Design criteria for a mechatronic handle for measuring visco-elastic properties of the human arm

The experimental investigation of the visco-elastic properties of the human arm has important implications in neuroscience, robotics and neuro-rehabilitation of the upper limb. In neuroscience it allows studying the mechanisms used by the central nervous system in implementing low-level strategies for motion control; in robotics it can provide useful information for the formulation of control strategies for human-robot interaction, by taking inspiration from the biological behavior; in neuro-rehabilitation it may be a useful tool for quantitatively assessing the recovery of motor functions during motor therapy. Few mechatronic instruments exist allowing the direct measurement of visco-elastic properties of the human arm. None of them are intended to be portable and stand-alone devices, and also to be properly interfaced with existing robots as end effectors. This paper is concerned with the design of a novel mechatronic handle intended to be a portable device for the measurement of human arm visco-elastic properties. The design specifications take into account also the possibility of adapting the device to existing robots for rehabilitation motor therapy. In particular, the investigation of existing literature, both in robotics and in neuroscience, together with numerical simulations, led to the selection of the most useful technical specifications for such devices. A preliminary design of the handle is also presented and discussed.