1,721,003 research outputs found
Le sedi dell'Università di Modena e Reggio Emilia
No full textLe sedi dell'Università di Modena e Reggio Emili
Design and Virtual Prototyping of a Variable Stiffness Joint via Shape Optimization in a CAD/CAE Environment
No full textDuring the latest decade, collaborative robots, namely machines specifically designed for the physical interaction with humans, have been gradually making their transition from laboratories to real-world applications [1]. Naturally, whenever the envisaged task would benefit form physical human-machine interaction, safety and dependability become issues of paramount importance [2]. Nonetheless, especially when dealing with collaborative operations in the manufacturing industry, safety regulations may lead the plant designer to face opposite goals. On one hand, robots should indeed be designed so as to never cause harm to people (both during regular functioning or in case of failure). On the other hand, the wide-spread use of industrial manipulators traditionally leverages on their capabilities to carry rather high payloads, while achieving a very fast and precise positioning of the end-effector. These requirements are usually pursued by coupling powerful actuation systems with extremely rigid mechanical structures, which hardly comply with safety needs whenever the workers are supposed to enter the robot workspace. Therefore, the engineering challenge when designing collaborative robotics systems, which have to be safe and efficient at the same time, is usually tackled via the following strategies: i) by enhancing the robot sensory apparatus; ii) by adopting active control strategies; iii) by reducing the inertia of any moving part employing lightweight materials whenever possible. In parallel, as previously proven by several researchers [3], another way to actually implement safe machines for collaborative tasks is to increase (rather than minimize) the inherent compliance of their mechanical structure [4], simultaneously introducing the possibility to actively vary such compliance during the robot movements. This capability can be implemented, for instance, by means of Variable Stiffness Joints (VSJ), namely particular actuation systems which allow to independently control the position of an output link along with the transmission stiffness. In light of this consideration, the present talk describes the design of a novel VSJ architecture, depicted in Fig. 1a. The VSJ can achieve stiffness modulation via the use of a pair of compliant mechanisms with distributed compliance, which act as nonlinear springs with proper torque-deflection characteristic. These elastic elements are composed of slender beams whose neutral axis is described by a spline curve with non-trivial shape. The beam geometry is determined by leveraging on a CAD/CAE framework that allows for the shape optimization of complex flexures. In particular, the design method makes use of the modeling and simulation capabilities of a parametric CAD seamlessly connected to a FEM tool. For validation purposes, proof-concept 3D printed prototypes of both elastic elements (Fig. 1a) and overall VSJ (Fig. 1b) are finally produced and tested (Fig. 1c). Experimental results fully confirm that the VSJ behaves as expected.
BIBLIOGRAFY
[1] Heyer, C., 2010. “Human-robot interaction and future industrial robotics applications”. Proceeding of the IEEE/RSJ International Conference on Intelligent Robots and Systems, pp. 4749–4754.
[2] Fryman, J., and Matthias, B., 2012. “Safety of industrial robots: From conventional to collaborative applications”. Proceeding of ROBOTIK, 7th German Conference on Robotics, May, pp. 1–5.
[3] Bicchi, A., and Tonietti, G., 2004. “Fast and soft arm tactics: Dealing with the safety-performance trade-off in robot arms design and control”. IEEE Robotics and Automation Magazine, 11(2), pp. 22–33.
[4] Berselli, G., Guerra, A., Vassura, G., and Andrisano, A. O., 2014. “An engineering method for comparing selectively compliant joints in robotic structures”. IEEE/ASME Transactions on Mechatronics, 19(6), pp. 1882–1895
A Multi-disciplinary Assessments Tool for Human-Machine Interaction
No full textHuman-centered design is based on the satisfaction of the user needs mainly related to performances, interaction, usability, accessibility, and visibility issues. However, the quality of the interaction process is hidden and usually difficult to detect. The paper proposes a multi-disciplinary assessment tool for the evaluation of the human-machine interaction, based on the collection of physiological data and anthropometrical performance data. Such a method can be used both within on-field tests and virtual simulations, supporting the spread of digital approaches in industry. The methodology allows objectifying how users interact with machine or interface items, thanks to the collection of the users’ performance during task execution, the digitalization of collected data, and the evaluation of users’ physical and mental workload. Such a system has been applied to an industrial case study focusing on agricultural machinery driving and control to support the system re-design in terms of interface features, commands’ location and grouping, and positioning of additional devices
UNA CONFIGURACIÓN DE REALIDAD VIRTUAL MULTIMODAL PARA EL DISEÑO CENTRADO EN EL SER HUMANO DE ESTACIONES DE TRABAJO INDUSTRIALES
Full text linkAlthough the so-called Industry 4.0 trend is promoting the increasing automation of processes in the factories of the future, manual activities still play an extremely important role within the factory and human factors greatly affect the process performance. However, the analysis of human- machine interaction and the prediction of human performance in industry are difficult but crucial to have an optimized design of workspaces and interfaces, reducing time and cost of implementation, and avoiding late design changes. This research adopts a multimodal human-centered approach for the analysis of human-machine interaction, and proposes a multimodal experimental set-up for the evaluation of the workers’ experience to support the design of industrial workstations. The set-up combines virtual mock-ups, interaction with both physical and virtual objects, and monitoring sensors to track users and analyze their actions and reactions. It allows creating a multimodal environment able to deepen the interaction between humans and systems or interfaces, to support design activities. Indeed, it has been demonstrated that the analysis of the reactions of the users involved, allows to evaluate the quality of the interaction, identify the critical issues, define corrective actions, and propose guidelines for system design or redesign [1]. The paper describes the application of the proposed set-up on two industrial case studies and reports the main results
Quasi-Cyclic Doubly Generalized LDPC Codes
No full textWe introduce a class of structured (protograph-based)
doubly generalized low-density parity-check (DGLDPC)
codes. The proposed class leads to quasi-cyclic codes for which efficient encoder and decoder implementations are possible. In particular, we illustrate that on the additive white Gaussian noise (AWGN) channel, the introduced structured DGLDPC codes do not lose in performance with respect to unstructured DGLDPC codes. Furthermore, a sufficient condition on the code graph is derived, which allows unveiling the quasi-cyclic nature of the designed codes
Development And Validation Of A New Methodology For Human-Centered Workstation Design
No full textNowadays, modern factories are paying a growing attention to human-centered workplaces, tailored to the needs of workers, as a recurring theme of Industry 4.0 [1]. This approach, which makes the worker at the center of the factory system according to a Human-Centered view [2], is based on a careful ergonomic analysis of the workstations, taking into account the cycle time required for the tasks completion and related recovery times. From the combination of factory ergonomics and time-method analysis, a new methodology has been defined to support the design of human-centered workplaces, called “ERGO-MTM-UAS”.
This new methodology therefore aims to reduce the risks to the health of the worker’s musculoskeletal system (usually linked to repetitive tasks) associating a specific methodology of work time measurement (MTM-UAS) with an ergonomics assessment and risk factors evaluation checklist (EAWS).
The analysis consists of three main steps:
• • Assignment of a basic work time through the MTM-UAS methodology;
• • Calculation of the recovery time considering the risk factor through the EAWS checklist;
• • Definition of the total work time summing the basic time and recovery time.
The industrial case study has been developed in collaboration with CNH Industrial, focusing on the assembly of ATS (After Treatment System) on the hood support of a large size tractor. The final aim was to validate the new methodology by applying to a real case study, comparing to the ideal case study without recovery time. To achieve this goal, a calculation sheet has been developed in Visual Basic code. In the first part, it allows to calculate the estimated time to complete a specific task, subdividing it in sub-tasks. In the second part, it allows to evaluate risks factors with the EAWS score and calculate the recovery time needed at the end of the entire task. In addition, the user could choice to insert postures data by the direct observation of workers but also from JACK Siemens postures data files.
Fig.1 shows the results of the analysis on the case study: the estimated time to complete the selected task is about 12 minutes and 46,7 seconds by applying the MTM-UAS method, while the EAWS method suggests a recovery time of 2 min and 16 sec. The total time to achieve the task has been found to be 14 min and 34 sec, very close to the estimated time by recovery time. The results of this analysis confirmed the applicability of the new methodology, underlining the vital importance of adopting a careful ergonomic feasibility study to properly design complex and long-term assembly processes. The main advantage of the proposed method is the possibility to introduce an ergonomic assessment before the process creation, to be applied at the early stage of the design process, to assure reducing the workers’ musculoskeletal disorders and costs for workstation redesign.
REFERENCES
[1] Gregori, F., Papetti, A., Pandolfi, M., Peruzzini, M. and Germani, M., 2017. “Digital manufacturing system: a framework to improve social sustainability of a production site”. The 50th CIRP Conference on Manufacturing System, 2017 on Sustinable Manufacturing, Vol. 63 of Procedia CIRP, pp. 436 – 442.
[2] May, G., Taish, M., Bettoni, A., Maghazei, O., Matarrazzo, A., Stahl, B., 2015. “A new Human-centric Factory Model”. 12th Global Conference on Sustinable Manufacturing, Vol. 26 of Procedia CIRP, pp. 103-108
Il progetto AREUS – robotica industriale eco-efficiente e sostenibile
No full textL’impiego esteso di robot industriali nei processi di manifattura permette di ottenere la superiore qualità e produttività richiesta dai mercati; i paradigmi dell’Industria 4.0 prevedono inoltre un notevole ulteriore incremento del numero di robot, che purtroppo rischia di compromettere la sostenibilità delle fabbriche del futuro in termini sia finanziari che ambientali. Infatti, i sistemi di produzione meccatronici e robotizzati sono intrinsecamente energivori e impattano pesantemente sulla potenza installata ed i consumi energetici aziendali. Allo stato dell’arte si è lavorato soprattutto per migliorare l’efficienza dei singoli robot, ma è mancato un reale approccio di sistema, necessario per ottimizzare il consumo energetico totale di celle ed impianti robotizzati. Recentemente, sono stati introdotti sul mercato tool di simulazione proprietari capaci di predire il consumo energetico dei singoli robot [1] ma non dell’applicazione (i.e.: robot, utensili, macchinari, etc.), e pertanto risultano solo parzialmente utili per dimensionare empiricamente la cabina elettrica.
Il progetto europeo FP7 AREUS – Automation and Robotics for EUropean Sustainable manufacturing [2], coordinato da UNIMORE, ha come obiettivo la riduzione dei consumi energetici e del LifeCycle Cost (LCC) di impianti robotizzati mediante quattro innovazioni modulari e scalabili. Una nuova architettura industriale di smartgrid a corrente continua (DC) permette la rigenerazione ed il recupero energetico tra diversi robot e macchinari, mentre un set di tool di simulazione e controllo basati sul concetto di Energy Signature [3] abilitano l’ottimizzazione dei consumi energetici dell’intero impianto mantenendo la stessa produttività e qualità di lavorazione, sfruttando il coordinamento ed il recupero di energia.
Infine, un innovativo approccio al LifeCycle Assesment (LCA) ha permesso di sviluppare tools specifici per impianti robotizzati, ideali per calcolare con superiore precisione l’impatto ambientale e finanziario di ogni soluzione di produzione robotizzata.
In questa presentazione, si mostreranno i principali avanzamenti, rispetto allo stato dell’arte, introdotti dal progetto AREUS e, in particolare, i risultati di ricerca e sviluppo ottenuti nei seguenti WorkPackages (WP), correlati alle suddette innovazioni e schematizzati in Fig. 1
• WP 1: Nuove architetture hardware (e.g. [4]) per la riduzione del consumo energetico, basate su un innovativo sistema di distribuzione dell’energia elettrica con migliori possibilità di distribuire, recuperare ed immagazzinare energia a livello di fabbrica;
• WP2: Un innovativo ambiente integrato di simulazione e design (e.g. [5,6]), specificamente concepito per il progetto e la programmazione eco-efficiente di grandi impianti robotizzati;
• WP3: Nuovi metodi di ottimizzazione, interamente connessi ai tools di simulazione di cui al punto 2), specificamente concepiti per la determinazione di scheduling dell’operazioni esplicitamente mirati alla riduzione dei consumi energetici (sia in termini globali che in termini di potenze massime assorbite istantaneamente [7,8]);
• WP4: Nuovi metodi di LCA concepiti per predire/ottimizzare sia l’impatto economico che ambientale della fabbrica automatizzata [9]
Progetto Ed Ottimizzazione Di Forma Di Un Dispositivo Cedevole A Forza Costante
No full textNell’ambito della progettazione di dispositivi per la manipolazione di parti, la regolazione della forza di contatto rappresenta un problema di notevole rilevanza, specialmente nel caso di interazione con oggetti fragili o altamente flessibili. Nella pratica, i grippers industriali sono spesso equipaggiati con architetture di controllo anche complesse e con opportuni apparati sensoriali (e.g. sensori di forza o pressione), il cui scopo è quello di mantenere le forze di contatto ad un valore prefissato. Tali sistemi meccatronici consentono una notevole flessibilità ma, al contempo, possono risultare inadeguati o estremamente costosi in applicazioni per oggetti di piccole dimensioni (e.g. micro-scala). In questo caso, un’interessante alternativa alla regolazione attiva della forza è rappresentata dall’impiego di strutture cedevoli (compliant mechanisms [1,2]) appositamente progettate in modo da garantire una forza di reazione quasi-costante a fronte di spostamenti imposti di rilevante entità [3]. Alla luce di tali considerazioni, l’obiettivo di questa memoria è descrivere la progettazione di un meccanismo cedevole ad un grado di libertà caratterizzato da rigidezza limitata (idealmente nulla) all’interno di un ampio range di funzionamento. La metodologia progettuale si compone di due steps concettuali: 1) nel primo step, una soluzione sub-ottima viene ricavata utilizzando soluzioni note da letteratura e basate sull’utilizzo di modelli pseudo-rigidi a parametri concentrati [1]. Il risultato di questa prima fase è mostrato in Figura 1a, che riporta la geometria di un meccanismo flessibile (composto da tre cerniere elastiche), in grado di fornire una forza costante per limitati valori di spostamento imposto.2) nel secondo step, la soluzione precedente viene ulteriormente ottimizzata, utilizzando una singola struttura trabeiforme. Tale struttura è caratterizzata da spessore continuamente variabile e da asse neutro la cui forma è descritta da una funzione spline. In questa seconda fase, la geometria ottimale viene determinata utilizzando una procedura iterativa basata su uno script di Matlab e successive simulazioni FEM realizzate mediante il software Ansys APDL. Rispetto al design a cedevolezza concentrata, il dispositivo a cedevolezza distribuita, presentato in Figura 1b, garantisce la costanza della forza a fronte di un notevole incremento del range di funzionamento ammissibile. I risultati delle simulazioni sono confermati mediante sperimentazione su prototipi fisici realizzati in stampa 3D (vedi Figura 2a). Infine, Figura 2b riporta il design concettuale di un micro-gripper basato sull’utilizzo di quattro strutture a forza costante.
[1] Howell, L. L., 2001. Compliant mechanisms. John Wiley & Sons.
[2] Berselli, G., Guerra, A., Vassura, G., and Andrisano, A.O., 2014. “An engineering method for comparing
selectively compliant joints in robotic structures”. IEEE/ASME Transactions on Mechatronics, 19(6), pp. 1882–1895.
[3] Liu, Y., and Xu, Q., 2017. “Design of a 3D-printed polymeric compliant constant-force buffering gripping mechanism”. IEEE ICRA International Conference on Robotics and Automation, pp. 6706–6711
Effective spectral efficiency for adaptive QAM with diversity and pilot assisted channel estimation
No full textThis paper investigates the effects of non-ideal channel state information in adaptive M-ary quadrature amplitude modulation systems with subset diversity. The slow adaptive modulation (SAM) technique, which adapts the modulation parameters to slow channel variations, is considered. With respects to fixed scheme modulation systems, SAM achieves a good gain in terms of spectral efficiency (SE) and outage probability and, compared to fast adaptive modulation, reduces the system complexity by lowering the feedback rate. Resources dedicated to channel estimation affect both the system performance, in terms of error and outage probability, and the effective SE for which a proper definition is needed. Here, we evaluate the performance of SAM technique when pilot-assisted channel estimation errors are considered. Taking into account the number of pilot symbols transmitted, an effective SE is obtained to address the tradeoff between channel estimation quality and SE
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