Stefano Filippi

A new design paradigm for the development of custom-fit soft sockets for lower limb prostheses

This paper presents a new 3D design paradigm for the development of specific custom-fit products, such as the soft socket of prostheses for lower limb amputees. It is centered on the digital model of the human body and, contrarily to the traditional process almost manually based, it considers the integration of methods and tools coming from different research and application fields: Reverse Engineering, Medical Imaging, Virtual Prototyping, Physics-based Simulation, and Rapid Prototyping. The paper describes the techniques adopted to acquire and create the digital model of the residual limb, the procedure to generate the socket model, the strategy developed for the functional simulation of the socket-stump interaction and, finally, the realization of the physical prototype. Each design step is described with the related problems and the obtained results. Both trans-tibial and trans-femoral amputees have been considered; however, for now the complete process has been validated for trans-tibial prostheses. Major outcomes of the proposed approach stand in a better quality of the final product, in a shorter involvement of the amputee implying a lower psychological impact, in a limited use of physical prototypes, and in a shorter development time. Moreover, the resulting paradigm answers to the Collaborative Engineering guidelines by optimizing the interaction between different domains and enhancing their contributions in a homogeneous development framework.

Accuracy of virtual reality and stereolithographic models in maxillo-facial surgical planning.

Computed tomography is a medical instrument that can be useful not only for diagnostic purposes, but also for surgical planning, thanks to the fact that it offers volumetric information which can be translated in three dimensional models. These models can be visualized, but also exported to Rapid Prototyping (RP) systems, that can produce these structures thanks to the rapidity and versatility of the technologies involved. The literature reports various cases of stereolithographic models used in orthopedic, neurological, and maxillo-facial surgery. In these contexts, the availability of a copy of the real anatomy allows not only planning, but also the practical execution of surgical operations, within the limitations of the materials. Nevertheless, the Rapid Prototyping model also presents some disadvantages that can be reduced if practical simulation is accompanied by virtual simulation, performed on a digital model. The purpose of this work is to examine and present the use of Virtual Reality (VR) and Rapid Prototyping for surgical planning in Maxillo-Facial surgery.

Analysis of existing methods for 3D modelling of femurs starting from two orthogonal images and development of a script for a commercial software package

BACKGROUND At present the interest in medical field about the generation of three-dimensional digital models of anatomical structures increases due to the widespread diffusion of CAS--computer assisted surgery--systems. Most of them are based on CT--computer tomography--or MR--magnetic resonance--data volumes but sometimes this information is not available; there are only few X-ray, ultrasound or fluoroscopic images. METHODS This paper describes the study and the development of a script for a commercial software package (3ds Max) able to reconfigure the template model of a femur starting from two orthogonal images representing the specific patients anatomy. RESULTS The script was used in several tests as summarized in this paper and the results appear to be interesting and acceptable, even for the medical experts that evaluated them. CONCLUSIONS The script developed in this work allows the generation of the 3D model of a femur in a very simple way (the user interface has been developed obeying to the main usability guidelines) and using a widespread commercial package. The quality of the results can be compared to the quality of more expensive and specialized systems.

Modular dynamic virtual-reality modeling of robotic systems

This article presents the results of research into the field of dynamic simulation of mechanical and robotic systems. The main goal of the whole project is to achieve an efficient modular approach to modeling, in order to make the modeling process easier, ensure its traceability and inspectability, and support model reuse. This is achieved through the declarative definition of models, the standardization of model interfaces, and the object-oriented approach to model development and model data management. The article presents the specific features ofa general-purpose simulation environment, including an overview of the 3D solid modeling software interfaces. The modeling and simulation of a 3-DOF gripper designed for Space robotics applications is also discussed to show the performance of the whole simulation environment in terms of complexity management, efficiency, and accuracy.

Generation, Adoption, and Tuning of Usability Evaluation Multimethods

The selection and customization of usability evaluation methods, given the peculiarities of their application domains, still remains a critical issue; this especially when dealing with complex products and/or nonexpert usability evaluators. Moreover, as time goes by, the quality of the evaluation results has a heavier impact on the product design process. Starting from classic usability evaluation methods, the research described in this article generates multimethods semiautomatically. It allows quantitative characterization of these multimethods before their application in the field and exploits the comparison between this prior assessment and a final estimate, made after adoption, to update the information used by the method selection process. The most critical issue related to usability, subjectivity, is considered and dealt with throughout the entire research. A case study, done at the end of the development phase, helps validate the proposed approach to usability evaluation.

The role of product feature relations in a knowledge based methodology to manage design modifications for product measurability

During product development, the verification process should already be considered at the design phase to ensure that the characteristics of the product are measured effectively and reliably. Moreover, the verification process may prove more effective if the inspector is aware of the specific designers intents. The development of the new ISO GPS (Geometrical Product Specifications) standards is mainly founded on these considerations. In accordance with the ISO GPS concepts, previous work developed a knowledge based system named Design GuideLines (DGLs). This system provides the designer with the knowledge concerning the manufacturing and verification procedures/tools and better links the manufacturing and verification processes to the designers activities/needs. Further research then exploited the DGLs to discover the relations among product features determined by a particular manufacturing process. This work again uses the DGLs to prove that further relations among product features may also be determined by the verification process. This knowledge helps designers in understanding the consequences of the modifications applied to the product features required to improve the measurability of the product. Moreover, inspectors can better manage the verification procedure knowing these relations among the product features.

A Methodology for Evaluating the Adoption of Knowledge and Innovation Management Tools in a Product Development Process

The efforts made by a company to focus on the manufacturing process to minimize production costs are not any more sufficient to launch competitive products on the market. In recent years, the industry has focused on the integration and optimization of the phases of the product development process and on the introduction of innovations in the attempt to tackle and solve the above mentioned issues. The paper presents the results of a research project whose aim is to study a methodology for the evaluation of the impact and costs related to the adoption of new and innovative technologies for knowledge and innovation management within currently implemented companies’ product development processes (As-Is process).Copyright

Comparing parametric solid modelling/reconfiguration, global shape modelling and free-form deformation for the generation of 3D digital models of femurs from X-ray images

At present, computer assisted surgery systems help orthopaedic surgeons both plan and perform surgical procedures. To enable these systems to function, it is crucial to have at ones disposal 3D models of anatomical structures, surgical tools and prostheses (if required). This paper analyses and compares three methods for generating 3D digital models of anatomical structures starting from X-ray images: parametric solid modelling/reconfiguration, global shape modelling and free-form deformation. Seven experiences involving the generation of a femur model were conducted by software developers and different skilled users. These experiences are described in detail and compared at different stages and from different points of view.

Customising a Knowledge-Based System for Design Optimisation in Fused Deposition Modelling RP-Technique

In a Design For Manufacturing context, Rapid Prototyping techniques are some way still considered as “new technologies”: the peculiar characteristics of the manufacturing processes are not widely known and may deeply affect the final product functionality. A Knowledge Based System, the Design Guidelines — DGLs, was developed by our Research Group at the University of Udine; it evaluated the products design, in order to verify its feasibility by DMLS (Direct Metal Laser Sintering) Rapid Prototyping technique. During the evaluation process, the DGLs also keep into consideration the aspects relating the verification step, according to the ISO-GPS principles, thus enhancing the completeness of the tool. Aim of this work was to customise the DGLs for design optimisation in FDM (Fused Deposition Modelling), also evidencing the critical aspects and proposing alternative solutions. The contents and structure of the customised version of DGLs are presented in this work.

Human in the loop: a model to integrate interaction issues in complex simulations

Several activities of the product development process as for example ergonomic analyses, usability testing, and what is defined as User Experience - UX- design in general require humans to be involved as testers. In order to achieve a good effectiveness degree, these tests must be performed on prototypes as much as possible similar to the final product, and this is costly and sometimes difficult to obtain during the development process. This is especially true at the earliest stages of the process. Functional mock-up - FMU - methods and tools can be of great help, because they allow technological aspects of the products, as electronics, hydraulics, mechanics, etc. to be represented and managed in a simple and effective way. Mathematical equations allow product behavior to be determined, due to input values representing the application environment of the product. At the moment, an FMU model is great in simulating product behavior from the technological point of view, but concerns about user interaction issues are left apart. The research described in this paper aims at widening the coverage of FMU to user-product interaction issues. The goal aims at evaluating the possibility of substituting real users with a characterization of them, and to model and simulate interaction in a homogeneous way together with all the other product aspects. All of this makes the research activities very challenging, and the result is a sort of FMU-assisted interaction modeling. As an evolution of what is generally recognized as hardware and software-in-the-loop, this methodology will be referred as human-in-the-loop.