Every year millions of workers are affected by Work-Related Musculoskeletal Disorders (WMSDs) through their work. The main groups of WMSDs are back and upper limb pain and injuries. They are causally linked to physical load and posture of the operator resulting from occupational activities. To limit this problem there is a growing movement towards human-robot collaboration. Within this context, nowadays the use of wearable technologies, such as exoskeletons, is highly developing in the industrial sector, to improve workers health and efficiency. Despite the high interest for industrial exoskeltons, their large-scale implementation in industry has still a long way to go. Indeed, although they can reduce demands on specific body parts, they may also have unintended consequences such as increasing loading and/or discomfort on other regions of the wearer's body. In order to analyze these side effects, the scientific community has opted for subjective metrics and analysis of muscular activity (electromyography - EMG) in laboratory environment. However, also in a laboratory environment, it is difficult to analyze the effective biomechanical load at joints during the execution of the tasks, particularly with respect to low spine. In addition, the difficulty to recruit a consistent number of participants, ethical reasons, cost of the experimental set-up and the limited available space prevent a proper analysis. In particular, in order to mimic what happens in the real working scenario, different subjects need to adopt different postures (that might be unhealthy), carry out different activities for a long or a short time without and with the exoskeleton(s), and this is often impossible to be implemented. Simulations in a virtual environment can reduce the limits of experimental tests. Nevertheless, the experimental tests remain an important instrument to detect the human feeling in terms of usability and perceived relief, which is anyhow an important factor. In this context, the aim of this work is to make use of newly developed software, Santos Human developed by University of Iowa Virtual Soldier Research (VSR) - an advanced human modeling software that provides a realistic virtual human simulation - to provide an objective ergonomic evaluation method of exoskeletons. With the proposed approach, the effects of various configurations of exoskeleton on virtual subjects with different anthropometric dimensions can be compared and quantified. Torque values at each joint, biomechanical load at low spine level, and posture stability resulting from different typologies of exoskeleton can be quantitatively analyzed. In particular, two exoskeletons derived from literature have been included in the analysis, modeled and simulated in Santos Human: low back support exoskeleton, and upper body exoskeleton. In the virtual environment, virtual subjects with the two configurations of exoskeleton maintain different static postures and executing different tasks, considered at risk for developing WMSDs. The effects of the exoskeletons are investigated in terms of torque values at each joint, spine shear and compression forces and posture stability. For each activity in which virtual subjects are involved, the values of assistive force and reaction force for each configuration of exoskeleton, that provide minimal values of biomechanical load at low spine and joint torques are determined.
Ogni anno milioni di lavoratori sono affetti da Disturbi Muscolo Scheletrici (DMSs) derivanti da attività lavorative. I principali DMSs sono dolori/infortuni agli arti superiori e rachide, provocati da carichi fisici e posture che l'operatore assume durante l'attività lavorativa. Per limitare questo problema c'è un crescente interesse verso la collaborazione umano-robot. All'interno di questo contesto, al giorno d'oggi l'utilizzo di tecnologie indossabili, come gli esoscheletri, si sta altamente sviluppando nel settore industriale, allo scopo di migliorare la saluta e l'efficienza dei lavoratori. Nonostante ci sia alto interesse nei confronti degli esoscheletri industriali, la loro implementazione su larga scala nel settore industriale richiede ancora molta strada da fare. Infatti, sebbene possano ridurre l'affaticamento fisico in certe regioni corporee, potrebbero provocare conseguenze indesiderate come sovraccarico o discomfort in altre regioni anatomiche dell'utilizzatore. Allo scopo di analizzare questi effetti indesiderati, la comunità scientifica ha optato per metriche soggettive ed analisi dell'attività muscolare (elettromiografia - EMG) in ambiente di laboratorio. Tuttavia, anche in ambiente di laboratorio, è difficile analizzare il carico biomeccanico effettivo ai vari giunti corporei durante l'esecuzione di attività, in particolare rispetto al rachide. In aggiunta, la difficoltà di reclutare un numero consistente di partecipanti, ragioni etiche, costi del set-up sperimentale ed il limitato spazio disponibile impediscono un'analisi appropriata. In particolare, allo scopo di replicare ciò che accade in uno scenario lavorativo reale, differenti soggetti devono adottare differenti posture (potrebbe essere poco salutare), compiere differenti attività per un tempo breve o lungo senza e con l'/gli esoscheletro(i), e questo è spesso impossibile da implementare. Simulazioni in un ambiente virtuale possono ridurre i limiti dei test sperimentali. Ciononostante, i test sperimentali rimangono uno strumento importante per rilevare la sensibilità umana in termini di usabilità e sostegno percepito, che è ad ogni modo un fattore importante. In questo contesto, l'obiettivo di questo lavoro è di utilizzare un software di recente sviluppo, Santos Human sviluppato dall'Università di Iowa Virtual Soldier Research (VSR) - un software di modellazione umana avanzato che fornisce una simulazione umana virtuale realistica - allo scopo di fornire un metodo di valutazione ergonomica degli esoscheletri oggettivo. Con l'approccio proposto, gli effetti di varie configurazioni di esoscheletro su soggetti virtuali con differenti dimensioni antropometriche possono essere confrontati e quantificati. Valori di sforzo ad ogni giunto, carico biomeccanico a livello del rachide, e stabilità posturale risultanti da differenti tipologie di esoscheletro possono essere analizzati quantitativamente. In particolare, due esoscheletri derivanti dalla letteratura sono stati inclusi nell'analisi, modellati e simulati in Santos Human: esoscheletro di supporto al rachide, ed esoscheletro di supporto della parte superiore del corpo. In ambiente virtuale, soggetti virtuali con le due configurazioni di esoscheletro mantengono differenti posture statiche ed eseguono differenti attività, considerate a rischio per lo sviluppo di DMSs. Gli effetti degli esoscheletri sono analizzati in termini di valori di sforzo ai vari giunti corporei, forze di compressione e taglio al rachide e stabilità posturale. Per ogni attività in cui i soggetti virtuali sono coinvolti, i valori di forza di assistenza e di scarico per ogni configurazione di esoscheletro, che forniscono valori minimi di carico biomeccanico al rachide e sforzo ai giunti sono stati calcolati.
Ergonomic evaluation of exoskeletons in a virtual environment
GATTONI, NICOLA
2018/2019
Abstract
Every year millions of workers are affected by Work-Related Musculoskeletal Disorders (WMSDs) through their work. The main groups of WMSDs are back and upper limb pain and injuries. They are causally linked to physical load and posture of the operator resulting from occupational activities. To limit this problem there is a growing movement towards human-robot collaboration. Within this context, nowadays the use of wearable technologies, such as exoskeletons, is highly developing in the industrial sector, to improve workers health and efficiency. Despite the high interest for industrial exoskeltons, their large-scale implementation in industry has still a long way to go. Indeed, although they can reduce demands on specific body parts, they may also have unintended consequences such as increasing loading and/or discomfort on other regions of the wearer's body. In order to analyze these side effects, the scientific community has opted for subjective metrics and analysis of muscular activity (electromyography - EMG) in laboratory environment. However, also in a laboratory environment, it is difficult to analyze the effective biomechanical load at joints during the execution of the tasks, particularly with respect to low spine. In addition, the difficulty to recruit a consistent number of participants, ethical reasons, cost of the experimental set-up and the limited available space prevent a proper analysis. In particular, in order to mimic what happens in the real working scenario, different subjects need to adopt different postures (that might be unhealthy), carry out different activities for a long or a short time without and with the exoskeleton(s), and this is often impossible to be implemented. Simulations in a virtual environment can reduce the limits of experimental tests. Nevertheless, the experimental tests remain an important instrument to detect the human feeling in terms of usability and perceived relief, which is anyhow an important factor. In this context, the aim of this work is to make use of newly developed software, Santos Human developed by University of Iowa Virtual Soldier Research (VSR) - an advanced human modeling software that provides a realistic virtual human simulation - to provide an objective ergonomic evaluation method of exoskeletons. With the proposed approach, the effects of various configurations of exoskeleton on virtual subjects with different anthropometric dimensions can be compared and quantified. Torque values at each joint, biomechanical load at low spine level, and posture stability resulting from different typologies of exoskeleton can be quantitatively analyzed. In particular, two exoskeletons derived from literature have been included in the analysis, modeled and simulated in Santos Human: low back support exoskeleton, and upper body exoskeleton. In the virtual environment, virtual subjects with the two configurations of exoskeleton maintain different static postures and executing different tasks, considered at risk for developing WMSDs. The effects of the exoskeletons are investigated in terms of torque values at each joint, spine shear and compression forces and posture stability. For each activity in which virtual subjects are involved, the values of assistive force and reaction force for each configuration of exoskeleton, that provide minimal values of biomechanical load at low spine and joint torques are determined.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/154118