to have a fast scan of about 30 seconds, making them impractical. The handheld scanners, on the other hand, can compute a fast reconstruction by moving around the patient in few seconds. Results showed that Artec Leo and Structure Sensor are the most appropriate for the orthopedic centers.The Artec Leo resulted in higher accuracy (about 0.2 mm), which could be required for very detailed parts, while the Structure Sensor can be stably used for the back brace design, with an accuracy of about 0.6 mm.
Next, analyzing the current CAD tools for sculpting the tessellated models, I identified issues in the different software packages, which would require a future integration. The most relevant gap is the absence of a 3D skeleton model that could be used as a visual reference in the 3D virtual environment. The technicians are currently limited to using bi-planar X-ray images to assume how the brace would interact with the patient’s body. For this reason, I developed a pseudo-parametric skeleton model that could be morphed according to these two projections to obtain an approximated patient-specific skeleton model, which can be used as a reference when sculpting the brace, in its low poly formulation.
Moreover, a NURBS-surface formulation of the model was imported in the numerical simulation tool to compute the interaction between the brace and the patient’s body. A set of simplified simulations was performed to verify the usability of the developed model and the possibility to obtain a relatively fast numerical simulation to validate the sculpted brace before 3D printing it during the design phase. The simulations converged showing the possible interaction analysis, but they required more than an hour due to the non-linearity of the contact problem. Complementary simulations where performed on the simpler case of a wrist orthosis without considering the interaction with the patient’s anatomy. The orthosis was constrained as a cantilever beam supported with a roller and loaded with a force in the hand palm. This simulation assessed the feasibility of using the Topology Optimization tool for reducing the weight of an orthotic device, obtaining an optimized material distribution in contrast to purely aesthetic patterns. The mass was reduced of about 25% in 6 minutes, which was more than 10 times the static structural simulation time. This means that applying the Topology Optimization to the more complex case of the chest brace with the contact interaction could be exponentially larger.
Regarding the Additive Manufacturing, the FFF technology was selected for the best compromise in terms of costs, speed and printing volume. Different materials were initially considered, but only PLA and PETG were deeply analyzed and compared to the thermoformed material (PP). The best results were obtained with the PETG, both for the mechanical properties and for the inter-layer adhesion, verified with a SEM analysis. This material was thus used for 3D printing a full brace that was successfully tested with a volunteering patient. The positive feedback regarded not only the patient but also the orthopedic physician and technicians involved in the experiment.
The overall conclusion of the thesis is that the process is currently feasible in all the different steps, even though these have to be performed separately by using different software packages. Thus, a further integration of the various tools is required in order to allow a simpler implementation of the process in the orthopedic centers.DIPARTIMENTO DI MECCANICAEngineering Design and Manufacturing for the Industry of the Future32VEDANI, MAURIZIOROCCHI, DANIEL
Analisi sperimentale e modellazione numerica dell'interazione tra l'invaso di una protesi di arto inferiore e l'arto residuo
No full textLAUREA MAGISTRALEQuesto lavoro di tesi fa parte di un programma di ricerca finalizzato alla virtualizzazione del processo di progettazione e di produzione per protesi di arto inferiore, denominato Socket Modeling Assistant.
La tesi è focalizzata su tecniche per la valutazione del comfort garantito dall'invaso che viene progettato. Questa valutazione si basa tipicamente sulla pressione di contatto e quindi, per quantificare questo comfort in fase di progettazione, si pensa che il metodo più adeguato sia quello degli elementi finiti. Avendo però bisogno di validare la simulazione numerica con misure sperimentali, al fine di trovare una buona correlazione tra le informazioni risultanti, è stato sviluppato questo lavoro di tesi.
Analizzando le ricerche precedenti, si è riscontrato che non sono molte quelle eseguite sia per la parte di simulazione che per la parte di analisi sperimentale, inoltre sono in gran parte riguardanti le amputazioni transtibiali. Altre ricerche riguardanti i casi di amputazioni transfemorali propongono analisi sperimentali separate da quelle numeriche, con il conseguente problema della comparazione dei risultati tra soggetti diversi.
Si è partiti da una fase di indagine riguardante le impostazioni del software di simulazione che permettessero di analizzare il difficile problema del contatto tra invaso e moncone. In parallelo è stata condotta un'analisi preliminare riguardante il sistema di acquisizione delle pressioni. Definite quindi le opzioni considerate migliori per la sperimentazione e redatte le procedure riportate nel testo, è stato possibile eseguire una sessione di prove con un paziente transfemorale preso in esame. Durante tale sessione sono stati scansionati il paziente e l'invaso da cui sono stati ricavati i modelli geometrici, usati in seguito nelle simulazioni.
Eseguite infine le analisi FEM, è stato riscontrato che la distribuzione delle pressioni ottenuta è paragonabile a quella sperimentale. Il metodo numerico può essere quindi un valido supporto per la produzione di componenti tanto soggettive quanto lo sono gli invasi per le protesi di arto inferiore.This thesis is part of a research program directed to the virtualization of the designing and production process for lower limb prosthesis, named Socket Modeling Assistant.
The thesis focuses on the techniques of evaluation of the comfort guaranteed by the designed socket. This evaluation is typically based on the contact pressure and thus, in order to quantify this comfort in the designing phase, we think that the most adequate technique is the Finite Element Method. But since we need to validate the numerical simulation with experimental measurement, with the aim of finding a good correlation between the resulting data, we developed the work described in this thesis.
After analyzing the previous researches, I found out that there are not many about both the simulation part and the experimental analysis, moreover these deal mostly with the transtibial amputations. Other researches about the transfemoral cases propose experimental analyses separated from the numerical ones, with the consequent problem of comparing results between different subjects.
The work has started with a period of investigation about the settings of the simulation software that could allow us to analyze the difficult problem of contact between residual limb and socket. In parallel a preliminary analysis has been developed about the pressure acquisition system. After having defined which are the setting considered to be the best ones for the experiments and having written the procedures shown in the text, it has been possible to execute a session of tests with a transfemoral patient. During this session both the patient and the actual socket were scanned to produce the geometrical models, that were after used in the simulations.
Completed the FEM analyses, I discovered that the obtained pressure distribution is comparable to the experimental one. Thus the numerical method can be used as a valid support for production of components as personal as the sockets for lower limb prosthesis
A Comparative Study for Material Selection in 3D Printing of Scoliosis Back Brace
No full textIn recent years, many research studies have focused on the application of 3D printing in the production of orthopaedic back braces. Several advantages, such as the ability to customise complex shapes, improved therapeutic effect and reduced production costs place this technology at the forefront in the ongoing evolution of the orthopaedic sector. In this work, four different materials, two of them poly(lactic acid) (PLA) and two of them poly(ethylene terephthalate glycol) (PETG), were characterised from a thermal, mechanical, rheological and morphological point of view. Our aim was to understand the effects of the material properties on the quality and functionality of a 3D-printed device. The specimens were cut from 3D-printed hemi-cylinders in two different orientation angles. Our results show that PETG-based samples have the best mechanical properties in terms of elastic modulus and elongation at break. The PLA-based samples demonstrated typical brittle behaviour, with elongation at break one order of magnitude lower. Impact tests demonstrated that the PETG-based samples had better properties in terms of energy absorption. Moreover, 3D-printed PETG samples demonstrated a better surface finishing with a more homogenous fibre–fibre interface. In summary, we demonstrate that the right choice of material and printing conditions are fundamental to satisfy the quality and functionality required for a scoliosis back brace
Postural stability metrics associated to the publication: Additive manufacturing of spinal braces: evaluation of production process and postural stability in patients with scoliosis
No full textData was collected for each condition (3D-printed brace, conventional brace, unbraced) for 60 seconds with patients in a standing posture, open eyes and both feet together.This research was funded by EMPATIA@Lecco Empowerment del Paziente In cAsa— Bando Emblematico Fondazione Cariplo 2016 and Regione Lombardia and by the Italian Ministry of Health (Ricerca Corrente 2022 awarded to E. Biffi)
Learning My Way: A Pilot Study of Navigation Skills in Cerebral Palsy in Immersive Virtual Reality
No full text: Purpose: Human navigation skills are essential for everyday life and rely on several cognitive abilities, among which visual-spatial competences that are impaired in subjects with cerebral palsy (CP). In this work, we proposed navigation tasks in immersive virtual reality (IVR) to 15 children with CP and 13 typically developing (TD) peers in order to assess the individual navigation strategies and their modifiability in a situation resembling real life. Methods: We developed and adapted to IVR an application based on a 5-way maze in a playground that was to be navigated to find a reward. The learning process, navigation strategies, and adaptation to changes were compared between participants with CP and their TD peers and correlated with visual-spatial abilities and cognitive competences. Results: Most participants with CP needed more attempts than TD participants to become proficient in navigation. Furthermore, the learning phase was correlated to visual-spatial memory but not with cognitive competences. Interestingly, navigation skills were comparable between groups after stabilization. While TD participants mainly relied on allocentric strategies based on environmental cues, egocentric (self-centered) strategies based on body motion prevailed in participants with CP. Furthermore, participants with CP had more difficulties in modifying their navigation strategies, caused by difficulties in executive processes beyond the visual-perceptual impairment, with an inefficient shift between implicit and explicit competences. Conclusions: The navigation abilities in participants with CP seem to be different from their TD peers in terms of learning and adaptation to new conditions; this could deeply affect their everyday life and ultimately participation and inclusion. A regular assessing and focused rehabilitative plans could help to better navigate the environment and affect self-perception
