A. REHABILITATION ROBOTICS
- A1. upper limb powered prostheses
- A2. upper limb exoskeletons
B. ELASTODYNAMIC MODELLING OF MECHANICAL SYSTEMS
- B1. structures
- B2. mechanisms
C. EXPERIMENTAL ANALYSIS OF MECHANICAL VIBRATIONS
- C1. monitoring and diagnostics of mechanical system
- C2. identification of modal parameters
- C3. vibration qualification testing
A. Rehabilitation Robotics - In the field of Rehabilitation and Assistive Robotics, the candidate has been performing activities for the development of robotic aids (including synthesis, design, prototyping, and testing) addressed to subjects with impairments at the upper limbs. In particular, the research is focused on powered prostheses for upper limb amputees (A1) and, more recently, on hand and wrist exoskeletons for the rehabilitation of post-stroke patients (A2). The clinical aspects and the technical factors are systematically studied in order to optimize the contrasting requirements of the devices, namely their functional performance on one side and their wearability and easiness of control on the other one. In particular, for the activity A1, carried out in a strict collaboration with the INAIL Prosthetic Centre (Bologna, Italy), the candidate conceived and implemented an original procedure to optimize the design of upper limb prostheses for amputees with high-level disarticulations. The procedure, which can be considered as a multi-criteria optimization algorithm that consistently treats both clinical and engineering issues, was applied to support the design of new powered joints by determining the optimal architectures of the final prostheses for different amputee's reference profiles. Based on the technical specifications obtained from the procedure application, a novel shoulder articulation with 2 degrees of freedom (DOFs) and a new powered humeral rotator were designed, manufactured and tested (these devices being commercially unavailable). The prosthesis equipped with the powered shoulder articulation was awarded with a national prize in 2009. In this field the candidate was the principal investigator, being upper limb prosthetics the main topic afforded within his Ph.D. program. Among the several challenges afforded in this multidisciplinary research, it is worth mentioning a problem arisen in the experimental determination of the reference trajectories to be simulated by different upper limb prosthesis models. The data acquired by means of an optoelectronic system for the human motion analysis can be affected by an error, named "skin artifact", due to the relative motion between the subject's skin (where reflective markers are fixed) and the underlying bones (whose motion must be tracked). A method for the evaluation (and possible compensation) of the error was proposed and particularly appreciated by the Italian Society of Clinical Motion Analysis, which endorsed it with a special award in 2003 . In this context, the candidate (being the only mechanical engineering among biomedical and electronic engineers in the research team involved in the activity) proposed and implemented the original algorithms that, based on spatial kinematic analysis of two reference frames properly built, permit to estimate the skin artifact (what is the core of the work). The activity A2, more recent, was started within the framework of a project (Project SEED 2009: "Brain computer interfaces for Robotic enhanced Action in Visuo-motOr tasks (BRAVO)") funded by the Italian Institute of Technology (Genoa, Italy). The research unit of the candidate was involved in the design of the distal part of an upper limb exoskeleton, i.e. the wrist and the hand. Many efforts were spent to determine the guidelines and the technical specifications for the development of the hand exoskeleton, whose purpose is to assist post-stroke patients in grasping cylindrical objects during rehabilitation exercises. An original solution with two DOFs, based on a modular layout of the finger mechanisms, was selected and developed. In this context, the candidate defined the algorithms for the synthesis of the finger mechanisms and supervised their implementation, participated to the executive design, supervised the prototype manufacturing and bench testing, and finally contributed - in part only - to the preliminary tests in collaboration with the "Perceptual Robotics Laboratory - PERCRO" (Pisa, Italy). For the development of the wrist exoskeleton, the candidate contributed to the executive design, the prototype manufacturing, and the bench testing.
B. Elastodynamic Modeling of Mechanical Systems The studies in the field of Dynamic of Machines started in 2006, when the candidate, just completed the PhD program, joined the research unit led by prof. Alessandro Rivola, active in this field. The research deals with the study of the dynamic behaviour of high-performance mechanical systems (e.g. automatic machines, machine tools, engine timing systems and cranktrains). Uncontrolled vibrations, due to the inertial effects associated with rapid and non-uniform motions, are known to possibly worsen the actual performance of these systems. In this context, the purpose of the research activity is to analyze and/or predict the system dynamic behaviours by means of simulations of proper kineto-elastodynamic models. The core of this study consists of the definition and simulation of different models, aiming at defining general procedures suitable for the analysis of the most popular mechanical (sub-)systems. Most of the papers co-authored by the candidate are relative to industrial applications, for which the research activities were carried out in collaboration with companies active in the fields of industrial automation and automotive. Applications are various: analyzing the relationship between the system parameters (geometric and functional parameters) and the system dynamic behaviour, predicting the vibratory behaviour of mechanical systems for the design optimization of components and/or mechanisms, supporting the experiments for vibration testing. Depending on the system and the application of the models (which generally present several non-linearities), different modelling approaches are adopted: lumped-parameters, finite elements, flexible multibody systems. The simulation results of the developed models are often validated by means of experimental data (so that activities B and C are somehow linked). The contribution of the candidate in this field has been progressively grown from the first applications to the most recent works, when a complete autonomy was acquired in the model development and implementation as well as in the results analysis and interpretation.
C. Experimental Analysis of Mechanical Vibrations - The study of the dynamic behaviour of a mechanical system generally requires experimental data (e.g. for the model validations). A proper signal processing is needed to correctly interpret all the information brought by the experimental data. Many techniques can be used to process the data (typically acquired by means of accelerometers, force sensors, tacho sensors), from the common time domain analysis and frequency domain analysis to the more advanced time-frequency analyses. The experimental study of vibrations involves many fields, and the candidate's activity has been dealing with:measurement of vibration level in machines and structures, Experimental Modal Analysis (EMA), Operational Modal Analysis (OMA), updating and validation of numerical models, vibration qualification testing, rotating machinery analysis. Though this activity is the most recent in the candidate's experience, nowadays he has competencies to autonomously carry out experimental campaigns from the first stage of design of experiment to the test conduction, from the data processing (using advanced commercial software and/or by elaborating self-made algorithms) to the final result interpretation. In particular, the candidate operates with the instrumentation present at the Laboratory of Dynamics and Machine Vibrations of his department, equipped for the measurement and the experimental analysis of machine vibrations, for experimental modal analysis and for vibration qualification testing. An interesting research is carried out in collaboration with Siemens Industry Software and deals with the Mission Synthesis (i.e. the definition of test input profiles) for vibration qualification testing. Different numerical/experimental activities are conducted aiming (1) at the verification of the Fatigue Damage Spectrum (FDS) method, widely used for the determination of vibratory excitations having a limited duration suitable to laboratory tests, (2) at the validation of different methods to control the Kurtosis of both input and response during shaker tests, and (3) at the definition of a Mission Synthesis procedure for Sine-on-Random input profiles.