Robotics: Science and Systems IV

fMRI-Compatible Robotic Interfaces with Fluidic Actuation

Ningbo Yu, Christoph Hollnagel, Armin Blickenstorfer, Spyros Kollias, Robert Riener

Abstract: Actuation is a major challenge in the development of robotic systems intended to work in the Magnetic Resonance Imaging (MRI), due to the high magnetic fields and limited space in the scanner. Fluidic actuators can be made MRI-compatible and are, thus, promising solutions. In this work we developed two robotic interface devices, one with hydraulic and another with pneumatic actuation, to control one degree-of-freedom translational movements of a user that performs functional MRI (fMRI) tasks. These two systems differ from conventional fluidic actuators in the special cylinder materials and the long transmission lines that connect the endeffector inside the scanner with the valves and pressure sensors far away. Both systems have been proved to be MRI-compatible and yield no image artifacts in a 3T scanner. Passive as well as active subject movements were achieved by position and impedance controllers. With the hydraulic system we achieved smoother movements, higher position control accuracy and improved robustness against force disturbances than with the pneumatic system. In contrast, the pneumatic system was back-drivable, showed faster dynamics with relatively low pressure, and allowed force control. Furthermore, it is easier to maintain and does not cause hygienic problems after leakages. In general, pneumatic actuation is favorable for fast or force-controlled applications, whereas hydraulic actuation is recommended for applications that require high position accuracy, or slow and smooth movements.



    AUTHOR    = {Ningbo Yu, Christoph Hollnagel, Armin Blickenstorfer, Spyros Kollias, Robert Riener},
    TITLE     = {f{MRI}-Compatible Robotic Interfaces with Fluidic Actuation},
    BOOKTITLE = {Proceedings of Robotics: Science and Systems IV},
    YEAR      = {2008},
    ADDRESS   = {Zurich, Switzerland},
    MONTH     = {June},
    DOI       = {10.15607/RSS.2008.IV.026}