A new time-frequency approach to estimate single joint upper limb impedance.

This paper proposes a new technique to estimate single joint impedance during postural tasks. The method is based on a reassigned spectrogram and can track the frequency modulation of biomechanical system after perturbations. Compared to the existing techniques, this procedure successfully estimated rapidly time varying impedance parameters in a faster and equally accurate way. For this reason it can be an optimum tool to easily estimate limb impedance of stroke patients, before, during, and after robot therapy sessions, without interfering with the delivered treatment.