Interface sensor systems for upper limb prosthetics

Abstract

Active prosthetic hands could benefit from tactile feedback at the fingers when performing a variety of daily activities, such as grasping and manipulating objects. This requires real-time monitoring of pressure and shear at the interface between the fingers and objects. Although some pressure sensors are available, little work has been reported on sensor systems capable of simultaneous measurement of pressure and shear, despite the fact that shear monitoring is crucial in detecting object slip and movement. Further to this, control of an upper limb prosthesis relies on surface EMG (electromyography) control. This surface interface is a strong contributor to loss of prosthesis control and movement artefacts. In this thesis, a sensor system has been developed, specifically for upper limb prosthetic applications. This platform tri-axial pressure and shear sensor system (TRIPS) was previously developed in the research team which was designed for a range of body interface applications and successfully validated to be applied at stump/socket interface for lower limb amputees. For potentially applications in upper limb prosthetics, TRIPS sensor system has been further developed based on criteria set out in literatures in the fields of EMG stresses and fingertip kinetics. A sensor accuracy of 10% was considered acceptable for the prototype sensor system and this was validated using calibration equipment and techniques developed in this thesis. Following sensor development, the sensor system was utilised to capture various stresses, typical in an active upper limb prosthesis. This included the EMG electrode-socket interface and the fingertip-object interface. To provide initial data, a socket-simulator was developed, which allowed testing with intact participants prior to recruiting limb-loss patients. The stresses at these interfaces were analysed and potential patterns recognised. This sensor system provides the capability to quantify these stresses and to create active prosthetics which are more reliable and easier to use.

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ORCID for Liudi Jiang: orcid.org/0000-0002-3400-825X

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