Electromyography Based Human-Robot Interfaces for the Control of Artificial Hands and Wearable Devices

The design of robotic systems is currently facing human-inspired solutions as a road to replicate the human ability and flexibility in performing motor tasks. Especially for control and teleoperation purposes, the human-in-the-loop approach is a key element within the framework know as Human-Robot Interface. This thesis reports the research activity carried out for the design of Human-Robot Interfaces based on the detection of human motion intentions from surface electromyography. The main goal was to investigate intuitive and natural control solutions for the teleoperation of both robotic hands during grasping tasks and wearable devices during elbow assistive applications. The design solutions are based on the human motor control principles and surface electromyography interpretation, which are reviewed with emphasis on the concept of synergies. The electromyography based control strategies for the robotic hand grasping and the wearable device assistance are also reviewed. The contribution of this research for the control of artificial hands rely on the integration of different levels of the motor control synergistic organization, and on the combination of proportional control and machine learning approaches under the guideline of user-centred intuitiveness in the Human-Robot Interface design specifications. From the side of the wearable devices, the control of a novel upper limb assistive device based on the Twisted String Actuation concept is faced. The contribution regards the assistance of the elbow during load lifting tasks, exploring a simplification in the use of the surface electromyography within the design of the Human-Robot Interface. The aim is to work around complex subject-dependent algorithm calibrations required by joint torque estimation methods

The role of morphology of the thumb in anthropomorphic grasping : a review

The unique musculoskeletal structure of the human hand brings in wider dexterous capabilities to grasp and manipulate a repertoire of objects than the non-human primates. It has been widely accepted that the orientation and the position of the thumb plays an important role in this characteristic behavior. There have been numerous attempts to develop anthropomorphic robotic hands with varying levels of success. Nevertheless, manipulation ability in those hands is to be ameliorated even though they can grasp objects successfully. An appropriate model of the thumb is important to manipulate the objects against the fingers and to maintain the stability. Modeling these complex interactions about the mechanical axes of the joints and how to incorporate these joints in robotic thumbs is a challenging task. This article presents a review of the biomechanics of the human thumb and the robotic thumb designs to identify opportunities for future anthropomorphic robotic hands

The effects of robotic assistance on upper limb spatial muscle synergies in healthy people during planar upper-limb training

Background Robotic rehabilitation is a commonly adopted technique used to restore motor functionality of neurological patients. However, despite promising results were achieved, the effects of human-robot interaction on human motor control and the recovery mechanisms induced with robot assistance can be further investigated even on healthy subjects before translating to clinical practice. In this study, we adopt a standard paradigm for upper-limb rehabilitation (a planar device with assistive control) with linear and challenging curvilinear trajectories to investigate the effect of the assistance in human-robot interaction in healthy people. Methods Ten healthy subjects were instructed to perform a large set of radial and curvilinear movements in two interaction modes: 1) free movement (subjects hold the robot handle with no assistance) and 2) assisted movement (with a force tunnel assistance paradigm). Kinematics and EMGs from representative upper-limb muscles were recorded to extract phasic muscle synergies. The free and assisted interaction modes were compared assessing the level of assistance, error, and muscle synergy comparison between the two interaction modes. Results It was found that in free movement error magnitude is higher than with assistance, proving that task complexity required assistance also on healthy controls. Moreover, curvilinear tasks require more assistance than standard radial paths and error is higher. Interestingly, while assistance improved task performance, we found only a slight modification of phasic synergies when comparing assisted and free movement. Conclusions We found that on healthy people, the effect of assistance was significant on task performance, but limited on muscle synergies. The findings of this study can find applications for assessing human-robot interaction and to design training to maximize motor recovery

The effects of robotic assistance on upper limb spatial muscle synergies in healthy people during planar upper-limb training

BackgroundRobotic rehabilitation is a commonly adopted technique used to restore motor functionality of neurological patients. However, despite promising results were achieved, the effects of human-robot interaction on human motor control and the recovery mechanisms induced with robot assistance can be further investigated even on healthy subjects before translating to clinical practice. In this study, we adopt a standard paradigm for upper-limb rehabilitation (a planar device with assistive control) with linear and challenging curvilinear trajectories to investigate the effect of the assistance in human-robot interaction in healthy people.MethodsTen healthy subjects were instructed to perform a large set of radial and curvilinear movements in two interaction modes: 1) free movement (subjects hold the robot handle with no assistance) and 2) assisted movement (with a force tunnel assistance paradigm). Kinematics and EMGs from representative upper-limb muscles were recorded to extract phasic muscle synergies. The free and assisted interaction modes were compared assessing the level of assistance, error, and muscle synergy comparison between the two interaction modes.ResultsIt was found that in free movement error magnitude is higher than with assistance, proving that task complexity required assistance also on healthy controls. Moreover, curvilinear tasks require more assistance than standard radial paths and error is higher. Interestingly, while assistance improved task performance, we found only a slight modification of phasic synergies when comparing assisted and free movement.ConclusionsWe found that on healthy people, the effect of assistance was significant on task performance, but limited on muscle synergies. The findings of this study can find applications for assessing human-robot interaction and to design training to maximize motor recovery

Feasibility of Muscle Synergy Outcomes in Clinics, Robotics, and Sports: A Systematic Review

In the last years, several studies have been focused on understanding how the central nervous system controls muscles to perform a specific motor task. Although it still remains an open question, muscle synergies have come to be an appealing theory to explain the modular organization of the central nervous system. Even though the neural encoding of muscle synergies remains controversial, a large number of papers demonstrated that muscle synergies are robust across different tested conditions, which are within a day, between days, within a single subject and between subjects that have similar demographic characteristics. Thus, muscle synergy theory has been largely used in several research fields, such as clinics, robotics and sports. The present systematical review aims at providing an overview on the applications of muscle synergy theory in clinics, robotics and sports; in particular, the review is focused on the papers that provide tangible information for: (i) diagnosis or pathology assessment in clinics; (ii) robot-control design in robotics; and (iii) athletes’ performance assessment or training guidelines in sports

Caratteristiche delle sinergie muscolari dell'arto superiore, in soggetti sani e con diagnosi di ictus: revisione della letteratura

Background e obiettivi: L'impairment dell’arto superiore rappresenta, per l’incompletezza del recupero e l’impatto sulla qualità di vita che ne deriva, un aspetto di rilievo nei soggetti con diagnosi di ictus. Tuttavia, l’eterogeneità dei quadri motori ha da sempre rappresentato una difficoltà per lo sviluppo di evidenze della validità ed efficacia delle strategie fisioterapiche, probabilmente per un maggior focus della ricerca sugli effetti della riabilitazione a livello periferico, piuttosto che cercare di comprendere i meccanismi neurofisiologici centrali alla base del controllo motorio. In questo contesto si inserisce quindi il presente disegno di studio che, sostenendo l’ipotesi delle sinergie muscolari quale strategia del Sistema Nervoso Centrale per organizzare il movimento, ha come obiettivo di individuare le caratteristiche dei moduli motori nelle popolazioni con ictus e confrontarli con quelli registrati nei soggetti sani, al fine di individuare le eventuali alterazioni neurofisiologiche che un evento cerebrovascolare determina nell’organizzazione motoria dei movimenti volontari dell’arto superiore. Materiali e metodi: La presente tesi, redatta seguendo le linee guida PRISMA, fa riferimento al protocollo di revisione registrato su PROSPERO il 1 ottobre 2021 (ID: CRD42021275657). In particolare sono state consultate le seguenti banche dati: PubMed, CINAHL, Scopus, Web of Science, Cochrane ed Embase, dalle quali sono stati raccolti da due revisori indipendenti gli articoli che rispettassero i criteri di inclusione definiti a priori. In caso di disaccordo, un terzo revisore è intervenuto per prendere le decisioni finali. Una volta valutata l'inclusione degli studi, sono stati estratti e raccolti i dati in tabelle sinottiche. Risultati: Quarantotto studi sono stati analizzati per l'estrazione dei dati. Per ognuno di questi sono state raccolte le informazioni relative a campione, disegno di studio, definizione di sinergia muscolare, algoritmo di estrazione, numero e composizione dei moduli motori. Discussione e conclusioni: La mancanza di omogeneità rispetto alla definizione dei protocolli sperimentali ha reso i dati raccolti solo parzialmente confrontabili. Studi con caratteristiche affini hanno evidenziato sinergie quantitativamente simili in popolazioni con impairment motorio da lieve a moderato rispetto al gruppo di controllo sano. Risultati contrastanti sono invece emersi nei soggetti con disabilità di grado severo. Composizioni diverse sono state individuate nella maggior parte degli studi, per cui in termini di attivazioni muscolari non è stato possibile descrivere una valida panoramica dei moduli motori nei soggetti sani e con diagnosi di ictus.Background and objectives: Due to difficult in recovery and impact on quality of life, impairment of the upper limb represents the major issue in individuals diagnosed with stroke. However, heterogeneity of motor prognosis has always represented a difficulty for the development of valid and efficient physiotherapy strategies, probably due to a greater focus of research on the effects of rehabilitation at the peripheral level, rather than trying to understand the central neurophysiological mechanisms underlying motor control. This is the context for the present study design which, supporting the hypothesis of muscle synergies as a Central Nervous System strategy to organise movements, aims to identify the characteristics of motor modules in stroke populations and to compare them with those recorded in healthy subjects, in order to identify any neurophysiological alterations that a cerebrovascular event determines in motor control of voluntary movements of the upper limb. Materials and methods: This thesis followed the PRISMA guidelines and refers to the review protocol registered on PROSPERO on 1st October 2021 (ID: CRD42021275657). The following databases were consulted: PubMed, CINAHL, Scopus, Web of Science, Cochrane and Embase. Articles accomplishing defined inclusion criteria were screened by two independent reviewers. A third reviewer solved eventual disagreement. Data from included studies were extracted and collated in synoptic tables. Results: Forty-eight studies were analysed for data extraction. For each of these, information on sample, study design, definition of muscle synergy, extraction algorithm, number and composition of motor modules was extracted. Discussion and conclusions: The lack of homogeneity with respect to the definition of the experimental protocols made the collected data only partially comparable. Studies with similar characteristics showed quantitatively similar synergies in populations with mild to moderate motor impairment, compared with healthy control subjects. Conversely, contrasting results emerged in subjects with severe impairment. Different compositions were found in most of the studies, thus was not possible to describe a valid overview of the motor modules in healthy and stroke-diagnosed subjects at the level of muscle activations

Novel Bidirectional Body - Machine Interface to Control Upper Limb Prosthesis

Objective. The journey of a bionic prosthetic user is characterized by the opportunities and limitations involved in adopting a device (the prosthesis) that should enable activities of daily living (ADL). Within this context, experiencing a bionic hand as a functional (and, possibly, embodied) limb constitutes the premise for mitigating the risk of its abandonment through the continuous use of the device. To achieve such a result, different aspects must be considered for making the artificial limb an effective support for carrying out ADLs. Among them, intuitive and robust control is fundamental to improving amputees’ quality of life using upper limb prostheses. Still, as artificial proprioception is essential to perceive the prosthesis movement without constant visual attention, a good control framework may not be enough to restore practical functionality to the limb. To overcome this, bidirectional communication between the user and the prosthesis has been recently introduced and is a requirement of utmost importance in developing prosthetic hands. Indeed, closing the control loop between the user and a prosthesis by providing artificial sensory feedback is a fundamental step towards the complete restoration of the lost sensory-motor functions. Within my PhD work, I proposed the development of a more controllable and sensitive human-like hand prosthesis, i.e., the Hannes prosthetic hand, to improve its usability and effectiveness. Approach. To achieve the objectives of this thesis work, I developed a modular and scalable software and firmware architecture to control the Hannes prosthetic multi-Degree of Freedom (DoF) system and to fit all users’ needs (hand aperture, wrist rotation, and wrist flexion in different combinations). On top of this, I developed several Pattern Recognition (PR) algorithms to translate electromyographic (EMG) activity into complex movements. However, stability and repeatability were still unmet requirements in multi-DoF upper limb systems; hence, I started by investigating different strategies to produce a more robust control. To do this, EMG signals were collected from trans-radial amputees using an array of up to six sensors placed over the skin. Secondly, I developed a vibrotactile system to implement haptic feedback to restore proprioception and create a bidirectional connection between the user and the prosthesis. Similarly, I implemented an object stiffness detection to restore tactile sensation able to connect the user with the external word. This closed-loop control between EMG and vibration feedback is essential to implementing a Bidirectional Body - Machine Interface to impact amputees’ daily life strongly. For each of these three activities: (i) implementation of robust pattern recognition control algorithms, (ii) restoration of proprioception, and (iii) restoration of the feeling of the grasped object's stiffness, I performed a study where data from healthy subjects and amputees was collected, in order to demonstrate the efficacy and usability of my implementations. In each study, I evaluated both the algorithms and the subjects’ ability to use the prosthesis by means of the F1Score parameter (offline) and the Target Achievement Control test-TAC (online). With this test, I analyzed the error rate, path efficiency, and time efficiency in completing different tasks. Main results. Among the several tested methods for Pattern Recognition, the Non-Linear Logistic Regression (NLR) resulted to be the best algorithm in terms of F1Score (99%, robustness), whereas the minimum number of electrodes needed for its functioning was determined to be 4 in the conducted offline analyses. Further, I demonstrated that its low computational burden allowed its implementation and integration on a microcontroller running at a sampling frequency of 300Hz (efficiency). Finally, the online implementation allowed the subject to simultaneously control the Hannes prosthesis DoFs, in a bioinspired and human-like way. In addition, I performed further tests with the same NLR-based control by endowing it with closed-loop proprioceptive feedback. In this scenario, the results achieved during the TAC test obtained an error rate of 15% and a path efficiency of 60% in experiments where no sources of information were available (no visual and no audio feedback). Such results demonstrated an improvement in the controllability of the system with an impact on user experience. Significance. The obtained results confirmed the hypothesis of improving robustness and efficiency of a prosthetic control thanks to of the implemented closed-loop approach. The bidirectional communication between the user and the prosthesis is capable to restore the loss of sensory functionality, with promising implications on direct translation in the clinical practice