Digital Theses Archive


Tesi etd-03222023-095412

Type of thesis
The Myokinetic Interface: magnetic tracking and actuation for the restoration of dexterous control and proprioceptive feedback in transradial amputees
Scientific disciplinary sector
Istituto di Biorobotica - PHD IN BIOROBOTICA
Membro Prof.ssa CASADIO, MAURA
Membro Dott. D'ALONZO, MARCO
  • Upper limb prosthetics
  • Myokinetic Interface
  • Human-Machine Interfaces
  • Magnetic Tracking
  • Magnetic Actuation
  • Magnetic Field Modeling
Exam session start date
Developing dexterous hand prostheses which are controlled and perceived naturally by an<br>amputee is one of the major challenges in biomedical engineering. With this goal in mind,<br>many research efforts have been made, from proposing novel surgical techniques, to advancing<br>technologies for biological signals acquisitions and neuromuscular stimulation. Most of the<br>state-of-the-art approaches probe muscle electrical activity for control, and deliver electrical<br>pulses to nerves for sensory feedback. An alternative approach based on the implantation of<br>permanent magnets, dubbed the myokinetic interface, aims to monitor muscles contractions<br>by localizing the magnetic markers implanted in them, and thus controlling the corresponding<br>movements in the artificial hand. In this way, such an interface holds the potential for a<br>biomimetic, direct, independent, and parallel control of multiple degrees of freedom of an<br>artificial hand. Moreover, selectively vibrating the magnets also offers a unique opportunity to<br>study kinesthetic percepts in humans, thus possibly becoming a bidirectional interface. The<br>myokinetic interface could be combined with existing advanced human-machine interfaces<br>for prosthetics, such as targeted muscle reinnervation or osseointegrated implants, to further<br>improve its efficacy and comfort, and also opens new possibilities to interface humans with<br>robotic technologies in an intuitive way.<br>After presenting the latest advances in human-machine interfaces for prosthetics and the<br>key enabling technologies to develop a myokinetic interface (Chapter 1), this thesis reports<br>about part of the development stages of the latter, along three distinct topics: (i) modelling of<br>the implanted magnets (Part I, Chapter 2), (ii) magnetic tracking (Part II, Chapter 3) and (iii)<br>magnetic actuation (Part III, Chapter 4 and Chapter 5). Chapter 2 provides exact and robust<br>expressions for field and field gradient for permanent magnets cylinders with generic uniform<br>magnetization. In addition, expressions regulating the magnetic interaction between coaxial<br>cylinders are presented. Chapter 3 treats an in-silico study aimed at quantifying the impact of<br>sensors properties in the accuracy, precision and number of iterations of a magnetic tracker.<br>Different number of magnets and their distances from the sensors plane are considered in<br>order to evaluate the performance of the tracking algorithm for various sensors resolution<br>and localization rates (frequencies of localization). Chapter 4 addresses in-vitro and in-vivo<br>investigations of the magnetic actuation approach to deliver kinesthetic percepts. A coil-array<br>system consisting of 8 stationary electromagnets is used to test directionality, frequency<br>selectivity and the tuning of the vibration shape in a single remote magnet. Simplified systems<br>with only one degree of freedom (using a single magnetic actuating source) are used to vibrate<br>a magnet implanted in the forearm of an animal model. Chapter 5 presents the integration of<br>magnetic tracking and actuation in a single device consisting of 12 coils capable to selectively<br>vibrate moving magnets. Such a system exhibits individual actuation of a single magnet out of<br>4 that are still, or out of 2 that are moving, while simultaneously tracking all of them. Finally,<br>Chapter 6 discusses the thesis work including limitations, outlooks and concluding remarks.