Preliminary design of a novel system for estimating end-point stiffness

Quantification of arm stiffness is of great interest for a wide group of different research branches, because modulation of muscular stiffness represents the principal mechanism of motor control of movements. Past literature concentrated efforts in defining different methods to identify multijoint hand stiffness, but the required computational burden make them hard to implement. In the present work we aim to propose a novel design of a single degree of freedom mechanism conceived to estimate arm stiffness in a reduced amount of time; a rotary mechanism coupled to a commercial six axes force sensor allows to apply known cyclic radial perturbation to the human arm and acquiring the restoring forces. The outcomes have reported that the device is reliable and stiffness measurements on a test bench can be performed in a reduced amount of time (about 1 second). A modular system has been also developed to conduct experiment on humans while performing motor adaptation.